| چکیده انگلیسی مقاله |
Extended Abstract
Introduction and Objective: The reduction of genetic diversity in tomato (Solanum lycopersicum L.), caused by domestication and breeding, has required the use of all available genetic resources. Limiting cultivated tomato cultivars to modified cultivars and reducing genetic diversity is not desirable and causes vulnerability and instability of production. 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. They are often non-uniform and consist of different genotypes that are mostly pure 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. The aim of this research was to select accessions for purposeful crossings, to investigate the heritability of fruit traits, the amount of heterosis in the F1, and to select progeny with small fruit and nudeterminate growth.
Material and Methods: In this research, the number of 9 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, were identified and seed collection was done from them. Among these accessions, 17 crosses were made and the results of their first generation were analyzed. 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 the flowers opened. In each mass, 6 to 10 plants were selected for crossing. In one cluster, 2 to 4 flowers were considered for crossing. In case of no successful pollination and no fruit formation, crossing was repeated. After crossing and to control and prevent unwanted crossing by insects, a thin net (mosquito net) was used and the bushes were completely enclosed with it. 30-40 days after mating, the formed fruits were harvested. The fruits obtained in the laboratory were evaluated in terms of characteristics including fruit volume, fruit weight, fruit length, fruit diameter, number of seeds in the fruit, Brix, acidity and vitamin C. The design was based on a randomized complete block design with 17 treatments (17 crossings) in three replications. One-way analysis of variance of the measured traits was performed using SAS software version 9.1. Variance components, general heritability, phenotypic, genotypic and environmental diversity coefficients and the degree of trait heterosis were calculated.
Results: The results of variance analysis of different fruit traits showed that there is 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 one percent. The comparison of the average traits showed that fruit weight, fruit diameter and fruit length traits are the highest in the progeny of the Kermanshah*Rasht cross with the values of 28.16 grams, 3.29 mm and 2.71 mm, respectively. The highest fruit volume was recorded in the offspring of the Sari*Rasht cross with 18.8 ml. The highest number of seeds per fruit was counted with 141 and 140, respectively, in the cross between Gorgan*Varamin and Shoghgiri*Kurdistan. The highest Brix with 8.67% in the crossbreed of Rafsanjan*Kurdistan, the highest acidity with 11.03 milligrams per 100 ml of water in the crossbreed of Rafsanjan*Rasht and the highest vitamin C with 1.6mg per 100ml of water in the progeny of Kafshgiri*Rafsanjan was observed. In the traits of fruit size, fruit weight, number of fruit seeds, brix, acidity and vitamin C, the genetic variation coefficient was higher than the phenotypic variation coefficient, which indicated the lesser effect of environmental factors on these traits. In fruit length and fruit diameter, the phenotypic diversity coefficient was higher than the genetic diversity coefficient. The heritability of traits was also estimated. Fruit volume, fruit weight, acidity and vitamin C traits had general heritability (h2) from 80 to 99 percent. Brix value showed the lowest general heritability with 59%. Heterosis results showed positive heterosis in fruit diameter and volume. Also, 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 heritability (h2) and genetic progress were found for the traits of vitamin C, fruit acidity, fruit weight and fruit volume, respectively, which were found in the crossings of Kafshgiri*Rafsanjan, Rafsanjan*Rasht and Kermanshah* Rasht was obtained. On the other hand, in the term 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, which indicated 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 the breeder to choose the best combination and reach an optimal level of performance potential. |