Abstract
Rice false smut (RFS), an emerging major fungal disease worldwide caused by Ustilaginoidea virens, affects rice grain quality and yield. RFS cause 2.8-49% global yield loss depending upon disease severity and cultivars. In India, the yield loss due to RFS ranged from 2 to 75%. Identification of the genes or quantitative trait loci (QTLs) governing disease resistance would be of utmost importance towards mitigating the economic losses incurred due to RFS. Here, we report mapping of RFS resistance QTLs from a resistant breeding line RYT2668. The mapping population was evaluated for RFS resistance under the field condition in three cropping seasons 2013, 2015, and 2016. A positive correlation among infected panicle/plant, total smut ball/panicle, and disease score was observed in the years 2013, 2015, and the mean data. A total of seven QTLs were mapped on rice chromosomes 2, 4, 5, 7, and 9 using 2326 single nucleotide polymorphism markers. Of these, two QTLs, qRFSr5.3 and qRFSr7.1a, were associated with the infected panicle per plant, one QTL qRFsr9.1 with total smut ball per panicle, and four QTLs qRFSr2.2, qRFSr4.3, qRFSr5.4, and qRFSr7.1b with disease score. Among them, a novel QTL qRFSr9.1 on chromosome 9 exhibits the largest phenotypic effect. The prediction of putative candidate genes within the qRFSr9.1 revealed four nucleotide-binding sites-leucine-rich repeat (NBS-LRR) domain-containing disease resistance proteins. In summary, our findings mark the hotspot region of rice chromosomes carrying genes/QTLs for resistance to the RFS disease.
Highlights
resistance/tolerance to different stress (Rice) false smut (RFS) is an economically important grain disease caused by the fungus Ustilaginoidea virens (Cooke) Takahashi
The outcome of the present study illustrated promising QTLs associated with resistance to the rice false smut disease along with disease resistance genes which could be effectively utilized in rice breeding programs after further validation
QTLs associated with resistance to false smut on chromosome 2 and 4 were detected in recombinant inbred line (RIL) population derived from MR183-2/08R2394 cross
Summary
Rice false smut (RFS) is an economically important grain disease caused by the fungus Ustilaginoidea virens (Cooke) Takahashi. It is threatening rice productivity and impairs grain quality in most of the rice-growing countries, every year (Fan et al 2016; Qiu et al 2019). RFS was considered a minor disease due to sporadic occurrence (Zhang et al 2014; Jiehua et al 2019) It is emerged as a major constraint to the global rice production due to the adaptation of susceptible high yielding rice cultivars and hybrids, heavy application of nitrogenous fertilizers, and climate change (Rush et al 2000; Ladhalakshmi et al 2012). RFS is gaining attention among pathologists, breeders, and farmers
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