Seed testa sculpture of species of Allium L. (Amaryllidaceae) and its taxonomic implications

1 Department of Biology and Chemistry, Changwon National University, Uichang-gu, 35, Changwon, 51140, South Korea 2 Department of Biology, School of Arts and Science, National University of Mongolia, Ikh Surguuliin Gudamj, 1, Ulaanbaatar, 14201, Mongolia 3 Botanical Garden of the University of Osnabrueck, Albrechtstrasse, 29, Osnabrueck 49076, Germany 4 I. M. Sechenov First Moscow State Medical University Ministry of Health of the Russian Federation, Department of Pharmaceutical and Natural Sciences, Izmailovsky Boulevard, 8, Moscow, 105043, Russian Federation 5 E-mail: baasanmunkh.sh@gmail.com; ORCID iD: https://orcid.org/0000-0003-4224-9376 6 E-mail: hjchoi1975@changwon.ac.kr; ORCID iD: https://orcid.org/0000-0001-6315-0071 7 E-mail: oyunaa@num.edu.mn; ORCID iD: https://orcid.org/0000-0003-3772-3301 8 E-mail: nfriesen@uni-osnabrueck.de; ORCID iD: https://orcid.org/0000-0003-3547-3257 *Corresponding authors


Introduction
Seed morphology and seed testa studies have been suggested to be taxonomically useful for species and section rank detection in the genus Allium. Seed testa sculpture of anticlinal wall with S-, U-, Omega-, and straight type undulation and one central verruca with marginal verrucae or densely granulose periclinal wall are important characters to sections and subgenera level (Baasanmunkh et al., 2020). For instance, straight anticlinal walls were dominated in subg. Cepa, Reticulatobulbosa and Polyprason and the periclinal walls were distinguished by central big verruca and dense granules. The U-, Omega-and S-type undulation anticlinal walls and convex periclinal walls with several large verrucae or marginal verrucae were dominated in subg. Allium and Melanocrommyum (Celep et al., 2012;Lin, Tan, 2017;Veiskarami et al., 2018;Baasanmunkh et al., 2020). Additionally, several new taxa of Allium have been recognized based on their morphology including seed macroand micro-morphological characteristics and phylogenetic studies (Deniz et al., 2015;Duman et al., 2017).
The genus Allium L., one of the most diverse and the largest genus of petaloid monocots (Friesen et al., 2006;Li et al., 2010), comprises more than 1000 species (Govaerts et al., 2005(Govaerts et al., -2021. This genus is naturally distributed in the Northern Hemisphere (Friesen et al., 2006) and its main diversity is in the mountainous areas of southwestern and central Asia (Fritsch, Friesen, 2002;Friesen et al., 2006).
To date, seed morphology and seed testa sculpture of 460 taxa have been studied from different countries (Baasanmunkh et al., 2020). In particular, most of species were investigated from the Turkey, Iran and Central Asian countries (Celep et al., 2012;Lin, Tan, 2017;Veiskarami et al., 2018;Baasanmunkh et al., 2020). However, seed morphological studies of many species and sections of Allium is remaining. In particular, Friesen et al. (2006)  The article provides descriptions of the surface sculpture of 24 species of Allium made by the last author 15 years ago. The descriptions of testa sculpture of most of them have not yet been published in previous works. Since 24 species represent 13 sections and 5 subgenera in the genus Allium (three samples are type species of sections Daghestanica: Nigrimontana and Sikkimensia), they complement the spectrum of species whose testa sculpture has been published so far and contribute the understanding of the evolutionary and taxonomic significance of seed surface sculpture for the classification of the genus.

Specimens
information with species/ classification and origin are presented in Table 1.
No special pre-treatments were applied for the preparation of scanning electron microscopy (SEM). Seeds were immersed in absolute ethanol and sputtered with a gold coating in a Sputter Coater: Polaron E5150, Polaron Equipment Ltd, Hertfordshire, England. In all cases, the seeds of at least five samples per accession were analysed, characterized, and photographed with a Zeiss DSM 926 (Zeiss, Oberkochen, Germany) scanning electron microscope at the Zoological Department of the Osnabrueck University.

Result and Discussion
Recently, seed testa sculpture of Allium have been quite well studied from different countries based on the herbarium and field collection materials (Celep et Baasanmunkh et al., 2020). In this study, we investigated seed testa sculpture of 24 species in genus Allium L. based on herbarium materials and seed collected in the living Allium collections in Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany and Botanical Garden of the Osnabrueck University, Germany (GAT and OSN accessions in the table 1, respectively). Among these, seed testa sculpture of 21 species have been studied for the first time. The seed testa micrographs are sorted in alphabetical order of subgenus, section and species names ( Table 2; Figs. 1, 2). Each species and sections of the subgenera are discussed and provided below.
Subgenus Amerallium Traub. We described seed testa sculpture of two species A. fasciculatum Rendle (sect. Brommatorhiza) and A. stellatum Nutt. ex Ker Gawl. (sect. Lophyoprason) in this subgenus. Allium fasciculatum was investigated for the first time here. The testa cell was irregularly polygonal 3-4-edged and irregularly polygonal in A. fasciculatum (Fig. 1G) and A. stellatum (Fig. 1H), respectively. Choi and Cota-Sánchez (2010) studied straight anticlinal wall and periclinal wall with minutely roughened for A. stellatum from Canada. Our result was suggested similar result for anticlinal wall but periclinal wall somewhat differs from result of Choi and Cota-Sánchez (2010).
Finally, we provided that seed testa sculpture is important character for the species and section level of Allium. Especially, the straight, Omega-, U-and S-type anticlinal walls can be used to distinguish taxa on the subgenus level.