The genetic diversity of the world's major food crops, once considered virtually limitless, is fast disappearing in nature. The causes are well-known: the predominance of modern crop varieties, changes in consumer preferences, and loss of habitat each contribute to a trend that could well undermine the planet’s food supply.
Dryland areas are especially vulnerable to genetic erosion as they lack resiliency and are now experiencing the early impact of global climate change. These factors - in combination with poverty, human migration and political instability – tend to accelerate the problem.
To safeguard the biodiversity of food crops grown in the semi-arid tropics, ICRISAT maintains one of the world’s largest germplasm repositories, a "genebank" containing more than 120,000 accessions. The facility, serves as a world repository for sorghum, pearl millet, chickpea, pigeonpea, groundnut and six of the lesser-known millet species – finger millet, foxtail millet, proso millet, kodo millet, little millet and barnyard millet. Maintained at low temperatures to preserve viability, the collection contains hundreds of wild species as well as many farmer-developed varieties or land races that are fast disappearing in nature.
Located at the Center’s headquarters in Patancheru, India, the genebank was designed to withstand natural disasters and has numerous backup systems to keep the collection secure. In addition, three smaller facilities have been established in Africa to serve national and regional research programs and provide additional safeguards. Nearly 100,000 duplicate samples are stored at the Svalbard Global Seed Vault in Norway under the auspices of the Global Diversity Trust and the Nordic Genebank.
The purpose of maintaining a genebank is not to simply safeguard genetic diversity, but to encourage its use. To that end, researchers have characterized nearly 95% of the collection for morpho-agronomic traits, and a greater part for stress tolerance, pest and disease resistance and nutrition. Each accession maintained in the collections is freely available to researchers at other institutions. Thus far, more than 720,000 samples have been distributed to users in 146 countries.
More about genetic resources:
- Assessing diversity: Plant genetic resources specialists stress that assessments of the diversity maintained in germplasm collections is essential for the systematic management of and utilization of germplasm in breeding programs. To that end, major investments have been made to assess the phenotypic and geographical pattern of diversity in ICRISAT mandate crops and small millets.
- Identification of geographic gaps: The identification of geographic and taxonomic gaps in collections is likely to play an important role in future exploration and collection efforts. Already, Center scientists have identified geographic gaps in the pearl millet collection and anticipate mounting future exploration efforts before these valuable resources are lost due to climate change or neglect.
- Stabilizing yield potential: Following the initial development of high yielding cultivars in recent years, further improvement in yield potential are likely to be slow and progress incrementally. At present, breeding efforts are directed mainly towards stabilizing yield potential and reducing the vulnerability of genetically uniform modern varieties to pests, diseases, changes in climatic conditions and consumer preferences .
- Raising yield ceiling: Landraces, exotics and wild relatives hold a wealth of alleles, which, if included in breeding programs could well raise yield ceilings and enhance stress resistance levels and the nutritional quality of dryland cultivars. Only a small proportion (<1%) of conserved germplasm has been used in crop improvement programs due to a lack of information on traits of economic importance that show genotype x environment interactions. A representative sample that more generally reflects the diversity of the Center’s entire collection could provide a cost effective way to maintain and facilitate enhanced use of germplasm in breeding programs.
- Core collections: ICRISAT’s “core collection” is a representative sample or subset, consisting of ~10% of total accessions capturing most of the available diversity in the Center’s collection of crop species. Core collections of chickpea, pigeonpea, groundnut, sorghum, pearl millet, finger millet, foxtail millet and proso millet have been developed to enhance the utilization of germplasm in crop improvement.
- Mini-core collections: Even core collections, however, have frequently proven too large to assess traits of economic importance that display genotype × environment interaction. To resolve this issue, ICRISAT scientists established the mini-core (core of core) collection concept (~10% of core, ~1% of entire collection). Mini-core collections provide crop breeders with a systematic, yet manageable entry point into global germplasm resources.
- Trait selection: In recent years, mini-core collections of dryland crops and finger and foxtail millets have been developed and evaluated for resistance/tolerance to biotic and abiotic stresses, as well as agronomic and quality traits for use in crop improvement. Molecular proliferation of mini core collections has in turn led to the identification of genetically diverse germplasm lines for use in crop improvement and trait mapping. Such collections have also been used to determine marker-trait associations.
- Reference sets: Composite collections capturing genetic diversity of global collections of chickpea, pigeonpea, groundnut, sorghum, pearl millet, finger millet and foxtail millet (500-3500 accessions) have been established and profiled with 20-50 SSR markers. Reference sets consisting of 200 to 400 genetically diverse accessions (including mini core collections) have been selected for utilization in crop improvement and genomics.
- Wild relatives: The potential of wild relatives to enhance resistance to biotic and abiotic stresses in cultivated species is well recognized. But wild relatives are agronomically undesirable and are rarely considered for enhancing agronomic traits. Rare exceptions include the transfer of novel genes from wild relatives of chickpea, groundnut and pigeonpea to enhance the agronomic traits of cultivated species.
Detailed information about ICRISAT-held collections is available on-line at http://www.icrisat.org/ and at Genesys web site http://www.genesys-pgr.org/