Inheritance of biochemical and morphological characters associated with two-spotted spider mite resistance in Pelargonium xhortorum

Richard Grazzini, Donald Walters, Jody Harmon, David J. Hesk, Diana Cox-Foster, June Medford, Richard Craig, Ralph O. Mumma

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Diploid zonal geraniums (Pelargonium x hortorum) are able to resist attack by small arthropod pests such as the two-spotted spider mite (Tetranychus urticae Koch) when exudate produced by tall glandular trichomes contains a high percentage of ω5-unsaturated anacardic acids. Trichomes of susceptible plants exude primarily saturated anacardic acids. Inbred mite-resistant and -susceptible geraniums were reciprocally crossed and the F1, F2, and backcross generations were examined for anacardic acid composition and trichome density. Selected F2 plants were bioassayed for resistance to two-spotted spider mites. High concentrations of (ω5-unsaturated anacardic acids in resistant plants are conditioned by a single dominant allele. We propose that inheritance of tall glandular trichome density can be controlled by a small number of loci (possibly as few as one) exhibiting codominance. F2, with low densities of tall glandular trichomes and producing ω5-unsaturated anacardic acids, displayed effective resistance to two-spotted spider mites as measured by mite mortality and fecundity. A genetic model for the biosynthesis of anacardic acids is proposed.

Original languageEnglish (US)
Pages (from-to)373-379
Number of pages7
JournalJournal of the American Society for Horticultural Science
Volume122
Issue number3
DOIs
StatePublished - May 1997

All Science Journal Classification (ASJC) codes

  • Genetics
  • Horticulture

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