Mixing barley cultivars affects aphid host plant acceptance in field experiments

Abstract

Four barley varieties with no significant difference in aphid acceptance were sown in pure stands and in pairwise combinations with varieties side by side in separate rows. Settling tests were done in situ in the field plots with apterae of Rhopalosiphum padi (L.) (Homoptera:Aphididae) and showed that aphid acceptance was changed in some combinations of cultivars. In a laboratory test, in which plants of one cultivar were exposed to air from the other cultivars, aphid acceptance was significantly reduced in three of the four cultivars when treated with air from certain other cultivars. Two of these three cultivars showed the same reduction under field conditions. This supports the hypothesis that plant/plant communication may release responses in neighbouring plants that change aphid host plant acceptance. The results also show that this mechanism is not restricted to optimal growing conditions in the laboratory, although it may be modified under field conditions depending on plant genotype.

Plant response to touch affects the behaviour of aphids and ladybirds

“…Plants were placed inside modified Perspex cages (each 10 9 10 9 40 cm), with an opening (7 cm diameter) in the front side (Ninkovic et al 2002). Pots with test plants were placed in Petri dish lids to prevent any contact with root exudates from neighbouring plants.…”

“…An aphid no-choice settling test (Ninkovic et al 2002) was used to investigate aphid behavioural response to touched and untouched plants. Both maize and bean plants were tested 24 h after the last touching treatment ended.…”

Aphid acceptance of Hordeum genotypes is affected by plant volatile exposure and is correlated with aphid growth

“…These DH lines were selected for further studies because they caused greater reductions in aphid growth compared to their DH siblings. In addition, cultivars Alva and Kara were included in the studies because they have previously shown allelobiosis effects (Ninkovic et al 2002).…”

“…In parallel studies, it has been shown that volatiles from undamaged barley plants can, in certain cultivar combinations, reduce R. padi acceptance of the volatile-exposed plants (Pettersson et al 1999;Ninkovic et al 2002). It has also been shown that exposure to volatiles from Cirsium spp.…”

“…In previous tests of plant volatile interactions in undamaged, cultivated barley, effects were detected in certain combinations of four barley genotypes, measured as changes in plant acceptance by R. padi (Ninkovic et al 2002). The aim of the present study was to determine whether there is a relationship between R. padi growth rate on a certain genotype, measured by standard tests for aphid resistance, and changed aphid host acceptance of that genotype when previously exposed to volatiles from a another barley cultivar, or from the same cultivar.…”