تاثیر کاربرد خاکی گوگرد بر کاهش پوسیدگی آرمیلاریایی نهال‏های پسته در شرایط گلخانه

Armillaria root and crown rot is one of the most important diseases of pistachio trees that can cause the death of pistachio trees. Control of the disease is very difficult due to the characteristics of the causal agent. In this research, the effect of concentrations of 2, 4 and 8 percent mineral sulfur on the severity of Armillaria rot in Badami Zarand pistachio seedlings was evaluated in greenhouse conditions. Three concentrations of sulfur were added to the soil of the pots at two times, before and after inoculation of seedlings with Armillaria mellea (Am). The inoculum consisted of 2-cm pieces of apple tree branches that were colonized by the pathogen in 6 months. In treatment of sulfur before pathogen inoculation, pistachio seeds were sown in soil containing concentrations of 2, 4 and 8% mineral sulfur and after three months, each seedling were inoculated with two pieces of colonized branches for. In the treatment of sulfur after pathogen inoculation, three-month-old pistachio seedlings were inoculated with the pathogen and then concentrations of 2, 4 and 8% mineral sulfur were added to the soil of the pots by irrigation water. The effect of mineral sulfur was evaluated by measuring the growth and biochemical characteristics and nutrient concentration of pistachio seedlings. The results showed that in treatment of sulfur before pathogen inoculation, significant increase of shoot dry weight and concentration of chlorophylls (a, b, a+b), K, Ca, Mg, Zn and Mn was observed in concentrations of 4 and 8% of sulfur compared to AM treatment but root dry weight and concentration of N, P and Fe increased significantly only in 8% concentration of sulfur. The percent colonization of the roots by A. mellea significantly reduced from 92% in pathogen treatment and reached to 82 and 75% in 4 and 8% concentration of sulfur respectively. The mortality of seedlings, significantly decreased from 96% in pathogen treatment to 65% in 8% concentration of sulfur before pathogen inoculation. Sulfur treatments after pathogen inoculation had no effect on above criteria in comparison with the control and pathogen inoculation treatments. In general, the results of this research showed that using of 8% concentrations of mineral sulfur before inoculation of A. mellea can improve the growth, biochemical and nutritional characteristics of pistachio seedlings and reduce the severity of Armillaria crown and root rot.