Abstract
Summary ●Inflorescence architecture in plants is often complex and challenging to quantify, particularly for inflorescences of cereal grasses. Methods for capturing inflorescence architecture and for analyzing the resulting data are limited to a few easily captured parameters that may miss the rich underlying diversity.●Here, we apply X‐ray computed tomography combined with detailed morphometrics, offering new imaging and computational tools to analyze three‐dimensional inflorescence architecture. To show the power of this approach, we focus on the panicles of Sorghum bicolor, which vary extensively in numbers, lengths, and angles of primary branches, as well as the three‐dimensional shape, size, and distribution of the seed.●We imaged and comprehensively evaluated the panicle morphology of 55 sorghum accessions that represent the five botanical races in the most common classification system of the species, defined by genetic data. We used our data to determine the reliability of the morphological characters for assigning specimens to race and found that seed features were particularly informative.●However, the extensive overlap between botanical races in multivariate trait space indicates that the phenotypic range of each group extends well beyond its overall genetic background, indicating unexpectedly weak correlation between morphology, genetic identity, and domestication history.
Highlights
Plant organs show tremendous diversity in size and shape as a result of differential growth and patterning throughout development
From the Sorghum Association Panel (Casa et al, 2008), 34 accessions were selected for imaging with two field replicates each
An additional 21 accessions were imaged with a single replicate each, for a total of 55 sorghum accessions included in this study, consisting of nine or more accessions from each botanical race
Summary
Plant organs show tremendous diversity in size and shape as a result of differential growth and patterning throughout development. At field scales, plant height and other traits can be measured using 3D laser scanners or unmanned aerial systems (Friedli et al, 2016; Malambo et al., 2018), resulting in phenomics becoming an increasingly important tool in field research Between these two scales, specific structures of and within plants can be imaged in three dimensions using high-resolution X-ray computed tomography (XRT; Stuppy et al, 2003; Dhondt et al, 2010; Perez-Torres et al, 2015; Rogers et al, 2016; Jiang et al, 2019). 3D wheat grains have been segmented and measured from images of the wheat panicle (Hughes et al, 2017), and 3D branching topology has been characterized comprehensively in grapevine inflorescences (Li et al, 2017, 2019) Software such as CHIMERA (Pettersen et al, 2004) has been used widely for the visualization and analysis of molecular structures, density maps, 3D microscopy, and associated data (Goddard et al, 2017), and topological data analysis tools such as the medial axis (Blum, 1967) have been used extensively for analyzing shape structure and for forming shape descriptors. The medial axis, in particular, is a topological curve skeleton that is a
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