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  • Author: L.J. Vargas x
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Genetic Variation in Needle Epicuticular Wax Characteristics in Pinus Pinceana Seedlings

Abstract

Seedlings from each of 12 Pinus pinceana populations from throughout the species’ range in Mexico were evaluated in a common-garden test to (1) determine the level of genetic variation and genetic structure of epicuticular needle wax quantity, (2) examine differences in wax chemical composition, and (3) seek evidence for an adaptive response in wax composition and quantity across environmental and geographic gradients. Regions and populations within regions showed high variation (38.2% and 10.5%, respectively, of the total variation) in wax quantity. Epicuticular wax recovered from primary needles of P. pinceana comprised eight classes. Secondary alcohols (71.7%) were the major homologs identified by gas chromatography. Seedlings from the northern region were separated based on wax composition from seedlings from the central and southern regions by canonical discriminant analysis. A strong differentiation among regions (QSTR=0.571) and populations within regions (QSTP(R)=0.384) was observed for wax quantity. Data on wax quantity and chemical composition indicate that physicochemical characteristics of epicuticular wax may show adaptation of P. pinceana to local environments.

Open access
Genetic Parameters of Growth Traits and Wood Density in Eucalyptus grandis Progenies Planted in Argentina

Abstract

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.

Open access
Altitudinal genetic variation among native Pinus patula provenances: performance in two locations, seed zone delineation and adaptation to climate change

Abstract

To select the genetic source of Pinus patula Shiede and Deppe seed best adapted to different native zones for reforestation, seedlings of 12 provenances native to a selected altitudinal gradient in Oaxaca, southern Mexico, were planted on two sites at contrasting altitudes (high 3000 m above sea level (masl) and low, 2500 masl) within the species natural distribution, and tested for growth in height at age 18, 24 and 36 months. Differences among provenances and between sites showed significance (p<0.05). Seedling growth showed a climatic and altitudinal pattern, in which seedlings from populations originating in low-middle altitudes had higher growth than populations originating in high altitudes, and from the extreme low altitude limit. Results were used to delineate climatic and altitudinal seed zones for contemporary and future climate zones in the decade centered in year 2030, using the average results of six climate-emissions scenarios. The results indicate that splitting the region into four seed zones is appropriate under contemporary climate scenarios with the following altitude limits: Zone 1, from 2300 to 2500 masl; Zone 2, 2500 to 2700 masl; Zone 3, 2700 to 2900 masl and Zone 4 from 2900 to 3100 masl. The equivalence on climatic intervals was also defined for mean annual temperature, precipitation and an annual aridity index (AAI). Values of contemporary AAI occurring at a given altitude by year 2030 were determined, with results suggesting that populations should be shifted 200 to 250 m attitudinally upward, through a program of assisted migration, to realign them to the future climate for which they are adapted.

Open access
Musculoskeletal Outcomes from Chronic High-Speed High-Impact Resistive Exercise

Abstract

Subjects (n=13) did 30 workouts with their left leg on an Inertial Exercise Trainer (IET), while their right leg served as an untreated control. Before and after the 30 workouts, they underwent isokinetic strength tests (knee and ankle extensors of both legs) whose peak torque (PT), time to PT (TTPT), and rate of torque development (RTD) values were each analyzed with 2(leg)×2(time)×3(velocity) analysis of variances (ANOVAs), with repeated measures per independent variable. Peak force (PF) and total work (TW) data were measured from each IET workout, and they represent time course strength changes produced by our exercise intervention. PF and TW values for the three IET exercises that comprised each workout were each analyzed with one-way ANOVAs with time as the independent variable. Results included significant ankle and knee extensor PT increases, whereby the left leg achieved higher values at posttesting, but there were no significant TTPT changes and a time effect for ankle extensor RTD. Our data show that PF and TW each had significant increases over time, with the latter exhibiting greater gains over the 30-workout intervention. Our results imply that the IET yields strength gains over time comparable to standard resistive exercise hardware.

Open access