Affiliation:
1. College of Horticulture and Gardening, Yangtze University, Jingzhou 434025, China
2. Institute of Tibet Plateau Walnut Industry, Yangtze University, Gyaca 856400, China
3. Hubei Academy of Forestry Science, Wuhan 430075, China
4. Botany and Microbiology Department, College of Science, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
5. Plant Production Department, College of Food and Agricultural Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
Abstract
This study aims to evaluate whether a selected arbuscular mycorrhizal fungus, Diversispora spurca, improves growth in drought-stressed walnut (Juglans regia L. cv. Qingxiang) plants and whether this improvement is associated with changes in osmolyte (fructose, glucose, sucrose, soluble protein, proline, and betaine) levels. After 60 days of soil drought treatment (50% of maximum field water-holding capacity), root D. spurca colonization rate and soil mycelium length decreased by 13.57% and 64.03%, respectively. Soil drought also inhibited the growth performance of aboveground (stem diameter, leaf number, leaf biomass, and stem biomass) and underground (root projected area, surface area, and average diameter) parts, with uninoculated plants showing a stronger inhibition than D. spurca-inoculated plants. D. spurca significantly increased these growth variables, along with aboveground part variables and root areas being more prominent under drought stress versus non-stress conditions. Although drought treatment suppressed the chlorophyll index and nitrogen balance index in leaves, mycorrhizal inoculation significantly increased these indices. Walnut plants were able to actively increase leaf fructose, glucose, sucrose, betaine, and proline levels under such drought stress. Inoculation of D. spurca also significantly increased leaf fructose, glucose, sucrose, betaine, proline, and soluble protein levels under drought stress and non-stress, with the increasing trend in betaine and soluble protein being higher under drought stress versus non-stress. Drought stress dramatically raised leaf hydrogen peroxide (H2O2) levels in both inoculated and uninoculated plants, while mycorrhizal plants presented significantly lower H2O2 levels, with the decreasing trend higher under drought stress versus non-stress. In conclusion, D. spurca symbiosis can increase the growth of drought-stressed walnut plants, associated with increased osmolyte levels and decreased H2O2 levels.
Funder
Hubei Province ‘14th Five-Year’ Major Science and Technology Aid Tibet Project
Key Research and Development Project of Hubei Province
King Saud University, Riyadh, Saudi Arabia