Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/19/2004
Publication Date: 5/1/2006
Citation: Gillaspie Jr, A.G. 2006. New method for screening cowpea germplasm for resistance to cucumber mosaic virus. Plant Disease. 90:611-614. Interpretive Summary: A new method for screening for resistance to Cucumber mosaic virus (CMV) was developed using a newly discovered CMV resistant cowpea line to compare with greenhouse and field data. This method depends on finding the correct inoculums dilution to give infection results in the greenhouse that are similar to those obtained by natural infection in the field. Then, the planting of the test line seeds must be planned so that the virus source is not introduced until the test plants ate large enough. CMV is a component of cowpea stunt which is the most serious disease of cowpeas in the U.S. This method will allow the discovery of new and better germplasm for resistant cultivars of cowpeas to increase production. The final results will help growers as well as consumers.
Technical Abstract: Utilizing the Cucumber mosaic virus (CMV)-resistant cowpea germplasm line, GC-86L-98, a new method of screening for resistance in the greenhouse followed by field screening was developed. A uniform source of CMV inoculum (freeze-dried infected cowpea tissue) was diluted to provide an infection-rate in GC-86L-98 similar to that observed under field conditions. Plants of test lines were mechanically inoculated with this standard inoculum rate and assessed under greenhouse conditions. Lines considered equivalent in infection percentage with GC-86L-98 were then evaluated in field tests. Test line plants were exposed to virus from spreader-row plants when the plants were at the first or second trifoliolate leaf stage and then leaf samples were read by direct antigen coating-ELISA. Lines with infectioin percentages similar to or lower than the resistant control were considered resistant. A new line (PI 441917) with CMV resistance and several lines with Blackeye cowpea mosaic rirus resistance were found. Newly discovered CMV-resistant lines will help to control the serious cowpea stunt disease caused by syngergism of the two viruses.