تأثیر دما بر رشد رویشی و بیماریزایی عامل بلایت شمشاد، Calonectria pseudonaviculata تحت شرایط آزمایشگاه و گلخانه

Forest boxwood, with the scientific name Buxus hyrcana Pojark, is one of the most important evergreen plant species specific to the forests of the Caspian Sea. To investigate the effect of different temperatures on the vegetative growth of the boxwood blight agent, a piece with a diameter of 5 mm from each isolate was placed in the center of Petri dishes with a diameter of 9 cm containing PDA culture medium. The cultures were kept at temperatures ranging from 5 to 35 degrees Celsius, with a 5-degree interval. They were placed in the incubator in three replicates. Then, the radial growth rate of the isolates was measured once every 48 hours. Additionally, the effect of temperature on pathogenicity was investigated using the cut leaf test, following Guo et al.'s method. Five leaves were placed in 10*100 mm Petri dishes containing water-agar 1.5%, upright from the tail of the leaf. Subsequently, 5 microliters of inoculum with a 10X concentration were inoculated onto the surface of the leaves. The Petri dishes were covered with parafilm and placed in an incubator at temperatures ranging from 5 to 35 degrees Celsius, with a 5-degree interval. This experiment was replicated three times, including a negative control. The leaves were checked every 48 hours to monitor the progression of disease symptoms. To assess the severity of the disease in the greenhouse, the causative fungus was cultivated on PCA culture medium and incubated for two weeks. The spores produced were rinsed with sterile distilled water, and a spore suspension with a concentration of 4*104 was prepared. Inoculation was carried out by immersing the plant leaf in the spore suspension. To provide optimal humidity for spore germination and disease development (80-90%), pots were covered with nylon bags, and a piece of wet cotton was placed inside the nylon to maintain moisture. The pots were placed in the greenhouse at temperatures of 15-20, 20-25, and 25-30 degrees Celsius. The assessment of pathogenicity was conducted four times, with a five-day interval. Based on the results, the highest rate of vegetative growth of strains occurred at 25 degrees Celsius, and the lowest rate occurred at 5 degrees Celsius. Additionally, the rate of vegetative growth of strains at 30 and 35 degrees Celsius was zero. Moreover, the highest and lowest rates of disease under laboratory conditions were at temperatures of 20 and 5 degrees Celsius, respectively. Furthermore, the rate of disease at temperatures of 30 degrees Celsius and above was zero. In evaluating the effect of temperature on the pathogenicity of the fungus under greenhouse conditions, based on the assessment of disease severity, the results showed that temperatures of 20-25 and 15-20 had the highest and lowest disease rates, respectively.