The host suitability of 21 local, commercial tomato varieties were evaluated in concurrent greenhouse trials for resistance to Meloidogyne incognita race 2 and Meloidogyne javanica, respectively. M. incognita race-2-resistance identified in variety ‘Rhapsody’ during the latter study was subsequently verified in a follow-up microplot trial using differential initial population (Pi) densities and as well as in a field trial with four soil amendments. Substantial variation existed among the tomato varieties in the greenhouse screening with regard to resistance to the respective root-knot nematode species. Comparison of the different indicators of resistance used for the two species showed that labelling of specific varieties as resistant should not only be based on one criterium, since it could be insufficient. Strong non-linear relationships were shown in the microplot trial between Pi and Pf in the roots of both tomato varieties but nematode reproduction was poor on the resistant ‘Rhapsody’. Significantly lower Pf in roots and J2 in soil was obtained for ‘Rhapsody’ compared to the susceptible Moneymaker. In the soil-amendment field trial, ‘Rhapsody’ also maintained significantly lower M. incognita numbers compared to ‘Moneymaker’ in all treatments. These results confirm the superior resistance of ‘Rhapsody’ to local M. incognita race-2 populations used in this study. More frequent and extensive screenings of commercial tomato material are recommended in order to provide resource-poor producers with better options for improved and sustainable yields.
Key words: Initial densities, Meloidogyne incognita, Meloidogyne javanica, resistance, susceptible, root-knot nematodes, screening, tomato, varieties.
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