Mapping quantitative trait loci for disease resistance to false smut of rice

Yanqing Han,Fu Huang,Hongyan Sheng,Deqiang Li,Jun Yang,Wenxian Sun

doi:10.1186/s42483-020-00059-6

Abstract

False smut of rice, an important emerging disease caused by Ustilaginoidea virens, greatly reduces grain yield and deteriorates grain quality in many rice-growing regions worldwide. Identification of quantitative trait loci (QTL) conferring false smut resistance will facilitate incorporation of false smut resistance into elite cultivars. In this study, a set of recombinant inbred lines (RILs) derived from a cross of a resistant rice landrace MR183–2 and a high susceptible line 08R2394 were evaluated to map resistance QTLs for false smut. A total of 179 simple sequence repeat (SSR) polymorphic markers were identified for constructing genetic linkage maps. Using a composite interval mapping method, five false smut resistance QTLs were detected on chromosomes 2, 4, 8 and 11 in the RIL population. Among these QTLs, qFsr8–1 within a small region on chromosome 8 represents a major quantitative locus explaining the greatest phenotypic variance. Gene annotation in this major QTL region provides a theoretical basis for cloning of resistance QTLs. The SSR markers genetically linked to qFsr8–1 are valuable for marker-assisted breeding for false smut resistance in rice. In addition, nine QTLs for heading date were detected in this population. Correlation analysis of disease resistance score and heading date indicates that false smut resistance negatively correlates with the growth period length in rice.

Highlights

False smut of rice, which was previously considered a minor disease due to its sporadic occurrence (Cooke 1878), has become one of the most destructive diseases in major rice-growing countries (Fan et al 2015; Sun et al 2020)
A positive correlation between false smut disease severity and heading date in recombinant inbred line (RIL) population Rice plants were grown in disease nurseries with moderate fertilization, regular irrigation and pest management but no disease control
The results indicate that false smut resistance in MR183–2 is under polygenic control and that the RILF7 population is suitable for genetic analysis

Summary

Introduction

False smut of rice, which was previously considered a minor disease due to its sporadic occurrence (Cooke 1878), has become one of the most destructive diseases in major rice-growing countries (Fan et al 2015; Sun et al 2020). The disease has expanded rapidly worldwide, in China and in South Asia, probably because of large-scale planting of high-yield rice varieties and overuse of nitrogenous fertilizers in the past decades (Deng 1989; Zhou et al 2008). False smut occurs in about one third of rice cultivation area in China (Jiang et al 2010; Guo et al 2012). The disease causes a significant yield loss (Yang et al 2012), and reduces grain quality by generating a variety of mycotoxins, such as ustiloxins and ustilaginoidins, which are toxic to both humans and animals (Lai et al 2019; Li et al 2019a)

Results

Discussion

Conclusion