Genetic Similarity between Cotton Leafroll Dwarf Virus and Chickpea Stunt Disease Associated Virus in India

The cotton leafroll dwarf virus (CLRDV) is one of the most devastating pathogens of cotton. This malady, known as cotton blue disease, is widespread in South America where it causes huge crop losses. Recently the disease has been reported from India. We noticed occurrence of cotton blue disease and chickpea stunt disease in adjoining cotton and chickpea fields and got interested in knowing if these two viral diseases have some association. By genetic studies, we have shown here that CLRDV is very close to chickpea stunt disease associated virus (CpSDaV). We were successful in transmitting the CLRDV from cotton to chickpea. Our studies indicate that CpSDaV and CLRDV in India are possibly two different strains of the same virus. These findings would be helpful in managing these serious diseases by altering the cropping patterns

Overexpression of Cytochrome P450 CYP6B7 Mediated Pyrethroid Resistance in Indian Strains of the Cotton Bollworm, Helicoverpa Armigera (Hübner)

The role of cytochrome P450 monooxygenase in pyrethroid resistance was studied in different strains of the cotton bollworm, Helicoverpa armigera, from India. Filed collected strains of Nagpur and Delhi were compared to the laboratory reared population. The results showed a high resistance to deltamethrin, α-cypermethrin, and β-cyfluthrin. The results also showed that this resistance could be reduced by using piperonyl butoxide (PBO). The Nagpur and Delhi strains were found to have a 2.40 and 1.79 fold higher monooxygenase activity compared to a susceptible strain. A strong, positive correlation between monooxygenase activity and pyrethroid resistance was observed (r = 0.86 - 0.98). The relative expression of the housekeeping gene, EF-1α, and three P450 genes, was studied in the 5th instar larval midgut of the three strains. Out of the three P450 genes examined, expression of CYP6B7 mRNA was not detected in the midgut of the susceptible strain though it was highly expressed in the resistant strains. The midgut of the Nagpur strain had a 2.60 fold overexpression of CYP6B7 mRNA compared to the moderately resistant, Delhi strain. The mRNA of CYP4G8 and CYP6B2 were not overexpressed in either the Nagpur or Delhi strain. The results indicated that the elevated cytochrome P450 monooxygenase activity is associated with pyrethroid resistance in Indian strains of H. armigera, and CYP6B7 could be the P450 form responsible for pyrethroid resistance

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Not AvailableA new pest, mealybug which was hitherto not familiar earlier started destroying cotton crops caused economic damage, reducing yields up to 40-50% in affected fields since 2006. Several parts of Gujarat which are located on the border of Pakistan which had recent history of mealybugs infestation was severely affected. Mealybug infestation were recorded (Dhara Jothi et al., 2008) in 2006 on G. hirsutum in all the nine cotton-growing states of India, Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, Maharashtra, Tamil Nadu, Andhra Pradesh and Karnataka. Severe economic damage to G. hirsutum was reported in 2007 (Dhara Jothi et al., 2008) in four major cotton-growing districts (Bathinda, Muktsar, Faridkot and Ferozepur) of Punjab, two districts (Hisar and Sirsa) of Haryana, and low to moderate damage in parts of Maharashtra, Tamil Nadu and Andhra Pradesh. According to Goswami (2007), nearly 2000 acres of cotton crops were destroyed by the mealybug by mid-July and over 100 acres of mealybug-infested Bt cotton was uprooted in Raike-Kalan village in Bathinda. By the end of the Kharif season (June–October), the total damage in 2007 was estimated to range from US$400,000 to 500,000 in north India alone.NAI

The comparison of species diversity and abundance of insect natural enemies in the domesticated species of cotton using the yellow pan trap method

Abstract India is the world’s largest cotton producer and the only country that grows all four cultivated cotton species. There have been very few studies on the diversity and abundance of natural enemies of cotton insect pests in these cultivated cotton species. Therefore, the current study (2016–2018) was conducted to assess the diversity and abundance of natural enemies that cultivated cotton species harbour. Phule Dhanwantari, Suraj, Suvin, RCH-2, and DCH-32 were the five genotypes used in the study, each with a distinct genetic background. Using the adiv 2.0.1 and vegan R packages, we identified significant differences in natural enemies in terms of species diversity, richness, evenness, and abundance. Analysis of Similarity (ANOSIM) and Non-metric Multidimensional Scaling (NMDS) indicated substantial differences in the natural enemy community structure among the examined genotypes. A total of 17,279 natural enemies were collected and identified across genotypes from seven predatory families and five parasitoid families. The percentage share of these natural enemy families across genotypes and years, in descending order, is Coccinellidae (28.23%) < Tachinidae (19.23%) < Braconidae (12.68%) < Chrysopidae (11.65%) < Chalcididae (9.41%) < Aphelinidae (6.33%) < Pentatomidae (3.29%) < Ichneumonidae (2.37%) < Syrphidae (2.33%) < Vespidae (1.81%) < Asilidae (1.79%) < Geocoridae (0.89%). Coccinellidae, Tachinidae, Braconidae, Chrysopidae, Chalcididae, and Aphelinidae are the six major families that account for more than 85% of all recorded natural enemies. These six families have a higher percentage share in Phule Dhanwantary (90%) compared to the other genotypes. The conservation and better utilization of these natural enemies are crucial for the ecological and safe management of insect pests in the cotton ecosystem