Cultivar and endophyte effects on a root aphid, Aploneura lentisci, in perennial ryegrass

Abstract

In a pot trial, fungal endophytes (Neotyphodium spp.) with different alkaloid profiles were investigated for their effects on numbers of a root aphid (Aploneura lentisci) in perennial ryegrass. Some endophytes were also tested in different cultivars (Nui, Samson and Impact). Two endophytes, AR37 and AR6, strongly suppressed root aphid numbers. Wild-type had fewer aphids than endophyte-free plants and AR1. Endophytes producing peramine only (AR1, AR12, AR22) and an endophyte producing peramine and lolitrem B (AR23) did not differ from endophyte-free. There were no cultivar by endophyte interactions but cultivar affected the strength of aphid response to Wild-type. Comparisons of alkaloid profiles suggest that ergovaline (in Wild-type and AR6) and epoxy-janthitrems (in AR37) may affect root aphids whereas peramine and lolitrem B do not. Differences in herbage dry weight of plants and a significant relationship between herbage dry weight and root aphid numbers indicated this aphid reduces the growth rate of plants.