The field bank of the Genetic Resources Center is located at the International Institute of Tropical Agriculture, IITA Headquarters in Ibadan. Here clonally propagated crops are conserved comprising of cassava, yam and the musa species. For safety backup purpose amongst other reasons, a number of accessions of these different crops are also conserved in the in vitro bank.
There are about 3400 accessions of cassava conserved in the field bank and these are regenerated every two years. There is a large wild cassava relatives’ field which has been serving as the bedrock for some of the breeding activities of cassava breeders in IITA. In the yam field, about 3200 accessions are being conserved as well and these are regenerated once every year. Harvested yam tubers are stored briefly at GRC yam barn before they are transferred to the cold store where they are maintained till another planting time for the new season. There is an ex situ conservation of some wild yam relatives and these largely were brought in from the in situ conservation in IITA campus.
The different ecological zones from which these accessions were sourced is one of the factors that necessitated the use of outstations for those that perform poorly at IITA Ibadan station. A careful selection of an outstation that offers an environment that comes close to the conditions found in the places of origin of these accessions serves the good purposes of repository and pre-breeding research activities.
In the musa field of the field bank of GRC, there are about 350 accessions that have been conserved using the same location for several years. No conservation is done in any outstation for the collections in the musa field bank yet but as in the case of other clonally propagated crops in the field bank, there is safety backup for some of the accessions in the in vitro bank already.
CHOICE OF LOCATION AND LAND PREPARATION
GRC makes every effort to plant under agro-ecological conditions that are as similar as possible to the environment were the germplasm was collected. The site is carefully considered so as to minimize the risk of flooding, pests and diseases and human intervention. The site for field collections is under secured land-tenure and allows for further expansion should the collection increase in size. The site of the field collection is easily accessible to staff and has access to water for timely irrigation.
FIELD MARKING AND LABELING
The field is divided into plots separated by 1.5 m wide alleys. Each plot is 2.5 m in width and its length depends on the field dimensions. Measuring tape and bamboo or wooden pegs are used to measure, mark and demarcate the beginning of each plot. There is a distance of 1 m between ridges.
GERMPLASM SELECTION AND PREPARATION
Healthy stem cuttings, plantain or banana suckers and tubers are collected from the existing field bank. Selected stems, tubers, and suckers are free from cuts and visible attack by pathogens (viruses, bacteria, and insects).
Field Bank Monitoring
The field bank is monitored at least every day or once a week. The following indicators are informative of the health status: termites’ presence, changes in leaf color, insect incidence, signs of wilting (plant drooping) or severe chlorosis (plants turning yellow due to disease or lack of necessary nutrients). Any of these signs is reported to the manager for immediate action. Once an issue has been reported, daily observation may be needed until the situation is back to normal to prevent the loss of the material or accession.
REGENERATION AND PROPAGATION
Regeneration is the renewal of germplasm accessions by sowing seeds or planting vegetative materials and harvesting the seeds or plant materials which will posses the same characteristics as the original population. Cassava is regenerated after 2 years, musa is every three years and Yam is every year in GRC.
In situ conservation: Conservation of germplasm in ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings. Field and screen house Field genebanks are mostly used for the conservation of clonal crops.
Ex situ conservation: plant material under artificial conditions (other than their natural environment), to efficiently and effectively guarantee its longevity viability and availability. such as in vitro and cryo banks