Red root rot disease caused by Ganoderma philippii is one of the most economically important diseases of tropicalAcacia species. Research on field control of the disease has to date focused on inoculum reduction, silviculture practices and application of biological control agents. Incorporation of tolerant genotypes, a key component of integrated disease management, has not been adequately explored because of a lack of reliable and quick screening protocols. Recently, we developed a more rapid method of screening for red root rot tolerance in Acacia mangium, A. crassicarpa and A. mangium  A. auriculiformis hybrid planting stock, in which groups of five, 6-week-old plants were subjected to inoculum consisting of a rubber (Hevea brasiliensis) wood block culture of the pathogen held within a polythene bag. As symptoms start to appear 10 weeks after inoculation, experiments can be completed in a six-month period instead of the years needed by the traditional pot system. Using this technique we were able to identify variations in tolerance and/or susceptibility to G. philippii in A. mangium, A. crassicarpa and A. mangium  A. auriculiformis hybrid planting stock in a more consistent manner. Tolerant and susceptible genotypes subsequently have been selected for further experiments or crosses. While the ultimate goal of this study was to develop and deploy high-yielding Acacia genotypes that are also tolerant to red root rot disease, results of the current screening studies may also be used to investigate the basis for tolerance to G. philippii in Acacia species.

Research Highlights: This study provides a comprehensive set of wood and pulping properties of Acacia crassicarpa A.Cunn. ex Benth. to assess variation and efficient sampling strategies for whole-tree level phenotyping. Background and Objectives: A. crassicarpa is an important tree species in Southeast Asia, with limited knowledge about its wood properties. The objective of this study was to characterize important wood properties and pulping performance of improved germplasm of the species. Furthermore, we investigated within-tree patterns of variation and evaluated the efficiency of phenotyping strategies. Materials and Methods: Second-generation progeny trials were studied, where forty 50-month-old trees were selected for destructive sampling and assessed for wood density, kraft pulp yield, α-cellulose, carbohydrate composition, and lignin content and composition (S/G ratio). We estimated the phenotypic correlations among traits determined within-tree longitudinal variation and its importance for whole-tree level phenotyping. Results: The mean whole-tree disc basic density was 481 kg/m3, and the screened kraft pulp yield was 53.8%. The reliabilities of each sampling position to predict whole-tree properties varied with different traits. For basic density, pulp yield, and glucose content, the ground-level sampling could reliably predict the whole-tree property. With near infrared reflectance spectroscopy predictions as an indirect measurement method for disc basic density, we verified reduced reliability values for breast height sampling but sufficiently correlated to allow accurate ranking and efficient selection of genotypes in a breeding program context. Conclusions: We demonstrated the quality of A. crassicarpa as a wood source for the pulping industry. The wood and pulping traits have high levels of phenotypic variation, and standing tree sampling strategies can be performed for both ranking and high-accuracy phenotyping purposes.

Three screening trials of clonally replicated Acacia mangium seedlings were evaluated for survival and lesion length following inoculation with locally collected strains of Ceratocystis in Indonesia. Tolerance in the population was low with 6.7% of the 1033 clones represented by more than 4 ramets surviving repeated inoculations. Differences in tolerance among populations were slight; however, populations with consistently higher survival and shorter lesion lengths were from Papua New Guinea rather than Queensland. Estimates of the proportion of the experimental variation attributable to differences among parents (heritability) were low to moderate for both survival and lesion length. Estimates of the proportion of the experimental variation that was attributable to differences among clones (repeatability) were greater but typically similar to the heritability estimates, indicating that initial improvements from selection will primarily be derived from identifying tolerant parents. While genetic correlations among experiments were positive, estimates could not exclude the existence of host–pathogen interactions. Two validation trials of the tolerant clones were assessed 9 months after establishment; these trials verified that one-third of the clones identified in the nursery screening were also tolerant to Ceratocystis in field trials. The experiments confirmed that nursery screening may be used to quickly focus efforts on parents that produce more tolerant progeny, screening additional seedlings to increase selection intensity rather than using clonal replication to increase accuracy would lead to greater improvements in tolerance and field trials are required to verify disease tolerance at later ages.