Abstract
Most important breeding goals in ornamental crops are plant appearance and flower characteristics where selection is visually performed on direct offspring of crossings. We developed an image analysis toolbox for the acquisition of flower and petal images from cultivated carnation (Dianthus caryophyllus L.) that was validated by a detailed analysis of flower and petal size and shape in 78 commercial cultivars of D. caryophyllus, including 55 standard, 22 spray and 1 pot carnation cultivars. Correlation analyses allowed us to reduce the number of parameters accounting for the observed variation in flower and petal morphology. Convexity was used as a descriptor for the level of serration in flowers and petals. We used a landmark-based approach that allowed us to identify eight main principal components (PCs) accounting for most of the variance observed in petal shape. The effect and the strength of these PCs in standard and spray carnation cultivars are consistent with shared underlying mechanisms involved in the morphological diversification of petals in both subpopulations. Our results also indicate that neighbor-joining trees built with morphological data might infer certain phylogenetic relationships among carnation cultivars. Based on estimated broad-sense heritability values for some flower and petal features, different genetic determinants shall modulate the responses of flower and petal morphology to environmental cues in this species. We believe our image analysis toolbox could allow capturing flower variation in other species of high ornamental value.
Highlights
Dianthus is a large genus with over 300 species, a high incidence of polyploidy [1], and the fastest speciation rate reported to date in the flowering plants [2]
Correlation analyses (Table S3A) allowed us to reduce the number of parameters accounting for the variation in flower morphology to only four: flower area (FA), flower aspect ratio (FAR), flower solidity (FS) and flower convexity (FC)
We present here a systematic approach for acquiring and analyzing images taken from flowers and petals of cultivated carnation
Summary
Dianthus is a large genus with over 300 species (including carnations and pinks), a high incidence of polyploidy [1], and the fastest speciation rate reported to date in the flowering plants [2]. Breeding strategies to improve the quality of cultivated carnation need to consider a large number of characteristics from the cultivars selected, and are normally hindered by the polygenic nature of some of the traits selected [4]. From the detailed analysis of 75 commercial cultivars and 9 wild populations, the authors reported four principal components (PCs) accounting for most of the variation found in petal shape in this species [6]. In another study using a single natural population of yellow monkeyflower (Mimulus guttatus), epistatic genetic interactions among quantitative trait loci (QTL) for flower size were identified, which were proposed to account for some of the evolutionary differences observed in flower features in Mimulus spp. In another study using a single natural population of yellow monkeyflower (Mimulus guttatus), epistatic genetic interactions among quantitative trait loci (QTL) for flower size were identified, which were proposed to account for some of the evolutionary differences observed in flower features in Mimulus spp. [7,8]
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