Title : Endophytic bacteria Bacillus subtilis and salicylic acid: Biotic strategy to control postharvest diseases of Solanum tuberosum L
Potato (Solanum tuberosum L.) is a valuable food crop with great importance in ensuring food security worldwide. One of the most acute problems of modern agriculture and food industry is the loss of potato tubers (about 40-60% of the total harvest) during storage from diseases. Recently, beneficial bacteria Bacillus subtilis (with the well-known role in plant growth promotion and anti-stress physiological programs induction) generally recognized as safe microorganism to use in the food industry are considered for application as bio-active and eco-friendly agent for controlling postharvest decays. Of special interests are endophytic B. subtilis, living inside plant tissues, which allows them to be less dependent on external environmental factors (compared to rhizosphere and phyllosphere strains) while exhibiting “useful” features. Due to it is difficult to select an individual effective microbial strain with a broad spectrum of activity against range of pathogens an interest is co-application of B. subtilis with other methods (biological, physical) in an integrated vision of disease management. In this work we investigated the effect of endophytic B. subtilis (strains 10-4, 26D) in range of concentrations (103-108 CFU/mL) and its compositions with signalling molecule salicylic acid (SA) on potato tubers’ resistance to Phytophthora infestans and Fusarium oxysporum during storage. The experiments were carried out on virus-free potato mini-tubers (cv. Bashkirsky) grown using hydroponic system. Before storage tubers were dipped into suspensions of Ph. infestans (108 spores/mL) (causative agent of late blight), F. oxysporum (106 spores/mL) (causative agent of fusarium wilt and dry rot), water (control) and then dipped into suspension of B. subtilis (strains 10-4, 26D) in concentrations 103, 104, 105, 106, 107, 108 CFU/mL both alone and in composition with SA (0.05 mM), and stored at 18±1°C for 2 weeks and then at 3±1°C. Analysis the effect of B. subtilis (10-4, 26D) and SA on the development of late blight and fusarium of potato during 3 month storage showed dose-dependent manner in the action of B. subtilis (10-4, 26D) both individually and in mix with SA. It was revealed that B. subtilis (10-4, 26D) suppress the development of Ph. infestans and F. oxysporum starting from 106 CFU/mL and more, however, the most optimal against both diseases was 108 CFU/mL. When B. subtilis (10-4, 26D) used in mix with SA it was sufficient the concentrations of bacterial cells starting from 105 CFU/mL. Nevertheless, the best in suppressing both Ph. infestans and F. oxysporum were 107 CFU/mL (for 10-4+SA) and 106 CFU/mL (for 26D+SA). Besides, in variants with joined B. subtilis (especially strain 10-4) and SA application the tubers were fresher. Also, B. subtilis (10-4, 26D) both alone and in mix with SA decreased the pathogens-induced proline accumulation and lipid peroxidation in tubers indicating on protecting the cells against reactive oxygen species and controlling aging processes. Nevertheless, the mechanisms of B. subtilis (10-4, 26D) actions both alone and in mix with SA on potato under postharvest pathogen’s infection are require further detailed investigations to fully use their potential in agricultural and food industry. This research is supported by the Russian Science Foundation (Grant ? 18-76-00031).
Take Away Notes:
• Endophytic Bacillus subtilis, salicylic acid (SA), postharvest diseases, Phytophtora infestans, Fusarium oxysporum, Solanum tuberosum L.
• The findings presented in the work expand the knowledge about the regulatory action of B. subtilis and its compositions with signaling molecule SA on resistance of potato tubers against postharvest diseases caused by Phytophthora
infestans and Fusarium oxysporum during storage. The results of work could be used for development of new microbial
biological products for protection of potato tubers against postharvest diseases during storage and prolong their
«marketing» life with maintaining quality and nutritional value.
• Researchers from other faculty could use the presented data to expand their research or teaching. The obtained results could provide a practical solution to a problem that could simplify or make a job more efficient