Resistance to powdery mildew in the pea cultivar Xucai 1 is conferred by the gene er1

Abstract

Powdery mildew, caused by Erysiphe pisi D.C., is a major constraint to pea production worldwide. The pea cultivar Xucai 1 has shown high resistance to E. pisi under greenhouse and field conditions. The objectives of this study were to identify and characterize genes conferring resistance to powdery mildew in Xucai 1. Three crosses, Qizhen 76 × Xucai 1, Bawan 6 × Xucai 1, and Xucai 1 × Bawan 6, were made to generate populations for genetic analysis. The resistance to E. pisi and segregation ratios in the F1, F2, and F2:3 populations suggested a single recessive gene conferring the resistance of Xucai 1. Bulked segregant analysis was used to map the resistance gene using two F2 populations. The resistance gene was close to markers AD60 and c5DNAmet on linkage group VI with genetic distances of 9.9 cM and 15.4 cM in the Xucai 1 × Bawan 6 F2 population and 8.7 cM and 8.1 cM in the Qizhen 76 × Xucai 1 F2 population, respectively, suggesting that the resistance gene was an er1 allele. This hypothesis was confirmed by comparison of the cDNA sequences of the PsMLO1 gene between the parents and the PsMLO1 wild type. Three distinct types of transcripts in Xucai 1, characterized by a 129-bp deletion and 155- and 220-bp insertions, were detected, consistent with the structure of the er1-2 allele. We concluded that resistance in Xucai 1 was conferred by er1-2 and that its linked markers will be useful in pea breeding programs.

Keywords

• Erysiphe pisi
• er1-2
• Pea
• Powdery mildew
• Xucai 1