Open AccessCultivar-Based Introgression Mapping Reveals Wild Species-Derived Pm-0, the Major Powdery Mildew Resistance Locus in Squash
Author(s) -
William L. Holdsworth,
Kyle E. LaPlant,
Duane C. Bell,
Molly M. Jahn,
Michael Mazourek
Publication year - 2016
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0167715
Subject(s) - powdery mildew , cucurbita pepo , introgression , cucurbita moschata , biology , cucurbita , botany , plant disease resistance , genetics , gene , medicine , alternative medicine , pathology
Powdery mildew is a major fungal disease on squash and pumpkin ( Cucurbita spp.) in the US and throughout the world. Genetic resistance to the disease is not known to occur naturally within Cucurbita pepo and only infrequently in Cucurbita moschata , but has been achieved in both species through the introgression of a major resistance gene from the wild species Cucurbita okeechobeensis subsp. martinezii . At present, this gene, Pm-0 , is used extensively in breeding, and is found in nearly all powdery mildew-resistant C . pepo and C . moschata commercial cultivars. In this study, we mapped C . okeechobeensis subsp. martinezii -derived single nucleotide polymorphism (SNP) alleles in a set of taxonomically and morphologically diverse and resistant C . pepo and C . moschata cultivars bred at Cornell University that, by common possession of Pm-0 , form a shared-trait introgression panel. High marker density was achieved using genotyping-by-sequencing, which yielded over 50,000 de novo SNP markers in each of the three Cucurbita species genotyped. A single 516.4 kb wild-derived introgression was present in all of the resistant cultivars and absent in a diverse set of heirlooms that predated the Pm-0 introgression. The contribution of this interval to powdery mildew resistance was confirmed by association mapping in a C . pepo cultivar panel that included the Cornell lines, heirlooms, and 68 additional C . pepo cultivars and with an independent F 2 population derived from C . okeechobeensis subsp. martinezii x C . moschata . The interval was refined to a final candidate interval of 76.4 kb and CAPS markers were developed inside this interval to facilitate marker-assisted selection.