Everything you need to know about crop genetic resources and centers of diversity !
Q. 1. What do you mean by plant genetic resources?
Ans. Genetic material of plants which is of value as a resource for present and future generations of people is referred to as plant genetic resources.
Q. 2. What do you mean by gene pool?
Ans. The whole library of different alleles of a species or sum total of genes in a species is known as gene pool, also called germplasm, genetic stock and genetic resources.
Q. 3. Who coined the term gene pool?
Ans. The term gene pool was coined by Dobzhansky in 1951.
Q. 4. Who coined the term germplasm?
Ans. The term germplasm was first used by Weismann in 1883.
Q. 5. What are different kinds of germplasm?
Ans. Germplasm includes following plant materials:
(i) Land races
(ii) Obsolete cultivars
(iii) Modern cultivars
(iv) Homozygous breeding materials
(v) Wild races of cultivated species
(vi) Wild species
(vii) Mutants, etc.
Q. 6. What do you mean by land races?
Ans. Primitive cultivars which were selected and cultivated by farmers for many generations are called land races. Main features of land races are given below.
They have:
(i) More genetic diversity,
(ii) Wider adaptability and broad genetic base.
(iii) High degree of resistance to biotic and abiotic stresses.
Q. 7. What are main drawbacks of land races?
Ans. There are two main drawbacks of land races as follows:
(i) Produce of land races is less uniform.
(ii) Land races are low yielders.
Q. 8. What are obsolete cultivars?
Ans. Improved cultivars of the recent past are known as obsolete cultivars.
Q. 9. What are modern cultivars?
Ans. Currently cultivated high yielding varieties are known as modern cultivars. Modern cultivars are also known as improved cultivars or advanced cultivars. Modern cultivars constitute major part of working collectors and are extensively used in breeding programmes for developing productive cultivars.
Q. 10. What are different types of gene pool?
Ans. Based on degree of relationship, Harlan and de Wet (1971) divided the gene pool into following three groups:
(i) Primary gene pool
(ii) Secondary gene pool
(iii) Tertiary gene pool.
Q. 11. What is primary gene pool?
Ans. The gene pool in which inter-mating is easy and leads to production of fertile hybrids is known as primary gene pool. It includes genotypes (collections) of the same species and is designated as GP1.
Q. 12. What is secondary gene pool?
Ans. The genetic material which leads to partial fertility on crossing with primary gene pool is called secondary gene pool. It includes genotypes of related species and is designated as GP2.
Q. 13. What is tertiary gene pool?
Ans. The genetic material which leads to production of sterile hybrids on crossing with primary gene pool is called tertiary gene pool. It includes wild species of a crop and is designated as GP3.
Q. 14. What are different types of seed collections?
Ans. Based on use in crop improvement, seed collections are of following three types:
(i) Base Collections
(ii) Active Collections, and
(iii) Working Collections.
Q. 15. What do you mean by base collections?
Ans. Total accessions available in a crop species are known as base collections. These are used for long term storage. Seeds are stored at -18 or – 20°C. These are also known as principal collections.
Q. 16. What do you mean by active collections?
Ans. Collections which are actively utilized in the breeding programmes are called active collections. These are used for medium term (8-10 years) storage. Seeds are stored at 0°C.
Q. 17. What do you mean by working collections?
Ans. Collections which are frequently utilized by breeders in their crop improvement programmes are known as working collections. These are used for short term storage (3-5 years) and are stored at 5-10°C.
Q. 18. What are core collections?
Ans. A set of accessions derived from base collections to represent the genetic spectrum of variability in the whole collections are called core collections.
Q. 19. Who proposed idea of core collections?
Ans. The concept of core collections was proposed by Frankel in 1984.
Q. 20. What are various germplasm activities?
Ans. There are six important germplasm activities as given below:
(i) Exploration and Collection,
(ii) Conservation,
(iii) Evaluation,
(iv) Documentation,
(v) Distribution, and
(vi) Utilization.
Q. 21. What is in-situ conservation of germplasm?
Ans. Protection of genetic diversity of crop plants from genetic erosion is called conservation. It is of two types, viz. in-situ conservation and ex-situ conservation. Conservation of germplasm under natural habitat is called in- situ conservation. It requires establishment of biosphere reserve and national parks for protection of endangered species.
Q. 22. What is ex-situ conservation?
Ans. Conservation of germplasm in the gene banks is called ex-situ conservations.
It has following advantages:
(i) It helps in conserving biodiversity of a species at one place,
(ii) Handling of germplasm is easy,
(iii) It is cheap method of germplasm conservation.
Q. 23. Who classified seed into orthodox and recalcitrant groups?
Ans. Roberts (1973) classified seeds into two groups, viz. orthodox and recalcitrant for storage purposes.
Q. 24. What are orthodox seeds?
Ans. Seeds which can be dried to low moisture contents and stored at low temperature without losing their viability are known as orthodox seeds.
This group includes seeds of following crops:
Q. 25. What are recalcitrant seeds?
Ans. Seeds which show very drastic loss in viability with decrease in moisture content below 12 or 13% are called recalcitrant seeds. Seed of such crops cannot be stored in seed banks.
This group includes following crops:
Q. 26. When was plant introduction work started in India?
Ans. In India, plant introduction work was started in 1946 in the Division of Botany, IARI, New Delhi.
Q. 27. When was Division of Plant Introduction established in India?
Ans. In India, Division of Plant Introduction was establishes in 1961 under the leadership of Dr. Har Bhajan Singh at IARI, New Delhi.
Q. 28. What is NBPGR?
Ans. NBPGR refers to National Bureau of Plant Genetic Resources, New Delhi.
Q. 29. When was NBPGR established?
Ans. NBPGR was established in 1976 at IARI, New Delhi. Infact, in 1976, the Division of Plant Introduction was elevated to the status of Independent Institute known as National Bureau of Plant Genetic Resources.
Q. 30. What are main functions of NBPGR?
Ans. Main functions of NBPGR are given below:
(i) To coordinate germplasm collection and conservation work.
(ii) It deals with export and import of germplasm of agricultural and horticultural crops.
(iii) To organize short term training course on various activities of germplasm.
(iv) To provide consultancy and guidance for creating cold storage facilities.
(v) To take decision for setting up gene sanctuaries of endangered species.
Q. 31. What is IBPGR?
Ans. IBPGR refers to International Board for Plant Genetic Resources, Rome, Italy. It was established in 1974 to coordinate global work of germplasm collection and conservation.
Q. 32. What is IPGRI?
Ans. IPGRI refers to International Plant Genetic Resources Institute, Rome Italy. IPGRI was established in October 1991. However, it started functioning in January 1994. In fact IBPGR, which was established in 1974 was renamed as IPGRI in January 1994. Now IPGRI coordinates the work of germplasm collection, conservation, exchange etc. at global level.
Q. 33. Who was N.I. Vavilov?
Ans. N.I. Vavilov was a famous Russian Plant Explorer.
Q. 34. Who was Har Bhajan Singh?
Ans. Dr. Har Bhajan Singh was a famous India Plant Explorer/germplasm curator.
Q. 35. What is Plant Quarantine?
Ans. Quarantine refers to the prophylactic measures which are used to prevent the entry of new diseases, insects and weeds from other countries.
Q. 36. What are quarantine organisations in India?
Ans. Quarantine inspection offices are located at all seaports and International Airports.
In India quarantine inspection is done by following organisations:
(i) NBPGR, It deals with quarantine Inspection of Agricultural and Horticultural crops.
(ii) Forest, Research Institute Dehradun. It deals with quarantine inspection of propagules of forest trees.
(iii) Botanical Survey of India, Kolkata. It deals with quarantine inspection of medicinal plants and other plant species.
(iv) Directorate of Plant Protection, Quarantine and Storage, Faridabad. It deals with quarantine inspection of food grains and other products imported for human consumption.
Q. 37. What is genetic diversity?
Ans. Genetic diversity refers to total amount of genetic variation present in a population or species. In other words, variety of genes and genotypes found in a particular crop species is known as genetic diversity.
Q. 38. What is genetic erosion?
Ans. Gradual reduction in genetic variability due to elimination of various genotypes from a population is called genetic erosion. It results due to replacement of land races with improved cultivars, modernization of agriculture and various developmental activities.
Q. 39. What is extinction?
Ans. Extinction refers to permanent loss of a crop species due to various reasons,
Q. 40. What is Biodiversity?
Ans. Biodiversity refers to total variability present within and among species of all living organisms and their habitats. In other words, biodiversity is sum of genes, species and ecosystem in a region.
Thus biodiversity is of following three types:
(i) Genetic diversity
(ii) Species diversity, and
(iii) Ecosystem diversity.
Q. 41. What is significance of species biodiversity?
Ans. Diversity of species offers opportunities for people to select species of their choices for food, cloth, shelter and medicinal uses. Diversity in the species has offered items of food, fuel, cloth, timber and medicines to human beings. Crop diversity provides an insurance against crop losses caused due to diseases and insects.
Q. 42. What is CBD?
Ans. CBD refers to convention on Biological Diversity.
The CBD was signed in 1992 and became operational in December 1993 with following objectives:
(i) Conservation of biodiversity
(ii) Sustainable use of biodiversity, and
(iii) Exchange of genetic resources for benefits of all countries.
Q. 43. What is centre of diversity?
Ans. A place, region or area where maximum variability of crop plants is observed is called centre of diversity, also called centres of origin. Centres of diversity are of three types, viz. primary centres, secondary centres and micro-centres.
Q. 44. What are primary centres of diversity?
Ans. Original homes of crop plants which are generally uncultivated areas such as mountains, hills, river valleys, forests etc. are called primary centres of diversity.
Main features of these centres are given below:
(i) They have wide genetic diversity
(ii) Have large number of dominant genes
(iii) Mostly have wild characters
(iv) Exhibit less crossing over
(v) Natural selection operates
Q. 45. What are secondary centres of diversity?
Ans. Cultivated areas with vast genetic diversity are called secondary centres of diversity.
Main features of these centres are given below:
(i) Have lesser genetic diversity than primary centres.
(ii) Have large number of recessive genes.
(iii) Mostly have desirable characters.
(iv) Exhibit more crossing over.
(v) Both natural and artificial selections operate.
Q. 46. What are micro-centres of genetic diversity?
Ans. Small areas within the centre of diversity that exhibit tremendous genetic diversity of crop plants are known as micro-centres.
Main features of micro-centres are given below:
(i) They represent, small areas within the centres of diversity,
(ii) Exhibit tremendous genetic diversity.
(iii) The rate of evolution in these centres in faster than larger areas.
(iv) They are important sites for study of crop evolution.
Q. 47. Who coined the term micro-centre?
Ans. The term micro-centre was first used by Harland in 1948.
Q. 48. What are differences between centres of origin and centres of diversity?
Ans. Main differences between centres of origin and centres of diversity are given below:
(i) Centres of origin are geographical areas where crop plants have originated.
(ii) Centre of diversity refers to a location where vast genetic variability for a crop and its variability are found.
Thus, centre of origin and centre of diversity for a crop may be the same or different.
Q. 49. What is law of parallel variation?
Ans. This law states that a particular variation observed in a crop species is also expected to be available in another related species; also called law of homologous series of variation.
Q. 50. Who proposed law of parallel variation?
Ans. The concept of parallel variation was developed by N.I. Vavilov in 1951.
Q. 51. What are Vavilovian Centres of diversity?
Ans. Based on his studies of global exploration and collection, Vovilov proposed eight main centres and three subsidiary centres of diversity as follows:
(i) Main Centres – Include China, Hindustan, Central Asia, Persia, Mediterranean, Abyssinia, Mexico and South America.
(ii) Subsidiary Centres – Indo-Malaysia, Chile, Brazil and Paraguay.
Q. 52. What are gene sanctuaries?
Ans. Protected areas of great genetic diversity under natural conditions (i.e. in-situ conservation) are called gene sanctuaries. Gene sanctuary is also known as natural park or biosphere reserve. India has set up its first gene sanctuary in the Garo Hills of Assam for wild relatives of citrus. Efforts are also being made to set up gene sanctuaries for banana, sugarcane, rice and mango.
Q. 53. What are advantages of gene sanctuaries?
Ans. Main advantages of gene sanctuaries are given below:
(i) It protects the loss of genetic diversity caused by human intervention.
(ii) It allows natural selection and evolution to operate.
Q. 54. What are drawbacks of gene sanctuaries?
Ans. There are two main drawbacks of gene sanctuaries as given below:
(i) Entire variability of a crop species cannot be conserved.
(ii) Its maintenance and establishment is a difficult task.
Q. 55. What do you mean by gene banks?
Ans. A place or organisation where germplasm is conserved in living state is called gene bank; also known as germplasm bank. Gene banks are of two types, viz. seed gene banks and field gene banks.
Q. 56. What is seed gene bank?
Ans. A place where germplasm is conserved in the form of seeds is called seed gene bank.
Main advantages of seed gene banks are given below:
(i) Whole variability can be conserved in a small space.
(ii) Handling of germplasm is easy.
(iii) Germplasm is conserved under pathogen and insect free environment.
Q. 57. What are demerits of seed gene bank?
Ans. Main drawbacks of seed gene bank are given below:
(i) Seeds of recalcitrant species cannot be stored.
(ii) It requires constant power supply.
(iii) It requires periodical evaluation of viability and fresh seeds for storage.
Q. 58. What are field gene banks?
Ans. Those areas of land in which germplasm of recalcitrant crop species is maintained in the form of plants are called field gene banks; also called plant gene banks. Field gene banks are maintained for crops like coconut, Rubber, Mango, Cassava, Yam, Cocoa etc.
Q. 59. What are advantages of field gene banks?
Ans. Main advantages of field gene banks are given below:
(i) Field gene banks provide opportunities for continuous evaluation of germplasm for various economic characters.
(ii) Also provide opportunities for utilization of germplasm in breeding programmes.
Q. 60. What are drawbacks/limitations of field gene banks?
Ans. Main demerits of field gene banks are given below:
(i) The entire variability cannot be conserved.
(ii) The germplasm is exposed to pathogens and insects. Also exposed to, natural disasters such as bush fire, cyclones, floods etc.
(iii) Maintenance is a costly affair.
Q. 61. What is cryopreservation?
Ans. Long term conservation of plant tissues (meristems) at extremely low temperature i.e, -196°C in liquid nitrogen is called cryopreservation. This method is widely used for conservation of horticultural species.
Q. 62. What is characterization?
Ans. Recording of highly heritable phenotypic characters in germplasm collections is called characterization. Evaluation refers to recording of both oligogenic and polygenic characters.