Determination of Races and Biovars of Ralstonia solanacearum Causing Bacterial Wilt Disease of Potato

Abstract

A survey was carried out in some selected potato growing districts of Bangladesh during December to February 2011 to know the status of bacterial wilt of potato caused by Ralstonia solanacearum in terms of its incidence and severity. The results showed that the highest wilt incidence was recorded in Munshigonj (22.65%), followed by Nilphamari (19.98%) and the lowest incidence was recorded in Jamalpur (9.07%). The highest bacterial wilt severity was recorded in Munshigonj (3.80), while the lowest wilt severity was recorded in Jamalpur (2.90). A total of 44 isolates (R. solanacearum) were obtained from the wilted potato plant samples i.e. 20 from Munshigonj, 17 from Nilphamari and 7 from Jamalpur and the isolates were divided into three groups. The production of pink or light red colour with whitish margin on TZC medium by the bacterial isolates indicated all groups of R. solanacearum isolates were virulent. The results of pathogenicity test revealed that all groups of R. solanacearum isolates were able to cause wilt symptoms in potato plants and brown rot symptoms in potato tuber. On the other hand, all biochemical tests were used for the identification of R. solanacearum isolates. The biovar test using the oxidization of disaccharides (sucrose, lactose, maltose) and sugar alcohols (manitol, sorbitol and dulcitol) by R. solanacearum isolates confirmed that all groups of R. solanacearum isolates belong to biovar III. The race identification of R. solanacearum isolates by pathogenicity test on brinjal, tomato, tobacco and chilli indicating a narrow host range (only in potato) and were categorized in race 3. Therefore, the R. solanacearum isolates causing bacterial wilt of potato in Bangladesh were belonging to Biovar III and Race 3.

Isolation and Characterization of Ralstonia solanacearum Causing Bacterial Wilt of Solanaceae Crops

“…In the present study, four isolates belonged to Race 3 while two belonged to Race 1. The findings of the present study are also supported by Buddenhagen et al, (1962), Ahmed et al, (2013), Popoola et al, (2015). R. solanacearum Race 1 strains infect tobacco, tomato, and many other solanaceous crops, and certain diploid bananas.…”

“…The differentiation of biovars of R. solanacearum based on the utilization of carbohydrates was reported previously by Hayward (1964), He et al, (1983), Kumar et al, (1993), Chaudhry and Rashid (2011), Ahmed et al, (2013) andPopoolaet al, (2015). They also observed that, biovar III oxidizes both disaccharides and hexose alcohols, biovar II oxidizes only disaccharides whereas Biovar I oxidizes hexose alcohols only, and biovar IV oxidizes only alcohols.…”

“…On this medium, typical bacterial colonies appear fluidal, irregular in shape, and white with pink centres after 2 to 5 days incubation at 28ºC as reported by Champoiseau (2008). R. solanacearum produced fluidal colonies with pink or light red color on TZC media after 24 hours of inoculation as reported previously by Rahman et al, (2010), Ahmed et al, (2013). Denny and Hayward (2001) identified race of R. solanacearum by host specificity with infiltration/inoculation methodology used as simple and quick means of determining the race of any particular virulent isolate of this pathogen (Lozano and Sequiera, 1970;Lemessa and Zeller, 2007).…”

Isolation and Characterisation of Ralstonia Solanacearum Strains of Tomato Wilt Disease from Maseno, Kenya

“…These results could be due to the outer membrane of Gram-negative bacteria being readily disrupted on exposure to 3% KOH releasing the viscous DNA according to Ahmed, et al [7] who performed a similar test on R. solanacearum causing bacterial wilt disease of potato in Bangladesh. Solubility test confimed that R.solanacearum isolates were Gram negative.…”

“…[45]; Manasa, et al [46] and Ahmed, et al [7] who classified R. solanacearum into five landraces. Five landraces have been described so far, but they differ in host range, geographical distribution and ability to survive under different environmental conditions.…”