Red band needle blight caused by Dothistroma septosporum and D. pini, and brown spot needle blight caused by Lecanosticta acicola provoke severe and premature defoliation in Pinus, and subsequent reduction of photosynthetic surfaces, vitality, and growth in young and adult trees. The recurrent damage results in branch and tree death. Until recently, pine needle blight diseases have had only minor impacts on native and exotic forest trees in the North of Spain, but in the past five years, these pathogen species have spread widely and caused severe defoliation and mortality in exotic and native plantations of Pinus in locations where they were not detected before. In an attempt to understand the main causes of this outbreak and to define the effectiveness of owners' management strategies, four research actions were implemented: a survey of the management activities implemented by the owners to reduce disease impact, the evaluation of specific symptoms and damage associated with infection, and the identification of the causative pathogenic species and their reproductive capacity. Morphological characteristics of the fungus and molecular identification were consistent with those of Lecanosticta acicola and Dothistroma spp., D. septosporum, D. Pini, and both mating types were present for the three identified pathogens. The local silvicultural management performed, mainly pruning and thinning, was not resulting in the expected improvement. The results of this study can be applied to establish guidelines for monitoring and controlling the spread of needle blight pathogens.
The shoot-forming capacity of Pinusradiata D. Don juvenile explants under tissue culture conditions was examined. Three types of explant were used: whole embryos; cotyledons excised from whole embryos which had been cultured for 1 week on the shoot initiation medium; and cotyledons excised from 1-week-old aseptically germinated seeds. The average number of rootable shoots produced per seed in 12–13 weeks was 9 for excised embryos, 18 for their separated cotyledons, and 180 for the cotyledons from germinated seeds. Induction of a smooth-surfaced, yellow–green, nodular meristematic tissue appears to be a requirement for the formation of large numbers of adventitious shoots. By extending the culture period from 12 to 24 weeks more than 1300 shoots were formed from the cotyledons of one germinated seed. To date, no other conifer tissue culture method has been reported to give such a large number of adventitious shoots of the same clone in a first generation.
Horgan (nee Reiliy), K. and Aitten, J. 1981. Reliable plantlet formation from embryos and seedling shoot tips of radiata pine. -Physiol. Plant. 53: 170-t75.A method has been devised for the reliable production of plantlets from embryos and seedling shoot tips otPinus radiata D.Don (radiata pine). Buds were induced on an agar or liquid Schenk and Hildebrandt (SH) medium containing 5.0 mg/1 benzylammopurme (BAF). Except tor some abnormal buds, the buds grew into elongated shoots on an agar SH medium without cytokinin. The transfer of shoots from a SH medium to a Gresshoff and Doy (GD) medium was found to be an important pretreatment which increased the survival of the shoots when they were placed in a peat and pumice mix for root formation. Elongated shoots were induced to form roots under non-sterile conditions in a humid environment with dccasionai misting. An intervening 5-day treatment of shoots in an agar medium containing 2.0 mg/1 indolebutyric acid (IBA) and 0.5 mg/1 napthaleneacetic acid (NAA) significantly increased the percentage of shoots forming roots and the number of roots formed per shoot over control shoots placed directly in the peat:pumice mis. An enhanced level of COT during root formation had no effect on the time of root formation or on the percentage of shoots forming roots. These results concerning the elongation, growth and rooting of adventitious shoots are now being applied to the development of very large numbers of plantlets starting from cotyledons from partially germinated seeds.
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