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Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
RESEARCH ARTICLE

Genetic control of flowering in spotted gum, Corymbia citriodora subsp. variegata and C. maculata

Myralyn Abasolo A E , David J. Lee B , Lyndon Brooks C , Carolyn Raymond D and Mervyn Shepherd A D F
+ Author Affiliations
- Author Affiliations

A Cooperative Research Centre for Forestry, Southern Cross Plant Science, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia.

B Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast and Department of Agriculture, Fisheries and Forestry, Locked Bag 4, Maroochydore DC, Qld 4558, Australia.

C Division of Research, Southern Cross University, Lismore, NSW 2480, Australia.

D Southern Cross Plant Science, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia.

E Present address: Fairbank’s Selected Seed Co. Pty Ltd, 13/53 Gateway Boulevard, Epping, Vic. 3076, Australia.

F Corresponding author. Email: mervyn.shepherd@scu.edu.au

Australian Journal of Botany 62(1) 22-35 https://doi.org/10.1071/BT13223
Submitted: 23 February 2013  Accepted: 16 February 2014   Published: 28 April 2014

Abstract

Genetically controlled asynchrony in anthesis is an effective barrier to gene flow between planted and native forests. We investigated the degree of genetically controlled variation in the timing of key floral developmental stages in a major plantation species in subtropical Australia, Corymbia citriodora subsp. variegata K.D. Hill and L.A.S Johnson, and its relative C. maculata K.D. Hill and L.A.S. Johnson. Flowering observations were made in a common garden planting at Bonalbo in northern New South Wales in spring on 1855 trees from eight regions over three consecutive years, and monthly on a subset of 208 trees for 12 months. Peak anthesis time was stable over years and observations from translocated trees tended to be congruent with the observations in native stands, suggesting strong genetic control of anthesis time. A cluster of early flowering provenances was identified from the north-east of the Great Dividing Range. The recognition of a distinct flowering race from this region accorded well with earlier evidence of adaptive differentiation of populations from this region and geographically-structured genetic groupings in C. citriodora subsp. variegata. The early flowering northern race was more fecund, probably associated with its disease tolerance and greater vigour. Bud abundance fluctuated extensively at the regional level across 3 years suggesting bud abundance was more environmentally labile than timing of anthesis. Overall the level of flowering in the planted stand (age 12 years) was low (8–12% of assessed trees with open flowers), and was far lower than in nearby native stands. Low levels of flowering and asynchrony in peak anthesis between flowering races of C. citriodora subsp. variegata may partially mitigate a high likelihood of gene flow where the northern race is planted in the south of the species range neighbouring native stands.

Additional keywords: anthesis, Eucalyptus, floral development, gene flow, plantation forestry.


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