STUDIES ON BIOLOGICAL CONTROL OF POTATO BROWN ROT DISEASE

Abstract

I. Potato (Solanum tuberosum L) is grown in Egypt from September to February in three distinct growing seasons. Brown rot caused by Ralstonia solanaceamm was studied in samples collected from traditional potato districts in Egypt. More than five thousands samples collected over four-years period, (1996-1999), were examined. Sixty-four samples showed symptoms, and eighty-five showed latent infections. Potato cultivars, Nicola and Spunta showed the highest frequency of the brown rot infection. 2. Isolation of the pathogen was made on KB, CPGA, and SMSA media. Pathogenicity of isolates was tested in 3-week-old tomato seedlings, under greenhouse condition. Stem inoculation was made With a water suspension'\] x''l'08 ' cfu'nlli)."'he most Vir!Jleht (pathogenic on tomato plants) isolates were tested for pathogenicity on the target host (potato) of this study using the above-mentioned concentration under the green house condition. 3. Identification of the pathogen was made based on traditional and recently developed techniques employed routinely worldwide. Morphological, physiological and biochemical characteristics were studied. Serological (IFAS), Fatty acids profiling (FA), protein electrophoresis (PE) and nucleic acid-PCR based techniques were used. The employed techniques revealed that race 3 biovar II was the only detected pathovar affecting potatoes in Egypt. The Egyptian isolates exhibited very close similarity with the European isolates of R. solanacearum tested in this study. 4. Isolation of R. so!anaceamm from potato fields either planted with potatoes and/or with previous potato history was tried.