EFFECT OF CROP ROTATION ON TOMATO BACTERIAL WILT (RALSTONIA SOLANACEARUM) AND SURVIVAL OF THE PATHOGEN IN THE RHIZOSPHERES AND ROOTS OF DIFFERENT CROPS IN ETHIOPIA

Survival of Ralstonia solanacearum in a environment or ecosystem depends on many factors, such as the race or strain of the pathogen, physical, chemical, biological soil factors and presence or absence of a host and non-hosts plants. The objectives of this study were to assess the effect of one and two season rotation sequences on the development of tomato bacterial wilt; and the survival ability of R. solanacearum in the rhizosphere and roots of presumable hosts and non-host crops in Ethiopia. A one season crop rotation involving tomato- maize-tomato, tomato- common beans -tomato and two season rotations consisting of tomato - maize- common bean-tomato, tomato –common beans – maize-tomato and tomato – tomato- tomato were established at Melkassa in Ethiopia. The effect of the system was evaluated on bacterial wilt of tomato under field conditions using a susceptible tomato cultivar (Marglobe). In one season rotation treatment involving common bean and maize after tomato resulted in a reduction of an average 6% and 16% final wilt incidence, respectively. Similarly, in the two seasons rotation sequence growing tomato after bean-maize and maize-bean resulted in about 29% average final wilt incidence reduction. The onset of wilt incidence was also delayed by one week in the two season rotations with common bean and maize compared to continues tomato growing and one season rotation with non-host crops. Survival of ability of R. solanacearum, strain designated as TomNa3 biovar 1 race 1 was studied under soil rhizosphere and roots of presumably non-host and hosts of different crops under glasshouse conditions. The pathogen was detected in rhizosphere soils and roots of presumable non-host and hosts for the pathogen after 120 days after inoculation. The population of bacterial pathogens was recorded in a declining trend but detectable in the rhizosphere soils and roots of presumable non-host crops at 30, 45, 60, 90 and 120 days after inoculation.