A QTL associated with leaf trichome traits has a major influence on the abundance of the predatory mite Typhlodromus pyri in a hybrid grapevine population

Paola Barba,Gregory M Loeb,Karen Wentworth,Rebecca Loughner,Jan Peter Nyrop,Bruce I Reisch

doi:10.1038/s41438-019-0169-8

Paola Barba, Gregory M Loeb + Show 4 more

Open Access

https://doi.org/10.1038/s41438-019-0169-8

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Abstract

The abundance of predatory phytoseiid mites, Typhlodromus pyri, important biological control agents of spider mite pests in numerous crops, is positively influenced by the density of leaf trichomes and tuft-form domatia in vein axils. Identification of the genetic regions controlling both trophic levels could facilitate the improvement of predatory mite habitat in breeding programs. The abundance of T. pyri and non-glandular trichomes was measured in a segregating F1 family derived from the cross of the complex Vitis hybrid, ‘Horizon’, with Illinois 547-1 (V. rupestris B38 × V. cinerea B9), finding positive correlation among traits. High density genetic maps were used to localize one major quantitative trait locus (QTL) on chromosome 1 of Illinois 547-1 associated with both predatory mite abundance and leaf trichomes. This QTL explained 23% of the variation in phytoseiid abundance and similar amounts of variance in domatia rating (21%), domatia size (16%), leaf bristle density (37% in veins and 33% in blades), and leaf hair density (20% in veins and 15% in blades). Another nine QTL distributed among chromosomes 1, 2, 5, 8, and 15 were associated solely with trichome density, and explained 7–17% of the phenotypic variation. Combined, our results provide evidence of the genetic architecture of non-glandular trichomes in Vitis, with a major locus influencing trichome densities, domatia size and predatory mite abundance. This information is relevant for breeding grapevines with a more favorable habitat for biological control agents.

Highlights

Leaf morphological traits in plants can positively or negatively affect plant fitness through a direct effect on the second trophic level and indirectly by affecting the abundance of the third trophic level
In this paper we address the first question by studying the genetics of predatory mite abundance and leaf trichomes in a cross of two grapevine hybrids ‘Horizon’ and Illinois 547-1
To test whether predatory mite abundance and density of leaf morphology traits such as domatia, bristles and hairs have common genetic factors, we characterized parental vines and their F1 family segregating for these traits

Summary

Introduction

Leaf morphological traits in plants can positively or negatively affect plant fitness through a direct effect on the second trophic level (plant feeding insects) and indirectly by affecting the abundance of the third trophic level (natural enemies of plant feeding insects) (tri-trophic interactions sensu[1]). Leaf trichomes have a direct negative effect on the performance of small herbivorous arthropods (direct defense)[2,3,4,5,6,7]. This includes both non-glandular epidermal trichomes (bristles and hairs) and glandular trichomes that release sticky and/or toxic substances[8]. Leaf trichomes positively affect preference or performance of herbivorous arthropods, more commonly, performance can be enhanced indirectly by negatively affecting performance and predation rates of natural enemies[9] This is best shown with glandular trichomes[8,10,11,12]. The relationship between non-glandular trichomes and natural enemies such as predatory and mycophagous mites has frequently been shown to be positive (reviewed in refs. 13,14) counter examples exist[14,15,16,17]

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