Sweetpotato SpeedBreeders and Genomics CoP visits Rubona Research Station

On the morning of 17 May 2017, two buses departed from Grand Legacy Hotel, the venue of this year’s SpeedBreeders and Genomics Community of Practice (CoP). The 39 participants were on a field trip to Rubona Research Station in the Southern Province of the country. As the hills for which this country is famed for emerged from the morning mist, the participants’ energy and excitement began to rise. For many, it was the first visit, and they were looking forward to learning how research was driving the transformation in sweetpotato production.

The Rubona Research Station is located in Rusatira sector of Huye district in the Southern Province. With a staff capacity of over one hundred scientists, it is the largest research stations of the Rwanda Agriculture Board (RAB). RAB is in charge of developing agriculture and animal husbandry through reform and using modern production methods, research, agricultural extension, and education and training farmers in new technologies. The Rubona Station has a large research component on root and tuber crops, including a sweetpotato program supported by the International Potato Center (CIP).

Producing disease-free sweetpotato pre-basic seed

Sweetpotato is an important food and nutrition security crop in Rwanda. However, farmers here, like in other African countries, face problems accessing healthy planting material. Often, they save vines from previous harvests, which if infected with viruses, will lead to lower yields. Where the planting material is shared with other farmers, the virus infection could spread to other fields.

This is where the tissue culture laboratory comes in. Tissue culture is a term that generally describes the culture of cells, tissues or organs in a nutrient medium under sterile conditions. It is a promising technology that the Rubona Research Station is using to conserve and multiply disease-free sweetpotato planting material in vitro.  The starter material is sourced from the Kenya Plant Health Inspectorate Service (KEPHIS) in Kenya.

At the tissue culture lab, Julius Kagabo (RAB) led the SpeedBreeders and Genomics CoP on a tour to observe the transfer of material into nutrient media and how the growth room is maintained. Prior to this, they visited the plant pathology lab, where they found out how sweetpotato planting material is tested for viruses.

While it is not always possible to physically identify the virus symptoms on infected plants, the plant pathology team uses grafting on I. setosa to confirm whether the plantlets are completely free of virus infection before they are used for micropropagation in the tissue culture lab. Tissue culture plantlets provide the source of disease free materials that are multiplied through different stages of the seed system.

“We aim to produce few plantlets in the tissue culture lab, increase the cuttings in the screen houses and increase our production capacity to 15,000 per screen house every 2-3 months,” said Jean Ndirigwe, a member of the CoP and the head of the sweetpotato program at RAB.

These cuttings will be sold to about 50 registered decentralized vine multipliers to multiply in the open field and distribute to other farmers. The end-result is that farmers will receive planting material that are free from viruses and other diseases.  This is part of RAB’s strategy to hand over seed production to the private sector, and concentrate on research and provision of pre-basic seed.

Improving sweetpotato varieties

At the crossing block, Ndirigwe explained that the breeding focus in Rwanda is on high yield, high dry matter and resistance to sweetpotato virus disease. “Farmers in Rwanda really like the Vita orange-fleshed sweetpotato variety, which is high yielding and has high dry matter,” he told the participants, among them Robert Mwanga, the co-leader of the SpeedBreeders and Genomics CoP, and the breeder who developed this particular variety. Ndirigwe added that Gihingumukungu, an orange-fleshed variety that was developed in Rwanda, was performing well in high altitude areas with low virus pressure. It is preferred particularly for puree processing because it has low dry matter.

Taste testing unsweetpotato varieties

Participants participated in a taste test of sweetpotato varieties, which included unsweet varieties developed in Ghana. A taste test is a tool used to gather information about consumer perceptions about attributes of a food or product. “Typically, appearance and taste are the key attributes when it comes to evaluating consumer preferences. We know that we have to give more attention to sensory panels and what consumers want,” stated Ted Carey, who led the taste test.

The members of the SpeedBreeders and Genomics CoP used a 9-point scale to rate the cooked varieties based on appearance, fire, cooked taste, aroma, sweetness and cooked texture. Apart from providing some data for the breeders from Ghana, the exercise also demonstrated the challenges of using consumer panels for taste tests. Based on the findings, he highlighted the need for calibration of the people participating in the panels, to ensure that the findings are relatively accurate.

For both the participants and the RAB team, the visit was a great learning opportunity. “The breeders come from different countries and we wanted to get some insights on how to improve our work and reduce the costs,” says Ndirigwe.