Variability in infection and reproduction of Meloidogyne javanica on tomato rootstocks with the Mi resistance gene

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The response of 10 commercial or experimental tomato rootstocks with the Mi resistance gene to an initial inoculum of a Mi-avirulent population of Meloidogyne javanica was determined in pot tests conducted in spring and summer. In a field test, the rootstocks were subjected to continuous exposure to high initial population densities (2050 ± 900 second-stage juveniles (J2) per 250 cm3 soil) of the nematode. The presence of the Mi locus in the resistant rootstocks and cultivars was confirmed using the PCR co-dominant markers REX-1 and Mi23. Nematode infectivity (egg masses) and reproduction (eggs g−1 root) were highly variable in the spring tests. Rootstocks PG76, Gladiator and MKT-410 consistently responded as highly resistant, with nematode multiplication rate (Pf/Pi) < 1 and reproduction index (RI) < 10%, and they were as efficient as standard resistant tomato cultivars at nematode suppression. The relative resistance levels of rootstocks Brigeor, 42851, 43965, Big Power and He-Man varied depending on the susceptible standard used for reference or the duration of the test. Rootstocks Beaufort and Maxifort were susceptible to M. javanica (Pf/Pi > 50 and RI > 50%). Rootstocks PG76 and He-Man, and the resistant tomato cv. Caramba showed high levels of resistance in the test conducted in summer, whereas MKT-410 and 42851 and the resistant tomato cv. Monika were moderately resistant. In the field, seven rootstocks showed high levels of resistance and one (He-Man) showed an intermediate level, whereas Beaufort and Maxifort were susceptible.

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