YIELD AND QUALITY EVALUATIONS ON A PAIR OF PROCESSING TOMATO LINES NEARLY ISOGENIC FOR THE TM2(A) GENE FOR RESISTANCE TO THE TOBACCO MOSAIC-VIRUS

A pair of processing tomato (Lycopersicon esculentum Mill.) lines, nea rly isogenic for the Tm-2(a) gene for resistance to tobacco mosaic vir us, were grown in replicated trials under commercial production condit ions in five locations worldwide. The lines were evaluated for 17 proc essing traits including fruit yield, size, soluble solids concentratio n, color, firmness, and viscosity. Eight of those traits differed sign ificantly among the nearly-isogenic lines (NILs). Most notably, the NI L heterozygous for Tm-2(a) yielded, on average, 16% more than the NIL homozygous for the susceptible allele and 33% more than the ML homozyg ous for Tm-2(a). Viscosity was lower in the heterozygous NIL and the h omozygous and heterozygous resistant NILs had softer fruit with larger stem scars compared to the homozygous susceptible NIL. These results indicate the presence of the Tm-2(a) locus affects many traits of impo rtance for processing tomatoes and may be used, in the heterozygous st ate, to significantly increase yield. Whether the observed effects are due to the Tm-2(a) gene itself or genes associated via linkage drag c ould not be determined.