پژوهشنامه اصلاح گیاهان زراعی (Jun 2024)
The Study of Parents and F1 off Spring from the Crossing of Some Iranian Tomato Accessions
Abstract
Extended Abstract Background: The reduction of genetic diversity in tomatoes (Solanum lycopersicum L.), caused by domestication and breeding, has necessitated the use of all available genetic resources. Limiting cultivated tomato cultivars to modified cultivars and reducing genetic diversity are not desirable and cause production vulnerability and instability. Native populations can be used as genetic resources to improve and introduce superior crop varieties. Local populations are one of the most important genetic resources that are often non-uniform and consist of different and mostly pure genotypes. Breeding tomatoes means transferring desirable traits from parents to progeny and causing the variety and quality of tomatoes. Considering the great variety of tomato cultivars found in Iran, they can be used to select high-quality cultivars and produce desirable hybrids. This research aimed to select accessions for purposeful crossings to investigate the heritability of fruit traits, and the amount of heterosis in the F1, and to select progeny with small fruit and non-determinate growth. Methods: In this research, seeds were collected from nine identified local accessions of native cherry tomatoes in Iran, including Kafshgiri from Gorgan, 2) Darklate, 3) Kurdistan, 4) Varamin, 5) Rasht, 6) Gorgan, 7) Rafsanjan, 8) Sari, and 9) Kermanshah. These accessions were subjected to 17 crosses, and the results of their first generations were analyzed afterward. After collecting pollen from the male parent and removing the stamens of the female parent flowers, the pollen was placed on the stigma of the female in the early morning before opening the flowers. In each mass, 6-10 plants were selected for crossing. In one cluster, 2-4 flowers were considered for crossing. Crossing was repeated in the case of no successful pollination and no fruit formation. After crossing and to control and prevent unwanted crossing by insects, the bushes were completely enclosed with a thin net (mosquito net). The formed fruits were harvested 30-40 days after mating. The fruits obtained in the laboratory were evaluated in terms of fruit volume, fruit weight, fruit length, fruit diameter, number of seeds in the fruit, Brix, acidity, and vitamin C. The experiment was based on a randomized complete block design with 17 treatments (17 crossings) in three replications. One-way analysis of variance (ANOVA) for the measured traits was performed using SAS software version 9.1. Other calculated parameters were variance components, general heritability, phenotypic, genotypic, environmental diversity coefficients, and the degree of trait heterosis. Results: The results of ANOVA for different fruit traits showed a significant difference between the studied crosses in terms of fruit volume, fruit length, fruit weight, fruit diameter, number of fruit seeds, Brix, acidity, and vitamin C at the probability level of 1%. The comparison of the average traits showed that fruit weight, fruit diameter, and fruit length traits were the highest in the progeny of the Kermanshah × Rasht cross with values of 28.16 g, 3.29 mm, and 2.71 mm, respectively. The highest fruit volume (18.8 ml) was recorded in the offspring of the Sari × Rasht cross. The highest number of seeds per fruit was counted at 141 and 140, respectively, in the cross between Gorgan × Varamin and Shoghgiri × Kurdistan. The highest Brix (8.67%) belonged to the crossbreed of Rafsanjan × Kurdistan, the highest acidity (11.03 mg/100 ml of water) to the crossbreed of Rafsanjan × Rasht, and the highest vitamin C (1.6 mg per 100 ml of water) to the progeny of Kafshgiri × Rafsanjan. In the fruit size, fruit weight, number of fruit seeds, Brix, acidity, and vitamin C traits, the genetic variation coefficient was higher than the phenotypic variation coefficient, indicating the lesser effect of environmental factors on these traits. In fruit length and diameter, the phenotypic diversity coefficient was higher than the genetic diversity coefficient. The estimated heritability (h2) of traits revealed that fruit volume, fruit weight, acidity, and vitamin C traits had general h2 from 80 to 99%. The Brix value showed the lowest general h2 of 59%. The results showed positive heterosis in fruit diameter and volume. Negative heterosis was observed in fruit length, fruit weight, and number of seeds. All crosses showed positive and high heterosis regarding fruit size, and the highest fruit size heterosis with 10.71 was obtained in the progeny of the Kurdistan × Kafshgiri cross. The superior cross in terms of fruit diameter was identified in the Kermanshah × Rasht cross, with a heterosis of 7.53. Conclusion: The obtained results showed that the highest level of general h2 and genetic progress were found for the vitamin C, fruit acidity, fruit weight, and fruit volume traits, respectively, which were found in the crossings of Kafshgiri × Rafsanjan, Rafsanjan × Rasht, and Kermanshah × Rasht. In terms of fruit size, fruit weight, number of fruit seeds, soluble solids, acidity, and vitamin C, the genetic variation coefficient was higher than the phenotypic variation coefficient, indicating less influence of environmental factors on these traits. In other words, high heritability, genetic progress, and genetic diversity for quantitative and qualitative traits can help breeders choose the best combination and reach an optimal level of performance potential.
