Development and validation of codominant markers for recessive gene er2 conferring resistance to powdery mildew in peas (Pisum sativum L.)
摘要
Powdery mildew disease caused by Erysiphe spp inflicts heavy losses in pea crop worldwide. A recessive powdery mildew resistance gene er2 present in pea genotype JI2480 provides a broad-spectrum protection against powdery mildew disease in peas. In the present study, we targeted pea genome sequences around a previously known dominant Sequence Characterized Amplified Region (SCAR) marker ScX17_1400 for developing co-dominant markers for utilization in marker-assisted selection of the er2 gene. Of the ten STS markers developed from the target region, four were effectively converted into Cleaved Amplified Polymorphic Sequence (CAPS) markers. These polymorphic CAPS markers and two LG3-specific SSR markers, AA278 and AA5, exhibited close linkage to er2 when tested on a BC7F2 population derived from a cross between the susceptible genotype Azad P-1 and JI2480. The linkage map of the er2 locus spanned a 5.9 cM region wherein AA278 was most closely linked to er2 at a distance of 1.8 cM. Three cosegregating markers, PsLG3_CAPS-1, PsLG3_CAPS-3, and PsLG3_CAPS-4, were positioned at a distance of 3.2 cM from the gene. When tested across a panel of 28 commercial pea genotypes, the different markers differentiated 6 to 22 commercial pea varieties from er2 donor line JI2480. These markers collectively distinguished 26 commercial pea varieties from JI2480, thereby suggesting their utility for marker-assisted selection of the er2 gene in crosses with these genotypes serving as recipient or recurrent parents. As these markers also differentiated a significant number of commercial pea varieties believed to possess the er1 gene from the er2 donor line JI2480, they can also be effectively utilized to integrate both resistance genes (er1 and er2) in these genetic backgrounds for achieving a broad spectrum and durable resistance against powdery mildews.