Rute Terezinha da Silva Ribeiro

Characterization of Nomuraea rileyi strains using polymorphic DNA, virulence and enzyme activity

The characterization of entomopathogenic microorganisms is important for the selection of more effective strains for use in integrated pest-control programs. Five Nomuraea rileyi strains (SA86101, GU87401, SR86151, CG128 and VA9101) were characterized using random amplified polymorphic DNA (RAPD) analysis, virulence studies and assessment of chitinolytic and proteolytic activity. RAPD analysis divided the strains into two groups with a similarity coefficient of 0,76%, group 1 consisting of strains SA86101, GU87401 and SR86151 and group 2 of strains CG128 and VA9101. The LT50 varied from 165h with strain VA9101 to 246h with strain GU87401. Chitinolytic and proteolytic activity of the fungi after 144h growth in minimal medium were tested using colloidal chitin as substrate. All strains exhibited enzyme activity, with strain VA9101 having the highest chitinase activity (0,0040 mmol/mL/min the 40oC) and strain SA86101 the highest proteolytic activity. No relationship was found between RAPD analysis, virulence and chitinase or protease activity.

In vitro antifungal activity of four chemotypes of Lippia alba (Verbenaceae) essential oils against Alternaria solani (Pleosporeaceae) isolates

Several volatile natural compounds produced by plant secondary metabolism have been proven to present antimicrobial action, enabling their use in phytopathogen control. They also present low environmental impact when compared to conventional pesticides. Essential oils contain these compounds and can be found in several plant species, such as Lippia alba (Mill.) N.E. Brown (Verbenaceae). Essential oils of four chemotypes of L. alba, characterized by their major compounds, namely camphor, citral, linalool and camphor/1,8-cineole, were tested against the phytopathogen Alternaria solani Sorauer (Pleosporaceae), which causes early blight on tomatoes and is responsible for great economic losses regarding production. Essential oils antifungal action was tested in vitro using potato dextrose agar medium with essential oil concentrations at 0.1, 0.5, 1.0, 1.5 and 2.0 µL mL-1. The chemotype that had the best performance was citral, showing significant inhibition compared to the others, starting at the 0.5 µL mL-1 concentration. The essential oil belonging to the linalool chemotype was efficient starting at the 1.5 µL mL-1 concentration. Conversely, the camphor chemotype did not show any action against the phytopathogen. Moreover, the essential oils had no remarkable effect on tomato germination and growth. In conclusion, these essential oils presented fungicidal action against A. solani.

Desenvolvimento de Pantoea agglomerans em diversas temperaturas, pH e concentrações de carboxi-metil-celulose e o seu impacto no controle de Rosellinia necatrix

ABSTRACT Rosellinia necatrix Prill induces the white root rot of apple, adisease that causes severe losses in orchards located in Southern Brazil.The management of the disease is mostly preventative and includeusage of less susceptible rootstocks and soil fumigation. Protectionof nursery apple trees before planting with an antagonistic bacterium Pantoea agglomerans was recently proposed to reduce the diseaseincidence. The aims of this research were to know about thepathogen-antagonic bacterium relationships and the effect of cellconcentrations, pH, temperature and carboximethylcellulose(CMC) in the culture media on the growth of thepathogen, the antagonic organism and on the disease control. Camatti - Sartori V., Valdebenito - Sanhueza, R. M., Silva Ribeiro, R. T. Development of Pantoea agglomerans under different temperatures, pH andcarboximethyl cellulose rates and their effect on Rosellinia necatrix control. Summa Phytopathologica, v.34, n.1, p.13-17, 2008 RESUMO Rosellinia necatrix