Tomato line IIHR-249-1 can be used for improving antioxidant capacity, total carotenoids and lycopene in tomato breeding programmes. Cherry tomato lines IIHR-2866, 2865 and 2864 can be used for improving β-carotene content. LA-1777 and interspecific hybrids could be used for developing tomato lines rich in antioxidants as well as TSS.

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Employing known susceptible and resistant genotypes and pure bacterial inoculum (0.1 OD; 108 CFU/ml−1), five different inoculation methods were tried to assess the response of tomato genotypes to Ralstonia solanacearum. This included seed‐soaking inoculation, seed‐sowing followed by inoculum drenching, or at 2‐week stage through petiole‐excision inoculation, soaking of planting medium with inoculum either directly or after imparting seedling root‐injury. Seed‐based inoculations or mere inoculum drenching at 2 weeks did not induce much disease in seedlings. Petiole inoculation induced 90–100% mortality in susceptible checks but also 50–60% mortality in normally resistant genotypes within 7–10 days. Root‐injury inoculation at 2‐week seedling stage appeared the best for early and clearer distinction between resistant and susceptible lines. The observations suggest a role played by the root system in governing genotypic resistance to the pathogen. Direct shoot inoculation is to be adopted only for selecting highly resistant lines or to thin down segregating populations during resistance breeding.

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Wild relatives of the cultivated tomato (Solanum lycopersicum L.) are major sources of new genetic diversity for tomato improvement. Introgression lines (IL) are near-isogenic lines homozygous for one or several mapped wild DNA fragments in a common recurrent parent. A set of ILs developed by Cornell University from Solanum habrochaites accession LA1777 and recurrent parent E6203 has been made publicly available through the Tomato Genetics Resource Center of the University of California-Davis. Our objective was to identify LA1777 introgressions with potential to increase the marketable fruit yield of tomato grown in the tropics. A subset of ILs were each crossed to CLN2498E (resistant to bacterial wilt and some begomoviruses) to create IL hybrids (ILH). ILH, IL recurrent parent E6203, CLN2498E, and CLN2498E · E6203 (Hchk) were evaluated in replicated trials in Thailand, India, and Taiwan during two dry seasons. Highly significant effects for marketable fruit yield were detected in Thailand and Taiwan. ILH heterozygous for S. habrochaites segments at the bottom of chromosome 1 yielded about 20% than the Hchk at Thailand and Taiwan. Our results agree with previous results from Cornell University researchers who found a segment of S. habrochaites DNA located between TG158 and TG27 associated with increased total fruit yield in previous trials conducted in upper state New York. Yield improvement due to this S. habrochaites introgression can occur over a wide range of environments.

Tomato being sensitive to high temperature experiences mild to high temperature stresses under climate change conditions. To understand the response of tomato genotypes to mild temperature stress, a study was conducted in temperature gradient tunnel facility. The results revealed that across the genotypes studied, specific activity of antioxidant enzymes viz., superoxide dismutase (SOD), peroxidase (POX) and glutathione reductase (GR) increased significantly. Among the genotypes, increase in SOD activity was highest in cv. Arka Vikas, followed by IIHR 2195 and least in Abhinava. The GR activity was highest in Abhinava, followed by IIHR 2195 and least in cv. Arka Vikas. The mild temperature stress caused reduction in catalase (CAT) activity. The decrease in CAT activity and concomitant increase in POX activity was observed in cv. Arka Vikas. Low leaf water potential (W leaf ) and higher electrolyte leakage indicated that the membrane integrity was affected across the tomato genotypes even under mild temperature stress. Among the genotypes studied, cv. Arka Vikas showed greater activity of SOD and POX, higher membrane stability and least reduction in water potential under mild temperature stress.

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