Studies on the effect of subterranean clover red leaf virus and pea leaf roll virus on subterranean clover : A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science with Honours in the University of Canterbury [Lincoln College]

Abstract

The effects of viruses on plants do vary with environmental conditions particularly temperature, and also with biological factors such as the physiological status of the host.

In this study the symptoms of subterranean clover red leaf virus and pea leaf roll virus in subterranean clover (Trifolium subterreum L.) were observed under different environmental temperatures. Although these two diseases have been described from infected subterranean clovers growing in the field and in glasshouses, the environmental conditions were not clearly defined. As the infected plants acquired different physiological states with time and with defoliation, the effects of the viruses may possibly change. This possibility provided another aspect for study.

In all experiments quantitative measurements were employed to more accurately compare the effects of viruses on the host plants under the different conditions. Subterranean clover red leaf virus is a recent record for Australia and New Zealand, where Aulacorthum solani (Kltb.) has been shown to be a vector. In New Zealand, Macrosiphum euphorbae (Thos.) transmitted it on three occasions. Attempts were made therefore to confirm whether Macrosiphum euphorbae is a vector, and to compare its efficiency with that of Aulacorthum solani.