Assessing host specialization of Erysiphe pisi on garden pea germplasm through genotypic and phenotypic characterization

Abstract

Erysiphe pisi, Erysiphe baeumleri and Erysiphe trifolii cause powdery mildew disease in garden pea. So far, three genes er1, er2 and Er3 imparting resistance against E. pisi have been reported in pea. The E. pisi isolate used in this study, Ep01 (GenBank Accession No. KM096758) was identified using the internal transcribed spacer sequence of the ribosomal DNA region. Testing of garden pea germplasm lines and cultivars against E. pisi pathogen under green house conditions revealed varying levels of resistance. The resistant control lines JI2302, JI2480 and P660-4 with reported resistance genes er1, er2 and Er3 respectively showed significant levels of resistance to the E. pisi isolate, Ep01 while the susceptible control lines, Messire and Lincoln showed significant levels of susceptibility. Out of the forty six pea lines (including the control lines) tested, three lines were found to be highly resistant, three lines were resistant, eighteen lines were moderately resistant, twelve were moderately susceptible, six were susceptible and four lines were highly susceptible. The molecular screening using SCAR markers for er1 gene, Sc-OPO-18₁₂₀₀, Sc-OPE-16₁₆₀₀, ScOPX 04₈₈₀ and ScOPD 10₆₅₀ did not lead to identification of er1 gene due to lack of expected amplification with Sc-OPE-16₁₆₀₀ and Sc-OPO-18₁₂₀₀ while no polymorphism was observed between resistant and susceptible controls with ScOPX 04₈₈₀ and ScOPD 10₆₅₀. The SCAR marker for er2 gene, ScX17_1400 led to identification of twenty four lines that may be carrying er2 gene while SCAR markers for Er3 gene, SCW4₆₃₇ and SCAB1₈₇₄, helped identify four lines as potential sources of Er3 gene.