Somayeh Sadr, Vahid Mozafari, Hossein Alaei, Hossein Shirani, Ahmad Tajabadi Pour,
Volume 9, Issue 1 (12-2020)
Abstract
Pistachio endocarp lesion (PEL) is one of the most important disorders that has spread in the pistachio-growing regions of Rafsanjan and Anar in recent years and has caused great economic losses to farmers. In order to identify PEL symptoms, and investigate the biologic factors involved in the development of this disorder, on May 2016, 90 orchards with different levels of PEL, were randomly selected. The rate of development in each tree was scored in- to four levels. The incidence of this disorder was estimated to be 25.8% in Rafsanjan. The seeds with PEL symptoms were differentiated into six types based on the appearance of the symptoms. Then tissue from infected parts of each type were cultured in the PDA. From among the 18 prepared culture media, fungal growth was obtained only in five cultured plates. Isolated fungi were Ulocladium sp. Penicillium sp., Verticillium sp. and Fusarium sp. To prove their pathogenicity, the spore spray technique was used on detached cluster in vitro. None of the purified fungi caused symptoms similar to the symptoms of PEL. Isolated strains from the pistachio seeds with PEL symptom often were saprophytic and soil borne; they were abundant in the orchard and could be transferred to the shoots of trees under the influence of various factors, such as: tillage, soil splashing by rain drops, and wind. In this study, the role of these fungal agents on the development of PEL was rejected.
Volume 10, Issue 1 (3-2019)
Abstract
Silver nanoparticles have antimicrobial activity and are used in various commercially produced products. In this study, the effects of two types of nanosilver formulations, including LS2000 and L2000 on two strains of Streptomyces and three phytopathogenic agents, Pythium aphanidermatum, Pythium ultimum and Fusarium solani were investigated. Streptomyces and phytopathogenic agents were cultured on ISP2 and PDA medium respectively supplemented with 0, 5, 10, 25, 50 and 70ppm of LS2000 and L2000. The influence of LS2000 and L2000 on mycelium of Streptomyces was investigated by atomic force microscopy (AFM). Colony forming unit (cfu) of the bacteria decreased in response to elevated concentrations of L2000. LS2000 completely inhibited growth of both strains at a concentration of 5ppm. The inhibitory effects of LS2000 on the phytopathogenic agents were more than L2000. P. aphanidermatum showed the highest tolerance to L2000 and only at 75ppm of the nanoparticles, the diameter of the colonies was decreased. High susceptibility of F. solani to L2000 caused a decrease in fungal colony diameter in lowest concentration of the nanoparticles. The growth of all phytopathogenic agents was decreased by LS2000 and completely stopped in a concentration of 50ppm. The results showed that LS2000 destroyed mycelial networks of the both bacteria in all tested concentrations. Vesicles appeared on the surface of the mycelium branches, subsequent to treatment with L2000. Based on the results, the inhibitory effects of silver nanoparticles on the beneficial soil bacteria were more than on the phytopathogenic agents. Therefore, more caution should be taken in using silver nanoparticles as a fungicide in agriculture.
