GROWTH, PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF ARBUSCULAR MYCORRHIZA INOCULATED AVOCADO (Persea americana M.) RACESUNDER MOISTURE STRESS CONDITIONS

Abstract

Avocado is one of the most economically important and widely grown fruit crops in tropical and subtropical regions. It is mainly grown in the southern, South Western, and Eastern parts of Ethiopia, with high economic returns. Despite its importance, production is hampered by abiotic factors like moisture limitation in the nursery and later in the orchard. This requires alternative and effective strategies and tools to overcome the challenge, such as inoculating with arbuscular mycorrhiza fungi as a soil amendment. This study was designed to investigate the effect of AMF inoculation on the morpho physiological and biochemical responses of two avocado (Persea americana M.) races under different moisture levels. A factorial combination of two inoculation levels (inoculated and non-inoculated), two avocado races (Mexicana and Guatemalan), and four water withholding intervals (daily watering, 7-days, 14-days, and 21-days watering intervals) were arranged in a CRD design with three replications. Results of the study revealed that growth parameters of avocado seedlings such as internode length and seedling height were influenced by the main effects of arbuscular mycorrhizae and moisture while, leaf number, leaf area were influenced by main and two way interaction effect of arbuscular mycorrhizae and moisture while xylem number and xylem width affected by interaction effect of race and moisture. However, root length, root number, and average root diameter were influenced by the main, two-way, and three-way interaction effects of race, arbuscular mycorrhizae, and moisture levels. The highest mean values of leaf area, root number, root length, xylem number, xylem width, and biomass fresh and dry weight were observed from Mexicana treated with arbuscular mycorrhizae under daily and moisture stress treatments. Whereas the minimum value was recorded from Guatemalan race grown under non-inoculated and 21 days water withholding treatment. Moreover, photosynthesis rate, transpiration, water use efficiency, chlorophyll content, proline content, biomass fresh and dry weight were significantly influenced by the main, two ways and three-way interaction effect of avocado races, arbuscular mycorrhizae and moisture levels. All growth, physiological and biomass parameters were significantly decreased under drought stressed conditions. However, compared to non-inoculated seedlings, the inoculation of arbuscular mycorrhizae considerably increased all those growth, physiological, biochemical, and biomass parameters even under drought stress. Among the tested races, "Mexicana" showed significantly well performance under drought stress conditions than Guatemalan cultivar. In conclusion, the inoculation of arbuscular mycorrhizae considerably improved drought stress tolerance in both races compared to non-inoculated treatments. However, further research is needed under field condition before generalized conclusions can be drawn