TEMPERATURE EFFECTS ON RESISTANCE TO MELOIDOGYNE SPP IN EXCISED TOMATO ROOTS

Resistance to root-knot nematodes (Meloidogyne spp,) in tomato (Lycope rsicon esculentum Mill.) plants has been reported to break down at soi l temperatures >28C. We evaluated in vitro root explants of tomato het erozygous (Mimi), homozygous (MiMi) at the Mi locus, or lacking the Mi -1 gene for resistance to Meloidogyne incognita (Kofoid & White) Chitw ood and Meloidogyne arenaria (Neal) Chitwood at 28, 31, 34, and 37C. G enotypes Ace-55 UF and Rutgers, lacking the dominant allele, were susc eptible to M. incognita and M. arenaria at all temperatures. Genotypes possessing the dominant allele (heterozygous or homozygous) were equa lly resistant to both nematode species. The resistance level in these genotypes was maintained fully at 31C, partially maintained at 34C, an d lost at 37C. Resistance in the heat-tolerant Mi-heterozygous accessi on CLN 475-BC1F2-265-4-19 was not different from that of the heat-sens itive genotypes, As temperature increased, the genotypes differed in t heir sensitivity to resistance conferred by the Mi-1 locus.