Cultivated bacteria associated with tomato seeds

Relevance. Bacterial diseases that reduce tomato yield in both open and protected ground occupy a special place due to their harmfulness, intensity of transmission in agrocenosis, and difficulty of treatment. The widespread distribution of bacterial phytopathogens on tomatoes worldwide is due to their ability to remain viable for a long time on the surface and inside seeds. The aim of this study is to clarify the composition of cultivated bacteria associated with seeds of different tomato varieties and to identify pathogenic species. Material and Methodology. The work was conducted in the Bacteriology Department of the All- Russian Plant Quarantine Center (Moscow Region, town of Bykovo). To study the composition of cultivated bacteria, seeds from 24 varieties and hybrids of tomatoes were used. Seed samples were inoculated onto YDC nutrient medium in duplicate using the Drigalski method. Petri dishes were incubated at 27°C. DNA extraction from pure bacterial cultures was performed using the boiling method. Isolates were identified using Sanger sequencing. For pathogenicity testing, a bacterial suspension of isolates Pseudomonas sp. and Curtobacterium sp. was prepared from a two-day pure culture in sterile distilled water at a concentration of 106 CFU/ml. Tomato seedlings were grown from seeds of three hybrids. Artificial infection of the plants was conducted after the appearance of 2-3 true leaves by injecting into the stem between the cotyledons and the first true leaf in triplicate. Results and Discussion. During the phytosanitary examination of the obtained tomato seed material, bacterial isolates belonging to 10 genera were identified: Sphingomonas, Micrococcus, Phyllobacterium, Ralstonia, Frigoribacterium, Arthrobacter, Devosia, Agrococcus, Pseudomonas, and Curtobacterium. Using artificial infection of tomato seedlings, it was demonstrated that representatives of the genus Pseudomonas and Curtobacterium were pathogenic to tomato plants. It was found that plants of the Bellioso F1 hybrid are most susceptible to infection with Pseudomonas bacteria, with more numerous and large necrosis on the leaves compared with the Callanzo F1 hybrid and especially with the Senserno F1 hybrid. The bacteria of the genus Curtobacterium were less aggressive, and the necroses they caused on the leaves were smaller than those caused by Pseudomonas bacteria. Significant growth inhibition of the tested varieties was noted. Upon inoculation with Pseudomonas sp., the plants lagged behind the control by 40-50%, while infection with Curtobacterium sp. resulted in a growth delay of 44-54%, depending on the hybrid. Thus, qualitative and timely diagnosis of phytopathogenic agents of bacterial diseases, along with the culling or disinfection of seeds, is an effective way to reduce yield losses and increase the profitability of tomato production.