Lec 1, Pratical, Hybridization Techniques.pptx

importance of hybridization in field crops

1. Exercise No. 1 Hybridization techniques and Precautions to be taken - Floral Morphology, Selfing , Emasculation and Crossing Techniques in field crops

2. HYBRIDIZATION Producing new crop varieties in which two or more plants of unlike genetic constitution are crossed together. STEPS IN HYBRIDIZATION 1. SELECTION OF PARENTS The selection of parents should be done with great care, taking into consideration the objectives. As far as possible the parental types [female parent] must be selected from the local types, because they are best adaptable.

3. 2. SELFING OF PARENTS This is the second step and is essential for elimination of undesirable characters and also for obtaining the homozygous individuals. Selfing need not to be done in self-pollinated crops while in cross pollinated crops it has to be performed artificially. 3. EMASCULATION: Emasculation is the removal of male organs in bisexual flower before the anthers ripe.

4. 4. BAGGING The selected male and female flowers have to be bagged separately to prevent the contamination in staminate flowers and cross pollination in pistillate flowers. 5. CROSSING The desired pollen/anthers have to be collected from the male parent either in petridishes or in paper bags. The collected pollen has to be brushed or dusted on the stigmatic surface of the emasculated flower (female parent).

5. 6. TAGGING AND LABELLING The crossed flowers have to be properly bagged and labeled with the following information. 7. HARVESTING: The crossed seeds [F l ] have to be harvested after maturity

6. SELFING Self-Pollinated Crops: Artificial selfing is not necessary as they are naturally self-fertilized. 2. Cross-Pollinated Crops: The inflorescence should be enclosed in bags before anthesis to avoid cross-pollination. In crops like castor the whole inflorescence is enclosed in a bag and In maize selfing is done by collecting the pollen from the tassel and dusting on the silks of the same plant.

7. EMASCULATION METHODS FORCED OPEN METHOD In this method the flowers are opened by force before it opens naturally and the anthers are removed with a forceps. This technique is useful in large size flowers like cotton. 2. CLIPPING METHOD This technique is usually used in cereals like rice and wheat. In this method the top 1/3 portion of the spikelet is cut with scissors and the anthers are removed with forceps.

8. 3. RING CUT METHOD A circular cut is made at the base of the corolla, 2 mm away from ovary. The corolla is removed and the anthers are picked out with the help of a forceps. This method is generally used in leguminous crops and in cotton.

9. 4. KEEL RUPTURING METHOD In papilionaceous flowers such as black gram, green gram, red gram the keel petal is ruptured and the stamens are removed with the help of forceps. 5. HOT WATER TREATMENT The removal of stamens with forceps is time taking and tedious in plants having small sized flowers such as rice, jowar , ragi etc.

10. In such cases dipping the panicles in hot water for a definite period of time at a desired temperature is effective. This makes the pollen grains inviable without affecting the stigma and ovary. The panicles can be dipped in a thermos flask containing hot water. The temperature of water and time of dipping differ from crop to crop and variety to variety. In rice 45-52 C for 2-10 minutes is found effective.

11. 6. COLD WATER TREATMENT Treating the panicles with cold water at a temperature of 4 to 6 C for a particular time makes the pollen inviable . 7. CHILLING METHOD Chilling of plants for a particular length of time to allow the temperature to make the pollen sterility. In wheat, chilling treatment for 13 to 14 hours at 27-30 F would make the pollen sterile. 8. RELATIVE HUMIDITY METHOD The ear heads are given a special treatment so that the relative humidity around the panicles is increased.

12. For this purpose, the inflorescence is covered with moist cloth bag. Due to this the relative humidity increases forcing the anthers to come out, without dehiscing. The stamens are then removed with a forceps. Eg : rice 9. HOT AIR METHOD: The panicles are enclosed in a brown paper bag one to two hours before anthesis . After half an hour the temperature within the bag raises forcing the anthers to emerge out. The anthers are then removed with the help of forceps.

13. 10. CHEMICAL METHOD By spraying some of the chemicals called " Gametocides " such as 2,4-D, Maleic hydrazide . N.A.A., TIBA, Etherel etc., male sterility can be induced. 11. ALCOHOL TREATMENT The flower buds are dipped in ethyl alcohol for 5 to 10 minutes for making the pollen sterile. NAA -Naphthalene Acetic Acid TIBA – Tri iodo benzoic Acid

14. 12. MALE STERILITY METHOD In crops like maize, bajra , jowar , rice and sunflower male sterility occurs due to cytoplasmic and genetic causes or both. 13. SELF-INCOMPATIBILITY In crops like tobacco, potato and sunflower pollination with the desired pollen is possible without doing emasculation due to the presence of self-incompatibility.

15. CROSSING TECHNIQUES The emasculated flowers can be pollinated in different ways: 1. When the flowers produce small quantities of pollen, it will be collected in sterile petri dishes and the same will be transferred with the help of camel hairbrush. Eg . Chillies, tomato 2. When the flowers produce large amount of pollen, it will be collected in butter paper bags and dusted on the emasculated flowers. Eg : Bajra , Jowar , Maize. 3. In case of clipping method of emasculation, individual mature anther may be collected and inserted into the emasculated spikelets / florets. Eg : Paddy, Wheat etc.

16. 4. When the flowers are possessing numerous anthers the individual flower is collected after the corolla and calyx are removed and will directly made in contact with the stigma of the emasculated flower. Eg : Cotton. 5. The inflorescence of male and female parents are enclosed in a single bag and allowed for pollination.

17. FLORAL MORPHOLOGY STRUCTURE AND TYPES OF FLOWER A flower is a modified condensed shoot specialized to carry out sexual reproduction in higher plants. Like a branch, it arises in the axil of a small leaf-like structure called bract.

18. POSITION OF FLOWER A flower is usually seen either at the axil of a leaf or its branches. Accordingly, the flower is described as axillary and terminal respectively. A flower with stalk is described as pedicellate and a flower without stalk is called sessile.

19. PARTS OF A FLOWER The typical flower consists of following parts: 1. Bracts and Bracteoles 2. Thalamus 3. Calyx 4. Corolla 5. Androecium (Pollen grains-Male gametes) 6. Gynoecium (Ovule - Female gametes)

20. 1. BRACTS AND BRACTEOLES a) Bract: Bracts are modified leaves which bear flowers in their axils. A flower may be: ( i ). Bracteate : Flowers having bracts. (ii). Ebracteate : Flowers without bracts. The bracteate flowers have the following types of bracts: Leafy bracts: Large leaf-like bracts. Eg : Cotton. ii. Spathe : Large, often brightly coloured and cover spadix inflorescence. Eg : Banana, Maize, etc.

21. iii. Involucre : A large number of bracts form compact one or more whorls around a flower or an inflorescence. Eg : Sunflower. iv. Petaloid bracts: Bracts are large and brightly coloured. Eg : Bougainvillea. V. Glumes: Dry and scaly bracts found in association with spikelet inflorescence. Eg : Grasses (wheat, barley, oats etc.).

22. b) Bracteole: A secondary bract at the base of an individual flower. i . Bracteolate: Flowers having bracteoles. ii. Ebracteolate : Flowers without bracteoles. 1.2 THALAMUS: The thalamus is the short floral axis, with compressed nodes and internodes on which various floral leaves are inserted.

23. Based on Position of floral parts on thalamus in respect to ovary flowers are classified into three types

24. 1.3 CALYX The calyx is the outermost whorl of a flower composed of sepals. The sepals are usually green in colour, but sometimes, become brightly coloured then, said to be petaloid . e) Aestivation: The mode of arrangement of either sepals or petals of a flower in bud condition is known as aestivation. Types

25. Valvate : When the margins of sepals or petals just touch one another or lie very close to one another without overlapping, it its known as valvate aestivation.

26. ii. Twisted or contorted: When the margins of sepals or petals are overlapping along one margin but overlapped along the other in regular succession, it is known as twisted or contorted aestivation. Eg : Cotton

27. iii. Imbricate: When the arrangement of sepals and petals is so that one of them is external (it's both the margins are overlapping) and one is internal (it's both margins are overlapped). The remaining ones are overlapping along one margin but overlapped along the other. The imbricate aestivation is of two types.

28. ( i ). Ascendingly Imbricate: In this type, both the margins of the posterior petal (or) sepal is overlapped by the two lateral ones. While the margins of the anterior petal (or sepal) are overlapping. The remaining three petals are overlapping in such a way that one of their margins is overlapping and the other is overlapped by the other. (ii). Descendingly Imbricate: In this case, the posterior petal lies completely outside and covers the two lateral petals, which in their turn overlap the two other lateral smaller petals.

29. (iv). Quincuncial : In this type, arrangement of five sepals or petals is so that two of them are external (i.e., both the margins are overlapping) and the two are internal and remaining one, overlapping along one margin but overlapped along the other.

30. 1.4. COROLLA:- Corolla is the second accessory floral whorl and lies above the calyx. It is composed of petals. The petals are usually brightly coloured. When the petals are coloured, they are called Petaloid . Sometimes the petals may be green and are known as sepaloid . The various forms of corolla are stated below: Polypetalous Corolla: The petals are free from one another.

31. i . Regular forms: Cruciform: When there are four petals , the petals are arranged in the form of a cross, as in the members of the family Cruciferae .

32. b. Caryophyllaceous: When the corolla consists of five free clawed petals, with the limbs this form of corolla is a characteristic feature of the family Caryophyllaceae .

33. C. Rosaceous: In this type, the corolla consists of five petals without claw and with the limbs spreading outward. It is a characteristic type of corolla found in the family Rosaceae .

34. ii. Irregular forms: (a). Papilionaceous : When there are five irregular and free petals which resemble a butterfly. The posterior petal is larger than the other and is the outermost. It is called the vexillum or standard . Two lateral petals known as alae or wings. These in their turn overlap two anterior petals which are united to form a boat shaped structure known as keel or carina.

35. This is a characteristic type of corolla found in the family Papilionaceae .

36. b) Gamopetalous Corolla: The petals are fused with one another. i . Regular forms: Tubular: When the corolla tube is more or less cylindrical throughout as in the disc florets of Sunflower.

37. b. Campanulate or bell shaped: When the corolla tube is inflated below and to form a bell-shaped structure, as in many cucurbits.

38. c. Rotate or Wheel shaped: In this form, the corolla tube is short with spreading limbs at right angles to it, as in brinjal . d. Urceolate or Urn shaped: When the corolla tube is swollen in the middle but narrow above and below.

39. ii. Irregular forms: Ligulate or strap shaped: When the petals are united to form a short tube at the base but flat above like a strap as in ray florets of Sunflower.   b. Personate or Masked: It is just like bilabiate form of corolla (blipped), but the mouth remains closed by a projection of the lower lip known as palate, as in Sesamum .

40. c. Bilabiate or two lipped: When the limb of the corolla is divided into two portions or lips, known as the upper and the lower lip with the mouth remaining wide open. This is characteristic of the family Labiatae .

41. 1.5 ANDROECIUM: The androecium is third inner and upper floral whorl and is composed of stamens and anther. a) Number of whorls of stamens: According to the number of whorls, flowers are of following types: Monostamenous :- Stamens arranged in a single whorl; it is divided into two types: a. Alternipetalous : Stamens alternative with the petals, have number of petals equal to the number of stamens. b. Antipetalous : Stamens opposite to the petals.

42. ii. Dipostamenous : There are two whorls of stamens. Members of outer whorl opposite to sepals and that of inner whorl, opposite to the petals. iii. Obdiplostamenous : Reverse of diplostamenous , i.e., stamens in two whorls, members of outer whorl opposite to petals and that of inner whorl opposite to sepals. iv. Polystamenous : In this case more than two whorl present

43. b) Attachment of the anther to the filament: i . Basifixed : When the filament is attached directly at the base of the anther. Eg : Mustard ii. Dorsifixed : When the filament is fixed to the backside of the anther. iii. Adnate : When the filament is attached on the whole length of anther from base to apex.

44. iv. Versatile: When the filament is attached merely at a point about the middle of the connective. Eg : most of the grasses.

45. ii. Union of stamens among themselves. It is of three types: Adelphous : Filaments of stamens united, anthers remain free. It is again of three types. Monadelphous : When the filaments of all the stamens are united to form a single tube-like structure and the anthers remain free Eg : Members of the family Malvacaea 2. Diadelphous : In this type the filaments of stamens are united to form two bundles Eg : Pea.

46. 3. Polyadelphous : When the filaments of stamens are united to form a number of bundles Eg : Citrus. b. Syngenesious : When the anthers of stamens are fused, filaments remaining free Eg : Sunflower. c. Synandrous : When the anthers are united through their whole length i.e., by both filaments and anthers. Eg : Cucurbits

47. d) Adhesion of Stamens: Where members of one floral whorl are united with members of the other floral whorl, it is known as adhesion. It is of three types. Epipetalous: When stamens adhere to the petals they are known as epipetalous. eg : Brinjal . ii. Epiphyllous: When the stamens adhere to the perianth leaves ( tepals ). iii. Gynandrous / Gynostegium : Stamens unite with gynoecium eg : Calotropis .

48. e) Relative length of stamens: Sometimes the stamens of an androecium may not be of the same length. a. Didynamous : When there are four stamens in a flower, of which two are long and two are short. b. Tetradynamous : When there are six stamens, four of which in the inner whorl are longer than the two in the outer whorl. Eg : Family cruciferae .

49. c. Heterodynamous : The stamens in the same whorl are of different length.

50. ii. When the relative length of stamens are considered with regard to the corolla, two conditions are found. a. Exserted : When the stamens are longer than the corolla and they protrude out of the flower. b. Inserted: When the stamens are shorter than the corolla and they remain within the flower.

51. f) Orientation of Face: i . Extrorse : When in the bud condition, the face of anther faces towards the corolla. ii. Introrse : When in the bud condition, the face of anther faces towards the gynoecium . INTRORSE EXTRORSE

52. g). Anthers: (T.S = Transverse Section) Dithecous : In T.S. of anther four loculi present Monothecous : In T.S. of anther only two loculi present h). Dehiscene : ( i ). Porous: When pollen grains liberate through pores Eg : Solanum spp.

53. (ii). Valvular : Pollens are discharged through a trap-door-like valve formed on the anther wall. (iii). Longitudinal: The anther lobes burst lengthwise along the line of suture from base to apex. (iv). Transverse: The anther splits up transversely (as the suture is present crosswise) E.g., Malvaceae .

54. Various types of dehiscence of anthers i ) Longitudinal ii) Transverse iii) Porous iv) Valvular

55. 1.6 GYNOECIUM It is the central or the topmost floral whorl of the flower usually terminating the thalamus. It is made up of one or more carpels . a) Kinds of Pistil: i . Monocarpellary: When the gynoecium is made-up of a single carpel, it is known a monocarpellary gynoecium . Eg : Leguminosae & Gramineae members. Similarly, when, there are two or three carpels , the gynoecium is known as bicarpellary and tricarpellary respectively.

56. ii. Polycarpellary: When there are more than one carpel in a gynoecium it is known as compound or polycarpellary gynoecium . When the gynoecium is polycarpellary, two conditions are met within (a). Apocarpous : When all the carpels remain completely free from one another. eg : Rose. (b). Syncarpous : When the carpels are wholly or partially united with each other, it is known as syncarpous gynoecium . eg : Lady's finger.

57. b) Placentation :- The mode of origin and distribution of placenta in the ovary is called placentation . Various types of placentations are as follows:

58. i . Axile Placentation :- In this case the placentae arise on the cenral axis formed by the ingrowths of the united margins of two or more carpels at the centre. The ovary is divided into as many chambers as there are carpels . Ex. Solanaceae , Malvaceae , Liliaceae etc.

59. ii. Marginal Placentation : In this type of placentation , the placenta arises along the ventral suture of a monocarpellary gynoecium (as in pea family). The ovary is unilocular and the placenta is attached to its margin.

60. iii. Parietal Placentation : When the placentae arise from the united margins of two or more carpels , as for example in mustard etc.

61. iv. Basal Placentation : When the placenta arises at the base of the unilocular simple ovary, the inner wall of the ovary remains smooth in this case. Eg : Compositae .

62. V. Free — Central Placentation : In this type the ovules are found to be attached on an axial placenta which is not connected with the ovary wall.

63. Vi. Superficial Placentation : The ovary is multilocular as in axile placentation but the placentae develop from the inner surface of the partition walls, as in the case of poppy.

64. Marginal Axile Parietal Basal Free central Superficial PLACENTATION