Six different rice entries along with susceptible and resistant check varieties were evaluated under glasshouseconditions for different parameters of antixenosis and antibiosis resistance against brownplanthopper(BPH, Nilaparvata lugens Stål). In antixenosis studies, proportion of insects settled on test entries in relationto the susceptible control TN1 was recorded, with average lower proportion of nymphs settled on N22-CCDTM-893 and Ptb 33 in relation to those on TN1. In antibiosis studies adult population, adultlongevity andpopulation build-up were recorded. N22-CC-DTM-893 and Ptb 33 displayed significantly better performanceas compared to other test entries in these parameters studied and did not differ from each other. Theseresults helped in relative quantification of BPH resistance levels in different test entries and N22-CC-DTM-893 show substantial levels of antixenosis and antibiosis effects on BPH and it is considered as new effectivesource of BPH resistance and can be used in resistance breeding after tagging of resistant genes/QTLslinked to brown planthopper resistance with selectable molecular markers.
The temperature has a direct effect on the activity of insect pests and their developmental rate. The increasing temperature could profoundly influence the population dynamics, life cycle, length of reproduction, fecundity, and longevity. In the present study, the impact of different temperatures (32, 33, 34, 35 and 36°C) on the degree days and population fitness of Spodoptera frugiperda (J. E. Smith) was evaluated under artificial conditions. The results showed that for S. frugiperda, an average of 690.38 degree days was required to complete the total life span. The total larval developmental time, pupal duration and adult longevity required 237.38, 184.47 and 228.10 degree days, respectively. The life history data of S. frugiperda were analysed by using TWOSEX-MSChart. An increase in temperature reduced the developmental time of S. frugiperda at age x and stage j. The highest reproductive value (vx) of S. frugiperda was obtained at 34°C (600 individuals per day) and was found to be reduced at a further increase in temperature of 35°C (260 individuals per day) and 36°C (120 individuals per day). These results signify the improved fitness of S. frugiperda with increasing temperature levels, and the degree days help to predict the development pattern of S. frugiperda based on heat accumulation.
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