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STUDIES ON THE COMPATIBILITY OF BACTERIALANTAGONISTS WITH COMMON AGROCHEMICALSAGAINST XANTHOMONAS ORYZAE pv. ORYZAE, THERICE BACTERIAL LEAF BLIGHT PATHOGEN

Purushothaman, S.M1*., Rehumath Niza, T.J2. and Ravi, S3.1Regional Agricultural Research Station,Pattambi – 679 3062Krishi Vignan Kendra, Thrissur - 6806563Associate Director of Extension & Head Plant Pathology, COA, Padanakkad-671314*Email: purushothamansm@yahoo.co.in

Received on: 10 October 2013, accepted on: 12 December 2013

Abstract: Seven bacterial antagonistic bacteria viz., RE-1, RR-26, RR-53, CB-39, VB-67, VB-69 and Pf-1 were sub-jected to compatibility studies against the rice bacterial leaf blight pathogen Xanthomonas oryzae pv. oryzae (Xoo)under in vitro. The study revealed that except the two combinations viz., VB-67 with VB-69 and VB-67 with CB-39,the rest of the 17 combinations showed synergistic effect in inhibiting Xoo. The compatibility of seven antagonistswere tested with nine pesticides viz., chlorpyriphos, dimethoate, triazophos, quinalphos, dichlorvos, carbendazim,mancozeb, propiconazole and hexaconazole and with four fertilizers viz., urea, rajphos, muriate of potash andammonium sulphate under in vitro against Xoo. Out of 91 two way combinations tried, 71 two way combinationswere found having synergestic effect against Xoo and the rest 12 combinations viz., RE-1 with dimethoate, VB-69with dichlorvos, RR-53 with triazophos, Pf1 with carbendazim , VB-69 with hexaconazole, RR-53 with hexaconazole,RR-26 with rajphos, RR-26 with muriate of potash, RR-26 with ammonium sulphate, CB-39 with ammoniumsulphate and RR-53 with rajphos showed non compatible effect against Xoo. The compatibility of thirteen agro-chemicals viz., chlorpyriphos, dimethoate, triazophos, quinalphos, dichlorvos, carbendazim, mancozeb,propiconazole, hexaconazole, urea, rajphos, muriate of potash and ammonium sulphate with nine pesticides viz.,chlorpyriphos, dimethoate, triazophos, quinalphos, dichlorvos, carbendazim, mancozeb, propiconazole andhexaconazole under in vitro against Xoo. The study revealed that out of 71 two way combinations tested, 50 two waycombinations showed synergistic action in inhibiting the pathogen. Three two way combinations viz., quinalphoswith dichlorvos, dichlorvos with urea and hexaconazole with ammonium sulphate showed compatible actionagainst Xoo and the rest 19 combinations viz., chlorpyriphos with carbendazim, chlorpyriphos with urea, dimethoatewith muriate of potash, dimethoate with ammonium sulphate, triazophos with propiconazloe, triazophos withurea, triazophos with muriate of potash, quinalphos with hexaconazole, quinalphos with urea, quinalphos withmuriate of potash, dichlorvos with carbendazim, carbendazim with propiconazloe, carbendazim with hexaconazole,carbendazim with urea, carbendazim with rajphos, carbendazim with muriate of potash, carbendazim with ammo-nium sulphate, hexaconazole with urea and hexaconazole with rajphos showed non compatible effect against Xoo.The compatibility of four fertilizers viz., urea, rajphos, muriate of potash and ammonium sulphate showed that outof six two way combinations, only one namely urea with rajphos showed non compatible action in inhibiting theXoo and the rest f ive two way combinations showed synergistic action in inhibiting the pathogen. All the sevenantagonistic bacteria and 17 agrochemicals showed compatible reaction in inhibiting the Xoo.Key words: Antagonistic bacteria, Pesticides, Fertilizers, Rice bacterial leaf blight, Xanthomonas oryzae pv.oryzae, Inhibition

INTRODUCTION

Bacterial leaf blight (BLB) caused byXanthomonas oryzae pv. oryzae (Xoo) is one ofthe most important diseases of rice and thedisease was f irst noticed by the farmers of Japanin 1884 (Tagami and Mizukami, 1962). Severecrop losses of 10-20% in moderate conditions orup to 50% in highly conducive conditions havebeen recorded in several of Asian and South EastAsian countries (Mew, 1987; Ou, 1985). Globally,

its incidence has been reported from differentparts of Asia, Northern Australia, Africa andUSA. In India, BLB disease has been observedin most important rice-growing stateslike Andhra Pradesh, Bihar, Haryana,Kerala, Orissa, Punjab and Uttar Pradesh.The disease occurred in an epidemic formduring 1998 in Palakkad district of Kerala(Venkatesan and Gnanamanickam, 1999) and

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since then has been observed in severeproportions almost every year. Management ofbacterial blight of rice has been carried out usingchemicals and development of resistant cultivarsover a long period of time. However, theapplication of chemicals is not always effectiveand may also affect the environment. Breedingfor bacterial blight resistance is the mosteconomic strategy of disease management andthis has only been partially successful becauseof the enormous diversity in the pathogen.Recently, transgenic indica rices resistant tobacterial blight have been generated(Narayanan, 2001; Narayanan et al., 2002) butare still to be f ield-evaluated in India.

Biological control, therefore, assumes specialsignif icance in being an ecology-conscious, cost-effective alternative strategy for bacterial blightmanagement. This can also be used inintegration with other strategies to afford greaterlevels of protection and sustain rice yields.Antagonistic bacteria are considered idealbiological control agents, due to reasons likerapid growth, easy handling and aggressivecolonization of the rhizosphere (Weller,1988).The benef icial effects of PGPR includedirect growth promotion, biological control andinducing systemic resistance in host plants.PGPR strain mixtures have showed synergisticaction in plant protection and growthpromotion, indicating different mechanisms areinvolved in disease control. In this study, sevenantagonistic bacteria were subjected amongthemselves and to different agrochemicals tostudy their compatibility against Xoo the ricebacterial leaf blight pathogen.

MATERIALS AND METHODS

While adopting integrated disease managementpractices using antagonists, it is necessary thatthe agrochemicals used in the f ields should becompatible with the biocontrol agents andfurther care must be taken to select suitablecombinations. With this in view, laboratoryexperiments were carried out to study thecompatibility of bacterial antagonists withagrochemicals against Xanthomonas oryzaepv.oryzae (Xoo) the bacterial leaf blight of ricepathogen. Six antagonistic bacteria along withreference culture of KAU-(Pf1) and thirteenagrochemicals were taken for the study. The

details of antagonists, pesticides and fertilizersused for this study are listed below:

All of them were subjected to compatibilitystudies against Xoo under in vitro by paper discmethod. All possible two way combinations werestudied among themselves and withothers.Concentration of different antagonisticbacteria was adjusted to108 cfu/ml. To preparecorrect concentration of agrochemicals as perthe Packages of Practices recommendations(POP) of Kerala Agricultural University, theactual quantity was mixed with 100 ml of sterilewater and the stock solutions were made.Fertilizers were exposed to UV light for 45minutes to avoid the contamination. Three discswere kept in each Petri dish dipped in twomaterials for studying the combination effectand the interaction between them. The discsdipped in single material were used to study theindividual effect and they served as control also.The studies were carried out on PSA mediumseeded with Xoo. Observations on zone ofinhibition of Xoo were recorded after 48 h ofincubation.

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Table 1. Com

patibility of bacterial antagonists with com

mon agrochem

icals againstX

oo

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Tabl

e 2.

Com

pati

bilit

y of

bac

teri

al a

ntag

onis

ts w

ith

com

mon

agr

oche

mic

als

agai

nst

Xoo

Ass

umpt

ion

Tabl

e (a

+b)

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RESULTS AND DISCUSSION

The compatibility of the six promisingantagonistic bacteria viz., RE-1 (rice endospherebacteria from Kodallur), RR-26 (rhizospherebacteria from Nenmara), RR-53 (rhizospherebacteria from Pattambi) CB-39 (bacteria from cowdung), VB-67 and VB-69 (bacteria f romvermicompost) along with reference culture ofKAU-(Pf1) with pesticides and fertilizers amongthemselves in two way combinations werestudied and the results are presented in Table 1.

In the table, the inhibition presented asinteraction of 1 with 1, 2 with 2, likewiserepresents, the individual effect of antagonist,pesticide or fertilizer as the case may be. It wasconsidered as ‘a’ or ‘b’ as the study dealt withthe individual and combined effect of these twomaterials. Therefore, ‘a’ and ‘b’ represent theindividual effect (inhibition) on the pathogen.Likewise, the value in the interaction of 1 and 2represents the combined effect of 1 and 2 and isrepresented as combined effect of ‘a+b’. The dataindicated that some combined effects were lessthan the half of additional value of ‘a+b’ (lessthan the individual inhibition effects) denotingthat they were non compatible. In some cases,the combined effects were equal to themathematical addition of a+b, indicating theirinteraction resulted in additive interaction, whilesome combinations resulted in the inhibitionwhich was more than the additive effect of thecomponent materials, suggesting a synergisticeffect by their interaction. Some values showedthat they are better than individual inhibitionbut not up to the level of addition, they aredenoted as compatible. Hence, to interpret thedata on compatibility and interaction among thestudy materials, the following calculations weremade. The interaction values obtained arepresented in the Table 2.

For easy understanding of the above table, thefollowing notations are given and the table with‘non compatible’, ‘compatible’, ‘additive’ and‘synergistic’ interactions were made. An errorcomponent of 0.05 is allowed.

The compatibility of bacterial antagonists withagrochemicals against Xoo were studied and theresults are presented in Table 3. 21 types of twoway combinations among the seven antagonisticbacteria were studied for their compatibilityagainst Xoo. Among them, two combinationsviz., VB-67 with VB-69, VB-67 with CB-39showed non compatible effect in inhibiting theXoo. The rest of the 17 combinations showedsynergistic effect in inhibiting the Xoo.Ramamoorthy et al. (2001) opined that,management of multiple pathogens and pestsin crop plants can be achieved by applyingmixture of strains showing synergistic action.

The compatibility of six antagonists viz., RE-1,RR-26, RR-53, CB-39, VB-67 and VB-69 alongwith the reference culture Pf1 were studied withnine pesticides viz., chlorpyriphos, dimethoate,quinalphos, dichlorvos, triazophos, carbendazim,mancozeb, propiconazole and hexaconazole andwith four fertilizers viz., urea, rajphos, muriateof potash and ammonium sulphate under invitro against Xoo. The study showed that, outof 91 two way combinations tried, 12combinations viz., RE-1 with dimethoate, VB-69with dichlorvos, RR-53 with triazophos, Pf1 withcarbendazim, VB-69 with hexaconazole, RR-53with hexaconazole, RR-26 with rajphos, RR-26with muriate of potash, RR-26 with ammoniumsulphate, CB-39 with ammonium sulphate andRR-53 with rajphos showed non compatibleeffect against Xoo and the rest showedsynergestic effect against Xoo. The compatabilityof P. f luorescens with carbendazim is inagreement with the result of Vidhyasekaran andMuthamilan (1996) and compatability of P.fluorescens with mancozeb is in agreement with

the works of Mathew(2003), Bhavani (2004) andPaul (2004). Kumar et al. (2011) also reportedthe compatibility of Bacillus subtilis MBI 600(commercial formulation, Integral) withcarbendazim and azoxystrobin up to 400 ppm.

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Tabl

e 3.

Com

patib

ility

of

bact

eria

l ant

agon

ists

with

com

mon

agr

oche

mic

als

agai

nst

Xoo

(Int

erpr

etat

ion

Tabl

e)

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The compatibility of P. f luorescens withquinalphos and chlorpyriphos is in agreementwith the results of Mathew (2003) and Paul(2004). Bhavani (2004) observed that thefertilizers viz., rajphos and muriate of potashwere compatible with the antagonists, where asurea, ammonium chloride and ammoniumsulphate showed varying levels of inhibition,indicating their partial compatibility.

The compatibility of 13 agrochemicals viz.,chlorpyriphos, dimethoate, triazophos,quinalphos, dichlorvos, carbendazim, mancozeb,propiconazole, hexaconazole, urea, rajphos,muriate of potash and ammonium sulphate withnine pesticides viz., chlorpyriphos, dimethoate,triazophos, quinalphos, dichlorvos, carbendazim,mancozeb, propiconazole and hexaconazole wasstudied under in vitro against Xoo. The studyrevealed that out of 71 two way combinationstested, 19 combinations viz., chlorpyriphos withcarbendazim, chlorpyriphos with urea,dimethoate with muriate of potash, dimethoatewith ammonium sulphate, triazophos withpropiconazloe, triazophos with urea, triazophoswith muriate of potash, quinalphos withhexaconazole, quinalphos with urea, quinalphoswith muriate of potash, dichlorvos withcarbendazim, carbendazim with propiconazloe,carbendazim with hexaconazole, carbendazimwith urea, carbendazim with rajphos,carbendazim with muriate of potash,carbendazim with ammonium sulphate,hexaconazole with urea and hexaconazole withrajphos showed non compatible effect againstXoo. Three two way combinations viz.,quinalphos with dichlorvos, dichlorvos with ureaand hexaconazole with ammonium sulphateshowed compatible action against Xoo and therest 50 two way combinations showed synergisticaction in inhibiting the pathogen. Manav andThind (2001) also studied the in vitro eff icacyof f ive chemicals against Xoo by paper discdiffusion method and found that coppersulphate and monocrotophos could inhibit thebacterial growth.

The compatibility of four fertilizers viz., urea,rajphos, muriate of potash and ammoniumsulphate showed that, out of six two waycombinations, only one namely urea with rajphosshowed non compatible action in inhibiting theXoo and the rest f ive two way combinations

showed synergistic action in inhibiting thepathogen. All the seven antagonistic bacteria and17 agrochemicals showed the compatiblereaction in inhibiting the Xoo.

It is concluded that except the antagonisticculture VB-67 with VB-69, VB-67 with CB-39 restof the combinations were showed the synergisticeffect in inhibiting the Xoo. More over they werefound compatible with the most of thecommonly used agrochemicals in riceecosystem. Hence, the promising Pseudomonassp cultures can be made into a microbialconsortia for the management of bacterial blightof rice.

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Manav, M., Thind, B.S. and Manav, M. 2001.Management of bacterial blight of rice withnon-conventional chemicals. Plant Dis. Res.,16: 214-219.

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Mew, T.W. 1987. Current status and futureprospectus of research on bacterial blightof rice. Annu. Rev. Phytopathol., 25: 359-82.

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Narayanan, N.N., Baisakh, N., Vera Cruz, C.M.,Gnanamanickam, S.S., Datta, K. and Datta, S.K.2002. Molecular breeding for the development

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