EFFECTS OF ROOT-KNOT NEMATODES ON RED-CLOVER GROWN IN MICROPLOTS

Root-knot nematodes (Meloidogyne spp.) damage red clover (Trifolium pr atense L.) in the southeastern USA. Their effects on yields of the sus ceptible cv., 'Kenstar', and a resistant breeding Line, FLMR6, were ev aluated in microplot field studies during the 1993-94 and 1994-95 grow ing seasons. In 1993-94, plants were evaluated for response to presenc e or absence of a mixture of M. arenaria (Neal) Chitwood, M. javanica (Treub) Chitwood, and M. hapla Chitwood, and in 1994-95 for response t o M. javanica. Over both nematode treatments, FLMR6 produced almost tw ice as much dry matter field as Kenstar at the first harvest of 1993-9 4 and during the first three harvests of 1994-95. Dry matter yield of FLMR6 from inoculated and uninoculated plots was not different at any harvest date. During the 1993-94 growing season, inoculated Kenstar pl ants produced less dry matter yield than uninoculated plants at the th ird harvest date, and most inoculated plants did not survive the growi ng season. In 1995, inoculated Kenstar plants produced approximately 5 0% less dry matter yield than uninoculated plants at the second and th ird harvest dates and for the seasonal total. Such reduction suggests that root-knot nematode contributed to decreased plant growth. FLMR6 p lants flowered earlier than Kenstar plants in both years, due to selec tion under Florida conditions. There was no effect of nematode treatme nt on FLMR6 flowering response. Inoculated Kenstar plants were less ma ture than inoculated FLMR6 plants at the last two harvests of 1994 and at the second and third harvests of 1995. Soil samples from Kenstar p lots contained 284 second-stage juveniles per 100 cm(3) soil compared to 2 per 100 cm(3) from FLMR6 plots. The use of the resistant line, FL MR6, should be evaluated as a cover crop for root-knot nematode manage ment in crop rotations.