GWAS for low radiation tolerance during grain filling in rice (Oryza sativa L.)

Low radiation during grain filling is one of the main climatic factors limiting rice grain yields. This study aims at identifying genetic regions associated with morphophysiological traits conferring tolerance to low radiation during grain filling. Phenotype-genotype evaluation was carried out on a rice diversity panel using whole genome association studies (GWAS). An Indica panel (300 accessions) was evaluated in the field, on two consecutive years. Grain yield, fertility, 1000 Grain weight, stem-leaf ratio, source:sink relation (SSR)and the number of filled grains per panicle were significantly reduced by low radiation and significantly different across genotypes. A total of 108 QTLs (Quantitative trait loci) with a log 10-4 significance, were associated with 20 variables evaluated in the high and low radiation treatments. For low radiation conditions, two common QTLs were found across years. The haplotype associated to the SSR under low radiation conditions showed an impact on grain yield, percentage of fertility, and number of filled grains per panicle. The OSGRAS19 gene associated in previous studies with grain size (Sink size) and light interception (Source activity) was identified in the LD region of the QTL associated with SSR. Future studies are needed to validate the role of OsGRAS19 in grain yield, SSR and fertility under low radiation conditions.