The tomato Rme1 locus is required for Mi‐1‐mediated resistance to root‐knot nematodes and the potato aphid

Abstract

SummaryThe tomato Mi-1 gene confers resistance against root-knot nematodes (Meloidogyne spp.) and a biotype of the potato aphid (Macrosiphum euphorbiae). Four mutagenized Mi-1/Mi-1 tomato populations were generated and screened for altered root-knot nematode resistance. Four independent mutants belonging to two phenotypic classes were isolated. One mutant was chosen for further analyzes; rme1 (for resistance to Meloidogyne) exhibited levels of infection comparable with those found on susceptible controls. Molecular and genetic data con®rmed that rme1 has a single recessive mutation in a locus different from Mi-1. Cross-sections through galls formed by feeding nematodes on rme1 roots were identical to sections from galls of susceptible tomato roots. In addition to nematode susceptibility, infestation of rme1 plants with the potato aphid showed that this mutation also abolished aphid resistance. To determine whether Rme1 functions in a general disease-resistance pathway, the response against Fusarium oxysporum f.sp. lycopersici race 2, mediated by the I-2 resistance gene, was studied. Both rme1 and the wild type plants were equally resistant to the fungal pathogen. These results indicate that Rme1 does not play a general role in disease resistance but may be speci®c for Mi-1-mediated resistance.

Expression profile of jasmonic acid-induced genes and the induced resistance against the root-knot nematode (Meloidogyne incognita) in tomato plants (Solanum lycopersicum) after foliar treatment with methyl jasmonate

“…A resistance gene against RKN, Mi-1.2, is not transcriptionally regulated but speculated to be post-transcriptionally regulated (Martinez de Ilarduya et al, 2001). Our results also supported this suggestion.…”

Lotus japonicus: A New Model to Study Root-Parasitic Nematodes

“…The choice of growth medium for root-nematode experiments is important, as soil texture affects the severity of root infestation. Sandy loams and coarser textured soils are more conducive to infection in the field than heavy or clay soils (Sasser 1954, Raski and Johnson 1959, Thomason and Lear 1959, and researchers typically use coarse textured soils such as river bottom sand for RKN studies in the greenhouse (de Ilarduya et al 2001, Ammiraju et al 2003. However, unlike tomato, we found that Lotus roots develop poorly in sand alone, and so we tested various growth media for nematode infection.…”

How Durable is Root Knot Nematode Resistance in Tomato?

“…In contrast, the occurrence of susceptibility while there is no guarding or no R gene present in the plant targeted for the Avr genes, often resulting in a disease. For example rme1, a recessive gene resistance to Meloidogyne species, which is unlinked to Mi-1 (de Ilarduya et al 2001), and compromised Mi-1-mediated resistance. Since the gene product of RME1 still unknown; the authors guessed that it may be a protein kinase performing either upstream of Mi-1 or at the initial stage of the signal transduction pathway.…”