Evaluation of extraction and separation techniques for recovery of cysts of Heterodera zeae Rajan, Swarup Gopal Division of Nematology, Indian Agricultural Research Institute, New Delhi-12. Presented at Nematology Symposium held at Coimbatore, India in February, 1981 Abstract Extraction and separation of cysts. of Heterodera species for experimental investigations are very laborious and time consuming processes. A number of techniques have been suggested time and again by various workers but so far there has not been any attempt to evaluate the comparative efficacy of these techniques. Also the consequent effect, if any, on the emergence of larvae from cysts as a result of handling by different techniques and which should be an important consideration in adopting a technique for a particular species has not been generally studied. This is particularly true for the Indian conditions. Sieving followed by mechanical picking of the cysts is the generally accepted procedure for collection of cyst inoculum required for experimental purposes. However, this is a very laborious process and also tiresome. Therefore, some of the already known techniques of extraction and separation of cysts of Heterodera species have been evaluated in respect of 2 important cyst nematode species, Heterodera avenae and Heterodera zeae. The present paper is confined to the results obtained with respect to H. zeae. For extraction of cysts, use of ZnSO4 (sp. gr. 1.32) with flask was comparable to fenwick can and modified fenwick can but was inferior to sieving alone. Use of NaCl, MgSO4 and sugar was not effective. A sample size of 200 ml was found to be significantly better sample size than 50 and 100 mL However, for not culture soils, there was no difference between 50, 100 and 200 ml sample size. Soil type was found to be an important consideration in the selection of the techniques to be used for extraction. For loamy sand soil dry sieving-frubbing was better than other methods while in the case of sandy loam soil as well as pot culture soil, sieving, fenwick can and modified fenwick can were equally good. After extraction, quick separation of cysts from debri was obtained by acetone+carbon tetrachloride (drying of cyst+debri at 25°C), ethanol (drying of cyst + debri at 15°C). However, these chemicals depressed the hatching of the cysts but other inorganic chemicals like NaCl (sp. gr. 1.19) and MgSO4 (sp. gr. 1.22) which were significantly inferior to acetone + carbon tetrachloride and ethanol for separation of cysts from debri stimulated hatching of the recovered cysts. Top |