Bioprospecção de macroalgas marinhas e plantas aquáticas para o controle da antracnose do feijoeiro

Abstract

The goal of this work was to test the local, residual as well as systemic effect of extracts from 17 marine seaweeds and two aquatic plant species against the bean anthracnose. For that, specimens were collected, identified, dried into an oven at 50°C for 48 h, ground to powder and their compounds extracted with ethanol. Bean plants (Phaseolus vulgaris cv. Uirapuru) were grown in pots under greenhouse conditions. The 19 extracts were shared into two independent groups for screening and comparison in a completely randomized design, with five replications (pot with 3 plants). Plants at the first trifoliolate leaf stage were sprayed with extracts at concentration of 50 mg dry weight/mL. To assess the local effect, plants were inoculated with a suspension of 1.2 × 106 conidia/mL 4 h after the treatment, whereas to study the residual and systemic effects, inoculation was performed after 7 days. Disease severity was evaluated 7 days after inoculation (dai) on either whole plants or the non-treated leaf (systemic effect), using a scale from 1 to 9. Seaweeds and plants which significantly reduced anthracnose were compared in a follow-up experiment evaluated at both 7 and 12 dai. The extract of Bryothamnion seaforthii revealed local effect reducing the anthracnose severity by 35%. Ulva fasciata extract showed residual effect reducing the anthracnose at 12 dai by 22%. Compared to control, only extracts of Lemna sp. and U. fasciata systemically reduced the disease severity at 7 dai by 55 e 44%, respectively. The possible mode of action of these extracts is discussed.