Effect of low-temperature exposure of the wild potato Solanum commersonii Dun. and its genotypes on infection by the potato cyst nematode Globodera rostochiensis Woll

In continuation of research to study the effect of low temperature treatments on the ability of plants to act as hosts for the potato cyst nematode Globodera rostochiensis, the reproduction of the nematode on roots of the tuber-bearing wild potato species, Solanum commersonii, and its genotypes were investigated. Two genotypes were chosen, differing in freezing tolerance: freezing tolerant genotype 'FT 1020' and susceptible genotype 'FS 2022', and two plant treatments with low temperature (5 & DEG;C), applied prior to nematode infection. The temperature treatments differed in the duration of time the plants were subjected to low temperature, one treatment consisting of short-term daily temperature drops and the other of constant low temperature for 6 days. The infected S. commersonii plants had the highest mean and range of values of cyst numbers on their roots; the genotypes had similar cyst numbers on roots irrespective of their freezing tolerance level. Infection levels changed with the type of low temperature treatment. Plant treatment with short-term daily temperature drops consistently reduced the average cyst numbers and can be recommended for inducing S. commersonii resistance to G. rostochiensis; by contrast, low temperature for 6 days did not induce plant resistance. The genotype 'FT 1020' developed resistance after both low temperature treatments prior to infection, whereas the susceptible genotype 'FS 2022' became highly resistant only after the prolonged low temperature treatment.