Abstract
ABSTRACTA cross was made between MR219 (high yielding but submergence intolerant) and Swarna-Sub1 (submergence tolerant) to produce submergence-tolerant rice variety using the marker-assisted backcrossing (MABC) method to protect the farmers of low-lying land from flash floods during rain. Knowledge of yield and yield contributing factors plays a vital role in the selection process of a variety. This experim ent was designed to determine the genetic diversity among recently produced different lines of BC2F3 population and also to compare all the lines with MR219 to find the best one. Agronomical, yield and yield contributing data were taken, while genotypic and phenotypic coefficients, variance components and heritability were estimated. Introgression of the target gene, Sub1, was done using tightly linked marker, and also background recovery was measured using simple sequence repeat (SSR) markers in different generations. The observed recurrent parent genome (RPG) recovery of BC2F2 generation was 95.37%, which indicates high-level similarity between the recurrent parent (MR219) and the resulting lines. Thirty newly developed lines of BC2F3 population, resulting backcross of MR219 and Swarna-Sub1, were planted with four replications following randomised complete block design (RCBD). Newly developed lines were grouped into four clusters based on traits with UPGMA dendrogram and cluster analysis to select the 10 best plants. This study will help the future researchers to select the best plants of a breeding programme after introgression of a gene considering phenotype performances to develop new varieties.
Highlights
Flash floods can result in yield losses of rice up to 100%, depending upon different factors of submergence-prone ecosystems
Out of 340 plants, 156 were found to be heterozygous (H) for marker RM8300 linked with Sub1 and 184 of them were found to be fixed with the recipient allele (A), where no plant was shown as fixed with donor allele (B) in BC1F1 generation
Submergence tolerant-resistant lines were developed by crossing MR219 with a submergence-tolerant donor Swarna-Sub1 through marker-assisted backcrossing (MABC) using MR219 as a recurrent
Summary
Flash floods can result in yield losses of rice up to 100%, depending upon different factors of submergence-prone ecosystems. Traditional varieties adapted to these submergence-prone environments are, low yielding due to their poor tillering ability, long droopy leaves, susceptibility to lodging and poor grain quality. Improved varieties that can combine high yield attributes with submergence tolerance are needed. Molecular markers not linked to Sub, polymorphic between two parents and covered all chromosomes including Chromosome 9 (carrier of Sub1) were used for the selection of background to determine the recovery of recipient genome. Spaced SSR markers were selected for every chromosome. In case of BC1F1 and BC2F1 generation, 66 polymorphic markers were used for background survey. Additional 19 SSR markers were tested in BC2F2 generation for estimating the amount of recipient genome (Supplementary material).
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