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Everything you need to need about breeding for disease and insect resistance !
Q. 1. What is disease?
Ans. In crop plants, various disorders caused by pathogens are called disease.
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Q. 2. What is pathogen?
Ans. Various disease causing organisms such as fungi, bacteria, viruses and mycoplasma refer to pathogen.
Q. 3. What is pathogenicity?
Ans. Ability of a pathogen to attack a host is called pathogenicity.
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Q. 4. What is host?
Ans. The plant which is attacked by a disease, insect or parasitic weed is called host.
Q. 5. What is parasite?
Ans. An organism or virus which lives upon or within another living organism is called parasite.
Q. 6. What is pest?
Ans. Any animal or higher plant which parasitizes crop plants i.e. insects, nematodes, birds and parasitic needs refer to pest.
Q. 7. What do you mean by immune?
Ans. Completely or fully resistant plants are known as immune.
Q. 8. What is virulent?
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Ans. A race of a pathogen which is capable of attacking a host with specific resistance is called virulent race.
Q. 9. What is avirulent?
Ans. A race of a pathogen which is unable to attack a host having specific resistance is known as avirulent race.
Q. 10. What is physiological race?
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Ans. Strain of a pathogen differing in pathogenicity is known as physiological race; also called pathotype. Races of a pathogen are of two types, viz. virulent and avirulent.
Q. 11. What is biotype?
Ans. Variant or new strain of an insect is called biotype.
Q. 12. What is epidemic?
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Ans. Wide spread uncontrolled incidence of a disease is known as epidemic.
Q. 13. What is genetic resistance?
Ans. Ability of some genotypes to give higher yield of good quality rather than other varieties/genotypes at the same initial level of disease or insect infestation under similar environmental conditions.
Genetic resistance is of two types, viz.:
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i. Vertical and
ii. Horizontal.
Q. 14. What is vertical resistance?
Ans. Resistance of a host to the particular (specific) race of a pathogen is called vertical resistance. It is also known as major gene resistance, oligogenic resistance, race specific resistance and qualitative resistance.
Q. 15. What is horizontal resistance?
Ans. Resistance of a host to all the prevalent races of a pathogen is called horizontal resistance. It is also known as minor gene resistance, polygenic resistance, nonspecific resistance, general resistance and quantitative resistance.
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Q. 16. Who coined terms vertical and horizontal resistance?
Ans. Terms vertical resistance and horizontal resistance were first used by Van der Plank in 1963.
Q. 17. What is durable resistance?
Ans. The long lasting resistance is known as durable resistance. It may be vertical or horizontal.
Q. 18. What is seedling resistance?
Ans. The resistance which is exhibited by young seedlings is known as seedling resistance.
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Q. 19. What is adult resistance?
Ans. The resistance which is exhibited by adult plants is termed as adult resistance.
Q. 20. What is field resistance?
Ans. The resistance which gives an effective control of a parasite under field conditions is known as field resistance.
Q. 21. What do you mean by major genes?
Ans. Genes with distinct individual effect which can be easily identified are known as major genes.
Q. 22. What are minor genes?
Ans. Genes with small effect on a character which cannot be easily identified are called minor genes.
Q. 23. What is hypersensitivity?
Ans. A host pathogen interaction which leads to death of infested tissues is called hypersensitivity. It is an important mechanism of disease resistance.
Q. 24. What is difference between yield breeding and biotic resistance breeding?
Ans. In productivity breeding, there is interaction between genotype and environment. In resistance breeding for biotic factors, there is triangular interaction of host-pest environment.
Q. 25. What are advantages of genetic resistance?
Ans. Main advantages of genetic resistance are given below:
(i) It reduces environmental pollution and health hazards caused by pesticides.
(ii) It permits multiplication of natural enemies of insect pests.
(iii) It also reduces cost of crop production.
Q. 26. What is gene for gene hypothesis?
Ans. This hypothesis states that for each gene controlling resistance in the host, there is a corresponding gene controlling pathogenicity in the pathogen. It is also known as Flor hypothesis.
Q. 27. Who developed the concept of gene for gene hypothesis?
Ans. The concept of gene for gene hypothesis was developed by Flor in 1956 working with linseed crop.
Q. 28. What are mechanisms of disease resistance?
Ans. There are three mechanisms of disease resistance as given below:
(i) Resistance to establishment of the pathogen in the host tissue.
(ii) Resistance to growth and development of pathogen already established in the host tissue,
(iii) Ability of a host to perform well despite the establishment of the pathogen in the host tissues.
Q. 29. What are mechanisms of insect resistance?
Ans. There are four mechanisms of insect resistance as follows:
(i) Non-preference or non-acceptance.
(ii) Antibiosis
(iii) Tolerance and
(iv) Escape or avoidance.
Q. 30. What do you mean by non-preference?
Ans. Non-preference refers to various features of host plant which make the host undesirable or unattractive to insects for food, shelter or reproduction. It is also known as non-acceptance or antixenosis.
Q. 31. Which plant characters are associated with non-preference?
Ans. Following plant characters are associated with non- preference:
(i) Colour of leaves
(ii) Light penetration
(iii) Hairiness of stem & leaf
(iv) Leaf angle
(v) Odour
(vi) Taste.
Q. 32. What are the characters associated with non-preference to bollworm in cotton?
Ans. In cotton, following characters are non-preference to boll worms:
(i) Red plant body
(ii) Smooth leaves
(iii) Okra leaf
(iv) Open canopy
(v) Nectarilessness
(vi) Fregobract.
(vii) Thick and hard boll rind
(viii) Long pedicel.
Q. 33. What is non-preference to stem sawfly in wheat?
Ans. In wheat, solid stem is non-preference for stem sawfly.
Q. 34. Which traits are non-preference to brown plant hopper in rice?
Ans. In rice, low asparagine, red pericarp and purple stigma are non- preference to brown plant hopper.
Q. 35. What is non-preference for jassids in cotton?
Ans. In cotton, hairiness of leaves is non-preference to jassids.
Q. 36. What is non-preference for pea aphid in pea?
Ans. In pea, yellow green leaves are non-preference to pea aphid.
Q. 37. What is antibiosis?
Ans. Antibiosis refers to adverse effects of the host on feeding, development and reproduction of insect pests. Resistant plants retard the growth and rate of reproduction of insect pests. In some cases, antibiosis even leads to death of an insect. Antibiosis may involve morphological, physiological and biochemical features of the host plant.
Q. 38. What are the characters associated with antibiosis to bollworm in cotton?
Ans. In cotton, high levels of gossypol, tannins, heliocides and silica contents are associated with antibiosis to bollworm.
Q. 39. What is associated with antibiosis to green bugs in wheat?
Ans. In wheat, high benzyl alcohol is associated with antibiosis to green bugs.
Q. 40. What acts as antibiosis to cereal leaf beetle in barley?
Ans. In barley, waxiness of leaves acts as antibiosis to cereal leaf beetle.
Q. 41. What acts as antibiosis to stem borer in rice?
Ans. In rice, high silica content acts as antibiosis to rice stem borer.
Q. 42. What acts as antibiosis to stem borer in maize?
Ans. In maize, high aspartic acid acts as antibiosis to maize stem borer.
Q. 43. What acts as antibiosis to European corn borer in maize?
Ans. In maize, high DIMBOA in leaves acts as antibiosis to European corn borer.
Q. 44. What acts as antibiosis to spotted aphid and pea aphid in alfalfa?
Ans. In alfalfa, high saponin content acts as antibiosis to spotted aphid and pea aphid.
Q. 45. What acts as antibiosis to cabbage aphid in Brassica?
Ans. In Brassica, low sinigrin content acts as antibiosis to cabbage aphid.
Q. 46. What is tolerance to insects?
Ans. Tolerance refers to the ability of a variety to produce greater yield than susceptible variety at the same level of insect attack. Tolerant cultivars have greater recovery of damaged parts than susceptible ones.
Q. 47. What is plant features associated with insect tolerance?
Ans. The following plant characters are associated with insect tolerance:
(i) Speedy recovery of damaged parts.
(ii) Healthy leaf growth,
(iii) Superior plant vigour,
(iv) Potential for flower compensation.
Q. 48. What is insect avoidance or escape?
Ans. Avoidance refers to escape of a variety from insect attack either due to earliness or its cultivation in the season where insect population is very low. For example, early maturing cotton varieties escape pink boll worm infestation which occurs late in the season.
Q. 49. Who first gave mechanisms of insect resistance?
Ans. Mechanisms of insect resistance were first proposed by Painter in 1951. He gave three mechanisms of insect resistance in crop plants, viz. non- preference, antibiosis and tolerance.
Q. 50. What are basis of insect resistance?
Ans. There are following three important bases of insect resistance:
(i) Morphological Factors:
It includes various morphological traits such as hairiness, colour, thickness and toughness of tissues.
(ii) Physiological Factors:
It includes osmatic concentration of cell sap and leaf exudates.
(iii) Biochemical Factors:
It includes various types of chemical compounds such as high gossypol, tannins, heliocides and silica contents for bollworms in cotton.
Q. 51. What are sources of insect resistance in crop plants?
Ans. In crop plants, there are five important sources of insect resistances as follows:
(i) Cultivated varieties,
(ii) Germplasm collections,
(iii) Wild species and wild relatives,
(iv) Induced mutations, and
(v) Micro-organisms such as Bt.
Q. 52. What are factors affecting durability of insect resistance?
Ans. The durability of insect resistance depends on the following factors:
(i) Formation of new biotypes of an insect.
(ii) The mode of inheritance of insect resistance.
(iii) Morphological and biochemical characters associated with insect resistance.
Q. 53. What breeding methods are used for developing insect resistant cultivars?
Ans. The following breeding methods are used for developing insect resistant cultivars:
(i) Plant introduction.
(ii) Pure line selection and mass selection.
(iii) Backcross, bulk and Pedigree breeding methods.
(iv) Mutation breeding, and
(v) Transgenic breeding.
Q. 54. How much yield losses are caused by insect in crop plants?
Ans. In crop plants, about 14% yield losses are caused annually by insect pests.
Q. 55. How much annual yield losses are caused by diseases in crop plants?
Ans. In crop plants, about 20-30% annual yield losses are caused by various diseases.
Q. 56. What is gene pyramiding?
Ans. Incorporation of two or more major genes in a variety for specific resistance to a disease is called gene pyramiding.
Q. 57. What is difference between gene pyramiding and multi-lines?
Ans. In multiline approach, each major gene is incorporated into separate genotype and then resistant genotypes are mixed together. In gene pyramiding approach, all major genes are incorporated in a single cultivar.
Q. 58. What are advantages of gene pyramiding?
Ans. Varieties which are developed by gene pyramiding approach have durable resistance. New cultivars are developed with a combination of 2, 3 or more major genes.
Q. 59. In which crop gene pyramiding approach has been used?
Ans. Gene pyramiding approach has been used in oats against crown rust in Canada.
Q. 60. What is gene deployment?
Ans. Planned use of major genes in development of disease resistant cultivars for various geographical areas is called gene deployment. This approach helps in preventing diseases and maintaining the diversity for major genes in different geographical regions.
Q. 61. How vertical resistance can be exploited in plant breeding?
Ans. In plant breeding, vertical resistance can be exploited in following ways:
(i) By developing multi-lines.
(ii) By developing cultivars with individual major gene.
(iii) By gene pyramiding and
(iv) By gene deployment.
Q. 62. What is Verticellium tolerant variety of upland cotton?
Ans. In upland cotton, variety MCU 5 is tolerant to Verticillium wilt.
Q. 63. What is yellow mosaic resistant variety of okra?
Ans. In okra, variety Parbhani Kranti is resistant to yellow mosaic virus.
Q. 64. What is stem sawfly resistant variety of wheat?
Ans. In wheat, variety ‘Rescue’ with solid stem is resistant to stem sawfly. It was released in Canada in 1946.
Q. 65. What is green bug resistant variety of barley?
Ans. In barley, variety “Will” is resistant to green bugs. It was released in USA.
Q. 66. What are resistant varieties of alfalfa to spotted alfalfa aphid?
Ans. In alfalfa, varieties Cody, Moapa and Zia are resistant to alfalfa spotted aphid. These varieties were released in USA.
Q. 67. What is stem eelworm resistant variety of oat?
Ans. In oat, variety Greta is resistant to stem eelworm. It was developed in Belgium.
Q. 68. What are jassids resistant varieties of cotton?
Ans. In upland cotton, varieties B 1007, Khandwa 2, SRT 1, DHY 286 and PKV 081 are resistant to jassids.
Q. 69. What are whitefly resistant/tolerant varieties of cotton?
Ans. In upland cotton, varieties Kanchana, Supriya and LK 861 are resistant to whitefly.
Q. 70. Give name of leaf curl resistant hybrid of cotton.
Ans. Intra-lursutum cotton hybrid LHH 144 is resistant to leaf curl virus. It was developed from Punjab Agricultural University, Ludhiana.
Q. 71. Who first proposed use of multi-lines for control of diseases?
Ans. The use of multi-lines for controlling diseases in crop plants was first proposed or suggested by Jensen in 1952.
Q. 72. What is parasitic weed of sorghum in India?
Ans. In India, Striga is the parasitic weed of sorghum. Striga is found in Maharashtra state.
Q. 73. What is the Striga resistant variety of Sorghum?
Ans. The variety SAR 1 of Sorghum is resistant to Striga. It was released from ICRISAT for cultivation in those areas of Maharashtra where Striga is a problem.
Q. 74. What is serious parasitic weed of sugar-beet in Turkey?
Ans. In Turkey, Cuscuta is a serious parasitic weed of sugar beet.
Q. 75. What is serious parasitic weed of Sorghum in Africa?
Ans. In Africa, Orobanche is the serious parasitic weed of Sorghum.
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Q. 76. Where have been developed Orobanche resistant varieties of chickpea?
Ans. Orobanche resistant varieties of chickpea have been developed at ICARDA in Syria.
Q. 77. Where have been developed Orobanche resistant varieties of sunflower?
Ans. Orobanche resistant varieties of sunflower have been developed in Russia.
Q. 78. What are damages caused by Insects?
Ans. Insect attack leads to following damages:
(i) Stunting-reduction in plant growth.
(ii) Damage of vegetative and reproductive parts.
(iii) Premature defoliation.
(iv) Wilting of plants.
Q. 79. What are biological methods of insect control?
Ans. Biological methods of insect control are given below:
(i) Use of resistant varieties.
(ii) Use of botanical pesticides such as Neem, Ipomoea, Datura etc.
(iii) Use of predators and parasites.
