Reação de progênies de maracujazeiro-azedo ao Colletotrichum gloeosporioides e biocontrole da antracnose com Trichoderma spp.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

REACTION OF SOUR PASSIONFRUIT LINEAGES TO Colletotrichum gloeosporioides AND BIOCONTROL OF ANTHRACNOSE BY Trichoderma spp. ABSTRACT Given the importance of the passion fruit crop, where Brazil is the leading world producer, the present work had the objective to evaluate the reaction of lineages of Sour Passionfruit (Passiflora edulis Sims f. flavicarpa Deg.) to the fungus Colletotrichum gloeosporioides (Penzig) Saccardo, and to evaluate isolates of Trichoderma spp. as biocontrol agents of anthracnose. With the aim of producing inoculum in sufficient quantities for the assays, experiments were performed, using liquid fermentation, with four isolates of the fungus. The work was developed in the Phytopathology section of the Biological Station of the University of Brasilia and in the Phytopathology Laboratory of the Biological Control Department of Embrapa Genetic Resources and Biotechnology Center - CENARGEN in 2005. Three isolates of C. gloeosporioides were used in this study (CEN 419, CEN 421 and CEN 433) which were originally obtained from leaves and fruits, collected in supermarkets and orchards in Federal District (DF), while one (CEN 422) was kindly donated by UFRPE. The isolates of Trichoderma were obtained from the Collection of Fungi for Biological Control of Phytopathogens at CENARGEN. The C. gloeosporioides isolates had been previously evaluated in their pathogenicity using the susceptible lineages Yellow Master FB- 100 and MAR#20-13, while the isolate CEN419, was selected for using in all experiments. In the first experiment, 72 lineages of sour passionfruit were evaluated for their resistance to anthracnose, in the greenhouse. A randomized-block design was used, with four replicates and six plants for each replicate. The pathogen was cultivated in liquid medium and the spores later collected by centrifugation. Aqueous suspensions were then prepared at 5 x 106 spores/ml which were applied to wounds previously established by abrasion with fine steel wire brushes. The inoculated plants were kept at 60 -100% humidity and evaluated as to the severity and incidence of disease 20 days and again, at intervals of 7 days. The lineages showed significant differences in their susceptibility to C. gloeosporioides in the seven evaluations. In a second experiment, the antagonistic potential of 20 Trichoderma spp. isolates against C. gloeosporioides was evaluated, in vitro and in vivo. In tests of diffusible metabolites and in plate confrontations, all the Trichoderma isolates inhibited the growth of the pathogen. The in vivo experiment was carried out in the greenhouse using a randomized xix block design, with 4 repetitions, whe re a repetition cons isted of 4 polyethylene bags (1.5kg) with 2 plants per bag, with a total of 8 plants per block. Four different periods of application of the isolates of Trichoderma for the control of anthracnose were tested: P1 = inoculated with Trichoderma 24 hours before the pathogen; P2 = inoculated with Trichoderma 24 hours after the pathogen; P3 = Trichoderma inoculated simultaneously with the pathogen; P4 = Trichoderma inoculated seven days after the pathogen and as control treatments; P5 = Trichoderma only; P6 = Colletotrichum only and P7 = distilled water only. Three evaluations were made, at intervals of 12 days. The action of the isolates of Trichoderma was expressed in terms of fresh and dry weights of the aerial plant parts and roots. P3 was found to be the period producing greatest of control of anthracnose. In comparison with controls, it was observed that in the plants treated with the Trichoderma isolate, CEN 151 had an increased growth of aerial parts. In the third experiment, two assays were carried out to evaluate the mycelial growth and sporulation of C. gloeosporioides isolates in liquid media. In the first test, the behavior of four isolates of C. gloeosporioides was observed for their growth and sporulation in different liquid media. Each treatment was repeated four times, in a randomized 4x3 block. There was a significant interaction between the particular isolates and different media in terms of quantity of conidia produced and dry biomass. The isolates with greatest production of conidia were CEN 419 and CEN 422, in potato-dextrose medium (BD). In the second assay, the development of isolate CEN 419 was evaluated in BD medium with the addition of ten different concentrations extract of yeast extract, again in relation to the production of conidia and dry biomass. A significant effect on production of dry biomass was observed. There was a significant difference in the production of conidia only between treatments 1 (BD) and 5 (0.4% yeast extract).

ASSUNTO(S)

passiflora edulis sims f. flavicarpa biological control ciencias agrarias produção de inóculo. production of inoculum. passiflora edulis f. flavicarpa resistência controle biológico resistance

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