Bioprospecção de isolados de leveduras e bactérias, provenientes da secreção oral de Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) coletada em campo, antagônicos a Fusarium verticillioides (Nirenberg, 1976) e Colletotrichum falcatum (Went, 1893)
Abstract
Insect symbionts may have unknown functions in the interaction between insect-plant
and insect with microorganisms that co-inhabit the same space. The objective of this
study was to investigate the antagonism potential of symbiont microbiota from oral
secretion D. saccharalis collected in the field, against Fusarium verticillioides and
Colletotrichum falcatum pathogens commonly found inside the cane. For this, 4° and
5° instar caterpillars were collected inside sugarcane varieties RB-835 054 and SP-
813 250, and brought to the lab inside the cane stalks. The microbiota of oral
secretion was transferred to two selective media, NA (nutrient agar) for bacteria and
DRBC (dicloran Rose Bengal Chloramphenicol) for yeast. Based on morphology and
coloration of the colonies twenty colonies of bacteria and yeast were selected. Four
culture media were tested in co-cultivation of F. verticillioides and C. falcatum versus
bacteria or yeast isolates: PDA (potato, dextrose, agar), YEPD (yeast extract,
peptone, dextrose), CCS (supplemented cane broth) and NA (Nutrient Agar). The
most suitable culture medium for growth of most microorganisms was BDA.
Antagonism potential of 82 bacterial isolates and 87 yeast isolates to C. falcatum and
F. verticillioides was assessed using a visual scale of categories 1 to 4, with 4 being
the maximum degree of antagonism. Isolates that allocated category greater than or
equal to 2 were evaluated in co-culture with C. falcatum and F. verticillioides as the
percentage of growth inhibition. It was possible to identify four isolates of bacteria
which have the potential to inhibit growth of pathogens and 9 isolates with the same
potential but with much lower percentages. These results demonstrate that some
isolates of bacteria and yeast may influence the relationship between the bit-rot
complex and sugarcane plant, may in future be used as a biological control of these
pathogens or have some molecules of biotechnological interest extracted and
purified.