Heterosis and leaf curl virus resistance in rainy season tomato under North Indian conditions

Purpose of this study was to identify heterotic hybrids of tomato resistant to leaf curl virus disease. Eleven parental lines and their 55 one-way F1 crosses produced in a diallel mating design were evaluated for fruit yield, fruit quality, tomato leaf curl virus (TLCV) resistance and other important traits at Research Farm of the Department of Vegetable Science, Punjab Agricultural University, Ludhiana (India) during autumn of 2012. Parent 2-1 showed no TLCV symptoms throughout the growth period under natural epiphytotic conditions. The remaining lines showed mild to very severe disease infection. Seventeen of the crosses were completely free from TLCV symptoms under natural field conditions. Heterosis was worked out over mid-parent, better parent and commercial resistant check NS 524. The hybrids outperforming the best check (NS 524) included 102-13-6-1 × 2-1 for marketable (66.15%) and total fruit yield (63.12%), Punjab Chhuhara × 58-18-1-1 for dry matter content (43.89%), 58-11-1-1 × 102-13-6-1 for fruit weight (34.14%), 102-1-6-1 × 115-1-8-1 for number of locules (-45.15%), 56-14-7-1 × 58-18-1-1 for lycopene content (61.06%), 102-1-6-1 × 58-18-1-1 for TSS content (19.32%), 58-18-1-1 × 55-26-1-1 for pericarp thickness (49.56%), 102-1-6-1 × 115-1-8-1 for polar diameter (32.07%) and 115-1-8-1 × 55-26-1-1 for equatorial diameter (19.07%). Based on the overall performance, four crosses viz., 102-8-5-1 × 7-5-1, 102-13-6-1 × 55-26-1-1, 58-11-1-1 × 58-18-1-1 and 102-13-6-1 × 2-1 were identified as promising. These hybrids recorded fruit yield of 2.22, 2.29, 2.70 and 3.24 kg plant-1, respectively, which was either at par with or significantly better than the resistant check NS 524 (1.95 kg plant-1). The hybrids also had acceptable fruit shape index (0.97-1.20) and fruit size (36.66-96.66 g).   Key words: Tomato, heterosis, Diallel, tomato leaf curl virus (TLCV).