Investigations of Globodera pallida invasion and syncytia formation within roots of the susceptible potato cultivar Désirée and resistant species Solanum canasense

Abstract

Abstract Resistant responses to cyst nematode infection can take several different forms at a cytological level. We recently identified several new sources of resistance to Globodera pallida, including one derived from S. canasense Hawkes. Here we examine invasion, migration, syncytium formation and development of G. pallida on this source as compared with a susceptible cultivar (Désirée). Nematodes located roots of both resistant and susceptible plants, and invasion, migration and syncytium development occurred as expected on cv. Désirée roots. By contrast, second-stage juveniles (J2) invading S. canasense roots rarely induced a functional syncytium. The few syncytia that were induced were markedly smaller than those observed in cv. Désirée roots at the same timepoint, although they did contain the enlarged nuclei characteristic of 'normal' syncytia. No evidence for a necrotic response to the nematode or a developing syncytium was observed in S. canasense roots that did not support syncytia. Second-stage juveniles were observed at the surface of these roots suggesting that the nematodes were either unable to invade S. canasense roots or, as is the case for other resistance sources, that the J2 left the root soon after invasion. The possibility that glycoalkaloids play a role in the resistance of S. canasense to G. pallida is discussed.