Progress 07/10/07 to 04/30/12
Outputs
Progress Report Objectives (from AD-416): Objective 1. Develop improved resistance to root-knot nematodes in pepper and watermelon. Objective 2. Identify and develop improved resistance to diseases in cucurbits, e.g. powdery mildew, downy mildew, Phytophthora blight, and watermelon vine decline. Objective 3. Elucidate virulence parameters of selected plant pathogen populations and develop integrated methodologies for managing cucurbit diseases. Approach (from AD-416): Develop root-knot nematode-resistant sweet banana, sweet cherry, pimiento, and Cubanelle type peppers using backcross breeding procedures. Determine inheritance of resistance to root-knot nematodes (Meloidogyne incognita) in watermelon in greenhouse studies, and use techniques such as single sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) to develop molecular markers linked to root-knot nematode resistance genes in watermelon. Screen watermelon and melon germplasm for resistance to Phytophthora capsici and develop resistant germplasm. Screen bottle gourd (Lagenaria siceraria) plant introductions for resistance to powdery mildew in the greenhouse and develop resistant germplasm for use in rootstock breeding program. Screen watermelon plant introductions for resistance to watermelon vine decline, and evaluate strategies and develop integrated methodologies to manage watermelon vine decline in field tests. Identify prevalent races of powdery mildew using melon host differentials and determine their virulence on other selected cucurbit species in greenhouse and field studies. Determine genetic variability in the downy mildew pathogen (Pseudoperenospora cubensis) isolated from watermelon and cucumber using host differentials and molecular markers. For fiscal year 2012, the watermelon lines were selected for resistance to root-knot nematodes and evaluated as rootstocks for managing root-knot nematode in grafted seedless watermelon in fields that were highly infested with southern root-knot nematodes. Several of the selected watermelon rootstocks exhibited significantly higher resistance to root- knot nematodes than rootstocks, such as bottle gourd and squash hybrid rootstocks, which are commonly used for grafted watermelon. Selected lines of root-knot nematode resistant wild watermelon were evaluated for fruit type, flesh color, and fruit yields in field tests. Sweetpotato and southernpea (cowpea) germplasm lines were evaluated for resistance to southern root-knot nematodes. Homozygous lines of sweet banana, sweet cherry, and Cubanelle selected for resistance to southern root-knot nematode, Meloidogyne incognita, and back-crossed to susceptible parents in order to recover fruit types of the original parents. Watermelon germplasm was screened for resistance to Phytophthora fruit rot and single plant selections from the most resistant lines were made to develop resistant watermelon germplasm. Wild bottle gourd germplasm lines were re-evaluated for resistance to powdery mildew, single plant selections were made to develop powdery mildew resistant bottle gourd germplasm, and crosses between resistant and susceptible bottle gourd lines were made to develop populations for inheritance studies. Isolates of powdery mildew and Phytophthora capsici from Florida, Georgia, and South Carolina, were collected for use in studies of genetic variability for each of these fungi within specific fields and within regions of the southeastern U.S. Strategies to manage white-fly transmitted viral watermelon vine decline, including insecticide treatments and resistant pollenizers, were developed and experiments have been completed. ARS scientists detected and reported a severe outbreak of powdery mildew on watermelon fruit in Florida. The disease appeared on the fruit surface and reduced fruit quality, thus reducing yield. Accurate identification of the pathogen is essential to the development of appropriate management practices. This work is being continued under 6659-22000-026-00D, Development of Disease and Nematode Resistance in Vegetable Crops. Accomplishments 01 Root-knot nematodes are an important and re-emerging pest of pepper in t southern U.S. Root-knot nematodes are microscopic roundworms that attac plant roots causing �galls� or swellings on the roots, which divert nutrients from the fruit and foliage of the plants, resulting in fewer a smaller pepper fruit yields in infected plants. Although root-knot nematode-resistant pepper varieties have been developed, an ARS scientis in Charleston, SC, recently discovered a new strain of southern root-kno nematode that can infect many of the previously released resistant bell and hot pepper varieties. This discovery is important because it may become necessary to screen wild pepper collections for resistance to thi and other new strains of root-knot nematodes in order to identify new sources of nematode resistance genes that can be incorporated into existing pepper varieties. 02 Powdery mildew is a common disease that generally occurs on watermelon leaves in commercial farms and is known to reduce fruit yield. However, the disease is not known to occur on fruit surface in the field. ARS scientists in Charleston, SC, detected and reported a severe outbreak of powdery mildew on watermelon fruit in commercial watermelon fields in Florida for the first time. The disease appeared on the fruit surface a reduced fruit quality, thus directly reducing yield. ARS scientists helped in accurate identification of the pathogen. Accurate identification of the pathogen will allow commercial watermelon growers use appropriate management practices to manage powdery mildew on the fru
Impacts
(N/A)
Publications
- Thies, J.A. 2012. Virulence of Meloidogyne incognita to expression of N gene in pepper. Journal of Nematology. 43(2):90-94.
- Guan, W., Zhao, X., Hassell, R., Thies, J.A. 2012. Defense mechanisms involved in disease resistance of grafted vegetables. HortScience. 47(2) :164-170.
- Kousik, C.S., Donahoo, R.S., Webster, C.G., Turechek, W., Adkins, S.T., Roberts, P.D. 2011. Outbreak of powdery mildew on watermelon fruit caused by podosphera xanthii in southwest Florida. Plant Disease. 95:1586.
- Keinath, A.P., Kousik, C.S. 2011. Sensitivity of isolates of phytophthora capsici from the eastern United States to fluopicolide. Plant Disease. 95:1414-1419.
- Adkins, S.T., Webster, C.G., Kousik, C.S., Webb, S.E., Roberts, P.D., Stansly, P.A., Turechek, W. 2011. Ecology and management of whitefly- transmitted vegetable viruses in Florida. Virus Research. 159:110-114.
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report Objectives (from AD-416) Objective 1. Develop improved resistance to root-knot nematodes in pepper and watermelon. Objective 2. Identify and develop improved resistance to diseases in cucurbits, e.g. powdery mildew, downy mildew, Phytophthora blight, and watermelon vine decline. Objective 3. Elucidate virulence parameters of selected plant pathogen populations and develop integrated methodologies for managing cucurbit diseases. Approach (from AD-416) Develop root-knot nematode-resistant sweet banana, sweet cherry, pimiento, and Cubanelle type peppers using backcross breeding procedures. Determine inheritance of resistance to root-knot nematodes (Meloidogyne incognita) in watermelon in greenhouse studies, and use techniques such as single sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) to develop molecular markers linked to root-knot nematode resistance genes in watermelon. Screen watermelon and melon germplasm for resistance to Phytophthora capsici and develop resistant germplasm. Screen bottle gourd (Lagenaria siceraria) plant introductions for resistance to powdery mildew in the greenhouse and develop resistant germplasm for use in rootstock breeding program. Screen watermelon plant introductions for resistance to watermelon vine decline, and evaluate strategies and develop integrated methodologies to manage watermelon vine decline in field tests. Identify prevalent races of powdery mildew using melon host differentials and determine their virulence on other selected cucurbit species in greenhouse and field studies. Determine genetic variability in the downy mildew pathogen (Pseudoperenospora cubensis) isolated from watermelon and cucumber using host differentials and molecular markers. Single plant selections from Squash Vein Yellowing Virus (SqVYV) resistant wild watermelon germplasm lines were made to develop resistant watermelon germplasm. Wild melon (cantaloupe) germplasm lines were evaluated for resistance to crown rot caused by Phytophthora capsici and several resistant lines were identified. The core collection of watermelon Plant Introductions (PI), consisting of more than 200 PI, was evaluated for resistance to Phytophthora fruit rot and several lines with high levels of resistance were identified. Single plant selections from the most resistant lines were made to develop resistant watermelon germplasm. Wild bottle gourd germplasm lines were re-evaluated for resistance to Phytophthora crown rot and powdery mildew. Single plant selections were made to develop crown rot and powdery mildew resistant bottle gourd germplasm. Isolates of Phytophthora capsici from the southeast U.S. (Florida, Georgia, and South Carolina) were collected and will be used to study genetic variability of this fungus within specific fields and within regions of the southeast U.S. Insecticide treatments and resistant pollenizers were developed and evaluated for management of whitefly-transmitted SqVYV, which causes viral watermelon vine decline. Field studies were conducted to evaluate selected wild watermelon rootstocks for managing root-knot nematodes in grafted watermelon. Four watermelon rootstocks were moderately resistant to southern root-knot nematode and one rootstock produced significantly greater fruit yields than the other rootstocks. Studies on inheritance of resistance to southern root-knot nematode in watermelon were conducted. Pepper germplasm lines were screened and selected for resistance to northern root-knot nematode (Meloidogyne hapla) in greenhouse studies. Homozygous lines of sweet peppers were selected for resistance to southern root-knot nematode (Meloidogyne incognita). Fifteen cucurbit cultivars and wild germplasm lines were evaluated for their potential as rootstocks for managing southern root-knot nematode in grafted melon (cantaloupe) in field plots where soil had been fumigated with methyl bromide or not fumigated (control). Sweetpotato and southernpea (cowpea) germplasm lines were evaluated for resistance to southern root-knot nematodes. Accomplishments 01 Phytophthora fruit rot of watermelon is an important and emerging diseas in the southeastern U.S. This disease is caused by a fungus and can result in severe losses to watermelon production. There were no effecti strategies to manage this important disease, so ARS scientists tested different fungicides (chemicals that can kill or reduce growth of the fungus) for managing Phytophthora fruit rot of watermelon. Of nine fungicides tested, Revus and Presidio were the most effective for controlling Phythophthora fruit rot. These fungicides are considered to be reduced risk pesticides and can be used safely by growers to manage Phytophthora fruit rot of watermelon.
Impacts
(N/A)
Publications
- Thies, J.A., Ariss, J.J., Hassell, R.L., Olsen, S., Kousik, C.S., Levi, A. 2010. Grafting for Management of Southern Root-knot Nematode, Meloidogyne Incognita, in Watermelon. Plant Disease. 94(10):1195-1199.
- Kousik, C.S., Adams, M.L., Jester, W.R., Hassell, R., Harrison Jr, H.F., Holmes, G.J. 2011. Effect of Cultural Practices and Fungicides on Phytophthora Fruit Rot of Watermelon in the Carolinas. Crop Protection. 30:888-894.
- Webster, C.G., Kousik, C.S., Roberts, P., Rosskopf, E.N., Turechek, W., Adkins, S.T. 2011. Cucurbit yellow stunting disorder virus detected in pigweed in Florida. Plant Disease. 95(3):360.
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report Objectives (from AD-416) Objective 1. Develop improved resistance to root-knot nematodes in pepper and watermelon. Objective 2. Identify and develop improved resistance to diseases in cucurbits, e.g. powdery mildew, downy mildew, Phytophthora blight, and watermelon vine decline. Objective 3. Elucidate virulence parameters of selected plant pathogen populations and develop integrated methodologies for managing cucurbit diseases. Approach (from AD-416) Develop root-knot nematode-resistant sweet banana, sweet cherry, pimiento, and Cubanelle type peppers using backcross breeding procedures. Determine inheritance of resistance to root-knot nematodes (Meloidogyne incognita) in watermelon in greenhouse studies, and use techniques such as single sequence repeat (SSR) and sequence-related amplified polymorphism (SRAP) to develop molecular markers linked to root-knot nematode resistance genes in watermelon. Screen watermelon and melon germplasm for resistance to Phytophthora capsici and develop resistant germplasm. Screen bottle gourd (Lagenaria siceraria) plant introductions for resistance to powdery mildew in the greenhouse and develop resistant germplasm for use in rootstock breeding program. Screen watermelon plant introductions for resistance to watermelon vine decline, and evaluate strategies and develop integrated methodologies to manage watermelon vine decline in field tests. Identify prevalent races of powdery mildew using melon host differentials and determine their virulence on other selected cucurbit species in greenhouse and field studies. Determine genetic variability in the downy mildew pathogen (Pseudoperenospora cubensis) isolated from watermelon and cucumber using host differentials and molecular markers. Field studies were conducted to determine usefulness of wild watermelon, squash hybrid, and bottle gourd rootstocks for managing root-knot nematodes in grafted watermelon. Wild watermelon rootstocks were moderately resistant to southern root-knot nematode and one rootstock produced significantly greater fruit yields than the other rootstocks. Studies on inheritance of resistance to southern root-knot nematode in watermelon were conducted. Two greenhouse studies to assess whether root- knot nematode predisposes pepper plants to Phytophthora blight, caused by Phytophthora capsici, were completed. Pepper germplasm lines were screened and selected for resistance to northern root-knot nematode (Meloidogyne hapla) in greenhouse studies. Field studies were conducted to determine usefulness of several cucurbit species as rootstocks for managing southern root-knot nematode in grafted melon (cantaloupe). Sweetpotato and southernpea (cowpea) germplasm lines were evaluated for resistance to southern root-knot nematodes. Single plant selections from Squash Vein Yellowing Virus (SqVYV) resistant wild watermelon germplasm lines were made to develop resistant watermelon germplasm. Wild melon (cantaloupe) germplasm lines were evaluated for resistance to crown rot caused by Phytophthora capsici and several resistant lines were identified. Over 1,800 wild watermelon germplasm lines were re-evaluated for resistance to Phytophthora capsici and several lines resistant to Phytophthora foliar blight and fruit rot were identified. Over 200 plant introductions of watermelon were evaluated for resistance to Phytophthora fruit rot and several resistant lines were identified. Single plant selections from the most resistant lines were made to develop resistant watermelon germplasm. Wild bottle gourd germplasm lines were re- evaluated for resistance to Phytophthora crown rot and foliar blight and several resistant lines were identified. Single plant selections were made to develop crown rot and foliar blight resistant bottle gourd germplasm. Isolates of Phytophthora capsici from the southeast U.S. (Florida, Georgia, and South Carolina) were collected and will be used to study genetic variability of this fungus within specific fields and within regions of the southeast U.S. Strategies to manage white-fly transmitted viral watermelon vine decline including insecticide treatments and resistant pollenizers were developed and tested. Accomplishments 01 Grafting watermelon on resistant rootstocks for managing root-knot nematodes. Root-knot nematodes (RKN, Meloidogyne spp.) are microscopic roundworms that cause extensive damage to root systems of watermelon and many other vegetable crops, resulting in significant yield losses. ARS scientists (Charleston, SC) have identified wild watermelon (Citrullus lanatus var. citroides) lines resistant to RKN. These wild watermelon lines were evaluated as rootstocks for grafted watermelon in field tests in South Carolina and Florida. The RKN resistant lines performed well as rootstocks, and produced high yields for the grafted watermelon plants. These wild watermelon rootstocks could be a useful alternative to soil fumigation with pesticides such as methyl bromide for managing RKN in watermelon fields. Also, they can be useful for seed companies intereste in developing rootstock varieties for grafted watermelon.
Impacts
(N/A)
Publications
- Thies, J.A., Ariss, J. 2009. Comparison between the N and Me3 Genes Conferring Resistance to the Root-Knot Nematode (Meloidogyne incognita) in Genetically Different Pepper Lines (Capsicum annuum). European Journal of Plant Pathology. DOI 10.1007/s10658-009-9502-7.
- Turechek, W., Kousik, C.S., Adkins, S.T. 2010. Patterns of Virus Distribution in Single and Mixed Infections of Florida Watermelons. Phytopathology. doi:10.1094/PHYTO-01-10-0018.
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report Objectives (from AD-416) Objective 1. Develop improved resistance to root-knot nematodes in pepper and watermelon. Objective 2. Identify and develop improved resistance to diseases in cucurbits, e.g. powdery mildew, downy mildew, Phytophthora blight, and watermelon vine decline. Objective 3. Elucidate virulence parameters of selected plant pathogen populations and develop integrated methodologies for managing cucurbit diseases. Approach (from AD-416) Develop root-knot nematode-resistant sweet banana, sweet cherry, pimiento, and Cubanelle type peppers using backcross breeding procedures. Determine inheritance of resistance to root-knot nematodes (Meloidogyne incognita) in watermelon and identify molecular markers for root-knot nematode resistance genes in watermelon. Identify and develop improved resistance to Phytophthora capsici in watermelon and melon. Identify sources of resistance in watermelon plant introductions and develop management strategies for mature watermelon vine decline. Elucidate genetic variability in the downy mildew pathogen (Pseudoperenospora cubensis) isolated from watermelon and cucumber using conventional and molecular approaches. Significant Activities that Support Special Target Populations Completed programs to develop a root-knot nematode resistant habanero pepper breeding line and a root-knot nematode resistant pimento pepper cultivar. Studies on inheritance of resistance to southern root-knot nematode in watermelon were conducted. Field studies were conducted to determine usefulness of different wild watermelon, squash hybrid, and bottle gourd rootstocks for managing root-knot nematodes in grafted watermelon. The wild watermelon lines were moderately resistant to southern root-knot nematode and may be useful as rootstocks for grafted watermelon. Two greenhouse studies to determine usefulness of pepper genotypes differing in resistance to root-knot nematode and Phytophthora capsici for managing root-knot nematode and Phytophthora blight in pepper were completed. Wild bottle gourd (Lagenaria siceraria) germplasm lines were evaluated for reaction to southern root-knot nematode (Meloidogyne incognita) in greenhouse studies. Over 300 wild melon (Cucumis melo) germplasm lines were evaluated for resistance to crown rot caused by Phytophthora capsici and a number of resistant lines were identified. Over 1,700 wild watermelon germplasm lines were evaluated for resistance to Phytophthora capsici and several lines were identified as sources of resistance to Phytophthora foliar blight and fruit rot. Numerous wild bottle gourd (Lagenaria siceraria) germplasm lines with moderate to high resistance to Phytophthora crown rot and foliar blight were identified. Strategies to manage white-fly transmitted viral watermelon vine decline were developed and tested. A combination of silver plastic mulch and insecticide treatments to reduce whitefly populations helped manage viral watermelon vine decline. Several commercial bottle gourd cultivars which are used as rootstocks for grafted watermelon were identified as resistant to crown rot caused by Phytophthora capsici. Techniques were developed to quantify levels of Phytophthora capsici infection in crown tissue samples from commercial rootstocks for grafted watermelon. Isolates of Phytophthora capsici and downy mildew (Pseudoperonospora cubensis) were collected from the southeast US (Florida, Georgia, and South Carolina) and will be used to study genetic variability in these fungi within specific fields and within the southeastern US. Variability in Phytophthora capsici strains isolated from watermelon and other cucurbits in the southeast US was observed. This report also documents research conducted under subordinate project no. 6659-22000-020-04N, a non-funded cooperative agreement between ARS and University of Florida. Technology Transfer Number of New CRADAS: 1
Impacts
(N/A)
Publications
- Kousik, C.S., Adkins, S.T., Turechek, W., Roberts, P.D. 2009. Sources of Resistance in Watermelon Plant Introductions (PI) to Squash Vein Yellowing Virus (SqVYV), the Cause of Watermelon Vine decline in Florida. Plant Disease. 44(2):256-262.
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Progress 10/01/07 to 09/30/08
Outputs
Progress Report Objectives (from AD-416) Diseases and nematodes are major limitations in vegetable crop production in the U.S. There are many tools available to manage plant diseases. However, host-plant resistance is probably the easiest, most economical and environmentally friendly method for managing plant diseases and is readily acceptable to growers. Identification of host plant resistance to existing, new, and emerging pathogens in vegetable crops is critical for the development of efficient and effective disease management strategies that will reduce crop loss and pesticide use. Therefore, research under this project will identify new sources of resistance, determine inheritance of previously identified resistance, and develop molecular markers for important resistance genes that will facilitate their rapid incorporation into commercial cultivars. An understanding of variability in pathogen populations also is necessary to develop new vegetable cultivars with durable resistance. Thus, the proposed research will be accomplished through the following objectives: 1) Develop improved resistance to root-knot nematodes in pepper and watermelon, and 2) Identify and develop improved resistance to diseases in cucurbits and elucidate genetic variability in the cucurbit downy mildew pathogen. Successful attainment of these objectives will result in basic knowledge that facilitates development of new resistant germplasm, identification of molecular markers that will aid selection for resistance genes in breeding programs, and development of knowledge of pathogen variability. Approach (from AD-416) Develop root-knot nematode-resistant sweet banana, sweet cherry, pimiento, and Cubanelle type peppers using backcross breeding procedures. Determine inheritance of resistance to root-knot nematodes (Meloidogyne incognita) in watermelon and identify molecular markers for root-knot nematode resistance genes in watermelon. Identify and develop improved resistance to Phytophthora capsici in watermelon and melon. Identify sources of resistance in watermelon plant introductions and develop management strategies for mature watermelon vine decline. Elucidate genetic variability in the downy mildew pathogen (Pseudoperenospora cubensis) isolated from watermelon and cucumber using conventional and molecular approaches. Significant Activities that Support Special Target Populations Over 1,500 watermelon germplasm lines were evaluated for resistance to Phytophthora capsici. Several germplasm lines were identified as sources of resistance. Over 200 wild bottle gourd germplasm lines were evaluated for resistance to Phytophthora crown rot and foliar blight. Several moderately resistant germplasm lines were identified. Sweet pepper breeding lines (sweet cherry, Cubanelle, sweet banana, and pimiento) were evaluated for resistance to root-knot nematodes. Homozygous resistant lines were selected for further evaluation for horticultural characteristics and nematode resistance. Five watermelon populations (F1, F2, and F1 backcrosses to parents) were developed for use in studying inheritance of resistance to southern root-knot nematode and one inheritance study was conducted. Field studies to determine the usefulness of grafting watermelon on different squash hybrid, bottle gourd, and wild watermelon rootstocks for managing root-knot nematodes are in progress. Wild watermelon rootstocks developed by USDA scientists in Charleston, SC appear to be useful in managing root-knot nematodes in watermelon. However, squash hybrid and bottle gourd rootstocks were susceptible to root-knot nematodes. Greenhouse studies to determine usefulness of pepper genotypes differing in resistance to root-knot nematode and Phytophthora capsici for managing root-knot nematode and Phythophthora blight in pepper are underway. Strategies to manage watermelon vine decline were developed. A combination of silver mulch and insecticide treatments helped manage viral watermelon vine decline in Florida. This research contributes to National Program 303 Plant Diseases, Component 3: Plant Disease Resistance, Problem Statement 3B: Disease resistance in new germplasm and varieties; and Component 4: Biological and Cultural Strategies for Sustainable Disease Management, Problem Statement 4C: Application of sustainable disease management tools.
Impacts
(N/A)
Publications
- Kousik, C.S., Shepard, B.M., Hassell, R., Levi, A., Simmons, A.M. 2007. Potential Sources of Resistance to Broad Mites (Polyphagotarsonemus latus) in Watermelon Germplasm. HortScience. 42(7):1539-1544.
- Kousik, C.S., Keinath, A.P. 2008. First Report of Insensitivity to Cyazofamid among Isolates of Phytophthora capsici from the Southeastern United States. Plant Disease. 92:979.
- Adkins, S.T., Webb, S., Baker, C., Kousik, C.S. 2008. Squash vein yellowing virus detection using nested polymerase chain reaction demonstrates Momordica charantia is a reservoir host. Plant Disease. 92:1119-1123.
- Kousik, C.S., Levi, A., Ling, K., Wechter, W.P. 2008. Potential Sources of Resistance to Cucurbit Powdery Mildew (Podosphaera xanthii) in US Plant Introductions (PI) of Lagenaria Siceraria (bottle gourd). HortScience. 43(5):1359-1364
- Thies, J.A., Dickson, D.W., Fery, R.L. 2008. Stability of Resistance to Root-Knot Nematodes in 'Charleston Belle' and "Carolina Wonder' Bell Peppers in a Sub-Tropical Environment. HortScience. 43:188-190.
- Thies, J.A., Levi, A. 2007. Characterization of watermelon (citrullus lanatus var. citroides) germplasm for resistance to root-knot nematodes. Journal of Nematology. 42:1530-1533.
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