All of the plant material for South Africa’s banana industry comes from a single tissue culture laboratory, which also exports to 25 countries throughout Africa, the Middle East and the Indian Ocean islands.
Du Roi Laboratory in Letsitele, Limpopo Province, produces 8 to 10 million banana plants annually, going as far afield as Samoa, but 30 to 40% of their output is for domestic production.
Banana plant material may not be imported into South Africa nor moved across areas without a government permit, and with the TR4 strain of Panama disease already present in northern Mozambique, traceability and the guarantee of disease-free material is of the utmost importance.
Every single initiation tested for disease
“What we do differently from many international labs, is to test each and every sucker for diseases like Panama disease, banana bunchy top virus (BBTV) and others, even though South Africa doesn’t have Panama disease and even though the disease cannot be transmitted through the tissue culture process, but just to give our clients peace of mind,” explains Suné Wiltshire, general manager of the laboratory.
They multiply plant material from suckers, grown on in the 4ha mother block with 9 commercial and 5 additional varieties (some exclusive to Du Roi Laboratory) which has taken them years to develop and establish, focusing on commercial characteristics like a more cylindrical bunch, a quicker life cycle (usually 12 to 14 months under South Africa’s subtropical conditions, compared to the 6-month tropical life cycle) and plants of a more manageable height.
Mutation risk reduced by limited number of multiplications
In nine growing chambers under controlled temperature, humidity and light conditions the plant material, extracted from the growth tip of a sucker, develop for four weeks. Then it is further dissected (each tiny piece must contain meristematic tissue which will grow into shoots) and back to the growing chambers for a further month. This process is repeated five times and could, theoretically, continue indefinitely but by stopping the process at this point, the risk of mutation remains at less than 1%.
This five-month process renders 2,000 plants, which are then rooted in Du Roi Laboratory’s proprietary rooting hormone for a month.
The first age at which banana plants are sold, is at the in vitro stage, sold in batches of 50 plants with 10% extra (to account for losses). These tiny plants can be transported by air freight but do require that the receiver weans and hardens them off; roughly a quarter of their clients buy in vitro plants.
Banana producers without weaning facilities buy their plants at the in vivo (5cm) stage or at the field-ready (20 cm) stage.
“Our plant material may not the cheapest and many international labs are cheaper. It’s sometimes tempting for producers busy with large projects to cut costs in this way, but it endangers the banana industry,” she says.
The women who multiply banana plants
Multiplying banana plants is an intense and rigorous task, which the laboratory workers (all women) cannot perform for more than four hours at a stretch. Four shifts run from 3am (with an on-site crèche open at that time of the night for women starting their shift) until 10pm in an immaculately sterile environment with a pungent smell of alcohol.
It takes laboratory staff six months to become sufficiently adept at the multiplication process to reach their target of 3,500 multiplications per day, or 1,800 pieces rooted and graded into small, medium and large.
The South African industry prefers Williams, a variety forgiving of harsh conditions and management challenges, Suné says, but it is outperformed by their elite single clones like Nandi, Asdia and Apollo.
“The banana industry is very sensitive to what’s going on in the market and with the weather. Every now and then when banana prices rise, there’s more interest in our plants, and when macadamia prices rise, we see a drop in sales. With bananas you can get a harvest within the first year, so there’s a very quick turnaround in the industry.”
For more information:
Suné Wiltshire
Du Roi Laboratory
Tel: +27 15 345 1217
Email: sune@duroilab.co.za