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Research Project: Management of Temperate-Adapted Fruit, Nut, and Specialty Crop Genetic Resources and Associated Information

Location: National Clonal Germplasm Repository

Title: Developing DNA-based tests to breed fire blight resistant pears

item Zurn, Jason
item Driskill, Mandie
item Bassil, Nahla

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2020
Publication Date: 8/8/2020
Citation: Zurn, J.D., Driskill, M.J., Bassil, N.V. 2020. Developing DNA-based tests to breed fire blight resistant pears. Abstract for Plant Health 2020, August 10-14, 2020, Denver, CO

Interpretive Summary: Fire blight is a devistating disease of pears and is a constant problem in U.S. The most commonly grown rootstocks and scions are suceptible to the disease and new resistant varieties are needed. Recently a region in the pear genome was identified in three varieties that provided ressitance to fire blight. In this region there are 400 genes. These genes were sequenced to identify differences in DNA that are associate with fire blight resistance. A set of 13 DNA variations were found to be shared between the resistant varietes Moonglow, Potomac, and Old Home in the gene pycom02g05250. We are investigating these variations for DNA-test design for future breeding efforts

Technical Abstract: Fire blight, caused by Erwinia amylovora, is one of the most devastating diseases of pears (Pyrus spp.) and is a persistent problem in major production regions in the U.S. The most commonly grown scions and rootstocks are susceptible to the disease and new resistant cultivars are needed. Very little work has been done to identify fire blight resistance quantitative trait loci (QTLs) in pear. QTLs have been consistently detected in a similar region on chromosome 2 in the resistant cultivars Moonglow, Potomac, Old Home, and the selection NJA2R59T69. Recent advancements in pear genomics have shown that approximately 400 genes are present in this region. In order to characterize the QTL region and develop tools for DNA-informed breeding, genes were sequenced in resistant and susceptible progeny of Potomac, Old Home, and NJA2R59T69 and the parental varieties. Average coverage of the genes in this region was approximately 50X per sample and 14,020 polymorphisms were identified. The resistance in ‘Moonglow’, ‘Potomac’, and ‘Old Home’ was found to have 13 shared polymorphisms in the receptor-like kinase gene pycom02g05250. This is in agreement with previous hypotheses that the same gene mediates resistance to fire blight in these cultivars. Interestingly, these polymorphisms were not identified in resistant progeny derived from NJA2R59T69 supporting the hypothesis that a different gene is responsible for resistance. Further work is needed to develop diagnostic markers, validate these markers and pycom02g05250, and identify the gene responsible for NJA2R59T69 mediated resistance.