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Title: Potential sources of resistance in U.S. cucumis melo PIs to crown rot caused by phytophthora capsici

item DONAHOO, RYAN - University Of Florida
item Turechek, William
item Thies, Judy
item Kousik, Chandrasekar - Shaker

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2010
Publication Date: 2/1/2013
Citation: Donahoo, R.S., Turechek, W., Thies, J.A., Kousik, C.S. 2013. Potential sources of resistance in U.S. cucumis melo PIs to crown rot caused by phytophthora capsici. HortScience. 48(2):164-170.

Interpretive Summary: Melon is an important crop grown in many states across the US. Many different pests and diseases attack melon plants causing extensive damage. Crown rot is an important seedling disease that can cause severe damage and kill plants in the melon and pumpkin family. We evaluated over 300 wild melon varieties and plants types collected from different regions of the world for their reaction to crown rot in the greenhouse. Several wild melon plant types with moderate levels of resistance to crown rot were identified. These wild melons may be useful as sources of resistance to plant breeders for developing superior melon cultivars that are resistant to crown rot.

Technical Abstract: Phytophthora capsici is an aggressive pathogen that is distributed worldwide with a broad host range infecting solanaceous, fabaceous, and cucurbitaceous crops. Over the past two decades, increased incidence of Phytophthora blight, particularly in eastern states has threatened production of many vegetable crops. Cucumis melo (Honeydew and Cantaloupe), while especially susceptible to fruit rot, is also susceptible to crown/root rot. Currently, little is known about host resistance to P. capsici in C. melo. To assess crown rot resistance in C. melo seedlings, 308 US Plant Introductions (PIs), and two susceptible commercial hybrid cultivars (Athena and Dinero) were grown under greenhouse conditions. After three to four leaves emerged, seedlings were inoculated with a five isolate zoospore suspension (1 x 104/seedling) at the crown and monitored for six weeks. All the control plants died within seven days post inoculation. Several PIs (PI 181748, PI 182964, and PI 273438) succumbed earlier than ‘Athena’ and ‘Dinero’ due to crown rot. Eighty seven PIs (28%) appeared to have some degree of tolerance to P. capsici. The level of resistance to P. capsici within individual PIs was variable. Eighty seven PIs selected on the basis of the first screen were reevaluated and of these PIs, 44 were less susceptible than ‘Dinero’ and ‘Athena’. Twenty five of the 87 PIs were evaluated again and of these PI 420180, PI 344069, PI 266942, PI 176940, PI 525103, PI 176936 and PI 344068 had >80% of the plants survive in the two evaluations. Disease development was significantly slower on these PIs compared to the susceptible checks. Further screening and careful selection within each of these PIs can provide a framework for the development of resistant germplasm for use in breeding programs.