RFLP markers linked to the root knot nematode resistance gene Mi in tomato

Area of Science:

• Plant genetics
• Crop science
• Molecular biology

Background:

• Root-knot nematodes (Meloidogyne spp.) cause significant damage to cultivated tomatoes (Lycopersicon esculentum).
• The Mi gene from wild tomato (Lycopersicon peruvianum) confers broad-spectrum resistance to these nematodes.
• Introgression of the Mi gene into cultivated tomato varieties has been challenging due to linkage drag and marker availability.

Purpose of the Study:

• To identify and characterize molecular markers linked to the Mi gene for efficient introgression and breeding.
• To develop tools for distinguishing nematode-resistant and susceptible tomato genotypes.

Main Methods:

• Used nearly isogenic lines differing in the chromosomal region containing Mi and Aps-1 loci.
• Employed Restriction Fragment Length Polymorphism (RFLP) analysis to identify markers.
• Analyzed 51 Lycopersicon esculentum genotypes to validate marker linkage.

Main Results:

• Identified two RFLP markers, GP79 and H6A2c2, within the introgressed region.
• GP79 marker is tightly linked to the Mi gene, enabling differentiation of resistant and susceptible genotypes regardless of Aps-1 alleles.
• H6A2c2 marker is linked to the Aps-1 locus, distinguishing between Lycopersicon peruvianum and Lycopersicon esculentum alleles.

Conclusions:

• The identified RFLP markers, particularly GP79, are valuable tools for marker-assisted selection in breeding nematode-resistant tomatoes.
• Combined use of GP79 and H6A2c2 can facilitate precise introgression of the Mi gene and improve breeding efficiency.
• These markers offer a robust method for accelerating the development of nematode-resistant tomato cultivars.