Influence Of Plant Resistance And Nematicides On Growth And Yield Of Tomato (Lycopersicon Esculentum) And On Population Dynamics Of Root-Knot Nematodes (Meloidogyne Incognita With An Associa

Abstract

Both growth chamber and field experiments were conducted to study the influence of resistant tomato cultivars and applications of Vorlex (DD MENCS) on the population dynamics of root knot nematode species and growth and yield of subsequent crops of a susceptible tomato 3 3 cultivar. Four initial M. incognita inoculum densities (10 , 5 x 10 , 104 and 105 eggs/500 orT of soil) and two initial M. hapla inoculum o o o ^ densities (10 and 5 x 10 eggs/500 cm of soil) were used. Two resistant tomato cultivars (Nematex and VFN-8) and a susceptible cultivar (Rutgers) were used in studies with M. incognita. A resistant tomato species (Lycopersicon peruviarium), partially resistant (VFN-8) and susceptible (Rutgers) tomato cultivars were used in studies with M. hapla. Field experiments were conducted with M. hapla using the same initial inoculum densities of the nematode and the same tomato cultivars as in the growth chamber experiments. Vorlex was used at 22.5, 45 and 90 L/ha in growth chamber studies and at 45 L/ha in field studies. In the growth chamber studies both resistant and susceptible tomato plants were inoculated with the different initial inoculum density (P.) levels of the Meloidogyne sp. Six weeks after inoculation, plant tops were removed and the nematode population was determined. Vorlex was applied to seven replications of each treatment. An equal number of replicates 6 7 were left untreated. Four weeks after fumigation, pots were replanted with seedlings of tl^e susceptible cultivar and grown for 6 wks. The population of the nematode was determined and pots were immediately replanted with seedlings of the susceptible cultivar. Three more successive plantings of Rutgers were made before the experiment was terminated. Continuous cropping of a susceptible cultivar in infested soil greatly increased the nematode population and decreased the growth of plants. Resistant plants and applications of Vorlex to infested soil had similar effects in reducing nematode populations. Resistant cultivars alone or Vorlex alone resulted in nematode reduction that permitted one (at highest P ^ ) and two to three (at lowest P^s) plantings of susceptible crops to be grown before the nematode population returned to a damaging level. Applications of Vorlex after growing a resistant tomato cultivar resulted in sufficient reductions of the nematode populations so that at least three successive plantings of the susceptible cultivar could be grown before the population reached a damaging level. In field experiments, applications of Vorlex significantly increased marketable yields of the susceptible tomatoes. A further increase in yield of Rutgers was obtained when Vorlex was applied to infested soil that had been previously planted to resistant tomatoes before growing the susceptible cultivar. Fewer nematodes were recovered from the infested soil at the end of the second season although heavy galling was observed on infected roots.