Gene Sanctuaries and Gene Banks
The genetic diversity is sometimes conserved under natural habitat. In other words, areas of great genetic diversity are protected from human interference. These protected areas in natural habitat are referred to as gene sanctuaries. Gene sanctuary is generally established in the centres of diversity or microcenter. Gene sanctuary is Also Known As Natural Park or biosphere reserve. India has setup its first gene sanctuary in the Garo Hills of Assam for wild relatives of citrus. Efforts are also being made to setup gene sanctuaries for banana, sugarcane, rice and Mango. In Ethiopia gene sanctuaries for conservation of wild relatives of coffee was setup in 1984. Gene sanctuaries have two main advantages. Firstly, it protects the loss of genetic diversity caused by human intervention. Secondly, it allows natural selection and evolution to operate. There are two main drawbacks of gene sanctuary. Firstly, entire variability of a crop species can not conserved. Secondly , its maintenance and establishment is a difficult task. It is a very good method of in Situ Conservation.
Gene bank refers to a place or organisation where germplasm can be conserved in living state. Gene banks are also known as germplasm banks. The germplasm is stored in the form of seeds, pollen or in vitro cultures, or in the case of a field gene bank, as plants growing in the field. Gene banks are mainly of two types, viz: 1) Seed gene banks, and 2) Field gene banks. These are briefly discussed below:
1. Seed Gene Bank:
A place where germplasm is conserved in the form of seeds is called seed gene bank. Seeds are very convenient for storage because they occupy smaller space than whole plants. However, seeds of all crops can not be stored at low temperature in the seed banks. The germplasm of only orthodox species (whose seed can be dried to low moisture content without losing variability) can be conserved in seed banks. In the seed banks, there are three types of conservation, viz. 1) Short term, 2) Medium term, 3) Long term. Base collections are conserved for long term (50 years or more) at 18 or 20 0C. Active collections are stored for short term (3-5 years) at 5-10 0 C. The main advantages of gene banks are as follows:
1. Large number of germplasm samples or entire variability can be conserved in a very small space.
2. In seed banks, handling of germplasm is easy.
3. Germplasm is conserved under pathogen and insect free environment.
There are some disadvantages of germplasm conservation in the seed banks. These are listed below:
1. Seeds of recalcitrant species can not be stored in seed banks.
2. Failure of power supply may lead to loss of viability and there by loss of germplasm.
3. It requires periodical evaluation of seed viability. After some time multiplication is essential to get new or fresh seeds of storage.
2. Field Gene Banks:
Field gene banks also called plant gene banks are areas of land in which germplasm collections of growing plants are assembled. This is also exsitu conservation of germplasm. Those plant species that have recalcitrant seeds or do not produce seeds readily are conserved in field gene bank. In field gene banks, germplasm is maintained in the form of plants as a permanent living collection. Field gene banks are often established to maintain working collections of living plants for experimental purposes. They are used as source of germplasm for species such as coconut, rubber, mango, cassava, yam, and cocoa. Field gene banks have been established in many countries for different crops.
Field Gene Banks in Some Countries:
Name of Country
Crop Species for which Field Gene Bank is Established
Oil palm has been conserved on 500 hectares.
Earmarked 1000 hectares area for coconut and other perennial crops.
South East Asian germplasm of banana has been conserved.
Global collection of coconut has been conserved in Andaman ad Nicobar.
Field gene banks have some advantages and disadvantages which are discussed below: There are two main advantages.
1. It provides opportunities for continuous evaluation for various economic characters.
2. It can be directly utilized in the breeding programmes.
There are three main demerits of field gene banks as given below:
1. Field gene banks can not cover the entire genetic diversity of a species. It can cover only a fraction of the full range of diversity of a species.
2. The germplasm in field gene banks is exposed to pathogen and insects and some times is damaged by natural disasters such as bushfires, cyclones, floods , etc.
3. Maintenance of germplasm in the field gene banks is costly affair.
Meristem Gene Banks:
Germplasm of asexually propagated species can be conserved in the form of meristem. This method is widely used for conservation and propagation of horticultural species. In vitro method can be used in two ways, first, for storage of tissue under slow growth conditions. Second, for long term conservation of germplasm by cryopreservation. In cryopreservation, the tissues are stored at very low temperatures i.e. at 196 0C in liquid nitrogen. At these temperatures, all biological processes virtually come to a stop.
Based on status of Research Institutes, gene banks are again of two types, viz. 1) National gene banks, and 2) International or global gene banks . National gene banks are maintained by each country and global gene banks are located in International Crop Research Institutes/ Centres. In India, gene banks are maintained by concerned crop research institute of ICAR. National Bureau of Plant Genetic Resources, New Delhi is also maintaining germplasm of various field crops.