Isolation and identification of native bacteria of the genus Bacillus Cohn antagonistic to pathogenic strains of Fusarium Link. in calla

Abstract

The production of colored calla (Zantedeschia spp. Spreng) in Chile involves an intensive system, usually under greenhouse conditions. This type of production can lead to the presence of diseases, such as those caused by fungi included in the genus Fusarium Link. The objective of this study was to isolate bacteria of the genus Bacillus Cohn that are able to inhibit the growth of 60 strains of fungi Fusarium oxysporum Schlecht and F. solani (Mart.) Sacc., under in vitro conditions. Both of these fungi cause wilt in calla plants growing under greenhouse conditions. Bacteria of the genus Bacillus were isolated from calla stems, tubers, flowers and root samples. All isolates were challenged to 60 strains of both species of Fusarium. Tests were performed on Petri dishes containing potato dextrose agar. Of the 138 Bacillus spp. isolated and tested, only 6 inhibited all Fusarium species evaluated. Five of these were obtained from a stem sample and one from a root sample. Scanning electron microscopy showed that these Bacillus isolates caused morphological changes to the Fusarium species. The isolates of Bacillus were then tested to detect pathogenicity on calla tuber tissue. Results showed that strains grew on the surface due to starch availability without causing damage to calla tubers. The isolates studied were found to belong to the group Bacillus subtilis Ehrengberg.