Location: Vegetable ResearchTitle: New sources of resistance to phytophthora crown and root rot in Cucuribta moschata
|Kousik, Chandrasekar - Shaker|
|MIHIR, MANDAL - Oak Ridge Institute For Science And Education (ORISE)|
Submitted to: Cucurbitacea
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2018
Publication Date: 11/12/2018
Citation: Kousik, C.S., Ikerd, J.L., Mandal, M.K. 2018. New Sources of Resistance to Phytophthora Crown and Root Rot in Cucurbita moschata. Presented Cucurbitaceae 2018, Davis, CA. Cucurbitaceae 2018 conference abstracts, Page 11. https://cucurbit2018.ucdavis.edu/ https://doi.org/358780.
Technical Abstract: Winter and crook neck squash (Cucurbita moschata) are important vegetable crops grown and consumed in most states in the USA. Among C. moschata, butternut type squash are the most popular and widely used across USA. Many C. moschata lines are also used to develop interspecific hybrid rootstocks for grafting watermelon in parts of Asia. However, most commercially available C. moschata varieties are highly susceptible to crown and root rot caused by the oomycete pathogen Phytophthora capsici which is prevalent in southeastern USA. As part of an USDA, NIFA SCRI grant we evaluated all the available plant introductions (PIs) of C. moschata (319 PIs) for resistance to P. capsici. Four-week-old plants growing in 6.3-cm square pots were inoculated with 104 zoospores from a local South Carolina (SC) isolate of P. capsici. Plants were rated for disease severity two weeks after inoculation using a 0-5 rating scale. The experiments were conducted twice. Twelve potential new sources of resistance (e.g. Grif 1738, PI 438724, PI 438778, PI 442280) to crown rot caused by the local SC isolate of P. capsici were identified. Further evaluation of the S1 and S2 generation from the most resistant plants from the first evaluation of the PI, indicated that highly resistant plants could be selected to develop lines for use in breeding programs. In a previous study done in Florida (FL) five sources of resistance to P. capsici (PI 176531, PI 458740, PI 442266, PI 442262, and PI 634693) were identified in C. moschata germplasm collection within USDA by evaluating 119 accessions (Chavez et al., 2011, HortScience 46(4):536-540). Interestingly Grif 1738 which was resistant to the isolate from SC was susceptible to the FL isolate in the 2011 screen (Chavez et al., 2011) indicating the potential for existence of host specific races of P. capsici based on C. moschata lines. This also suggests that new sources of resistance identified should be evaluated against P. capsici isolates from other states. These new sources of resistance can be utilized for developing new crown and root rot resistant rootstocks for watermelon grafting and also for developing resistant varieties for human consumption.