12/17/2023 0 Comments Bacterial blight of endive![]() ![]() Furthermore, with the emergence of new and more virulent Xoo strains, single resistance genes can be overcome in a short period (McDonald and Linde 2002). Some resistance genes linked to undesirable agricultural traits cannot be directly applied in breeding, such as xa13, which improves BB resistance but reduces pollen fertility and seed setting rate (Li et al. ![]() Because of either their lower level of resistance or their narrow spectrum of resistance, only a few genes (such as Xa4, Xa21, Xa23 and Xa39) with broad-spectrum resistance have been widely deployed in breeding programs so far (Hu et al. Among the 45 major resistance genes, 11 genes ( Xa1, Xa3/ Xa26, Xa4, xa5, Xa10, xa13, Xa21, Xa23, xa25, Xa27 and xa41(t)) have been cloned and characterized ( ). Most BB resistance genes were detected through bi-parental population (F 2 or recombinant inbred line populations) studies except for Xa43(t), which was discovered in a multi-parent advanced generation inter-cross (MAGIC) population through genome-wide association study (GWAS) (Kim and Reinke 2019). To date, 45 major resistance genes (denoted Xa1 – xa-45(t)) that confer resistance to BB have been identified, and are distributed on all chromosomes except chromosomes 9 and 10 (Chukwu et al. ![]() Because of the adaptation between rice and Xoo, it is necessary to identify major resistance ( R) genes and quantitative trait loci (QTL) that will support the development of new resistant varieties. Breeding resistant cultivars is considered the most effective and eco-friendly strategy for managing this disease (McDonald and Linde 2002). As it is a vascular disease, chemical measures for controlling BB are less effective than for some other diseases (Niño-Liu et al. oryzae ( Xoo), is one of the most destructive bacterial diseases worldwide, in both tropical and temperate regions (Mew 1978). Rice bacterial blight (BB), caused by Xanthomonas oryzae pv. Rice ( Oryza sativa L.), an important cereal crop that supports more than 50% of the world population, suffers many biotic and abiotic stresses that lead to serious damage to crop yield and food safety (Oerke 2006). Our findings provide valuable information for the genetic improvement of BB resistance and application of germplasm resources in rice breeding programs. In addition, the Hap2 allele of LOC_Os11g46250 underlying qC5–11.1 was validated as positively regulating resistance against strain C5. Linear regression analysis showed a dependence of BB lesion length on the number of favorable alleles, suggesting that pyramiding QTL using marker-assisted selection would be an effective approach for improving resistance. The other three QTL were putative novel loci associated with BB resistance. Among them, eight resistance loci, which were narrowed down to relatively small genomic intervals, coincided with previously reported QTL or R genes, e.g. Using the 3 K RG 4.8mio filtered SNP Dataset, a total of 11 QTL associated with BB resistance on chromosomes 4, 5, 11 and 12 were identified through a genome-wide association study (GWAS). ResultsīB resistance of a diverse panel of 340 accessions from the 3000 Rice Genomes Project (3 K RGP) was evaluated by artificial inoculation with four representative Xoo strains, namely Z173 (C4), GD1358 (C5), V from China and PXO339 (P9a) from Philippines. To deal with ever-evolving Xoo, it is necessary to identify novel R genes and resistance quantitative trait loci (QTL). However, because of specific interaction of each R gene with the product of the corresponding pathogen avirulence or effector gene, new pathogen strains that can overcome the deployed resistance often emerge rapidly. Breeding and deployment of resistant cultivars carrying major resistance ( R) genes has been the most effective approach for BB management. ![]() oryzae ( Xoo) is one of the most devastating bacterial diseases of rice in temperate and tropical regions. Bacterial blight (BB), caused by Xanthomonas oryzae pv. ![]()
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