Collection, genotyping and virus elimination of cassava landraces from Tanzania and documentation of farmer knowledge

Open Access Journal; Published online: 17 Aug 2021Cassava (Manihot esculenta Crantz.) has been a vital staple and food security crop in Tanzania for several centuries, and it is likely that its resilience will play a key role in mitigating livelihood insecurities arising from climate change. The sector is dominated by smallholder farmers growing traditional landrace varieties. A recent surge in virus diseases and awareness in the commercial potential of cassava has prompted a drive to disseminate improved varieties in the country. These factors however also threaten the existence of landraces and associated farmer knowledge. It is important that the landraces are conserved and utilized as the adaptive gene complexes they harbor can drive breeding for improved varieties that meet agro-ecological adaptation as well as farmer and consumer needs, thereby improving adoption rates. Here we report on cassava germplasm collection missions and documentation of farmer knowledge in seven zones of Tanzania. A total of 277 unique landraces are identified through high-density genotyping. The large number of landraces is attributable to a mixed clonal/sexual reproductive system in which the soil seed bank and incorporation of seedlings plays an important role. A striking divergence in genetic relationships between the coastal regions and western regions is evident and explained by (i) independent introductions of cassava into the country, (ii) adaptation to prevailing agro-ecological conditions and (iii) farmer selections according to the intended use or market demands. The main uses of cassava with different product profiles are evident, including fresh consumption, flour production, dual purpose incorporating both these uses and longer-term food security. Each of these products have different trait requirements. Individual landraces were not widely distributed across the country with limited farmer-to-farmer diffusion with implications for seed systems

Cassava production improvement through staggered planting for industrial processing and utilization in eastern and southern zones of Tanzania

IITA supervisor: Dr. Pypers, P. IITA supervisor: Dr. Nzokwe, V.N.E.An experiment was conducted with the aim of identifying suitable cassava scheduled planting, harvesting and varietal performance in order to optimize growth, development, yield and quality of cassava during the 2017/18 - 2018/19 cropping season. The experiment was conducted at Naliendele, Nachingwea and Ilonga TARI Research Centres in Tanzania. The experiment was laid out as split-split plot in a randomized complete block design with variety being main factor, harvesting time as sub plot and planting schedules as sub-sub plot with four replications at each site.Factor A with three levels which were Kiroba, Mkuranga 1 and Chereko variety. The sub plot also with three levels that were harvesting at eight, ten and 12 months after planting while factor C also with three levels of planting times in November/December, January and March/April. The total root yield increased significantly from first to third planting and harvesting times respectively. Kiroba variety planted in November/December and then harvested at twelve months after planting (MAP) gave highest total fresh root yield 27 tones per hactre (t/ha) in the Southern zone followed by Eastern zone with Kiroba variety planted in November/December and March/April yielded highest total root (22t/ha) when harvested at 12MAP. Based on cassava dry matter content; the study shows that: highest dry matter content was obtained when Mkuranga 1 variety planted in November/December and harvested at 12MAP gave 40% followed by Kiroba variety planted in November/December and harvested after 12MAP had 39% in Southern zone. Also the study found that; cassava starch content was highest (23%) in Southern zone when Mkuranga 1 variety planted during November/December and harvested at 12MAP before the onset of rainfall. The current results recommend that practising planting cassava in November/December for fresh cassava utilization and adopt the late planting in March/April can be advantageous in small scale and commercial producers