Biocontrol potential of saline- or alkaline-tolerant Trichoderma asperellum mutants against three pathogenic fungi under saline or alkaline stress conditions

ABSTRACT Salinity and alkalinity are major abiotic stresses that limit growth and development of poplar. We investigated biocontrol potential of saline- and alkaline-tolerant mutants of Trichoderma asperellum to mediate the effects of salinity or alkalinity stresses on Populus davidiana × P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using an Agrobacterium tumefaciens mediated transformation system; this process yielded sixty five positive transformants (T1-T65). The salinity tolerant mutant, T59, grew in Potato Dextrose Agar (PDA) containing up to 10% (1709.40 mM) NaCl. Under NaCl-rich conditions, T59 was most effective in inhibiting Alternaria alternata (52.00%). The alkalinity tolerant mutants, T3 and T5, grew in PDA containing up to 0.4% (47.62 mM) NaHCO3. The ability of the T3 and T5 mutants to inhibit Fusarium oxysporum declined as NaHCO3 concentrations increased. NaHCO3 tolerance of the PdPap seedlings improved following treatment with the spores of the WT, T3, and T5 strains. The salinity tolerant mutant (T59) and two alkalinity tolerant mutants (T3 and T5) generated in this study can be applied to decrease the incidence of pathogenic fungi infection under saline or alkaline stress.

Isolation, identification, and biocontrol of antagonistic bacterium against Botrytis cinerea after tomato harvest

ABSTRACT Tomato is one of the most important vegetables in the world. Decay after harvest is a major issue in the development of tomato industry. Currently, the most effective method for controlling decay after harvest is storage of tomato at low temperature combined with usage of chemical bactericide; however, long-term usage of chemical bactericide not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after tomato harvest has great practical significance. In this study, antagonistic bacterium B-6-1 strain was isolated from the surface of tomato and identified as Enterobacter cowanii based on morphological characteristics and physiological and biochemical features combined with sequence analysis of 16SrDNA and ropB gene and construction of dendrogram. Effects of different concentrations of antagonistic bacterium E. cowanii suspension on antifungal activity after tomato harvest were analyzed by mycelium growth rate method. Results revealed that antifungal activity was also enhanced with increasing concentrations of antagonistic bacterium; inhibitory rates of 1 × 105 colony-forming units (cfu)/mL antagonistic bacterial solution on Fusarium verticillioides, Alternaria tenuissima, and Botrytis cinerea were 46.31%, 67.48%, and 75.67%, respectively. By using in vivo inoculation method, it was further confirmed that antagonistic bacterium could effectively inhibit the occurrence of B. cinerae after tomato harvest, biocontrol effect of 1 × 109 cfu/mL zymotic fluid reached up to 95.24%, and antagonistic bacterium E. cowanii has biocontrol potential against B. cinerea after harvest of fruits and vegetables.

In vitro inhibition of spores germination of Alternaria solani by three fungicides

Foram realizados 10 experimentos em condiçöes de laboratório, utilizando-se isolados selvagens locais do fungo Alternaria solani obtidos de folhas de tomateiro. O primeiro experimento consistiu na inoculaçäo de esporos em soluçöes dos fungicidas seguintes, cujas concentraçöes estäo expressas em ingredientes ativos (i.a.): iprodione 0,75 g/l. Outros nove experimentos foram realizados, concomitantemente, mas reduzindo-se as concentraçöes para:½, », 1/32, 1/64, 1/128, 1/256 e 1/512. Essas diluiçöes foram feitas em tubos de hemólise. Em todos os casos, foi incluído um tratamento testemunha, com água deionizada. Os cultivos experimentais foram mantidos em ambiente de 27 por cento. As avaliaçöes consistiram na determinaçäo da porcentagem dos esporos germinados em 5 campos microscópicos (aumento de 100 vezes) realizadas 6 horas e 9 horas após a inoculaçäo dos esporos em cada soluçäo de fungicida, sendo os dados transformados em arc. V sen p/100 para o tratamento estatístico. Na maior concentraçäo, todos os fungicidas inibiram a germinaçäo foram de 3 por cento, 18 por cento e 94 por cento respectivamente para iaprodione, chlorothalonil e água. Nos experimentos com menores concentraçöes dos fungicidas constatou-se significativos aumentos nas porcentagens de germinaçäo de esporos, exceto para anilazine, que manteve inibiçäo até a diluiçäo 1/64 (na avaliaçäo de 9 horas após inoculaçäo)

Utilización de diferentes especies de hongos como biodegradadoras de hidrocarburos: I ensayo preliminar / Utilization of different species of fungi as hydrocarbon biodegradatives: I preliminary assay

La degradación de compuestos orgánicos en la naturaleza es llevado a cabo por los microorganismos "in situ". En los últimos años se ha tratado de usar la capacidad degradativa de los hongos en la descomposición de sustancias producidas por el hombre y que son acumuladas en el medio ambiente como contaminantes. Se utilizó una mezcla de tres especies fúngicas: Alternaria alternata, Cunninghamella elegans y Phanerochaete chrysosporium), las que fueron cultivadas con los desechos de barros durante 30 días en condiciones de laboratorio. Los resultados de los análisis cromatográficos indican que la fracción aromática de la mezcla de hidrocarburos presentes en los barros utilizados ha tenido una importante degradación. Asimismo las relaciones de los isoprenoides a sus respectivos normales (Pristano nC17 y Fitano nC18) son mayores en las muestras tratadas que en la testigo, siendo ésto tambien evidencia de que hubo degradación