Authors: AMAL ABD EL-AZIZ, A. A. GUIRGIS, T. M. ROSHDY, M. A. KHEDER
Three genes Tm-1, Tm-2 and Tm- 22 are known to confer resistance to tomato mosaic virus (ToMV) in tomato (Lycopersicon esculentum Mill) plants. A polymerase chain reaction (PCR) based codominant marker was developed to be linked to these genes (Tm-1, Tm-2 and Tm-22) using sequence characterized amplified region (SCAR) markers. The polymorphic markers co-segregated with susceptibility or resistance, as determined by biological assays for ToMV resistance. Accordingly, the homozygous genotype will show the intact fragment (950 bp) alone the heterozygous; will show the intact fragment in addition to several smaller fragments (150-800 bp) and the homozygous recessive will show only the smaller fragments. This method enables the distinction of homozygous and heterozygous individual plants in segregating populations for Tm-22, and provides a convenient and rapid assay for mosaic virus resistance to be used in tomato breeding programs and hybrid seed production.