Effect of Mycorrhizal Symbiosis on the Development of the Canary Island Tomato Variety “Manzana Negra” under Abiotic Stress Conditions

Tomato production in the Canary Islands has significantly decreased in recent years due to the presence of parasites and pathogens, poor-quality irrigation water, lack of infrastructure modernization, and increased competition. To address this issue, local varieties with better agro-climatic adaptation and organoleptic characteristics have been cultivated. These varieties show their maximum potential under an agro-ecological cultivation system, where the beneficial micro-organisms of the rhizosphere (in general) and mycorrhizal fungi (in particular) have a positive influence on their development, especially when the plants are subjected to biotic or abiotic stresses. Irrigation water in Canary Islands tomato cultivation comes from groundwater sources with moderate levels of sodium and chlorides or sodium and bicarbonates. This study evaluated the response of mycorrizal plants of the local tomato variety “Manzana Negra” under abiotic stress conditions due to the presence of chlorides and bicarbonates. Two tests were carried out with mycorrhizal and non-mycorrhizal plants. In the first one, 0, 75, and 150 mM NaCl solutions were applied. In the second, the nutrient solution was enriched with sodium bicarbonate at doses of 0, 2.5, 5, 7.5, 10, and 12.5 mM. Presence of native mycorrhizae improved the growth and nutrition of plants affected by irrigation with saline and alkaline water containing chloride and sodium carbonate. Symbiosis produced statistically significant increases in all plant-development-related variables (stem length and diameter; fresh and dry weight) in all bicarbonate concentrations. However, the results with the application of sodium chloride do not seem to indicate a positive interaction in most of the analytical parameters at 150 mM NaCl concentration. The mycorrhizal inoculation with local fungi can be interesting in the production of seedlings of this tomato variety in situations of moderate salinity, especially under bicarbonate stress conditions.