Potato seed tuber physiological age and tolerance of attack by the potato cyst nematode Globodera pallida
Seed tubers conditioned to 0, 200 or 400 day-degrees above 4t were grown in land infested with Q. pallida. Plants from 400 day-degree seed emerged earlier, had larger canopies and greater dry weights early in the growing season than plants from 0 day-degree seed. However, physiological ageing reduced peak percentage ground cover and advanced crop senescence so that similar quantities of solar radiation were intercepted over the whole growth period. Overall, total and ware yields were not affected much by seed tuber physiological age. The partially resistant cultivars tested were more tolerant than the non resistant cultivars but tolerance was not usually affected by physiological age of seed tubers. The effects of nematicide treatment, initial Q. pallida population density, cultivar maturity class, cultivar resistance status and planting date on nematode multiplication, plant growth and tolerance of attack by Q. pallida are discussed. Using data from a variable temperature water bath experiment, probability and regression analysis estimated mean basal temperatures for the development of Q. pallida and Q. rostochiensis at 2.5 and S.rCi least variance analysis estimates were 3.5 and 4.rC respectively. Approximately 200 day-degrees above 3.5 and 4.rC were required from the inoculation of JJ2 of Q. pallida and G. rostochiensis to the peak numbers of JJ5 found in potato roots. From a range of chemicals tested for their ability to release antigen from Q. pallida cysts, sodium hypochlorite was found to be the most effective. Released antigen was detected using polyclonal antisera and monoclonal antibodies in an ELISA test. The potential for the development of an ELISA based diagnosis test for PCN using species-specific antibodies is discussed.