Variation in Cultivar Resistance to the Potato Cyst Nematode Globodera pallida
Introduction
The white cyst nematode, Globodera pallida, is a serious pest of potato crops. Partial resistance is an important cultivar characteristic, and is assessed for National List purposes. Field infestations in Britain are considered to belong to the Pa2-3 pathotype. Previously two pathotypes Pa2 and Pa3 had been described but subsequently this designation was considered inappropriate.
The earlier distinction was, however, based on observed genotype x cultivar interactions. Moreover the putative differential (VTn)262.33.3 had been used by breeders as a source of quantitative resistance to G. pallida. There is little information on the distribution of potentially different PCN populations in the UK, or on the extent to which they interaction with commercial potato cultivars.
Results
Analysis of variance for the cyst multiplication rates transformed to natural logarithms showed significant differences for populations and highly significant differences for cultivars. The interactions between cultivars and populations were also highly significant.
Cultivar ranking order from the mean of 10 PCN populations is clearly different from that seen in current NL information. Though most of the cultivars with susceptible ratings at NL showed high multiplication rates with all 10 populations, cv Celine and Valor appeared more resistant than the NL rating would suggest. Cv Nadine, which has some partial resistance, was more susceptible to some populations than the NL susceptible controls cv Desiree and cv M Piper.
Discussion
As the cultivars were selected for their differing levels of partial resistance to G. pallida pathotype 2/3, the nematode’s multiplication rate was expected to vary among cultivars, and these differences were clear. However, origin of a population also had a significant effect on multiplication rates. Variation between populations for multiplication on individual cultivars was significant, and occurred to the extent that ratings from National List testing may not adequately reflect what might occur in some locations.
The financial support of DEFRA is gratefully acknowledged.
Analysis of variance for the cyst multiplication rates transformed to natural logarithms showed significant differences for populations and highly significant differences for cultivars. The interactions between cultivars and populations were also highly significant.
Cultivar ranking order from the mean of 10 PCN populations is clearly different from that seen in current NL information. Though most of the cultivars with susceptible ratings at NL showed high multiplication rates with all 10 populations, cv Celine and Valor appeared more resistant than the NL rating would suggest. Cv Nadine, which has some partial resistance, was more susceptible to some populations than the NL susceptible controls cv Desiree and cv M Piper.
Discussion
As the cultivars were selected for their differing levels of partial resistance to G. pallida pathotype 2/3, the nematode’s multiplication rate was expected to vary among cultivars, and these differences were clear. However, origin of a population also had a significant effect on multiplication rates. Variation between populations for multiplication on individual cultivars was significant, and occurred to the extent that ratings from National List testing may not adequately reflect what might occur in some locations.
The financial support of DEFRA is gratefully acknowledged.