New cassava varieties to boost yields

Dar es Salaam. Cassava has transformed from a food security crop to a cash crop with industrial use in sectors such as brewery, pharmaceutical and confectionary.

The crop is one of Africa’s major staples, with the continent cultivating about 50 per cent of global production and is consumed by more than 600 million people in the developing world.

Tanzania is currently pushing to increase the production of cassava which has received a major boost after the release of four new varieties that are resistant to both cassava mosaic and cassava brown streak diseases.

African governments have been urged to seek genuine agricultural transformation to adopt the use of cassava in confectionaries and institute policies that would make the continent food secure and cut import bills on food.

International Institute of Tropical Agriculture (IITA) has released four cassava varieties with double resistance to the two deadliest diseases which have constituted some of the greatest threats to the production of the country’s second most important staple which also has immense potential as an industrial crop.

IITA plant breeder, Dr Edward Kanjuwho, who was involved in the research said it took ten years to come up with the varieties by crossing Tanzanian cassava varieties with those introduced from the Latin America Centre for Tropical Agriculture (CIAT, Colombia).

“The Tanzanian varieties were used as sources of tolerance to cassava brown streak disease (CBSD) and local adaptability,” he said.

The four varieties were developed through a collaborative research project between ARI Tanzania and two international research organisations: the International Centre for Tropical Agriculture (CIAT)) and International Institute of Tropical Agriculture (IITA).

The varieties released in 2012 by Tanzania were Makutupora, Dodoma, Mkumba and Pwani. They were evaluated across several sites and seasons in Dodoma, Coast, Mtwara and Lindi regions, hence their names.

Two of the four varieties released are meant for the coastal belt and the others are for semi-arid areas of central Tanzania. They can easily double the crop’s production potential as yields range from 23-51 tonnes/ha against the current average of 10 tonnes/ha.

The varieties were developed through conventional breeding and have been tested and pretested and have shown tolerance to the cassava brown streak disease. All have shown resistance to the cassava mosaic disease and have also given very good yields.

“Farmers have been eagerly awaiting these varieties as the two diseases have devastated the crop’s production for many years,” he said.

“Farmers were also involved in the selection process to ensure they met their preferences of cooking taste, texture, and time,” he added.

According to him, those from CIAT were used as sources of resistance to CMD and cassava green mites. All the released varieties are sweet in taste except Makutupora.

CBSD causes a dry rot in the roots rendering them inedible and was historically found only in the coastal low altitude areas of Eastern Africa and around Lake Malawi.

However, from 2004 the disease started spreading to mid-altitude areas. The disease can cause up to 80per cent yield reduction as it affects the roots and leaves, the most useful parts of the crop. It has drastically affected cassava production in North Western Tanzania and in the coastal belt.

Dr Victor Manyong, the director of the Eastern Africa Hub IITA, said they were working on seven major crops in East African including cassava, maize, yam, banana and plantain as well as soyabeans and cowpea.

Some of the diseases IITA is focusing on include cassava brown streak, cassava mosaic disease, and banana xanthomous wilt, banana bunchy top disease and soyabean rust.

“We are developing value chains of key staple crops and especially the highly perishable but hardy cassava, to ensure small holder farmers gain from their investment and their increased yields translate into real monetary benefits,” he said.

He noted that they were focusing on closing the yield gaps by addressing pests and diseases, developing sustainable production systems as well as deploying viable seed systems and addressing post- harvest losses.

Meanwhile, in Zanzibar, cassava is the second most important staple food after rice but ranks first in crop production area.

Cassava Brown Streak Disease (CBSD) was ranked by farmers as the major cassava production constraint. Unfortunately, the three most widely grown cultivars including Kibiriti Mweusi, Kibiriti Mwekundu and Boma are highly susceptible to CBSD, which causes farmers to lose 50 to 100 per cent of their harvest. As a result, many of them have abandoned cassava cultivation.

President Jakaya Kikwete has said in the past that many African countries are food-stressed and there is a decline in per capita food production.

“This signals an urgent need to revitalise agriculture research to scale up the application of science and technology as well as agro-processing and agribusiness,” he said.

He said that IITA research has made a tremendous impact in Sub Saharan Africa, especially on key tropical food crops such as cassava, banana, maize, soya beans, cowpeas and yam.

Research has enabled farmers to increase production of cassava by developing improved high quality disease resistant varieties.