Cassava production in africa is devasted by different viruses, e.g. african cassava mosiac virus, east african cassav amosiac virus. I was quite shocked to see crop destruction caused by viral attack. Cassava crop production needs to be enhanced for growing under abitic stress condition. We had a project on cassava in Ghana to develop virus resistant cassava by induced mutations. One mutant variety was developed that showed virus resistance, that later lost this character. Another aspect is to improve starch quality for industrial use and cooking quality

I remember sending Dr. Legg to Ghhana for cassava project evaluation as an IAEA specialist, who advised to take care of virus problem in Ghana for cassava production

I recall travelling to Ghana as part of the mutation breeding work that was being done by BNARI and KNUST some time ago. They had a variety called Tek Bankye that had a high starch content but unfortunately was relatively susceptible to cassava mosaic disease. I have to admit, that I was not too convinced by the potential for the mutation breeding approach for cassava. I know there have been similar efforts elsewhere (Zambia I know was one other), but the potential value of conventionally bred material seems overall much greater than that from this source. However, much effort is now going into the production of transgenic varieties, transformed for resistance to both cassava mosaic geminiviruses as well as cassava brown streak viruses. The latter are particularly problematic in East and Central Africa. The big question here, however, is one of regulatory and consumer acceptance, and it is still unclear whether it will be possible to get these into farmers' fields 'at scale' within the next 5-10 years. I am aware that average yields of cassava are MUCH greater in South Asia and Thailand, and wonder what the secret has been to getting these kinds of yields in these areas. If anyone has any thoughts on that, it would be good to hear them.

You are right, induced mutations did not work in cassava and also we tried in papaya, and failed to get the results. It looks transgenic research may be an ideal approach, which may raise ethical questions. Of course classical breeding, as suggested Prof. Wang, would cerainly be the best approach. Dr. Nasse Nabib, Brazil has been working on cassava breeding and has large collection of germplasm. I am not quite sure if he has developed cassava virus resistant lines. recently ha has been working on grfating method for cassava improvement, however, I find this work doubtful for trait stability

No secret for higher yield of a particular crop. Agromony and genetics plus hard work. Agronomy will deliver results quickly by looking at fertilizers, plant protection etc.

Thanks for this important and food-security-relevant question. While IITA Ibadan and others have done a lot for breeding against virus-diseases and palatabilty, more and more areas get under cassava again after being lost for decades. The theoretical and partly practically high yield-potential of cassava is one of THE challenges for the years to come, also considering the strong move of agronomy towards improving the availability of industrial raw-materials as well as energy-crops.....in addition to the highest priority FOOD and food-security. In crop-husbandry matters I see enormous further potentials in a) planting cassava in contour-line-oriented landscaping for better rain-harvesting; b) planting cassava in alley-systems, mixed cropping, esp. with leguminous soil-cover and Nitrogen-suppliers; c) Using all sorts of organic mulching-materials for weed-suppression, water-retention and nutrient-supply. Note: mulching can reduce water-loss by evaporation in the range of up to 50% !; d) Integrating cassava into perma-culture systems which were the predominant land-use manner before "man-made negativ impacts"; e) Allowing commercial large-scale mechanized cassava-plantations only with a wise eco-system, socio-system and minimum crop-rotation or alley-cropping-systems. e) Establishing a permanent system of variety-testing in farmers' fields and not only behind 3-m-high research-station-fences.