Yield and evaluation of F₁ tomato hybrids incorporating the non-ripening nor gene

Abstract

F1 hybrids of the nor non-ripening mutant tomato in different genotypic backgrounds were evaluated between 1978-81. The nor gene in the heterozygous condition delayed the start of ripening by a few days, increased the interval between breaker and the table ripe stage to 10 d at 21¦C compared with 6 d for fixed cultivars and increased the storage life of ripe fruit at 21¦C by about 50%. The retention of firmness by ripe fruit of the hybrids was affected by parental genotype. Fruit of some hybrids was firmer or as firm as fruit of the hard commercial Flora-Dade but others were much softer. A major problem with fruit of F1 nor hybrids was poor colour development. The fruit ripened to an orange-red colour, and strains with green shoulders developed an unattractive yellow on the shoulders. This deficiency was most pronounced in fruit picked before the appearance of red colour. The best hybrid found in this study was 75T10-1 x nor backcross 4 or 5 Heinz 1350. Fruit size, soluble solids, pH, titratable acidity, total ascorbic acid levels and acceptability except external colour of table ripe fruit appeared to be influenced by the parental genotype rather than by the nor gene. Since there were marked differences between hybrids with different genotypic backgrounds, it should be possible to breed nor hybrids with improved colour and firmness.