Root-knot nematodes (Meloidogyne spp.) represent a major constraint for tomato production worldwide, causing significant yield losses. The most efficient and sustainable approach to nematode management is the deployment of resistant cultivars. The Mi-1 gene, particularly Mi-1.2, confers resistance to several Meloidogyne species and has become a key target for marker-assisted selection.
A total of 174 tomato accessions (169 mutant lines and 5 wild relatives) from the germplasm collection of the Federal Research Centre for Biological Plant Protection (Russia) were analyzed. Genomic DNA was extracted using optimized CTAB and SDS protocols. PCR was conducted with the Mi23 SCAR marker linked to Mi-1.2. Standard controls included resistant tomato DNA, the susceptible accession L25, and nuclease-free water. In heterogeneous cases, seedlings were regenerated in vitro on MS medium and tested individually.
The Mi-1 marker was detected in 12 accessions (6.9%). Resistant genotypes included mutant lines (MO122, MO137, MO324, MO417, MO580, MO628, MO753, GK1971, MO147) and wild relatives (L. glandulosum CGN-15803, L. chilense CGN-15877, L. peruvianum CGN-17047). The majority (162 accessions) lacked Mi-1. Some bulk seed samples produced both resistant (380 bp) and susceptible (~430 bp) fragments, indicating heterogeneity, which was confirmed in in vitro clones.
Mi-1-mediated resistance was rare (<7%) in the analyzed collection, but its presence in wild relatives highlights their role as valuable donors for breeding. The identification of heterogeneous accessions stresses the importance of complementing bulk screening with individual plant testing. The resistant accessions identified here can be employed in marker-assisted breeding to develop nematode-resistant tomato cultivars, contributing to sustainable crop production.
The authors thank the staff of the Laboratory of Biorational Protection Technologies (FGBNU FNTSBZR, Krasnodar, Russia) for technical support. The research was performed according to the State Assignment of the Ministry of Science and Higher Education of the Russian Federation within the framework of research project No. FGRN-2024-0001.
