Biological Control of Early Blight on Potato Caused by Alternaria Solani by Some Bioagents

Early blight (Alternaria solani) is a potential disease of tomato that reduces its production globally both in conventional and tunnel cultivations. Due to variability in pathogenic isolates, prolonged active disease cycle phase and broad host range early blight is very difficult to manage. 8 microorganisms as a bioagent exhibiting inhibitory affects against Alternaria solani, were screened for their activity towards A. solani by a dual culture in vitro assay and in vivo (whole plant) test in vitro studies indicated that the microorganism’s strains strongly inhibited the mycelial growth of the pathogen. The effect of microorganism’s strains on the mycelial growth (mm) of the pathogen proved to be highest with Trichoderma sp. (0.55) followed by Pseudomonas brassicacearum (0.74) and Pseudomonas jessenii (0.81) on the high concentration (106 cells ml-1) compared to the control (2.30). On the other hand, Bacillus mycoides (2.14) in vivo studies 9 microorganism’s strains were applied in two different application (foliar – soil) and two different varieties (Labella – Romano). The results showed significant reductions in the disease severity (%) with the treatment by Trichoderma sp (2%) followed by Bacillus thuringiensis (3%) and Bacillus mycoides (5%) compared with the control (46%) of Romano variety, while there were a less significant reductions in the disease severity (%) with the treatments compared with the control (16%) of Labella variety . The efficacy of antagonists to suppress the early blight disease varied in respect to the time and type of application. Keywords—Altrnaria solani, biocontrol, Eearly blight, microorganisms, potato