Stacking of mutant genes in the development of “purple tomato” rich in both lycopene and anthocyanin contents

A conventional breeding approach was framed to combine lycopene enhancing mutant gene, dg or hp-2dg and anthocyanin synthesizing gene, Aft in one genotype in maximizing the accumulation of both lycopene and anthocyanin pigment in tomato fruit. This breeding scheme involves one crossing, Alisa Craig AftAft × BCT-115 dgdg followed by two selfings for selection of the desirable double homozygous genotype, AftAft dgdg, the “Purple tomato” based on morphological marker characters conditioned by two genes, dark green fruit of dgdg due to very high total chlorophyll content (18.19 mg/100 g fresh weight) and purple colour for anthocyanin pigment of Aft- gene. Lycopene content in ripe fruits of BCT-115 dgdg (6.22 mg/100 g fresh weight) was 62.41% higher compared to Alisa Craig Aft/Aft while that of Alisa Craig AftAft had high anthocyanin content (14.51 mg/ 100 g fresh weight) contrary to nil in BCT 115 dgdg. Segregation pattern confirmed the expected 3:1 ratio for single dominant Aft gene and 1:3 ratio for single recessive dg gene. The F2 segregates could be grouped into 5 phenotypic classes in the ratio of 6:3:3:3:1 instead of usual 9:3:3:1 in digenic segregation due to variable expression of anthocyanin in the homozygous (Aft Aft) and heterozygous (Aft aft) genotype. Of the selfed progeny of the 34 desirable F2 segregates (dark green fruit with intense anthocyanin pigmentation) clustered in the Group-1 family (F3 population), 9 segregates bred true confirming the presence of two targeted genes in homozygous condition, AftAft dgdg, the “Purple tomato line”. This breeding approach proved to be a viable option to develop a new variety “Purple tomato” with unique combination of high lycopene (6.13 mg/100 g fresh weight), anthocyanin (20.73 mg/100 g fresh weight) and ascorbic acid (31.56 mg/100 g fresh weight) contents.