Marker-Assisted Development and Evaluation of Near-Isogenic Lines for Broad-Spectrum Powdery Mildew Resistance Gene Pm2b Introgressed into Different Genetic Backgrounds of Wheat.

Hongxing Xu,Yanwei Cao,Liping Song,Yunfeng Xu,Pengtao Ma,Lihui Li,Diaoguo An,Feifei Ma

doi:10.3389/fpls.2017.01322

Abstract

At present, most of released wheat cultivars or breeding lines in China are susceptible to powdery mildew (Pm) (caused by Blumeria graminis f. sp. tritici, Bgt), so there is an urgent need to rapidly transfer effective and broad-spectrum Pm resistance genes into elite cultivars/lines. Near-isogenic lines (NILs) with short target gene region are very important in molecular breeding and map-based cloning and can be developed by combining marker-assisted selection and conventional phenotypic identification. However, no Pm gene NILs were reported by using this method in the previous studies. A new broad-spectrum dominant resistance gene Pm2b, derived from the Chinese wheat breeding line KM2939, conferred high resistance to Pm at both the seedling and adult stages. In this study, with the aid of forward and background selection (FS and BS) using molecular markers, the Pm2b gene was introgressed into three elite susceptible commercial cultivars Shimai 15, Shixin 828, and Kenong 199 through the back-crossing procedure. With the appropriate backcrossing generations, selected population sizes and marker number for BS, the homozygous resistant BC3F2:3 NILs of Pm2b gene in the three genetic backgrounds with the highest recipient genome composition of about 99%, confirmed by simple sequence repeat markers and 660K single nucleotide polymorphic array, were developed and evaluated for the powdery mildew resistance and agronomic traits. The different resistance and similar or improved agronomic performance between Pm2b NILs and their corresponding recurrent parents indicated their potential value in the marker-assisted breeding of the Pm2b gene. Moreover, the development of four flanked diagnostic markers (CFD81, BWM25, BWM20, and BWM21) of the Pm2 gene can effectively assist the forward selection and accelerate the transfer and use of this resistance gene.

Highlights

Common wheat (Triticum aestivum L.) is one of the most important staple food crop in China and the yield of wheat can seriously affect food safety
During the transfer of Pm2b into the recurrent parents, the resistant donor parent KM2939, recurrent parents Shimai 15 (SM15), Shixin 828 (SX828), and Kenong 199 (KN199), and all their derived generation plants were tested against B. graminis f. sp. tritici (Bgt) isolate E09, which is avirulent to Pm2b gene at the seedling stage and their inheritance of resistance was analyzed, and only the resistant target progeny plants after forward ground selection (FS) and background selection (BS) were selected for further backcrossing or selfing (Table 1)
During the backcross transfer of Pm2b gene into the genetic backgrounds of SM15, SX828 and KN199, most of the resistant progeny plants were genotyped with the four Pm2b diagnostic markers CFD81, BWM20, BWM21, and BWM25

Summary

Introduction

Common wheat (Triticum aestivum L.) is one of the most important staple food crop in China and the yield of wheat can seriously affect food safety. Of the several wheat production constraints, diseases are the most important stress, which can cause significant yield losses. Among the various wheat foliar diseases, Pm, caused by B. graminis f. Tritici (Bgt), is one of the most prevalent diseases occurring throughout the wheat growing regions of the world, which caused severe yield damage (Bennett, 1984; Sun et al, 2015). In China, most of the wheat cultivars released in recent years are susceptible to Pm and account for 83.1% of the total acreage (Li et al, 2011). The use of resistant cultivars and resistance genes is the most efficient, economical and environmentally safe approach to curb this disease and reduce yield losses (Wang et al, 2015)

Methods

Results

Discussion

Conclusion