Genetic control of Eucalyptus urophylla and E. grandis resistance to canker caused by Chrysoporthe cubensis

Chrysophorte cubensis induced canker occurs in nearly all tropical and subtropical regions where eucalypts are planted, causing losses in both wood quality and volume productivity, especially so in the warmer and more humid regions of Brazil. The wide inter and intra-specific genetic variability of resistance to canker among Eucalyptus species facilitates the selection of resistant plants. In this study, we evaluated resistance to this pathogen in five Eucalyptus grandis (G) and 15 E. urophylla (U) trees, as well as in 495 individuals from 27 progenies derived from crosses between the trees. In the field, six-months-old test seedlings were inoculated with C. cubensis. Lesion length in the xylem and bark was measured eight months later. The results demonstrated that xylem lesions could preferentially be used for the selection of resistant clones. Eight trees (7 U and 1 G) were susceptible, and the remainder (8 U and 4 G) resistant. Individual narrow and broad sense heritability estimates were 17 and 81%, respectively, thereby suggesting that canker resistance is quantitative and highly dependent on dominance and epistasis

Assessment of three-year DBH and height data and genetic gain prediction for five Acacia mearnsii (black wattle) subpopulations in South Africa using REML/BLUP

Recent research has shown Acacia mearnsii (black wattle) to be a source of high-quality pulp. This led to a change in the emphasis in the breeding programme at the Institute for Commercial Forestry Research, from improving bark yield and quality, to improving timber yield and quality while maintaining an acceptable bark quality. A Multiple Population Breeding Strategy was implemented to cater for these changes. Six subpopulations were established across different sites in KwaZulu-Natal and were determined by origin of seed. Five of these subpopulations were established in 2002 and the sixth one in 2004. Each subpopulation was established as a progeny trial with a breeding seed orchard adjacent to it. The management of the seed orchards will be determined according to the performance of the families within the progeny trials. This paper is a summary of the three-year growth measurements taken from the first five subpopulations. The results showed promising heritability values with respect to genetic gain. These data were then projected to estimate results at full rotation using appropriate growth models. Results showed that if one selects the top 20 individuals, mean annual increments (MAIs) of 13.20–19.60m3 ha–1 y–1 can be expected. If one selects the top 20 families, MAIs of 10.60–19.10m3 ha–1 y–1 can be expected. Growth data will continue to be collected each year. This will allow for continuous assessment of age–age correlations for the various traits being assessed, and will provide an appropriate decision-making tool for selecting individuals for future generations.Southern Hemisphere Forestry Journal 2007, 69(2): 111–11