ARS | Publication request: Response of U.S. bottle gourd (Lagenaria siceraria) Plant Introductions to Phytophthora capsici

Submitted to: International Phytophthora Capsici Conference
Publication Type: Proceedings
Publication Acceptance Date: October 22, 2007
Publication Date: November 27, 2007
Citation: Kousik, C.S., Thies, J.A. 2007. Response of U.S. bottle gourd (Lagenaria siceraria) Plant Introductions to Phytophthora capsici. International Phytophthora Capsici Conference, Islamorada, FL, 2007. p.27.

Technical Abstract: Phytophthora capsici causes severe damage to cucurbit crops grown in open fields in southeast U.S. Most cucurbit species are susceptible to damping-off, root and crown rot, and/or fruit rot caused by P. capsici. Bottle gourd plants (Lagenaria siceraria), which are resistant to Fusarium wilt, are being used in Asia and Europe as rootstocks for grafting of Fusarium-susceptible watermelon scions. Recently, there has been a growing interest in the U.S. in grafting watermelon plants onto various cucurbit rootstocks. However, the cost of grafted plants is still a concern to U.S. watermelon growers. Although gourd plants are resistant to Fusarium wilt, they may be susceptible to other root and foliar diseases including P. capsici. The response of L. siceraria Plant Introductions (PIs) to P. capsici and the identification of resistant accessions would be valuable information for cucurbit rootstock breeding programs. In greenhouse tests, we evaluated approximately 200 U.S. PIs of L. siceraria for resistance to P. capsici. Five four-week-old seedlings of each PI were inoculated with ca. 10,000 P. capsici zoospores suspended in one ml of distilled water. Seven isolates of P. capsici isolated from cucurbits and pepper in South Carolina were used in equal proportions in the zoospore suspension. Plants of ‘Mickey Lee’ watermelon were included as the susceptible check. The test was repeated once. Plants were rated on a 1 to 9 scale of increasing disease severity where 1=no symptoms to 9=plants dying or dead. Significant variability in level of resistant to P. capsici on plants within PIs was observed. ‘Mickey Lee’ was highly susceptible to P. capsici with all plants dead within 2 to 3 weeks after inoculation. Eleven (5.2%) of the PIs evaluated were resistance to P. capsici. Of these 11, four were resistant and 7 were moderately resistant. PI 419215 appeared to be the most resistant. These 11 PIs are being further evaluated to confirm their resistance to P. capsici.