الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 80 |  |  |
| | | from | 80 | | |
Abstract
Bacterial wilt caused by Ralstonia solanacearum, is one of the chief severe diseases of potato in warm temperate regions, tropics and subtropics of the world. The study was conducted to isolate and identify bacterial pathogens and select the most resistant cultivars and using different management strategies of bacterial wilt disease have been studied in worldwide with special focus on alternative methods of disease control. In this study, Samples of potato tubers showing typical brown rot were collected from different potato fields in Beni-Suef, Menoufia, Beheira, and El- Sharkia, Governorates. The results of traditional identification through morphological and serological studies showed that the nine isolates were isolated and identified as five isolates which virulent (i.e. RS1, RS2, RS3, RS5 and RS8). Four isolates were avirulent (i.e. RS4, RS6, RS7 and RS9). Pathogenicity tests showed that the isolate (RS5) was the most severe isolate, as it was recorded the lowest percentage reduction of disease incidence and severity, but isolate (RS8) was the highest one. The results showed in the experiment of planting date that the plants sowing from the end of September to the beginning of October were the best planting dates for three potato cultivars, as it led to a decrease in the disease incidence and severity. Potato cultivars reacted differently and varied significantly in their degree of susceptibility. Bellini was the highest in susceptibility, followed by Spunta and Mondial Genetic distances and similarities between three potatoes cultivars based on SDS-PAGE profile. Data showed that the highest genetic distances value was found between Mondial and Bellini as the most distant genetically, while the lowest value found between Bellini and Spunta cultivars. In addition, In addition, when using four colors of plastic sheets such as (black, green, blue and clear) in soil solarization compared to uncovered soil exposed to sunlight and this soil was conducted in soil artificially infested with Ralstonia solanacearum. The results explained that the clear mulch recorded the most inhibition of three isolates of bacteria, to increase the average percentage reduction of disease incidence on three potatoes cultivars. On the other hand, soil un-solarized was the lowest inhibition on three virulence isolates of R. solanacearum. Furthermore, Screening of secondary metabolites of bio-agents against R. solanacearum, Bacillus subtilis was considered the best secondary metabolism in vitro and in vivo to reduce the bacterial wilt disease on three cultivars of potatoes Spunta, Bellini and Mondial, but the secondary metabolism of actinommycetes spp. was the lowest one. The results showed that when three types of fertilizers were used against bacterial wilt of potatoes in three different concentrations, humic acid was the most effective in vitro and in vivo to control potato wilt disease on three cultivars, but marine macro algal extract was the least fertilizer. The results were evident when chitosan nanoparticles were evaluated as an alternative disease management strategy and the best concentrations were (100µg/ml and 200µg/ml) in vitro and in vivo. Transmission electron microscopy (TEM) micro-graphs showed modification in the external shape of bacterial cell with treated. Also, the result of using Random amplified polymorphic DNA (RAPD)-PCR observed that differences in treated R. solanancearum genotype by nano-chitosan compared to the genotype of the same untreated isolate.