Evaluation of Alysicarpus Germ Plasm for Resistance to Root-Knot Nematodes. G. R. Smith, Texas Agricultural Experiment Station, Texas A&M University Agricultural Research and Extension Center, Overtoil 75684. D. S. Wofford, Department of Agronomy, University of Florida, Gainesville 32611, and J. L. Starr, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, 77843. Plant Dis. 80:1147-1150. Accepted for publication 27 June 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1147.

Root-knot nematodes reproduce freely on alyceclover (Alysicarpus vaginalis) cv. Florida Common, limiting alyceclover establishment, forage production, and utility as a component of crop rotations. This study was conducted to identify alyceclover germ plasm with resistance to Meloidogyne hapla and M. incognita. Individual alyceclover seedlings planted in Cone-Tainers were infested with at least 2,300 eggs of M. hapla or M. incognita and grown for 77 days under glasshouse conditions at Overton, TX. Root systems were scored for galling on a 0 to 5 scale (0 = no galls, 1 = 1 to 2, 2 = 3 to 10, 3 = 11 to 30, 4 = 31 to 100, and 5 = more than 100 galls). Nematode egg production on selected alyceclover entries was evaluated and expressed as eggs per g of fresh root weight. Twenty-six alyceclover lines were evaluated in 1990, and five lines were reevaluated in 1991. Four alyceclover germ plasm groups were identified according to relative galling responses to M. hapla and M. incognita. Two groups were heavily galled by both nematodes, one group was not galled by M. incognita and was variable in response to M. hapla, and one group was galled by M. incognita and variable in galling response to M. hapla. Nematode egg production was often not related to gall response. M. hapla produced up lo 62,000 eggs per g of fresh root weight on plants of breeding line FL-3 with no visible galls. Breeding lines of alyceclover were identified that contained individual plants resistant to either nematode species, but no single alyceclover line had resistance to both nematodes.

Keyword(s): screening