Fresh fruit remains at the centre of most healthy diets. Apples, oranges, apricots, pears, in fact, anything that one can eat fresh has health benefits to the consumer.
And fresh fruit exports represent more than 7% of South Africa’s export with its largest trading partner, the European Union. South African fruit is highly sought-after overseas. This positive perception enhances our fruit products’ export potential, making it imperative to remain at the forefront of the technology that will perpetuate this situation.
Efforts have been made since time immemorial to improve the quality of fruit by natural selection, to breed trees that are hardened against prevailing soil conditions and local water availability, as well as onslaughts by fungi, pests and weeds and, these days, also the changing weather patterns evidenced globally.
Enter into this modern-day scenario the fruit tree genetics programme at the University of the Western Cape, which is run in collaboration with the Agricultural Research Council (ARC). The aim of the programme is to develop and use molecular marker technology to improve the breeding programmes in apples and pears.
The programme was started with the specific aim to develop markers tightly linked to commercially important traits, which are then used to screen the progeny of the breeding programme.
Says programme head, Professor Jasper Rees: “We are particularly looking at markers linked to genes controlling traits like pest and pathogen resistance, reduced chilling requirements for dormancy break and other improved horticultural properties, such as long-term storage, of course.
“This last property is of major importance in the export market, as fruit might be delayed en route to its destination and being able to time it to arrive fresh and flavourful makes the difference in every shop it reaches.”
The conventional breeding programme was started more than 30 years ago and the plant breeder in the programme, Dr Iwan Labuschagné, produces the 20 000 to 25 000 seedlings that are planted each year.
But, by using molecular genetic selection strategies, the aim is to be able to increase the number of plants to 100 000 annually.
Labuschagné says that by increasing the starting number of seedlings and using genetic selection it is possible to combine traits more effectively and in a shorter period of time. By selecting for genes that control traits that can be detected only after several years of field trials, such as fruit quality, it becomes possible to improve the speed and success rate of the selection process.
By developing new cultivars that are resistant to the major diseases affecting apples and that have low winter chilling requirements, it will be possible to reduce the chemical inputs of fungicides, pesticides and dormancy breaking agents that are required for production.
This will reduce costs and make it possible to meet increasingly stringent controls on chemical residues. Rees says “this way the producer and consumer will both benefit from the new varieties”.
Genetic maps are being pre- pared for apples and pears from this project. Molecular markers controlling qualities like time of bud break and disease resis-tance to apple scab have been identified already.
This knowledge will now be put to use by assisting in the selection of new cultivars for plant breeding. But disease resistance was only the first port of call. Other traits are also being addressed.
“Fungal pathogens, in particular apple scab, is being studied to determine the mechanisms of resistance to this pathogen. We are evaluating the apple Vf genes as markers for scab resis-tance and are using the genes in molecular selections; but in the future we aim to incorporate scab resistance from different sources, creating “durable resistance” that is not easily overcome by mutations in the fungal genome.
“Our medium-term objective is to deliver marker selected apple seedlings based on five identified genetic markers for the breeding programme, then these can be used to undertake the proof-of- concept analysis to determine its value.
The project has been incorporated into the International Rosaceae Genomics Initiative, allowing the exploitation of genome sequences of apple and peach when these are completed in 2008 and for the development of other technologies, as well as collaboration with the EU-FP6 ISAFRUIT Consortium, thereby opening the way to extending the research done locally to stone fruits like the plums, peaches and apricots.
“The long-term goals are to develop apple and pear culti-vars in collaboration with the ARC breeding programme that have durable resistance to diseases and pests to allow for lesser use of fungicides and pesticides. The aim is to assist in the selection process for low chilling requirements so as to optimise the crops for warm winter climate conditions.
“These are indeed crucial for the development of locally adapted cultivars, which will prove to be essential for the long-term economic survival of the South African deciduous fruit industry,” he says.
As the molecular techniques start to play a role, however, cultivars already developed by the ARC are starting to hit the market; newly released cultivars “African Carmine” and “Elegant” are being marketed by the new company, CulDevCo, and should be visible in local supermarkets in the near future.
Rees says traditionally breeding programmes have taken a generation to produce new varieties and market penetration has been difficult. He foresees that market demand will move away from named varieties to generic brands, in other words, consumers will ask for “green apples” rather than “Granny Smith apples”.
He says the advantage of this is that apple varieties could become more varied, but still meet market needs and allow for rapid replacement of older orchards. Eventually this will lead to higher profitability and competitiveness.