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ABSTRACTCorymbia citriodorasubsp. citriodorahas a long history of cultivation as a multipurpose tree in China and many other countries in Southeast and South Asia. Despite this history and longstanding interest in the species, published studies examining genetic variation among and/or within provenances/seed sources are scarce. Recognising this and to initiate an improvement program for this species, a field trial was established in southern coastal China in 2015 with 171 open-pollinated single mother-tree family seedlots representing five natural-stand seed sources in Australia and six planted seed sources in China. Large significant variation was found among seed sources for pest and disease resistance, survival, growth and stem form up to age 81 months. Australian seed sources were generally superior to Chinese ones for most traits. Phenotypic correlations among traits, at both the individual tree and seed-source mean levels, were favourable, with the strongest individual tree correlations found between disease susceptibility at 10 months and various tree growth traits. Overall, the variation observed in this field trial indicates the potential gains in this species from seed-source selection and ongoing breeding.

ABSTRACTEucalyptus grandisis one of the main commercial forest plantation species in the highlands of Sri Lanka. An E. grandisgenetic improvement program was initiated in 1995 with the establishment of a first-generation provenance-family trial cum seedling seed orchard (SSO), and several seed production areas (SPAs) using seeds from natural stands in Australia. In 2007 a second generation was initiated, comprising a seed-source/family trial with 132 families from plus-trees selected in Sri Lanka: 72 families from the first-generation SSO, 28 families from two of the first-generation SPAs, and 32 families from plus-trees selected in local plantations. Diameter at breast height (DBH) and tree height measurements were taken at ages 2, 5 and 7 years. Trees from a first thinning conducted just after the 5-year assessment were used for assessment of log end-splitting. Significant differences between seed sources and families within seed sources were observed for individual tree volume but not for log end-splitting. The seed source with the highest 7-year tree volume was the SSO, and the second and third best seed sources were the SPAs. Heritabilities for individual tree volume ranged from 0.04±0.05 at age 2 years (all trial families) up to 0.27±0.12 at age 7 years (subset of the 72 SSO families). Heritabilities for end-splitting were close to zero across all trial families and 0.16±0.15 for the subset of 72 SSO families. Phenotypic and genetic correlations between tree volumes across different ages were positive (favourable) with genetic correlations ranging from 0.39±0.38 to 1.00±0.40. The phenotypic and genetic correlations between individual tree volumes at ages 2 and 5 years with end-splitting at age 5 years were generally positive (unfavourable), with the former ranging up to 0.70 and the latter ranging up to 0.90±0.95. This correlation between tree volume and end-splitting could make simultaneous improvement of these traits difficult. Options for further tree improvement work with E. grandisin Sri Lanka are discussed.

ABSTRACTIn 2006 a research project commenced to breed drought-hardy Eucalyptus globulusfor the lower rainfall Secano area (mean annual rainfall below 1000 mm y–1) of Chile’s Bío-Bío Region. Three populations were included in this project: (a) open-pollinated families of selected clones from a seed orchard of INFOR’s tree breeding program; (b) open-pollinated families of plus-trees selected from plantations of landrace origin grown under dry conditions; and (c) control-pollinated families generated by intraspecific crosses between populations (a) and (b). This paper presents results of one control-pollinated and two open-pollinated family trials on three sites representative of drier areas of Chile’s central Bío-Bío Region in 2009–2010. Growth parameters, including heritabilities and genetic correlations, of E. globulusto ages 5 to 6 years were estimated from 24 control-pollinated families at one site, and up to 61 open-pollinated families at the other two sites. Family performance was also compared with commercial E. globulusseed sources, and with seedlots of the drought-tolerant species E. camaldulensisand E. cladocalyx. There were no significant differences between the average growth of the E. globulusseed sources at any of the three sites, but there were large, significant differences between families within seed sources for average growth. In general, the top-ranked groups of families were dominated by those having as parents plus-trees of local Secano plantation origin that had been selected for superior growth and form. Conclusions presented relate to the applicability of this strategy for improving productivity of E. globulusin drier areas of the Bío-Bío Region.

ABSTRACTA preliminary assessment of climate change impacts on planting domains is presented for Eucalyptus pellitaand the E. urophyllax E. grandishybrid in parts of China and south-east Asia. Simple descriptions of climatic requirements are verified and, where necessary, refined. Climate data for current conditions and projected temperature rises of 1.10, 1.96 and 3.83°C (means across the study area compared against a 1986–2005 baseline) are then used to map at a 10-minute (about 18 km) resolution areas that are likely to have suitable climatic conditions for growing these species in the future. For E. pellitaa 1.10°C temperature rise has little impact on climatically suitable areas, while E. urophylla x E. grandismay lose some currently suitable areas in southern China and Sumatra. If temperatures rise by more than 2°C, then larger currently suitable areas will fall outside the range of climatic conditions that are known to be suitable for the two taxa. The vulnerabilities of eucalypt plantations of the two taxa across the study region are generally low, as the short rotation lengths used should allow managers to adapt plantations relatively easily to changing conditions. While this preliminary analysis suggested climate change risks are manageable, the analysis highlighted two risks that are worthy of more detailed research: some existing E. urophylla x E. grandisplantations in lowland areas in Sumatra appear to experience similar climatic conditions to those where leaf diseases have been experienced in Brazil, and extreme frost risks exist in inland areas of southern China.