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Identification of Heterodera Species by Larval Length. Technique for Estimating the Constants determining the Length Variations Within a given Species

Published online by Cambridge University Press:  18 November 2009

D. W. Fenwick  and
M. T. Franklin
D. W. Fenwick
Affiliation:
Institute of Agricultural Parasitology, St. Albans.
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Extract

A complete investigation of the variations likely to occur in the lengths of larvae of Heterodera rostochiensis (for example) under all conditions would involve measuring larvae from a great number of varieties of potato grown in a great number of different localities, and also of larvae from tomatoes of different varieties grown under various conditions. The results obtained so far for this species of Heterodera make but a small contribution towards the mass of information which might be accumulated. Until such further data become available, certain conclusions have been drawn as to the best method of taking samples of larvae for measurement, but it must be remembered that these conclusions may need revision at a later date in the light of new information. According to our present knowledge it appears that the variety of potato on which a cyst has developed does not significantly affect the mean length of the larvae within, but that the mean length of the larvae from a single plant, irrespective of the variety, may differ significantly from that of larvae from another plant. It is also deduced that the variations in the mean lengths of the larvae from different cysts are greater than the variations within the individual cysts. From these facts it follows that if one wishes to estimate parameters for larval lengths of a population of H. rostochiensis larvae, a better estimate will be obtained if one takes a small number of larvae from each of a large number of cysts rather than the same total number of larvae from a small number of cysts. Similarly the cysts should have come from a large rather than a small number of plants, but apparently it is not necessary that the plants should be of as many varieties as possible, though this last assumption is based on information derived from only seven varieties of potato, all of them maincrop varieties, and it may need modification when larvae from other varieties have been examined.

Type
Research Papers
Information
Journal of Helminthology , Volume 20 , Issue 3-4 , December 1942 , pp. 67 - 114
Copyright
Copyright © Cambridge University Press 1942

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References

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