Abstract
Oryza meyeriana is highly resistant to rice bacterial blight (BB) and this resistance trait has been transferred to cultivated rice (O. sativa) using asymmetric somatic hybridization. However, no resistance genes have yet been cloned. In the present study, a progeny of the somatic hybridization with high BB resistance was crossed with a rice cultivar with high BB susceptibility to develop an F2 population. Using bulked segregant analysis (BSA), 17 polymorphic markers that were linked to rice BB resistance were obtained through scanning a total of 186 simple sequence repeats (SSR) and sequence-tagged site (STS) markers, evenly distributed on 12 chromosomes. A genetic linkage map was then constructed based on the 17 linkage markers and the F2 segregating population, which was followed by mapping for quantitative trait loci (QTLs) for BB resistance. Three QTLs were identified on chromosomes 1, 3 and 5, respectively, and the alleles of the resistant parent at any of the QTLs increased BB resistance. All of the three QTLs had a strong effect on resistance, explaining about 21.5%, 12.3% and 39.2% of the resistance variance, respectively. These QTLs were different from the loci of the BB resistance genes that have been identified in previous studies. The QTLs mapped in this work will facilitate the isolation of novel BB resistance genes and their utilization in rice resistance breeding.
Highlights
Xanthomonas oryzae pv. oryzae (Xoo) causes rice bacterial blight (BB), one of the most destructive bacterial diseases of rice worldwide
Because ASH1 was derived from the japonica cultivar Dalixiang, an indica cultivar IR24 was selected as another parent for Quantitative Trait Loci (QTL) mapping in order to produce marker polymorphism between the parents
O. meyeriana is highly resistant to rice BB disease, but no resistance genes have yet been cloned in this wild rice, which has delayed the utilization of this important material in rice breeding programs
Summary
Xanthomonas oryzae pv. oryzae (Xoo) causes rice bacterial blight (BB), one of the most destructive bacterial diseases of rice worldwide. Oryzae (Xoo) causes rice bacterial blight (BB), one of the most destructive bacterial diseases of rice worldwide. It is responsible for severe yield losses to global rice production, generally in the range of 20% to 30%, and as high as 50% in years when the disease is prevalent [1]. Most of them have been tagged with DNA markers and eight of them (Xa1, Xa3/Xa26, Xa5, Xa10, Xa13, Xa21, Xa25, Xa27) have been cloned successfully using a map-based cloning strategy [3,4,5,6,7,8,9,10] Some of these resistance genes have been widely used in rice breeding for BB resistance and many useful cultivars have been released in Asian countries
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