The genetic associations between yield component traits and bacterial leaf blight resistance in rice (O. sativa L.)

Abstract

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is highly destructive to high-yielding susceptible rice cultivars. In severe epidemics, yield losses up to 75% have been reported. Considerable information on BLB resistant genes is available; however, genetic overlaps between BLB resistant and yield related traits largely remain unclear. Using two sets of backcross introgression inbred lines and one set of recombinant inbred lines, genetic associations between bacterial leaf blight resistance and yield component traits in three Xoo races were analyzed using Single Nucleotide polymorphism (SNP) markers. Fifteen quantitative trait loci conferring BLB resistant and 112 QTLs for yield and yield related traits were detected. Among 15 QTLs conferring bacteria leaf blight resistance, 14 QTLs overlapped with 39 QTLs for yield and yield related traits. The total resistance variation explained by additive QTLs (R²) ranged between 5-76% and epistasis QTLs ranged between 1-26%. Quantitative trait loci (QTLs) with the highest additive effects for BLB resistance were detected at positions os04-17305294 (on chr.4), os05-07310209 (on chr.5), os09-15240130 (on chr.9), os11-28421947 (on chr.11) and os12-25291547(on chr.12). The BLB resistance QTL at position os05-07310209 (on chr.5) overlapped with QTLs for 1000-grain weight, grain number per panicle, days to heading, grain length width ratio and grain yield per plant. The BLB resistance QTL at position os09-15240130 (on chr.9) overlapped with QTLs for grain yield per plant, panicle number, grain width and 1000-grain weight. The BLB resistance QTL at position os12-25291547-(on chr.12) overlapped with QTLs for 1000-grain weight, panicle number, grain yield per plant, filled grain number and grain width. Eleven percent of the 717 plants in this study were resistant to at least two Xoo races and had higher grain yield compared to both recurrent parents. Overlapping regions especially with already cloned genes and epistasis detected in this study offer opportunity to develop rice varieties which combine high yield and resistance to bacteria leaf blight.