Influence Of Plant Resistence And Nematicides On Growth And Yield Of Tomato (Lycopersicon Esculentum) And On Population Dynamics Of Root-Knot Nematodes (Meloidogyne Incognita And Meloidogyne Hapla ) With An Asociated Study Rooted-Knot Nematode Resistance In Lettuce (Lactuca Species)

Abstract

The influence of resistant tomato cultivars, chemical applications and both in combination on the population dynamics of root-knot nematode species (Meloidogyne incognita and Meloidogyne hap!a) and on growth and yield of subsequent susceptible tomato crops was studied. Both growth chamber and field experiments were conducted. High initial inoculum densities (P.) of root knot nematode species reduced growth but had slight or no effect on growth of resistant cultivars. Nematode reproduction was positively correlated with the initial inoculum density. M. incognita was more virulent than M. hapla on the susceptible (Rutgers) tomato. VFN-8 was found to be partially resistant to M. hapla. Continuous cropping of a susceptible cultivar in infested soil greatly increased the nematode population and decreased the growth of susceptible plants. Resistant cultivars or applications of Vorlex alone permitted one (at highest P.'s) and two to three (at lowest P^s) susceptible crops to be grown before the nematode population reached a plant damaging level. Applications of Vorlex after a crop of resistant cultivar resulted in sufficient reductions of the nematode populations that at least three successive crops of the susceptible cultivar could be grown before the population reached a plant damaging level. A lower dosage of chemical was needed when used in combination with a resistant cultivar to control root knot nematodes. In field experiments, Vorlex significantly increased marketable yields of tomatoes. Further increases in marketable yields of Rutgers tomato were obtained when Vorlex was applied to infested soil that had been previously planted to a resistant cultivar. In another study, only the resistant tomato seedlings when transplanted after 2 wk from highly infested to noninfested soil, grew as well as those transplanted from noninfested to noninfested soil. In the third study, none of either the Lactuca species or the lettuce breeding lines tested were resistant to M. incognita and M. javanica. JL. saliqna and L.. dregeana were resistant to a greenhouse population of M. hapla but were susceptible to a field population of M. hapla.