Intra-specific morphometric variability of Tylenchorhynchus mashhoodi Siddiqi and Basir (1959) associated with groundnut, Arachis hypogaea L. in West Bengal

During a roving survey in major groundnut growing areas of the Hooghly district of West Bengal (India), forty three soil samples measuring 200cm3 were collected to study the morphometric variability of Tylenchorhynchus mashhoodi associated with groundnut, Arachis hypogaea L. The nematodes were extracted from the soil and then fixed in 4:1 formalin glacial acetic acid solution. These samples were processed following Seinhorst glycerol-ethanol method. The processed specimens were permanently mounted in pure anhydrous glycerol. Measurements on thirty two morphometric features of the nematode were taken under compound microscope (Olympus BX-51) with the help of ocular micrometer as well as with the image analyzing device ProgRes CT5 of Jenoptic Version 2.80. De Man indices for important morphometric features of the T. mashhoodi were also worked out. Drawings were made with the help of drawing tube of the compound binocular microscope. Detailed observation on morphometric variability revealed T. mashhoodi as the only dominant species under the genus Tylenchorhynchus. The present population of T. mashhoodi revealed high variability in body length among females than males. Number of lip annules and lateral lines were consistent between sexes. The stylet length (15-23μm) showed least variability among juveniles, moderate variability among males and high variability among females. Ratios like, a, b, c, c´ were found highly variable in females; while males showed least to moderate variability with regard to a and b ratios. V% in females, distance of median valve from stylet base and excretory pore from anterior end in males are least variable.