Temperature-dependent development of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) and its larval parasitoid, Habrobracon hebetor (Say) (Hymenoptera: Braconidae): implications for species interactions

Habrobracon hebetor (Say) is a parasitoid of various Lepidoptera including Helicoverpa armigera (Hübner), a key pest of different crops and vegetables. The development of both H. armigera and H. hebetor were simultaneously evaluated against a wide range of constant temperatures (10, 15, 17.5, 20, 25, 27.5, 30, 35, 37.5 and 40 °C). Helicoverpa armigera completed its development from egg to adult within a temperature range of 17.5–37.5 °C and H. hebetor completed its life cycle from egg to adult within a temperature range of 15–40 °C. Based on the Ikemoto and Takai model the developmental threshold (T o) and thermal constant (K) to complete the immature stages, of H. armigera were calculated as 11.6 °C and 513.6 DD, respectively, and 13 °C and 148 DD, respectively, for H. hebetor. Analytis/Briere-2 and Analytis/Briere-1 were adjudged the best non-linear models for prediction of phenology of H. armigera and H. hebetor, respectively and enabled estimation of the optimum (T opt) and maximum temperature (T max) for development with values of 34.8, 38.7, 36.3, and 43 °C for host and the parasitoid, respectively. Parasitisation by H. hebetor was maximal at 25 °C but occurred even at 40 °C. This study suggests although high temperature is limiting to insects, our estimates of the upper thermal limits for both species are higher than previously estimated. Some biological control of H. armigera by H. hebetor may persist in tropical areas, even with increasing temperatures due to climate change

Studies on the Variability of Indigenous Mulberry Germplasm for Growth and Yield Traits

Twenty two indigenous mulberry accessions were evaluated for growth and yield traits in three seasons. ANOVA on growth and yield showed significant variation among the accessions for the traits. The interaction between accession and season was highly significant for all traits. The co-efficient of variation was maximum for single leaf weight (17.08%) and minimum for total shoot length (0.08%). The divergence analysis grouped 22 indigenous mulberry accessions into 5 clusters. Maximum accessions were grouped in clusters I & II (8 acc.) followed by cluster V (4 acc.). The diversity among the accessions measured by inter-cluster distance (D2) showed variation. The cluster group indicates that mulberry accessions were distributed in different clusters irrespective of geographical distribution

Characterization of Mulberry Genetic Resources for Multiple Traits

Mulberry plants have wide range of variations in characters in view of its adaptability to cross pollination with no inter-specific reproduction barrier rendering it a heterozygous species. Every plant being different from the other in natural population, this great diversity makes it difficult to gather information and carry out studies on effect of different edaphic factors on the expression of genotypic characters for adjudging the variations. In lieu of this known diversity for posterity, the collection of mulberry genotypes from diverse genetic sources, their conservation, evaluation and consequent documentation is of prime importance. In the present study, 69 mulberry accessions were characterized for morphology, anatomy, and reproductive parameters. Evaluation for propagation, growth and yield characters were also carried out. Based on multiple trait analysis, 14 top performing accessions viz., MI-0879, MI-0882, MI-0908, MI-0931, MI-0907, MI-0940, MI-0881, MI-0941, MI0892, MI-0913, MI-0937, MI-0934, MI-0865, MI-0886 were identified. These accessions could serve as resources for further evaluation aimed at trait-specific crop improvement.</jats:p