Pea, an important grain legume crop, suffers significant yield and quality losses because of infections by the parasitic fungus Erysiphe pisi Syd., the causal agent of powdery mildew. Most pea cultivars in western Canada are susceptible to this fungus. The genetic basis of resistance found in certain Canadian cultivars is unclear. Resistant cultivars and lines were intercrossed with each other and crossed with susceptible lines to determine the genetic basis of resistance. Resistance in the cultivars Highlight, AC Tamor, Tara, Mexique 4, Stratagem and lines JI 210, JI 1951, JI 1210 was found to be conferred by a single recessive gene, er-1. The resistance in line JI 2480 is conferred by a different recessive gene, er-2. Resistance provided by er-1 was durable under both field and growth cabinet conditions, however, resistance of er-2 was broken under controlled growth conditions. Combining er-1 and er-2 in a cultivar could increase the durability of resistance. Key words: pea, Pisum sativum, powdery milde...

Inheritance of Powdery Mildew in Peas (Pisum Sativum L.)

Inheritance of powdery mildew resistance in pea

SUMMARY Powdery mildew is an economically important disease in a number of crop legumes; however, little is known about resistance to the disease in these species. To gain a better understanding of the genetics of resistance and plant responses to powdery mildew in legumes, we developed a pathosystem with Medicago truncatula and Erysiphe pisi. Screening accessions of M. truncatula identified genotypes that are highly susceptible, moderately resistant and highly resistant to the fungus. In the highly resistant genotype, fungal growth was arrested after appressorium development with no colony formation, while in the moderately resistant genotype a small number of colonies formed. Both resistant and moderately resistant genotypes produced hydrogen peroxide and fluorescent compounds at pathogen penetration sites, consistent with a hypersensitive response (HR), although the response was delayed in the moderately resistant genotype. Very little hydrogen peroxide or fluorescence was detected in the susceptible accession. Microarray analysis of E. pisi-induced early transcriptional changes detected 55 genes associated with the basal defence response that were similarly regulated in all three genotypes. These included pathogenesis-related genes and other genes involved in defence, signal transduction, senescence, cell wall metabolism and abiotic stress. Genes associated with the HR response included flavonoid pathway genes, and others involved in transport, transcription regulation and signal transduction. A total of 34 potentially novel unknown genes, including two legume-specific genes, were identified in both the basal response and the HR categories. Potential binding sites for two defence-related transcription regulators, Myb and Whirly, were identified in promoter regions of induced genes, and four novel motifs were found in promoter regions of genes repressed in the resistant interaction.

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Molecular and cytological responses of Medicago truncatula to Erysiphe pisi

Medicago truncatula was used to characterize resistance to anthracnose and powdery mildew caused by Colletotrichum trifolii and Erysiphe pisi, respectively. Two isolates of E. pisi (Ep-p from pea and Ep-a from alfalfa) and two races of C. trifolii (races 1 and 2) were used in this study. The A17 genotype was resistant and displayed a hypersensitive response after inoculation with either pathogen, while lines F83005.5 and DZA315.16 were susceptible to anthracnose and powdery mildew, respectively. To identify the genetic determinants underlying resistance in A17, two F7 recombinant inbred line (RIL) populations, LR4 (A17 × DZA315.16) and LR5 (A17 × F83005.5), were phenotyped with E. pisi isolates and C. trifolii races, respectively. Genetic analyses showed that i) resistance to anthracnose is governed mainly by a single major locus to both races, named Ct1 and located on the upper part of chromosome 4; and ii) resistance to powdery mildew involves three distinct loci, Epp1 on chromosome 4 and Epa1 and Epa2 on chromosome 5. The use of a consensus genetic map for the two RIL populations revealed that Ct1 and Epp1, although located in the same genome region, were clearly distinct. In silico analysis in this region identified the presence of several clusters of nucleotide binding site leucine-rich repeat genes. Many of these genes have atypical resistance gene analog structures and display differential expression patterns in distinct stress-related cDNA libraries.

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Genetic dissection of resistance to anthracnose and powdery mildew in Medicago truncatula

The genetics of powdery mildew (Erysiphe pisi) resistance in pea (Pisum sativum) was studied using five isolates of E. pisi in a controlled environment. Resistance was controlled by a single recessive gene in all the pea cvs. included in the study. The same recessive gene controlled resistance to all the five isolates of E. pisi. Tests for allelism showed that resistance in cvs. HPPC-63, HPPC-95, DPP-26, DPP-54, Mexique-4, SVP-950, Wisconsin-7104 and P-6588 is conferred by the same recessive gene.

Genetics of powdery mildew resistance in pea

In this contribution we review the state of the art for genetic resistance to powdery mildew, caused by Erysiphe pisi, in pea (Pisum sativum L.) and potential use of marker-assisted selection (MAS) for developing disease resistant cultivars. Powdery mildew is important in many production regions worldwide and reduces yield and crop quality when present in epidemic proportions. Although genetic resistance to powdery mildew is available (er1 and er2) and has been durable since its characterization in 1969, recently a new dominant gene (Er3) has been reported in Pisum fulvum, a wild relative of pea that is different from previously reported er1 and er2. The efficacy of these genes may be at risk from the point of view of new pathotypes and pathogens. Erysiphe trifolii has been reported that was not previously known as a pathogen of pea powdery mildew. A continued search for new and diverse resistant sources remains a priority in pea breeding and special emphasis should be paid to selection of resistance that will prolong durability of existing resistance genes. Marker assisted selection is a new emerging approach for target breeding that has been intensively employed especially in cereals and has recently got popularity among legume breeders. With the advancement of genomic research, especially related to quantitative traits loci, the MAS is potentially anticipated future technique for routine plant breeding that is scarce in legumes at present. In pea, various DNA markers have been reported linked to er1, er2 and Er3 at varying distances in different mapping populations that are currently being used in breeding programs. Currently MAS of single gene is the most powerful approach and successes have been witnessed. If single marker is not close enough to the gene of interest then two flanking markers are considerably utilized to improve the correct identification that is being successfully employed in MAS for powdery mildew resistance in pea.

Inheritance of Powdery Mildew in Peas (Pisum Sativum L.)

Citations

Inheritance of powdery mildew resistance in pea

Molecular and cytological responses of Medicago truncatula to Erysiphe pisi

Genetic dissection of resistance to anthracnose and powdery mildew in Medicago truncatula

Genetics of powdery mildew resistance in pea

Marker assisted selection (MAS) for developing powdery mildew resistant pea cultivars