Abstract

Globally powdery mildew (PM) is one of the major diseases of the pea caused by Erysiphe pisi. Besides, two other species viz. Erysiphe trifolii and Erysiphe baeumleri have also been identified to infect the pea plant. To date, three resistant genes, namely er1, er2 and Er3 located on linkage groups VI, III and IV respectively were identified. Studies have shown the er1 gene to be a Pisum sativum Mildew resistance Locus ‘O’ homologue and subsequent analysis has identified eleven alleles namely er1–1 to er1–11. Despite reports mentioning the breakdown of er1 gene-mediated PM resistance by E. pisi and E. trifolii, it is still the most widely deployed gene in PM resistance breeding programmes across the world. Several linked DNA markers have been reported in different mapping populations with varying linkage distances and effectiveness, which were used by breeders to develop PM-resistant pea cultivars through marker assisted selection. This review summarizes the genetics of PM resistance and its mechanism, allelic variations of the er gene, marker linkage and future strategies to exploit this information for targeted PM resistance breeding in Pisum.

Highlights

  • The pea (Pisum sativum L.; 2n = 2x = 14) is one of the most important cool season legumes consumed both as a vegetable and as a pulse

  • In the case of E. pisi, the er2 genotype (JI2480) showed complete resistance at 25 ◦ C while incomplete resistance at 20 ◦ C and susceptibility at 15 ◦ C [27]. This line was completely resistant against E. trifolii at 20 and 25 ◦ C [22]. These results suggest that the resistance in JI2480 to E. pisi is temperature-dependent, while the interaction between this genotype and E. trifolii is temperature-independent

  • Pea productivity is constrained by powdery mildew (PM) disease, which is prevalent throughout pea growing regions

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Summary

Introduction

400 species, the majority of pathogenic species belong to the genus Erysiphe [6] These obligate biotrophic parasites infect nearly 10,000 species of angiosperms, including cereals, pulses, fruits, vegetables and ornamental plants [7,8]. Many of these are host-specific or target a very small number of hosts, suggesting the presence of very specific pathogenesisrelated (PR) genes. There is no comprehensive review covering the pathogen, novel variations of the er genes/alleles, advances in mapping strategies, linked markers and future strategies to combat the disease. (b): the affected pods of commercial cultivar ‘PC-5310 from India; (c): the susceptible and resistant lines growing under natural epiphytic conditions at ICAR-IIVR, Varanasi, India

Erysiphe Species Infecting Peas
Screening under Natural Epiphytic Conditions
Controlled Conditions
PM Disease Scale in Pea
Genetics
Resistance Mechanism and the Temperature-Based Reaction of Resistant Genes
The Biochemical Aspect
The Molecular Aspect
Allelic Variations at er1 Locus
Comparative Mapping
Conventional Approaches
Molecular Breeding Using Linked DNA Markers
Gene Introgression from Related Species
Characterization and Introduction of Resistant Sources
Host–Pathogen Interaction and Disease Development
10. Conclusions

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