Abstract
Powdery mildew is one of the most widespread diseases of wheat. The development and deployment of resistant varieties are one of the most economical and effective methods to manage this disease. Our previous study showed that the gene(s) at 2Mb in Chinese Spring (CS)-Aegilops biuncialis 2Mb disomic addition line TA7733 conferred a high level of resistance to powdery mildew of wheat. In this study, resistance spectrum of TA7733 was assayed by using 15 Blumeria graminis f. sp. tritici (Bgt) isolates prevalent in different regions of China. The result indicated that TA7733 was highly resistant to all tested Bgt isolates and the gene(s) on chromosome 2Mb conferred broad-spectrum resistance to powdery mildew. In order to characterize mechanism of powdery mildew resistance by identifying candidates R-genes derived from Ae. biuncialis chromosome 2Mb and develop 2Mb-specific molecular markers, we performed RNA-seq analysis on TA7733 and CS. In total we identified 7,278 unigenes that showed specific expression in TA7733 pre and post Bgt-infection when compared to CS. Of these 7,278 unigenes, 295 were annotated as putative resistance (R) genes. Comparatively analysis of R-gene sequences from TA7733 and CS and integration CS Ref Seq v1.0 were used to develop R-gene specific primers. Of 295 R-genes we identified 53 R-genes were specific to 2Mb and could be involved in powdery mildew resistance. Functional annotation of majority of the 53 R-genes encoded nucleotide binding leucine rich repeat (NLR) protein. The broad-spectrum resistance to powdery mildew in TA7733 and availability of 2Mb-derived putative candidate R-gene specific molecular markers identified in this study will lay foundations for transferring powdery mildew resistance from 2Mb to common wheat by inducing CS-Ae. biuncialis homoeologous recombination. Our study also provides useful candidates for further isolation and cloning of powdery mildew resistance gene(s) from Ae. biuncialis chromosome 2Mb.
Highlights
Common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD), one of the most widely planted crops in the world provides 20% of the calories and 25% of its protein consumed by human [1,2]
We identified that Chinese Spring (CS)-Ae. biuncialis 2Mb disomic addition line TA7733 conferred high resistance to powdery mildew compared with its recipient parent CS [26]
We report the assays of a broad-spectrum resistance gene(s) on chromosome 2Mb derived from Ae. biuncialis, discovery of 2Mb-specific candidate genes of powdery mildew resistance, and development of molecular markers of 2Mb specificity based on transcriptome sequencing of CS-Ae. biuncialis 2Mb disomic addition line TA7733
Summary
Wheat yields and quality are severely threatened by various diseases, such as rusts, Fusarium head blight (FHB) and powdery mildew. Wheat powdery mildew, caused by Blumeria graminis f. Certain agronomic practices to increase yields, such as popularization of high planting density, high inputs of irrigation and fertilization have accelerated the spread and severity of powdery mildew [5,6]. Though spraying fungicides can reduce the damage caused by this disease to some extent, it can result in side effects such as drug resistant of powdery mildew fungus, environment pollution, and high production inputs [7]. Breeding disease-resistant varieties is currently recognized as one of the most effective and economical ways to control powdery mildew
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