Title: Estimation of Epiphytic Population Size of Pseudomonas syringae pv. syringae on the Weeds of Apricot Orchards Infected to Bacterial Canker

The epiphytic phase of Pseudomonas syringae pv. syringae (Pss) has basic role in the outbreak and distribution. This research was carried out to estimate epiphytic population rate of Pss on some weeds of apricot orchards infected to bacterial canker. In October-November 2008, from the weeds including Malva neglecta, Taraxacum officinale, Convolvulus arvensis, Chenopodium album, Sorghum halepense, Amaranthus retroflexus and Agropyron repense were sampled. Then, various dilutions up-to 107 of suspension prepared from plant tissue were distributed on the semi-selective medium NAS and incubated at 25±1°C. After 48-72 hours, bacterial colonies were numerated and rate of bacterium per 1 gram of fresh tissue of the plants was calculated by using of the dilution multiples. Logarithm of the numbers was used for statistical analysis and mean comparison. The weeds were significantly different at probability level 1% for epiphytic population rate of Pss. Sorghum halepense, Agropyron repense and Amaranthus retroflexus had the highest epiphytic population rate with 6.785, 6.145 and 5.22 (Log bacterial cell per 1 gram plant fresh tissue) respectively and 2 weeds, Malva neglecta and Convolvulus arvensis had the lowest epiphytic population rate with 2.605 and 2.35 (Log bacterial cell per 1 gram plant fresh tissue) respectively. It is seem to the role of the growth pattern, structural and physiological attributes of the weeds in their epiphytic population rate become potential.