Micropropagación de Quercus suber L. y resistencia/tolerancia in vitro al patógeno Phytophthora cinnamomi Rands. fases iniciales de la micropropagación de Q. ilex L.

Resumen

The dramatic fall in Quercinea forests occurred in the Mediterranean area from the last third of the twentieth century, has generated great preoccupation about the “dehesa” and Quercus forest conservation, because its importance in that area. Numerous studies have allowed relate the factors involved in the aforementioned fall, so the hypothesis remaining today is that the combined action of these factors, leads to the progressive and widespread deterioration of the tree up to cause its death. That is why this disease was known as oaks "decline", considering the pathogen Phytophthora cinnamomi as the main contributor to this disease. One of the resources to respond to this problem, are the studies of resistance/tolerance for selection and propagation of elite trees, within which is framed the present work, specifically focusing on the selection and propagation of holm oak (Q. ilex L. , ssp. ballota) and cork oak (Q. suber L. ). The propagation has been carried out by in vitro culture, since this method of regeneration allows saving the disadvantages caused by geographical and weather conditions, as well as time of production, in very controlled environmental conditions. The first chapter deals with micropropagation of adult and juvenile material were made, both of holm and cork oaks. In the initial phase of the material, a different behavior of both species was observed with respect to the cuttings pre-cold treatment in adult material, not being recommended for holm oak but just for cork oak. In the establishment phase, the culture media based on GB5 salts showed the best results in holm oak respect to GD or MS media, while GD rinsed better results than MS in cork oak. In the proliferation phase, only performed for cork oak, explants showed better aspect and multiplication rates in MS in opposition to GD. The best hormones combination was 0,3mg/L BAP + 2mg/L AIB, being novelty the better aspect and development of the explants remaining the auxins in greater proportions than cytokines. Rooting was performed only for cork oak too. Percentages of up to 80% of available rooted shoots were achieved with the treatment of 4mg/L of AIB for 15 days. Neither the darkness pre-treatment, nor free-hormone media treatments, improved the overall percentages of rooting, although some clones as the HEE6 reached 100% of available rooted shoots with darkness treatment during the first 7 days of rhizogenesis. Tips necrosis problems were cause by concentrations of AIB higher than 4mg/L, being this cause very dependent on the genotype and origin of the material. However, treatment in free-hormone media prior induction of rhizogenesis in auxins media, reduced the overall percentages of the tip necrosis. In the second chapter, the in vitro inoculation with P. cinnamomi of in vitro rooted explants of cork oak was made, as well as the evaluation of parameters representing the symptoms caused by infection in those plantlets. Dose of inoculum, time of inoculation for the appropriate tests and the better parameters reflecting the health state of the plants after infection in both the aerial and the radical part of plantlets were established. After that, 5 clones of cork oak were compared by its different behavior after infection with P. cinnamomi. Parameters as the "time to reach the total necrosis", "time to appear the first symptoms of necrosis", "speed to reach the total necrosis from the emergence of the first symptoms" and the "visual rating of stem" of the aerial part, and parameters as the "percentage of necrotic root length compared to the total length", "the rate of growth in length of the roots" and the "rate of growth in the number of roots" of the root zone, showed differences between genotypes of the in vitro rooted and inoculated plantlets.