🦹🏼‍♀️ Germplasm Activities

👉🏻 There are six important activities related to plant genetic resources.

1. Exploration and Collection
2. Conservation
3. Evaluation
4. Documentation
5. Multiplication and Distribution
6. Utilization

1. Exploration

• Exploration refers to collection trips and collection refer to tapping of genetic diversity from various sources and assembling the same at one place. The exploration and collection is a highly scientific process. This process takes into account six important items, viz,
  • sources of collection
  • priority of collection
  • agencies of collection
  • methods of collection
  • methods of sampling
  • sample size.

✅ Merits

• Collection helps in tapping crop genetic diversity and assembling the same at one place.
• It reduces the loss of genetic diversity due to genetic erosion.
• Sometimes, we get material of special interest during exploration trips.
• Collection also helps in saving certain genotypes from extinction.

❌ Demerits

• Collection of germplasm especially from other countries, sometimes leads to entry of new diseases, new insects and new weeds.
• Collection is a tedious job.
• Collector, sometimes has encounter with wild animals like elephants, tigers etc.
• Transportation of huge collections also poses difficulties in the exploration and collection.

Germplasm Conservation

• Conservation refers to protection of genetic diversity of crop plants from genetic erosion. or
• Germplasm conservation refers to maintain the collected germplasm in such a state that there is minimum risk for its loss and that either it can be planted directly in the field or it can be prepare for planting with relative ease whenever necessary.
• There are two important methods of germplasm conservation or preservation viz.,
  1. In situ conservation
  2. Ex situ conservation

1. In situ conservation

• Conservation of germplasm under natural habitat is referred to as in situ conservation.
• This is achieved by protecting this area from human interference. Such an area is often called as natural park, biosphere reserve or gene sanctuary.

Gene Sanctuaries

• The genetic diversity is sometimes conserved under natural habitat. The 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 also Known As Natural Park or Biosphere Reserve.
• A gene sanctuary is best located within the centre of origin of crop species concerned, preferably covering the microcenter with in the centre of origin.
• 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 sanctuary for conservation of wild relatives of Coffee was setup in 1984.
• NBPGR, New Delhi is making attempts to establish gene sanctuaries in Meghalaya for Citrus and in the North-Eastern region for Musa, Citrus, Oryza, Saccharum and Mengifera genus.

✅ Merits

• A gene sanctuary not only conserves the existing genetic diversity present in the population, it also allows evolution to continue. As a result, new alleles and new gene combinations would appear with time.
• The risks associated with ex situ conservation are not operative.

❌ Disadvantages

• Each protected area will cover only very small portion of total diversity of a crop species, hence several areas will have to be conserved for a single species.
• The management of such areas also poses several problems.
• This is a costly method of germplasm conservation

Ex situ conservation

• Conservation of germplasm away from its natural habitat is called ex situ germplasm conservation.

✅ Merits

• It is possible to preserve entire genetic diversity of a crop species at one place.
• Handling of germplasm is also easy.
• This is a cheap method of germplasm conservation

👉🏻 Seed Collection

• Preservation in the form of seed is the most common and easy method, relatively safe, requires minimum space and easy to maintain.
• Glass, tin or plastic containers are used for preservation and storage of seeds. The seed can be conserved under long term, medium term and short-term storage conditions.

• Roberts in 1973 classified seeds on the basis of their storability, into two major groups. viz.,

1. Orthodox Seeds: Seeds of this type can be dried to low moisture content of 5% and stored at a low temperature without losing their viability are known as orthodox seeds. Most crop seeds belong to this category. Such seeds can be easily stored for long periods; their longevity increases in response to lower humidity and storage temperature. Eg. Wheat, Rice, Corn, Chickpea, Cotton, Sunflower etc.
2. Recalcitrant Seeds: The viability of this group of seeds drops drastically if their moisture content is reduced below 12-30%. Seeds of many forest and fruit trees, and of several tropically crops like Citrus, mango, coffee, cocoa, rubber, oil palm, jackfruit, etc. belong to this group. Such seeds present considerable difficulties in storage. They require in situ conservation.

3. Evaluation

• Evaluation refers to screening of germplasm in respect of morphological, genetical, economic, biochemical, physiological, pathological and entomological attributes.
• Evaluation requires a team of specialists from the disciplines of plant breeding, physiology, biochemistry, pathology and entomology.
• First of all a list of descriptors (characters) for which evaluation has to be done is prepared. This task is completed by a team of experts from IPGRI, Rome, Italy.
• The descriptors are ready for various crops.
• The evaluation of germplasm is down in three different places, viz., (1) in the field, (2) in green house, and (3) in the laboratory.

4. Documentation

• It refers to compilation, analysis, classification storage and dissemination of information.
• In plant genetic resources, documentation means dissemination of information about various activities such as collection, evaluation, conservation, storage and retrieval of data.
• Now the term documentation is more appropriately known as information system. Documentation is one of the important activities of genetic resources.
• Large number of accessions are available in maize, rice, wheat, sorghum, potato and other major crops.
• About 7.3 million germplasm accessions are available in 200 crops species. Handling of such huge germplasm information is only possible through electronic computers.

5. Distribution

• The specific germplasm lines are supplied to the users on demand for utilization in the crop improvement programmes.
• Distribution of germplasm is the responsibility of the gene bank centres.
• The germplasm is usually supplied to the workers who are engaged in research work of a particular crop species.
• Supplied free of cost to avoid cumbersome work of book keeping.
• The quantity of seed samples depends on the availability of seed material and demands
• Proper records are maintained about the distribution of material.
• It helps in acclimatization and purification of the material.

6. Utilization

• It refers to use of germplasm in crop improvement programmes. The germplasm can be utilized in various ways.
• The uses of cultivated and wild species of germplasm are briefly discussed below:
• Cultivated Germplasm
  • It can be used in three main ways: (1) as a variety, (2) as a parent in the hybridization, and (3) as a variant in the gene pool.
• Wild Germplasm
  • It is used to transfer resistance to biotic and abiotic stresses, wider adaptability and sometimes quality such as fibre strength in cotton.

Organizations associated with germplasm

• International Plant Genetic Resources Institute, (IPGRI) Rome, Italy

• National Bureau of Plant Genetic Resources, (NBPGR) New Delhi

Genetic Erosion

• Genetic erosion refers to loss of genetic diversity between and within populations of the same species over a period of time. or
• Gradual reduction in genetic diversity in the populations of a species, due to elimination of various genotypes, is called genetic erosion.
• Thus, genetic erosion leads to reduction of the genetic base of a species due to human intervention and environmental changes.
• There are five main reasons of genetic erosion:
  • Replacement of land races with improved cultivars: The main features of modern cultivars are high yield, uniformity, narrow genetic base and narrow adaptability. On the other hand land races and primitive cultivars have more genetic diversity, broad genetic base, wider adaptability and low yield potential. Thus replacement of land races with modern cultivars has resulted in reduction in genetic diversity because land races are disappearing.
  • Modernization of agriculture: Clean and modern agriculture, Improved crop management practices has resulted in the elimination of wild and weedy forms of many crops. These weedy forms enhance the genetic diversity through introgression of genes from crop to weedy forms and weedy forms to crop plants.
  • Extension of farming into wild habitats: It has resulted in destruction of wild relatives of various crops resulting in reduction of their genetic diversity.
  • Grazing into wild habitats: Grazing of animals in the wild habitat also reduces genetic diversity by destroying the wild and weedy forms of crop plants.
  • Developmental activities like Hydroelectric projects, growth of towns, cities, roads, air ports and industrial areas also lead to genetic erosion of crop plants, because vast areas are cleaned for such activities.

Extinction

• Extinction refers to permanent loss of a crop species due to various reasons.

Introgression

• Transfer of few genes from one species into the full diploid chromosome complement of another species.

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 banks, as plants growing in the field.
• Types:
  • Seed gene banks
  • Plant or field gene banks
  • Meristem gene banks
  • Cell and organ gene banks and
  • DNA gene banks