MELOIDOGYNE-JAVANICA DEVELOPMENT IN 3 CLOVER POPULATIONS

Root-knot nematodes (RKN), Meloidogyne spp., cause damage to red clove r (Trifolium pratense L.) which affects water and nutrient uptake and may predispose plants to other soil-borne pathogens. Penetration and d evelopment of M. javanica (Treub) Chitwood on three clover populations differing in resistance levels were evaluated in two greenhouse exper iments conducted during 1994 and 1995. The RKN susceptible red clover cultivar 'Kenstar', a red clover breeding selection designated FLMR6 w ith moderate RKN resistance, and a highly RKN resistant species T. sto loniferum Muhlenburg, running buffalo clover (RBC), were grown in Cone -tainers and inoculated with 450 second-stage juveniles (J2) 21 d afte r germination. Responses measured were numbers of J2, J3/J4 (third-sta ge or fourth-stage juvenile nematodes) and adults at 1, 2, 4, 8, 16, 2 4, 36, 48, 60, 80 (Exp. 2), and 120 (Exp. 1) days after inoculation (D AI). Fecundity was evaluated by counting number of egg-masses and tota l number of eggs per plant at 80 and 120 DAI. More J2 were found in Ke nstar roots than in FLMR6 and RBC roots at 4, 8, 36, 60, 80, and 120 D AI. More third or fourth stage juveniles (J3/J4) were found in Kenstar and FLMR6 roots than in RBC at 16, 24, 36, 48, 60, 80, and 120 DAI, a nd Kenstar J3/J4 numbers were higher than FLMR6 at 60 and 120 DAI. Few er adults were found in FLMR6 roots than in Kenstar at 36, 48, 60, 80, and 120 DAI, but adult numbers in RBC roots were significantly lower than in FLMR6 at these same dates. At 80 and 120 DAI, number of egg ma sses and total number of eggs were greater on Kenstar roots than on FL MR6, and total egg numbers on RBC were lower than on FLMR6. The resist ance mechanisms in FLMR6 and RBC hindered normal M. javanica developme nt because of a combination of slower maturation to later growth stage s and fewer J3/J4 maturing to adults, which produced fewer J2 for seco ndary infection.