Research Article

Response of Scirpophaga incertulas Walker to different temperature regimes

Free access

The yellow stem borer (YSB) Scirpophaga incertulas (Walker) (Pyralidae: Lepidoptera) is one of the major pests in rice producing areas and accounts for 27 to 34 per cent loss in the crop yield. Climate change especially temperature increase will affect the insect physiology, behavior and development. An investigation was undertaken to study the effect of temperature on Scirpophaga incertulas (Walker) by constructing the stage specific life table to understand its behaviour in the future climate. Experiments were carried out at four different temperature regimes viz., 28.0°C, 30.0°C, 32.0°C and 34.0°C. The results revealed that the survival fraction of a particular stage reduced with increasing temperatures. The calculated apparent mortality indicated that the percentage of insect died, increased with increasing temperatures. The results showed that the Mortality Survival Ratio (MSR) was observed to be increasing with increasing temperatures for all the stages. The value of IM was observed to be decreasing with increasing temperatures. The generation mortality of YSB was increasing with increase in temperatures for all the stages. The experiments revealed that the insects which happened to live under higher temperature would die faster and most of their energy is spent for reproduction rather than for living long time.

Genetic interaction of physiological traits in Eucalyptus species

Free access

Paramathma M

Published on: 30 Mar 2020 | DOI: | Pages: 5-8

Six species of Eucalyptus viz., E. alba, E. camaldulensis, E. microtheca, E. tereticornis, E. polycarpa and E. torelliana, were subjected to full diallel mating. The cross between E. polycarpa and E. torelliana was characterised by post-fertilization abortion. An evaluation of the remaining four parents and 12 hybrids revealed that characters like leaf temperature and diffusive resistance were free from epistatic interaction. For the characters  PAR, non-allelic interaction was obserrved. Leaf temperature was shown to be under the influence of predominantly dominant gene action. Predominance of additive gene action  was evident in respect of diffusive resistance and transpiration rate. The gene distribution among the parents was observed to be unequal with greater frequencies of dominant allels for PAR and diffusive resistance. The number of genes that control the characters was one for leaf temperature, PAR and transpiration rate and  two for diffusive resistance. Narrow sense heritability was low  for all the attributes.