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Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) is a serious threat to grain legumes, particularly pigeonpea. Varietal resistance in pigeonpea against M. vitrata and knowledge about the seasonal abundance of the pest are crucial to manage it efficiently. Nine pigeonpea genotypes (AL 1932, AL 2000, AL 1747, MN 1, AL 2102, PADT16, AL 201, PAU 881 and AL 882) were screened against M. vitrata under field conditions for two years (Kharif 2020 and 2021). M. vitrata larvae were first observed during the 36th SMW (Standard Meteorological Week) in the early flowering genotypes (MN 1 and PADT 16). The pest population gradually reached its peak during the 40th SMW on all the genotypes and gradually declined thereafter, with no pest population after the 43rd SMW. Mean larval population, web counts and per cent pod damage were the lowest in genotype AL 1747 and the highest in genotype MN 1. The number of larvae and webs per plant had a non-significant correlation with all the weather parameters. Principal component analysis (PCA) was used and the variables were transformed into principal components (PC) to explain the nature and extent of the relationships among different variables. During kharif 2020, PC1 and PC2 between M. vitrata larvae, webs and weather parameters captured 53.0 and 34.9 per cent of the variability in data, respectively whereas during kharif 2021, PC1 and PC2 captured 49.0 and 35.8 per cent of the variability in data, respectively. Our results show that genotype AL 1747 consistently performed better under M. vitrata infestation and therefore, it can be used in future breeding programmes to develop resistant varieties against M. vitrata. [ABSTRACT FROM AUTHOR]

Pigeonpea (Cajanus cajan) production can be affected by the spotted pod borer (Maruca vitrata). Here, we identified biochemical changes in plant parts of pigeonpea after M. vitrata infestation. Two pigeonpea genotypes (AL 1747, moderately resistant; and MN 1, susceptible) were compared for glyoxalase and non-glyoxalase enzyme systems responsible for methylglyoxal (MG) detoxification, γ-glutamylcysteine synthetase (γ-GCS), glutathione-S-transferase (GST) and glutathione content in leaves, flowers and pods under control and insect-infested conditions. MN 1 had major damage due to M. vitrata infestation compared to AL 1747. Lower accumulation of MG in AL 1747 was due to higher activities of enzymes of GSH-dependent (glyoxylase I, glyoxylase II), GSH-independent (glyoxalase III) pathway, and enzyme of non-glyoxalase pathway (methylglyoxal reductase, MGR), which convert MG to lactate. Decreased glyoxylase enzymes and MGR activities inMN1 resulted in higher accumulation of MG. Higher lactate dehydrogenase (LDH) activity in AL 1747 indicates utilisation of MG detoxification pathway. Higher glutathione content in AL 1747 genotype might be responsible for efficient working of MG detoxification pathway under insect infestation. Higher activity of γ-GCS in AL 1747 maintains the glutathione pool, necessary for the functioning of glyoxylase pathway to carry out the detoxification of MG. Higher activities of GST and GPX in AL 1747 might be responsible for detoxification of toxic products that accumulates following insect infestation, and elevated activities of glyoxylase and non-glyoxylase enzyme systems in AL 1747 after infestation might be responsible for reducing reactive cabanoyl stress. Our investigation will help the future development of resistant cultivars. [ABSTRACT FROM AUTHOR]

Multi-location field experiments were conducted in five districts of Punjab (India) during kharif (May-October) 2019 cropping season to evaluate the effect of four doses (1250, 1875, 2500 and 3125 ml ha-1) of home-made neem (Azadirachta indica A. Juss) extract against pod sucking bug, Clavigralla gibbosa, as well as their effect on the grain yield of pigeonpea. The incidence of the pod bug (seven days after spray) and the seed damage were found to be significantly lower in the home-made neem extract treatments as compared with the untreated control (41.99% and 34.25% reduction over the control, respectively). However, none of the home-made neem extract doses was as effective as the synthetic insecticide (deltamethrin) in terms of pest population and seed damage reduction. However, amongst the botanical insecticide treatments, home-made neem extract @ 3125 ml ha-1 excelled in overall performance. This technology is cheap, safe, environment friendly and easy for adoption by limited resource farmers. [ABSTRACT FROM AUTHOR]

The present study was carried out to study the relative seasonal abundance and damage potential of spotted pod borer, Maruca vitrata Fab. in pigeonpea for three consecutive seasons. The highest number of Maruca larval population as well as webbings per plant was recorded during 40th Standard Meteorological Week (SMW) during the three seasons, coinciding with the peak flowering stage of pigeonpea. The pod damage due to M. vitrata during different years (2015 to 2017) ranged from 19.50–24.50%, indicating the key pest status of this pod borer species in the region. Non-significant correlation was observed between the weather parameters and larval population of M. vitrata as well as number of webbings per plant. Out of three weather parameters analyzed, maximum temperature was found to exert significant influence on Maruca incidence. [ABSTRACT FROM AUTHOR]

Development of transgenic crops with stable gene inheritance and expression over generations is important for effective deployment at field level. In present study, T1 plants of pigeonpea cultivars AL15 and AL201 were evaluated for the presence and expression of cry1Ab gene and protection against Maruca pod borer. Cry1Ab protein in transgene carrying T1 plants ranged from 0.72 to 0.87 µg g-1 flower tissue. In vitro insect bioassay demonstrated up to 49.17 and 53.80% loss in larval body weight after four days of infesting T1 transgenic flowers and pods, respectively. Further, no adults emerged from the pupae of larvae fed on transgenic plants 15-537 and 201-344. All T2 progeny plants of 15-537 exhibited cry1Ab presence; likewise, all T3 progeny plants derived from homozygous T2 plant (15-537-5) displayed presence and expression of transgene, thus establishing stable transgene integration in T1 plants, followed by its stable inheritance and expression in T2 and T3 generations. [ABSTRACT FROM AUTHOR]

The potential of enzyme inhibitors against infestation of insects serves as attractive strategy for the management of devastating pests. In an effort to identify some effective and eco-friendly inhibitors of a damaging pest, Helicoverpa armigera, iron and zinc were found to be potent inhibitors of H. armigera α-amylase, which is an important digestive enzyme required for its survival. This observation motivated us to determine the status of iron and zinc in different pigeon pea genotypes in response to H. armigera herbivory. In general, there was significant decline in zinc content in developing seeds and pod wall after herbivory. However, zinc content was significantly higher in moderately resistant genotypes than moderately susceptible genotypes in infested developing seeds. Significant accumulation of iron was also observed in developing seeds of moderately resistant and intermediate genotypes after the pod borer attack. Higher content of zinc in pod wall of moderately resistant genotypes could determine their resistibility status against H. armigera herbivory. [ABSTRACT FROM AUTHOR]

Amylase inhibitors serve as attractive candidates of defense mechanisms against insect attack. Therefore, the impediment of Helicoverpa armigera digestion can be the effective way of controlling this pest population. Nitrite was found to be a potent mixed non-competitive competitive inhibitor of partially purified α-amylase of H. armigera gut. This observation impelled us to determine the response of nitrite and nitrate reductase (NR) towards H. armigera infestation in nine pigeonpea genotypes (four moderately resistant, three intermediate and two moderately susceptible). The significant upregulation of NR in moderately resistant genotypes after pod borer infestation suggested NR as one of the factors that determine their resistance status against insect attack. The pod borer attack caused greater reduction of nitrate and significant accumulation of nitrite in moderately resistant genotypes. The activity of nitrite reductase (NiR) was also enhanced more in moderately resistant genotypes than moderately susceptible genotypes on account of H. armigera herbivory. Expression of resistance to H. armigera was further revealed when significant negative association between NR, NiR, nitrite and percent pod damage was observed. This is the first report that suggests nitrite to be a potent inhibitor of H. armigera α-amylase and also the involvement of nitrite and NR in providing resistance against H. armigera herbivory. [ABSTRACT FROM AUTHOR]