Potato production has a rich history in the Republic of South Africa (RSA). The first breeding programme in that country was initiated by the late Dr JE van der Plank back in 1950. Over the years, the focus of the breeding programme shifted from seed security and virus resistance in the 1950’s, to good yield and skin finish characteristics as the primary focus.
The bulk of South Africa’s potato output is done by about 530 large commercial producers on approximately 55 000 hectares. A small percentage of the total production comes from small-scale farm holders, estimated to be less than 500 hectares. The drive of the RSA government is to get small-scale farmers much more involved in potato production and by this means increase household food security and also income.
Going forward the potato breeding programme in RSA needs to focus on acceptable yields with limited input in order to accommodate the needs of these up and coming small scale farmers. The focus of commercial farmers to date was maximum marketable yield only. The difference between these two objectives speak for itself.
Philippus Steyn and Dr Lerato Matsaunyane are in charge of the potato breeding programme at the Agricultural Research Council (Vegetable and Ornamental Plants) facility based at Roodeplaat near Pretoria.
Recently they initiated a project to evaluate past achievements of the national potato breeding programme in RSA – taking a critical look at particularly the last three decades of breeding efforts in South Africa.
The elite potato trials planted at Roodeplaat from September 1982 to 2010 were used for this evaluation study. A total of 495 potato genotypes were evaluated in 28 trials. Gains with regard to yield, tuber dry matter (DM), dry matter yield (DM Yield) and crisp fry colour were evaluated.
Steyn explains the fundamentals that underpinned the premise of their evaluation study. “Plants converts the energy received from the sun into different components that makes up the plant,” he says.
“The farmer is interested in the parts that can be marketed and used as food. Researchers look at this efficiency as the ability to produce dry matter per hectare. The plant breeder on his part tries to improve this efficiency over time, by breeding and releasing varieties that are better equipped to convert the sunlight received into dry matter (genetic gain).”
“To compare different crops with each other, we need to remove al the water from the interested parts (tubers in the case of potatoes) to be able to compare ‘potatoes with potatoes’” Steyn says.
“On average, potato tubers contain about 20% dry matter with the rest being water. Determining the genetic gain tells the breeder if he or she is successful in improving the crop over time, and also how successful the achievement was.”
Steyn notes that Dr Matsaunyane and himself then used this measurement to determine the improvement of varieties over time, and they only look at the best five varieties from each trial for a specific trait, and then compared it to a single variety that served as the benchmark.
The variety BP1 bred by the late Dr Van Der Plank in the 1960’s was used as a benchmark. The genetic gains in three traits were determined: Tuber Dry Matter (TDM), Dry Matter yield (DM-yield) and fry colour.
The breeders found that varieties developed in the South African potato breeding programme showed an improvement of 0,42% regarding tuber dry matter year on year.
“This value tells the processing company a lot about the varieties being developed potential to be processed into frozen fries or crisps in the factory but not a lot on what the farmer can expect of each hectare harvested,” Steyn points out.
He says the DM-yield is easily determined by multiplying the yield with the TDM percentage. Comparing the DM-yield values over time in the breeding programme a genetic gain of 1,70% was achieved.
“The top five candidates regarding TDM varieties will differ from the top DM-yield candidates,” Steyn says. “Candidates in both the top 5 groups will be good processing varieties that is of value for both the processor and the farmer.”
“This research shows that the breeding programme between 1982 and 2010 focussed on producing varieties with value to the processing industry,” Steyn says. “Darius was one of the processing varieties released by the ARC during this period, and at one stage represented almost 10% of all potatoes produced in South Africa.”
Sugars produced in the leaves of the plants is transported to the tubers and then converted into starch. This conversion process is faster in some varieties than others. This is easily determined by frying 3mm thick slices in oil at 180⁰C for 3 minutes, according to Steyn. “Darker crisps has more of the unconverted sugars and can become a problem for processing into crisps.”
As with DM-yield, this trait was also evaluated by Steyn and Matsaunyane. Year on year they found that there was an improvement of 0,16%. “Although the trait was improving it might be more difficult to breed for it specifically, or perhaps not as important as DM-yield in the breeding process,” Steyn points out.
Steyn and Matsaunyane agree on this: “Being a potato breeder in RSA today is the best possible job position one could hope for. Not only do you have to apply the art of selecting the best varieties, you have all the modern tools available with incredible people applying their trade working towards the same goal.”
On the other hand, they say, you are also working directly with farmers trying to bring change to their future and influence the future of their communities for the better.
“The decisions made by the breeder today will have an impact in the next eight or ten years’ time,” the breeders point out. “We believe that the task of the breeder is ultimately to reduce input costs for farmers by releasing improved varieties and constantly improving the quality of the spuds being grown. Improving dry matter and adaptability to an ever-changing environment are key to breeding success.”
The only way forward to achieve this, is to reduce the impact of chemicals used in farming by breeding for disease resistance and tolerance to heat and drought, they say.
“It is no longer a matter of how much tonnes per hectare, but rather what is the best yield with the lowest cost to the farmer and reduced impact on the environment.”
Philippus Steyn can be reached at email@example.com for further information.
This article was first published in the February issue of Global Potato News magazine.