Research Papers: Internal Response of Resistant and Susceptible Potato Clones to Invasion by Potato Cyst Nematode Heterodera Rostochiensis

Abstract

A histological study was made to observe the early response of four resistant and four susceptible potato clones to invasion by race A of Heterodera rostochiensis Wollenweber. The resistant clones were hybrids between Solanum tuberosum ssp. tuberosum and four different sources of resistance: S. tuberosum ssp. andigena, S. spegazzinii, S. vernei, and S. multidissectum. The response of each resistant clone was compared to that of a related, but susceptible, clone. The response to invasion in all of the susceptible clones was the formation, through cell-wall dissolution, of a multinucleate syncytium, characterized by dense, granular cytoplasm. In all of the resistant clones, larvae were able to penetrate the roots and initiate the syncytium, but the amount of tissue included and the maintenance of the dense cytoplasm were limited by the resistant reaction. The mechanisms of resistance involved vacuolation of the syncytial cytoplasm, necrosis, and enclosure of the syncytium, but were not