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Life Table and Population Parameters of Schizaphisgraminum (Rondani) (Hemiptera: Aphididae) on SixWheat GenotypesAuthor(s): Behshid Barkhordar , Jafar Khalghani , GholamrezaSalehi Jouzani , Gadir Nouri Ganbalani , and Mahmood ShojaiSource: Entomological News, 122(4):336-347. 2011.Published By: The American Entomological SocietyDOI: http://dx.doi.org/10.3157/021.122.0407URL: http://www.bioone.org/doi/full/10.3157/021.122.0407

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LIFE TABLE AND POPULATION PARAMETERS OFSCHIZAPHIS GRAMINUM (RONDANI) (HEMIPTERA:

APHIDIDAE) ON SIX WHEAT GENOTYPES1

Behshid Barkhordar,2 Jafar Khalghani,3 Gholamreza Salehi Jouzani,4

Gadir Nouri Ganbalani,5 and Mahmood Shojai6

ABSTRACT: Biological parameters of Schizaphis graminum (Rondani) reared on an ancient wheatspecies (Einkorn) from England and five Iranian wheat genotypes (Azadi, Ommid, Marvdasht,Pishtaz and Moghan 2) were studied under controlled conditions at 22 ± 1°C, 65 ± 5% RH, 16:8(L:D) h. The lowest rm value (0.261± 0.002 females/female/day) and net reproductive rate (R0)(28.747± 0.369) were recorded on Einkorn. The highest and the lowest finite rates of increase (λ)were on Moghan 2 and Einkorn, respectively. Also, the longest mean generation time (T) and dou-bling time (DT) with the lowest percentages of nymphal survival (79.5%) and fecundity over devel-opmental time (35.739± 0.378 nymphs/female/day) were obtained on Einkorn. Adult longevity var-ied from 10.72± 0.123 days on Einkorn to 18.04± 0.212 days on Moghan 2. Therefore, our resultsshowed that Einkorn, exerting a high level of antibiosis compared to other tested genotypes, maydecrease the population density of the greenbug.

KEY WORDS: biological parameters, Einkorn, Iranian wheat genotypes, plant resistance,Schizaphis graminum

INTRODUCTION

The greenbug, Schizaphis graminum (Rondani), is a worldwide pest of gra -minaceous plants that has been recognized as a major pest of small grains in North,Central and South America, Europe, Africa, the Middle East and Asia (Burd etal., 2006). Both winter and spring grains can be severely damaged by greenbugpopulations. Enzymatic activity of greenbug’s saliva breaks down cell walls andchloroplasts in susceptible plants (Dorschner et al., 1987). It causes yellow or redleaf spots and continued feeding may lead to general yellowing, leaf and rootdeath, and finally to plant death. Also, greenbugs transmit some plant virusesincluding barley yellow dwarf (Rezvani, 2001), sugarcane mosaic (Ingram andSummer, 1938) and maize dwarf mosaic viruses (Nault and Bradley, 1969).

Despite the fact that insecticides have proved effective in controlling green-bugs in small grain crops (Hays et al., 1999), the more economical solution

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______________________________1 Received on March 10, 2012. Accepted on July 7, 2012.2 Corresponding author. Department of Entomology, Science and Research Branch, Islamic AzadUniversity, Tehran, Iran. E-mail: behshid_barkhordar@yahoo.com

3 Plant Protection Institute, Agricultural Research, Education and Extension Organization (AREEO),Tehran, Iran. E-mail: Khalghani@gmail.com

4 Department of Microbial Biotechnology and Biosafety. Agricultural Biotechnology Research Insti -tute of Iran (ABRII), Karaj, Iran. E-mail: gsalehi@abrii.ac.ir

5 Department of Plant Protection, College of Agriculture, University of Mohaghegh Ardabili, Ardabil,Iran. E-mail: gadirnouri@yahoo.com

6 Department of Entomology, Science and Research Branch, Islamic Azad University, Tehran, Iran.E-mail: mahmoodshojaii@yahoo.com

Mailed on January 24, 2013

remains to be host plant resistance. One of the most important compounds ofwheat as a source of natural resistance is hydroxamic acid (Hx), although thedensity and type of trichomes on leaf surfaces of wheat varieties can affect theaphid population growth (Escobar and Niemeyer, 1993; Kazemi et al., 1988).

Several studies have already been conducted to detect at least one relativelyresistant variety to control aphids in order to decrease insecticide applications(Roberts and Foster, 1983; Papp and Mesterhazy, 1993; Khalghani, 1994; Kaze -mi et al., 2001; Ozder, 2002; Razmjou et al., 2006; Taheri et al., 2010). How ever,there is still insufficient data for some other genotypes. It seems imperative todeter mine growth parameters of the pest on different host genotypes, should anaccurate IPM decision be made to control the aphid. To this end, the life tabletechnique represents a reliable index to evaluate the fitness and the level of plantresistance to aphids and other pests (Foster et al., 1988; Nkongolo et al., 1990;Hes ler et al., 1999; Tsai and Wang, 2001; Satar and Yokoni, 2002; Frel et al.,2003; Razmjou et al., 2006; Silva et al., 2006; Ma and Bechinski, 2009; Obopileand Ositile, 2010; Taheri et al., 2010). Therefore, the aim of the present studywas to evaluate the degree of resistance of six wheat genotypes to S. graminum,and their effects on biological parameters of the aphid, such as the life tableparameters.

METHODS

PLANTS: Five Iranian wheat genotypes including Azadi, Ommid, Marvdasht,Pishtaz and Moghan 2 (Triticum aestivum) that are commonly planted in Iran andan ancient British wheat species, Einkorn (T. monococcum) were used in theseexperiments. These genotypes were selected based on their area of cultivationand also based on their level of resistance to the pest according to previous stud-ies (Khalghani, 1994; Kazemi, 1988; Kazemi et al., 2001; Shahrokhi-Khaneg -hah, 2003). The seed samples of Einkorn were generously provided by van Em -den (Reading University, UK), and the seed samples of other five genotypes werekindly obtained from the Seed and Plant Improvement Institute of Iran (Karaj,Iran). The seeds of Ommid (winter wheat genotype) were put in a box contain-ing a few drops of distilled water, covered with aluminum foil and vernalized inthe refrigerator at 4±1ºC for eight weeks according to the procedure by Kazemi(1988). Plastic pots (7 cm diameter and 15 cm height) were filled with soil andcompost, planted with five wheat seeds at 2 cm-depth and thinned to three plantsper pot after germination by adapting the method used by van Emden et al.(1991). Third leaf stages of wheat plants were used for experimentation. Twenty-five replications were allocated to each genotype.

APHIDS: Greenbugs used in these experiments were originally obtained froma stock culture kept at the Tarbiat Modares University (Tehran, Iran). This cul-ture has been maintained at the laboratory for many generations without infusionof wild-type greenbugs. We reared the aphids on susceptible wheat seedlings

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(Pish taz genotype) in dutt cages (ventilated cylindrical plexiglass cages 15 cmdiameter and 70 cm height) according to the procedure used by Khalghani (1994)and kept in a controlled chamber at a temperature of 22 ± 1°C, RH of 65 ± 5%and 16:8 (L:D) photoperiod at the Agricultural Biotechnology Research Instituteof Iran (ABRII, Karaj, Iran). Aphids were reared on the test plants for at least twogenerations to eliminate the possible preconditioning effect of the previous hostplant (Apablaza and Robinson, 1967; Adams and van Emden, 1972; Kay et al.,1981; Shufran et al., 1992; Jyoti et al., 2006).

EXPERIMENTAL CONDITIONS: After producing cohorts of the first-instarnymphs, each of them was individually placed in a leaf cage (Petri dishes with 5cm diameter and 1.5 cm height by 3 cm diameter hole in the middle) accordingto Shahrokhi-Khaneghah (2003), and put on the upper leaf of the experimentalplant to avoid escape or parasitism. These nymphs were of approximately thesame age and weight. Body size and exuviae from molting were the criteria todis criminate the developmental stages of greenbugs. The position of the cageswas changed once every three to four days to avoid local leaf damage. The exper-iment was carried out in a completely randomized design with six treatments(wheat genotypes), each replicated twenty-five times.

LIFE TABLE PARAMETERS: The survivorship of apterous aphids and eachnymph were recorded at 24-h intervals. The percentages of survival of each off-spring on all examined genotypes as well as the longevity of each aphid were cal-culated. The developmental time (time from birth till first offspring), reproduc-tive period and fecundity were measured on different wheat genotypes. Adultlongevity was measured after the immatures became adults through daily inspec-tion for reproduction and survival. In each observation the number of newbornnymphs were counted and then removed. The experiment was continued until thedeath of the last aphid. The intrinsic rate of natural increase (rm) of apterousaphids on different wheat genotypes was calculated according to Birch’s model(1948) as follows:

∑e–rxlxmx = 1.

The net reproductive rates (R0 = ∑lxmx), mean generation time (T = lnR0/r),doubling time (DT), and finite rate of increase (λ = er) were estimated accordingto Carey (2001).

DATA ANALYSIS: The parameters of development and fecundity were ana-lyzed using SAS software version 9.0 (SAS Institute, 2000). Means were com-pared by Duncan’s test at α = 0.05 (SAS Institute, 2000). The variance of the lifetable para meters including the intrinsic rate of natural increase (rm), net repro-ductive rate (R0), doubling time (DT), finite rate of increase (λ) and the meangeneration time (T) were estimated by the Jacknife technique (Meyer et al.,

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1986; Maia et al., 2000; Carey, 2001) using the SAS System version 9.0 (SASInstitute, 2000). One-way analysis of variance (ANOVA) was conducted to ana-lyze the difference in the means of developmental time, reproductive period,adult longevity, post reproductive period and fecundity over developmental time.

RESULTS

DEVELOPMENTAL TIME AND SURVIVORSHIP OF NYMPHS

The developmental time of nymphal stages of S. graminum indicated significantdifferences among the tested wheats (F = 747.32, df = 5, P < 0.0001). Thenymphs reared on Einkorn had the longest developmental time (10.7 days). Thepercentage of nymphal survival was the highest on Moghan 2 (92%) and the low-est on Einkorn (79.5%) (Table 1).

REPRODUCTIVE PERIOD, POST REPRODUCTIVE PERIOD,ADULT LONGEVITY AND FECUNDITY

The tested wheats induced significant differences in the reproductive period ofaphids (F = 141.17; df = 5; P <0.0001). The shortest reproductive period wasrecorded on Einkorn and the longest was on Pishtaz and Moghan 2 with no sig-nificant difference. Also, the aphid showed different post reproductive periods onthe examined wheat genotypes (F = 127.73; df = 5; P <0.0001) so that the longestpost reproductive period was recorded on Moghan 2 and the shortest on Einkornand Azadi with no significant difference between the latter two. The adult lon -gev ity also showed significant variations (F = 291.87; df = 5; P <0.0001). Theshortest adult longevity was observed on Einkorn and Azadi with no significantdifference, but the longest was on Moghan 2 (18.04 days) (Table 1). There werealso significant differences in the mean total number of offspring produced overdevelopmental time among aphids reared on Einkorn and the other five wheatgeno types (F = 352.35; df = 5; P < 0.0001). The lowest fecundity of the aphidwas on Einkorn and the highest was on Marvdasht, Moghan 2 and Pishtaz withno significant differences among them (Fig. 1).

LIFE TABLE PARAMETERS

Different wheat genotypes affected population growth parameters of S. gra -m inum differently (Table 2). The intrinsic rate of natural increase (rm) differedsignificantly between Einkorn and the other five wheat genotypes (F = 606.11, df= 5, P<0.0001). A significant reduction of population growth rate occurred onEin korn while the highest increase occurred on Pishtaz and Moghan 2 (Table 2).

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340 ENTOMOLOGICAL NEWS

The values of the net reproductive rate (R0) of aphids indicated significant dif-ferences among the wheat genotypes (F= 349.92, df= 5, P < 0.0001). The aphidsfed on Einkorn had the lowest R0 values (28.747 aphids), but there were no sig-nificant differences between Marvdasht, Pishtaz and Moghan 2 which showedthe highest R0 values (Table 2). The mean generation time values (T) of green-bugs fed on different genotypes indicated significant differences (F= 34.74, df=5, P< 0.0001), however, the same values were recorded for Einkorn, Azadi andOmmid genotypes. Doubling time (DT) differed among the wheat genotypes sig-nificantly (F = 596.20, df = 5, P< 0.0001) and ranged from 2.012 on Moghan 2to 2.657 on Einkorn. There was no difference between Moghan 2 and Pishtaz.Fur ther more, the finite rate of increase (λ) values of S. graminum indicated sig-nificant differences (F = 597. 27, df = 5, P< 0.0001), being higher on Pishtaz andMoghan 2 than on the others. The lowest (λ) value was on Einkorn (Table 2).

DISCUSSION AND CONCLUSION

The present study was designed to determine the effect of wheat resistance tobiological parameters of a worldwide pest of graminaceous plants, S. graminum.The results of this study demonstrated that the life history parameters of theaphid were significantly influenced by the genotype and level of wheat resist-ance. Developmental time is likely to be faster for aphids feeding on a high qual-

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Fig. 1 Fecundity over developmental time of S. graminum on six wheat genotypes (Meannumber of nymph/female ±SE). Means followed by the same letters in each column arenot significantly different (P≥0.05)

Einkorn Azadi Ommid Marvdasht Pishtaz Moghan2

Nymph/female

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ity host than on a poor quality host (Dixon, 1987). In the present study, the meannumber of days from birth to reproduction of S. graminum was higher than thatrecorded by Shahrokhi-Khaneghah (2003) on other wheat varieties (7.8- 8.47days) and Tofangsazi et al. (2011) on barley varieties (6.35-6.75 days). Ourresults also indicated that the developmental time of immature stages of S. gra -minum was longer than Sitobion avenae (7.92-9.25days) and Rhopalosiphumpadi (4.37-5.53 days) which were reported by Khalghani (1994); Razmjou andGoli zadeh (2010) and Taheri et al. (2010) reared them on other wheat varieties,respectively (Table1).

In the current study Einkorn and Moghan 2 showed the lowest and the highestrates of survivorship of aphids respectively, which corroborates the findings ofthe previous work on different varieties (Shahrokhi-Khaneghah, 2003; Taheri etal., 2010). The shortest reproductive period, post reproductive period and adultlon gevity were on Einkorn and Azadi and the longest were on Moghan 2. In con-trast to earlier findings, these parameters were lower in the present study. Taheriet al. (2010) and Tofangsazi et al. (2010) found that the adult longevity of R. padiand S. graminum were between 16.1-27.3 days and 29.04-33.29 days on wheatand barley varieties respectively (Table 1).

The fecundity over developmental time in the present study was between35.739 to 69.909 nymphs/female on Einkorn and Marvdasht. There were no sig-nificant differences between Marvasht, Pishtaz and Moghan 2 for this parameter(Fig. 1). These results showed a higher total number of offspring/female ofS. graminum than in some published studies. Shahrokhi-Khaneghah (2003) re -ported that the total fecundity of greenbug was 33.16 on Kavir wheat variety to59.69 nymphs per female on Tabasi variety. Also the fecundity of S. graminumon barley varieties was 35.14-51.43 nymphs per female (Tofangsazi et al., 2010),which is considerably lower than the data obtained in this study.

The rm values of the greenbug as an important indicator of insect populationgrowth that can be influenced by reproduction, mortality and nymph develop-mental time (McCauley et al., 1990), varied between 0.261 on Einkorn to 0.344females/female/day on Moghan 2. The higher rm values indicated that greenbughad a greater potential to reproduce on genotypes such as Moghan 2 and Pishtazthan on Mardasht, Ommid, Azadi and Einkorn. The low rm value on Einkornindicated that this variety has a considerable antibiosis, causing reduced survivaland reproduction (Table 2). In contrast to earlier findings, however, we obtainedthe highest rm value for the tested wheat genotypes. Shahrokhi-Khaneghah(2003) found the highest rm value (0.310 per day) on Niknezhad and the lowestrm value (0.252 per day) on Kavir variety. Azadi as the same wheat varietyshowed the rm value of 0.275 per day in our study differing from Shahrokhi-Khaneghah (2003) results. Tofangsazi et al. (2011) showed different rm value ofS. graminum (0.299 to 0.336 per day) reared on barley variety. The rm value ofthe same species reared on Paspalum vaginatum was different compared to thepresent study (Nuessley et al., 2008).

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Khalghani (1994) found the lowest rm value of S. avenae reared on Einkorn(0.231 per day) and the highest rm on Tonic, Timmo, Axona and Moghan 1 withno significant differences. Also the rm value of Ommid variety in the currentstudy (0.266 per day) was different from the value obtained by Khalghani (1994)which was 0.292 per day. Kazemi et al. (2001) showed that the highest and thelowest rm values of Diuraphis noxia were on Sardari (0.340 per day) and Zarrin(0.289 per day) wheat varieties. Taheri et al. (2010) found that the highest andthe lowest rm values of R. padi were on Niknezhad (0.381 per day) and Darab 2(0.328 per day) wheat varieties. Some studies using other host plants found thatantibiosis was the mechanism of resistance to different aphid species (Bayhan,2010; Golawska, 2010; Obopile and Ositile, 2010; Razmjou and Golizadeh,2010; Takallozadeh, 2010).

Significant difference has been reported for R0 values of the aphid on variouswheat genotypes. In the current study, the lowest R0 value of S. graminum Ein -korn was on Einkorn which is lower than the value reported by Shahrokhi-Khaneghah (2003) and Tofangsazi et al. (2011). Marvdasht, Pishtaz and Moghan2 induced the highest R0 value with no significant differences (Table 2). Finiterate of increase (λ) also had the lowest value on Einkorn and the highest valueon Pishtaz and Moghan 2. The diffrences in rm and λ values can be explained bydiffrent R0 values of greenbugs on the studied host plants (Table 2). The DTvalue of greenbugs on Einkorn was longer than other genotypes and also themean generation time (T) was longer on Einkorn, Azadi and Ommid with no sig-nificant differences. These factors may explain the unsuitability of Einkorn foraphid population growth.

In the present study, the mean generation time and population doubling time ofgreenbug were lower than those reported by Shahrokhi-Khaneghah (2003) ondifferent wheat varieties and higher than the mean generation reported by To -fang sazi et al. (2011) on barley varieties. However, the finite rates of increase ofgreenbug reported by Tofangsazi et al. (2011) being 1.348–1.400 on barley andthat reported by Shahrokhi-Khaneghah (2003) being 1.282–1.358 on wheat vari-eties were similar to the results obtained in the current study.

The lowest rm value, as an important indicator of insect population growth, onEinkorn showed the poor performance of S. graminum on this species. Also otherparameters such as the longest developmental time, shortest reproductive periodand adult longevity, lowest R0, DT, T, λ could categorize the Einkorn as the high-ly resistant wheat amongst the studied wheat genotypes. Also taking into con-sideration the biological parameters of S. graminum, Azadi and Ommid could becharacterized as resistant and semi-resistant varieties respectively. Marvdasht,Pishtaz and Moghan 2 could be categorized as semi-susceptible and susceptiblerespectively with no significant differences between Pishtaz and Moghan 2.

The differences in life table parameters of aphids among different studies maybe attributed to different host plants exerting different effects, different wheatgenotypes, as well as different aphid species. Also, environmental conditions of

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the investigations could be another source of variation in the results. Anotherpossible explanation for the differences between the studied wheat resist ancesmight be because of the different levels of hydroxamic acid (Hx) be tween wheatgenotypes. Also the density and types of trichomes on the leaf surfaces of thetested wheats might contribute to these differences between genotypes. There -fore, present results may provide helpful information for comprehensive IPMprograms of greenbug. Further studies are needed to focus on the interactionbetween environment and genotypic resistance of wheat genotypes against S. grami num and to identify other mechanisms of these genotypes.

ACKNOWLEDGMENTS

The authors greatly appreciate the Agricultural Biotechnology Research Institute of Iran (ABRII)and especially Dr. Khayyam Nekouie for supporting this project. We are thankful to Professor vanEmden for providing the Einkorn seeds from England and the Seed and Plant Improvement Institutefor providing seeds of Iranian wheat genotypes. We also appreciate Mrs. Kazemi for providing theaphids and Dr. Shahrokhi-Khaneghah for helping in data analysis. We also thank Mr. Karimi, Mr.Boustani, Mr. Dalvand and Mrs. Karami for their help during this study.

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