Molecular Cytogenetic Identification of a New Wheat-Rye 6R Chromosome Disomic Addition Line with Powdery Mildew Resistance.

Diaoguo An,Fangpu Han,Lihui Li,Qiaoling Luo,Xiaotian Zhang,Hongxia Zhang,Yilin Zhou,Qi Zheng,Yunfeng Xu,Hongxing Xu,Pengtao Ma,Dragan Perovic

doi:10.1371/journal.pone.0134534

Abstract

Rye (Secale cereale L.) possesses many valuable genes that can be used for improving disease resistance, yield and environment adaptation of wheat (Triticum aestivum L.). However, the documented resistance stocks derived from rye is faced severe challenge due to the variation of virulent isolates in the pathogen populations. Therefore, it is necessary to develop desirable germplasm and search for novel resistance gene sources against constantly accumulated variation of the virulent isolates. In the present study, a new wheat-rye line designated as WR49-1 was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. Using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), mc-GISH (multicolor GISH) and EST (expressed sequence tag)-based marker analysis, WR49-1 was proved to be a new wheat-rye 6R disomic addition line. As expected, WR49-1 showed high levels of resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 19 of 23 Bgt isolates tested at the seedling stage. According to its reaction pattern to different Bgt isolates, WR49-1 may possess new resistance gene(s) for powdery mildew, which differed from the documented powdery mildew gene, including Pm20 on chromosome arm 6RL of rye. Additionally, WR49-1 was cytologically stable, had improved agronomic characteristics and therefore could serve as an important bridge for wheat breeding and chromosome engineering.

Highlights

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the major serious diseases threatening the production of wheat (Triticum aestivum L.) in many regions around the world
There were several disease resistant genes located on rye chromosome arms, for instance, the powdery mildew resistance (Pm) gene Pm8, stripe rust (Puccinia striiformis Westend. f. sp. tritici) resistance gene Yr9, stem rust (P. graminis Pers. f. sp. tritici) resistance gene Sr31 and leaf rust (P. triticina Eriks. f. sp. tritici) resistance gene Lr26, all derived from chromosome arm 1RS of Petkus rye; Pm17 came from 1RS of Insave rye; Pm7 derived from 2RL of Rosen rye and Pm20 from 6RL of Prolific rye [5]
The result indicated that WR49-1 had 44 chromosomes, among which one pair of intact chromosomes displayed bright-green hybridization signals and demonstrated that it came from the rye parent German White, while the other 42 chromosomes showed only the blue signals, indicating that they were derived from the wheat parent Xiaoyan 6 (Fig 1a and 1c), since genomic in situ hybridization (GISH) detection showed that no rye chromosomes or chromosome segment existed in Xiaoyan 6 (Fig 2)

Summary

Introduction

Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is one of the major serious diseases threatening the production of wheat (Triticum aestivum L.) in many regions around the world. Powdery mildew was prevalent in the main wheat producing regions of China and resulted in serious yield loss [2]. A continuing challenge is faced to discover new gene sources for powdery mildew resistance and incorporate these genes into wheat breeding programs. There were several disease resistant genes located on rye chromosome arms, for instance, the powdery mildew resistance (Pm) gene Pm8, stripe rust To meet the challenge of the rapid loss of resistance, it is essential to continually develop new resistance germplasm and identify novel resistance gene sources from other rye genotypes against new virulent isolates

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