Controle de Cladosporium herbarum e promoção de crescimento do feijoeiro pelo emprego de Trichoderma harzianum

Abstract

The fungus Cladosporium is associated with common bean seeds during storage, being able to inflict damage on germination and vigor. The objective of this study was to evaluate five isolates of Trichoderma harzianum (CEN287, CEN288, CEN289, CEN290 and CEN316) in control of Cladosporium herbarum and promoting early seedling growth of common bean. For this purpose: (1) it was carried out a micromorphological characterization of C. herbarum found on seeds of common bean cv. ‘Perola’, Ipameri, Goiás, Brazil; (2) it was evaluated the parasitic capacity and in vitro effect of volatile (vm) and thermostable non-volatile metabolites (tnvm) from antagonists against C. herbarum in Petri dishes; (3) it was evaluated the effect of the antagonists and its metabolites (vm and tnvm) on seeds contaminated with C. herbarum (2 mL suspension at 2.5 x 108 conidia 100 g-1 seeds and 2 mL of tnvm 100 g-1 seeds, respectively) and; (4) it was evaluated the growth and biomass of common bean seedlings by seed treatment with autoclaved metabolites (AM) and conidia suspension (CS) of antagonist, at the same doses previously specified. After micromorphologic observations of the characteristics of conidia, it was found that they had 7.2 to 10.4 x 3.6 to 4.2 µm (8.1 x 4.0 µm) and combined with other characteristics, the fungus was identified as C. herbarum. Concerning the control, it was founded the hiperparasitism of T. harzianum on C. herbarum in a light microscope from the visualization of the fungi structures from samples taken from the same confrontation area. Furthermore, in tests with vm, CEN288 inhibited in 59% the in vitro growth of C. herbarum, while for tnvm all isolates were similar, ranging from 29 to 40% of pathogen growth inhibition. Concerning the use of cs in the seed treatment, all isolates of T. harzianum gave control of the pathogen, which ranged 67 to 77%. Still in seed treatment, am of CEN289 and CEN290 provide the better control (75 and 73 %, respectively). Regarding the experiments evaluating the potential of T. harzianum in promoting the growth of bean, CEN289 and CEN290, respectively, differ from the others such the length of roots (12.57 and 13.31 cm, control: 8.94 cm) and stem (9.10 and 8.77 cm, control: 7.05 cm) in experiments using sc. Besides, CEN289 and CEN290, respectively, provided the highest total biomass in the experiment with CS (127.45 and 117.91 g, control: 95.23 g) and AM (133.43 and 128.13, control: 70.39 g). Seedlings grown from seeds treated with CEN289 and CEN290 showed intense accumulation of biomass and vigorous vegetative growth, reaching maturity in the shortest.