Meloidogyne javanica Development in Three Clover Populations

Abstract

Root‐knot nematodes (RKN), Meloidogyne spp., cause damage to red clover (Trifolium pratense L.) which affects water and nutrient uptake and may predispose plants to other soil‐borne pathogens. Penetration and development of M. javanica (Treub) Chitwood three clover populations differing in resistance levels were evaluated in two greenhouse experiments conducted during 1994 and 1995. The RKN susceptible red clover cultivar ‘Kenstar’, a red clover breeding selection designated FLMR6 with moderate RKN resistance, and a highly RKN resistant species T. stoloniferum Mublenburg, running buffalo clover (RBC), were grown in Cone‐tainers and inoculated with 450 second‐stage juveniles (J2) 21 d after germination. Responses measured were numbers of J2, J3/J4 (third‐stage or fourth‐stage juvenile nematodes) and adults at 1, 2, 4, 8, 16, 24, 36, 48, 60, 80 (Exp. 2), and 120 (Exp. 1) days after inoculation (DAI). Fecundity was evaluated by counting number of egg‐masses and total number of eggs per plant at 80 and 120 DAI. More J2 were found in Kenstar roots than in FLMR6 and RBC roots at 4, 8, 36, 60, 80, and 120 DAI. More third or fourth stage juveniles (J3/J4) were found Kenstar and FLMR6 roots than in RBC at 16, 24, 36, 48, 60, 80, and 120 DAI, and Kenstar J3/J4 numbers were higher than FLMR6 at 60 and 120 DAI. Fewer adults were found in FLMR6 roots than in Kenstar at 36, 48, 60, 80, and 120 DAI, but adult numbers in RBC roots were signiftcantly lower than in FLMR6 at these same dates. At 80 and 120 DAI, number of egg masses and total number of eggs were greater on Kenstar roots than on FLMR6a, nd total egg numbers on RBC were lower than on FLMR6. The resistance mechanisms in FLMR6 and RBC hindered normal M. javanica development because of a combination of slower maturation to later growth stages and fewer J3/J4 maturing to adults, which produced fewer J2 for secondary infection.