Hardwood Breeding (Wattle)

Acacia mearnsii De Wild (black wattle) is an important forestry plantation species for tannin production and woodchip exports in South Africa, and breeding of this species is the key focus of the Acacia Tree Improvement project at the ICFR. Research to date has made significant improvements in bark yield, tannin content, tree volume, stem form and disease incidence (gummosis) during the first decades of the breeding programme.

During the last decade, one of the main challenges for further improvement has been the high levels of relatedness that has built up in the breeding population. Different approaches to managing this problem have included sublines and multiple populations. A breeding strategy and operational breeding plan was developed in 2013 with the aim of ensuring short and long term genetic gains, while maintaining relatedness within acceptable levels. The main objectives are to increase timber and bark yield, and to continue improving stem form. Improvement in frost tolerance is also a priority for the frost-prone areas.

In 2014, a new disease in black wattle, caused by a rust fungus (Uromycladium acaciae), emerged in KwaZulu-Natal, and research is now prioritised on the development of wattle-rust tolerant genetic material. In addition, the establishment of new seed orchards to supplement the four remaining Production Seed Orchards is another activity of high priority for the wattle industry.

Research Projects

Breeding for tolerance to wattle rust

Following the recent outbreak of wattle rust in 2014, research has focused on developing disease-tolerant genetic material by identifying genetic variation and tolerance to the disease in the existing breeding populations. The objective is to develop and implement a breeding strategy to manage wattle rust in Acacia mearnsii, including developing tolerant seed sources for the wattle industry.

Breeding for Frost Tolerance

Frost damage is an ongoing problem in the wattle growing areas of south-eastern Mpumalanga and northern KwaZulu-Natal. Significant efforts in breeding research for frost tolerance in black wattle have been undertaken and deployment of improved seed for frost-prone areas remains work in progress.  

Seed Orchards ( Improved seed for non-frost areas)

The ICFR manages valuable black wattle seed orchards which provide the Industry with improved seed. After losses due to storm and wind damage as well as natural decline, there are currently four orchards remaining in productive condition. Recent efforts have been to establish four new orchards which will ensure a sustained supply of improved seed to the Wattle Industry for non-frost areas.

Development of Cutting Protocols

The development of rooted cutting protocols is fundamental to the Acacia breeding programme, to enable the propagation and establishment of clonal seed orchards and thus increase genetic gain deployed from the breeding programme. Rooted cuttings also play a major role in testing A. mearnsii individuals tolerant to wattle rust. Current research efforts are focussed on optimising rooting protocols, developing acclimatisation protocols and optimising the rooting medium.

Development of Hedge Management Protocols

Also linked to propagation protocols for black wattle is the need to manage hedge plants effectively. Very little is known about how A. mearnsii responds, as a hedge plant, to constant pruning and to being kept in a container. In particular, it is important to determine the productivity of a hedge in relation to its size and age (i.e. number of cuttings per hedge plant per harvest, number of harvests per season), as well as optimising the nutritional requirements of the hedge plants to maximise productivity and successful rooting of cuttings.

Acacia Molecular Genetics

For a breeding programme, quality control of genetic identity is essential to ensure optimum capture as well as prevent losses in genetic gain. This project aims to establish an SSR-based DNA fingerprinting tool to assist in ensuring optimum capture and transfer of genetic gain for the Acacia breeding programme.