بررسی بقای اپی فیتی پاتوتیپ های A و A* عامل شانکر مرکبات روی برخی از علف های هرز باغ های مرکبات

Citrus canker disease is one of the most important diseases of citrus trees in Iran and caused by Xanthomonas citri subsp. citri. This Pathogen can survive in the form of epiphyte, with low population density on citrus, non-citrus host and weeds. Among different aspects of the epidemiology of the disease, the study of the survival rate of the pathogen on infected weeds can play an important role in the control and eradication of It. The aim of this study was to determine the population dynamics of two pathotypes A and A* of citrus canker on the following weeds in greenhouse conditions: Amaranthus retroflexus, Medicago sativa, Avena ludoviciana, Plantago lanceolate, Portulaca oleraceae, Chenopodium album, Sorghum halepens and Xanthium strunarium. After culture of one strain of pathotype A and one strain of pathotype A* (isolated from lime in Kohgiluyeh and Boyerahmad province) on NA medium, a suspension of 107 cells / ml was prepared and sprayed on weeds of the same age in greenhouse conditions. Sampling was carried out at intervals of 1, 4, 9, 11, 13, and 20 days after inoculation. Extracts were obtained from tissues and then dilution series were prepared and appropriate dilutions were cultured. The colonies were counted after 48 to 72 hours. The results showed that the rate of increase and fluctuation of two strains in various weeds was different. After 20 days, weeds sprayed with pathotype A strain, were divided into four groups. Plantago lanceolate and Medicago Sativa with 5.8 and 5.2 (log of the number of bacterial cells per gram of plant tissue) were in the first group. Xanthium strunarium, Sorghum halepens and Amaranthus retroflexus respectively with 3.8, 3.8 and 3.7 were in the second group, Avena ludoviciana and Chenopodium album respectively with 4.8 and 4.6 were in the third group and the Portulaca oleraceae with 1.8 and the lowest population density, was in the fourth group. Also, the log of the bacterial cell count in grams of plant tissue of A* pathotype strain, divided the weeds into four groups: Medicago sativa and Plantago lanceolate with 6 and 5.9 in the first group, Avena ludoviciana and Chenopodium album respectively with 5 and 4.9 In the second group, Xanthium strunarium, Sorghum halepens and Amaranthus retroflexus respectively with 4, 4 and 3.8 in the third group and the Portulaca oleraceae with 1.2 was placed in the last group. Thusly, it seems that removal of these weed species as prominent source of inoculum is important for decreasing the population of pathogen and control of citrus bacterial canker disease.