and deficits, and dry matter content (which affects taste and storability) to manage the vagaries
of both nature and the market (Scott, 1988; Durr, 1980, Poats, 1981).

Since most potato varieties introduced into Rwanda before the late 1970s were from a relatively
narrow genetic base (European-adapted Solanum tuberosum), cultivar diversity provides less
protection against environmental hazards than in the crop's Andean homeland. Nonethless,
Rwandan farmers do use the available diversity to help reduce their production, consumption and
marketing risks, and to spread labour requirements and food supplies more evenly across the
annual cycle. Cultivar mixtures allow the use of staggered harvests and varied growth cycles,
which permit farmers to extend the period of fresh food and cash availability.

Distinctions between 'traditional' and 'modem' varieties, always problematic, are quickly
blurred in Rwanda, where potatoes have only been grown for about a century, and where in recent
decades dozens of cultivars have been introduced, from Europe and South America in particular.
The four most frequently grown potato cultivars in Rwanda (Montsama, Sangema, Gashara, and
Muhabura) have diverse origins. Agricultural research institutions introduced Montsama and
Sangema into Rwanda from Mexico in the 1970s, and Gashara from Europe a number of decades
ago. Farmers and traders probably brought Muhabura into Rwanda from Uganda. Montsama,
Muhabura and Sangema were multiplied and distributed by the Rwandan national potato research
programme (PNAP) in the late 1970s and early 1980s.

Farmers rate these four popular cultivars as having distinctly different maturity and dormancy
periods, water content, cooking time, storability, late blight resistance, market acceptability,
response to moisture stress, and suitability for intercropping (Haugerud, 1988). The variety
Muhabura, for example, though disliked for its taste and poor storability, is appreciated for its
short dormancy. Farmers appreciate Sangema for its taste, market acceptability, yields under
good rainfall, and late blight resistance (which Rwandan farmers equate with good yield under
heavy rain), though they appreciate less its long dormancy and long growth cycle.

The degenerated cultivar (degeneration refers to accumulation of viruses) Gashara would have
been abandoned long ago if disease resistance and yield were farmers' sole decision criteria.
Many farmers continue to cultivate Gashara, however, because of its short growth cycle, short
cooking time, short dormancy, and good taste (low water content). The continued popularity of
this cultivar suggests one neglected strategy for current breeding and germplasm screening. We
return later to this and other implications of the farm survey work for germplasm screening in
Rwanda.


East African Farmers' Use of Maize Cultivar Diversity

Farmers recognize in maize, as in potato cultivars, important differences in taste, texture,
storability, marketability, disease and pest resistance, and response to moisture stress. At least
nine possible end uses, many of them simultaneously relevant on a single farm, help to determine
the maize genotypes east African farmers prefer. The crop may for example, be consumed at
home green or dry brewed for beer, or sold green or dry. In addition, the plant and grain may be
used green at various stages of maturity, or dry as food for livestock. Cultivar mixtures in maize,


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