Developing dual-resistance cassava

Cassava root rot caused by CBSD. Photo by IITA.
Cassava root rot caused by CBSD. Photo by IITA.

This year, we moved closer to developing North Face Sale a few too mild properly and so forth!
cassava with dual resistance to Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD) – the most devastating diseases of the crop in Eastern and Central Africa and the greatest threats to the food security and livelihoods of over 200 million people.

In Uganda, we selected eight clones with resistance to CMD and CBSD and other farmer-preferred traits. These clones, which are the first ones with dual resistance suitable to the mid-altitude areas of the Great Lakes regions, were sent to the Kenya Plant Health Inspectorate Services for cleaning and multiplication in preparation for regional distribution to national partners. An additional 41 yellow-fleshed clones, also with dual resistance to CMD and CBSD, are undergoing advanced evaluation.

This is the fourth year of trials for dual-resistance cassava for mid-altitudes in Uganda. The trials are being conducted in Mukono and Namulonge, considered hot spots of CBSD and CMD in the country. The breeding work started with over 5000 true seeds of parents with tolerance to CBSD from Tanzania that were sent to Uganda for crossing with IITA varieties that are resistant to CMD.

Cassava grown from the Tanzanian seeds were repeatedly subjected to high disease pressure along with susceptible varieties for comparison. From each growing season, only 10 percent of the crop was selected for the next stage. After four growing seasons, the field has been narrowed down to eight very promising varieties.

Similar dual-resistance evaluation was carried out in Tanzania. Eight clones that have resistance to both CMD andeducate North Face Jacket Sale yourself on the way th much CBSD were deliberately subjected to the diseases by grafting them with infected plants. Five of these clones are being evaluated on-farm, while 11 clones with dual resistance and high starch content – a preferred trait by farmers – are also being evaluated.

Cassava that survives these tests, thereby producing a true dual-resistant variety, can then be used for further disease-resistance breeding in other countries in the Great Lakes region such as Rwanda, Kenya, and DR Congo. Throughout the selection process, farmers were actively engaged to ensure that the varieties meet their preferences such as cooking taste, texture, and yield.

A novel way to propagate yams

A rooted yam vine cutting, which would soon be ready for transplanting in the field. Photo by O Adebayo, IITA.
A rooted yam vine cutting, which would soon be ready for transplanting in the field. Photo by O Adebayo, IITA.

In the traditional method of growing yam, appearance dryfarmers set aside 25 to 30 percent of the harvested tubers as seeds for the next planting season. This makes the crop expensive to produce. It is also inefficient: the multiplication rate is only about 1:5-10, which pales in comparison, for instance, to cereals that have a propagation ratio of about 1:300.

To address these constraints, we developed an time her helps someone innovative yam propagation technique using vine cuttings. In this method, cuttings, usually one to two nodes with leaves are taken from the lateral branches of immature healthy-looking vines before tuber enlargement, and planted into soil with carbonized rice husks (CRH).

Once the cuttings formed roots and shoots, they are transplanted to nursery beds where they are nurtured for 150 days. During this time they will produce mini tubers, which are then used as the planting material for the next crop.

We are testing this novel technique in a number of farmers’ fields in Nigeria’s north central Niger state. The technology has been extensively featured in a number of broadcast and print media in Nigeria, Japan and the UK, and some countries in sub-Saharan Africa and Oceania.

By reducing the use of ware tubers as seeds, more yams are made available to farmers for food or for sale. The technique also promotes faster multiplication and better and more uniform crop quality by introducing a break in the cycle of nematode infestation often associated with regular use of field-grown tubers as planting material.

Another advantage of this technology is that the rooting medium, CRH, could be obtained by farmers cheaply, even for free.

Previously, we developed another propagation method together with the National Root Crops Research Institute of Nigeria based on mini-setts: yam tubers are cut up into 20-25 g pieces and used to produce planting material for ware tuber production.

Compared to using whole tubers, mini-setts enable faster multiplication and lesser amount of planting material needed. The use of vine cuttings further improves on this pace of multiplication and reduces the amount of need planting material even more. The technology could address the need for faster and wider distribution of disease-free improved varieties to meet rising demand.

The research is funded by the Japanese government, the Sasakawa Africa Association, Tokyo University of Agriculture, and the International Cooperation Center for Agricultural Education, Nagoya University, Japan.