Fungos associados às sementes de goiaba-serrana: detecção, efeitos na qualidade das sementes, transmissão para plântulas e controle

Abstract

Acca sellowiana (Berg) Burret is a fruit tree species native to southern Brazil and northeastern Uruguay, which is attracting great interest due to the high economic potential of its organoleptic fruit. The main mode of transmission of Acca sellowiana is sexual route, so use lots of high quality seeds is one of the most important success factors of a culture. This paper aims to compare three forms of detection of fungi on seeds of Acca sellowiana - treated or not treated superficial disinfection; analyze the effect of fungi on seed quality, determine potential losses in the early development of seedlings of this species, and evaluate the efficiency of fungicides and biological control of fungi associated with seeds, especially Colletotrichum gloeosporioides, and to determine the possible harmful effects of treatments for seed germination. The seeds were from four counties in the state of Rio Grande do Sul (Arroio do Tigre, Cachoeira do Sul, Camaquã e Venâncio Aires) and three counties in the state of Santa Catarina (Concórdia, Lages e São Joaquim). The health test seed culture media Potato Dextrose Agar (PDA), V8 (tomato juice) and the method of "Blotter Test" were tested. For physiological analysis of seed germination test was carried out at 25 °C and a photoperiod of 12 h for 30 days and evaluated the percentage and speed of germination (Germination Speed Index). Initially, seeds were split, with a portion subjected to surface sterilization with 70% alcohol, 1 % sodium hypochlorite with subsequent washing in distilled water and another not. To evaluate the samples was conducted seedling emergence test in the nursery for 60 days. 200 seeds arranged in eight replicates of 25 seeds (4 replicates subjected to sterilization and 4 without sterilization) were used for each source. For control of fungi associated with seeds, we used fungicides capture, carbendazim, carbendazim + thiram, carboxim + thiram and commercial product Trichodermax (at a concentration of 1.5 x 109 viable spores per ml of Trichoderma asperellum product) at recommended doses for large crops. The experiments were conducted from the randomized design, with four replications of 25 seeds per treatment. Data were evaluated at a level of significance α = 0.05. It was concluded that agarized media are more sensitive in the detection of fungi in seeds of Acca sellowiana. Aspergillus sp. C. gloeosporioides, Fusarium sp. Penicillium sp. and Phomopsis sp. are associated with non-germinated seeds of Acca sellowiana, being detrimental to their quality. C. gloeosporioides and Fusarium sp. are transmitted from seeds to seedlings, causing necrotic lesions on cotyledons and poor root formation respectively. The chemical and biological treatments to reduce the incidence of fungal in Acca sellowiana seeds, however, chemical treatments adversely affect the germination of seeds.