Physiological Responses of Almond Genotypes to Drought Stress

In this study, the physiological and developmental response of ten promising almond genotypes to deficit irrigation was investigated. A factorial experiment was conducted in a completely randomized block design with three replications during 2019 and 2020 at the Temperate Fruit Research Center, Horticultural Research Institute. The first factor was ten almond genotypes, and the second factor was three levels of drought stress (-0.33 MPa as a control, 0.9 and 1.6 MPa as moderate and severe stress, respectively). The results showed that growth and physiological characteristics, such as plant height, trunk diameter at the top of the plant, length of new branch growth, and leaf yellowness, as well as chlorophyll index based on the SPAD criterion, relative leaf water content, chlorophyll fluorescence, and activity of leaf enzymes including SOD, POD, CAT, and APX, varied among the ten almond genotypes under different levels of drought stress. Higher proline, RWC, and F-v/F-m values indicated a higher ability to tolerate drought stress in almonds. The study conducted a heatmap clustering analysis to classify 10 almond genotypes based on their response to drought stress. The results showed that the genotypes were divided into three groups, with two genotypes in the first group being more sensitive to drought stress. Also, the A-7-100 genotype in the third group was found to be more tolerant and adapted to drought stress than the other genotypes.