Resumo

Endophytic fungi live inside plants, apparently do not cause any harm to their hosts and may play important roles in defense and growth promotion. Fungal growth is a routine practice at microbiological laboratories, and the Potato Dextrose Agar (PDA) is the most frequently used medium because it is a rich source of starch. However, the production of potatoes in some regions of the world can be costly. In the present study, we used leaves from the guarana (a tropical plant from the Amazon region) and the olive (which grows in subtropical and temperate regions) to isolate endophytic fungi using PDA and Manihot Dextrose Agar (MDA). Potato Dextrose Agar (PDA) was prepared in our laboratory, and consisted of potato extract (200 g), dextrose (20 g), agar (15 g), and distilled water to a final volume of one liter with a pH of 6.5. Manihot Dextrose Agar (MDA) was prepared using the same method as PDA but with 200 g of cassava instead of potato Cassava (Manihot esculenta) was evaluated as a substitute starch source. For guarana, the endophytic incidence (EI) was 81% and 96% on PDA and MDA media, respectively, and 31% and 40% for olive, respectively. The fungal isolates were sequenced using the ITS- rDNA region. The fungal identification demonstrated that the isolates varied according to the host plant and media source. In the guarana plant, 13 fungal genera were found using MDA and six were found using PDA. In the olive plant, six genera were obtained using PDA and 4 were obtained using MDA. The multivariate analysis results clearly demonstrated the highest fungal diversity from guarana when using MDA medium. Interestingly, some genera were isolated from one specific host or in one specific media, suggesting the importance of these two factors in fungal isolation specificity. This study clearly indicated that cassava is a feasible starch source that could serve as a potential alternative medium to potato medium.