Barley systematics and taxonomy foreseen by seed morphometric variation

Abstract

Since its Neolithic domestication in the Fertile Crescent, barley has spread to all continents and represents a major cereal in many modern agrarian systems. Current barley diversity includes thousands of varieties divided into four main categories corresponding to 2-row and 6-row subspecies and naked and hulled types, each of them with winter and spring varieties. This diversity is associated to different uses and allow cultivation in diverse environments. We used a large dataset of 58 varieties of French origin, (1) to assess the taxonomic signal in barley grain measurements comparing 2-row and 6-row subspecies, and naked and hulled types; (2) to test the impact of the sowing period and interannual variation on the grains size and shape; (3) to investigate the existence of morphological differences between winter and spring types; and finally (4) to contrast the relationship between the morphometric and genetic proximity. Size and shape of 1980 modern barley caryopses were quantified through elliptic Fourier Transforms and traditional size measurements. Our results indicate that barley grains record morphological diversity of the ear (89.3% classification accuracy between 2-row/6-row subspecies; 85.2% between hulled and naked type), sowing time of the grains (from 65.6% to 73.3% within barley groups), and environmental conditions during its cultivation and varietal diversity. This study opens perspectives for studying archaeological barley seeds and tracing the barley diversity and evolution since the Neolithic.

Deep learningversusgeometric morphometrics for archaeobotanical domestication study and subspecific identification

“…Among the model species studied by our team, we retained those for which we have enough material, secure identification and associated publication record: grapevine pips (Pagnoux et al ., 2015; Bonhomme et al ., 2020b), barley grains (Jeanty et al ., 2023), olive stones (Bourgeon et al ., 2018; Terral et al ., 2021) and dates seeds (Terral et al ., 2012; Gros-Balthazard et al ., 2017) (Table 1). All models corresponded to a binary classification task with 2-versus 6-row types of barley ( Hordeum vulgare ), and wild versus domestic for the three other taxa.…”

“…The morphological distinction between wild and domestic types using GMM is now very accurate for olive (Terral et al ., 2004, 2021) and grapevine (Terral et al ., 2010; Bonhomme et al ., 2022). On the other hand, distinguishing between wild and domestic date palm seeds (Terral et al ., 2012; Gros-Balthazard et al ., 2017), as well as between two- and six-row barley grains remains challenging (Ros et al ., 2014; Bonhomme et al ., 2017b; Wallace et al ., 2018; Jeanty et al ., 2023).…”