title: A comparison of the levels of hydroxamic acids in Aegilops speltoides and a hexaploid wheat and effects on Rhopalosiphum padi behaviour and fecundity.
abstract: Hydroxamic acids (HAs) are plant secondary metabolites produced by certain cereals, which have been found to be toxic to pest aphids in artificial diet assays. Previous studies have shown that tetraploid and hexaploid wheat varieties, the leaf tissues of which contained higher levels of these compounds than used in artificial diets, did not reduce aphid settling or fecundity. This current study reports findings on a high HA producing B genome accession of the diploid ancestor of wheat, Aegilops speltoides. We found that this accession does have a negative impact on aphid host selection and substantially reduces nymph production. Whole leaf tissue assays showed very high levels of HAs, well in excess of the toxic level determined in the artificial diet assays. Extraction of the apoplast fluid (AF) from this accession showed that the HA level is much lower than that of the whole tissue, but is still close to the artificial diet toxic level. Furthermore the HA level in the AF increases in response to aphid feeding. These observations could explain why hexaploid wheat remains susceptible to aphids, despite having whole leaf tissue HA levels in excess of the toxic levels determined in artificial diets.
authors.affiliation: KWS UK Limited Thriplow UK.
authors.forename: Henriett
authors.initials: H
authors.lastname: Elek
authors.affiliation: Rothamsted Research Biological Chemistry Department Harpenden UK.
authors.forename: Lesley
authors.initials: L
authors.lastname: Smart
authors.affiliation: Rothamsted Research Biological Chemistry Department Harpenden UK.
authors.forename: S
authors.initials: S
authors.lastname: Ahmad
authors.affiliation: University of Pannonia Department of Meteorology and Water Management, Georgikon Faculty Keszthely Hungary.
authors.forename: Angéla
authors.initials: A
authors.lastname: Anda
authors.affiliation: KWS UK Limited Thriplow UK.
authors.forename: C P
authors.initials: CP
authors.lastname: Werner
authors.affiliation: Rothamsted Research Biological Chemistry Department Harpenden UK.
authors.forename: J A
authors.initials: JA
authors.lastname: Pickett
mesh_terms: D000818:Animals; D000898:Antibiosis; D001042:Aphids / Q000502:physiology*; D004171:Diploidy; D005298:Fertility; D060434:Herbivory; D006877:Hydroxamic Acids / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D011123:Polyploidy; D014908:Triticum / Q000235:genetics / Q000378:metabolism*
chemical_list: D006877:Hydroxamic Acids
keywords: Aegilops speltoides; Rhopalosiphum padi; apoplast fluid; hydroxamic acids; wheat