Principles of Plant Breeding (2+1)

Gene Banks

• Gene bank refers to a place or organization 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,

  (1) Seed gene banks
  (2) Field gene banks

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, and (3) Long-term.
Base collectionsare conserved for long term (50 years or more) at -18 or -20°C.
Active collections are stored for medium term (10-15 years) at zero degreesCelsius.
Working collectionis stored for short term (3-5 years) at 5-10°C.

Advantages of gene banks
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.
 

Disadvantages
1. Seeds of recalcitrant species can not be stored in seed banks.
2. Failure of power supply may lead to loss of viability and thereby loss of germplasm.
3. It requires periodical evaluation of seed viability. After some time multiplication is essential to get new or fresh seeds for 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 called ex-situ conservation of germplasm. Those plant species that have recalcitrant seeds or do not produce seeds readily are conserved in field gene banks. 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
Established field gene banks

Name of country	Crop species for which field gene bank is established
Malaysia	Oil palm has been conserved on 500 ha.
Indonesia	Earmarked 1000 ha. Area for coconut and other perennial crops.
Philippines	South East Asian germplasm of banana has been conserved.
India	Global collection of coconut has been conserved to Andman and Nicobar.

Advantages
1. It provides opportunities for continuous evaluation for various economic characters.
2. It can be directly utilized in the breeding programme.

Disadvantages
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 pathogens and insects and sometimes is damaged by natural disasters such as bushfires, cyclones, floods, etc.
3. Maintenance of germplasm in the field gene banks is costly.