Evaluation of starting material when breeding heat resistant tomato varieties for the South of Russia
An important stage in the breeding process when developing F<sub>1</sub> hybrids is the search for sources and donors of valuable economic traits. In recent years, dry and hot weather prevails in the south of Russia during the growing season of tomato. High ambient temperatures inhibit the growth and development of tomato, thereby reducing its yield and quality. The heat resistance of plants is influenced by the environment, agricultural technology and especially the genotype. Therefore, the purpose of our research was to study the heat resistance of canned tomato varieties in laboratory conditions to search for plant genotypes with high heat resistance, for further use in breeding highly productive varieties and hybrids. The studies were carried out in 2018- 2020. The article presents the results of the assessment of six mid-season tomato samples suitable for processing into tomato products and whole-fruit canning. According to the results of laboratory studies, varieties with increased heat resistance of plants have been identified (LK-2840, LG-1181), weak organic heat resistance was shown by varieties Mirage and Roker. In 2019, due to the prevailing conditions, an epiphytoty of viral diseases and stolbur was observed, which did not allow assessing the yield of tomato. In 2018 and 2020 the variability of productivity to a greater extent (78,9 %) was influenced by the varietal characteristics of the studied samples. Weather conditions also had a significant impact on yield, although to a lesser extent (20.6%). Crossing was carried out and hybrid combinations were obtained with the participation of heat-resistant samples for further study of the inheritance of this trait.