ABSTRACT

An effort to obtain a tomato cultivar that would adapt to high temperature and high humidity condition in the southern part of Nigeria in order to increase tomato yield in this part of the country has been in progress for the past nine years (2000-2008).The research was carried out at the Faculty of Agriculture Research Farm, University of Nigeria, Nsukka located in the derived savanna zone latitude 0.6o52, N, longitude 07o 24, E, 447.26 m altitude. Three cultivated tomato varieties (Solanum lycopersicon) Roma
VF, Tropica (Derica), Nsukka Local and a wild relative, Solanum pimpinellifolium and their progenies were used in the study for the development of a novel tomato cultivar for commercial production. The results of the frequency distributions of the parents and progenies showed continuous variation in fruit size thus suggesting fruit size in tomato as a polygenic trait that is controlled by multiplicative gene action.
Genetic progress made over the generations equally revealed that highest genetic gain was obtained at the F11 generation over all the generations studied with a decline at the F12 generation.

Correlation coefficients revealed positive associations between
yield and all the yield components in all the generations. Path coefficient analysis showed that number of flowers per plant had the highest direct effect on yield. Principal component analysis had number of flowers per plant and fruits per plant as the highest weighting factors. Genotype by trait (GT) biplot analysis revealed that Roma x Wild out performed the other hybrids for the yield traits measured. The results of different statistical analyses performed rated Roma x Wild as the best genotype among the three cross combinations (Roma x Wild, Local x Wild and Tropica x Wild) that will replace the original parents for adaptability under high humidity environment. Among the agronomic traits studied, number of flowers per plant and number of fruits per plant were of considerable importance, thus selection based on these traits will enhance yield in tomato. The genotype (Roma x Wild) gave higher yield and was more tolerant to high humidity conditions.