Study on effects of qDTY3.1 contributing yield under drought in Ranjit x Apo derived F4 populations
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Date
2019-07
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AAU, Jorhat
Abstract
Tolerance to low land drought stress in rice is under polygenic control and numerous quantitative trait loci(QTLs) have been identified, out of which a major QTL for yield under drought (qDTY3.1) derived from ‘Apo’ has been detected with significant additive effects. Intermittent drought profoundly affect the yield of ‘Ranjit’, a predominant high yielding variety for sali season in Assam. Therefore, a study was conducted to improve drought tolerance in ‘Ranjit’ and to understand the genetics of qDTY3.1 in the F4 lines of Ranjit x Apo. The screening of F4 populations for qDTY3.1 using the nearest marker RM520 revealed 45 Ranjit type, 69 Apo type and 66 with heterozygous alleles, respectively. Although indicated a slight bias towards Apo type allele yet the Chi square test showed that the data were in good fit, and were not significantly deviated from the expected values. Further, screening with markers far from the qDTY3.1 revealed a total of 35 Ranjit/Apo recombinants having qDTY3.1 intact, indicating suitability of these lines for advanced breeding materials. To check the nucleotide diversity and informative sites within and near the QTL region, sequencing analysis was performed in coding sequences (CDS) for some of the proteins expressed under drought/abiotic stress. Out of the CDSs sequenced, two CDSs within the QTL region did not show any polymorphism. The one CDS for NAC family detected with one non synonymous substitution in which the Apo type (with qDTY3.1) was encoded with ‘Proline’ and Ranjit type with ‘Arginine’, warrants detail study to validate the data along with inclusion of more regions to be sequenced. The effect of the qDTY3.1 allele was also estimated. Mean values showed the better yield performance of ‘Apo’ types than the ‘Ranjit’ types in drought condition. Although symptomatically the leaf rolling scores of ‘Ranjit’ is comparable to ‘Apo’, however the yield penalty for both these types was evident. Significant correlation was observed for panicle length and number of grains, effective booting tiller and tiller number, effective booting tiller and grain yield in ‘Ranjit’ and panicle length and number of grains, spikelet fertility with number of grains in ‘Apo’ under drought stress. The effects of qDTY3.1 in Ranjit x Apo imparting drought tolerance in F4 lines was observed. However, the role of other minor effect QTLs with the change of other background may not be ruled out. The study will help in generating promising breeding lines for low land drought tolerance in Assam rice.
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