Identification and association of ISSR markers for thermal stress in polyvoltine silkworm <Emphasis Type="Italic">Bombyx mori</Emphasis> |
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Authors: | P P Srivastava P K Kar A K Awasthi S Raje Urs |
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Institution: | (1) Seribiotech Research Laboratory, Central Silk Board, Carmelram Post, Kodathi Bangalore 560 035, Karnataka, India;(2) Central Sericultural Germplasm Resources Center, Central Silk Board, P. B. 44, Thally Road, Hosur, Tamil Nadu, 635109, India |
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Abstract: | Evaluation of genetic resources is an essential prerequisite for their effective utilization. In India, the tropical climate
prevails in most of the sericultural belts, where temperature goes beyond the ambient during summer, adversely affecting the
silkworm rearing. Although polyvoltine silkworms are poor in silk content, they are mostly tolerant to tropical conditions
and diseases. With an aim to identify potential silkworm races/breeds specific to thermotolerance for their effective utilization
in breeding programme, 15 selected polyvoltine silkworm races were studied for their thermotolerance behaviour. Their genomic
DNA samples were analyzed for ISSR-PCR using 15 selected primers. The UPGMA analysis based on Nei and Li algorithm has clustered
the 15 silkworm races into five groups and one isolate. ALSCAL multidimensional scaling has not only supported the information
generated by the dendrogram, but it has made the genetic distance among races more clear and substantiating their status in
terms of thermal stress where pupation rate was taken as indicator. Further, discriminant function analysis (DFA) was done
with three groups of silkworms classified for thermal stress viz. susceptible, moderately tolerant and tolerant. The canonical
correlation value was estimated to be 0.987 (Wilk’s λ= 0.004; χ2 = 36.044, p < 0.05). DFA clearly discriminated the above three groups. Beta statistics with t value and its significance for the markers identified through stepwise multiple regression analysis (MRA) revealed a total
of five bands (8071300, 8083000, 8084000, 8344000, and 8343000) showing correlation with pupation rate after thermal treatment. Out of them, marker 808 3000 showed maximum and highly significant
correlation (r = 0.757, p < 0.001, t = 4.182) with pupation rate among the silkworm races. The identified putative markers are being used to develop DNA marker
to be used in evolving thermo-tolerant silkworm breeds using marker-assisted selection programme.
The text was submitted by the authors in English. |
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