IDENTIFICATION OF NEMATODES AND MORPHOLOGICAL CHARACTERIZATION OF MELOIDOGYNE INCOGNITA ASSOCIATED WITH SOLANUM LYCOPERSICUM L. IN THE ASHANTI, BRONG AHAFO AND UPPER EAST REGIONS OF GHANA

ABSTRACT

Production of tomato in Ghana is threatened by plant parasitic nematodes. Identification of the types,  distribution  and  population  densities  of  these  parasites  is  indispensable  for the design  and implementation of a proper nematode management practice.  A study was conducted to: assess farmers' knowledge and perception on plant parasitic nematode occurrence and management on their farms in  nine communities of Ashanti, Brong Ahafo and Upper East Regions of Ghana; Identify genera of plant parasitic nematodes associated with tomato production in the communities; determine the relative abundance of identified nematodes from tomato roots and rhizosphere soil; morphologically characterize field populations of Meloidogyne incognita; compare morphometric features of the parasite reported to that in literature and determine which features account for total morphological variations of the populations through principal component analysis (PCA). Semi-structured questionnaires were designed and administered to fifty four randomly selected farmers from nine communities namely Afrancho, Akumadan, Asuosu, Tono, Vea, Pwalugu, Tachimentia, Tanoso and Tuobodom. Data collected in the questionnaire were subjected to descriptive statistics. Composite rhizosphere soil and tomato roots were collected from two randomly selected farms in each of the nine communities and nematode extracted from them, identified and enumerated. Morphometric characters were measured on adult males and second stage juveniles of Meloidogyne incognita. Principal component analysis was performed on the measurements to determine the morphological features accounting for the total variation of measured characters. The findings indicated that farmers were ignorant of plant parasitic nematodes as pathogens of their tomato crops although they experienced symptoms of nematode infestation on their tomato fields. Most farmers (63%) continually cropped their land to tomato for 4-7 years without any form of rotation and all the farmers interviewed (100%) applied only inorganic fertilizer to their crops. Eight genera of plant parasitic nematodes were identified;  (Helicotylenchus  spp.,  Hoplolaimus  spp.,  Meloidogyne  spp.,  Pratylenchus  spp., Rotylenchuluss  spp., Scutellonema  spp., Tylenchus  spp. and Xiphinema spp.) from rhizosphere soils and four from roots of tomato plants (Meloidogyne spp., Pratylenchus spp., Rotylenchulus spp. and Scutellonema  spp.) at varying densities.  Meloidogyne spp. was found to be the most abundant genus (37.41%, 69.27%) in soil (200 cm3) and roots (10 g) respectively. Meloidogyne incognita was the most abundant Meloidogyne species (59% of males and 75% of Juveniles) based on head morphology of adult males and tail shapes of second stage juveniles, Average morphometric measurements of adult males were: Body length =1131.28 µm, Greatest body width= 34.45 µm, DEGO= 3.69 µm, Gubernaculum length = 10.19 µm, Stylet length= 25.45 µm, Tail length =11.15 µm and Spicule length= 29.26 µm and second stage juveniles were: Body length = 405.54 µm, Greatest body width = 15.16 µm, Stylet length = 12.35 µm and Tail length = 46.67 µm. These measurements were generally larger than those reported in the literature for M. incognita. PCA indicated that total body length and greatest body width were important characters in separating adult males of M. incognita from four communities while tail length, body length and stylet length were important in separating J2 of M. incognita from the nine communities.