Semi-selective medium for Fusarium graminearum detection in seed samples

Abstract

Several fungal species belonging to the genus Fusarium cause agriculturally important diseases in a variety of plants. The pathogen Fusarium graminearum Schwabe, teleomorph Gibberella zeae (Schwein.) Petch, is the causal agent of wheat (Triticum aestivum L.) head blight also known as giberela ear rot and maize (Zea mays L.) stem and cob rot (2). This parasite has a wide geographical distribution and attacks a large number of crops causing qualitative and quantitative damage, which can affect agricultural production (6). Head blight of wheat is particularly important in the state of Rio Grande do Sul, Brazil, where wheat is extensively grown (13). In the south of Brazil ecological group II occurs (1, 11). A detailed knowledge of the survival and dissemination mechanisms of pathogenic fungi is important in developing control measures for difficult-to-control fungal plant pathogens. Selective or semi-selective culture media, which act by excluding non-target fungi and bacteria, are important tools for fungal isolation, purification and quantification and for investigating the detailed biology of fungi, being especially useful for slow growing organisms (3, 4,12). However, the media currently available for Fusarium do not meet criteria such as sensitivity and selectivity and ability to allow the development of Fusarium colonies with consistent morphological characteristics and pigmentation (9).Several selective or semi-selective culture media have been developed for the isolation of Fusarium species, including the most widely-used culture medium Nash-Snyder agar (NSA) (7). However, the NSA medium often does not maintain the ABSTRACTFungi of the genus Fusarium cause a variety of difficult to control diseases in different crops, including winter cereals and maize. Among the species of this genus Fusarium graminearum deserves attention. The aim of this work was to develop a semi-selective medium to study this fungus. In several experiments, substrates for fungal growth were tested, including fungicides and antibiotics such as iprodiona, nystatin and triadimenol, and the antibacterial agents streptomycin and neomycin sulfate. Five seed samples of wheat, barley, oat, black beans and soybeans for Keywords: Small grains scab, head blight, Gibberella zeae, seed assay.quarter dextrose agar (1/4PDA; potato 50g; dextrose 5g and agar 20g ), either un supplemen ted or supplemented with various concentrations of the antimicrobial agents cited above. The selected components and concentrations (g.L -1 ) of the proposed medium, Segalin & Reis agar (SRA-FG), were: iprodiona 0.05; nystatin 0,025; triadimenol 0.015; neomycin sulfate 0.05; and streptomycin sulfate, 0.3 added of ¼ potato sucrose agar. In the isolation from seeds of cited plant species, the sensitivity of this medium was similar to that of NSA but with de advantage of maintaining the colony morphological aspects similar to those observed in potato-dextrose-agar medium. RESUMOOs fungos do gênero Fusarium causam doenças de difícil controle, em diferentes culturas, inclusive...

Anthesis, the infectious process and disease progress curves for fusarium head blight in wheat

“…At weekly intervals, PEA were collected, plated on Petri dishes containing potato dextrose agar (1/4PDA) and Segalin & Reis (23) semi-selective medium and incubated in a growth chamber at 12h photoperiod for seven days at 25 o C; subsequently, under a stereoscope microscope, fungi that colonized the anther were identified.…”

Identificação e quantificação de fungos associados a sementes de azevém (Lolium multiflorum Lam.)

“…Para o preparo dos meios de cultura foram utilizados os protocolos descritos em Fernandez (9) para o meio Batata-Dextrose-Ágar (BDA), Reis (17) para o meio semi-seletivo de Reis, e Segalin & Reis (20), para o de Segalin & Reis. As sementes foram plaqueadas com auxílio de pinça previamente flambada.…”

Viabilidade e controle de Fusarium graminearum em sementes de cevada

“…Por outro lado, Garcia Junior et al (10) determinaram que o fungicida triadimenol (13,5g do i.a./ 100 Kg de sementes) em tratamento de sementes de trigo demonstrou eficiência de controle de 62% para F. graminearum. Neste trabalho os autores salientam que apesar do triadimenol não ser um fungicida recomendado para o controle de F. graminearum, o mesmo indicou eficiência na inibição ou ação fungistática sobre o desenvolvimento do fungo e salienta-se que o triadimenol é componente de meio de cultura semi-seletivo para F. graminearum (26). Entretanto, o uso dos triazóis no manejo do fungo deve ser explorado, uma vez que no Brasil, isolados do complexo F. graminearum tem se mostrado sensíveis aos triazóis provavelmente devido às características intrínsecas do patógeno ou a pressão de seleção pelo uso crescente deste grupo químico, isolado ou em misturas comerciais, para o controle de várias doenças de cereais de inverno, tais como o trigo (27).…”