Inheritance of Root-knot Resistance in the Cowpea (Vigna unguiculata (L.) Walp.)1

Abstract The inheritance of resistance in cowpea to root knot incited by the root-knot nematodes Meloidogyne incognita (Kofoid & White) Chitwood, M. javanica (Treub.) Chitwood, and M. hapla Chitwood was determined in 3 separate greenhouse experiments. Each seed was inoculated at planting with about 2,000 eggs of the appropriate Meloidogyne species. In Experiment I, plants of parental, F 1 , F 2 , and F 1 × P 1 and F 1 × P 2 backcross generations of a cross between the resistant cultivar ‘Mississippi Silver’ and the susceptible breeding line CR 18-13-1 were tested for reaction to M. incognita. In Experiment II, plants of parental, some F 1 , and all F 2 generations of a series of crosses involving CR 18-13-1 and the resistant lines ‘Colossus’, ‘Mississippi Silver’, ‘Iron’, and PI 353383 were evaluated for resistance to M. incognita. In Experiment III, plants of parental, F 1 , and 30 randomly chosen F 3 lines of the ‘Mississippi Silver’ × CR 18-13-1 cross were evaluated in separate tests for reaction to M. incognita, M. javanica, and M. hapla. A single dominant gene determined resistance to M. incognita, M. javanica, and M. hapla; the same gene governed resistance in ‘Colossus’, ‘Mississippi Silver’, ‘Iron’, and PI 353383. The gene conditioned a high level of resistance, but it did not confer immunity. Roots of many resistant plants exhibited limited galling and supported some egg production by the parasites. We propose that this gene be designated Root-knot resistance and symbolized Rk .