Abstract
BackgroundIn Arabidopsis thaliana and other crucifers, the glucosinolate-myrosinase system contributes to resistance against herbivory by generalist insects. As yet, it is unclear how crucifers defend themselves against crucifer-specialist insect herbivores.Methodology/Principal FindingsWe analyzed natural variation for resistance against two crucifer specialist lepidopteran herbivores, Pieris brassicae and Plutella xylostella, among Arabidopsis thaliana accessions and in a new Arabidopsis recombinant inbred line (RIL) population generated from the parental accessions Da(1)-12 and Ei-2. This RIL population consists of 201 individual F8 lines genotyped with 84 PCR-based markers. We identified six QTL for resistance against Pieris herbivory, but found only one weak QTL for Plutella resistance. To elucidate potential factors causing these resistance QTL, we investigated leaf hair (trichome) density, glucosinolates and myrosinase activity, traits known to influence herbivory by generalist insects. We identified several previously unknown QTL for these traits, some of which display a complex pattern of epistatic interactions.Conclusions/SignificanceAlthough some trichome, glucosinolate or myrosinase QTL co-localize with Pieris QTL, none of these traits explained the resistance QTL convincingly, indicating that resistance against specialist insect herbivores is influenced by other traits than resistance against generalists.
Highlights
Arabidopsis thaliana recombinant inbred lines (RILs) have been widely used for mapping of quantitative trait loci (QTL)
Taking advantage of RILs derived from crosses between the accessions Columbia (Col) and Landsberg erecta (Ler) [2], and between Ler and Cape Verdi Islands (Cvi) [3], several insect resistance QTL have been mapped and, subsequently, several were cloned and characterized [4,5,6,7,8]
E-mail: kroymann@ice.mpg. de among Arabidopsis accessions and in a new Arabidopsis recombinant inbred line, Da(1)-126Ei-2, and we investigate whether variation in glucosinolate profiles, myrosinase activity or trichomes contributes to variation in resistance
Summary
Arabidopsis thaliana recombinant inbred lines (RILs) have been widely used for mapping of quantitative trait loci (QTL) (reviewed in [1]). Taking advantage of RILs derived from crosses between the accessions Columbia (Col) and Landsberg erecta (Ler) [2], and between Ler and Cape Verdi Islands (Cvi) [3], several insect resistance QTL have been mapped and, subsequently, several were cloned and characterized [4,5,6,7,8] In most cases, these studies involved lepidopteran species with a broad host range (generalists) such as Spodoptera exigua or Trichoplusia ni, and found that generalist insects were sensitive towards glucosinolate-based defenses. We analyzed natural variation for resistance against two crucifer specialist lepidopteran herbivores, Pieris brassicae and Plutella xylostella, among Arabidopsis thaliana accessions and in a new Arabidopsis recombinant inbred line (RIL) population generated from the parental accessions Da(1)-12 and Ei-2. Glucosinolate or myrosinase QTL colocalize with Pieris QTL, none of these traits explained the resistance QTL convincingly, indicating that resistance against specialist insect herbivores is influenced by other traits than resistance against generalists
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