BP Singh

210 Arju1l Lalwidth 0.02 rom), nematodes often go undetected in germplasm asthey contaminate soil or infest/infect plants, roots, tubers, bulbs,seeds etc. When infected plants and plant materials are collectedand moved, the nematodes travel with them. One of the worstparasitic nematodes (Ditylenchus dipsaci) have moved around theworld in this manner. Studies of the nematode movement andspread reveal that man is often the culprit, unintentionallycontributing to the distribution of these pests.N ow we shall discuss some of the commonly used techniquesto detect and diagnose the nematode infested plant material orseed and simple laboratory methods used to recover nematodesfrom infested soil or plant material.Nematode detection techniquesI. Detection of nematodes in the laboratory. Germplasm material received in the quarantine laboratory issubjected to detailed examination by employing various nematodedetection techniques depending upon the kind of plant material,size of the sample and availability of time. Some commonly usedtechniques are described below :a) Examination of the plant material: Examination of the plant·tissues under the microscope is the most conclusive and directevidence of nematode association with the infested plant material.This method is most suitable for nematodes producing distinctsymptoms on plants as their females become swollen.b) Observation of symptoms: Many species of plant parasiticnematodes cause stunting, yellowing, or wilting of their hostplants in the field. Nematode-plant interactions also result indevelopment of some specific signs of abnormal plant tissuegrowth (Table-2). It may be possible to find nematodes by directexamination when careful inspection of the plant/plant materialreveals-****Galls or swellings on roots, tubers, or rhizomesWhite, yellow, or brown pinhead size bodies adheringto rootsSwollen or malformed leaf, stem, or other tissueRoot lesions, or unusual root proliferation