Colchicine-induced neoautotetraploid genotypes of Acacia mangium were cloned and planted in mixture with a set of diploid clones in an orchard in southern Vietnam. Following good general flowering, open-pollinated seed was collected from trees of both cytotypes and microsatellite markers were used to determine the breeding system as characterised by the proportion of outcrosses in young seedling progeny. As predicted from the literature, the progeny of diploid clones were predominantly outcrossed (tm = 0.97). In contrast, the progeny of the tetraploid clones were almost entirely selfs (tm = 0.02; 3 of 161 seedlings assayed were tetraploid outcrosses and there were no triploids). Segregation at loci heterozygous in the tetraploid mothers followed expected ratios, indicating sexual reproduction rather than apomixis. Post-zygotic factors are primarily responsible for divergence of the breeding systems. Commonly, less than 1 % of Acacia flowers mature as a pod, and after mixed pollination, diploid outcrossed seed normally develops at the expense of selfs. Selfs of the tetraploid trees appear to express less genetic load and have a higher probability of maturing. However, this does not fully explain the observed deficiency of outcross tetraploid progeny. Presumably, there are cytogenetic reasons which remain to be investigated. In nature, selfing would increase the probability of establishment of neotetraploids irrespective of cytotype frequency in the population. Breeders need to review their open-pollinated breeding and seed production strategies. It remains to be seen whether this is an ephemeral problem, with strong fertility selection restoring potential for outcrossing over generations.

Item Type:	Refereed Article
Keywords:	Acacia, polyploidy, breeding systems, self-fertility
Research Division:	Agricultural, Veterinary and Food Sciences
Research Group:	Forestry sciences
Research Field:	Forestry management and environment
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Forestry
Objective Field:	Hardwood plantations
UTAS Author:	Griffin, AR (Professor Rod Griffin)
UTAS Author:	Vuong, TD (Mr Duc Tran)
UTAS Author:	Vaillancourt, RE (Professor Rene Vaillancourt)
UTAS Author:	Harbard, JL (Ms Jane Harbard)
UTAS Author:	Nghiem, QC (Miss Quynh Nghiem)
ID Code:	82550
Year Published:	2012
Web of Science® Times Cited:	18
Deposited By:	Plant Science
Deposited On:	2013-02-06
Last Modified:	2013-05-15
Downloads:	0