Plants encounter a broad range of natural enemies and defend themselves in diverse ways. The cost of defense can be reduced if a plant secondary metabolite confers resistance to multiple herbivores. However, there are few examples of positively correlated defenses in plants against herbivores of different types. We present evidence that a genetically variable chemical trait that acts as a strong antifeedant to mammalian herbivores of Eucalyptus also deters insect herbivores, suggesting a possible mechanism for cross-resistance. We provide field confirmation that sideroxylonal, an important antifeedant for mammalian herbivores, also determines patterns of damage by Christmas beetles, a specialist insect herbivore of Eucalyptus. In a genetic progeny trial of Eucalyptus tricarpa, we found significant heritabilities of sideroxylonal concentration (0.60), overall insect damage (0.34), and growth traits (0.30-0.53). Population of origin also had a strong effect on each trait. Negative phenotypic correlations were observed between sideroxylonal and damage, and between damage and growth. No relationship was observed between sideroxylonal concentration and any growth trait. Our results suggest that potential for evolution by natural selection of sideroxylonal concentrations is not strongly constrained by growth costs and that both growth and defense traits can be successfully incorporated into breeding programs for plantation trees.

A young provenance/progeny trial of spotted gums, which are major hardwood plantation species in subtropical eastern Australia, was studied for growth, form, and damage from Quambalaria shoot blight. The trial contained a wide range of genotypes, mainly of Corymbia citriodora subsp. variegata, with between one and 21 families per provenance. Genetic parameters were calculated from 23 provenances with four or more families. Provenances superior for growth included four well-represented C. citriodora subsp. variegata provenances, all from south-east Queensland, which also had a high proportion of superior families. Overall, Queensland provenances had significantly higher mean diameter and height than those from New South Wales (NSW), although there were several superior NSW families. Provenances superior for growth also displayed good straightness and relatively fine branching. Relatively low Quambalaria shoot blight damage was recorded for four Queensland provenances and one coastal NSW provenance, which all had high proportions of families with low damage. Provenances that were putative intergrades between C. citriodora subsp. variegata and C. maculata tended to have high damage levels. However, some mediocre provenances contained superior families potentially useful for breeding. Regressions of Quambalaria damage index (QDI) on latitude, and mean height growth on QDI, were highly significant and moderately strong (0.51 and 0.58, respectively), indicating increasing damage in more southern material, and a retarding effect (although not striking) of damage on growth. Individual heritability estimates were low (zero to 0.14) for growth and form, and moderate for QDI (0.31). The genetic correlations for QDI with growth traits were strong and negative (-0.77 and -0.88), supporting a strategy of selecting vigorous trees for breeding programs from provenances and families superior for these traits.

No abstract

A new breeding strategy is presented for the Radiata Pine Breeding Company, a New Zealand based research consortium, that drives the breeding program for Pinus radiata for both the New Zealand and New South Wales based Australian forest plantation industry. The new strategy builds on the existing base for P. radiata, and on the last strategy review in 2000. The new strategy comprises a large open-pollinated (OP) Main Population (MP) with 500 female parents and two sublines (250 female parents per subline). The MP will be tested using alpha designs, single-tree plots and incomplete blocks to maximise efficiency. Each subline will be tested on four sites, geographically distant from the other subline. The MP will be managed in discrete generations. Selection of the next generation will be using a combination of backward and forward selection, but the strict control of inbreeding with identified lineage will rely on the development of parental reconstruction for OP progeny. There are alternatives to this, however, such as estimating the group coancestry and accepting some additional increase in inbreeding. This is a new and significant departure from previous breeding strategies for P. radiata in New Zealand. There will also be a single, small Elite Population (EP), tested 50% as progeny and 50% as clones. Twenty four parents will be tested each year as clones and 24 as seedling progeny with some overlap between the two. It is expected that the clonal population will capture the greatest gains in traits with low heritabilities, and the half-sib progeny will capture the greatest gains in traits with high heritabilities. The two sublines will be maintained in the EP, and breeding will be managed as a rolling front with trials established every year, while trials of the MP will be established every 10 years.

This association study of Eucalyptus pilularis populations provides empirical evidence for the role of Pectin Methylesterase (PME) in influencing solid wood characteristics of Eucalyptus. PME6 was primarily associated with the shrinkage and collapse of drying timber, which are phenotypic traits consistent with the role of pectin as a hydrophilic polysaccharide. PME7 was primarily associated with cellulose and pulp yield traits and had an inverse correlation with lignin content. Selection of specific alleles in these genes may be important for improving trees as sources of high-quality wood products. A heterozygote advantage was postulated for the PME7 loci and, in combination with haplotype blocks, may explain the absence of a homozygous class at all single-nucleotide polymorphisms investigated in this gene.

Growth to 38 months and severity of Mycosphaerella leaf disease and target spot (caused by Aulographina eucalypti (Cooke & Mass.) von Arx & Muller) were assessed in a Eucalyptus pilularis Smith (blackbutt) family trial in New South Wales (NSW), Australia. Significant variation in growth, disease, and defoliation was found among the 40 provenances and 321 families tested; however, relatively few provenances had concentrations of superior or poor families. Most families in three higher altitude NSW provenances were superior for volume increment, while three southeast Queensland provenances had low mean volume increment. Mycosphaerella damage and defoliation tended to be low in several higher altitude northern NSW provenances, but the southeast Queensland provenances had significantly higher mean defoliation. Individual narrow sense heritability estimates were low to moderate for Mycosphaerella damage (0.38) and defoliation (0.22) and low for Aulographina damage (0.13) and volume increment (0.13). Significant genetic and phenotypic correlations between Mycosphaerella damage and defoliation were low and positive. Low to moderate negative correlations occurred between Mycosphaerella damage and volume increment and between defoliation and volume increment, suggesting that Mycosphaerella leaf disease, in particular, and defoliation had deleterious effects on tree growth. However, the impact of these foliar pathogens on the volume of E. pilularis is often low, so selecting for growth and form alone in the early stages of domestication could provide acceptable gains in yield. Résumé :Les auteurs ont évalué la croissance jusqu'à 38 mois ainsi que la sévérité des maladies de feuilles causées par Mycosphaerella et Aulographina eucalpti (Cooke & Mass.) von Arx & Muller dans un test de descendances d'Eucalyptus pilularis Smith établi en Nouvelle-Galles du Sud (NGS), en Australie. Des différences significatives quant à la croissance, aux maladies et à la défoliation ont été observées parmi les 40 provenances et 321 descendances testées. Cependant, il y avait relativement peu de provenances avec des concentrations de descendances supérieures ou inférieu-res. La plupart des descendances des trois provenances les plus en altitude de la NGS affichaient un accroissement en volume supérieur, tandis que trois provenances du sud-est du Queensland affichaient un faible accroissement moyen en volume. Les dommages et la défoliation dus à Mycosphaerella étaient généralement faibles chez plusieurs provenances plus en altitude du nord de la NGS, mais les provenances du sud-est du Queensland affichaient une défoliation moyenne significativement plus élevée. Les estimations de l'héritabilité au sens strict variaient de faibles à modérées pour les dommages (0,38) et la défoliation (0,22) dus à Mycosphaerella tandis qu'elles étaient faibles pour les dommages dus à Aulographina (0,13) et pour l'accroissement en volume (0,13). Les corrélations génétiques et phénotypiques significatives entre les dommages dus à Mycosphaerella et la défoliation étai...

SummaryGrowth stress in 9-y-old plantation-grown Eucalyptus dunnii was assessed by measuring longitudinal growth strain. Strain varied considerably (370-1560 µm -1 ) and was sufficiently heritable (h 2 = 0.3-0.5) that tree breeding may be an effective way to reduce the incidence of growth stress in this species. Although the formation of longitudinal growth strain appears to be under strong genetic control (P = 0.0015), there was a tendency for tall thin trees to exhibit higher stress than short thick trees (P = 0.025 for height:diameter ratio). Two provenances and three families identified in this study show potential as superior material for further tree breeding.

No abstract