EFFECT OF WATER STRESS ON ROOT ROT DISEASE OF PISTACHIO SEEDLINGS CAUSED BY Fusarium solani *

Water stress is a major limiting factor in plant growth and can increase the incidence and severity of root rot diseases. The effects of water stress on root rot disease of pistachio seedlings caused by Fusarium solani were studied in a greenhouse experiment. Treatments consisted of three levels of soil moisture (D0= 80% Field capacity (FC), D1= 50% Field capacity (FC) and D2=25% Field capacity (FC)) and three levels of fungal pathogen (F0= control and F1and F2 for two isolates of F. solani). The experimental arrangement was factorial with completely randomized design with six replications. According to the results, the main effects of fungal isolates and water stress treatments caused a significant reduction (at 1%) in shoot height and root length, shoot and root dry weight, shoot and root fresh weight, leaf numbers, root volume and leaf surface area over the control. Water stress and Fusarium interaction caused a significant reduction (at 1%) in all plant growth parameters except for root dry weight Based on the results, water stress increased the negative effects of the pathogen. In this regard, the interaction between F2 isolate and 25% field capacity had a greater impact on reducing growth parameters. Root colonization of pistachio seedlings by Fusarium isolates and disease severity increased by increasing water stress. Therefore, water stress can increase the negative effects caused by F. solani in pistachio seedlings.