Introgression of drought tolerance into popular rice variety using wild ancestor derived Chromosomal Segment Substitution Lines through marker assisted selection

Abstract

newline Wild species of rice are reservoir of many useful genes. These genes have played important role in imparting tolerance to various biotic and abiotic stresses. However, most of these genes remain untapped till date because it is often difficult to transfer these genes into cultivated rice. Chromosome Segment Substitution Lines (CSSLs) and backcross inbred lines (BILs) are powerful tools for identifying these naturally occurring, favourable alleles/genes in un-adapted germplasm. The identification of new alleles of genes from wild relatives of rice and transfer into cultivated rice would improve productivity under stress condition. In the present study, two interspecific libraries of Chromosome Segment Substitution Lines (CSSLs) were evaluated in four seasons includes dry-wet of 2013-2014 under both drought and control conditions. The stress was imposed in rainout shelter at panicle initiation stage and soil water tension was maintained at -50 kPa at 30cm soil depth.The phenotypic screening of 80 CSSLs led to the identification of three promising drought tolerant lines, MER20, RUF16 and RUF44 on the basis of yield performance and relative yield reduction under reproductive stage drought stress. The MER20 line was backcrossed with popular Indian rice varieties namely, Swarna-Sub1 and IR64-Sub1 to introgress wild chromosome segments responsible for reproductive stage drought tolerance. In backcrossing, advance barcode data tracking system was used for wild introgressions. In F1 and BC1F1 back-cross generations, foreground screening was carried out by using designed SSR and Sub1A gene specific markers. The monitoring of recurrent parent genome recovery was facilitated by the use of the Cornell 6K and 7K Infinium RICE SNP arrays for foreground and background selection in BC2F1, BC3F1 and BC3F2 generations. The Cornell 6-7K RICE Infinium array platform by Illumina Genome Studio and PERL pipeline script program was used for allele calling and SNP analysis.