Identification Of Nematodes And Morphological Characterisation Of Scutellonema Bradys Associated With Yam From Guinea Savanna And Transitional Rain Forest Ecological Zones Of Ghana

Abstract

Nematode parasitism is a major constraint and has resulted in major loses to both yam farmers and marketers in all yam producing areas in West Africa. Nematodes causes significant damage to yam tubers resulting in deformed, unsightly tubers or tubers with cracked and flaking skin that conceals the underlying rot. Farmers have over long periods been experiencing severe loses as result of nematode infestation both in the field and in storage. A study was therefore conducted from August, 2014 to May, 2015 to assess farmers’ knowledge and perception about nematode occurrence and its’ economic impact on their livelihoods; determine the different types, abundance and frequency of occurrence of plant-parasitic nematodes (PPNs) associated with yam; and determine morphological and morphometric variations among the yam nematode population. Assessment of farmers’ knowledge and perception was ascertained through questionnaires and interviews of 60 yam farmers in the Guinea savanna and Transitional rain forest agro-ecological zones (AEZs). The questionnaire focused on farmers’ demographic characteristics, their land use intensity, their knowledge, perception and experiences concerning occurrence, management and economic importance of nematodes associated with yam. The findings indicated that most farmers of yam aware of the physical damage that nematodes cause to yam tubers, but are completely unaware of what causes the damage, its spread and management. Nine genera of PPN belonging to six families of Tylenchida and Tryplonchida were identified from both the yam rhizosphere soils and yam tubers. They included; Meloidogyne spp., Pratylenchus spp., Scutellonema spp., Tylenchus spp., Trichodorus spp., Tylenchorhynchus spp., Rotylenchus spp., Hoplolaimus spp., and Helicotylenchus spp.The lesion nematode (Pratylenchus spp.), Scutellonema bradys and Meloidogyne spp. occurred with frequency of 100% in both yam rhizosphere soils and yam tubers in the field during the rainy season and yam tubers in storage during the dry season. Pratylenchus spp. was observed with the highest frequency of 22.9%, 46.3% and 22.3% for soil and yam tubers in the field during the rainy season and yam tubers in storage during the dry season respectively. Scutellonema spp. and Meloidogyne spp. had relative abundance of 18.8% and 18.2% for soils, 20.8% and 19.2% for yam tubers in storage respectively. The highest nematode population density in yam rhizosphere soils, yam tubers in the field and yam tubers in storage was recorded in Kanshegu in the Guinea savanna AEZ. Morphological descriptions and morphometric measurements are given for S. bradys female and male populations. Morphometric measurements from five populations in each AEZ using 14 female and male characters corresponded with previous descriptions of this species. Principal component analysis on eight variable that were identified as the most valuable characters in differentiating both male and female of S. bradys, could not distinctly separate the populations into groups. .