Improving controlled pollination methodology for breeding Acacia mangium Willd.

Abstract

Acacia mangium is a major plantation species for the pulp and paper industry in south-east Asia and there are a number of active breeding programs. The species is predominantly outcrossing, but with a demonstrated capacity to set selfed seed where outcross pollen is limited, with consequent inbreeding depression in the progeny. Current controlled pollination methods therefore include a time-consuming emasculation step. We used microsatellite genotyping of seedlings to determine the consequences of outcross pollination with and without emasculation. Only 1 of 3 mother trees set a small amount (5%) of selfed seed. Using whole inflorescences from the male parent as the pollen applicator rather than sieved pollen reduced outcross contamination rates from 19.1 to 8.7% and substantially increased worker productivity. Application of sugar solution to the female flowers immediately prior to pollination increased yield of sound seeds per spike. Additional improvements to the pollination protocols are discussed.