А. В. Вишнякова Tomato crops are susceptible to a significant number of diseases that reduce both yield and product quality, requiring the improvement of genetic diversity and the creation of genetically resistant varieties. Solanum sisymbriifolium Lam. is a source of resistance to bacterial wilt, verticillium wilt, root nematodes, carmine spider mites and late blight. The hybridization of tomato and sticky nightshade is feasible, but involves difficulties in overcoming prezygotic and postzygotic barriers to non-crossing. This study investigates the effect of exogenous phytohormones, specifically zeatin and abscisic acid, on fruit set and the number of developing ovules in crosses between Solanum lycopersicum and Solanum sisymbriifolium. Six tomato lines with functional male sterility and a sample of sticky nightshade ( OOO Breeding Station named after Timofeyeva ) were used in the hybridization process. The stigmas of tomato lines, which had been emasculated at the lemon-yellow bud stage, were treated with zeatin and abscisic acid ( ABA ) solutions for ten minutes and for two hours before pollination. The studies showed that the phytohormone treatment induced a genotype-specific response. Application of zeatin for two hours doubled fruit set in two of the tomato genotypes. In addition, short-term treatment with zeatin had a positive effect on fruit set in all genotypes. The application of ABA had a multidirectional effect on fruit set. A significant decrease in fruit set was observed in the Roz.son2–6 genotype. In contrast, in the st8 genotype, two hours of ABA treatment resulted in no fruit set, whereas ten minutes of exposure facilitated successful fruit set from all pollinated flowers. The effect of phytohormones on the mean number of developing ovules was remarkable in large-fruited tomatoes. Zeatin treatment increased the number of developing ovules, while the response to ABA treatment depended on genotype and time of treatment. In cherry tomato, phytohormone application had a statistically significant effect on the number of developing ovules only in the st8 genotype. However, prolonged phytohormone treatment decreased the number of developing ovules. Conversely, a brief 10-minute zeatin treatment showed a threefold increase in the average number of developing ovules in the fruit.
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