Interactions among insect-resistant soybean genotypes extracts with populations of Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae) susceptible and resistant to its nucleopolyhedrovirus

Anticarsia gemmatalis nucleopolyhedrovirus (AgMNPV) is being used in Brazil as a biological insecticide. Host plant resistance of soybean to insects is been searched for and some authors have mentioned the interference of plant chemistry in virus efficiency. Interactions among soybean extracts of genotypes used as a source of resistance (PI 274454 and PI 227687) with different AgMNPV concentrations in populations of A. geatalis susceptible (S) and resistant (R) to the virus were studied at laboratory condition. Higher mortality was observed when larvae fed on diets with extracts of the soybean genotypes compared with those fed on a plain diet (control). The mean lethal concentration (LC50) was reduced about 10 ties in the S-population fed on diets containing PI 274454 extracts and different concentrations of AgMNPV, compared to control diet. Additive effect was predominantly observed when larvae fed on diets with extracts of soybean genotypes (PI 274454 and PI 227687) and AgMNPV for both larval populations. The pupal weight was negatively influenced by the extracts incorporated to the diets compared to control, for both larval populations, notably for R-population. The results suggest that, in general, leaf extracts of soybean resistant genotype did not cause any harmful effect on virus efficiency.

O nucleopoliedrovirus de Anticarsia gemmatalis (AgMNPV) tem sido utilizado como um inseticida biológico no Brasil. A resistência de plantas de soja a insetos tem sido pesquisada e alguns autores têm mencionado a interferência de substâncias químicas de plantas sobre a eficiência de vírus. As interações entre extratos de genótipos de soja utilizados como fontes de resistência (PI 274454 e PI 227687) com diferentes concentrações do AgMNPV em populações de A. gemmatalis suscetível (S) e resistente (R) ao vírus foram estudadas em condições de laboratório. Mortalidades elevadas foram observadas quando as larvas foram alimentadas com dietas contendo extratos dos genótipos de soja, em relação às larvas alimentadas com dieta artificial sem a presença de extratos (testemunha). A concentração letal média (CL50) foi reduzida em aproximadamente 10 vezes, na população s alimentada com dieta contendo extratos da PI 274454 e diferentes concentrações do AgMNPV, comparada à dieta testemunha. Um efeito aditivo foi predominantemente observado quando as larvas se alimentaram em dietas com extratos dos genótipos de soja (PI 274454 e PI 227687) e o AgMNPV, para ambas as populações (S e R). O peso de pupa foi negativamente influenciado pela dieta contendo os extratos em relação à dieta testemunha, para ambas as populações, com destaque para a população R. Os resultados indicam que, no geral, os extratos de folhas de genótipos de soja resistentes não causam efeitos negativos na eficiência do vírus.

Establishment of two new cell lines from Bombyx mori (L.) (Lepidoptera: Bombycidae) & their susceptibility to baculoviruses.

BACKGROUND & OBJECTIVES: Lepidopteran cell cultures and baculovirus expression vector systems are becoming popular due to their potential applications in biotechnology especially for the expression of foreign proteins. Efforts were made to develop new, indigenous, cell lines from Bombyx mori larvae and pupae. METHODS: Eight to ten B. mori larvae and 10-12 pupae were surface sterilized, dissected and ovaries were removed aseptically. Ovaries were chopped finely, washed and suspended in growth medium. When the cells formed monolayers, they were subcultured and experiments were carried out. RESULTS: Two new cell lines from larval and pupal ovaries of B. mori were established in Grace's insect tissue culture medium supplemented with 20 per cent FBS (foetal bovine serum). The larval cell line consisted predominantly of epithelial-like cells (98.31%), whereas the pupal cell line had a mixed cell population of epithelial-like (71.8%) and fibroblast-like cells (27.8%). Karyology indicated a typical lepidopteran pattern in both the cell lines and had chromosome numbers ranging from 35 to 150 and 60 to 180 for larval and pupal ovaries respectively. Four-fold increase in cell number was observed in these cell lines in 7 days. Both the cell lines were found susceptible to B. mori multiple nucleopolyhedrovirus and Autographa californica multiple nucleopolyhedrovirus, but not to Helicoverpa armigera single nucleopolyhedrovirus and Spodoptera litura multiple nucleopolyhedrovirus. INTERPRETATION & CONCLUSION: These well characterized cell lines may be of immense application in biotechnology and medicine for the production of biologically active recombinant proteins to use in vaccine studies as well as in therapeutic applications.

Enhancing the efficacy and persistency of Spodoptera litura (Fab.) nuclear polyhedrosis virus using UV irradiation protectants.

To enhance the field persistency of S. litura nuclear polyhedrosis virus (SLNPV), three chemicals viz. cupric ammonium nitrate, tinopal and cupric sulphate were tried as protectants (0.01 mg/ml) against natural sunlight (UV) irradiation. On exposure for 8 hr and subsequent bioassaying (diet surface treatment), it was found that cupric sulphate protected the polyhedrosis inclusion bodies (PIBs), recording 95.56% mortality which was statistically at par with unexposed PIBs recording 97.78% mortality.