Abstract
Thrips are a worldwide threat to Capsicum because they damage fruits, flowers and leaves directly by feeding, and indirectly by vectoring tospoviruses such as tomato spotted wilt virus. Therefore, growers would benefit from thrips-resistant varieties. Previously, a quantitative trait locus (QTL) that provides resistance to Frankliniella occidentalis has been identified. Here we explore the potential of this QTL for breeding thrips-resistant varieties by studying its effect on two thrips species (i.e. F. occidentalis and Thrips tabaci) in four different Capsicum annuum backgrounds. We observed differences in thrips resistance between different genetic backgrounds, both in plants that have the resistance allele for the QTL region in homozygous state as well as in plants with the susceptibility allele in homozygous state. This suggests the presence of factors in these backgrounds that either increase or reduce thrips resistance. Altogether, we confirmed the major effect of the QTL on thrips resistance in all four genetic backgrounds to both F. occidentalis and T. tabaci, thus showing its general applicability as a source for breeding thrips-resistant Capsicum varieties.
Highlights
Thrips are a major pest in vegetable, fruit and ornamental crops worldwide (Kirk and Terry 2003)
Two Three-Way ANOVAs with quantitative trait locus (QTL) genotype (‘‘R’’ or ‘‘S’’ allele), thrips species (F. occidentalis or T. tabaci) and genetic background as factors followed by a Fisher’s Protected LSD were used to determine the effects of each factor on larval development, possible interactions between these factors, and whether larval development was significantly different between groups
In all four backgrounds investigated, the level of thrips resistance was higher in leaves of plants that have the resistance (‘‘R’’) allele in homozygous state for the QTL region on chromosome 6, than on leaves of plants that have the susceptibility (‘‘S’’) allele for the QTL region, both in the lines with background 1 and 2 (Table 4; experiment 1; Supplementary data Table S1) and in the lines with background 3 and 4 (Table 5; experiment 2; Supplementary data Table S2)
Summary
Thrips are a major pest in vegetable, fruit and ornamental crops worldwide (Kirk and Terry 2003). We observed significant differences in susceptibility to thrips between the different backgrounds: susceptibility to F. occidentalis in background 1 was significantly higher compared to background 2, and background 4 had significantly higher levels of resistance to both thrips species compared to background 3 when the plants carry the resistance allele in homozygous state This indicates that additional factors in the genetic background outside of the QTL region contribute to thrips resistance, affecting F. occidentalis, T. tabaci, or both thrips species. It is important to validate the effect of the QTL in different backgrounds, as additional factors that affect thrips resistance might be present or lacking
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