Mapping Floral Genetic Architecture in Prunus mume, an Ornamental Woody Plant

Abstract

Floral traits are both evolutionarily and economically relevant for ornamental plants. However, their underlying genetic architecture, especially in woody ornamental plants, is still poorly understood. We perform mapping experiments aimed at identifying specific quantitative trait loci (QTLs) that control the size, shape, architecture, color, and timing of flowers in mei (Prunus mume). We find that the narrow region of chromosome 1 (5–15 Mb) contains a number of floral QTLs. Most QTLs detected from this mapping study are annotated to candidate genes that regulate various biological functions toward the floral formation. We identify strong pleiotropic control on different aspects of flower morphology (including shape, petal number, pistil number, petal color, and calyx color) and flower timing, but find different genetic systems that mediate whether a flower produces pistils and how many pistils a flower produces. We find that many floral QTLs display pleiotropic effects on shoot length growth but shoot radial growth, implicating a possible association of floral display with light capture. We conduct a transcriptomic study to characterize the genomic signature of floral QTLs expressed in mei. Our mapping results about the genetic control of floral features make it promising to select superior varieties for mei carrying flowers of ornamental value.

A High-Resolution Linkage Map Construction and QTL Analysis for Morphological Traits in Anthurium (Anthurium andraeanum Linden)

“…The result that these QTLs associated with different traits were co-located might be attributed to one same QTL, a gene multi-effect, or two QTLs closely linked, therefore leading to the correlation among morphological traits. Similar colocalizing QTLs were also observed in other plants such as prunus mume [43,44], rice [45], wheat [46,47], sesame [48], cauliflower [49], barley, and so on [50]. However, whether the co-localized QTLs are single-gene with pleiotropism or are just closely linked but distinct genes in our results remains to be further studied.…”

Mutations overlying the miR172 target site of TOE-type genes are prime candidate variants for the double-flower trait in mei

“…However, above-threshold signals were also present within the unanchored scaffolds. In an F 1 ‘Liuban’ (SF) × ‘Huang Lve’ (DF) mei progeny using floral diameter as an estimator of flower doubleness, strongly associated markers were mapped in a 5 Mb interval on Pa1, with signal peaks covering the interval between 4,580,444 and 6,253,182 bp 8 , but no information was provided about the type of DF trait inheritance. Segregation of the DF trait was analyzed in another F 1 progeny derived from the cross of mei accessions ‘XM’(SF) × ‘FP’(DF), showing a segregation ratio SF vs DF of about 1:1 10 consistent with a dominant inheritance of the causative variant(s).…”

“…In the second scenario the mutation is dominant, as persistence of the transcript of one of the two alleles is sufficient to confer the phenotype. Independent mapping works 6 , 8 , 10 provided the position and markers tightly associated to the DF trait in the mei germplasm on chromosome 1, ruling out the possibility that mutations on the gene orthologous to that encoding miR172d in peach were responsible in those materials, as this is found on chromosome 5 of the tortuosa genome (5: 25,786,770). Also considering the reported dominant inheritance of the trait 10 euAP2 genes on chromosome 1 were therefore prime candidates for closer inspection, and one of them, pmTOE , fell within the genomic region under scrutiny.…”

“…The completion of P. mume whole-genome reference, along with the availability of genome sequencing data of wide Eastern germplasm collections 5 – 8 , is allowing the investigation of the genetic basis of important traits, such as cold resistance, plant architecture, flower type, color and aroma, as well as the development of useful tools for molecular breeding in this species. Flowering mei represent a prime choice for landscaping, due to its extreme blooming precociousness and traits associated to flower appearance, such as petal color and flower shape.…”

“…Nevertheless, a variant and/or gene responsible for single or double flower type has remained elusive in mei. Recent QTL mapping experiments support a relatively simple inheritance of the trait, identifying a major locus on chromosome 1 affecting flower diameter 8 , 10 , although the large mapping interval hindered a clear positioning and identification of the causal mutation(s) or candidate gene variant(s). By contrast, several studies in Rosaceae and other plant families has shed light on different classes of mutations leading to the double flower phenotype 11 – 16 .…”