The field verification activity: a cooperative approach to the management of the global Musa in vitro collection at the International Transit Centre

The International Transit Centre (ITC) (Bioversity International, KULeuven, Belgium) currently holds the largest ex situ collection of Musa germplasm, partly available to researchers, breeders and the larger Musa community via the online ordering system in the Musa Germplasm Information System (MGIS). It is thus extremely important that somaclonal variants and mislabeled accessions are removed from the collection to ensure that users have access to a valid and reliable source of Musa genetic resources. Through Bioversity's Field Verification (FV) activity, a combination of morphological and molecular characterization along with a validation by a panel of experts is used to assess the genetic integrity of the Musa accessions held at ITC. The FV includes ploidy determination and SSR and DArT fingerprinting data (produced by the Musa Genotyping Centre, Institute of Experimental Botany, Czech Republic and DArT P/L, Australia) combined with minimum descriptors and standard photographs of accessions in partners' field collections. The compiled molecular and morphological data are sent to a panel of ten Musa taxonomists in charge of the validation of the accessions' genetic integrity. This workflow allows the quality control of the germplasm available to users while adding value to the content of the ITC by producing standardized characterization data. Status has been determined for 370 of 832 accessions sent to field partners, and the first round will be completed when all virus-free accessions are validated. Results thus far indicate that most of the in vitro collection is genetically stable, supporting the use of the tissue culture protocols; however, questions have arisen regarding the optimal duration after which accessions should be genetically verified; how the work can be better organized and communicated, and the implications of the type of somaclonal variations observed. A large body of information has been generated and is accessible to the public via MGIS, including documentation (data and photographs) for 540 accessions, covering 63% of the collection currently available for distribution. This information adds significant value to the ITC collection and is a clear asset to the Musa community.