Changes in protein profile of pigeonpea genotypes in response to NaCl and boron stress

Two pigeonpea [Cajanus cajan (L.) Millsp.] genotypes, a salt tolerant Manak and a salt sensitive ICPL 88039 were subjected to stress treatment of 3 mM boron, 60 mM NaCl and boron + NaCl at the seedling stage. Radicle and plumule proteins were analyzed by SDS-PAGE. Boron treatment increased 28.3 kDa proteins in plumule and 38.3 and 51.9 kDa proteins in radicle of Manak, however, there was no specific protein in ICPL 88039 either in plumule or in radicle. In NaCl treatment 95.6 kDa proteins appeared in plumule and 67.5 kDa proteins in radicle of Manak. Conversely content of some proteins decreased by boron treatment alone or in combination with NaCl although they were present in the controls. Thus, 54.3 kDa protein disappeared in ICPL 88039 plumule, 68.4 kDa in Manak radicle and 28.1 kDa in ICPL 88039 radicle.     

Mechanisms of resistance to Helicoverpa armigera and introgression of resistance genes into F1 hybrids in chickpea

The noctuid pod borer, Helicoverpa armigera is a major pest of chickpea, and host plant resistance is an important component for managing this pest. We evaluated a set of diverse chickpea genotypes with different levels of resistance to H. armigera, and their F₁ hybrids for oviposition non-preference, antibiosis, and tolerance components of resistance under uniform insect infestation under greenhouse/laboratory conditions. The genotypes ICC 12476, ICC 12477, ICC 12478, ICC 12479, and ICC 506EB were non-preferred for oviposition under no-choice, dual-choice, and multi-choice conditions, and also suffered lower leaf damage in no-choice tests as compared to the susceptible check, ICCC 37. Antibiosis expressed in terms of low larval weights was observed in insects reared on ICC 12476, ICC 12478, and ICC 506EB. Weight gain by the third-instars was also low on ICC 12476, ICC 12477, ICC 12478, ICC 12479, and ICC 506EB at the podding stage. Non-preference for oviposition and antibiosis (poor larval growth) were also expressed in hybrids based on ICC 12477, ICC 12476, ICC 12478, ICC 12479, and ICC 506EB as compared to the hybrids based on the susceptible check, ICCC 37, indicating that oviposition non-preference and antibiosis in the F₁ hybrids is influenced by the parent genotype. Loss in grain yield was lower in ICC 12477, ICC 12478, ICC 12479, and ICC 506EB compared to that on ICCC 37. The genotypes ICC 12477, ICC 12478, ICC 12479, and ICC 506EB showing antixenosis, antibiosis, and tolerance mechanism of resistance to H. armigera can be used for developing chickpea cultivars for resistance to this pest.     

Single feature polymorphisms (SFPs) for drought tolerance in pigeonpea (<Emphasis Type="Italic">Cajanus</Emphasis> spp.)

Single feature polymorphisms (SFPs) are microarray-based molecular markers that are detected by hybridization of DNA or cRNA to oligonucleotide probes. With an objective to identify the potential polymorphic markers for drought tolerance in pigeonpea [Cajanus cajan (L.) Millspaugh], an important legume crop for the semi-arid tropics but deficient in genomic resources, Affymetrix Genome Arrays of soybean (Glycine max), a closely related species of pigeonpea were used on cRNA of six parental genotypes of three mapping populations of pigeonpea segregating for agronomic traits like drought tolerance and pod borer (Helicoverpa armigiera) resistance. By using robustified projection pursuit method on 15 pair-wise comparisons for the six parental genotypes, 5,692 SFPs were identified. Number of SFPs varied from 780 (ICPL 8755 × ICPL 227) to 854 (ICPL 151 × ICPL 87) per parental combination of the mapping populations. Randomly selected 179 SFPs were used for validation by Sanger sequencing and good quality sequence data were obtained for 99 genes of which 75 genes showed sequence polymorphisms. While associating the sequence polymorphisms with SFPs detected, true positives were observed for 52.6% SFPs detected. In terms of parental combinations of the mapping populations, occurrence of true positives was 34.48% for ICPL 151 × ICPL 87, 41.86% for ICPL 8755 × ICPL 227, and 81.58% for ICP 28 × ICPW 94. In addition, a set of 139 candidate genes that may be associated with drought tolerance has been identified based on gene ontology analysis of the homologous pigeonpea genes to the soybean genes that detected SFPs between the parents of the mapping populations segregating for drought tolerance.     

Tolerance to reniform nematode (Rotylenchulus reniformis) race A in pigeonpea (Cajanus cajan) genotypes

The reniform nematode (Rotylenchulus reniformis) is an important pathogen of pigeonpea (Cajanus cajan). Forty‐six medium maturity (mature in 151–200 days at Patancheru, India) pigeonpea genotypes were evaluated for resistance and tolerance to the reniform nematode in greenhouse and field tests, over the period 1990–97. Each genotype was screened for number of nematode egg masses on a 1 (no egg mass = highly resistant) to 9 (> 50 egg masses = highly susceptible) scale. Plant biomass production in carbofurantreated plots was compared with that in non‐treated plots in a field naturally infested with R. reniformis. Pigeonpea genotypes C 11, ICPL 87119 and ICPL 270 were used as nematode susceptible checks. Genotypes with good plant growth, both in nematode‐free and nematode‐infested plots, were identified as tolerant and evaluated for plant growth and yield for at least three years. All the tested genotypes were susceptible (7 and 9 egg mass score). Single‐plant‐selections, based on plant vigour and yield, were made from genotypes showing tolerance to nematode infection. The level of tolerance was enhanced by plant‐to‐progeny row selection for plant vigour and seed yield in a nematode‐sick field for at least three years. The most promising nematode tolerant genotypes produced significantly greater yield and biomass than the locally grown pigeonpea cultivars in fields naturally infested with R. reniformis at two locations. Pigeonpea landraces are considered to be the most likely sources of tolerance to the nematode. These reniform nematode tolerant lines represent new germplasm and they are available in the genebank of pigeonpea at ICRISAT bearing accession numbers ICP 16329, ICP 16330, ICP 16331, ICP 16332, and ICP 16333.     

Pod surface exudates of wild relatives of pigeonpea influence the feeding preference of the pod borer, Helicoverpa armigera

Wild relatives of crops are an important source of resistance genes against insect pests. However, it is important to identify the accessions of wild relatives of crops with different mechanisms of resistance to broaden the basis and increase the levels of resistance to insect pests. Therefore, we studied the feeding behavior of pod borer, Helicoverpa armigera, which is the most damaging pest of pigeonpea, in relation to biochemical characteristics of the pod surface exudates in a diverse array of germplasm accessions belonging to 12 species of pigeonpea wild relatives. Feeding by H. armigera larvae was significantly lower on the unwashed or water-, methanol-, or hexane-washed pods of Canajus sericeus, C. scarabaeoides, Flemingia bracteata, F. stricta, and Rhynchosia aurea than those of C. acutifolius, C. albicans, C. cajanifolius, C. lineatus, D. ferruginea, P. scariosa, R. bracteata, and the cultivated pigeonpea, C. cajan genotypes, ICPL 87, and ICPL 332, although there were a few exceptions. The methanol-washed pods of wild relatives were less preferred for feeding by the H. armigera larvae than the unwashed pods, but the hexane-washed pods were preferred more than the unwashed pods. The results suggested that methanol extracted the phagostimulants from the pod surface, while hexane removed the antifeedants. The high-performance liquid chromatography (HPLC) finger printing of methanol and hexane pod surface extracts showed qualitative and quantitative differences in compounds present on the pod surface of different wild relatives of pigeonpea. Some of the peaks in HPLC profiles were associated with feeding preference of the third-instar larvae of H. armigera. There was considerable diversity in wild relatives of pigeonpea as revealed by principal component analysis based on HPLC fingerprints of pod surface extracts in methanol and hexane, and H. armigera feeding on the pods. Wild pigeonpea accessions with low amounts of phagostimulants and high amounts of antifeedants may be used for introgression of resistance genes into the cultivated pigeonpea to develop varieties with broad-based resistance to H. armigera. There is considerable diversity among the wild relatives of pigeonpea, and the accessions with resistance to pod borer. These can be used to broaden the basis and increase the levels of resistance to H. armigera.     

Morphological and chemical components of resistance to pod borer, Helicoverpa armigera in wild relatives of pigeonpea

Host plant resistance is an important component for minimizing the losses due to the pod borer, Helicoverpa armigera, which is the most devastating pest of pigeonpea. An understanding of different morphological and biochemical components of resistance is essential for developing strategies to breed for resistance to insect pests. Therefore, we studied the morphological and biochemical components associated with expression of resistance to H. armigera in wild relatives of pigeonpea to identify accessions with a diverse combination of characteristics associated with resistance to this pest. Among the wild relatives, oviposition non-preference was an important component of resistance in Cajanus scarabaeoides, while heavy egg-laying was recorded on C. cajanifolius (ICPW 28) and Rhynchosia bracteata (ICPW 214). Accessions belonging to R. aurea, C. scarabaeoides, C. sericeus, C. acutifolius, and Flemingia bracteata showed high levels of resistance to H. armigera, while C. cajanifolius was as susceptible as the susceptible check, ICPL 87. Glandular trichomes (type A) on the calyxes and pods were associated with susceptibility to H. armigera, while the non-glandular trichomes (trichome type C and D) were associated with resistance to this insect. Expression of resistance to H. armigera was also associated with low amounts of sugars and high amounts of tannins and polyphenols. Accessions of wild relatives of pigeonpea with non-glandular trichomes (type C and D) or low densities of glandular trichomes (type A), and high amounts of polyphenols and tannins may be used in wide hybridization to develop pigeonpea cultivars with resistance to H. armigera. Handling editor: Robert Glinwood     

Next‐generation sequencing for identification of candidate genes for Fusarium wilt and sterility mosaic disease in pigeonpea (Cajanus cajan)

To map resistance genes for Fusarium wilt (FW) and sterility mosaic disease (SMD) in pigeonpea, sequencing‐based bulked segregant analysis (Seq‐BSA) was used. Resistant (R) and susceptible (S) bulks from the extreme recombinant inbred lines of ICPL 20096 × ICPL 332 were sequenced. Subsequently, SNP index was calculated between R‐ and S‐bulks with the help of draft genome sequence and reference‐guided assembly of ICPL 20096 (resistant parent). Seq‐BSA has provided seven candidate SNPs for FW and SMD resistance in pigeonpea. In parallel, four additional genotypes were re‐sequenced and their combined analysis with R‐ and S‐bulks has provided a total of 8362 nonsynonymous (ns) SNPs. Of 8362 nsSNPs, 60 were found within the 2‐Mb flanking regions of seven candidate SNPs identified through Seq‐BSA. Haplotype analysis narrowed down to eight nsSNPs in seven genes. These eight nsSNPs were further validated by re‐sequencing 11 genotypes that are resistant and susceptible to FW and SMD. This analysis revealed association of four candidate nsSNPs in four genes with FW resistance and four candidate nsSNPs in three genes with SMD resistance. Further, In silico protein analysis and expression profiling identified two most promising candidate genes namely C.cajan_01839 for SMD resistance and C.cajan_03203 for FW resistance. Identified candidate genomic regions/SNPs will be useful for genomics‐assisted breeding in pigeonpea.     

木豆凝集素对蚜虫的抗性研究

用盐析法提取10个木豆品种的凝集素,经亲和层析法提纯后添加到全纯人工营养液用于桃蚜饲养,发现所有供试木豆的凝集素对桃蚜都具有不同程度的抗拒性,抗性强弱顺序为：ICP 8863〉ICPL 85010〉ICPL 99066〉ICPL 7035〉ICPH 8〉ICPL 9008〉ICP 6997〉“海南种”〉ICPL 87091〉ICPL 87119。     

Ultrastructural alterations in response to zinc and nickel stress in the root cells of pigeonpea

Ultrastructure of root cortical cells of two genotypes of pigeonpea (Cajanus cajan), namely LRG30 and ICPL87, were grown under different concentrations of zinc and nickel. Growth reduction was found in roots. Electron micrographs of the root cortex cells of the two pigeonpea genotypes exposed to zinc and nickel showed alterations both at the cellular and the organelle level. At the lower concentrations, appearance of unusual deposition of electron dense globules in the vacuoles of the root cortical cells suggests that they may be involved in metal detoxification. Some of the cortical cells showed two nucleoli. The ultrastructural alterations are discussed in relation to the tolerance indices of the two genotypes.     

Cage experiments on Orius tantillus predation of Helicoverpa armigera

The role of Orius tantillus (Motschulsky) (Hemiptera: Anthocoridae) in the predation of H. armigera was studied on both sorghum (Sorghum bicolor L.) and pigeonpea (Cajanus cajan L.), the predominant intercrop of small farmers in Andhra Pradesh, India. Adult Orius tantillus was observed in cages where there were eggs and first-instar larvae of H. armigera on sorghum and pigeonpea. We found that O. tantillus had two diurnal peaks of activity, after sunrise and before sunset. O. tantillus was found preying on first-instar larvae and not on eggs. However, a later immunoassay of O. tantillus collected on sorghum during a peak period of H. armigera oviposition activity showed that predation of eggs did occur under certain conditions. The activity of O. tantillus on sorghum was significantly higher on the flowers than elsewhere but this was not the case on pigeonpea. Therefore O. tantillus was a significantly more efficient predator on sorghum than on pigeonpea. The results indicate that O. tantillus could be an important predator of early stages of an H. armigera infestation, particularly in sorghum.     

Waterlogging induced oxidative stress and antioxidant enzyme activities in pigeon pea

An experiment was conducted with two contrasting pigeon pea (Cajanus cajan L.) genotypes, ICPL 84023 (tolerant) and ICP 7035 (susceptible), to study the physiological and molecular basis of waterlogging tolerance in relation to oxidative stress and antioxidant enzyme activities. Waterlogging resulted in visible yellowing and premature senescence of leaves, and greater decline in relative water content, chlorophyll content, and membrane stability index in ICP 7035 than in ICPL 84023. Superoxide radical and hydrogen peroxide contents increased at day 4 and 6 of waterlogging probably due to activation of NADPH-oxidase. O₂ ^·− production was inhibited, by diphenylene iodonium chloride, a specific inhibitor of NADPH oxidase and expression of NADPH oxidase-mRNA was increased under waterlogging condition in ICPL 84023. ICP 7035 showed higher contents of ROS in control condition and after recovery, however, during waterlogging the O₂ ^·− production was higher in ICPL 84023. Activities of antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase and catalase increased under waterlogging more in ICPL 84023 than in ICP 7035. Cu/Zn-SOD and APX-mRNA expression in 24-h waterlogged plants showed enhanced expression in ICPL 84023 compared to ICP 7035. The cloning and sequencing of APX gene of tolerant and susceptible genotypes yielded cDNAs of 622 and 623 bp, having 95 % homology with each other and 92 % with the corresponding sequences of Vigna unguiculate APX-gene.     

Detached leaf assay to screen for host plant resistance to Helicoverpa armigera

The noctuid Helicoverpa armigera (Hübner) is a major insect pest of chickpea Cicer arietinum L., pigeonpea Cajanus cajan (L.) Millsp., peanut Arachis hypogaea L., and cotton Gossypium spp., and host plant resistance is an important component for managing this pest in different crops. Because of variations in insect density and staggered flowering of the test material, it is difficult to identify cultivars with stable resistance to H. armigera across seasons and locations. To overcome these problems, we standardized the detached leaf assay to screen for resistance to this pest in chickpea, pigeonpea, peanut, and cotton under uniform insect pressure under laboratory conditions. Terminal branch (three to four fully expanded leaves) of chickpea, first fully expanded leaf of cotton, trifoliate of pigeonpea, or quadrifoliate of peanut, embedded in 3% agar-agar in a plastic cup/jar of appropriate size (250-500-ml capacity) infested with 10-20 neonate larvae can be used to screen for resistance to H. armigera. This technique keeps the leaves in a turgid condition for approximately 1 wk. The experiments can be terminated when the larvae have caused > 80% leaf damage in the susceptible check or when differences in leaf feeding between the resistant and susceptible checks are maximum. Detached leaf assay can be used as a rapid screening technique to evaluate germplasm, segregating breeding materials, and mapping populations for resistance to H. armigera in a short span of time with minimal cost, and under uniform insect infestation. It also provides useful information on antibiosis component of resistance to the target insect pest.     

A greenhouse technique to screen pigeonpea for resistance to Heterodera cajani*

Heterodera cajani is an important nematode pest of pigeonpea in India and a simple and reliable greenhouse procedure has been developed to screen pigeonpea genotypes for resistance to it. In pot experiments, white cysts of H. cajani were counted on the roots of the susceptible genotype ICPL 87 at 15, 30 and 45 days after seedling emergence in soils infested with different levels of H. cajani. The seedlings were rated for the number of white cysts per root system on a one (highly resistant, no cysts) to nine (highly susceptible, more than 30 cysts) scale. White cysts were not easy to see on wet roots but were clearly visible on slightly dried roots. Cyst counts and ratings were more uniform when roots of 30 day old seedlings were evaluated than when 15 or 45 day old seedlings were examined. Effects of different H. cajani infestation levels on the ratings were not significant although the use of higher inoculum densities (16 to 27 eggs and juveniles/cm³ soil) was effective in reducing variability. This procedure was used to screen 60 pigeonpea genotypes and all of them were rated seven or nine. Ten accessions of Atylosia spp. and Rhynchosia spp. were rated three.     

Standardization of cage techniques to screen chickpeas for resistance to Helicoverpa armigera (Lepidoptera: Noctuidae) in greenhouse and field conditions

Because of variations in insect populations and staggered flowering of chickpea, Cicer arietinum L., genotypes, it is difficult to compare the genotypic performance across seasons and locations. We standardized a cage technique to screen chickpeas for resistance to Helicoverpa armigera (Hübner). Leaf feeding by the larvae was significantly lower on ICC 506 than on ICCC 37 when the seedlings were infested with 20 neonates per five plants at 15 d after seedling emergence or 10 neonates per three plants at the flowering stage. Maximum differences in pod damage were observed when the plants were infested with six third-instar larvae per three plants in the greenhouse, and with eight larvae per plant under field conditions. Larval weights were significantly lower on ICC 506 than on ICCC 37 across growth stages and infestation levels. At the podding stage, percentage of reduction in grain yield was significantly greater on ICCC 37 and Annigeri than on ICCV 2 and ICC 506. The no-choice test can be used to screen segregating breeding material and mapping populations for resistance to H. armigera. It also provides useful information on antibiosis mechanism of resistance to H. armigera.     

Differential inhibition of Helicoverpa armigera gut proteinases by proteinase inhibitors of pigeonpea (Cajanus cajan) and its wild relatives

The seeds of 36 pigeonpea [Cajanus cajan (L) Millsp.] cultivars, resistant and susceptible to pests and pathogens and 17 of its wild relatives were analysed for inhibitors of trypsin, chymotrypsin, and insect gut proteinases to identify potential inhibitors of insect (Helicoverpa armigera) gut enzymes. Proteinase inhibitors (PIs) of pigeonpea cultivars showed total inhibition of trypsin and chymotrypsin, and moderate inhibition potential towards H. armigera proteinases (HGP). PIs of wild relatives exhibited stronger inhibition of HGP, which was up to 87% by Rhynchosia PIs. Electrophoretic detection of HGPI proteins and inhibition of HGP isoforms by few pigeonpea wild relative PIs supported our enzyme inhibitor assay results. Present results indicate that PIs exhibit wide range of genetic diversity in the wild relatives of pigeonpea whereas pigeonpea cultivars (resistant as well as susceptible to pests and pathogens) are homogeneous. The potent HGPIs identified in this study need further exploration for their use in strengthening pigeonpea defence against H. armigera.     

Studies on inheritance of resistance and allelic relationships for strain 2 of pigeonpea sterility mosaic pathogen

Inheritance of resistance and allelic relationships were studied in three resistant pigeonpea sources for strain 2 of sterility mosaic pathogen. The resistant genotypes (ICP 7035, ICP 7349 and ICP 8850) were crossed with susceptible genotypes (BDN1 and LRG30) to determine the inheritance of resistance. The resistant and susceptible genotypes were also crossed among themselves to obtain information on their allelic relationships. Parents, F₁ and F₂ generations were sown in pots and screened using infector-hedge technique. Observations in parents, F₁ and F₂ generations, indicated dominance of resistance in certain crosses and the dominance of susceptibility in others. Disease reaction appeared to be governed by two independent non-allelic genes, with at least three multiple alleles, at one of the loci.     

Host-plant preference and oviposition responses of the sorghum midge, Stenodiplosis sorghicola (Coquillett) (Dipt., Cecidomyiidae) towards wild relatives of sorghum

Sorghum midge, Stenodiplosis ( Contarinia ) sorghicola (Coquillett) is an important pest of grain sorghum world-wide. Considerable progress has been made in screening and breeding for resistance to sorghum midge. However, some of the sources of resistance have become susceptible to sorghum midge in Kenya, in eastern Africa. Therefore, the wild relatives of Sorghum bicolor were studied as a possible source of new genes conferring resistance to sorghum midge. Midge females did not lay eggs in the spikelets of Sorghum amplum , Sorghum bulbosum , and Sorghum angustum compared to 30% spikelets with eggs in Sorghum halepense when infested with five midge females per panicle under no-choice conditions. However, one egg was laid in S. amplum when infested with 50 midges per panicle. A larger number of midges were attracted to the odours from the panicles of S. halepense than to the panicles of Sorghum stipoideum , Sorghum brachypodum , S. angustum , Sorghum macrospermum , Sorghum nitidium , Sorghum laxiflorum , and S. amplum in dual-choice olfactometer tests. The differences in midge response to the odours from S. halepense and Sorghum intrans were not significant. Under multi-choice conditions, when the females were also allowed a contact with the host, more sorghum midge females were attracted to the panicles of S. bicolor compared with S. amplum , S. angustum , and S. halepense . In another test, numerically more midges responded to the panicles of IS 10712 compared with S. halepense , whereas the differences in midge response to the panicles of ICSV 197 ( S. bicolor ) and S. halepense were not apparent, indicating that S. halepense is as attractive to sorghum midge females as S. bicolor . The wild relatives of sorghum (except S. halepense ) were not preferred for oviposition, and they were also less attractive to the sorghum midge females. Thus, wild relatives of sorghum can prove to be an alternative source of genes for resistance to sorghum midge.     

A screening technique to evaluate pigeonpea for resistance to Rotylenchulus reniformis*

Rotylenchulus reniformis is one of the most important nematode pests of pigeonpea. A simple greenhouse technique has been developed to aid evaluation of pigeonpea genotypes for resistance to R. reniformis. In greenhouse pot experiments, eggsacs of R. reniformis in pigeonpea (cv. ICPL 87) roots were counted by eye and with the aid of a stereoscopic microscope at 15, 30 and 45 days after seedling emergence in soils infested with various numbers of vermiform R. reniformis. Seedlings were rated for the number of eggsacs per root system on a one (no eggsacs) to nine (more than 50 eggsacs) scale. Eggsac ratings were more uniform when roots were evaluated at 30 – 45 days than at 15 days and an inoculum of 15 to 30 individuals/cm³ soil also helped reduce variability. Eggsacs were not easily visible without the aid of a stereoscopic microscope. Of the 14 stains tested, exposure of nematode-infected roots to 0.25% trypan blue for three min was effective in staining the eggsacs blue without staining the roots. Using the stain, the assessment of infestation by R. reniformis was equally accurate with or without the aid of a stereoscopic microscope. Exposure of eggsacs to trypan blue enhanced the emergence of juveniles from the eggsacs.     

Resistance of Collard Green Genotypes to <Emphasis Type="Italic">Bemisia tabaci</Emphasis> Biotype B: Characterization of Antixenosis

Bemisia tabaci (Genn.) biotype B (Hemiptera: Aleyrodidae) is an important pest of vegetable crops, including collard greens Brassica oleracea var. acephala (Brassicaceae). The use of resistant genotypes is an interesting option to reduce insect populations and can be used as an important tool for integrated pest management (IPM). This study evaluated 32 genotypes of collard greens against the attack of silver leaf whitefly, with the aim to characterize antixenosis. Initially, a multiple-choice trial was conducted using all genotypes, in which the adult attractiveness was assessed on two leaves per genotype at 24 and 48 h after infestation. After 48 h, one leaf of each genotype was randomly selected for the determination of the number of eggs per square centimeter. From the results of the multiple-choice trial, 13 genotypes were selected for a no-choice oviposition test, following the same method of the previous test. Colorimetric analyses were also performed to establish possible correlations between leaf color and insect colonization. Genotypes HS-20, OE, and VA were less attractive, demonstrating antixenosis. Genotypes LG, VE, J, MG, MOP, HS-20, VA, and MT had less oviposition in the multiple-choice test, which indicated expression of antixenosis. In the no-choice test, genotypes VE, P1C, CCB, RI-919, H, and J had less oviposition, which also characterized antixenosis. Therefore, genotypes VE and J showed the highest resistance stability because both had less oviposition in both test modalities. Thus, the resistance to B. tabaci biotype B indicates the genotypes HS-20, OE, VA, VE, and J are promising for use in breeding programs to develop resistance to whitefly.     

Leaf volatiles as attractants for neonate Helicoverpa armigera Hbn. (Lep., Noctuidae) larvae

The 1st instar Helicoverpa armigera larvae were bioassayed in the laboratory to study their orientational responses towards leaf volatiles of four leguminous crops: chickpea, Cicer arietinum L.; pigeonpea, Cajanus cajan Millsp.; blackgram, Vigna mungo L.; and cowpea, Vigna unguiculata L. (Walp.). The gram podborer larvae showed positive orientational responses towards leaves of all four test plants. Whole leaves of chickpea, pigeonpea and blackgram were more attractive for gram podborer larvae than cowpea whole leaves. Larval attraction for crushed (damaged) leaves of chickpea, blackgram and cowpea was significantly higher than the attraction for pigeonpea crushed leaves. The orientational responses of gram podborer larvae for crushed leaves of cowpea were significantly higher compared to whole leaves. However, the whole pigeonpea leaves elicited higher orientational responses than the crushed leaves. Maceration was not observed to affect the attractancy of chickpea and blackgram leaves. Further, the leaves were extracted in n-hexane and methanol. It was observed that the crude extracts of all the test leaves elicited positive orientational responses of larvae. In no-choice tests, the orientational preference of the larvae for the hexane extracts of all the test leaves was statistically equal. Similarly, the methanol extracts of leaves of all the test plants also attracted a greater percentage of larvae in no-choice tests. However, under two-choice bioassays, hexane foliage extract of all the test plants elicited higher orientational responses of larvae compared to the methanolic extracts of same leaves. The results of these bioassays clearly indicate that all the test leaves emit kairomones for gram podborer larvae. Moreover, kairomonal components of these leaves are, at least in part, extractable in hexane and methanol, which are higher in hexane than methanol.