Ecology, epidemiology and pathogenic variability of pseudomonas syringae pv. phaseolicola in the southern highlands of Tanzania.
| dc.contributor.author | Gondwe, Betty James | |
| dc.date.accessioned | 2023-03-14T11:02:23Z | |
| dc.date.available | 2023-03-14T11:02:23Z | |
| dc.date.issued | 1998 | |
| dc.description | PhD-Thesis | en_US |
| dc.description.abstract | Investigations were carried out to determine races of Pseudomonas syringae pv. phaseolicola existing in the Southern Highlands of Tanzania and the relationship between motility and virulence of the pathogen. The epiphytic survival of a brown diffusible pigment producing strain (9337- uncertain race type) and a non brown diffusible pigment producing strain (9359-racc 6) of P.s.phaseolicola was also studied in bean genotypes Kablanketi and Uyole-90. On the basis of cultural, biochemical and pathogenicity tests, 260 isolates were identified as P.s.phaseolicola. Using the Biolog Microplate identification system, other isolates of fluorescent pseudomonads encountered were confirmed to be Pseudomonas fluorescens A and Pseudomonas syringae pv. syringae A. Race determination, using eight halo blight differential bean cultivars, showed that races 1,2, 3, 4. 5, 6. 7b and 8 exist in the Southern Highlands of Tanzania. In addition, 7.6% of the strains characterized were of uncertain race type, suggesting occurrence of wider pathogenic variability than could be categorized using the current set of halo blight differential cultivars. Races 3 and 6 were the most prevalent. Race 3 occurred at a high frequency in Mbeya and was predominant in Nkasi and Sumbawanga districts. About 32% of the isolates collected produced the brown diffusible pigment in vitro. Some brown pigment producing strains were found to be race 3. Race 3 strains, which cause a very strong hypersensitive reaction associated with systemic necrosis on several bean genotypes including Tendergreen and A53, exist in the region. Strains isolated from N.wighlii and Desmodium sp. and characterized as race 7b were less virulent on bean cultivars A52 and A53 than race 7b strains originating from P. vulgar is.I hirly-six germplasm accessions were tested for resistance to eight strains of P.s.pliasi'olicola. New sources of resistance to races 1. 3, 4, 5, 7b, and strains 9337 (brown diffusible pigment producing strain) and 14494 (closely related to race 9) were identified. Differences in motility between and within races of P.s.phaseolicola were also demonstrated. Results from epiphytic population studies showed that there were differences between bean genotypes Kablanketi and Uyole-90 in supporting the epiphytic populations of die brown diffusible pigment producing strain 9337 and race 6 (strain 9359) of I’.s.p/iiixeolieolii. The resulting halo blight disease severity scores were generally low but comparably higher on Kablanketi inoculated with race 6. In vitro and in vivo studies under greenhouse conditions were conducted to determine the inhibitors effect of garlic bulb extract on growth of races 3, 6 and a brown diffusible pigment producing strain 9337 (uncertain race type) of P.s.phaseolicola. Antibacterial activity was shown as clear zones of inhibition. Halo blight disease incidence and severity on bean genotypes Uyole-90. Canadian Wonder and Kablanketi were significantly reduced. Pseudomonas syringae pv. phaseolicola strains 9337 (a diffusible brown pigment producer of an uncertain race type) and 9359 (race 6) survived in immature flat green pod tissues at 18 to 25°C in the laboratory for nine months. | en_US |
| dc.description.sponsorship | The Swedish Agency for Research Co-operation (SAREC), administered through the Directorate of Research and Postgraduate Studies of the Sokoine University of Agriculture | en_US |
| dc.identifier.uri | http://www.suaire.sua.ac.tz/handle/123456789/5005 | |
| dc.language.iso | en | en_US |
| dc.publisher | Sokoine University of Agriculture | en_US |
| dc.subject | Pseudomonas syringae | en_US |
| dc.subject | Ecology | en_US |
| dc.subject | Pathogen | en_US |
| dc.subject | Symptomatology | en_US |
| dc.subject | Southern highlands-Tanzania | en_US |
| dc.title | Ecology, epidemiology and pathogenic variability of pseudomonas syringae pv. phaseolicola in the southern highlands of Tanzania. | en_US |
| dc.type | Thesis | en_US |