Genetic Analysis to Select Good Combiners for TYLCV-Tolerance and Yield Components in Tomato

As an attempt to develop high-yielding and TYLCV-tolerant hybrids, this study was conducted using TYLCV-tolerant inbred lines F8: 802-5 (P₁); F8: 802-21 (P₂) and selection of CLN3498E (P₃) and TYLCV-susceptible cvs Ace 55VF (P₄), Super Strain B (P₅) and Castlerock (P₆). A line × tester mating system was carried out under greenhouse conditions through the 2012 winter planting to produce tolerant × susceptible hybrids. Nine F₁ hybrids and their parents were evaluated for TYLCV tolerance, yield and fruit quality under natural infection of TYLCV by whitefly-mediated virus inoculations under field conditions during the 2013 and 2014 fall plantings. Mid-parent hterosis (H), heterobeltiosis (BPH), potence ratio (P), and combining ability effects were estimated for the evaluated traits. The variances due to combining abilities showed that additive gene action played the predominant role in controlling TYLCV-tolerance and yield traits. The hybrids of parent P₁, in addition to P₂ × P₄ exhibited the maximum H and BPH for early (EY) and total yield (TY)/plant under TYLCV-infection. The hybrids of P₁ were exhibited the maximum negative significant H of TYLCV mean score. TYLCV-tolerant parent P₁ was a good combiner for TYLCV mean score, EY/plant and TY/plant traits, while, TYLCV-susceptible parent P₄ was a good combiner for each of TYLCV-mean score, EY/plant, TY/plant, average fruit weight (AFW), and fruit TSS content traits. The TYLCV-tolerant cross P₂ × P₄ was a good combination for TYLCV mean score, TY/plant, AFW, fruit firmness, and fruit TSS content traits, while TYLCV-tolerant cross P₁ × P₄ was a good combination for TYLCV mean score, EY/plant, TY/plant and fruit titarable acidity content traits.