Effects of avirulent bacteriocin‐producing strains of Pseudomonas solanacearum on the control of bacterial wilt of tobacco

Abstract

Root systems of tobacco dipped in suspensions containing 2 × 109 colony forming units (CFU)/ml of avirulent bacteriocin‐producing strains (ABPS) of Pseudomonas solanacearum and assayed immediately after planting in steam‐sterilized soil had 8 × 106 CFU/root system of ABPS. The bacterial population declined to an average of 5·3 × 105 CFU/root system after 30 days. Roots of seedlings dipped in bacterial suspensions of ABPS were more effectively protected against wilt caused by P. solanacearum than those dipped in suspensions of an avirulent nonbacteriocin‐producing strain (ANBPS). Lipopolysaccharide (LPS) isolated from one ABPS (121) inhibited the attachment of bacteria on roots by 70% but had no effect on the reduction of wilt, whereas bacterial cells significantly reduced the disease severity as compared to LPS or water treatment. In steam‐sterilized soil containing a 1:1 mixture (5 × 105 CFU/g of oven‐dried soil) of ABPS 121 or 237 and the virulent strain K‐60, ABPS 121 reduced multiplication of the virulent strain in soil and in the rhizosphere of seedlings. When roots of seedlings were dipped in a suspension of 2 × 109 CFU/ml of ABPS before planting, root colonization by the virulent strain added to steam‐sterilized soil at 2 × 106 CFU/g of oven‐dried soil was significantly reduced. When roots were dipped in a suspension of ABPS and assayed 20 days after planting, 98% of the bacterial population was found in the original zone of inoculation and only 2% was detected in new growths of the root system. Plants which were grown in soil infested with ABPS 121 or K‐60 had both strains present at variable populations along all sections of roots.

Biological control of bacterial wilt caused by Pseudomonas solanacearum in India with antagonistic bacteria

“…Protection obtained by these attempts to induce resistance was inconsistent and was dependent largely on environmental conditions (McLaughlin and Sequeira, 1988). Bacteriocinogenic strains of P. solanacearum protected rootdipped tobacco plants against virulent strains of P. solanacearum (Chen and Echandi, 1984;Chen et al, 1982).…”

Effect of weakly-virulent bacteriocin-producing strain of Pseudomonas solanacearum on the protection of tobacco plant from bacterial wilt.

“…Therefore, studies on the biological control, as other possible means for control, is necessary to obtain more efficient control of bacterial wilt. Recently, a number of attempts to control bacterial diseases with bacteriocin-producing strains have been made2, 3,11,12,15,19). Among them, non-pathogenic bacteriocin-producing strain 84 of Agrobacterium radiobacter has been successfully used for the control of crown gall disease12, 14).…”

Tropical Strains of Ralstonia solanacearum Outcompete Race 3 Biovar 2 Strains at Lowland Tropical Temperatures

“…These proteins had no effect on seven other bacterial species, indicating that they are putative bacteriocins, proteins that specifically target conspecific or closely related strains (28,50). R. solanacearum has long been known to produce bacteriocins, but their biological role(s) was unknown (38,(51)(52)(53). Many plant-associated bacteria make bacteriocins, such as agrocin, produced by Agrobacterium radiobacter strain K84.…”