Keywords: Potato, positive selection, viruses, seed potato systems, East Africa, Kenya,
Potato (Solanum tuberosum L.) is a crop with a high potential to contribute to poverty
reduction in Eastern Africa through income increase and improved food security. It is
largely grown by smallholders, has a high production per hectare, stable prices and a
steadily growing demand. Average yields in Eastern Africa of 10.5 t/ha are much below
the world average and yields observed in the fields of better performing smallholders.
There is both a need and a potential for increased potato productivity.
A diagnosis of the potato systems of Kenya, Uganda and Ethiopia identified
integrated management of bacterial wilt (Ralstonia solanacearum) and late blight
(Phytophthora infestans), soil fertility management, and improving seed potato quality as
technology-based opportunities for innovation. Improvement of potato supply chains and
the knowledge exchange in the sector were identified as systemic opportunities for
improvement. Analysis of the seed potato system confirms that both virus diseases and
bacterial wilt are likely contributors to the low yields. In only 3% of seed potato tubers
sold in rural markets was free of PVY, PLRV, PVX and PVA. Ralstonia solanacearum was
found in 74% of potato farms sampled in Kenya.
Less than 5% of the seed potatoes used are sourced from specialized multipliers
(specialized chain). Farmers rely on seed potatoes from neighbours and farm-saved seed
potatoes (local chain). This often makes economic sense in the absence of affordable high
quality seed potatoes and limited market security. Seed potato system interventions need
to tackle the local and specialized chain simultaneously. Private investment in specialized
multiplication could stimulate the production of affordable high-quality seed potatoes.
For local chain improvement training on seed quality maintenance and on bacterial wilt
and virus management is needed. Research into the mitigation of yield-reducing effects
of indiscriminate seed potato recycling, such as research on virus resistance and positive
selection deserves attention.
Positive selection, the selection of healthy looking mother plants for the production
of seed potatoes, can contribute to improving quality management in the local chain. In
farmer managed trials in Kenya it gave an average yield increase of 34% which
corresponded to a 284 Euro profit increase per ha. It requires no cash and only 4 man-days
per hectare and is an important alternative and complementary technology to regular
In 18 replicated trials it was shown that positive selection lowered the incidence of
PLRV, PVY and PVX with 35%, 35% and 39%, respectively, and increased yields irrespective
of the agro-ecology, crop management, soil fertility, variety, and quality of the starting
material with an average 30%, compared to current farmer practice. Regression analysis
showed that this reduction in virus incidence contributed to the higher yields, but did not
fully account for the effect. Probably other, not tested, virus diseases and other seed borne
diseases also played a role. It can be concluded that positive selection can benefit all
smallholder potato producers who select seed potatoes from their own fields, and should
thus be incorporated routinely in agricultural extension efforts.
In retrospect the research trajectory can be considered a successful contribution of
agricultural research to innovation. It shows that it is worthwhile to search for opportunities
for incremental innovation that do not require institutional change and that these
opportunities can be of a surprising simple nature, and based on old technology. Essential
for researchers to contribute to innovation is room to manoeuvre and opportunity to
immerse in practical collaborative partnerships with practitioners. Most importantly,
innovation needs to be made a central objective, rather than research results, and the
mandate of research needs to be broadened and allow for the active engagement in
training, communication and scaling-up.
|Qualification||Doctor of Philosophy|
|Award date||20 Jun 2012|
|Place of Publication||S.l.|
|Publication status||Published - 2012|
- solanum tuberosum
- seed potatoes
- plant viruses
- east africa