Effect Of Overwintering On Potato Wilt Bacteria Under Sana'a Conditions

الملخص

Survival of potato bacterial wilt disease was investigated in 107 infected potato samples under winter conditions in Sana’a,Yemen. Results obtained on the effect of over wintering low teperature on Ralstonia solanacearum showed that the highest rate of the bacterium population survival was associated more with the monoculture of potato cv. Picasso than other cultivars with or without irrigation. The number of colony forming units (CFU) dropped rapidly to low levels at low temperature but not to undetectable levels, but with temperature increase, recovery of colonies occurred. Bacterial survival occurred on various crops or in the soil of unplanted pots, with or without irrigation. Wheat plants were the most effective in reducing bacterial population, as measured by the CFU count. Such data support the assumption of using crop rotation with wheat or bean plants is more effective in reducing the bacterial pathogen population as compared to no rotation or fallow soil. There was variability among the different bacterial isolates. Isolate 5 had the highest CFU, followed by that for isolates 6 and 4 with a mean of 37.61 x104, 34.17x104 and 33.00x104 (CFU), respectively. In five samples collected during winter, data showed that samples differed significantly in their associated bacterial populations, except for samples collected on January 28,2010 and on March 18,2010.