Towards increasing and sustaining production of yam for food security and improved livelihoods in Uganda.
Yam (Dioscorea spp.) plays an important role in food security and is increasingly gaining importance as a source of income for smaller holder farmers in Uganda. However, the crop has not been given due attention in the national research and development (R&D) agenda in Uganda and nearly falls in the class of ‘neglected or orphaned crop’. The objective of this paper is to generate insights into the importance of yam in Uganda in order to increase production and improve food security. Primary and secondary information from studies conducted in Uganda show that the most popular yam types are the yellow varieties. Challenges include limited availability of yam, seed rendering it very expensive, high cost of staking materials and limited knowledge in yam agronomy and utilisation.
Nematode distribution and damage to yam in central and eastern Uganda
Yams (Dioscorea spp.) are food crops of growing significance in sub Saharan Africa. Unfortunately, nematodes are major pests to their production. A study was undertaken in major yam growing areas of Uganda to investigate the association of plant parasitic nematodes with damage symptoms. Nematodes were assessed from tubers, roots and surrounding soil for seven cultivars belonging to Dioscorea alata, D. bulbisiana, D. burkilliana and D. cayenensis at harvest. Pratylenchus sudanensis was found in the greatest density and was followed by Meloidogyne spp. Higher densities of both nematodes were observed in the tubers rather than roots. Although symptoms of cracking and galling were relatively low, P. sudanensis incidence was strongly associated with cracking and Meloidogyne spp. with galling. Pratylenchus sudanensis and Meloidogyne spp. incidence their associated damage were, however, negatively correlated, suggesting inter-species competition. Principal components analysis of data suggested that differences in susceptibility to P. sudanensis occur between yam cultivars and species.
Plant-parasitic nematodes associated with root and tuber crops in Uganda
In a nematode survey of eight commonly grown root and tuber crops (cassava, sweet potato, potato, yam, tannia, taro, carrot and turmeric) from 430 fields in Uganda, 69 species of plant-parasitic nematodes representing 28 genera were extracted from soil and roots. About twice as many nematode species were recovered from soil (64) as from roots (36), while 32 species were found only in soil and four species only in roots, usually in mixed populations. lIgMeloidogynel/Ig spp. (root-knot nematodes) were the most frequently recovered across crops, with the major species ( M. arenaria, M. hapla, M. incognital/Ig and M. javanica ) observed on cassava. Some nematodes were recovered only from specific crops. Sweet potato yielded the greatest diversity of species (55 species in 25 genera), followed by cassava (40 species in 19 genera) and yam, which was sampled principally in the northern and eastern regions of Uganda (39 species in 14 genera). Results of the study provide baseline information for more detailed local population 
studies and nematode pathogenicity evaluations on important root and tuber crops.