2.2.115
b) CHARACTERISTICS OF STRAINS OF <1> RALSTONIA SOLANACEARUM
b) CHARACTERISTICS OF STRAINS OF <1> RALSTONIA SOLANACEARUM
V SUNAINA l, V KISHORE l,CS SHEKHAWAT l
l Central Potato Research Station,Modipuram 250110 UP, India
Background and objectives
Among the bacterial diseases limiting production of potatoes, the wilt disease caused by Ralstonia solanacearum is a serious problem in tropical, subtropical and warm temperate zones of Northern India. Thirty- nine strains, isolated from cultivated and wild host plants, were compared with respect to natural host range, reaction to five differential hosts, physiological and biochemical tests and colony appearance on tetrazolium chloride (TZC) medium (1]. This research was undertaken to determine variation and characterization of the strains of R.solanacearum collected from a wide range of host plants. Material and methods
Inoculum was prepared from cultures of the virulent, fluidal colony type grown on TZC medium at 30 C for 48 hr. Host plants used in pathogenicity were: potato (Solanum tuberosum ), tomato ( Lycopersicon esculentum ), eggplant( Solanum melongena ), pepper ( Capsicum annuum ) and datura ( Datura stramonium )
. Results and discussion
On TZC medium, all virulent strains produced fluidal colonies with light pink to light red centres after 48 hr incubation, but there were differences in size, fluidity, formazan pigmentation and melanin formation. Potato and tomato were susceptible to all the strains. Eggplant was susceptible to most of the strains, datura showed differences in reaction to specific strains and pepper was resistant to four strains isolated from ginger plants. Strains differed in their capacity to oxidize sugar alcohols and disaccharides. Nine strains, obtained solely from potato, oxidized disaccharides but not sugar alcohols, were placed in biovar II. Twenty five strains with broad host range, oxidized sugar alcohols and disaccharides, were placed in biovar III. Four strains obtained from ginger plants, oxidized sugar alcohols but not disaccharides, were placed in biovar IV. One strain obtained from potato could not be placed in any of the known biovars as this strain produced acid from maltose and mannitol but failed to oxidize sorbitol [2). The collection of thirty nine strains did not have any representative of biovar I and V which are present in other parts of the world
. References
l. Kelman A, 1954. Phytopathology 44, 693-95
. 2 .Sunaina V, Kishore V, Shekhawat GS, 1997. Potato Research 40, 163-68.