Identifying sources of resistance to fusarious and bacterial rot in onions (Allium cepa L.)

Relevance. In onion breeding, the priority is the development of interline hybrids based on cytoplasmic male sterility. To obtain these hybrids, it is necessary to develop a pool of inbred lines characterized by high combining ability across a range of economically valuable traits and resistance to biotic and abiotic factors. The most damaging diseases of onions are Fusarium wilt and bacterial wilt, which can cause yield losses of 40% or more. The aim of the research. To evaluate parental lines and hybrid combinations based on them for resistance to native strains of Fusarium and bacterial rot pathogens. Materials and Methods. The study was conducted from 2022 to 2024 at the FSBSI FSVC in the Odintsovo District of the Moscow Region. Twelve onion breeding lines and nine hybrid combinations were analyzed. The onions were grown from seedlings in breeding and hybrid nurseries according to generally accepted methods. The resistance of the studied samples to Fusarium and bacterial rot was assessed using phytopathological selection methods. Results. It was established that under the vegetation conditions of the Moscow region, the basis of the pathocomplex of mixed rot of onions consisted of Fusarium spp. and Pseudomonas spp., while under storage conditions – Fusarium spp., Penicill spp., Botrytis spp., Aspergillus spp., Pseudomonas spp. Immunological assessment of parental lines for resistance to fusarium and bacterial rot allowed us to isolate two maternal sterile lines «A» and five paternal fertile lines «C» with a low damage index under natural infectious background conditions (I=0,5-1,5). Inclusion of these lines in the selection process made it possible to obtain two hybrid combinations (10/22 and 20/22) with group resistance to native strains of fusarium (F. acuminatum and F. annulatum) with Vп=0-472 mm3; two (7/22 and 10/22) – with group resistance to bacterial rot pathogens with Vп=0- 514 mm3. The sources of resistance to highly aggressive strains of P. marginalis are hybrid combinations 3/22 and 4/22 (Vп=40-472 mm3), P. fluorescens – 7/22 and 22/22 (Vп=0-371 mm3). In the 11/22, 19/22, and 10/22 combinations, overdominance was observed relative to the best parent in terms of bulb survival during storage (heterosis effect of 8,3-30,5%). Promising resistant lines and hybrid combinations have been included in the breeding program for the development of domestic competitive heterotic onion hybrids.