GENETIC IMPROVEMENT OF FRUIT QUALITY AND ADAPTATION TRAITS OF EXOTIC TOMATO VARIETIES IN A HUMID TROPICAL ENVIRONMENT
The experiment was conducted at the Teaching and Research Farm and Laboratory, of the Department of Crop Science, University of Nigeria, Nsukka to: (i) determine the fruit characteristics, agronomic, yield and yield component trait performances of seven tomato varieties; (ii) produce and select genotypes that combine adaptable and qualitative traits of interest; (iii) determine the inheritance pattern of the crop traits; (iv) estimate heterosis and heritability in the hybrids, and (v) determine the combining ability of the selected parents and their hybrids. The experimental materials used were the seeds of six varieties of tomato including; Grosso (G), Insulata (In), Petomech (P), Chico ІІI, Super Roma, and Piccolo obtained from Italy and Lycopersicon pimpinellifolium; wild(W) obtained from Mbu in Isi-uzo Local Government Area of Enugu state. General combining ability of the parents and the specific combining ability of the hybrids were estimated using Griffings’ model 1 method 2 in a 4 x 4 diallel cross. Chi- square statistic was used to test for the inheritance pattern of these traits. The wild parent was significantly (p = 0.05) higher in number of flowers/truss (10.07), fruits/truss (7.33), fruits/plant (621), and fruit yield (11.96 tons/ha) than the other parents. Petomech was significantly (p = 0.05) higher in pericarp thickness (5.35 mm), days to first fruit spoilage (24), 50% fruit spoilage (34) and 100% fruit spoilage (65) than the other parents. Grosso showed significantly (p = 0.05) higher average fruit weight (67g) and fruit length (9.69 cm) than the other parents. The cross, W x P was significantly (P = 0.05) higher than other hybrids and the parents in fruit yield (27.41 tons/ha) and number of fruits/truss (8.43). The cross, In x P was significantly (P = 0.05) higher than the other crosses and hybrids in days to first fruit spoilage (46). The cross, W x G was also significantly higher than the other crosses and the parents in days to 100% fruit spoilage (86) and it was statistically similar to Petomech. The rwild was the best general combiner in days to flowering (2.47), fruiting (2.71), ripening (2.61) and fruit yield (9.22). Petomech was the best general combiner in days to first fruit spoilage, 50% fruit spoilage and 100% fruit spoilage (5.08, 4.23 and 9.77, respectively. The cross, W x P was the best specific combiner in number of flowers/ truss (1.38), fruits/truss (1.91), fruits/plant (79.85), and fruit yield (21.67). The cross, In x P was the best specific combiner in pericarp thickness (1.77 mm). Highest better parent heterosis (BPH) was recorded in W x P for number of fruits/truss (12.94 %) and fruit yield (206.04 %). Highest BPH was also recorded in W x G for days to first fruit spoilage (233.65), 50 % spoilage (225.15 %) and 100% spoilage (262.87 %). Hybrids having wild as one of its parent had low disease incidence and severity at fruit ripening. W x P had significantly higher phenol content (4.29 mg/100g) and flavonoid (2.62 %) content than all the parents and the other hybrids.