MJ BABIANO, R MANSO, T VALLE and P CORCHETE

Dpto Fisiologia Vegetal, Facultades de Biologia y Farmacia, Universidad de Salarnanca, Spain

Background and objectives
Ophiostoma ulmi is the causal agent of Dutch elm disease (DED), one of the most devastating tree diseases in the world. Since the first detailed description of the disease in Holland in 1920/21, great efforts to understand and combat this disease have been made. In order to obtain DED control, knowledge of defense mechanisms against the disease is essential.

When cell suspension cultures derived from leaf-callus of Ulmus pumila (an elm species resistant to DED) or U. campestris (a high susceptible elm) were inoculated with O. ulmi spores, mycelial growth was visible 24 h after inoculation in U. campestris . By contrast no fungal growth was observed in Ulmus pumila cultures after 4 days of inoculation. This differential growth on "in vitro" cultured elms reflect a degree of resistance of the Ulmus pumila tissue from which the cultures were derived [1]. These cultures are being used as a model system to study the differential biochemical mechanisms of disease resistance in elms. In this work we have studied the protein pattern in both resistant and susceptible elm cell cultures and the alterations brought about by the infection with spores of 0. ulmi .

Results and conclusions
Qualitative analysis of proteins by SDS-PAGE extracted from the protoplastic fraction of cultured cells of Ulmus pumila and U. campestris indicated major qualitative differences between both species: in the resistant culture the presence of a 28 kD protein was detected while it was absent from the susceptible species. When cell suspensions were infected with fungal spores an alteration of the protein pattern was observed mainly 6 h after inoculation: the 28 kD protein was strongly induced in U. campestris cells. The putative involvement of this protein in DED is currently under investigation.

References
1. Corchete MP, Diez JJ, Vafie T, 1993. Plant Cell Reports 13, 111-14.