Genetic analyses by the Quesada laboratory at NC State found that different clades of P. cubensis vary for the predominant mutations conferring resistance. These findings of clade-specific resistances can facilitate the design of more effective fungicide programs tailored to crop and region.
CucCAP Featured Articles
The CucCAP website features recently published articles from the four crop teams, (Cucumber, Melon, Squash, and Watermelon) and the Bioinformatics, Breeding, & Genomics group. Integtated crop and disease management activities, articles and reports are also featured.
Improved detection methods for CDM
CucCAP researchers develop improved detection methods for downy mildews infecting cucurbit crops. Management of cucurbit downy mildew relies on an intensive fungicide program. Timely alerts of appearance of sporangia can help growers to determine need to initiate fungicide sprays. Research by CucCAP scientists developed improved ability to detect airborne sporangia and distinguish among types that infect different kinds of crops. This improved methodology could be used as part of an advisory system to time fungicide applications to protect cucurbit crops.
CucCAP researchers assemble genomic tools to study the development of giant pumpkin fruit
Cucurbit fruits come in different shapes and sizes, controlled by genes underlying cell size and number. In a recent study, a team at West Virginia State University (WVSU) identified genetic factors underlying the giant fruit size of the mammoth group of Cucurbita maxima. The study elucidated genome diversity and identified single nucleotide polymorphism (SNP) markers associated with genes controlling fruit size. In addition to the genomic toolkit useful for breeding programs aiming at pumpkin fruit traits, this study provides insight into population differentiation and evolutionary origins of rare variants contributing to the giant fruit size of certain pumpkin varieties.
CucCAP scientists genetically map novel sources of resistance to cucurbit downy mildew in watermelon
Watermelon crops are increasingly threatened by infection by cucurbit downy mildew. While there are limited sources of disease resistance within cultivated watermelon, Citrullus amarus can be a valuable source of resistances. CucCAP scientists performed disease resistance screening and whole genome resequencing of 122 C. amarus accessions. Genome wide association analysis of these materials identified several marker-trait associations and candidate genes, providing potential resources for genomics-assisted breeding for resistance to CDM in watermelon.
Cucurbitaceae 2022 brings together international cucurbit community
The Cucurbitaceae 2022 conference was held in Naples, Florida on October 30 – November 2. The conference was organized by CucCAP co-PIs Geoffrey Meru from the University of Florida and Cecilia McGregor from the University of Georgia. Researchers and industry representatives from North America, Europe and Asia shared information about cucurbit genomics, breeding, disease resistance and cultivation. CucCAP researchers presented 28 talks and posters.
CucCAP scientists identified candidate gene contributing to resistance to downy mildew in cucumber
Downy mildew (DM) is an important disease of cucumber and other cucurbits. Many quantitative trait loci (QTL) have been identified from different resistant resources but very few have been fine mapped or cloned. CucCAP researchers in USDA-ARS and the University of Wisconsin Madison reported identification and functional characterization of the candidate gene for the major-effect QTL, dm5.3, for DM resistance from the plant introduction line PI 197088. This gene, which can enhance plant disease signaling, is currently being used to breed for disease resistance in cucumber.
CucCAP scientists use genomic approaches to facilitate breeding for PRSV-W resistance in squash
Papaya ringspot virus-W (PRSV-W) causes severe yield losses in squash production. The Meru laboratory at the University of Florida identified a single QTL for resistance on Chromosome 09 of the C. moschata genome. Subsequent testing identified two SNP markers as potential targets for marker-assisted selection. The findings of this study will facilitate breeding for resistance against PRSV-W in commercial squash cultivars.
CucCAP scientist examines economic impacts of reduced fungicide efficacy against downy mildew
Resistance to fungicides is a concern with cucumber downy mildew, Pseudoperonospora cubensis clade 2. These fungicides still suppressed downy mildew well enough that yields of marketable-sized fruit of a susceptible slicing cucumber were much better than not spraying.
