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United States Department of Agriculture

Agricultural Research Service

2007 Annual Report

1a.Objectives (from AD-416)
The overall objective of this project is to develop novel basic and applied solutions within an integrated/organic framework for reducing disease and insect losses in cucurbit crops while producing safe, nutritious products for consumers. The specific objectives include: .
1)identify and develop systems for suppression of soilborne diseases using grafting and/or biofumigant crops to formulate novel control strategies applicable to organic and conventional vegetable speciality crops; .
2)elucidate virulence parameters of selected pre- and postharvest pathogen populations, define the role of polygalacturonase-inhibiting protein (PGIP) as a plant pathogen defense mechanism, and use this information to develop integrated methodologies for natural control of cucurbit diseases in conventional and organic production; .
3)characterize strains of Serratia marcescens from different ecological niches with special reference to the phloem-inhabiting strain that causes cucurbit yellow vine disease; .
4)develop behavior-based alternative controls for insect vectors of CYVD and other key insect pests of vegetable crops; and.
5)identify and develop disease-resistant germplasm and inbred lines for release to the seed industry.

1b.Approach (from AD-416)
Because plant-pest/host relationships are inherently difficult to study, more precise methods of quantifying pathogen virulence and of understanding insect behavior are prerequisite in formulating and measuring effective pest control strategies. This project's overall approach is to develop technologies necessary to devise integrated systems for conventional and organic producers to control disease and insect pests of watermelon, cantaloupe, and other specialty crops. Biofumigant crops (mustard) and biocontrol microbes will be integrated into the cropping system along with resistant germplasm for suppression of soilborne diseases. Grafting plants onto resistant rootstock will be part of a diverse approach for developing sustainable farming systems.

Powdery Mildew Resistant Watermelon: Powdery mildew on watermelon, which appeared in the U.S. in early 2000, can have a drastic economic impact for growers and seed companies. Recombinant inbred lines that have differential expression for powdery mildew resistance were developed by a scientist at the South Central Agricultural Research Laboratory, Lane, OK. Genetic resistance to race 1 powdery mildew has not been documented in commercial cultivars. Incorporating resistance from unimproved varieties or wild watermelon relatives may provide control for this pathogen, reducing or eliminating the need for fungicide applications. This recombinant inbred line will be used to map resistance genes. This may lead to development of molecular markers for resistance to this disease. (NP 303, Component 5A, Problem Statement 3B)

Virulence Characterization of the Fusarium solani Complex Causing Fruit Rot of Cantaloupe: Fruit rot caused by Fusarium species is probably the most frequent cause of preharvest and postharvest decay in the $400 million/year U.S. muskmelon crop. Presently, there is no simple predictive method for level of virulence involved in fungal fruit rot of cantaloupe. Scientists at the South Central Agricultural Research Laboratory, Lane, OK, demonstrated that virulence of F. solani strains causing cantaloupe fruit rot may be associated with the fungi’s ability to produce significant levels of three types of pectinolytic enzymes simultaneously. This accomplishment lays the foundation for a simple, straightforward means to characterize and predict the virulence of isolates of this fungus to produce fruit rot in cantaloupe. (NP 303, Component 2, Problem Statement 2A)

5.Significant Activities that Support Special Target Populations
Provided disease identification techniques, monitoring of disease development, and supplied pest management strategies for African-American and Hispanic farmers. Mentored a Native American student during the summer Choctaw Nation work program.

6.Technology Transfer

Number of non-peer reviewed presentations and proceedings8

Review Publications
Bruton, B.D., Fish, W.W., Subbarao, K.V., Isakeit, T. 2007. First report of Verticillium wilt of watermelon in the Texas High Plains. Plant Disease. 91:1053.

Davis, A.R., Levi, A., Wehner, T.C., Pitrat, M. 2006. PI 525088-pmr, a melon race 1 powdery mildew-resistant watermelon line. HortScience. 47(7):1527-15-28.

Last Modified: 9/21/2014
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