PARASITIC NEMATODES ASSOCIATED WITH YAM (DISCOREA ROTUNDATA) AND MORPHOMETRIC CHARACTERIZATION OF SCUTELLONEMA BRADYS IN THE KRACHI NCHUMURU DISTRICT, GHANA

ABSTRACT

A dry rot of yam Dioscorea rotundata which attacks tubers in the field and in storage is currently threatening production of the crop in the Krachi Nchumuru District of the Volta Region No detailed investigation has been conducted therefore a study was carried out from October 2016 to May 2017 to assess the knowledge, perception and experiences of farmers in the District on the occurrence and management of the tuber dry rot disease, isolate, identify and assess plant parasitic nematode genera Krachi Nchumuru District in yam fields and stored yam tubers; determine variation within and among population of Scutellonema. bradys using morphological and morphometric characteristics. Questionnaire were developed and administered randomly to 50 farmers in 10 communities. The questionnaires covered demographic characteristics, land use intensity, farmers’ knowledge, perception and experience concerning occurrence of nematodes in yam fields and stored yam tubers, management and economic importance of yam nematodes. Yam rhizosphere soil samples were collected from 20 farms in the district for nematode extraction using Jenkins centrifugation method. Three stored yam tubers were also collected from the same farmers for nematode extraction using Baemanns extraction method. Morphometric measurements were carried out on populations of the yam nematode S. bradys using compound microscope attached to a computer. The survey revealed that farmers were aware of the tuber dry rot disease, but were however, ignorant about the causes and the spread of the disease, so planting materials were not treated before use. Twelve genera belonging to seven nematode families of order Rhabdida and Dorylaimida were identified in yam rhizosphere soils and nine genera in stored yam tubers. These were Scutellonema spp., Meloidogyne spp. Longidorus spp., Tylenchulus spp., Helicotylenchus spp., Ditylenchus spp., Heterodera spp., Pratylenchus spp., Rotylenchus spp., Appenlenchoides spp., Paratylenchus spp., and Bursaphelenchoides spp., The predominant nematodes Scutellonema spp., Meloidogyne spp. and Pratylenchus were present in both soil and yam tuber peels. There were low populations of other nematode genera. The most frequently detected genus was Scutellonema bradys (131) per 200cc of soil and (34086) in 10 gram tubers peels. Agglomerative hierarchical clustering (AHC) revealed 5 groups at a dismilarity of 90%, however sub groups formed at dissimilarity value of 5% Significant morphology variation is present in female S. bradys population.