Evaluación de la respuesta en plantas jóvenes de Ulmus minor al patógeno Ophiostoma novo-ulmi

Along the 20th century the entire population of elms in Europe and North America was devastated by a fungus disease called Dutch elm disease (DED), which is caused by pathogens of the genus Ophiostoma. This disease consists in a quick drying of the trees due to the obstruction of the xylem conductive vessels. One of the most promising strategies for the repopulation of elms, and the consequent recovery of the forest to which this tree belongs is the discovery of disease tolerant species and their propagation. The long juvenile period of the elm hinders a quick determination of the tolerance or susceptibility of the individuals to the disease, since this property can only be analyzed in adult individuals. Therefore, developing tools that reveal these characteristics in less time are very useful for the detection of potentially useful individuals for the repopulation of the tree. Along these lines, finding a correlation between molecular and biochemical properties and the tolerance of a specie may be quite useful to develop a suitable strategy for obtaining DED-resistant trees. This project worked on the testing of several biochemical parameters related to plant defense and oxidative stress in young specimens of Ulmus minor as a way to find out if they can be used as reliable correlation to the tolerance to the DED. Two genotypes, a resistant one called V-AD 2, and a non-resistant one, called VA-AP 38 were used to this purpose. The molecular parameters studied were the production of malondialdehyde because of lipid peroxidation caused by the oxidative stress, as well as several enzimes implied in the detoxification of the reactive oxygen species (ROS), such as superoxide dismutase and ascorbate peroxidase. Also plant defense parameters such as total phenolic content and total flavonoid content were studied in both genotypes. As a result, some evidences were found. Although no correlation between lipid peroxidation and tolerance to DED was proved, the invasion of Ophiostoma novo-ulmi appeared to promote the accumulation of proline, as well as enhanced the activity of an oxidative-strees induced enzyme. Along with several basal biochemical differences found in the polyphenolic content, flavonoid content and proline accumulation, the results of this project showed that, notwithstanding more investigation is required, the use of young specimens of Ulmus minor are suitable in the finding of dutch elm disease tolerant trees.