1. INTRODUCTION
Cassava growing in Rwanda was first introduced in Rwanda in 1930 by Belgians. Cassava is a staple food crop ranking third in country after sweet potatoes and bananas in terms of importance. The production of cassava has drastically declined in the last decade due to mainly diseases, pests and lack of disease resistant varieties.
The cassava plant is grown for its roots which are used as food. Cassava has the ability to grow on poor soils where other crops do not grow well. Cassava is also a suitable crop to grow when there is drought. Because cassava roots can be stored in the ground for up to 24 months, and some varieties for up to 36 months, harvest may be delayed until market, processing, or other conditions are favorable.
The cassava plant is used mainly for food for human consumption. It can also be used as animal food. In many homes cassava provides a source of food and supplies energy. It can be made into flour for porridge of Ugali or roasted or boiled. Cassava leaves are also consumed as a green vegetable, which provides protein and vitamins A and B.
2. VARIETIES
Normally, there are two types of Cassava varieties: bitter and sweet cassava varieties.
Cassava is referred to as “sweet” it is less poisonous. Cassava contains large quantities of cyanide compounds, which must be processed out of the tubers before they can be safely eaten. The sweet variety of cassava has fewer of these compounds, and does not require as much processing. Bitter cassava is very similar in cultivation and general appearance to sweet cassava, but produces much higher quantities of cyanide compounds. Sweet cassava my contain as few as 40 parts per million, while bitter cassava varieties can range as high as 490 parts per million. Any quantity of cyanogens over 50 parts per million is considered to be hazardous. The presence of cyanide in cassava constitutes a clear threat to health, unless these compounds are removed before the cassava is consumed. Unprocessed cassava is toxic enough to cause death, but insufficiently processed cassava will also cause mortality over a period of time, especially when quality protein is absent from the local diet. There are several methods of removing the cyanide from cassava. Simple drying reduces the level of cyanide, though this may not be adequate to make it safe for consumption. Soaking the roots in water first, to leach out cyanide, produces a safer starch. So does fermenting the roots, either whole, shredded or in pieces, before drying. Roasting the tubers, or boiling them in multiple changes of water, will also reduce the cyanide content to manageable levels.
In Rwanda, we have a number of cassava varieties which are suffering from various diseases and pests.
Those varieties are described in the table below:
|
Crop: Cassava ( Manihot esculentum Crantz) |
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|
Name |
Code |
Released |
AEZ |
Taste |
Cycle (month) |
Yield (t/ha) |
Other Important Traits |
|
Gitamisi |
Eala 07 |
1975 |
LA, MA
|
Bitter |
18 – 24 |
40 |
Susceptible to CMD and Green mite, Dark brown stem, greenish red petiole, dark green leaves, dark brown external root color and white root pulp |
|
Rutanihisha |
Creolinha |
1985 |
LA, MA
|
Bitter |
15 – 18 |
40 - 45 |
Susceptible to CMD and Green mite, silver stem color, greenish red petiole, dark green leaves, cream external root color and white root pulp |
|
Gacyacyali |
Local |
1985 |
MA
|
Sweet |
12 – 15 |
25 |
Susceptible to CMD and Green mite, silver stem color, purple petiole, dark green leaves, dark brown external root color and white root pulp |
|
Gahene |
Local |
1988 |
LA, MA
|
Bitter |
12 – 15 |
30 |
Susceptible to CMD and Green mite, silver stem color, purple petiole, purple green leaves, cream external root color and white root pulp |
|
Bukalasa |
Local |
1985 |
LA, MA
|
Intermediate |
12 – 15 |
25 |
Susceptible to CMD and Green mite, silver stem color, greenish red petiole, dark green leaves, light brown external root color and white root pulp |
|
Iminayiro |
Local |
1985 |
LA, MA
|
Intermediate |
12 – 15 |
20 |
Susceptible to CMD and Green mite, dark brown stem color, yellowish green petiole, dark green leaves, light brown external root color and white root pulp |
|
Mavuta |
Local |
1988 |
LA, MA
|
Intermediate |
12 – 15 |
20 |
Susceptible to CMD and Green mite, silver stem color, purple petiole, dark green leaves, light brown external root color and cream root pulp |
|
Nyirakarasi |
Local |
1986 |
LA, MA
|
Bitter |
12 – 15 |
25 |
Susceptible to CMD and Green mite, golden stem color, purple petiole, purple green leaves, cream external root color and white root pulp |
|
Kiryumukwe |
Local |
1985 |
LA
|
Sweet |
10 – 15 |
25 |
Susceptible to CMD and Green mite, silver stem color, yellowish green petiole, dark green leaves, light brown external root color and white root pulp |
|
Maguruyinkware |
Local |
1985 |
LA, MA |
Intermediate |
12 - 15 |
20 -25 |
Susceptible to CMD and Green mite, grey stem color, greenish red petiole, dark green leaves, dark brown external root color and white root pulp |
|
Nyiramabuye |
Local |
1985 |
LA
|
Intermediate |
15 |
35 |
Susceptible to CMD and Green mite, green yellowish stem color, greenish red petiole, dark green leaves, dark brown external root color and white root pulp |
|
Imisurupiyo |
Local
|
1985 |
LA, MA
|
Intermediate |
15 |
20 |
Susceptible to CMD and Green mite, green yellowish stem color, red petiole, light green leaves, light brown external root color and white root pulp |
|
Ndamirabana |
TME 14 |
2006 |
LA, MA |
Sweet |
10 - 12 |
40 |
CMD resistant, Tolerance to green mite, silver stem color, purple petiole, light green leaves, cream external root color and white root pulp |
|
Cyizere |
I92/0057 |
2006 |
LA, MA |
Intermediate |
15 |
40 - 45 |
CMD resistant, Tolerance to green mite, green yellowish stem color, yellowish green petiole, light green leaves, dark brown external root color and white root pulp |
|
Mbakunga haze |
95/NA/00063 |
2006 |
LA, MA |
Bitter |
12 |
45 |
CMD tolerant, Tolerance to green mite, silver stem color, purple petiole, light green leaves, white external root color and white root pulp |
|
Mbagaru mbise |
MH95/0414 |
2006 |
LA, MA |
Intermediate |
12 – 15 |
30 – 35 |
CMD tolerant, Tolerance to green mite, golden stem color, purple petiole, light green leaves, light brown external root color and white root pulp |
|
Rwizihiza |
MM96/3920 |
2009 |
LA, MA |
Sweet |
12 |
30 - 35 |
CMD resistant, Tolerance to green mite, silver stem color, purple petiole, light green leaves, light brown external root color and white root pulp |
|
Seruruseke |
MM96/5280 |
2009 |
LA, MA |
Sweet |
12 |
25 - 30 |
CMD resistant, Tolerance to green mite, silver stem color, purple petiole, light green leaves, dark brown external root color and white root pulp |
|
Mavoka |
MM96/0287 |
2009 |
LA, MA |
Sweet |
10-12 |
35 -40 |
CMD resistant, Tolerance to green mite, grey stem color, greenish red petiole, dark green leaves, dark brown external root color and yellow root pulp |
|
Garukunsubire |
MM96/7204 |
2009 |
LA, MA |
Sweet |
12 |
30 - 35 |
CMD resistant, Tolerance to green mite, sylver stem color, greenish red petiole, dark green leaves, dark brown external root color and yellow root pulp |
AEZ = Agro Ecological Zone, LA = Low Altitude, MA = Middle Altitude
RWA
ENG