Hybridization is an important evolutionary force, because interspecific gene transfer can introduce more new genetic material than is directly generated by mutations. Pinus engelmannii Carr. is one of the nine most common pine species in the pine-oak forest ecoregion in the state of Durango, Mexico. This species is widely harvested for lumber and is also used in reforestation programmes. Interspecific hybrids between P.engelmannii and Pinus arizonica Engelm. have been detected by morphological analysis. The presence of hybrids in P. engelmannii seed stands may affect seed quality and reforestation success. Therefore, the goals of this research were to identify introgressive hybridization between P. engelmannii and other pine species in eight seed stands of this species in Durango, Mexico, and to examine how hybrid proportion is related to mean genetic dissimilarity between trees in these stands, using Amplified Fragment Length Polymorphism (AFLP) markers and morphological traits. Differences in the average current annual increment of putative hybrids and pure trees were also tested for statistical significance. Morphological and genetic analyses of 280 adult trees were carried out. Putative hybrids were found in all the seed stands studied. The hybrids did not differ from the pure trees in vigour or robustness. All stands with putative P. engelmannii hybrids detected by both AFLPs and morphological traits showed the highest average values of the Tanimoto distance, which indicates: i) more heterogeneous genetic material, ii) higher genetic variation and therefore iii) the higher evolutionary potential of these stands, and iv) that the morphological differentiation (hybrid/not hybrid) is strongly associated with the Tanimoto distance per stand. We conclude that natural pairwise hybrids are very common in the studied stands. Both morphological and molecular approaches are necessary to confirm the genetic identity of forest reproductive material.

The establishment of clonal seed orchards is a viable option for the continuous production of improved seed of desired genotypes. Grafting is the main technique used to establish clonal seed orchards. The objective of this study was to examine how the geographic location and the age class of the donor trees of buds, the phenological status of the buds, and the anatomical characteristics of the scions and the rootstocks affect the survival and growth of Pinus engelmannii Carr. grafts. Scions were collected from two trees in each of three age classes (young, middle-aged, and old). Grafting was performed with buds in two physiological states (end of dormancy and beginning of sprouting). Cross-sections of the grafted organs were obtained for anatomical analysis. A Cox proportional hazards model was used to determine the effects of the variables that were considered. The age class of the scion donor trees, the total area of the cut surface of the scion, and the density of resin channels in the scions significantly affected (p < 0.05) survival of the grafts. By contrast, the physiological state of the buds and the other anatomical characteristics of the grafted organs did not significantly affect graft survival. In P. engelmannii, grafting was most effective when scions from middle-aged trees were used. Graft survival was enhanced by a small total area of the cut surface of the scion and low density of resin channels in the scions. The area of the cambium of the scions directly influenced growth of the grafts.

Abstract. Extreme ocean waves in the Caribbean

No abstract

Se evaluó en campo, en dos sitios con características climáticas contrastantes: El Carmen, Durango y Santa Lucía, Pueblo Nuevo, Durango, el efecto de la calidad de planta de Pinus cooperi Blanco producida en vivero en envases de 80 cm3 y 170 cm3 de volumen y regada en la fase de preacondicionamiento cada 48, 96 y 168 horas. Los tratamientos se distribuyeron en un diseño experimental de bloques al azar, con un arreglo en parcelas subdivididas. Durante 18 meses se evaluó supervivencia, crecimiento en diámetro y altura, así como producción de fitomasa. La planta producida en el envase de 170 cm3 resultó superior estadísticamente (p<0,05) en diámetro, con 9,26 mm y en producción total de fitomasa con 19,0 g. Por otro lado, la planta regada cada 96 horas resultó superior estadísticamente (p<0,05) en diámetro, con 9,17 mm y en producción de fitomasa con 17,9 g. El tamaño de envase y la frecuencia de riegos no influyeron estadísticamente (p>0,05) en la supervivencia y crecimiento en altura de las plantas. El factor sitio de plantación sólo tuvo diferencias significativas (p<0,05) en la supervivencia y en el crecimiento en altura de las plantas. La supervivencia fue superior estadísticamente (p<0,05) en el sitio El Carmen, Durango, con 85,6 %, mientras que el crecimiento en altura sobresalió en Santa Lucía, Pueblo Nuevo, Durango con 18,5 cm.