Resistant Cassava Types Still On

It is estimated that viruses are causing $60m (about Shs138b) in losses per, annum out of the revenue contribution the government is supposed to realise from the production of cassava.

That is why Ugandan scientists are investigating ways to come up with cassava varieties resistant to cassava mosaic virus and cassava brown streak. The team still has a long way to go because they aim at eradicating four types of viruses that are destroying the crop from farmer's fields in cassava growing countries throughout Africa.

Crop scientists at the National Agricultural Crop Resources Research Institute in Namulonge are currently conducting research using both the conventional and biotechnology method in a bid to come up with cassava varieties that are resistant to virus.

The research work that has been going on since 2005 is an initiative of a United State research based centre, the Donald Danforth Plant Science Centre in collaboration with USAID and Uganda government.

The chief investigator of the project Dr Titus Alicai said in 2005 the National Biosafety committee housed at Uganda National Council for Science and Technology gave his team a permit to proceed with the research where the team undertook to study the general behaviour of the virus before embarking into real research work.

The team in the 1990s did conduct research in a bid to eradicate cassava mosaicvirus which was a major problem that time. However later in the year 2000, scientists discovered another deadly virus, the cassava mosaic Virus.

The two viruses have since been identified having two types of viruses each namely, Cassava Brown Streak Virus (CBSV), Uganda Cassava Brown Streak Virus (UCBSV) which was first spotted in Uganda, African Cassava Mosaic Virus (ACMV) and East African Cassava Mosaic Virus (EACMV).

The ongoing research is aimed at finding solutions to curb all types of viruses.

According to Dr Alicai, it is estimated that these viruses are causing $60m in losses per, annum out of the revenue contribution the government is supposed to realise from the production of cassava.

Further estimates show that farmers especially those in the districts of Mukono and Luwero are experiencing 100 per cent loss as a result of cassava brown streak epidemic.

As the team was studying the behaviour of the virus, they got an alternative method of breeding varieties using conventional breeding. Conventional breeding is a means of developing new plant varieties by selecting the best varieties with the existing gene in plant species. Here, scientists transfer the genes by crossing the female part of the plant to the male part.

Conventional breeding employs processes that occur in nature, such as sexual and asexual reproduction. The product of conventional breeding emphasises certain characteristics which are not new to the plant

As far as the research at Namulonge is concerned, the team obtained resistant varieties from Tanzania and Colombia, and crossed them to some screened local varieties here. The breeding process here involves cutting part of the male flower from the foreign cassava and crossing it to the female flower of the local variety in order to come up with a new variety.

The team also screened about 1,000 local varieties and conducted the same crossing exercise. So far the team has identified six varieties that seem to be resistant to the viruses but are being evaluated at selected farmer's fields throughout the country to establish stability of yields and tolerance to the virus.

Once the evaluation process is done, the team will collect the data and apply to the Variety Evaluation Committee at the ministry of Agriculture to give them a go ahead to release these varieties to the farmers.

Dr Alicai is optimistic that his team will release the six varieties to farmers by next year. However the research team is not convinced that the conventional breeding method will solve the problem of eradicating the virus the reason they are conducting research using the Biotechnology method. What is different here is that the resistant genes are introduced to the local varieties in the laboratory.

Last year the scientists were conducting research to establish resistance against the EACMV. The work that was concluded in September showed some good results but for purposes of validating the exercise they are repeating the research work.

According to Dr Alicai, the next exercise is to test the same genes against the rest of the viruses. Later the team will merge the exercise against all the viruses in order to come up with cassava varieties that are resistant to all the four types of viruses.

The team hopes that by the year 2015 they would have identified the best gene that is resistant to all the viruses. The challenge of using the biotechnology method according to Dr Alicai is that since the work is done in the laboratory, there is need for reagents that are used to contact the research to always be in place but sometimes they are not available because sometimes the suppliers take long to supply them.