Location: National Clonal Germplasm RepositoryTitle: Creating DNA-based tests for the pear chromosome 2 fire blight resistance region
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/28/2020
Publication Date: 8/9/2020
Citation: Zurn, J.D., Driskill, M.J., Bassil, N.V. 2020. Creating DNA-based tests for the pear chromosome 2 fire blight resistance region. Abstract for American Society for Horticultural Science Annual Conference, August 9-13, 2020, Orlando, FL
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. Using the newest assembly of the pear genome, we have identified 400 genes in this region. In order to characterize the QTL region and develop tools for DNA-informed breeding, genes were sequenced from Potomac, Old Home, NJA2R59T69, susceptible parents, and resistant and susceptible progeny generated from these crosses. 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 from this source. Further work is needed to develop diagnostic markers, validate these markers and pycom02g05250, and identify the gene responsible for NJA2R59T69 mediated resistance.