Biological Control of Pseudomonas syringae pv. syringae, the Causal Agent of Basal Kernel Blight of Barley, by Antagonistic Pantoea agglomerans

Abstract

Strains of Pantoea agglomerans (synanamorph Erwinia herbicola) suppressed the development of basal kernel blight of barley, caused by Pseudomonas syringae pv. syringae, when applied to heads prior to the Pseudomonas syringae pv. syringae infection window at the soft dough stage of kernel development. Field experiments in 1994 and 1995 revealed 45 to 74% kernel blight disease reduction, whereas glasshouse studies resulted in 50 to 100% disease control depending on the isolate used and barley cultivar screened. The efficacy of biocontrol strains was affected by time and rate of application. Percentage of kernels infected decreased significantly when P. agglomerans was applied before pathogen inoculation, but not when coinoculated. A single P. agglomerans application 3 days prior to the pathogen inoculation was sufficient to provide control since populations of about 10(7) CFU per kernel were established consistently, while Pseudomonas syringae pv. syringae populations dropped 100-fold to 2.0 x 10(4) CFU per kernel. An application to the flag leaf at EC 49 (before heading) also reduced kernel infection percentages significantly. Basal blight decreased with increasing concentrations (10(3) to 10(7) CFU/ml) of P. agglomerans, with 10(7) CFU/ml providing the best control. For long-term preservation and marketability, the survival of bacterial antagonists in several wettable powder formulations was tested. Over all formulations tested, the survival declined between 10- to >100-fold over a period of 1.5 years (r = -0.7; P = 0.000). Although not significant, storage of most formulations at 4 degrees C was better for viability (90 to 93% survival) than was storage at 22 degrees C (73 to 79%). However, long-term preservation had no adverse effect on biocontrol efficacy.

Microbiology of the Phyllosphere

“…These antagonists were also shown to move readily from inoculated to noninoculated flowers, thereby facilitating biocontrol in flowers that otherwise would support relatively few other indigenous bacteria (49,88). Several other recent studies have revealed the in vitro antagonism and/or competitive interactions of potential antagonistic bacteria with bacterial and fungal plant pathogens on plants (15,57,79,106,117,125,126). They illustrate the considerable potential for further development of useful biological control organisms for diverse diseases.…”

Post-harvest biological control by Pantoea agglomerans (CPA-2) on Golden Delicious apples

“…syringae (Braun-Kiewnick et al 2000) and Monilinia oxycocci (Voland et al 1999). However, the exact mechanism by which P. agglomerans suppresses diseases is not clear.…”

Are we killing the rain? Meditations on the water cycle and, more particularly, on bioprecipitation

“…5. P. syringae received sustained research attention, therefore, as an aggressive and successful pathogen responsible for basal kernel blight in respect to barley (Braun-Kiewnick et al 2000); as a principal causal agent of halo blight in many bean cultivars (Bozkurt and Soylu 2011); as a prolific cause of bacterial shoot blight in tea plants, widely infecting them in tea-growing countries such as Japan (Tomihama et al 2009); and as an antagonist of tomato plants, on which it causes a blight called bacterial speck across the world (see e.g. de-Bashan 2002a, 2002b with the author.…”