Abstract
Amomum Roxb. is a large genus in the family Zingiberaceae which has been recently recircumscribed and 6 new genera were proposed. The phylogenetic structure of the newly defined genus Amomum s.s. was investigated with traditional sequencing methods (ITS region) and state-of-the-art next generation sequencing (NGS) Hyb-Seq method targeting 494 nuclear genes, nearly-complete plastome and full rDNA cistron.
The absolute genome size of the same accessions was mapped onto the resulting phylogeny to estimate the evolutionary pattern of genome size changes. All phylogenies showed four basic groups (lineages) in Amomum: group A (A. subulatum Roxb., A. petaloideum S.Q.
Tong), group B (A. repoeense Pierre ex Gagnep. and related species), group C (A. maximum Roxb. and related species) and group D (former Elettariopsis Baker). Group A was basal to all other groups in the NGS and cpDNA topology, but in the ITS and rDNA topologies group B was at the base instead.
The NGS phylogeny was the most resolved, and the cpDNA and rDNA phylogenies differed from it in some deeper nodes. The rDNA analysis procured the same topology as the ITS analysis.
Absolute (2C) genome size showed an increasing trend towards the more derived groups. The smallest 2C genome size in the genus was found in A. subulatum (2C = 3.54 pg) and the largest in A. "cinnamomeum", ined. (2C = 15.66 pg).
Group D (former Elettariopsis) had the greatest 2C genome sizes (ranging from 2C = 5.39 pg to 15.66 pg), mainly in the species found in the south-eastern area of the geographical distribution of the genus. This corresponds with the pattern observed in the whole family Zingiberaceae, where deciduous plants from monsoonal areas have smaller genomes than their evergreen relatives from evergreen tropics.