Sweetpotato cultivars with improved storage root quality

Partners:
International Potato Center, Uganda and Kenya
Sugarcane Research Institute (Kibaha) Tanzania
HortiTengeru, Arusha, Tanzania
Sokoine University of Agriculture, Tanzania
Namulongwe Agriculture Research Organisation, Uganda
Agricultural and Animal Production Research Institute (SAARI), Uganda

Problem:
Breeding initiatives for sweetpotato are at an early stage compared to other staple crops.  Given the enormous genetic diversity of sweetpotato worldwide, and that breeding programmes of sweetpotato are relatively new, crop improvements are expected to be rapid.  This cluster of outputs arises from projects undertaken to examine germplasm available in East Africa, the potential for breeding for specific post-harvest/quality traits, and to identify strategies to facilitate effective cultivar selection.

Achievements:
Many of the project activities were focused towards understanding the physiological basis for differences among germplasm.  The resulting outputs can feed into breeding strategies at two levels: use of molecular markers (appropriate for international breeding programmes such as that at CIP);  identification of selection techniques suitable for National Programmes with more limited facilities.  Results from the studies

• Identification of farmer, trader and consumer criteria for sweetpotato cultivars in east Africa and strategies to incorporate them into selection protocols during breeding.
  
  
• Methods developed for the use of consumer tests and trained taste panels to assess sensory characteristics of sweetpotatoes.
  
  
• Breeding strategies to select for extension of shelf-life. Sweetpotato cultivars in East Africa have a wide range of shelf-life.  We established that a key factor affecting shelf-life is the efficiency by which storage roots heal wounds at low humidity.  Unfortunately high wound-healing efficiency is associated with lower dry matter content, although we do not know if this is a causative relationship.  Simple strategies, appropriate for use by national programmes, to assess wound-healing efficiency using tissue staining methods, or weight loss measurements have been developed.
  
• Increased understanding of the effect of root shape on susceptibility to damage during handling.
  
  
• Increased understanding of cultivar characteristics affecting long-term storability.
  
  
• Strategies to select for cultivars with canopy and rooting structures that confer reduced susceptibility to field infestation by insects, especially Cylas spp., including methods to assess appropriate root structures, and design of field trials with appropriate levels of insect pressure for efficient cultivar selection.