Caracterização morfológica de isolados de Fusarium oxysporum associados ao mal do panamá e inibição in vitro do crescimento micelial por isolados de Bacillus

Abstract

Banana (Musa spp.) is the most consumed fresh fruit in the world and Brazil stands out as the fourth largest producer worldwide. However, its production has been affected by several diseases, among which stands out the Panama disease, whose causal agents are phylogenetic species of fungi that comprise the morphospecies Fusarium oxysporum f. sp. cubense (Foc), and currently stands out among the greatest threats to the world banana industry. The control of this disease consists of the use of resistant varieties and cultural control. Thus, studies related to biological control have shown promise and among the microorganisms used in biological control are bacteria of the genus Bacillus. Thus, the objective of this study was to characterize the morphology of Foc isolates and investigate the in vitro inhibition of mycelial growth by Bacillus isolates. To this end, five isolates of Foc were obtained from symptomatic plants and characterized as to colony coloration variation, mycelial growth and micromorphology. Subsequently, these five isolates were submitted to two in vitro antibiosis tests to verify the antagonist activity of the bacterial strains LPPC159, LPPC170, LPPC265 and LPPC272. All bacterial strains showed ability to inhibit mycelial growth of the fungal isolates when compared to control. However, isolates LPPC170 and LPPC265 showed the highest percentages of inhibition. In the first test, the LPPC170 strain presented inhibition of the mycelial growth of the fungal isolates between 47.3% and 72.1%, while the bacterial isolate LPPC265 presented inhibition of the mycelial growth of the fungal isolates between 47.8% and 70.4%. In the second in vitro antibiosis test, the LPPC170 strain inhibited the mycelial growth of fungal isolates between 55.6% and 67.8%, while the LPPC265 strain inhibited the mycelial growth of fungal isolates between 54.7% and 64.8%. It is concluded that Foc isolates showed most of the typical micromorphological characteristics of the FOSC, and some variations may be caused by the difference between possible species and strains. Bacillus strains inhibited the in vitro mycelial growth of Foc isolates, the most promising bacterial strains being LPPC170 and LPPC265.