Powdery mildew resistant bottle gourd germplasm lines: USVL351-PMR and USVL482-PMR

Authors: Kousik, Chandrasekar - Shaker; Ikerd, Jennifer; MANDAL, MIHIR - Oak Ridge Institute For Science And Education (ORISE); Adkins, Scott; Webster, Craig; Turechek, William

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2018
Publication Date: 8/24/2018
Citation: Kousik, C.S., Ikerd, J.L., Mandal, M., Adkins, S.T., Webster, C.G., Turechek, W. 2018. Powdery mildew resistant bottle gourd germplasm lines: USVL351-PMR and USVL482-PMR. HortScience. 53(8):1224-1227. https://doi.org/10.21273/HORTSCI13067-18.
DOI: https://doi.org/10.21273/HORTSCI13067-18

Interpretive Summary: Watermelon is an important vegetable crop grown in 44 states in the U.S.A. Many diseases and pests attack watermelon seedlings and plants and reduce their yield resulting in monetary loss for growers. One such disease, known as Fusarium wilt can infect watermelon plants in the field and can result in death of plants and also result in yield reduction. Grafting watermelon on bottle gourd rootstocks can help manage this disease. However, most of the available rootstocks are susceptible to another disease known as powdery mildew. ARS scientists in Charleston, SC, have developed two bottle gourd germplasm lines, USVL351-PMR and USVL482-PMR with resistance to powdery mildew. These resistant germplasm lines can be used by private and public sector plant breeders to develop new bottle gourd rootstocks with resistance to powdery mildew. The powdery mildew resistant bottle gourd lines will also be useful in Asian countries to develop resistant varieties where bottle gourd is used for human consumption. Development of varieties and rootstocks with resistance to powdery mildew will help reduce pesticide use and allow growers to produce a healthy crop. The germplasm lines will be useful to university researchers, and private sector plant breeders.

Technical Abstract: USVL351-PMR (powdery mildew resistant) and USVL482-PMR are bottle gourd (Lagenaria siceraria) germplasm lines that exhibit high levels of resistance to the cucurbit powdery mildew (PM) pathogen (Podosphaera xanthii) compared to susceptible commercial bottle gourd rootstocks and other plant introductions (PI). Powdery mildew is an important foliar disease affecting cucurbit crops grown in the United States and most parts of the world. It commonly occurs on seedlings, mature plant foliage, petioles, and stems. Resistance in these two germplasm lines is expressed as none to a few powdery mildew lesions, with sparse pathogen mycelia or conidia observed on young seedlings (including hypocotyls, cotyledons and true leaves) in greenhouse evaluations. In comparison, severe powdery mildew development and abundant pathogen conidia can be observed on the susceptible rootstock Emphasis and the susceptible line USVL848-PMS. Mature plants of USVL351-PMR and USVL482-PMR are also tolerant to powdery mildew under field conditions in South Carolina. These two germplasm lines are highly uniform for powdery mildew resistance and growth characteristics, including fruit size, shape and color. Most commercial bottle gourd lines currently used as watermelon rootstocks in United States are not resistant to cucurbit powdery mildew. Thus USVL351-PMR and USVL482-PMR can serve as useful sources for incorporating resistance to powdery mildew in commercially acceptable bottle gourd rootstocks and cultivars. These lines will also be useful for incorporating powdery mildew resistance in bottle gourd varieties that are cultivated for fruit consumption in Asia. These are the first bottle gourd germplasm lines with resistance to powdery mildew released in the United States.