RESUMEN
Macrophomina phaseolina and Rhizoctonia solani are considered two major soil-borne pathogens of Phaseolus vulgaris in Cuba. Their management is difficult, not only due to their intrinsic biology as soil-borne pathogens, but also because the lack of active ingredients available against these pathogens. Actinobacteria, a heterogeneous bacterial group traditionally known as actinomycetes have been reported as promising biological control agents (BCAs) in crop protection. Thus, the main objective of this study was to evaluate the effectiveness of 60 actinobacterial strains as BCAs against M. phaseolina and R. solani in vitro by dual culture assays. The most effective strains were characterized according to their cellulolytic, chitinolytic and proteolytic extracellular enzymatic activity, as well as by their morphological and biochemical characters in vitro. Forty and 25 out of the 60 actinobacteria strains inhibited the mycelial growth of M. phaseolina and R. solani, respectively, and 18 of them showed a common effect against both pathogens. Significant differences were observed on their enzymatic and biochemical activity. The morphological and biochemical characters allow us to identify all our strains as species belonging to the genus Streptomyces. Streptomyces strains CBQ-EA-2 and CBQ-B-8 showed the highest effectiveness in vitro. Finally, the effect of seed treatments by both strains was also evaluated against M. phaseolina and R. solani infections in P. vulgaris cv. Quivicán seedlings. Treatments combining the two Streptomyces strains (CBQ-EA-2 + CBQ-B-8) were able to reduce significantly the disease severity for both pathogen infections in comparison with the non-treated and inoculated control. Moreover, they showed similar effect than that observed for Trichoderma harzianum A-34 and with Celest® Top 312 FS (Syngenta®; Basilea, Switzerland) treatments, which were included for comparative purposes.
RESUMEN
A partir de una mancha de enmohecido de un libro del Archivo "Coronado" con valor patrimonial, se obtuvo una cepa fúngica mediante aislamiento en medio de cultivo micológico. La cepa fué Aspergillus sclerotiorum y se identificó por secuenciación de ADN ribosomal. Se evaluó y confirmó su capacidad deteriorante sobre el papel, al determinar cualitativamente las actividades enzimáticas celulolítica, proteolítica y amilolítica, así como la producción de pigmentos y ácidos. Se evaluaron cuantitativamente sus actividades enzimáticas celulasa total sobre papel de filtro (FPasa) y &beta-endoglucanasa, FPasa y &beta-endoglucanasa; confirmando actividades bajas. Aunque su capacidad deteriorante es discreta, resulta ser amenza para la conservación del documento y potencialmente peligroso para la salud de las personas que consultan y archivan.
By performing a mycological culture, we isolated a fungal strain from a mold patch in a book of great heritage value from the "Coronado" archives. Ribosomal DNA sequencing identified the strain as Aspergillus sclerotiorum. By qualitatively determining its cellulolytic, proteolytic and amylolytic and enzymatic activities, as well as the production of pigments and acids, we confirmed its paper deteriorating abilities. Quantitatively, we evaluated its total cellulase enzyme activities on filter paper (FPase) and &beta-endoglucanase, and FPase and &beta-endoglucanase; confirming low activities. Although its deteriorating abilities are weak, it poses a threat to the preservation of the document and is a potential health hazard to the people who refer to and archive these books.
A partir de uma mancha de bolor de um livro do Arquivo "Coronado" com valor patrimonial, obteve-se uma cepa fúngica mediante isolamento em meio de cultura micologica. A cepa foi Aspergillus sclerotiorum e identificou-se por sequenciação de ADN ribossomal. Avaliou-se e confirmou-se a sua capacidade deteriorantesobre o papel, ao determinar qualitativamente as atividades enzimáticas celulósica, proteolitica e amiolitica, assim como a produção de epigmentos e ácidos. Avaliaram-se quantitativamente as suas atividades enzimáticas celulase toral sobre o papel de filtro (FPasa) e &beta-endoglucanasa, FPasa e &beta-endoglucanasa; confirmando atividades baixas. Apesar da sua capacidade deteriorante ser discreta, resulta ser ameaçante para a conservação do documento e potencialmente perigoso para a saúde das pessoas que consultam e arquivam.