Evaluation of some Tomato Genotypes for Nematode Resistance and Detection of the Mi-1.2 Resistance Gene

Abstract

Response of fourteen tomato genotypesfrom different geographical regions to root-knot nematodes (RKN; Meloidogyne spp .) was evaluated for two seasons under greenhouse conditions. Two PCR-based markers (Mi-23 and REX-1) were used for the detection of the RKN resistance gene (Mi-1.2) in the tested genotypes. The results showed a wide variation among tested tomato genotypes in their responses to RKNs. Highly significant differences were observed among tested genotypes for gall index and egg masses per root system. Based on nematode bioassay, the tomato genotype Strain B F1 was highly resistant to RKN and ranked in top of resistant genotypes. Floradade and VF145-B were resistant, Castlerock, Peto86 and Qaha were moderately resistant, Super strain B, E115, Super Marmande, M82 and Edkawy were susceptible, and E37, E40 and Giza-80 were highly susceptible to RKN. Molecular analysis with Mi23 and REX-1 markers indicated a heterozygous state (Mi/mi) of Mi-1.2 gene for Strain B F1; meanwhile, the remaining genotypes displayed a homozygous recessive state (mi/mi). These finding suggested that Strain B F1 could be used to develop new tomato cultivars resistant to RKN through tomato breeding programs. In addition, the results suggested that tomato genotypes that were identified in the present study as homozygous recessive (mi/mi) for the Mi-1.2 gene and considered as resistant or moderately resistant may possess other genes controlling RKN resistance. However, further studies are still needed to determine these genes that control the resistance to RKNs in tomatoes.