Changes in cell structure in roots of resistant potatoes parasitized by potato cyst-nematodes. I. Potatoes with resistance gene H1 derived from Solanum tuberosum ssp. andigena

Histological changes in roots of potato plants with the gene H₁, which confers resistance to the potato cyst-nematode Globedera rostochiensis pathotype Ro 1, are described for periods of 24 h to 10 days after invasion by second-stage juveniles of G. rostochiensis. The changes are compared with those which occur in roots of a susceptible cultivar. Experiments were carried out on potato roots growing from sprouting tuber pieces on water agar. Root cells surrounding the invading nematode undergo a hypersensitive-like response and become necrotic. Cell walls of inner cortical and stelar cells adjacent to the stylet of the invading nematode break down to form a syncytial complex but cells surrounding the syncytium become necrotic, presumably limiting movement of nutrients from plant to nematode. Ultrastructural changes of cells in the cortex and the stele are illustrated and discussed.