Response of Almond Genotypes/Cultivars Grafted on GN15  Garnem Rootstock in Deficit-Irrigation Stress Conditions

This study was conducted to evaluate the response of Iranian promisinglate blooming almond genotypes to deficit-irrigation stress on GN15 rootstock. One-year old plants subjectedto three deficit-irrigation, including moderate and severe stress (soil water potential, Ψsoil = -0.8 and -1.6 MPa, respectively) and a control treatment (Ψsoil= -0.33 MPa), were applied for six weeks to five grafting combinations. A factorial experiment was conducted with a CRD which included three irrigations factors, five genotype factors and three replications. Genotypes/cultivarsincluded: ‘K3-3-1’, ‘H’, ‘13-40’, ‘Sahand’ and ‘Ferragness’ grafted on GN15 rootstock. Deficit-irrigation stress caused a significant reduction in plant growth parameters such as fresh and dry weights of plant organs, leafnumber, and total leafarea and leaf relativewatercontent in all almond genotypes and cultivars. Specific leaf weight (SLW) and leafabscission also significantly increased in drought-treated plants compared to the control group. Total shoot length, individual leaf area, leaf dimension (length and width), stomatal size and frequency were decreased in response to deficit-irrigation treatments. In response to stress, the‘Ferragnes’ and ‘Sahand’ cultivars on GN15 rootstock showed the highest relative water content (RWC) among the genotypes and showed the smallest decrease in fresh and dry weights of organs. The ’13-40’ and ‘K3-3-1’ genotypes showed the greatest leaf abscission and a decrease in the total leaf area, (the most reduction in transpiration area).