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United States Department of Agriculture

Agricultural Research Service

Title: Powdery Mildew: An Emerging Disease of Watermelon in the United States

Authors
item Davis, Angela
item Bruton, Benny
item Pair, Sammy
item Thomas, Claude

Submitted to: Cucurbit Genetics Cooperative Report
Publication Type: Trade Journal
Publication Acceptance Date: May 16, 2001
Publication Date: August 1, 2001
Citation: Davis, A.R., Bruton, B.D., Pair, S.D., Thomas, C.E. 2001. Powdery mildew: An emerging disease of watermelon in the United States. Cucurbit Genetics Cooperative Report. 24:42-48.

Interpretive Summary: Powdery mildew is a fungal disease that affects most cucurbit crops with often devastating results. Historically, watermelon has been resistant to the disease although outbreaks were confirmed last year in OK, TX, FL, CA and SC. This disease has epidemic potential, especially in the south central and southwestern United States. In this study we screened watermelon genotypes to find resistance to powdery mildew. Crosses were made in order to study the inheritance of resistance. Results of our study demonstrated that resistance to powdery mildew exists in the Plant Introduction Germplasm Collection. This information will be useful in transferring this resistance into commercial watermelon cultivars reducing the amount of fungicide needed to control the disease.

Technical Abstract: Powdery mildew has been a devastating disease for many cucurbit crops in the past. However, watermelon has typically been resistant to this disease. Unfortunately, outbreaks of powdery mildew in watermelon were confirmed last year in OK, TX, FL, CA and SC suggesting introduction of a more virulent race of powdery mildew. This is an emerging disease on watermelon in the U.S. and has epidemic potential. We have screened Citrullus lanatus for resistance to a virulent race of Sphaerotheca fuliginea. Results of our study demonstrated that tolerance to powdery mildew exists in the Plant Introduction Germplasm Collection. However, none of the C. lanatus screened were 100% resistant to the disease. The information gained from this study will be useful in transferring powdery mildew tolerance into commercial watermelon cultivars thus reducing the number of fungicide applications necessary for the control of powdery mildew on watermelon.

Last Modified: 12/25/2014