Preparation, characterisation and cell viability of encapsulated Trichoderma asperellum in alginate beads.

Aim: The encapsulation of Trichoderma asperellum BRM-29104 using Ca-alginate matrix was evaluated.Methods: Intact and freeze-dried beads containing submerged conidia and microsclerotia (MS) of T. asperellum grown in liquid culture were prepared and characterised. Beads were stored at 8, 25, and 35 °C over 120 days.Results: The mean sizes of beads before and after freeze-drying were 2.5 ± 0.2 mm and 1.5 × 1.1 mm (± 0.1 mm), respectively. Freeze-dried beads stored at 8 °C were more effective in maintaining conidia concentration, while MS concentrations yielded 102 MS/g for both beads at 8 and 25 °C. The concentration of viable cells in freeze-dried beads stored at 8 °C attained 3.0 × 108 CFU/g after 120 days. FIRT analysis showed an interaction between the alginate and the cell wall of the fungus.Conclusion: These findings support the use of alginate beads followed by freeze drying and cold storage for maintenance of viability of T. asperellum.

Diversity and Pathogenicity of Rhizoctonia Species from the Brazilian Cerrado.

Eighty-one Rhizoctonia-like isolates were identified based on morphology and nuclei-staining methods from natural and agricultural soils of the Cerrado (Brazilian savanna). The nucleotide similarity analysis of ITS1-5.8S-ITS2 regions identified 14 different taxa, with 39.5% of isolates assigned to Waitea circinata (zeae, oryzae, and circinata varieties), while 37.0% belonged to Thanatephorus cucumeris anastomosis groups (AGs) AG1-IB, AG1-ID, AG1-IE, AG4-HGI, and AG4-HGIII. Ceratobasidium spp. AG-A, AG-F, AG-Fa, AG-P, and AG-R comprised 23.5%. Rhizoctonia zeae (19.8%), R. solani AG1-IE (18.6%), and binucleate Rhizoctonia AG-A (8.6%) were the most frequent anamorphic states found. Root rot severity caused by the different taxa varied from low to high on common beans, and tended to be low to average in maize. Twenty-two isolates were pathogenic to both hosts, suggesting difficulties in managing Rhizoctonia root rots with crop rotation. These results suggest that cropping history affects the geographical arrangement of AGs, with a prevalence of AG1 in the tropical zone from central to north Brazil while the AG4 group was most prevalent from central to subtropical south. W. circinata var. zeae was predominant in soils under maize production. To our knowledge, this is the first report on the occurrence of W. circinata var. circinata in Brazil.

Efeito de compostos orgânicos sobre podridões radiculares no feijoeiro comum / Effect of organic compounds on root rots of common beans

Os fungos habitantes do solo, Rhizoctonia solani e Fusarium solani f.sp. phaseoli, constituem um complexo etiológico com interação sinérgica, responsável por perdas de produtividade de até 50% em feijoeiro. A matéria orgânica de diversas origens é utilizada na agricultura visando, entre outros motivos, estimular a atividade microbiana para limitar a atividade dos fitopatógenos habitantes do solo. O presente trabalho teve como objetivo avaliar o efeito de doses de compostos orgânicos sobre podridões radiculares causadas por R. solani e F. solani f.sp. phaseoli, em feijoeiro cultivar Pérola, em condições de campo. O delineamento experimental foi de blocos casualizados, em esquema fatorial de 2 x 6. Os compostos orgânicos à base de crotalária (Crotalaria juncea) e grama batatais (Paspalum notatum), associados com cama de frango, foram aplicados no sulco de plantio nas doses de 0, 20, 40, 80, 160 e 320 kg.ha-1. As avaliações de severidade foram realizadas, utilizando-se escala de notas. A maior severidade de F. solani f.sp. phaseoli em plantas de feijoeiro foi observada sob efeito da dose de 320 kg.ha-1 de crotalária + cama de frango e 80 kg.ha-1 para o composto à base de grama batatais + cama de frango. Para R. solani, os compostos orgânicos e doses não influenciaram a severidade de R. solani. A dose de 80 kg.ha-1, independente do composto orgânico, proporcionou a melhor produtividade.

The soil inhabiting fungi, Rhizoctonia solani and Fusarium solani f.sp. phaseoli, constitute an etiological complex with synergic interaction, responsible for up to 50% losses in common beans. Organic matter of diverse sources is used in agriculture to stimulate microbial activity limiting the activity of soil inhabiting plant pathogens, among other uses. This study evaluated the effect of organic compound doses on root rots caused by R. solani and F. solani f.sp. phaseoli, in common beans, cultivar Pérola, in field conditions. The experimental design was randomized blocks, as a 2 x 6 factorial. The organic compounds of Crotalaria juncea or Paspalum notatum, associated with poultry bedding, were applied in the planting furrow at the doses de 0, 20, 40, 80, 160 or 320 kg.ha-1. Evaluations of severity were done using a rating scale. Greater severity of F. solani f.sp. phaseoli in common bean plants were observed at the dose of 320 kg.ha-1 crotalaria + poultry bedding e 80 kg.ha-1 with paspalum compound + poultry bedding. The organic compounds and doses did not affect R. solani severity. The dose of 80 kg.ha-1, regardless of the organic compound, resulted in greater yield.

Potencial antagônico de Trichoderma spp. originários de diferentes agroecossistemas contra Sclerotinia sclerotiorum e Fusarium solani / Antagonist potential of Trichoderma spp. from distinct agricultural ecosystems against Sclerotinia sclerotiorum and Fusarium solani

A partir de 40 amostras de solo, provenientes dos estados do Rio Grande do Sul, Minas Gerais, São Paulo, Bahia, Goiás e Tocantins, uma coleção de 230 isolados monospóricos de Trichoderma spp. foi estabelecida, usando o meio seletivo TSM. Com o objetivo de selecionarem-se isolados com potencial para controle biológico de doenças, foram conduzidos testes de pareamento de culturas em meio BDA, a 20 ºC para Sclerotinia sclerotiorum e a 25 ºC para Fusarium solani f.sp. phaseoli. Antagonismo contra os dois patógenos foi observado em 10 por cento dos isolados. Avaliações ao microscópio eletrônico de varredura de sete isolados selecionados in vitro mostraram que nem todos promoveram o hiperparasitismo dos patógenos, sugerindo a existência de outros mecanismos de antagonismo, como antibiose ou competição.

From 40 soil samples collected in the Rio Grande do Sul, Minas Gerais, São Paulo, Bahia, Goiás and Tocantins states, Brazil, a collection of 230 monosporic isolates of Trichoderma spp. was established using TSM selective media. In order to select efficient isolates for biological control, dual culture tests were carried out on PDA media at 20 ºC for Sclerotinia sclerotiorum and at 25 ºC for Fusarium solani f.sp. phaseoli. From the whole collection, 50 isolates presented antagonism against F. solani and 111 isolates to S. sclerotiorum. The antagonism against both pathogens was found in only 10 percent of the isolates. Scanning electron microscopy assessments with seven in vitro selected isolates showed that not all promoted hyperparasitism on the pathogens, suggesting the existence of other mechanisms of antagonism, as antibiosis or competition.