Unraveling the genetic diversity held in genebanks on a large scale is underway, due to advances in Next-generation sequence (NGS) based technologies that produce high-density genetic markers for a large number of samples at low cost. Genebank users should be in a position to identify and select germplasm from the global genepool based on a combination of passport, genotypic and phenotypic data. To facilitate this, a new generation of information systems is being designed to efficiently handle data and link it with other external resources such as genome or breeding databases. The Musa Germplasm Information System (MGIS), the database for global ex situ-held banana genetic resources, has been developed to address those needs in a user-friendly way. In developing MGIS, we selected a generic database schema (Chado), the robust content management system Drupal for the user interface, and Tripal, a set of Drupal modules which links the Chado schema to Drupal. MGIS allows germplasm collection examination, accession browsing, advanced search functions, and germplasm orders. Additionally, we developed unique graphical interfaces to compare accessions and to explore them based on their taxonomic information. Accession-based data has been enriched with publications, genotyping studies and associated genotyping datasets reporting on germplasm use. Finally, an interoperability layer has been implemented to facilitate the link with complementary databases like the Banana Genome Hub and the MusaBase breeding database. Database URL: https://www.crop-diversity.org/mgis/
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.
Core activities of genebank operations include the preservation of germplasm identity and maintenance of genetic integrity. Some organisms such as banana are maintained by tissue culture that can foster accumulation of somatic mutations and loss of genetic integrity. Such changes can be reflected in their genome structure and thus be revealed by sequencing methods. Here, we propose a protocol for the detection of large chromosomal gains and/or losses that was applied to in vitro banana accessions with different levels of ploidy. Mixoploidy was detected in triploid (3x) accessions with chromosomal regions being diploid (2x) and tetraploid (4x) and in diploid accessions (2x) where large deletions resulted in partial haploidy (1x). Such abnormal molecular karyotypes can potentially explain phenotypic aberrations observed in off type material. With the affordable cost of Next Generation Sequencing (NGS) technologies and the release of the presented bioinformatic pipeline, we aim to promote the application of this methodology as a routine operation for genebank management as an important step to monitor the genetic integrity of distributed material. Moreover, genebank users can be also empowered to apply the methodology and check the molecular karyotype of the ordered material.
An amendment to this paper has been published and can be accessed via the original article.
Somaclonal variation describes random cellular changes in plants regenerated through tissue culture. It occurs in certain crops that undergo micropropagation and has been recorded in different explant sources, from leaves and shoots to meristems and embryos. In banana (Musa spp.), a clonal crop conserved in vitro, somaclonal variation has been observed after prolonged periods in tissue culture, resulting from an increase in subcultures performed on a given clone. According to scientific literature, variants, or off-types, often show characteristics such as abnormal growth and flower or fruit defects in frequencies ranging from 1% to 32%. This variation poses a problem for gene bank managers, whose mandate is to maintain the genetic integrity of their collections for research and breeding. In the case of the Bioversity International Musa Germplasm Transit Centre (ITC), stress during the in vitro process is minimized by various techniques and plants are regenerated after 10 years, making it a long and costly process. Identifying somaclonal variation at an early stage would be an ideal solution; however, this requires suitable molecular markers. Recent studies revealed that techniques such as direct DNA sequencing and single nucleotide polymorphisms (SNPs) are able to detect the underlying factors of somaclonal variation and are becoming more accessible. On the other hand, somaclonal variation can be beneficial as it allows the natural development of new varieties and supplies genetic stocks used for future genetic studies. Harnessing the diversity of somaclones is easier, faster and cheaper compared with other methods of crop improvement, although it is also less predictable. So far, variants of crops such as apple, strawberry, potato and banana have been successfully adopted into global markets. In this chapter, we will discuss how to minimize the adverse effects of somaclonal variation while maximizing its benefits for greater crop diversity, with a particular focus on banana.
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