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REVIEW OF LITERATURE
Biological control may be defined as ‘A reduction of pathogens through the action
of other living organisms which occur naturally or through the manipulation of the
environment’. The term was introduced in scientific literature by G.F. Von Tabuef in 1914
(Baker, 1987). Interest in biological control first observed in 1920s and 1930s, when some
plant pathogens were suppressed by microbes producing some antibiotics. A turning point
for research on biological control of plant pathogens came after a gap of more than 30 years
when in 1963, an International Symposium, on ‘Ecology of soil-borne plant pathogens
prelude to biological control’ was held in Berkeley, USA.
Before attaining the true management of soil microbes, it is essential to understand
better the interaction between plants and microbes in the soil around the roots. Management
of soil-microbes is necessary to optimize N and P nutrition of plants. There are extensive
microbial activities in rhizosphere soil which is colonized by a wide range of microbes with
important effects on plant nutrition, growth and health. Among these micro-organisms the
importance of mycorrhiza deserve special attention.
Mycorrhizal fungi have been involved in the adaptation of plants to unfavourable
conditions from the very beginning (Penninsi, 2004). The most prominent effect of this
group of fungi is improved phosphorus nutrition of the host plant in soil (Koide, 1991).
However uptake of nitrogen, zinc, copper and other micro-nutrients enhanced as well. The
ability of AM fungi to suppress root diseases caused by soil borne pathogens have been
intensively studied in the last thirty years. Numerous reviews on the efficacy of AM fungi
as biological control agents have been published by Schenk and Kellam, (1978);
Schoenbeck, (1979); and Siddiqui and Mahmood, (1995).
The main objective of this review is to analyze the role of bioinoculants on
biological control of plant diseases caused by plant-parasitic nematodes especially by root-
knot nematode M. incognita. However, the informations regarding the interaction of these
organisms with nematodes are meager and lacking in Indian context. It is therefore need to
describe the research findings by various workers.
Distribution, Identification and Classification of AM fungi
Mycorrhizal fungi are a major component of agricultural natural resources and
members of kingdom fungi. The term ‘mycorrhiza’ is derived from Greek word which
means ‘fungus root’ (Friberg, 2001). The term was first coined by A.B Frank a German
plant pathologist in 1855 to describe the symbiotic relationship between plant roots and
fungi. AM associations have been observed in 1000 genera of plants belonging to 200
families. There are about 300,000 receptive hosts in world flora (Kendrick and Berch,
1985). Over 90% of plant species are associated with mycorrhizal fungi of vascular and
non-vascular in nature. Some important crops such as carrot, maize, soybean, citrus fruits,
tomatoes and pepper harbouring the population of AM fungi (Muchovej, 2004).
The abundance and distribution of AM fungi have been studied by many workers
(Anderson et al., 1984; Hussain et al., 1995). AM fungi are reported to be found in diverse
land areas such as calcareous grasslands, arid/semi-arid grasslands, several temperate
forests, tropical rainforests and shrubs lands in diverse part of the world (Muthukumar and
Udaiyan, 2002; Renker et al., 2005). Reyes and Ferrera (1992) observed that AM
colonization levels are higher in herbs than in shrubs. They have also been reported in
floating (Bagyaraj et al., 1979) and submerged aquatic plants (Clayton and Bagyaraj, 1984).
They are found in Gymnosperms (Harley, 1969), Pteridophytes (Cooper, 1976) and
Bryophytes (Smith and Read, 1997). Recently AM fungi have received more attention
especially in African countries such as Namibia, Morocco, Nigeria, Zambia and South
Africa.
According to Mosse and Bowen (1968), AM population is more in cultivated soil as
compared to virgin soil. AM fungi are mostly found in top 15-30 cm of soil and their
number decreases markedly below the top 15 cm of soil (Redhead, 1977). Moisture content
had negative influence on AM development. Significant correlation between AM fungi, soil
pH, moisture and P content has been observed by Rani and Manoharachary, (1994); and
Bharadwaj et al., (1997).
The pattern of distribution is also very important phenomena in the land growing
crops. Using relative simple technique of wet sieving and decanting (Gerdemann and
Nicolson, 1963), spores have been isolated from soils. The available reports indicate that
there is a more or less uniform distribution of all the genera in both the hemispheres.
Mycorrhiza are classified on the basis of morphological characteristics, biochemical
and molecular properties of soil-borne resting spores (Morton and Benny, 1990; Mukerji et
al., 2002; Peterson et al., 2004). Arbuscular mycorrhiza were formerly classified in the
phylum zygomycota under the family Endogonaceae, but this was later re-evaluated when
AM fungi produced asexual spores rather than sexual spores like other endogone species
(Pawlowska and Taylor, 2004). Seven different types of mycorrhizal associations have been
recognized, viz., Ecto-and Endo mycorrhiza, Ericoid mycorrhiza, orchidaceous mycorrhiza,
Arbutoid mycorrhiza, Monotropoid mycorrhiza and Ectendo mycorrhiza (Smith and Read,
2008). Among these groups, endo-mycorrhiza represent a group of fungi which are
geographically ubiquitous and occur over a wide ecological range.
On the basis of the advance techniques, the latest classification of AM fungi
belonging to the class Glomeromycetes of the phylum Glomeromycota (Schubler et al.,
2001; Walker et al., 2007) and the genus Glomus is said to be the largest within the
glomales. AM fungi played diverge role in the Indian Agricultural System for various ways.
Role of AM fungi in nutrient uptake
AM fungi involved in the symbiotic activities with the roots of different plants.
Interests in AM fungal symbiosis observed in agriculture, forestry, rehabilitation and in
environments (Cuenca et al., 1998; Friberg, 2001). The major benefits of AM fungi include
enhanced nutrient uptake, increased tolerance to root pathogens, drought resistance,
tolerance to toxic heavy metals and improved soil aggregation and structure. The main
hurdle in exploiting beneficial effects of AM fungi for improved agricultural productivity is
the obligate nature of the symbiont. They can not be grown and cultured in the absence of
their host plants. The greatest impediment to AMF commercialization is the obligate
biotrophicity of the fungi, which necessitates the use of a living host for sustained survival
and propagation. The cost of inoculum production can be relatively high as compared to
other organisms. Furthermore, the lack of consistency in efficaceous product and poor
market demands has contributed to the insignificant and slow progress in this area.
AM fungi have been reported to function as biofertilizers, biostimulators,
bioprotectors etc. and therefore can benefit the area of agriculture, horticulture and
sylviculture immensely (Kendrick and Berch, 1985). AM fungi received wide attention as
part of an increasing popular paradigm that considers as an active and diverse soil biological
community as essential for increasing the sustainability of agriculture system (Gianinazzi
and Schuepp, 1994). It has been established that AM fungi have the ability to sequester
mineral nutrients and transfer to the plant roots when nutrients are in high concentration in
the soil. Macro-and micronutrients are required by the plants in varying amounts.
In the majority of mycorrhizal type improvements in plant growth followed by root
colonization by AM fungi occur as a result of acquisition of the mineral nutrient (especially
P) from the soil (George, 2000). AM fungi are known to enhance uptake of the
macronutrients like phosphorus from the soil. AM fungi help the plants in two ways: firstly
they help in the uptake of these elements which are considered to be relatively immobile
and secondly they take up these elements and store them so as to prevent their
concentrations to reach toxic levels (Gonzalez-Chavez et al., 2002; Pawlowska and Charvat,
2004).
Phosphorus deficiency is one of the most widespread mineral nutrient stresses
limiting crop production in the world (Sanchez and Salinas, 1981; Holford, 1997).
Phosphorus is the essential nutrient required for the plant growth and is found in many soils
in organic and complex inorganic forms. Due to its slow solubility and mobility, plants can
not readily utilize P in an organic or complex inorganic form (Schachtman et al., 1998).
Inorganic phosphate present in soluble forms in the soil can be readily utilized by plants but
in limited amounts. The enzyme phosphatase produced by AM fungal extraradical hyphae
hydrolyses and releases P from organic complexes and facilitates the absorption of P and
other nutrients thereby creating a depletion zone around the roots (Li et al., 1991; Jackobson
et al., 1992). These depletion zones give mycorrhizal plants a great advantage because of
the ability of ERH to extend past this nutrient depletion zone to enhance absorption (Sylvia
et al., 2001). Thus AM fungi intervene to enhance nutrient uptake through the spread of
extraradical hyphae into the surrounding soil and hydrolyzing an unavailable sources of P
with the aid of secreted enzymes such as phosphatase (Koide and Kabir, 2000).
Enhancement of phosphorus uptake by AM fungi and transfer to the host plant has been
reported by several workers (Karandashov and Bucher, 2005; Cardoso et al., 2006).
Sylvia et al. (2001) evaluated the influence of arbuscular mycorrhizal fungi and
concluded that the role of mycorrhiza in plant competition for nutrients is markedly
impacted by soil nutrient status and reduced P application in tomato plants.
Mamtha and Bagyaraj (2002) studied the effect of different levels of VAM
application on growth and nutrition of tomato under greenhouse conditions. The different
levels of Glomus fasciculatum improved the plant growth, biomass, P content and
mycorrhizal root colonization. Chaoxing et al. (2006) studied the effects of different AM
fungi strains on tomato growth and nutrient absorption during seedling stage. They found
inoculated plants produced higher dry matter and showed higher nutrient uptake than
uninoculated ones. Glomus mosseae strains showed higher infection rate than the others.
Role of AM fungi in nematode control
Plant-parasitic nematodes are among the most widespread and important pathogens
causing crop losses across the world. Plant-parasitic nematodes and mycorrhizal fungi are
commonly found inhabiting the same niche and colonizing roots of their host plants. These
two groups of micro-organisms exert a characteristic but opposite effects on plant health.
The potential role of mycorrhizal fungi for the control of nematode diseases has received
considerable attentions (Osman et al., 1990; Santhi and Sundarbabu, 1995; Price et al.,
1995). AM fungi have shown an antagonistic influence on the population of plant-parasitic
nematodes (Bagyaraj et al., 1979; Sivaprasad et al., 1990; Osman et al., 2005).
Jain and Hasan (1986) reported that nematodes did not affect VAM sporulation
adversely when there was 50 percent root colonization. The nematodes number was lower
and rarely infect VAM colonized region of the roots. Increased spore production and higher
root colonization by VAM fungi in the presence of nematodes have also been observed by
Ingham, (1988). Nematode susceptible plants colonized by AM fungi were better able to
tolerate plant-pathogenic nematodes (Kellam and Schenck, 1980; Sankaranaryanan and
Sundarababu, 1994).
Sikora (1978) suggested that attractiveness of the root system to M. incognita larvae
was altered by the presence of G. mosseae. As a result of interaction in general, the severity
of nematode diseases was reduced in mycorrhizal plants. The antagonistic effects of AM
fungi on nematodes may be either physical or physiological in nature. Sitaramaiah and
Sikora (1980) observed that Glomus mosseae increased the resistance of tomato plants to
Rotylenchulus reniformis infection. AM fungi can alter the physiology of the roots
including root exudates which were responsible for chemotactic attraction of nematodes.
Sitaramaiah and Sikora (1982) expressed the other version of increasing resistance
in tomato plants colonized by Glomus fasciculatum against Rotylenchulus reniformis by
delaying the nematode attacks in roots. Glomus fasciculatum adversely affect the R.
reniformis during several phases of its life cycle.
Jain and Sethi (1989) showed that the occurrence of Heterodera cajani and VAM
fungi, Glomus fasciculatum and G. epigaeus in Vigna unguiculata were largely independent
of each other and the organisms modify the effect of each other to some extent. The
presence of G. fasciculatum showed a adverse effects on cyst production and multiplication
of nematodes while G. epigaeus exhibited a different trends.
Heald et al. (1989) have suggested increased nutrient uptake by mycorrhizal fungi
enhances plant tolerance relative to detrimental effects on nematodes. Similarly it had been
found that the presence of mycorrhiza increased the tolerance of plants to diseases (Chandra
and Kehri, 1996). Sivaprasad et al. (1990) observed that the pre-inoculation of Piper nigrum
cv. Panniyur cuttings with Glomus fasciculatum or G. etunicatum reduced the root-knot by
32.4 and 36.0 per cent respectively and reduced nematode population in roots and
surrounding soils, which significantly increased growth even in the presence of nematodes.
The tolerance of Kiwi plants to M. javanica was increased in presence of G. etunicatum
(Verdejo et al., 1990).
In the similar study, Singh et al. (1990) observed that preinoculation of tomato cv.
Pusa Ruby roots with Glomus fasciculatum resulted in an increase in lignin and phenols and
this might be improved the resistance in tomato plants against root-knot nematode,
Meloidogyne incognita.
Mishra (1996) studied the interrelationship of M. incognita, G. fasciculatum and the
three commonly used herbicides. Higher levels of VAM after 60 days of inoculation
improved growth of tomato plants while simultaneous inoculation of VAM and nematodes
resulted maximum colonization of VAM. Pre-establishment of G. fasciculatum increased
plant growth, decreased the size and number of galls and improved NPK uptake compared
to those plants inoculated with the nematode alone or pre-inoculated with the nematodes to
VAM. Sundarababu et al. (1996) observed that when Glomus fasciculatum was inoculated
15 days prior to nematode inoculation that resulted an enhancing the growth of tomato cv.
CO3 and suppress M. incognita multiplication. Simultaneous inoculation however followed
the similar pattern. G. fasciculatum was unable to suppress nematode growth when the
nematode was inoculated 15 days prior to fungus. Mishra and Shukla (1997) reported that
simultaneous inoculation of G. fasciculatum with M. incognita caused greater reduction in
the number and size of the root-galls induced by nematodes.
Cofcewicz et al. (2001) studied the interaction of arbuscular mycorrhizal fungi
Glomus etunicatum and Gigaspora margarita with root-knot nematode Meloidogyne
javanica and their effects on the growth and mineral nutrition of tomato. They pointed out
that the shoot dry matter and yields were reduced by nematode infection and this was less
pronounced in plants colonized with G. etunicatum than those plant colonized with G.
margarita and non-mycorrhizal plants. The higher tolerance of plants colonized with G.
etunicatum to M. javanica appeared to be associated with P nutrition. Similarly, Labeena et
al. (2002) evaluated the ability of five arbuscular mycorrhiza, viz. G. fasciculatum, G.
macrocarpum, G. margarita, Acaulospora laevis and Sclerocystic dussi to mitigate the
damage caused by M. incognita on tomato cv. Pusa Ruby. They found that G. fasciculatum
was the most efficient in promoting plant growth despite in the presence of nematodes. The
developmental stages of nematode in the roots and density in soil were suppressed by the
AM fungi and the most pronounced effect was exhibited by G. fasciculatum.
Osman et al. (2005) observed the interaction of root-knot nematode and VAM fungi
on common bean plants (Phaseolus vulgaris L.) in the greenhouse. They concluded that the
inoculation with VAM fungus caused a significant increase in plant height and fresh weight
as compared to un-treated plants. The inoculation with VAM fungus caused a significant
increase in phosphorus content. Although there were significant decrease in nematode final
population and gall-index when plants inoculated with nematodes at 15 and 30 day after
mycorrhizal infection.
Castillo et al. (2006) studied the effect of single and combined inoculations of olive
planting stocks cvs. Arbequina and Picual with the arbuscular mycorrhizal fungi Glomus
intraradices, Glomus mosseae or Glomus viscosum and the root-knot nematodes M.
incognita and M. javanica on plant performance and nematode infection. They observed
that prior inoculation of olive plants with AM fungus improved the health status and vigour
of Arbequina and Picual planting stocks during nursery propagation. Indigenous isolates of
AM fungus Glomus fasciculatum were found effective in the management of root-knot
nematode Meloidogyne incognita on tomato (Kantharaju et al., 2005). Shreenivasa et al.
(2007) found that presence of AM fungus (Glomus fasciculatum) reduced penetration of
Meloidogyne incognita larvae in tomato roots. Neog et al. (2007) studied different spore
inoculum levels and time of inoculations of VAM fungus Glomus fasciculatum, and noticed
that inoculation of VAM with two levels, viz., 150 and 300 spores level prior to nematode
inoculation was more effective in reducing number of galls, egg-masses and final nematode
population in soil and increasing plant-growth parameters as compared to simultaneous
inoculation of both VAM and nematode or inoculation of nematode 10 days prior to
inoculation of VAM and the highest reduction was recorded when 300 spores were added 1
days prior to inoculation of nematodes.
AM fungi have the ability to induce systemic resistance against plant- parasitic
nematodes in a root system (Elsen et al., 2008). Anjos et al. (2010) demonstrated that the
establishment of an AM fungus before nematode infection effectively reduced reproduction
of the root-knot nematode Meloidogyne incognita and reduced disease severity in infested
soil seems to be due to physiological alteration in favour of growth of AM fungus.
Aparajita et al. (2009) studied the effect of soil types on efficacy of Glomus
fasciculatum in the management of Meloidogyne incognita on green gram. Nematode
reproduction was found to be minimum in sandy loam soil as compared to other types of
soil when VAM was inoculated simultaneously with nematodes. The plant growth was
found increased when soil was supplemented with VAM fungus. VAM spore population in
soil and mycorrhizal colonization in roots were found higher in coarse textured soil as
compared to clay soil.
Pandey (2011) tested two species of VAM fungi, viz. Glomus mosseae and Glomus
fasciculatum against Heterodera cajani population infecting cowpea. In the first set of
experiment, mixed inoculation of VAM was found more effective in managing H. cajani
population whereas single VAM inoculation Glomus fasciculatum proved to be more
beneficial. In second set of experiment degree of mitigative effects of VAM on Heterodera
cajani depended at the time of VAM and nematodes inoculation. Two weeks prior
inoculation of G. fasciculatum resulted greater reduction in nematode multiplication.
Alguacil et al. (2011) found whether galls produced by M. incognita infection in
Prunus persica roots were colonized by AM fungi or not. Their study finally indicated that
the galls produced in P. persica roots due to infection with M. incognita were found
colonized extensively by a community of AM fungus. They hypothesized that they act as
protection agents against opportunistic pathogens.
Role of Azotobacter in improvement of plant growth and disease development
Azotobacter belongs to family Azotobacteriaceae, aerobic, free living bacteria in
nature. The first representative of the genus, A. chroococcum was discovered and described
in 1901 by the Dutch microbiologist and botanist Martinois Beijerinck. Azotobacter are
gram negative bacteria and found in neutral and alkaline soil (Martyniuk and Martyniuk,
2003), in water (Tejera, 2005) and in association with some plants (Kumar et al., 2007).
The isolated culture of Azotobacter fixes about 10 mg Nitrogen-1 carbon source under in
vitro conditions. They are known to synthesize biological active growth promoting
substances such as Vitamins of B group, IAA and gibberellins. The occurrence of this
organism has been reported from the rhizosphere of a number of crop plants such as rice,
maize, sugarcane, bajra, vegetables and plantation crops (Arun, 2007). Azotobacter
normally fix molecular nitrogen from the atmosphere without symbiotic relationship with
plants, although some species are associated with plants (Kass, 1971).
The incorporation of such kind of biofertilizers play major role in improving soil
fertility, yield attributing characters and thereby final yield have been reported by many
workers (Kachroo and Razdan, 2006; Son et al., 2007). In addition to their application in
soil which minimizes the sole use of chemical fertilizers (Subashini et al., 2007) and save
much money to be spent on such fertilizers. Very little informations are available regarding
the research of Azotobacter and its incorporation in the soil for the exploitations of
beneficial capabilities in the agricultural system.
Jackson et al. (1964) found accelerated growth of tomato stem with inoculation of
Azotobacter. Mishutin (1966) demonstrated that bacterial fertilizers significantly improved
the yield of a wide range of crop plants, specially vegetables. Dumal (1992) reported the
effects of Azotobacter on germination, growth and yield of some vegetables. Martinez et al.
(1993) reported that inoculation of Azotobacter increased tomato seed germination by 33-
46 per cent. Similarly, Gerardo Rosales (2002) reported that soil inoculation with
Azotobacter increased tomato seed germination by 33-46 per cent. Azotobacter
chroococcum have the capability for contributing nitrogen to a number of non-legumes by
trapping the nitrogen from aerial nitrogen reservoir (Singh and Sinsinwar, 2006) and can
meet upto 15-20 kg N per ha requirement of crop besides producing some growth
promoting substances that help in increasing the yield (Das et al., 2006).Various research
workers used Azotobacter chroococcum as a bioinoculants in different crops such as wheat
(Kumar et al., 2001), and herbal crops like Withania somnifera (Kumar et al., 2009) for
requirement of nutrient supply.
Effect of interaction of Azotobacter with other bioinoculants
The interaction between rhizospheric microbes and plants have a great influence on
plant health and soil quality (Lynch, 1990). Among these beneficial rhizospheric microbes,
arbuscular mycorrhizal fungi and plant growth promoting rhizobcteria can be considered
and emphasized in recent years in Indian Agricultural System. Since they inhabited the
common habitats, i.e. the root surface and common functions. They have to interact during
their processes of root colonization as root associated microorganisms. Soil
microorganisms, particularly PGPR, can influence spore formation of AM fungi and
functions. While on the other hand the mycorrhiza can also affect PGPR populations on the
rhizosphere population (Barea, 2000).
Bioinoculants like Azotobacter and others have shown synergistic effect on plant
growth parameters and nutrient uptake of different crops. Seed inoculation with a
combinations of beneficial microorganisms including rhizobia, PGPR and PSB have been
shown to increase crop growth and productivity (Zaidi et al., 2003; Rudresh et al., 2005).
Bagyaraj and Menge (1978) studied the interaction between free living N2-fixing
bacterium Azotobacter chroococcum and mycorrhizal fungus Glomus fasciculatum and
found a synergistic effect on plant growth of tomato. Mycorrhizal infection increased the
population of A. chroococcum in rhizosphere and consequently A. chroococcum enhanced
spore production by the mycorrhizal fungus. Javaid et al. (2000) noticed the response of
crop growth when Vigna radiata (L.) Wilczek was grown in farmyard manure and Trifolium
green amended soils with different isolates of VAM fungus and found a positive results in
both the types of soils. El-Zeiny et al. (2001) observed that inoculation of tomato seedling
with Azotobacter, Azospirillum and Bacillus increased plant height, leaf number per plant,
fruit mean weight and yield as compared to untreated control. Suresh and Bagyaraj (2002)
reported synergistic interaction between AM fungi and asymbiotic N2-fixing bacteria such
as Azotobacter chroococcum, Azospirillum spp. and Acetobacter diazotrophicus.
Synergistic effects of combined inoculations of PGPRs have also been reported in various
crops like potato (Kundu and Gaur, 1980), rice (Tiwari et al., 1989) and sugarbeet and
barley (Cakmakci et al., 1999). Similarly, the synergistic effect of AM fungi and
rhizobacteria such as Azospirillum, Azotobacter, Pseudomonas and Phosphate-solubilizing
bacteria were studied by many workers (Bagyaraj, 1990; Siddiqui, 2003).
Similarly Widada et al. (2003) conducted an experiment to evaluate the interaction
effects of AM fungi or/and rhizobacteria, Phosphate-solubilizing bacteria, (PSB), N2-fixing
bacteria (NFB) and Siderophore producing bacteria (SPB) on the growth and nutrient
uptake of sorghum (Sorghum bicolor). Dual inoculation of AM fungi and rhizobacterium
yielded higher plant dry weight and nutrients uptake compared to the individual
inoculation. The rhizobacteria also increased to help the plant colonization by AM fungi.
These results revealed that the interaction of AM fungi and the selected rhizobacteria has a
potentiality to be developed as biofertilizers.
Bhowmik and Singh (2004) evaluated the efficiency of PGPR like Azospirillum sp.,
Azotobacter chroococcum, Pseudomonas fluorescens, Pseudomonas striata and yeast for
maximization effects of Glomus mosseae in Chloris gayana Kunth. Results revealed that
PGPR considerably enhanced mycorrhizal colonization when compared to yeast. They not
only stimulated AM development but also accelerated the root growth possibly to increase
the surface area for colonization. Similarly, Bashan et al. (2004) reported that inoculation of
Azospirillum significantly increased the plant biomass, nutrient uptake, N content, plant
height, leaf size and root length of cereals. Significant increase in plant height, leaf area was
also observed in different crops when jointly inoculated with Pseudomonas, Azospirillum
and Azotobacter strains (Shaukat et al., 2006b).
Wu et al. (2005) conducted greenhouse experiment to evaluate the effects of four
biofertilizers containing Glomus mosseae or Glomus intraradices with or without N-fixer
(Azotobacter chroococcum), Bacillus megaterium and Bacillus mucilaginous on soil
properties and the various growth parameters of Zea mays. Their applications significantly
increased the growth of Z. mays. The use of biofertilizers resulted in the highest biomass
and seedling height. Similarly, Sharma et al. (2005) studied the efficacy of native
bioinoculants, viz. AM fungi and Azotobacter separately as well as in combination for
enhancing biomass productivity of Morus alba, Populus deltoids, Psidium guajava and
Leucaena leucocephala under different agroforestry model alongwith other plant species.
Shaukat et al. (2006a) concluded that Azospirillum, Pseudomonas and Azotobacter strains
could affect seed germination and seedling growth. Ram Rao et al. (2007) studied the
influence of VAM fungi and bacterial biofertilizer (BBF) with 50% recommended dose of
(N and P) of chemical fertilizers on leafy quality traits of mulberry. The dual inoculation of
BBF and VAM (505 cut in N and P) proved economical and beneficial with regard to
saving of 50% cost of chemical fertilizers and improvement in soil fertility and leaf quality.
Similarly, Khan and Zaidi (2007) studied the synergistic effects of plant-growth promoting
rhizobacteria and an arbuscular mycorrhizal fungus (Glomus fasciculatum) on plant growth,
yield and nutrient uptake of wheat plants under field condition. The triple inoculation of
Azotobacter chroococcum with Bacillus and Glomus fasciculatum significantly increased
the dry matter by 2.6-fold as compared to the untreated control. The higher N content (33.6
mg/plant) and P content (67.8 in wheat plants) were observed with the co-inoculation of A.
chroococcum with Bacillus sp. and G. fasciculatum.The findings showed that the multiple
inoculations consistently increased the growth and yield, N and P concentrations in plants
and quality of wheat grains.
Paroha et al. (2009) further studied the integrated effects of biofertilizers (AM fungi,
Azotobacter and PSB) and NPK fertilizers in various combinations on growth and nutrient
acquisition by Tectona grandis. It was observed that integrated application of biofertilizers
and chemical fertilizers enhanced growth responses due to higher uptake of P, N, Cu, Mn
and Zn in the crops. Rabie and Humiany (2004) worked on similar pattern and revealed
that efficiency of biofertilizers can be increased using mixtures of biopreparations as
nitrogen fixers, phosphate and silicate solubilizers as well as mycorrhizal fungi.
Sakthivel et al. (2009) noted the effect of seed inoculation with PGPR on yields of
tomato. Their results favoured the above findings and reported that the higher fruit yield
was found increased in the combinations of Pseudomonas fluorescens + Azotobacter
chroococcum + Azospirillum brasilence. Ratageri and Lakshman (2009) studied the effects
of Glomus macrocarpum, Glomus fasciculatum and Azotobacter spp. on wheat (Triticum
aestivum L.) in sterilized soil. These results clearly demonstrated that the AM fungal
species with Azotobacter used in combinations were found more beneficial for much
improved growth of wheat. Similarly the seed treatments with Azotobacter enhanced seed
germination, plant height and plant biomass of wheat as compared to control (Kumar and
Gupta 2010). Sridevi and Ramakrishnan (2010) scrutinized the effects of AM fungi and
Azospirillum in single as well as dual inoculation on onion (Allium cepa L.). The two
beneficial microbes played a vital role in supplying N and P to the onion and found
enhanced growth and yield over the untreated control.
Ordookhani et al. (2010) studied the impact of inoculating the roots of tomato
(Lycopersicon esculentum) F1 hybrid GS-15 roots with PGPR and AM fungi on fruit
quality. It was found that the application of Pseudomonas + Azotobacter + Azospirillum +
AM fungi significantly increased the lycopene, antioxidant activity and potassium contents
of tomato.
Saba and Khan (2010) investigated the effect of biofertilizers (G. fasciculatum, A.
brasilense, A. chroococcum and Microphos) and pesticides in balsam. The results revealed
that individual application of biofertilizers significantly improved the plant growth
parameters such as length, dry weight and number of flowers as compared to uninoculated
plants. Arumugam et al. (2010) studied the individual and combined inoculation effects of
Rhizobium and Arbuscular mycorrhizal fungi on growth and chlorophyll content of Vigna
unguiculata L. A significant increase was observed in root and shoot length, dry weights of
root and shoot, total number of nodules, dry weight of nodules, percentage of mycorrhizal
infection and total chlorophyll content in the inoculated plants.
Rokhzadi and Toashis (2011) carried out an experiment to evaluate the effects of
single and combined inoculations with plant-promoting rhizobacteria, viz. Azospirillum,
Azotobacter, Mesorhizobium and Pseudomonas on nutrient uptake, growth and yield of
chickpea plants under field conditions. All inoculants were found superior over
uninoculated control with respect to nitrogen concentration in shoot.The treatments
containing Azospirillum + Azotobacter significantly improved phosphorus concentration in
shoots as well grain yield, biomass and, dry weight. Nitrogen and phosphorus uptake of
grains improved by applying every inoculation treatment.
Solanki et al. (2011) studied the yield and nutrient uptake by using dual inoculation
with AM fungi (Glomus fasciculatum) and Azotobacter chroococcum on Chlorophytum
bravllianum. Results showed that the nitrogen uptake was increased in Azotobacter treated
plants, while higher P and K uptake were sustained in AM fungi inoculated plants.
Economic analysis revealed the net profit was highest in NPK + Azotobacter + G.
fasciculatum using dual inoculations of micro-organisms.
Ordookhani and Zare et al. (2011) further investigated the effects of inoculation of
two cultivars of tomato (Lycopersicon esculentum) roots with PGPR and AM fungi on
growth and some element contents. The inoculations with Pseudomonas putida,
Azotobacter chroococcum and Glomus mosseae showed positive results. Azotobacter
chroococcum was more effective than Pseudomonas putida to increase all traits.
Colonization of plant roots by mycorrhiza were significantly higher than non-mycorrhizal
plants, thus increased the overall plant growth.
Effects of Azotobacter and N-fertilizers
The synergistic effect of biofertilizer like Azotobacter and N-fertilizers was well
documented in literature. The favourable effect of Azotobacter and mineral nitrogen
fertilizer on growth, chemical composition of leaves and yield was reported by Stajner et al.
(1997) on sugarbeet, Bambal et al. (1998) on cauliflower, Wyszkowska (1999) on faba bean
and Sharma (2002) on cabbage, Prabhjeet et al. (1994) on Brassica napus, Verma et al.
(1997) on cabbage, Verma et al. (2000) on pea and Panwar et al. (2000) on radish which
revealed that seed yields were found increased with their combined inoculations.
Agrawal et al. (2004) studied the effect of Azotobacter inoculation with graded doses
of nitrogen on the uptake of nutrients and yield of wheat. It was concluded that inoculation
of Azotobacter could save about 20 kg nitrogen in wheat crop. In the similar way, El-
Assiouty and Sedera (2005) carried out an experiment to study the effect of Azotobacter
chroococcum and Phosphorein singly and in combinations with different rates of N and P
chemical fertilizers on growth, yield and quality of spinach cv. Dokki. Results showed that
seed inoculations with biofertilizers (Azotobacter and Phosphorein) enriched the
rhizosphere with such micro-organisms as compared to uninoculated control. Application of
40 kg N + 15.0 kg P2O5 + 300 g phosphorein increased plants fresh yield by 27.2 and 42.3%
and 16.3 and 10.4% in seed yield over the control in the first and second seasons.
Constantino et al. (2008) evaluated the effects of two rhizobacteria (Azotobacter
chroococcum and Azospirillum) and a commercial product containing multiple strains of
arbuscular mycorrhizal fungi alongwith NPK fertilizer on the growth and yield of habanero
chilli (Capsicum chinese Jacquin) in various combinations. In the nursery phase, single
biofertilization promoted a higher growth and nutrient contents in the crop than combined
biofertilization. However in the field phase the combined biofertilization increased the
nutrient contents of the plant leaves, which were significantly greater than those observed
in the NPK treatments alone. The highest yields were recorded for the treatments involving
a single inoculation of A. chroococcum and for those with the multi-strain of AM fungi as
compared to individual inoculation of N, P and K.
Direkvandi et al. (2008) conducted an experiment to study the effects of different
rates of Nitrogen (N) fertilizer with two types of biofertilizers (0, 125, 75, 225, 125 plus
super-nitro and 125 kg N h-1 plus Nitroxin-biofertilizer) and two cultivars of tomato (Super
Chief and Super Beita) on growth and yield at field conditions. The results revealed that
there were significant differences between N level and most of the characteristics such as
plant height, leaf numbers, fruit number per inflorescence, fruit number per plant, fruit
mean weight and fruit yield. The biofertilizers improved the growth parameters such as
germination rate, plant height, leaf numbers, fruit mean weight and fruit yield. The
maximum yield was accomplished when Super Beita cultivar received 225 kg N h-1.
Similarly, Sharma et al. (2008) conducted field experiment to investigate the response of
broccoli (Brassica oleracea var. italic L.) in integrated nutrient management using organic
manure and Azotobacter alongwith synthetic fertilizers. An application of 100% NPK +
Azotobacter + 20 Mt ha-1 of CM provided the highest increase in the contents of organic C
and available N, P and K respectively. About 31, 8.4 and 12.5 kg ha-1 of N, P and K
respectively can be saved in broccoli production if CM at 20 Mt ha-1 and Azotobacter are
used in combination with synthetic fertilizers.
Premsekhar and Rajashree (2009) studied the effect of various biofertilizers on the
growth, yield parameters and quality of tomato var. CO3 under field experiment. Three
types of biofertilizers, viz., Azospirillum, Phosphate-solubilizing bacteria (PSB) and
Vesicular Arbuscular Mycorrhiza (VAM) in different combinations were tested. The results
revealed that taller plants, better yield parameters and higher yield were recorded
significantly with the application of Azospirillum + 75% N + 100% PK followed by
Azospirillum + 100% NPK. Mahato et al. (2009) carried out similar experiments to
evaluate the responses against biofertilizers and inorganic fertilizer on germination and
growth of tomato plants. Nitrogen was used as inorganic fertilizer and Azotobacter as
biofertilizer. They concluded that Azotobacter showed better results than inorganic fertilizer
in relation to seed germination and all plant-growth parameters.
Naseri et al. (2010) studied the effect of biofertilizers and yield components of
safflower under dry land conditions. Significant improvement was observed in all the
characters with applying biofertilizers and increasing nitrogen from zero to 30 kg/ha but not
30 to 60 kg/ha. There were significant interaction between nitrogen levels and bio-fertilizers
regarding yield components, seed oil and protein content. The highest yield obtained from
the treatments received 30 or 60 kg/ha with Azotobacter inoculation. The highest amount of
seed oil and protein content obtained from the multiinoculation of nitrogen, Azotobacter
and Azospirillum.
Gajbhiye et al. (2010) further studied the effects of biofertilizers (Azotobacter and
Phosphobacterium) and inorganic fertilizers (150 : 60 : 60 kg NPK/ha) on the fruit qualities
of 10 tomato cultivars and their application registered highest locule numbers per fruit,
lycopene content and vitamin-C content.
Sarkar et al. (2010) investigated the influence of nitrogen and biofertilizers on
growth and yield of cabbage. Application of both nitrogen and biofertilizer had significant
impact on growth and yield attributing characters among the different levels of
nitrogen. Application of 100 kg N ha-1 proved to be superior followed by 80 kg N ha-1.
Arumugam et al. (2010) determined the effect of Rhizobium and arbuscular
mycorrhizal fungi, both individually and concomitantly on growth and chlorophyll content
of Vigna unguiculata L. A significant increase in root length, shoot length, dry weights of
root and shoot, total number of nodules, dry weight of nodules, percentage of mycorrhizal
infection, chlorophyll a, b and total was recorded in dual inoculated plants than with
individual ones.
Keeping the importance of these bioinoculants alongwith the presence of plant
extracts Mogle (2011) conducted an experiment to study the effect of biofertilizer and leaf
extract against anthracnose disease of tomato. Results showed that the disease intensity was
significantly reduced by mixed bacterial (Azotobacter and Trichoderma) inoculation and
spray of leaf extract on plants.
Effect of bioinoculants (Azotobacter and Glomus) on nematode control
The nematodes encounter diverge group of rhizosphere microorganisms during
infestation and in many cases, this phenomena can leads to substantial disease control of the
harmful rhizosphere microorganisms. Bacteria and fungi have important roles in the
management of plant-parasitic nematodes on various crops as has been reported by Weller
(1988).
Chahal and Chahal (1988) conducted the experiment in vivo and in vitro to
determine the effects of Azotobacter chroococcum against M. incognita on brinjal. The
biofertilizer A. chroococcum significantly inhibited the hatching of egg-masses of M.
incognita and did not allow the larvae to penetrate into the roots of brinjal to form the galls.
Khan and Kounsar (2000) studied the effect of P. lilacinus, V. chlamydosporium,
Cylindrocarpon destructans, Arthrobotrys oligospora, B. subtilis, Beijerinkia indica,
Azotobacter chroococcum and Azospirillum lipoferum on the growth of mungbean (Vigna
radiata), root nodulation and root-knot disease caused by M. incognita in field experiment.
Application of bacterial and fungal bioagents significantly control the nematode
pathogenesis leading to a decrease of number of galls, egg-masses per root system and J2/kg
soil.
Siddiqui and Mahmood (2001) investigated the effects of rhizobacteria, i.e.
Pseudomonas fluorescens, A. chroococcum and A. brasilense alone and in combination with
root symbionts like Rhizobium sp. and Glomus mosseae on the growth of chickpea and
reproduction of Meloidogyne javanica. Their findings revealed that G. mosseae was found
better at improving plant growth and reducing galling and nematode reproduction than any
other organism. The effect of A. chroococcum was found more pronounced than A.
brasilense for improving growth of nematode infected plants.
Khan et al. (2002) conducted field trials to study the effect of soil application of
rhizobacteria (A. chroococcum, A. lipoferum, B. subtilis and Beijerinkia indica),
antagonistic fungi (A. oligospora, C. destructans, V. chlamydosporium and P. lilacinus)
and fenamiphos on root nodulation, plant growth, biomass production, gall formation and
reproduction of M. incognita on green gram. Their application significantly improved the
growth parameters, egg-mass production and subsequently the soil populations of M.
incognita were adversely affected.
Bansal and Verma (2002) investigated the effects of A. chroococcum inoculation on
root invasion and reproductive potential of M. javanica. The results revealed that A.
chroococcum affect nematodes development and multiplication in the host plant.
Azotobacter inoculation was partially responsible for increased plant growth in brinjal by
alleviating the damaging effect of root-knot nematode.
Chatterjee (2002) used two types of bacteria Azotobacter and Rhizobium sp. using
okra as the host plant infested with M. incognita. The results showed that among the
inoculated schedule of treatments, Azotobacter treatment significantly noticed the best
results and Rhizobium proved to be the least effective.
Jaizme-Vega et al. (2006) studied the effect of the combined inoculation of AM
fungi and PGPR on papaya infected with the root-knot nematode Meloidogyne incognita.
Results revealed that the beneficial effect due to AM inoculation persisted in the presence
of PGPR. Meloidogyne incognita infection was significantly reduced in mycorrhizal
inoculated plants. The dual inoculation of AM fungi and PGPR must be considered for
papaya plant threatened by the root-knot nematode, M. incognita.
Saravanapriya and Subramanian (2007) conducted greenhouse experiments to test
the effect of humic acid alone and in combinations with biofertilizers like Azospirillum and
phosphobacteria, biological control agents (Trichoderma viride, Pseudomonas fluorescens
and Arbuscular mycorrhizal fungus) against M. incognita on tomato. Application of humic
acid with all the bioinoculants significantly increased the plant-growth parameters and
consequently reduced the number of root-galls, egg- masses per plant and final soil
population.
Ugwuoke and Eze (2010) observed the effect of mycorrhiza (Glomus geosporum),
Rhizobium and Meloidogyne incognita on growth and development of cowpea (Vigna
unguiculata L. Walp). Their results clearly revealed that the association of mycorrhiza with
cowpea roots produced lesser galling on roots than nematode alone inoculated plants.
Pandey et al. (2011) employed eco-friendly ways of nematode management
mutualistic endophytes (Trichoderma harzianum strain, Glomus intraradices) and plant
growth promoting rhizobacteria (Bacillus megaterium and Pseudomonas fluorescens) and
assessed their effect individually and in combinations on plant biomass, oil yield of
menthol, reproduction potential and population development of root-knot nematode, M.
incognita under glasshouse conditions. These microbes enhanced the plant biomass and per
cent oil yield both with and without M. incognita inoculations.
Soliman et al. (2011) observed the influence of A. brasilense, P. fluorescens, A.
chroococcum, mixed genera of AM fungi and oxamyl for controlling Meloidogyne
incognita on Acacia farnesiana (L.) Wild and A. saligna (Labill.) in a complete randomized
design. They reported further that both oxamyl and arbuscular mycorrhiza were the most
effective treatments in decreasing the final nematode populations in both soil and roots,
number of galls and rate of buildup of root-knot nematode.
Siddiqui (2004) assessed the influence of P. fluorescens, A. chroococcum, A.
brasilense and composted organic fertilizers alone and in combinations on the
multiplication of M. incognita and growth of tomato under glasshouse experiments. Poultry
manure with P. fluorescens was the best combination for the management of M. incognita
on tomato but management of M. incognita can also be obtained if goat dung is used with P.
fluorescens or poultry manure with A. chroococcum.
Siddiqui and Futai (2009) assessed the effect of antagonistic fungi (A. niger, P.
lilacinus, P. chrysogenum) and plant-growth promoting rhizobacteria (A. chroococcum, B.
subtilis, P. putida) with cattle manure on the growth of tomato and on the reproduction of
M. incognita. Application of antagonistic fungi and PGPR alone and in combinations with
cattle manure resulted in a significant increase in the growth of nematode inoculated plants.
P. lilacinus caused highest reduction in galling and nematode multiplication followed by P.
putida, B. subtilis, A. niger, A. chroococcum and P. chrysogenum.
Khan et al. (2012) conducted an experiment to study the effect of inoculation with
biological nitrogen fixers on growth and yield of chilli ( Capsicum annum L.) cv. “Pusa
Jawala” in relation to disease incidence caused by plant-parasitic nematodes in field
condition. The growth, yield, and quality parameters of chilli increased significantly with
the inoculation of biological nitrogen fixers using Azospirillum and Azotobacter.
Performance of Azospirillum was found better as compared to Azotobacter. Simultaneous
inoculation with biofertilisers (100% recommended dose of N-fertiliser 100 kg N per ha and
farmyard manure 15 t per ha) resulted the maximum growth, yield, and quality parameters.
Thus, the associative nature of the above biofertilisers helps to save 25% nitrogenous
fertiliser in chilli crop. There was increased content in plant nitrogen, phosphate and potash,
leaf chlorophyll and residual available soil nitrogen, phosphate and potash with dual
inoculation with the biological nitrogen fixers alongwith recommended full dose of nitrogen
fertiliser. Disease intensity was recorded in decreasing order in all the treatments but more
pronounced in those where biofertilisers were added.
Role of organic matter in disease management
Organic matter plays pivotal role that affects the crop growth and yield either
directly by supplying nutrients or indirectly by modifying soil physical properties that can
improve the root environment and stimulate plant growth. Organic amendments offered an
alternative or supplementing tactic to chemical or cultural control of nematode pathogens on
agricultural crops. Considerable progress has been made in the utilization of organic matter
as soil amendment for the control of plant-parasitic nematodes (Akhtar and Mahmood,
1993c; Akhtar, 1997). Linford et al. (1938) suggested that organic amendment to soil
stimulated the activity of naturally occurring antagonists of nematode pests and argued that
the activity of these organisms provided control of plant-parasitic nematodes. The
effectiveness of oil-cakes in controlling root-knot nematodes have been documented by
several workers in different crops (Khan and Saxena, 1997; Nagesh et al., 1999).
Numerous plant species representing 57 families have been shown to contain
nematicidal compounds (Sukul, 1992). Neem (Azadirachta indica) is the best known
example by releasing many nematicidal constituents in soil. Neem plant parts like leaf, seed
kernel, seed powders, seed extracts, oil, sawdust and particularly oil-cakes have been
reported as effective for the control of several nematode species (Akhtar and Mahmood,
1996a, Akhtar, 1998). Indian farmers with no knowledge of the chemical constituents of
neem by-products have used them traditionally in pest control for centuries. Neem
constituents such as Nimbin, Salanin, thionemone, azadirachtin and various flavonoids have
nematicidal action (Thakur et al., 1981). Besides the nematicidal effects, triterpene
compounds in neem cake inhibit the nitrification process and increase available nitrogen for
the same amount of fertilizer (Akhtar and Alam, 1993a). Neem oil-seed cakes has been used
extensively in nematode control (Muller and Gooch, 1982). Other available oil-seed cakes
such as castor (Ricinus communis), groundnut (Arachis hypogaea) and Mahua (Madhuca
indica) have also been reported to be effective in nematode control (Lear, 1959 and Akhtar
and Alam, 1991).
Several environmental factors affect nematodes and soil antagonists. The addition of
organic matter to soil stimulates the activity of bacteria, fungi, algae and other
microorganisms in amended soil causes enhanced enzymatic activities (Rodriguez Kabana
et al., 1983) and accumulation of decomposition end products and microbial metabolites
which may be detrimental to plant-parasitic nematodes (Mankau and Minteer, 1962;
Rodriguez-Kabana et al., 1987). Organic amendments release some chemicals into the soil
that are directly responsible for nematode control. Rich et al. (1989) reported that ricin, a
protein derived from castor bean has nemato-toxic potential.
Metabolites produced by microbes during decomposition of organic matter can also
be detrimental to plant-parasitic nematodes. Ammonia, nitrites, hydrogen sulphide, organic
acids, and other chemicals that are produced from organic matter may be directly
nematicidal or affect egg-hatch or the mortality of juveniles (Sayre et al., 1964; Badra and
Eligindi, 1979). Badra et al. (1979) reported that plants growing in amended soil contained
greater concentrations of phenols than those growing in unamended soil and this may
induce disease resistance in roots.
Rodriguez-Kabana et al. (1987) suggested the usefulness for nematode management
by organic additives depends on their chemical compositions and the types of micro-
organisms that develop during their degradation in the soil.
In the recent years, the beneficial effects of certain types of plant derived materials
in soil have been attributed to a decrease in the population densities of plant- parasitic
nematodes (Akhtar and Mahmood, 1996b; Akhtar, 2000). During the last three decades,
several experiments have been conducted on the utility of neem oil-seed cake for
controlling nematode pests on vegetables such as tomato, eggplant, okra and a few pulse
crops (Muller and Gooch, 1982; Akhtar and Mahmood, 1996b).
The nematode population, root-galling and egg-mass production were reduced in
oil-cake amended soil, while the growth of tomato was improved which seems to be due to
reduced disease incidence (Goswami and Vijayalakshmi, 1987). Alam et al. (1980) reported
that fewer juveniles penetrated the roots of plants raised in neem cake amended soil as
compared to untreated control. The mode of action of oil-seed cakes studied by various
workers which leading to the control of plant-parasitic nematodes (Khan et al., 1974).
Tiyagi and Alam (1995) evaluated the efficiency of oil-seed cakes of neem, castor,
mustard and duan against plant-parasitic nematodes infesting mungbean and the subsequent
crop, chickpea in field trials. Several fold improvement was observed in plant-growth
parameters and the residual effects of oil-seed cakes also noted in the subsequent crop. The
population of saprophytic microorganisms increased which may arrest the potential of
pathogenic organisms.
Parveen and Alam (1999) conducted an experiment with oil-seed cakes and leaves
of neem (Azadirachta indica), castor (Ricinus communis) and rice polish, a by-product of
rice milling. All the above treatments significantly controlled Meloidogyne incognita
development and subsequently improved plant-growth parameters. The greatest
improvement was observed in plant-growth parameters of tomato by the addition of neem
cake followed by castor cake, neem leaf, castor leaf and rice polish. Both the cakes gave
better results than inorganic fertilizers (urea + superphosphate + murate of potash) as
compared to control treatment.
Rangaswamy et al. (2000) in a glasshouse experiment evaluated the efficacy of P.
penetrans and Trichoderma viride with botanicals (neem and castor cakes) in controlling
the root-knot nematode, M. incognita in tomatoes. The population of P. penetrans was
effectively controlled by neem cake however, T. viride alone or in combinations with either
neem or castor cake found to be most effective in parasitizing the egg-masses of the
nematodes.
Goswami and Sharma (2001) observed that some fungi such as Aspergillus niger, A.
terreus, F. oxysporum, F. solani, P. oxalicum and P. lilacinus were consistently associated
with egg-masses of root-knot nematode, Meloidogyne incognita in survey of tomato fields.
Both types of fungi such as saprophytic and pathogenic which grew well on medium
containing dried soobabool (Leucaena leucocephala) leaf powder, oil-seed cakes of karanj
(Pongamia pinnata) and/or neem (Azadirachta indica) and molasses were tested against M.
incognita on tomato. Combined application of the both fungal bioagents resulted in better
plant growth than either of the application of bioagents.
El-Sherif et al. (2004) reported greatest suppression in number of root-knot
nematodes, M. incognita galls per root system of sunflower. This was recorded with
sesame oil-cake mixed with oxamyl which improved plant-growth parameters. Yadav et al.
(2006) determined the efficacy of oil-seed cakes (neem, karanj, mustard, castor and mahua)
at the rate of 10, 15 and 20% w/w each as seed dressing treatments on the management of
root-knot nematode, M. incognita infesting chickpea. All the oil-cakes at different
concentrations significantly increased the plant-growth parameters and decreased the
nematode multiplication over the control. Among the oil-cakes, neem cake was the most
effective in improving growth characters and suppressing nematode infestation followed by
karanj cake. The highest concentration (20% w/w) of neem cake was more effective than
lower concentrations.
Anver (2006) found that oil-seed cakes of neem/margosa (A. indica), groundnut (A.
hypogaea), castor (R. communis), mustard (B. compestris), rocket salad/duan (Eruca sativa)
were effectively reducing the multiplication of nematodes.
Javed et al. (2007) tested two types of neem formulations for suppression of root-
galls and egg-masses of M. incognita. The crude form was neem leaves and neem cakes and
another of neem refined products “aza” the protective and curative soil application. These
formulations which significantly reduced the number of egg-masses and galls on tomato
roots.
Kalairasan et al. (2007) revealed that application of oil-cakes significantly increased
the tomato plant growth and decreased the host infestation by root-knot nematode, M.
incognita over control. Among the oil-cakes, cakes of jatropha and neem were proved to be
the best in managing the nematodes. Jatropha cake reduced the egg hatching and increased
the juvenile mortality by 14.07 and 49.33% respectively after 48 h of incubation.
Lopes et al. (2008) conducted an experiment to evaluate the role of agro-industry
wastes such as sugarcane bagasse, Saccharum spp. hybrids, coffeae husks (Coffea arabica),
castor bean oil-cake (Ricinus communis) and jackbean seed powder (Canavalio aensiformis)
applied at the rates of 0.5 or 1.0% (w/w) to control Meloidogyne javanica on tomato. Their
results revealed that jackbean seed powder was most effective in reducing the number of
root-galls and no. of eggs which was followed by castor bean oil-cakes.
Javed et al. (2008) evaluated the potential of combining P. penetrans and neem
(Azadirachta indica) formulations as a management system for root-knot nematode on
tomato. There was significant less root-galling in the P. penetrans combined with neem
cake treatment at the end of the third crop and this treatment also had the greatest effect on
the growth of tomato plants. Meena et al. (2009) assessed the biopesticidal potential of
some organic cakes, viz., neem cake, sesamum cake, mustard cake, cotton cake and castor
cake at the dose of 3 g and 5 g/pot for the management of H. cajani. Such type of amended
cakes were found significantly effective in plant growth promotion and reduction in
nematode population.
Similarly, Radwan et al. (2009) conducted a pot experiment with oil-cakes of cotton,
flax, olive, sesame and soybean at the rate of 5, 10, 15, 20 or 50 g/kg soil against
Meloidogyne incognita infecting tomato that M. incognita population in the soil and root-
galling were significantly suppressed with these cakes at all rates. All oil-cakes exhibited
varying degrees of reduction as compared to the control. The highest reduction in galls was
noted in plants treated with sesame cake whereas the lowest with olive cake.
Tiyagi et al. (2010) studied the effect of some botanicals such as Argemone
mexicana, Calotropis procera, Solanum xanthocarpum and Echhornia echinulata against
plant-parasitic nematodes and soil-inhabiting fungi infesting Trigonella foenum-graecum
under field conditions. Significant reduction was observed in the multiplication of plant-
parasitic nematodes.
Ashraf and Khan (2010) studied the efficacy of biocontrol agents (P. lilacinus and
C. oxysporum) and oil-cakes such as castor, linseed, groundnut, mahua and neem for the
management of root-knot nematode, M. javanica infecting egg-plant under glasshouse
condition. All the treatments effectively suppressed the nematode population and kept the
infection at significantly low level. The highest improvement in plant growth and best
protection against M. javanica was obtained by the integration of P. lilacinus with
groundnut cake followed by neem cake, linseed cake, castor cake and mahua cake. On the
other hand, the integration of C. oxysporum with neem cake followed by groundnut cake,
linseed cake, castor cake and mahua cake gave the best results in managing the damaging
potential of M. javanica on egg-plant.
Application of organic matter influenced soil structure, pH, nutrient and water
holding capacity alone or in combinations with mycorrhizal colonization and efficiency
(Srivastava et al., 1996). The use of AM fungi in combination with oil-cakes in
transplantable crops was found to be highly beneficial in terms of reduced nematode
infection and increased yields (Rao et al., 1997; Parvatha Reddy et al., 1997). It was found
that desirable rhizospheric changes by addition of castor cake to the soil facilitated the
effective utilization of G. fasciculatum for the management of M. incognita in tomato.
Nagesh et al. (1999) observed that mycorrhiza in combination with neem cake recorded
higher plant-growth parameters as compared to carbofuran treated plants which indicating
that the application of these combinations was superior to that of carbofuran. It has been
noted that the organic amendments tend to alter the host-parasite relationships in favour of
the crop (Jothi et al., 2003).
Various chemical substances on decomposition like ammonia, nitrites, hydrogen
sulphide, organic acids and other chemicals that are released from organic matter may be
directly nematicidal or affect egg-hatch or the mobility of juveniles (Rodriguez-Kabana,
1986). There is a direct relation between the amount of nitrogen in organic amendments and
their effectiveness as nematode population suppressors (Mian and Rodriguez-Kabana,
1982).
The magnitude of microbial stimulation and the qualitative nature of the responding
microflora and fauna depends on the nature of the organic matter added. Since organic
amendments take a long time to decompose, the nematicidal properties persisted for a
longer period, sometimes more than six months (Alam et al., 1977). Tilak and Dwivedi
(1990) found that arbuscular mycorrhizal spores exhibited the property of nitrate reducing
ability. It is likely that the symbiotic effectiveness of the arbuscular mycorrhizal fungi is
enhanced in terms of N assimilation and translocation to the host plant. Fungal hyphae may
also increase the availability of nutrients like N and P from locked sources by decomposing
large organic molecules (George et al., 1995). Rao et al. (1997) also observed that
integration of VAM fungus, G. fasciculatum with castor cake caused significant reduction
in root-galling of M. incognita on tomato. Ray et al. (1998) studied the feasibility of
interaction of VA mycorrhiza (G. fasciculatum) and castor cake (R. communis) for the
management of M. incognita on Solanum melongena. Significant improvement in
colonization of G. fasciculatum on roots of egg-plant and chlamydospore densities in this
treatment indicated favourable effects of castor cake amendment.
Borah and Phukan (2004) conducted microplot experiment to know the
compatibility of G. fasciculatum with the application of neem cake and carbofuran 3G for
integrated management of M. incognita on brinjal cv. JV-2. Vesicular arbuscular
mycorrhizal fungus, neem cake and carbofuran alone or in various combinations
significantly decreased root-knot index and nematode population in soil as compared to
nematode alone treated plants.
Pandey et al. (2005) conducted an experiment to assessed the effects of organic
amendments on activity of nematodes and microflora of chickpea rhizospheres. The results
showed that organic amendments significantly increased growth parameters of chickpea.
Higher growth of plants was recorded in neem cake amended soil. The organic amendment
significantly reduced the root-knot (M. incognita) infection but the neem cake resulted the
maximum reduction. The Rhizobium and Azotobacter population increased significantly in
such soil amended with neem cake.
Bhardwaj and Sharma (2006) studied the combined effect of AM fungi with three
different oil-cakes. The oil-cakes of Azadirachta indica, Brassica campestris and Ricinus
communis reduced the damaging potential of the root-knot nematode, Meloidogyne
incognita. Combined use of AM fungi and oil-cakes resulted in reducing the galling and
nematode multiplication, thus improving plant growth and yield. The best results pertaining
to AM root infection, nematode reproduction and plant growth and yield were obtained with
the combination of AM fungi and R. communis oil-cake.
Goswami et al. (2007) compared the percentage response of colonization and
development of a vesicular arbuscular mycorrhiza (Glomus fasciculatum) on a number of
pulse crops such as, cowpea, chickpea, soybean, pigeonpea and lentil under glasshouse
condition. The results showed that the treatments constituting FYM, karanj cake and VAM
reduced the disease incidence to a greater extent with the most promising improvement in
plant-growth parameters as compared to all other treatments.