Multispectral Phenotyping and Genetic Analyses of Spring Appearance in Greening Plant, Phedimus spp.

Abstract

The change in appearance during the seasonal transitions in ornamental greening plants is an important characteristic. In particular, the early onset of green leaf color is a desirable trait for a cultivar. In this study, we established a method for phenotyping leaf color change by multispectral imaging and performed genetic analysis based on the phenotypes to clarify the potential of the approach in breeding greening plants. We performed multispectral phenotyping and quantitative trait locus (QTL) analysis of an F 1 population derived from 2 parental lines of Phedimus takesimensis , known to be a drought and heat-tolerant rooftop plant species. The imaging was conducted in April of 2019 and 2020 when dormancy breakage occurs and growth extension begins. Principal component analysis of 9 different wavelength values showed a high contribution from the first principal component (PC1), which captured variation in the visible light range. The high interannual correlation in PC1 and in the intensity of visible light indicated that the multispectral phenotyping captured genetic variation in the color of leaves. We also performed restriction site-associated DNA sequencing and obtained the first genetic linkage map of Phedimus spp. QTL analysis revealed 2 QTLs related to early dormancy breakage. Based on the genotypes of the markers underlying these 2 QTLs, the F 1 phenotypes with early (late) dormancy break, green (red or brown) leaves, and a high (low) degree of vegetative growth were classified. The results suggest the potential of multispectral phenotyping in the genetic dissection of seasonal leaf color changes in greening plants.

Genetic Dissection of Seasonal Changes in a Greening Plant Based on Time-Series Multispectral Imaging

“…Using QTL analysis, we identified the genetic loci involved in changes in appearance throughout the year. We demonstrated the effectiveness of multispectral analysis and genetic analysis based on [20] in the analysis of seasonal color changes of this ornamental plant.…”

“…P. takesimensis is an ornamental plant; a low degree of dormancy and unfurled leaves in winter are preferred from the standpoint of appearance. Phedimus species grow after a dormancy break in spring, are deciduous in fall, and many of them overwinter with dormant buds because of their high degree of dormancy [20,21]. Because of these characteristics and the importance of good appearance for ornamental plants, it is important to evaluate the changes in leaf coloration with seasonal changes in Phedimus species.…”

“…Because of these characteristics and the importance of good appearance for ornamental plants, it is important to evaluate the changes in leaf coloration with seasonal changes in Phedimus species. Using multispectral image analysis, we previously evaluated plant color, area of plant cover, and 15 vegetation indices in 94 F 1 plants derived from a cross between two parental lines (evergreen P 1 and winter-dormant P 2 ) of P. takesimensis [20]. We demonstrated that this approach allows for quantitative evaluation and genetic analysis of the plant color and degree of dormancy break [20].…”

“…Using multispectral image analysis, we previously evaluated plant color, area of plant cover, and 15 vegetation indices in 94 F 1 plants derived from a cross between two parental lines (evergreen P 1 and winter-dormant P 2 ) of P. takesimensis [20]. We demonstrated that this approach allows for quantitative evaluation and genetic analysis of the plant color and degree of dormancy break [20]. However, we analyzed only one seasonal time point (two measurement time points), namely, in April 2019 and April 2020.…”

“…The purpose of this study was to monitor seasonal changes in P. takesimensis appearance using multispectral image analysis throughout the year in the F 1 population established in [20] and to perform a genetic analysis of these changes. We constructed a quantitative time-series system for evaluating plant color and vegetation indices.…”