Green plants play a fundamental role in ecosystems, human health, and agriculture. As de novo genomes are being generated for all known eukaryotic species as advocated by the Earth BioGenome Project, increasing genomic information on green land plants is essential. However, setting standards for the generation and storage of the complex set of genomes that characterize the green lineage of life is a major challenge for plant scientists. Such standards will need to accommodate the immense variation in green plant genome size, transposable element content, and structural complexity while enabling research into the molecular and evolutionary processes that have resulted in this enormous genomic variation. Here we provide an overview and assessment of the current state of knowledge of green plant genomes. To date fewer than 300 complete chromosome-scale genome assemblies representing fewer than 900 species have been generated across the estimated 450,000 to 500,000 species in the green plant clade. These genomes range in size from 12 Mb to 27.6 Gb and are biased toward agricultural crops with large branches of the green tree of life untouched by genomic-scale sequencing. Locating suitable tissue samples of most species of plants, especially those taxa from extreme environments, remains one of the biggest hurdles to increasing our genomic inventory. Furthermore, the annotation of plant genomes is at present undergoing intensive improvement. It is our hope that this fresh overview will help in the development of genomic quality standards for a cohesive and meaningful synthesis of green plant genomes as we scale up for the future.

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DNA barcoding has transformed the fields of ecology, evolution, and conservation by providing a rapid and effective tool for species identification. The growth of DNA barcodes as a resource for biologists has followed advances in computational and sequencing technology that have enabled high-throughput barcoding applications. The global DNA barcode database is expanding to represent the diversity of species on Earth thanks to efforts by international consortia and expanding biological collections. Today, DNA barcoding is instrumental in advancing our understanding of how species evolve, how they interact, and how we can slow down their extirpation and extinction. This review focuses on current applications of DNA barcode sequences to address fundamental lines of research, as well as new and expanding applications of which DNA barcoding will play a central role.