Abstract
The present research was prompted by lack of improved tomato cultivars adapted to the humid tropical. Tomato hybrids were developed by crossing wild and cultivated tomato varieties. The average fruit size of the tomato hybrids generated did not meet the level of acceptability in the local market. A modified three way cross between the advanced generation of the tomato hybrids and an exotic variety with giant fruit size was initiated. The resulting hybrids were evaluated to determine the magnitude of heterosis in floral traits and fruit size. Highly significant differences were observed among the genotypes in all the traits studied. Highly significant heteroses were found for flower length which ranged from 2.7 to 13.4% and 7.2 to 21.9%, style length 2.6 to 14.5% and 6.8 to 43%, fruit length 1.9 to 5.1% and 4.6 to 27.4% over the better and mid parents, respectively. Similarly, a significant positive heterosis was recorded for ovary area which ranged from 1.2 to 6.2%, ovary perimeter 1.6 to 6.2%, ovary length 4.8 to 15.3%, fruit diameter 5.7 to 6.5% and number of fruits per plant 14.56 to 55.195% over mid parents only. Key words : Heterosis, floral traits, modified three way cross, tomato, Solanum spp
Highlights
Tomato is one of the most important fruit vegetables in Nigeria
Positive heterosis was obtained for flower length in all the six the hybrids and the values ranged from 2.7 to 13.4% and 7.2 to 21.9% over the better and mid parents, respectively
A significant negative heterosis was found for flower width in all the hybrids and they ranged from -37.6% to -4.3% and -19.2% to -2.2% over the better and mid parents, respectively
Summary
Tomato is one of the most important fruit vegetables in Nigeria. It is mainly grown by small scale farmers under arable conditions. Many constraints affect the productivity and quality of tomato Some of such constraints are high humidity and rainfall and lack of locally adapted cultivars. The development of tomato that can withstand the high humidity conditions of south eastern Nigeria prompted the initiation of a hybridization programme. Crosses between two commercially acceptable but poorly adapted cultivars, Roma VF and Tropica and wild variety produced tomato hybrids with prolific fruiting (Uguru and Umukoro, 2005; Atugwu and Uguru, 2012) and increased disease resistance (Uguru and Igili, 2002) under high rainfall conditions. Fruit size improvement can be enhanced by considering the fruit development pattern such as floral traits and other fruit size components
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