In his book Essay on population Malthus’s 1798 predicted that population growth will soon outpace food production. Ecologist Paul Ehrlich’s 1968 wrote in his book: The Population Bomb predicted that the world will undergo famines in 1970s, hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. It is too late!!! It did not happen. However by some surprise or scientific achievements this did not happen but to say it will never happen will be far from truth. Wars are destroying biodiversity regionally in different parts of the globe. Countries such as India had exceeded their “carrying” capacity. 100,000 plants representing 1/3rd of plant species are threatened. Around 100 species are getting extinct each year and 32 million ha of forest land is destroyed world wide in one year. In order to preserve the genotypes, plant species several efforts have now been taken at the level of Europe in major way , in middle east, in USA and also in developing world.
Since the 1970s large number of land races and wild relatives are sampled and stored ex situ presently _about 6 million samples are held in national, regional, internationaland private gene bank collections.
What is difference in in situ and ex situ conservation ?.
In situ : It is conservation of plants in their ‘normal’ habitat like preserving plants in rainforests, gardens and farms.
In contrast to this Ex Situ conservation is to take plants or plant material tissue or even genes and conserve them in
a) Semi-static method
Main justification for this method is :
Capturing current genetic diversity/species diversity. It is readily available for use and research and it complements in situ conservation. This includes: Field collection, Botanical gardens Seed collections ; In vitro collection; Normal growth ; Slow growth and Cryopreservation(-196°C)
Some of the plants parts which can be stored include: Orthodox seeds; Seeds be maintained under conditions in which life processes are minimized. This can be achieved by
a) Low MC/Low temperature b)Stored safely for a number of years c) Little loss in Genetic Diversity , genetic integrity and viability, Storage facilities extend viability of seeds, Efficient&reproducible technique for orthodox seed species.
However considerable progress has been made in alternative methods of storage with respect to Conservation of Tissues/Cells for difficult-to-conserve species, recalcitrant seeds, Vegetatively propagated plant species, and Large seeds. For some species only option is : Cryopreservation. Rapid progress has been made and it has great potential for conservation.
(DNABanks) have to undergo following steps :
1. Receiving vegetative material from field genebank/ex situ stands/collecting mission 2. Processing of the material for disease indexing 3. Therapy and quarantine, if needed 4. Healthy and clean material for culturing 5. Cryopreserved base genebank (long term) and/or 6 In vitro active genebank in slow growth. Thus In vitro genebanks must have protocols for tissue culture , their successful regeneration , and transfer to soil, genetic stability, cryopreservation of cultured material , Vitrification or encapsulation.
What is cryopreservation ?
Storage of living tissues at ultra-low temperatures (-196°C)
_ Cryopreservation procedures are now available for about 150-200 different plant species. However for each species and tissue type, the cryopreservation protocol needs to be empirically adapted.
Cryopreservation can be used for
• Conservationof plant germ plasm
• Vegetatively propagated species (root and tubers, ornamental, fruit trees)
• Recalcitrant seed species (Howea, coconut, coffee)
• Conservation of tissue with specific characteristics
• Medicinaland alcohol producing cell lines
• Genetically transformed tissues
• Transformation/ Mutagenesis competent tissues (ECSs)
• Eradication of viruses (Banana, Plum)
• Conservation of plant pathogens (fungi, nematodes)
Steps of conservation include:
• Use of immature zygotic embryos (not for vegetatively propagated species)
• Addition of inhibitors or retardants
• Manipulating storage temperature
• Mineral oil overlay
• Reduced oxygen tension
• Defoliation of shoots
Synthetic Seeds provide easy method of storage of clonally propagated or Species with recalcitrant seed, Encapsulation of shoot‑tips & somatic embryos, in semi‑solid material ‘Beads' using sodium alginate. With current pace of development production & storage of artificial seeds may be a routine practice soon.