The Significance of the Necrotic Phloem Reaction in the Potato to The Leaf-Roll Virus

Abstract

SummaryA modified technique which has facilitated the detection of phloem necrosis in leaf-roll-infected potato plants is described. Placed on a quantitative basis, the necrotic reaction has proved valuable in the estimation of leaf-roll severity in varieties and hybrids. Quantitatively, phloem necrosis has been shown to be tl varietal character which can be influenced by nutritional and environmental conditions. Among varieties and hybrids, a range of necrotic reactions in the phloem from mild to very severe was found, and these reactions were correlated with external symptoms. Severe reactors show a progressive decrease in the amount of phloem necrosis from the stem base to the tip. It is probable that a severe physiological reaction to leaf roll has a well-defined genetic basis, so that the development of hybrids hypersensitive to this virus is possible. This provides a new approach to the problem of leaf-roll resistance in the potato.

Mechanism of strong resistance to Potato leafroll virus infection in a clone of potato (Solanum tuberosum)

“…In a series of tests, aphids were allowed to acquire PLRV from secondarily infected G8107(1) plants (where they multiplied at a normal rate), prior to placing them on receptor plants of P. floridana and N. clevelandii. Hutton (1949) reported severe phloem necrosis associated with PLRV infection in Bismark, and Wilson & Jones (1992) suggested that this might be a resistance mechanism. Control tests with Maris Piper source plants showed that aphids readily infected the receptor plants and every plant became infected.…”

“…Bismark with primary PLRV infection were healthy. Hutton (1949) reported severe phloem necrosis associated with PLRV infection in Bismark, and Wilson & Jones (1992) suggested that this might be a resistance mechanism. A similar case was reported by Golinowski et al (1987) in cv.…”