DISCOVERY OF QTLs FOR DROUGHT TOLERANCE TRAITS USING A BIPARENTAL MAPPING POPULATION OF MULBERRY SEGREGATING FOR ROOT AND WATER USE EFFICIENCY (WUE)
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Date
2015-10-26
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Soil moisture stress is one of the main factors limiting the mulberry productivity
in India. Maintaining leaf water relations by better root system and maintenance of
superior metabolism for positive carbon gain can enhance drought adaptability. These
traits are quantitatively inherited and therefore requires a forward molecular breeding
approach to pyramid them. Towards identifying QTL for these complex traits, mapping
population segregating for WUE and root traits was extensively characterized for
phenotypic and molecular diversity. Significant genetic variability was noticed in various
physiological and biometric traits among the progeny. Root weight varied between
23.66 and 250.50 g p-1 while Δ13C, a surrogate for WUE varied between 15.65 and
21.28‰. The traits segregated in a 1:1 pattern conforming to the pseudo test cross in out
beeding perennials. The F1 progeny MPR-89, MPR-120, MPR-53, MPR-68 and MPR-
123 which segregated into low Δ13C category also had high TDM, LA and R/S ratio and
appeared to be the most suitable genotypes for water limited conditions. A total of 751
SSR markers were screened which revealed 453 markers polymorphic between parents.
A linkage map with 14 linkage groups (LGs) with 134 linked markers had a map length
of 4263.5 cM. The distance between two linked markers varied from 5.0 to 49.8 cM with
an average distance of 31.80 cM. QTL analysis was performed using composite interval
mapping (CIM) using QTL CARTOGRAPHER (version 2.5). The CIM identified 23, 11
and 9 QTLs controlling various traits respectively on first, second and pooled data.
Further, validation of these QTLs and saturation of these regions would help the breeder
to exploit root traits, WUE and associated traits for genetic improvement of mulberry
varieties and also to evolve new varieties adapted to water limited conditions.
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