MAPPING AND DISSECTION OF GENETIC EFFECTS INTO QTLs FOR GRAIN YIELD UNDER DROUGHT IN ELITE RICE VARIETY OF ASSAM
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Date
2017-01
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AAU, Jorhat
Abstract
Two traditional drought tolerant cultivars were crossed with Ranjit in the present study in order to identify QTLs and improved lines for various yield traits under drought stress. The allelic distribution of 45 SSR markers associated with major grain yield QTLs under drought stress were studied in 115 ahu rice cultivars. The cluster analysis distinguished cultivars into 2 major clusters. The drought tolerant cultivars (ARC10372 and Banglami) were grouped with tolerant check (Nagina22) and high yielding cultivars were grouped with susceptible check (Ranjit).
A total of 110 polymorphic SSR markers were identified across the parents, Banglami and Ranjit. These SSR markers were used for segregation analysis in 180 F2 plants. Among 110 polymorphic SSR markers, 88 fitted the expected Mendelian segregation, whereas 22 (20.0%) significantly deviated from it (P<0.01). Only 89 SSR markers could be assigned to 12 linkage groups covering a total of 1628.7 cM of the rice genome. The F2:4 population consisting of 2460 F4 plants were evaluated for various yield traits under two hydrological conditions viz., irrigated control (non stress) and drought stress created in rainout shelter. The drought stress was imposed from panicle initiation to panicle emergence period (reproductive stage). A total of seven QTLs, viz., qNOT2.1 (number of tillers), qEBT6.2 (effective booting tillers), qPNL1.1, qPNL6.1 (panicle length), qNGP12.1 (number of grains per panicle), qNCP6.1 (number of chaff per panicle) and qGYP7.1 (grain yield), were identified under drought stress whereas, four QTLs viz., qEBT6.1 (effective booting tillers), qNCP4.1 (number of chaff per panicle), qSFP6.1 (spikelet fertility) and qGYP9.1 (grain yield), were identified under irrigated conditions.
The cultivar ARC10372 was crossed with Ranjit and 180 F2 plants were raised. Among these, only 36 F2 plants carrying tolerant parent allele for the SSR markers RM431 and RM11943 associated with the major grain yield QTL (qDTY1.1) were selfed to raise F2:3 population. Only 10 F3 plants were selected on the basis of yield and root traits. These were selfed to raise F4 population. The F2:4 population consisting of 217 F4 plants were evaluated for various yield traits under drought stress and irrigated conditions. Two F2:4 lines (B-42, B-106) from ‘Banglami x Ranjit’ and one F2:4 line (A-78) from ‘ARC10372 x Ranjit’ were selected on the basis of improved yield and grain quality traits under drought stress. The selected plants may be used for the development of drought tolerant rice variety.
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