Morpho-physiological Response of Avocado (Persea americana Mill.) Seedlings to Different Salinity Levels in Sidam National Regional State, Southern Ethiopia

Salt stress is the most important environmental stress that adversely affects avocado morpho-physiological performance. Therefore, this study has been conducted to evaluate the response of avocado seedlings to different salinity levels. The experiment was laid out in a Randomized Complete Design (RCD) with four salt concentration levels (0, 1.3 dS/m, 2.6 dS/m, and 3.9 dS/m) on grafted avocado seedlings, with three replications. The avocado seedlings were raised from Ettinger avocado scion grafted on Guatemalan race rootstock. The results indicate that most of the morphological growth parameters, such as rootstock diameter, sucker development, and root length, were significantly (p<0.01) affected by salt stress level. While tap root diameter and lateral root length were not significantly (p>0.05) affected by salt treatment. Except for the number of suckers developed on the rootstock, rootstock and scion diameter significantly decreased as salt concentrations increased from 0 to 3.9 dS/m. Similarly, significant (p<0.01) variations were also observed in leaf length, bud number, leaf fresh weight and dry weight, leaf area, shoot height, taproot length, and lateral root length. These parameters were also significantly decreased with the increase in salt concentrations. Likewise, photosynthesis, transpiration, stomatal conductance, and instantaneous water use efficiency were significantly affected by salt concentration, where relatively maximum scores were obtained at 0 and 1.3 dS/m. In general, salt concentration at 0 and 1.3 dS/m EC favors most of the growth and physiological performance of avocado seedlings compared to 2.6 and 3.9 dS/m. Thus, the study revealed that for vigorous growth of avocado seedlings at an early stage, the quality of irrigation water needs considerable attention to ensure robust avocado seedling growth.