A total of 1640 increment cores from 343 radiata pine ( Pinus radiata D. Don) families were sampled at two second-generation progeny trials, aged 6 and 7 years, for a detailed genetic study of juvenile wood quality traits. Density, microfibril angle (MFA), and modulus of elasticity (MOE) were determined from pith to bark using SilviScan® technology. Heritability was greatest for area-weighted density at the two sites (0.63 and 0.77, respectively), and the lowest for growth traits (<0.23). Genotype by environment interaction was low for all three wood quality traits. A positive genetic correlation between density and MOE (0.43), and a highly negative, and therefore, favourable genetic correlation between MFA and MOE (–0.92) were observed, implying that improvement of multiple juvenile wood properties is possible. The genetic correlations between whole-core wood quality traits and individual-ring measurements suggest that improvement for juvenile wood properties across the entire profile of the corewood including the innermost rings can be achieved. However, density, MFA, and MOE had unfavourable genetic correlations with diameter growth suggesting that selection for increased density and MOE, and reduced MFA in the absence of selection for growth will result in a genetic loss for growth rate.
Economic breeding objectives were developed for production of radiata pine (Pinus radiata D. Don) structural timber in Australia. Production systems of eight companies, including plantation growers, sawmills, and integrated-system companies, were examined. A bioeconomic model linking the breeding-objective traits mean annual increment (MAI), stem sweep, average branch size, and modulus of elasticity (MoE) with production-system components was constructed using data obtained from industry and published sources. For a plantation grower the most important trait for improvement was MAI (31% improvement of net present value after a 10% trait improvement). For a sawmill the most important trait was MoE (29% improvement of profit after a 10% trait improvement). For an integrated-system company the two most important traits were MoE and MAI (24% and 21% improvement of net present value after a 10% trait improvement, respectively). There was a high correlation between breeding objectives of plantation growers within a region (rG > 0.99), but a negative correlation between breeding objectives of plantation growers and sawmills (rGS = –0.32) and only an intermediate correlation (rGI < 0.65) between those of growers and integrated-system companies.
-A total of 360 bark-to-bark-through-pith wood strips were sampled at breast height from 180 trees in 30 open-pollinated families from two rotation-aged genetic trials to study inheritance, age-age genetic correlation, and early selection efficiency for wood quality traits in radiata pine. Wood strips were evaluated by SilviScan and annual pattern and genetic parameters for growth, wood density, microfibril angle (MFA), and stiffness (modulus of elasticity: MOE) for early to rotation ages were estimated. Annual ring growth was the largest between ages 2-5 years from pith, and decreased linearly to ages 9-10. Annual growth was similar and consistent at later ages. Wood density was the lowest near the pith, increased steadily to age 11-15 years, then was relatively stable after these ages. MFA was highest (35• ) near the pith and reduced to about 10• at age 10-15 years. MFA was almost unchanged at later ages. MOE increased from about 2.5 GPa near the pith to about 20 GPa at ages 11-15 years. MOE was relatively unchanged at later ages. Wood density and MOE were inversely related to MFA. Heritability increased from zero near the pith and stabilised at ages 4 or 5 for all four growth and wood quality traits (DBH, density, MFA and MOE). Across age classes, heritability was the highest for area-weighted density and MFA, lowest for DBH, and intermediate for MOE. Age-age genetic correlations were high for the four traits studied. The genetic correlation reached 0.8 after age 7 for most traits. Early selection for density, MFA and MOE were very effective. Selection at age 7-8 has similar effectiveness as selection conducted at rotation age for MFA and MOE and at least 80% effective for wood density.early selection / microfibril angle / modulus of elasticity / wood density / radiata pine Résumé -Efficacité d'une sélection précoce pour les propriétés du bois adulte chez le pin radiata. Cette étude a pour objectif d'estimer les paramètres génétiques (héritabilités et corrélations juvéniles-adultes) pour différentes propriétés du bois chez le pin radiata et d'évaluer l'efficacité d'une sélection précoce. Trois cent soixante échantillons diamétraux de bois ont été prélevés dans deux dispositifs génétiques adultes sur trente familles de pin radiata issues de pollinisation libre, puis analysés avec le SilviScan . Les caractéristiques annuelles de la croissance, de la densité du bois, de l'angle des microfibrilles (MFA) et de la rigidité (module d'élasticité : MOE) ont été analysées et les paramètres génétiques de ces caractères ont été estimés du stade juvénile à l'âge de la révolution. La croissance radiale est la plus forte entre 2 et 5 ans (depuis la moelle) puis décroît linéairement jusqu'à neuf-dix ans et se stabilise ensuite. La densité du bois est la plus faible près de la moelle ; elle augmente fortement jusqu'à 11-15 ans puis se stabilise. MFA est le plus élevé (35 • ) près de la moelle ; il diminue ensuite pour atteindre environ 10• vers 10-15 ans. MFA ne varie pratiquement plus au-delà de cet âge. MOE passe d...
We studied the genetic structure of Mycosphaerella cryptica following natural infection of Eucalyptus globulus in a genetic trial. Results from this study indicated significant genetic variation within, and between, E. globulus families (three cloned and control-crossed F 2 and four open-pollinated families). Single-ascospore isolates were sampled from 72 E. globulus trees with contrasting levels of resistance within the trial, 21 E. nitens trees in an adjacent plantation, and five distant Eucalyptus plantation trees (two E. globulus 100-2400 km; two E. nitens 50-2200 km; one E. grandis × E. tereticornis hybrid 1500 km from the trial). Deoxyribonucleic acid from these isolates was scored for the presence/absence of 75 random amplified polymorphic DNA (RAPD) loci. Only 18 RAPD genotypes, which appeared to recombine rarely, were present among the 98 isolates, which indicates that M. cryptica is not strictly heterothallic. Cluster analysis using genetic distance revealed that M. cryptica genotypes from the field trial grouped into two clusters that matched differences in isolate culture morphology, indicating that the fungal population comprised two distinctive biotypes. The two biotypes differed markedly in their host interactions. Biotype 2 was found only on E. globulus, whereas biotype 1 infected both E. globulus and E. nitens eucalypt species. Within E. globulus, biotype 2 was almost exclusively collected on resistant trees whereas biotype 1 was found on both resistant and susceptible trees. The hypothesis that there could be specialisation of M. cryptica biotypes occurring at two levels, among host species and within host species, is discussed.
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