Partial purification of elicitors from saccharomyces cerevisiae: role as resistance inducers in cucumber (Cucumis sativus) against colletotrichum lagenarium and as inducers of glyceollin synthesis in soybean (Glycine max).

Author(s)

Elaine Regina Godoy Labanca

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2002-07-04

Examining board members

Sergio Florentino Pascholati; Marcia Regina Braga; Marcio Rodrigues Lambais

• Advisor: Sergio Florentino Pascholati

Abstract

The acquired resistance of plants to pathogens is an alternative method to control diseases which includes the activation of resistance mechanisms in the plants. A few products already commercially available have their action based upon this mechanism. In the search for novel molecules that can be used under field conditions, many compounds from microbes with the ability to stimulate one or more defense responses were already isolated and characterized. Saccharomyces cerevisiae is an yeast with the ability to induce defense responses and resistance in some plants. A suspension of cells from the yeast was autoclaved with the purpose of extracting one or more compounds with the ability to induce the accumulation of phytoalexins in soybean cotyledons and to protect soybean plants against Microsphaera diffusa (causal agent of powdery mildew) and plants of cucumber against Colletotrichum lagenarium (causal agent of anthracnose). The compounds extracted by this method were separated using ethanolic precipitation. After this step, the fractions of higher elicitation activity were separated from those of lower one by using ion exchange cromatography and affinity cromatography. The non-adsorbed fraction to DEAE-Cellulose was the one that induced the highest accumulation of phytoalexins. However, none of the fractions were able to protect soybean plants from M. diffusa. In the case of cucumber, seedlings treated with the fractions from affinity chromatography were able to reduce disease symptoms caused by C. lagenarium by 50 to 70 % and to increase the activity of peroxidases. Extracts that were incorporated into growing media did exhibit any inhibitory effect on in vitro growth and sporulation of C. lagenarium. According to these results, it is possible to conclude that there are compounds in the cell walls of the yeast that are able to induce local resistance to C. lagenarium in cucumber and that at least one of these compounds is a carbohydrate that likely contains mannan and glucosamine. (AU)