Phenotypic variation of floral organs in flowering crabapples and its taxonomic significance

Abstract

Background In angiosperms, phenotypic variation of floral organs is often considered as the traditional basis for the evolutionary relationship of different taxonomic groups above the species level. However, little is known about that at or below the species level. Here, we experimentally tested the phenotypic variation of Malus floral organs using combined methods of intraspecific uniformity test, interspecific distinctness analysis, principal component analysis, Pearson correlation analysis, and Q-type cluster analysis. The ancestor-inclined distribution characteristic analysis of Malus species and cultivars floral attributes was also carried out, so as to explore its taxonomic significance. Results 15/44 phenotypic traits (e.g., flower shape, flower type, flower diameter, ...) were highly consistent, distinguishable, and independent and could be used as the basis for Malus germplasm taxonomy. The studied 142 taxa were divided into two groups (A, B) and five sub-groups (A1, A2, B1, B2, B3), with significantly variable floral phenotypic attributes between groups and within sub-groups. Malus natural species were relatively clustered in the same section (series) while homologous cultivars showed evidence of ancestor-inclined distribution characteristics. However, no significant correlation between the evolutionary order of sections (Sect. Docyniopsis → Sect. Chloromeles → Sect. Sorbomalus → Sect. Eumalus) and group/sub-groups (B3 → B2 → B1 → A). Conclusions Phenotypic variation of floral organs could better explore the genetic relationship between Malus taxa. The findings improved our cognition of floral phenotypic variation taxonomic significance under the species level.

Variability and correlations of traits of the flower, leaf and fruit of Malus zumi

“…They considered the variability of the floral organs of the apple tree. Our data on high homogeneity (low variability) of flower traits are consistent with the results of Zhou [20]. Delgado's study raises the question of correlations between phenotypic traits of flowering and pollen quality [22].…”

“…A research by Dan and Sestras shows variability in fruit size and flavor in F1 hybrids where Malus zumi was either the mother or father [9]. The variability of crabapples has been studied by Zhou [20] and Weryszko-Chmielewska [21]. They considered the variability of the floral organs of the apple tree.…”

Flower and fruit morphological characteristics of different crabapple genotypes of ornamental value

“…The close correlations indicate links between essential characters for the decorative value of the ornamental apple, which could be useful in apple breeding and used as indirect selection indices. Multivariate analysis and Pearson correlations are working methods that have been well validated in crabapple genotypes (Yu et al, 2021;Zhou et al, 2021). The obtained results contribute to the knowledge of the taxonomic significance of the floral phenotypic variation at the level of some ornamental apple cultivars, completing similar information in the field (Zhou et al, 2019(Zhou et al, , 2021.…”

“…Multivariate analysis and Pearson correlations are working methods that have been well validated in crabapple genotypes (Yu et al, 2021;Zhou et al, 2021). The obtained results contribute to the knowledge of the taxonomic significance of the floral phenotypic variation at the level of some ornamental apple cultivars, completing similar information in the field (Zhou et al, 2019(Zhou et al, , 2021. The phenotypic diversity of reproductive and decorative organs could better explore the genetic relationship between Malus genotypes, but also the manifestation of characteristics of ornamental interest in specific environmental conditions in which the evaluation was performed.…”

Comprehensive Evaluation of Apple Germplasm Genetic Diversity on the Basis of 26 Phenotypic Traits

“…Correlation analyses can reveal the degree of correlation between traits [33]. In this study, correlation analysis of the phenotypic traits of apple germplasm resources detected significant correlations between several traits.…”