Identification of a tomato cultivar resistant to root-knot nematode (Meloidogyne spp.) : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

Tomato is a vegetable/fruit consumed by people globally. Root-knot nematode (RKN) is one of the most important plant-parasitic nematodes which causes significant yield loss in tomato and many other agriculturally important crops worldwide. A 45-day study was conducted in a glasshouse environment to test the host status of five common tomato cultivars to RKN. The experiment was conducted with eight replicates of five cultivars, with and without exposure to RKNs. The influence of RKN to inoculated plants were compared with uninoculated control plants by measuring the (i) plant height and the number of branches, measured weekly, (ii) Shoot and root biomass, (iii) root gall index, and (iv) the number of RKN eggs on each root system measured on days 28 (five replicates) and 45 (three replicates). The results showed that four of the cultivars (1, 2, 4, and 5) tested were susceptible to RKN, and all their development factors were affected by the RKNs and clearly showed root-knots and nematode eggs in the root systems. Among these, one cultivar was the most susceptible and was significantly damaged by the RKN. Another cultivar was the best host for RKN reproduction. In contrast, in the test plants of cultivar 3 (C3), RKN and RKN eggs in the root system were absent. The plant height, number of branches and root biomass were higher in the C3 test plants compared with the respective controls. All these indices indicated that the cultivar 3 was fully resistant to RKNs. A surprising result was that the physical development of plants from this cultivar was better in the presence of the RKN than in the corresponding uninoculated control. The increase in biomass of the cultivar 3 even in root-knot infested soil is a new finding. This result would be useful for both commercial tomato farmers and home gardeners since they would be able to plant this cultivar in heavily RKN infested soils. These findings will enable growers to utilize limited to no nematicides and thereby promoting the clean green image of NZ and thus boosting the export of NZ trade even further.