Bacillus strains as potential agents for the biocontrol of phytopathogenic fungi Alternaria spp.

Abstract

Plant diseases caused by fungal pathogens can lead to major economic losses in agriculture. Th e genus Alternaria includes saprobic, endophytic and pathogenic species that may cause various plant diseases such as blight disease. Symptoms of Alternaria blight include the presence of irregular, oft en circular, brown to dark brown coloured leaf spots. Alternaria spp. also cause collar rots, stem lesions, tuber and fruit rots of their respective hosts. In addition, bacteria are one of the most frequently biocontrol agents used to protect plants from diseases. Bacillus species control disease through a variety of mechanisms. Bacterial antagonists might act as inhibitors of growth, development and reproduction of pathogen, or as inducers of host resistance in plant. Th e objective of this study was to examine in vitro antifungal activity of ten antagonistic Bacillus strains from collection of Department for Microbiology of Institute of Field and Vegetable Crops, Novi Sad. Strains were originally isolated from the soil samples collected from several localities of Vojvodina Province. Antifungal activity of Bacillus strains against Alternaria padwickii, A. dauci and A. linicola, obtained from rice, carrot and linseed, respectively was tested using a dual plate assay. Th e results confi rmed that all tested Bacillus strains showed antifungal acivity against Alternaria spp. Th e highest antagonistic activity was exhibited by B. pumilus B11 (45.71% to 51.25%), B. subtilis B13 (45.71% to 49.37%) and B. subtilis B32 (45.71% to 52.08%), while B. pumilus B23 had the weakest antifungal activity. B. safensis B2 (35.24% to 48.33%), B. pumilus B21 (40.95% to 48.75%) and B. pumilus B22 (33.50% to 49.17%) also demonstrated good antifungal potential. A. dauci was the most sensitive fungus, while the most resistant was A. linicola. Obtained results indicate the possibility of usage of the most eff ective Bacillus strains as potential biocontrol agents of plant diseases caused by Alternaria spp