Identification of QTLs for resistance to sclerotinia stem rot and BnaC.IGMT5.a as a candidate gene of the major resistant QTL SRC6 in Brassica napus.

Jian Wu,Lixia Li,Sheng Liu,Chuchuan Fan,Yongming Zhou,Xinping Luo,Guangqin Cai,Jiangying Tu,Lipeng Zhou,Jinfa Zhang

doi:10.1371/journal.pone.0067740

Jian Wu, Lixia Li + Show 8 more

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https://doi.org/10.1371/journal.pone.0067740

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Journal: PloS one	Publication Date: Jul 2, 2013
Citations: 126	License type: CC BY 4.0

Affiliation: Huazhong Agricultural University

Abstract

Stem rot caused by Sclerotinia sclerotiorum in many important dicotyledonous crops, including oilseed rape (Brassica napus), is one of the most devastating fungal diseases and imposes huge yield loss each year worldwide. Currently, breeding for Sclerotinia resistance in B. napus, as in other crops, can only rely on germplasms with quantitative resistance genes. Thus, the identification of quantitative trait locus (QTL) for S. sclerotiorum resistance/tolerance in this crop holds immediate promise for the genetic improvement of the disease resistance. In this study, ten QTLs for stem resistance (SR) at the mature plant stage and three QTLs for leaf resistance (LR) at the seedling stage in multiple environments were mapped on nine linkage groups (LGs) of a whole genome map for B. napus constructed with SSR markers. Two major QTLs, LRA9 on LG A9 and SRC6 on LG C6, were repeatedly detected across all environments and explained 8.54–15.86% and 29.01%–32.61% of the phenotypic variations, respectively. Genotypes containing resistant SRC6 or LRA9 allele showed a significant reduction in disease lesion after pathogen infection. Comparative mapping with Arabidopsis and data mining from previous gene profiling experiments identified that the Arabidopsis homologous gene of IGMT5 (At1g76790) was related to the SRC6 locus. Four copies of the IGMT5 gene in B. napus were isolated through homologous cloning, among which, only BnaC.IGMT5.a showed a polymorphism between parental lines and can be associated with the SRC6. Furthermore, two parental lines exhibited a differential expression pattern of the BnaC.IGMT5.a gene in responding to pathogen inoculation. Thus, our data suggested that BnaC.IGMT5.a was very likely a candidate gene of this major resistance QTL.

Highlights

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic and nonhost-specific fungal pathogen that infects more than 400 plant species, including several important oil crops such as oilseed rape, soybean and sunflower [1,2]
The segregation patterns for both stem resistance (SR) and leaf resistance (LR) in the mapping population implied that resistance to Sclerotinia infections was a quantitative trait with additive gene effects
Our study indicated that the resistance to S. sclerotiorum in B. napus is a complex quantitative trait and is controlled by minor polygenes, which is consistent with previous reports [7,8,11,12,13,14,15]

Summary

Introduction

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic and nonhost-specific fungal pathogen that infects more than 400 plant species, including several important oil crops such as oilseed rape, soybean and sunflower [1,2]. Stem rot in oilseed rape (Brassica napus) caused by S. sclerotiorum is one of the most devastating diseases for the important crop worldwide. It imposes, for example, 10–20% of yield losses every year, and up to 80% in severely infected fields in China [3], one of the largest rapeseed producers in the world Sclerotia geminate under favorable conditions through either formation of apothecia that release ascospores, or of mycelia that generate hyphae This life cycle pattern, together with its wide host range, makes Sclerotinia stem rot in oilseed rape difficult to manage through cultural practices. The molecular mechanism of the interaction of pathogenic infection and resistance reaction in host plants is poorly understood [5]

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