Heidi S. Dungey

The effectiveness of cloning for the genetic improvement of Mexican white cypress Cupressus lusitanica (Mill.)

Two trials on Mexican cypress Cupressus lusitanica Miller in the North Island of New Zealand were assessed for diameter at breast height and at one site, subjective scores for branch size and stem canker (caused by Seiridium spp.) at age 6 from planting. The trials comprised 15 open-pollinated families, represented by both cloned and seedling progeny. Linear mixed model methodology, using a spatial model for the residuals, was applied to estimate genetic parameters. Estimated narrow-sense heritabilities were moderate to high for diameter at breast height (range from 0.46 to 0.62), stem canker (≈0.30) and branch size (range from 0.23 to 0.45) and did not appear to differ significantly between propagule types for all traits. Clonally replicated progeny led to an increase in accuracy of selection for additive genetic merit when compared with seedling testing, with the improvement being greater for traits with lower narrow-sense heritabilities. Estimated additive genetic correlations between cloned and seedling progeny were moderate to high (≥0.65) for diameter and branch size, indicating that selection decisions would not be substantially changed using either propagule type for progeny testing. All estimates of non-additive genetic variation based on the cloned progeny were non-significant. The use of spatial analysis was effective for diameter and branch size, but not for stem canker. No significant genotype by environment interaction was detected for diameter. Implications of the results for breeding and deployment of C. lusitanica are discussed.

First evidence of genetic-based tolerance to red needle cast caused by Phytophthora pluvialis in radiata pine

BackgroundRed needle cast (RNC) is a new needle disease of Pinus radiata D. Don (radiata pine) in New Zealand that is causing significant, but as-yet un-quantified, loss of growth and productivity. This foliar disease has recently been attributed to the infection of the needles by Phytophthora pluvialis Reeser, Sutton & E Hansen. Genetic improvement is seen as a possible solution to mitigate the effects of this needle disease on forest productivity.FindingsTo quantify the ability of genetics to provide a solution, RNC was assessed on a single clones-within-families genetics trial using two methods: the percentage needle cast that was attributable to red needle cast symptoms; and the percentage needle cast where the causal agent was not clearly identifiable. Both needle cast assessment methods were found to be heritable (ĥ2 0.21-0.31).ConclusionsSelecting for tolerance to RNC is likely to deliver healthier trees. More assessments across a number of sites and seasons are required to confirm this result.

Heartwood of Cupressus lusitanica , C. macrocarpa , Leyland and Ovens cypress and prediction of its durability using near-infrared spectroscopy

The heartwood of plantation-grown Cupressus lusitanica, C. macrocarpa, Leyland and Ovens cypress (×Cuprocyparis leylandii and ×C. ovensii) from trials in New Zealand, was evaluated using breast height increment cores and in vitro decay tests with fungal cultures to determine the variation in the heartwood content and natural durability, and its prediction using near-infrared (NIR) spectroscopy. The increment core measurements showed the length of the cores was strongly influenced by the stocking and site, but the heartwood content and weight loss with decay testing were strongly influenced by species and genotype. The heartwood content was consistently high for C. macrocarpa, but varied widely for C. lusitanica, and the Leyland and Ovens cypress clones. The weight loss was similar for the species and cypress clones, with the heartwood classified as very durable and durable, but there were differences in the distributions of less durable heartwood. The NIR calibration models of mass loss with fungal decay testing had ratios of prediction to deviation (RPD) of 1.0–1.3, which suggests the models could be used to segregate the heartwood for high and low values of natural durability.ZusammenfassungKernholz von Cupressus lusitanica, C. macrocarpa sowie Leyland- und Ovens-Zypresse (×Cuprocyparis leylandii und ×C. ovensii) aus Versuchsplantagen in Neuseeland wurde mittels entnommener Bohrkerne in Brusthöhe und In-Vitro-Abbauversuchen mit Pilzkulturen untersucht, um die Variation des Kernholzanteils und der natürlichen Dauerhaftigkeit sowie dessen Vorhersage mittels Nahinfrarotspektroskopie zu bestimmen. Bohrkernmessungen zeigten, dass die Länge der Bohrkerne stark vom Bestockungsgrad und dem Standort beeinflusst wurde. Jedoch hatten die Holzart und der Genotyp einen starken Einfluss auf den Kernholzanteil und den in Abbauversuchen festgestellten Masseverlust. Der Kernholzanteil von C. macrocarpa war durchweg hoch, streute jedoch stark bei C. lusitanica und den Leyland- und Ovens Zypressenklonen. Der Masseverlust war bei den Baumarten und Zypressenklonen vergleichbar zwischen Kernholz, das sehr dauerhaft und dauerhaft klassifiziert wurde. Jedoch wiesen diese unterschiedliche Anteile an weniger dauerhaftem Kernholz auf. Für den Masseverlust bei Pilzabbauversuchen ergaben NIR-Kalibrierungsmodelle ein Vorhersage-Abweichungs-Verhältnis (RPD) von 1,0 bis 1,3. Dies weist daraufhin, dass die Modelle zur Unterscheidung von Kernholz mit hoher oder niedriger natürlicher Dauerhaftigkeit verwendet werden können.

A ‘Reality Check’ in the Management of Tree Breeding Programmes

Modern tree breeding is now at least 80 years old, and has many successes to report, notably with loblolly pine since the 1920s and with Pinus radiata in New Zealand since the 1950s. Nevertheless, tree breeders are facing various difficult issues, some longstanding, and some new, which will not disappear. These include: meeting the requirement to preserve genetic variation while capturing genetic gain; accelerating the capture of genetic gain through both enhanced selection technology and rapid-deployment propagation systems; coping with changes in perceptions of appropriate breeding goals driven by science, biotic influences, changes in forestry ownerships, and market shifts; harnessing DNA technology with what are still essentially wild organisms; doing so without incurring undue opportunity costs with respect to genetic gains available from conventional breeding; managing cultural differences between classical breeders and those practising the new genomic sciences; and coping with institutional and funding changes.

Phenotyping Whole Forests Will Help to Track Genetic Performance

Phenotyping is the accurate and precise physical description of organisms. Accurate and quantitative phenotyping underpins the delivery of benefits from genetic improvement programs in agriculture. In forest trees, phenotyping at an equivalent precision has been impossible because trees and forests are large, long-lived, and highly variable. These facts have restricted the delivery of genetic gains in forestry compared to other agricultural sectors. We describe a landscape-scale phenotyping platform that integrates remote sensing, spatial information systems, and genomics to facilitate the delivery of greater gains enabling forestry to catch up with other sectors. Combining remote sensing at a range of spatial and temporal scales with genomics will ultimately impact on tree breeding globally.

Assessing the genetic variation of tolerance to red needle cast in a Pinus radiata breeding population

Breeding for disease resistance or tolerance is a viable option for disease management programmes and is important for the continued success and resilience of planted forests. Red needle cast (RNC) is a disease that affects radiata pine (Pinus radiata) and is caused by Phytophthora pluvialis. Knowledge is still very limited regarding the potential for genetic tolerance to this pathogen. The application of controlled screening techniques is clearly required. Using a detached needle assay, we screened 392 clonally replicated individuals (clones) from an elite P. radiata population for quantitative tolerance to RNC. Data was highly skewed and required logarithmic data transformation and Poisson distributions for the estimation of best linear unbiased predictions. These estimates revealed a broad range in susceptibility/tolerance to RNC, and enabled the identification of clones that were clearly susceptible and clones that were clearly tolerant. There was a high correlation between the number and length of lesions that developed in response to inoculation with P. pluvialis. Broad-sense heritability estimates were low to moderate, indicating that there is potential for improving tolerance through breeding. These results provide evidence that breeding for tolerance to P. pluvialis is possible, although continued work into understanding and minimising causes for variance are required.