Surveying and fast detection of Ralstonia solanacearum bacterium in some Egyptian governorates

Naturally infected potato plants showing bacterial wilt symptoms were collected from different habitats and used for isolation of R. solanacearum pathogen. Also, isolation was carried out from soil, water canals, weeds and some other common crops (Pepper, Tomato, Banana, Snap Bean, Corn, Eggplant, Onion, Cabbage and Clover).  All isolates showed typical and atypical morphological growth of R. solanacearum on Selective Medium South Africa medium (SMSA).  Out of suspected 321 isolates of R. solanacearum, only 209 isolates were positive when identified using Immunofluorescence antibody staintest (IFAS) while the rest were negative. When these 209 isolates were identified again by growing on SMSA medium, only 194 isolates were positive as typical forms of R. solanacearum while the rest15 isolates appeared as atypical forms of R. solanacearum. Selected sixty-six isolates of those identified as typical or atypical forms of R. solanacearum were tested for their virulence. Results indicate that all tested 66 isolates could infect potato plants (cv. Spunta), where disease severity (DS %) ranged between 26.4% - 100 % when incubated for 20 days. In this respect, MktT-17 (Menofia - EL Kawady - typical - tuber isolate) isolate was the highest infective one. While, the least infective isolate was BhhaWa-53 (Beheira –Kom Hamada - atypical – water) isolate, at the same period of incubation. Also, the rest of other isolates were infective and caused bacterial wilt symptoms below 98.4% and over 28.0%. All atypical forms of R. solanacearum isolates were less infective than the typical forms which were more virulent in this respect. Also, all sixty-six tested isolates of typical or atypical R. solanacearum were infective and caused bacterial wilt symptoms of tomato plants (cv. Ponto) which reached 100%DS but they differed in the time of incubation. The typical isolates were more virulent and fast in their infection on tomato plants (cv. Ponto). The highest DS% on tomato plants (cv. Ponto) was recorded with the typical R. solanacearum isolate MktT-17 (Menofia - EL Kawady - typical - tuber) to be 100% at 4 days of incubation period. While, the lowest DS% was recorded with MmtOB-47 (Menofia - Om saber – typical – other common crop – Banana) isolate where it recorded 100% DS at 10 days of incubation period. Moreover, the fastest atypical form of R. solanacearum was GhzaS-55 (Gharbia - Kafr el Zayat - atypical - Soil) isolate which causing 100% wilt DS on tomato plants (cv. Ponto) at 9 days of incubation period while, the slowest atypical ones were BhhaS-56 (Beheira – Kom Hamada - atypical - soil), GdaS-62 (Giza - Wardan – atypical - soil) and GHzaOT-64 (Gharbia- Kafr el zayat atypical- other common crop - Tomato) isolate which caused 100% wilt DS on tomato plants (cv. Ponto) at 15 days of incubation period.