Role of Fungal Rots in Post-harvest Storage Losses in Some Nigerian Varieties of Dioscorea Species

Aims: To study storage rots in yam varieties cultivated in South East Nigeria and to determine under conditions of experimental storage, the influence of fungal rot on their post harvest storage losses.
Place and Duration of Study: Laboratories, Department of Applied Microbiology & Brewing, Nnamdi Azikiwe University, Awka, Nigeria between January 2012 and July 2013.
Methodology: Five yam varieties; Dioscorea dumentorum, two varieties each of D. alata and D. rotundata, obtained immediately after harvest were stored in an experimental barn (30ºC and 95% RH) and examined at intervals for storage rots. Fungal causative agents of rots were isolated and identified using the partial ITS rDNA sequencing analysis and a BLAST search using the GenBank sequence database. Post harvest storage losses in terms of weight loss and reduction of shelf life among the varieties were determined.
Results: All varieties of yams studied suffered fungal rots, predominantly, dry rots during storage. Seven distinct fungal isolates, which caused these rots, were fully characterized. The species were Aspergillus tamari, Fusarium solani, Lasiodiplodia theobromae, Aspergillus niger, Mucor circinelloides, Aspergillus flavus and Aspergillus sp. In all the yams, storage rots reduced shelf life and aggravated weight loss. Post harvest storage losses varied among the different varieties of yams.
Conclusion: The varieties of yams studied suffer rots from various fungi, which are similar to those reported in other parts of the world. Severity of post harvest losses resulting from fungal rots varies among different varieties of yams. This should be taken into consideration in the development of storage techniques.