The spotted stem borer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) is being successfully reared on artiWcial diets for screening programmes. Besides quality characteristics of the diet, rearing density and adult nutrition have signiWcant implications on the successful mass multiplication of lepidopterans. The performance of C. partellus moths was assessed on diVerent adult diets (water and sugar solution) and compared with unfed adults. Further, three pairing densities, viz. 2, 5 and 8 pairs/oviposition jar (1177.5 cm 3 ) were compared for their eVect on C. partellus longevity and fecundity. In another experiment, diVerent larval densities (100, 150 and 200 neonate larvae/diet jar) were evaluated for their eVect on the larval survival. Water-fed moths (both males and females) lived longer (7.32 and 7.26 days, respectively) and showed higher fecundity (307.17 eggs) than the sugar-fed or unfed moths. The latter, however, showed better egg hatchability (76.55%) than the water-or sugar-fed moths (60.45 and 50.59%, respectively). The longevity (5.67 days) and fecundity (258.46 eggs) were signiWcantly greater at pairing density of 2 pairs/jar. The larval survival was higher (58.50%) at rearing density of 100 larvae/jar. The neonate larval release into diet jars was compared with conventional egg release and both modes were no diVerent with respect to larval survival.
Three transgenic maize hybrids, viz. Prabal YG, Hishell YG and Double YG, producing Bacillus thuringiensis (Bt) Cry1Ab protein (event Mon 810), were evaluated under field and laboratory conditions for their resistance to spotted stemborer Chilo partellus (Swinhoe). The Bt maize hybrids suffered less damage than their non-Bt iso-hybrids with respect to per cent plant infestation (0.0 -0.6), leaf injury rating (1.0 -1.1) and per cent stem tunnelling. These hybrids also resulted in significantly higher larval mortality (79.4 -100.0%) in laboratory bioassays. The toxin protein produced in leaves was equally effective against neonates and 15-day-old larvae. Neonate larvae consumed less leaf area (5.0 -13.8%) in case of Bt hybrids than their non-Bt iso-hybrids.
The maize (Zea mays L.) cultivar 'Makki Safed 1' (MSI) with susceptibility to brown stripe downy mildew (BSDM) caused by Sclerophthora rayssiae var. zeae PAYAK & RENFRO, was subjected to two cycles of mass selection and one cycle of full-sib family selection. Selection was carried out primarily for BSDM resistance. The mass selection was practised under artificial epiphytotic conditions in a disease nursery. Full-sib progenies and performance trials on MS1 and its improved versions were grown in diseased and disease free environments.Mass selection resulted in a significant improvement for resistance to BSDM. A cycle of full-sib selection resulted in an additional improvement for resistance to the disease. The disease rating of the improved version was 1.5 against 4.5 for the original population (scale: 1, highly resistant to 5, highly susceptible). The yield of the improved populations of MS1 was significantly greater than that of MS1 in the disease nursery. In disease free experiments, the improved populations showed almost no yield advantage over MSl. There were also no significant differences between the original population and the improved population after three selection cycles for ear length, ear girth, number of kernel rows per ear, number of kernels per row, 1 OOOkernel weight, plant height, ear height and days to silk.
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