BP Singh

Detection Techniques for Plant Parasitic Nematodes 213If any of these symptoms are observed on the plants Iplanting materials, dissection can then be undertaken to confirmthe nematode presence.c) Dissection techniques: For examination of nematode infectedplant tissue, following things are required: stereoscopic dissectingmicroscope, petri dishes or Syracuse dishes, fluorescent illuminator,dissecting needles, fine-bladed knife, scalpel or razor blade. Cutaffected roots, b~bs, leaves or buds into small pieces. Place a fewpieces in a petri dish or Syracuse dish containing water and notethe presence of nematodes under microscope by cutting open thetissues with dissecting needles. If any nematodes are found, pickthem up and process for identification.True seeds infected with nematodes do not show any clearcut symptoms and, therefore, difficult to separate from healthyones. However, in some cases (paddy, onion, peanut, foxtail millet,fababean, alfalfa) infected seeds are discoloured, shriveled andlighter in weight. Nematodes from such seeds are recovered bysoaking the seeds in water at 25 DC for about 24 hrs. and observingunder stereoscopic microscope after crushing the seeds or removingthe seed coat. It is always better to examine as many seeds aspossible. Important nematode species reported as seed borne orcarried on seed are listed in Table-3.d) Staining techniques: It is often difficult to detect nematodesin plant tissues as they are colourless or translucent. Staining issimple and helps in differentiating nematodes from plant tissues(specially roots). The most common staining technique used forroot samples is to colour the tissue with acid, fuchsin dissolved inlactophenol or lactoglycerol (0.05%), then destain it with clearlactophenolllactoglycerol. The nematodes retain red stain morestrongly than does the root tissue.e) Soil examination: Some plant parasitic nematodes (cystforming and ectoparasitic ones) can spread with small amounts ofsoil mixed with seeds or adhered to roots. To detect the presenceof cysts in soil, 5-10 gm of soil (removed from seeds by sieving orhand picking the clods) is mixed with 20 m1 water and directlyobserved under stereoscopic microscope at 15 to 50 X magnification.Brown to dark brown cysts can be seen if the soil is infested. Collectall cysts by a forecep or brush and send for identification afterproper labeling. ,