Effect of epicuticular waxes of poplar hybrids on the aphid Chaitophorus leucomelas (Hemiptera: Aphididae)

Abstract

Insect response to plant surface features is a critical step in host-finding and acceptance of herbivorous insects. The plant surface is usually covered with epicuticular waxes (EWs), which are not only involved in water physiology, but also provide resistance to insects. In the present work the probing behaviour and performance of the aphid Chaitophorus leucomelas Koch (Hemiptera: Aphididae) on dewaxed and waxed leaves of two poplar hybrids, [(Populus trichocarpa Torr. & Gray · Populus deltoides Bartram ex Marshall) · P. deltoides] (TD · D) and [(P. trichocarpa · Populus maximowiczii Henry) · (P. trichocarpa · P. maximowiczii)] (TM · TM), previously reported as susceptible and resistant, respectively, are described. Laboratory experiments showed that in naturally waxed leaves of the resistant hybrids, aphids devoted less time to probing and more time to non-probing behaviour when compared with their behaviour on susceptible hybrids. These differences were not present when leaves of these hybrids were experimentally dewaxed. A field experiment demonstrated that aphid reproductive performance was affected by hybrid genotype (higher in the TD · D) but not by EWs, although a trend of lower performance on dewaxed leaves in both hybrids was apparent. SEM analysis of EWs revealed micromorphological differences between both hybrids. These results support the idea that EWs affect aphid behaviour in poplars, with a rather slight impact on reproductive performance.

Host Selection and Probing Behavior of the Poplar Aphid <I>Chaitophorus leucomelas</I> (Sternorrhyncha: Aphididae) on Two Poplar Hybrids With Contrasting Susceptibility to Aphids

“…These results conÞrm previous studies reporting that poplar hybrids with P. maximowiczii parentage are more resistant to aphids by reducing probing behavior and fecundity (Alfaro-Tapia et al 2007, Ramṍrez et al 2004), A higher antixenotic and antibiosis resistance of poplar hybrids with P. maximowiczii parentage (NM6) to the poplar-and-willow borer, C. lapathi (L.), has also been reported , although, chemically mediated resistance was not supported (Broberg et al 2010). Nonetheless, poplar hybrids with P. maximowiczii parentage are serious candidates for breeding programs aimed at enhancing insect resistance.…”

“…A related compound, 1-hexacosanol, has been associated with delayed initialization of stylet penetration in oat by the black bean aphid, Aphis fabae Scopoli (Powell et al 1999). Related to these results, in an earlier study on this aphidÐpoplar interaction, Alfaro-Tapia et al (2007) found that C. leucomelas devoted more time to probing and less time to nonprobing behavior on dewaxed leaves of the TM ϫ TM hybrid compared with natural waxed leaves. This result also suggests that waxes are in some way involved in antixenosis activity against aphids.…”

“…These differences were not present when leaves of both hybrids were experimentally dewaxed, suggesting that waxes elicit an antixenotic effect on aphid behavior in poplars. However, the removal of epicuticular waxes did not affect the reproductive performance of aphids (Alfaro-Tapia et al 2007). These results suggest that, in addition to waxes, other plant factors are also likely to be involved in the resistant status of TM ϫ TM poplar hybrids, such as plant volatiles or internal metabolites.…”

Differential Expression of Candidate Defense Genes of Poplars in Response to Aphid Feeding

“…Formerly, these poplar hybrids were imported from the Poplar Molecular Genetics Cooperative, University of Washington (Seattle, WA). These hybrids were described as susceptible and resistant to aphids, respectively (Ramṍrez et al 2004, Alfaro-Tapia et al 2007). One clone of each hybrid was used.…”

Evaluation of Beta corolliflora for Resistance to Curly Top in Idaho

“…capitata) (Eigenbrode et al, 1991), pea (Pisum sativum L.) (White and Eigenbrode, 2000) and poplar hybrids (Populus sp.) (Alfaro-Tapia et al, 2007). Savitsky (1969) used a much higher number of beet leafhoppers and a longer exposure period to the vector than is normally necessary to transfer the virus in her study, which indicates that resistance to initial infection may be a possible mechanism of resistance.…”