This presentation is described by the following abstract

¹International Potato Center (CIP), Tanzania, C/o Lake Zone Agricultural Research and Development Institute (LZARDI), P.O Box 1433, Mwanza, Tanzania.

²CIP-SSA, P.O. Box 25171-00603, Nairobi, Kenya.

³CIP-Lima, Apartado 1558, Lima 12, Peru.

⁴Lake Zone Agricultural Research and Development Institute (LZARDI), P.O Box 1433, Mwanza, Tanzania.

⁵Mikocheni Agricultural Research Institute, P.O. Box 6226, Dar Es Salaam, Tanzania.

*Corresponding author, email: K.Ogero@cgiar.org

Single and complex virus infections are a major constraint to sweetpotato production in Tanzania. This is exacerbated by the common practice of farmer-farmer exchange of planting materials whose quality is often unknown. Farmers’ access to virus-free planting materials sourced from virus-indexed tissue culture plantlets may improve the situation. However, it is important to empower farmers with skills and technologies that will help in protecting quality planting materials from attack by virus vectors. We are validating the use of low cost insect-proof net tunnels, managed by farmer multipliers, to protect basic seed stock. As part of this we are assessing the degeneration rate of vines multiplied in the net tunnels compared to those multiplied in open beds. This research is being conducted over three years, on two varieties in both high and low virus pressure areas. Vines are harvested every 60–80 days, vine yields calculated, and planted out for subsequent assessment of root yield. Leaf samples are collected for virus testing using PCR. A visual assessment of virus symptoms and whitefly count on the surrounding crops is conducted for each field generation. Results of visual inspections conducted in the first season indicate that the materials show no virus symptoms. Additionally, materials at the tissue culture laboratory tested negative for sweetpotato chlorotic stunt and sweetpotato feathery mottle viruses whose synergistic interaction causes the sweetpotato virus disease. Results from the first four rounds of harvesting showed a consistent decrease in the total number of vines at both sites and for both varieties. The number of three-node cuttings showed a different pattern; reducing during the first rattoon, going up during the second rattoon and decreasing again during the third one. This study will help inform the appropriate number of multiplication cycles the net tunnel technology can be relied upon before replacing the material.