Abstract
Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is one of the most devastating diseases in rice production areas, especially in humid tropical and subtropical zones throughout Asia and worldwide. A genome-wide association study (GWAS) analysis conducted on a collection of 236 diverse rice accessions, mainly indica varieties, identified 12 quantitative trait loci (QTLs) on chromosomes 1, 2, 3, 4, 5, 8, 9 and 11, conferring resistance to five representative isolates of Thai Xoc. Of these, five QTLs conferred resistance to more than one Xoc isolates. Two QTLs, qBLS5.1 and qBLS2.3, were considered promising QTLs for broad-spectrum resistance to BLS. The xa5 gene was proposed as a potential candidate gene for qBLS5.1 and three genes, encoding pectinesterase inhibitor (OsPEI), eukaryotic zinc-binding protein (OsRAR1), and NDP epimerase function, were proposed as candidate genes for qBLS2.3. Results from this study provide an insight into the potential QTLs and candidate genes for BLS resistance in rice. The recessive xa5 gene is suggested as a potential candidate for strong influence on broad-spectrum resistance and as a focal target in rice breeding programs for BLS resistance.
Highlights
Rice is the staple food of more than half the world population
Based on the Bacterial leaf streak (BLS) disease scores calculated using unweighted pair-groups with arithmetic mean (UPGMA), the five Xanthomonas oryzae pv. oryzicola (Xoc) isolates were divided into three groups: Group 1 consisted of 3BR7-7; Group 2 consisted of
Bacterial leaf streak (BLS) resistance in rice has been reported as a polygenic trait
Summary
Rice production is threatened by several factors including abiotic stresses, such as drought, soil salinity and flooding, and biotic stresses, such as insect pests and diseases caused by pathogens. Oryzicola (Xoc) is one of the most devastating diseases in rice production areas, Plants 2020, 9, 1673; doi:10.3390/plants9121673 www.mdpi.com/journal/plants. 10–20% have been recorded for BLS depending on rice varieties and environmental conditions [2]. Asia and Africa where its intensity and frequency of effect is growing. A key sustainability goal for controlling BLS is the development of resistant rice varieties, especially as the majority of rice cultivars in Asia and Africa are susceptible to the disease [3]. It is necessary to identify resistance genes/quantitative trait loci (QTLs) and the functional background of BLS resistance in rice breeding programs for rice variety improvement
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