Multiple allelism at Er locus for powdery mildew resistance in pea (Pisum sativum L.)

Several sources of powdery mildew resistance in pea have been identified in natural germplasm as well as in landraces and cultivated varieties. Genetic studies revealed that all such cases are recessive mutations in a single gene called Er. Many carriers of the powdery mildew resistance trait differ in their phenotype and expression. This indicated existence of multiple alleles at the locus controlling resistance to powdery mildew. Molecular analysis revealed differences in the nature of changes induced in nature or during mutagenesis. A total of nine molecular mutations have been characterized. Many more alleles of different origin are awaiting similar characterization.