Genetic Basis of the Epidemiologic effects of Resistance to Meloidogyne incognita in the Tomato Cultivar Small Fry.

The genetic nature of resistance and its epidemiologic effects on two Meloidogyne incognita populations were assessed in the F hybrid tomato cv. Small Fry. The progeny of a Small Fry x Small Fry cross segregated in a 3:1 resistant:susceptible ratio, indicating the presence of a single, completely dominant resistance gene (LMiR) in Small Fry. In a subsequent experiment, infection frequency and the rate of development of primary infection on resistant Small Fry x Small Fry segregates were compared to those on susceptible segregates and the susceptible cultivar Rutgers. Suppression in both infection frequency and rate of development of primary infection was entirely attributable to gene LMiR. A single egg-mass population of M. incognita propagated for 12 generations on Small Fry showed an increased ability over the wild type population to parasitize plants containing the LMiR gene but failed to completely overcome resistance. The relationship of this phenomenon to the genetics of the Lycopersicon esculentum-M. incognita interaction is discussed.