Bananas and plantains (Musa spp.) are grown in more than a hundred tropical and subtropical countries and provide staple food for hundreds of millions of people. They are seed-sterile crops propagated clonally and this makes them vulnerable to a rapid spread of devastating diseases and at the same time hampers breeding improved cultivars. Although the socio-economic importance of bananas and plantains cannot be overestimated, they remain outside the focus of major research programs. This slows down the study of nuclear genome and the development of molecular tools to facilitate banana improvement.

The CGIAR genebank International Musa Germplasm Transit Centre (ITC) currently holds 1617 banana accessions from 38 countries as an in vitro collection, backed-up by a cryopreserved collection to safeguard global Musa diversity in perpetuity. The ITC also serves as a vital safety backup and transit centre for national banana genebanks and ensures that germplasm is clean of pests and diseases and freely available under the International Treaty on Plant Genetic Resources for Food and Agriculture. In more than 35 years of activity, the ITC has distributed over 18,000 banana accession samples to researchers and farmers in 113 countries. Ex situ conservation of vegetatively-propagated crops such as banana poses very particular challenges. Maintaining the ITC genebank is labor intense and costly. Efficiencies are sought through research and development of techniques on detecting viruses, the genetic integrity of accessions, and on innovative means of safeguarding banana diversity, such as conserving populations of wild species by seed banking. Although the conservation of global banana diversity is the main objective of the ITC, significant value comes from its holistic approach to better understand and promote its germplasm through numerous research activities and resources. Techniques for morphological and molecular characterization serve to identify and describe the collection, while also determining what gaps should be filled by collecting missions with national partners. The evaluation of desirable agronomic traits inherent in Musa spp. are investigated by a high-throughput phenotyping platform, which helps breeding programs to select cultivars resistant or tolerant to biotic and abiotic stresses. Genomic and bioinformatic studies of several banana wild relatives greatly enhance our understanding of Musa genetic diversity, links to important phenotypic traits and bring new methods for management of the collection. Collectively, these research activities produce enormous amounts of data that require curation and dissemination to the public. The two information systems at the ITC, Musa Genebank Management System and the Musa Germplasm Information System, serve to manage the genebank activities and to make public germplasm-related data for over 30 banana collections worldwide, respectively. By implementing the 10-year workplan set out in the Global Strategy for the Conservation and Use of Musa Genetic Resources, the network MusaNet supports Musa researchers and stakeholders, including the ITC, and most importantly, links to the world’s banana-producing countries via three regional banana networks.

The international collections of plant genetic resources for food and agriculture (PGRFA) hosted by 11 CGIAR Centers are important components of the United Nations Food and Agriculture Organization’s global system of conservation and use of PGRFA. They also play an important supportive role in realizing Target 2.5 of the Sustainable Development Goals. This paper analyzes CGIAR genebanks’ trends in acquiring and distributing PGRFA over the last 35 years, with a particular focus on the last decade. The paper highlights a number of factors influencing the Centers’ acquisition of new PGRFA to include in the international collections, including increased capacity to analyze gaps in those collections and precisely target new collecting missions, availability of financial resources, and the state of international and national access and benefit-sharing laws and phytosanitary regulations. Factors contributing to Centers’ distributions of PGRFA included the extent of accession-level information, users’ capacity to identify the materials they want, and policies. The genebanks’ rates of both acquisition and distribution increased over the last decade. The paper ends on a cautionary note concerning the potential of unresolved tensions regarding access and benefit sharing and digital genomic sequence information to undermine international cooperation to conserve and use PGRFA.

High-throughput sequencing (HTS) technologies have brought tremendous improvements in the ability to detect plant viruses and have great potential for application in virus routine diagnostics. The performance criteria of an HTS test need therefore to be estimated and compared with traditional virus indexing tests before it can be used in routine diagnostics. In this study, 78 Musa accessions previously indexed for viruses by molecular tests and/or electron microscopy were tested individually or in pools using an HTS protocol based on total RNA sequencing. The analytical sensitivity of HTS and RT-PCR was also compared by independent testing on serial dilutions of RNA extracts. In total, 136 libraries were sequenced in five batches, and the sequences were analyzed for virus detection. The external alien control, a wheat sample infected by barley yellow dwarf virus, monitored the contamination burden and determined an adaptative detection threshold. Overall, the HTS test displayed a better analytical sensitivity than the RT-PCR and a better inclusivity than the classical indexing protocol, as distant isolates and new viral species were only detected by the HTS test. The repeatability and reproducibility of virus detection were both 100%, although differences in number of sequencing reads per virus were observed between replicates. The diagnostic sensitivity was very high, but false positive results were observed. Finally, the results also underlined the need for expert judgement in the interpretation of the results. In conclusion, the HTS test with an alien control and completed by expert evaluation fulfilled the criteria of the virus indexing protocol for Musa germplasm. [ ] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Ensete glaucum (2n = 2x = 18) is a giant herbaceous monocotyledonous plant in the small Musaceae family along with banana (Musa). A high-quality reference genome sequence assembly of E. glaucum is a resource for functional and evolutionary studies of Ensete, Musaceae, and the Zingiberales. Using Oxford Nanopore Technologies, chromosome conformation capture (Hi-C), Illumina and RNA survey sequence, supported by molecular cytogenetics, we report a high-quality 481.5 Mb genome assembly with 9 pseudo-chromosomes and 36,836 genes. A total of 55% of the genome is composed of repetitive sequences with predominantly LTR-retroelements (37%) and DNA transposons (7%). The single 5S ribosomal DNA locus had an exceptionally long monomer length of 1,056 bp, more than twice that of the monomers at multiple loci in Musa. A tandemly repeated satellite (1.1% of the genome, with no similar sequence in Musa) was present around all centromeres, together with a few copies of a long interspersed nuclear element (LINE) retroelement. The assembly enabled us to characterize in detail the chromosomal rearrangements occurring between E. glaucum and the x = 11 species of Musa. One E. glaucum chromosome has the same gene content as Musa acuminata, while others show multiple, complex, but clearly defined evolutionary rearrangements in the change between x= 9 and 11. The advance towards a Musaceae pangenome including E. glaucum, tolerant of extreme environments, makes a complete set of gene alleles, copy number variation, and a reference for structural variation available for crop breeding and understanding environmental responses. The chromosome-scale genome assembly shows the nature of chromosomal fusion and translocation events during speciation, and features of rapid repetitive DNA change in terms of copy number, sequence, and genomic location, critical to understanding its role in diversity and evolution.

Bananas (Musa spp.) are an important crop worldwide. Most modern cultivars resulted from a complex polyploidization history that comprised three whole genome duplications (WGDs) shaping the haploid Musa genome, followed by inter- and intra-specific crosses between Musa acuminata and M. balbisiana (A and B genome, respectively). Unresolved hybridizations finally led to banana diversification into several autotriploid (AAA) and allotriploid cultivars (AAB and ABB). Using transcriptomic data, we investigated the impact of the genome structure on gene expression patterns in roots of 12 different triploid genotypes covering AAA, AAB and ABB subgenome constitutions. We demonstrate that (i) there are different genome structures, (ii) expression patterns go beyond the predicted genomic groups, and (iii) the proportion of the B genome influences the gene expression. The presence of the B genome is associated with a higher expression of genes involved in flavonoid biosynthesis, fatty acid metabolism, amino sugar and nucleotide sugar metabolism and oxidative phosphorylation. There are cultivar-specific chromosome regions with biased B:A gene expression ratios that demonstrate homoeologous exchanges (HE) between A and B sub-genomes. In two cultivars, aneuploidy was detected. We identified 3674 genes with a different expression level between allotriploid and autotriploid with ~ 57% having recently duplicated copies (paralogous). We propose a Paralog Inclusive Expression (PIE) analysis that appears to be suitable for genomes still in a downsizing and fractionation process following whole genome duplications. Our approach allows highlighting the genes with a maximum likelihood to affect the plant phenotype. This study on banana is a good case to investigate the effects of alloploidy in crops. We conclude that allopolyploidy triggered changes in the genome structure of a crop and it clearly influences the gene.