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Variability in Reproduction of Isolates of Meloidogyne incognita and M. javanica on Resistant Tomato Genotypes. P. A. Roberts, Extension Nematologist, University of California, Kearney Agricultural Center, Parlier 93648. I. J. Thomason, Professor of Nematology and Plant Pathology, University of California, Riverside 92521. Plant Dis. 70:547-551. Accepted for publication 14 November 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-547.

Variability in reproduction and root galling of eight isolates of Meloidogyne incognita and seven isolates of M. javanica on Mi gene-based resistant tomato (Lycopersicon esculentum) was studied in greenhouse experiments. Fresh-market cultivars Castlemart (susceptible); Valerie, Royal Flush, Jackpot, Super Fantastic, Better Boy, Cavalier, President, Carmen, and Duchess (all resistant); and processing tomato cultivars and advanced lines UC82 (susceptible) and VFN8, GS27, Hy9889, XPH671, CX8202, MOX3076, and MOX3078 (all resistant) were tested. The M. incognita isolates did not vary in pathogenicity. The resistant tomatoes, except Valerie, were highly resistant to M. incognita, supporting egg production in most combinations at less than 2% of that on susceptible controls. Valerie was a mixture of fully susceptible and highly resistant individual plants, indicating segregation for resistance in this cultivar. Five M. javanica isolates also reproduced on resistant tomatoes, except Valerie, at less than 2% of their reproduction on susceptible controls; some of these isolates reproduced more on CX8202 and MOX3078 than on other resistant tomatoes. However, two additional M. javanica isolates reproduced more than the other isolates on resistant cultivars and lines; their egg production varied significantly (P ≤0.05) with cultivar from low (highly resistant) to intermediate (moderately resistant) compared with that on susceptible controls for each isolate. No resistant tomato cultivar or line was immune to any nematode isolate.

Keyword(s): root-knot nematodes.