Assessment of genome size variation in palm germplasm revealed by flow cytometry

Abstract Flow cytometry (FC) is a well-established technique for estimating nuclear deoxyribonucleic acid (DNA) content and ploidy levels, providing valuable insights into the genetic structure and diversity of plant species. The present study aimed to assess inter- and intraspecific variation in nuclear DNA content among conserved palm germplasm accessions maintained at the Indian Council of Agricultural Research–Central Plantation Crops Research Institute. The materials included 20 accessions of Cocos nucifera (coconut), 3 accessions of Areca catechu (arecanut), 2 wild relatives of arecanut ( A. triandra and A. concinna ) and related genera Normanbya normanbyi (black palm), Actinorhytis calapparia (calappa palm) and Borassus flabellifer (palmyrah palm). Nuclear DNA content was estimated using FC with Pisum sativum cv. Citrad (2C = 9.09 picograms [pg]) as the reference standard. Substantial interspecific variation was observed in 2C DNA content, ranging from 5.56 pg in A. calapparia to 12.70 pg in B. flabellifer , corresponding to 1C genome sizes of 2722.23 and 6210.30 Mb, respectively. Notable intraspecific variation was also detected among coconut (5.66–6.16 pg) and arecanut accessions (6.32–6.60 pg), as well as between female (12.59 pg) and male (12.70 pg) palms of B. flabellifer . Hierarchical cluster analysis based on genome size grouped the samples into two major clusters, reflecting their genomic relatedness. The observed variation in nuclear DNA content underscores the potential of genome size as a cytogenetic marker for species discrimination, evolutionary studies and germplasm characterization. The baseline genome size information generated will facilitate the effective utilization of palm genetic resources in conservation, pre-breeding and future genome sequencing efforts.