Grafting is one of the most widely used methods for vegetative propagation, particularly for multiplying trees considered important, but there has been little research done on the effect of hybridization on grafts from the genus Pinus. Sometimes hybrids show the ability to reproduce and adapt efficiently to the environment. However, they reduce the genetic gain of seed orchards. The objective in this research was to evaluate the effect of scion grafts from pure species donor Pinus engelmannii Carr. and from putative hybrid trees P. engelmannii × P. arizonica Engelm., grafted on rootstocks of pure species P. engelmannii, along with the effect of the position of the scion in the donor tree crown (upper third and middle third). The scions were collected from three trees of the pure species and three hybrids. In each tree, 20 scions were collected from each third of the crown evaluated. 120 side-veneer grafts were made at the beginning of spring (March) 2018. Variance analyses were performed to evaluate the treatments and adjustments of the Logit and Weibull models to obtain the probability of graft survival. Significant differences were found between the origins of scions (p < 0.0083, after Bonferroni correction), showing grafts with hybrid tree scions taking hold better. In addition, the probability of survival at 5 months after grafting with hybrid tree scions was greater (p < 0.0001) than in grafts with scions from trees of the pure species (Logit model), which coincides with the results of the Weibull model, which indicated that the probability of graft death with pure species donor tree scions is greater than for grafts with hybrid scions. There were no significant differences regarding the position of the scion in the donor tree crown.

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.

To determine the genetic parameters of growth traits and wood density (estimated by Pilodyn penetration) in a population of Eucalyptus grandis formed by families from 11 seed origins in NE Queensland, Australia and a local land race, 8.5-year-old progenies established in three sites in NE Argentina were evaluated. Local trees exhibited higher growth rate at two sites and better stem form, but also deeper Pilodyn penetration, at all sites; thus, there is potential to infuse new genetic variation into the current breeding population in the region. A significant amount of genetic variation was found for all traits assessed, with growth traits [diameter (DBH), height (HT) and volume (VOL)] showing different genetic structure and degree of genetic control as compared to stem straightness (FORM), bark thickness (BARK) and Pilodyn penetration (PILO). The effect of origin was negligible for growth traits while it was important for the other traits, so it should be considered in the selection strategy; in addition, individual heritability for growth traits (0.11-0.16 in the combined analyses) was generally lower than for the other traits (0.20-0.35). Genetic correlations between sites for all traits were high enough to indicate that genotype-environment interaction would not affect the selection program by using a single breeding population for this region. Genetic correlations between growth traits were high (rg > 0.80), and negligible between these and FORM; the only unfavorable genetic correlation was between PILO and BARK (rg = -0.44). Age-age correlations for growth traits and FORM were very high (rg > 0.90). Results suggest that all traits evaluated could be handled in a breeding program, either independently or combined, without negative correlated effects. Early selection for growth traits and stem form is also possible, with major savings in time.

La determinación de parámetros genéticos en características de valor económico relacionadas con la productividad y calidad de la madera es importante para definir la estrategia más adecuada de mejora genética en especies forestales. En este trabajo se estimó la heredabilidad y las correlaciones genéticas y fenotípicas de características asociadas con la calidad de la madera (densidad de la madera, longitud de traqueidas), el crecimiento (altura total, diámetro normal y volumen del tronco) y la ramificación (número, diámetro y ángulo de ramas, y número de verticilos) en progenies de Pinus patula de ocho años de edad, obtenidas de polinización libre. Se encontró una variabilidad genética amplia en la mayoría de las características, pero el control genético fue de bajo a moderado en ellas (≤ 0.10 h2i ≤ 0.25), excepto para longitud de traqueidas y numero de ramas, en las que no se encontró una variación genética significativa (P > 0.05). La estructura de correlaciones mostró una relación favorable en la mayoría de las características, con correlaciones genéticas que variaron de -0.23 a 0.98 y fenotípicas de 0.02 a 0.93. Los resultados muestran que es posible utilizar algunas características como criterios de selección de manera independiente o combinada para aumentar el crecimiento y calidad de la madera sin ocasionar efectos colaterales negativos en las otras características de importancia económica.

Within the Analytic Hierarchy Process (AHP) framework, a hierarchical model was created considering anthropogenic, genetic and ecological criteria and sub-criteria that directly affect Douglas-fir (Pseudotsuga menziesii (Mirb.)) risk of extinction in central Mexico. The sub-criteria values were standardized, weighted, and ordered by importance in a pairwise comparison matrix; the model was mathematically integrated to quantify the degree of extinction risk for each of the 29 populations present in the study area. The results indicate diverse levels of risk for the populations, ranging from very low to very high. Estanzuela, Presa Jaramillo, Peñas Cargadas and Plan del Baile populations have very low risk, with values less than 0.25. On the other hand, Vicente Guerrero, Morán, Minatitlán, La Garita and Tonalapa populations have very high risk (>0.35) because they are heavily influenced by anthropogenic (close to roads and towns), ecological (presence of exotic species and little or no natural regeneration) and genetic (presence of mature to overmature trees and geographic isolation) factors. In situ conservation activities, prioritizing their implementation in populations at most risk is highly recommended; in addition, germplasm collection for use of assisted gene flow and migration approaches, including artificial reforestation, should be considered in these locations.