Abstract
BackgroundTomato leaf mold is a common disease in tomato cultivation. This disease is caused by Cladosporium fulvum, which has many physiological races and differentiates rapidly. Cf genes confer resistance to C. fulvum, and the C. fulvum-tomato pathosystem is a model for the study of gene-for-gene interactions. Plants carrying the Cf-19 gene show effective resistance to C. fulvum in the field, and can be used in breeding and resistance mechanism studies as new resistant materials. In this study, we used F2 bulk specific-locus amplified fragment sequencing (SLAF-seq) and parental resequencing methods to locate and characterize the Cf-19 gene.ResultsA total of 4108 Diff_markers and three association regions were found in association analysis. A 2.14-Mb region containing seven Cf-type genes was identified in further analysis based on data from SLAF-seq and parental resequencing. Two candidate genes, Solyc01g006550.2.1 and Solyc01g005870.1.1, were screened out by quantitative real-time PCR (qRT-PCR) analysis. Sequence analysis showed that Solyc01g006550.2.1 (an allelic locus of Cf-0) in CGN18423 was a novel homologue of the Cladosporium resistance gene Cf-9 (Hcr9s) in the Cf-4/9 locus. The marker P7, which cosegregated with the resistant trait, was developed based on sequence mutation of the Solyc01g006550.2.1 locus in CGN18423.ConclusionsThe Cf-19 gene was mapped to the short arm of chromosome 1. The candidate genes Solyc01g006550.2.1 and Solyc01g005870.1.1 showed related amino acid sequence structures and expression patterns. Solyc01g006550.2.1 had a close evolutionary relationship with the functional Hcr9 members Cf-4 and Cf-9, and was very different from non-functional members. The results from this study will facilitate the breeding of cultivars carrying the Cf-19 gene and provide a basis for further gene cloning, resistance gene evolution and plant resistance mechanism studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0737-0) contains supplementary material, which is available to authorized users.
Highlights
Tomato leaf mold is a common disease in tomato cultivation
Disease severity ratings and genetic analysis of the Cf-19 gene CGN18423 and F1 plants were resistant to the C. fulvum race 1.2.3.4, while Moneymaker plants were susceptible
The Cf-19 gene was mapped to the short arm of chromosome 1 Cf-19 was assigned to the long arm of chromosome 2 in 1980 [11], while this gene was mapped at the short arm of chromosome 1 in this study
Summary
Tomato leaf mold is a common disease in tomato cultivation This disease is caused by Cladosporium fulvum, which has many physiological races and differentiates rapidly. Plants carrying the Cf-19 gene show effective resistance to C. fulvum in the field, and can be used in breeding and resistance mechanism studies as new resistant materials. Tomato leaf mold disease, caused by the biotrophic fungus Cladosporium fulvum, is a serious disease of Solanum lycopersicum (tomato) [1]. This disease can reduce both fruit yield and quality, and sometimes even kill tomato plants. A race that has evolved to overcome the resistance genes Cf2, Cf-4, Cf-5, Cf-9, and Cf-11 was reported by Lindhout et al [5]. The number of Cf genes that can be used in breeding is decreasing, making it necessary to identify new resistance genes and breed them into tomato cultivars
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