Lorena Alejandra Elíades

Entomopathogenic fungi from Argentina for the control of Schistocerca cancellata (Orthoptera: Acrididae) nymphs: fungal pathogenicity and enzyme activity

Abstract The South American locust Schistocerca cancellata (Serville) was the most serious agricultural pest in Argentina during the first half of the last century and remains as a threat when preventive control measures are relaxed in the outbreak area. In this study, we analysed in the laboratory, the effectiveness of 26 fungal strains (isolated from both insects and soil collected in Argentina) for S. cancellata control and determined the relationship between the chitinase, protease and lipase levels in these fungi and their insecticidal activities. We observed that Beauveria bassiana (isolate LPSC 1067) caused the highest mortality (90±1.03%), the highest values of chitinolytic, proteolytic and lipolytic activity were 6.13±0.05, 2.56±0.11 and 2.33±0.47, respectively, and the lowest median lethal time was 5.96 days. This is the first time that a wide variability in chitinase, protease and lipase activity as well as in virulence has been reported in a representative sample of different entomopathogenic fungal strains from Argentina.

α-L-rhamnosidase and β-D-glucosidase activities in fungal strains isolated from alkaline soils and their potential in naringin hydrolysis.

α ‐L‐Rhamnosidases (EC 3.2.1.40) and β ‐D‐glucosidases (EC 3.2.1.21) obtained from several microbial sources are potential catalysts in food, beverage, and pharmaceutical industries. However, the enzyme preparations currently used have limitations related to the stability and activity of the enzyme as well to their reuse. A microtiter screening was carried out in 55 fungal strains isolated from alkaline soils, to obtain active α ‐L‐rhamnosidases and β ‐D‐glucosidases at pH 9.0. While α ‐L‐rhamnosidase activity was detected in 45% of the strains tested, β ‐D‐glucosidase activity was found only in 27%. Based on the fungal ability to produce α ‐L‐rhamnosidase activity, cultures were supplemented with naringin to study the activities of the enzymes and the potential of the fungal strains on naringin hydrolysis. About 70% of the fungal strains tested increased the activities of both enzymes in the naringin‐supplemented cultures as compared to non‐supplemented ones. This effect was higher in Acrostalagmus luteo‐albus LPSC 427 (15.3 fold) for α ‐L‐rhamnosidase activity and Metarrhizium anisopliae LPSC 996 (51.1 fold) for β ‐D‐glucosidase activity. All the enzyme preparations tested hydrolyzed naringin at pH 9.0, being that obtained from Acremonium murorun LPSC 927 cultures the one which showed highest hydrolysis. Here, different fungal species are reported for the first time for their ability to produce α ‐L‐rhamnosidase and β ‐D‐glucosidase activity at alkaline pH. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fungal monitoring of the indoor air of the Museo de La Plata Herbarium, Argentina

BACKGROUND Biological agents, such as fungal spores in the air in places where scientific collections are stored, can attack and deteriorate them. AIMS The aim of this study was to gather information on the indoor air quality of the Herbarium of Vascular Plants of the Museo de Ciencias Naturales de La Plata, Argentina, in relation to fungal propagules and inert particles. METHODS This study was made using a volumetric system and two complementary sampling methods: (1) a non-viable method for direct evaluation, and (2) a viable method by culture for viable fungal propagules. RESULTS The non-viable method led to ten spore morphotypes being found from related fungal sources. A total of 4401.88spores/m3 and 32135.18 inert suspended particles/m3 were recorded. The viable method led to the finding of nine fungal taxa as viable spores that mostly belonged to anamorphic forms of Ascomycota, although the pigmented yeast Rhodotorula F.C. Harrison (Basidiomycota) was also found. A total count of 40,500fungal CFU/m3 air was estimated for all the sites sampled. CONCLUSIONS Both the non-viable and viable sampling methods were necessary to monitor the bio-aerosol load in the La Plata Herbarium. The indoor air of this institution seems to be reasonably adequate for the conservation of vascular plants due to the low indoor/outdoor index, low concentrations of air spores, and/or lack of indicators of moisture problems.