S02 - Session O6 - Cryopreservation protocol optimization and procedure establishment for long-term storage of cassava and yam international clonal crop collections

Authors: Badara Gueye *, Olubimpe Obisean, Busola Bankole, Motunrayo Olagunju, Michael T. Abberton

Clonally propagated crop collections such as yams ( Dioscorea spp.), cassava ( Manihot esculenta CRANTZ), are maintained at the genetic resources center of the International Institute of Tropical Agriculture (IITA); in the field and in vitro genebanks. However, clonal diversity is at risk of loss because of several constraints, such as adverse environmental conditions, pests, diseases and genetic contaminations in the field or plant ageing, handling errors, pathogen contaminations, and higher epigenetic variations when conserved in vitro . Using liquid nitrogen at -196░C, cryopreservation is the most reliable and cost-effective conservation method for clonal crop collections long-term safeguarding. It also allows effective and standard germplasm safety duplication. Cryopreservation requires, among other criteria, an optimal protocol and reliable procedure that can ensure high standards, consistent plantlets recovery, on which the efficiency of any cryopreservation project is evaluated. This study aims to determine pertinent criteria for accessions cryopreservation and establish key parameters to make cassava and yam cryobanking operational at IITA. Experiments on selected cassava and yam accessions were carried out to improve meristem regrowth rate via meristem and multiplication culture media optimization and use oh antioxidants (Lipoic acid, Ascorbic, acid and acid glutathione). Also, virus cleaning protocols (meristem culture, thermo- and chemo-treatments) were tested on ten accessions each for cassava and yam and cryogenic methods (droplet vitrification and V-cryo plate) evaluated to determine the most efficient one in terms of meristem regrowth rate. The results of this study allowed to set up optimal cryopreservation protocol for cassava and yam germplasm and guide to validate an appropriate procedure with four defined criteria before an accession can be cryobanked. Setting up a reliable cryobanking procedure, including optimized protocols, was crucial to implement cryobanking at IITA since 2017, which was integrated into the institute's global conservation strategy for collection maintenance in perpetuity and sustainable use for more resilient and productive agriculture.