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Title of Thesis

Muhammad Jafar Jaskani
Institute/University/Department Details
Department of Horticulture/ University of Agriculture Faisalabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
interploid hybridization, kinnow mandarin , ploidy manipulations, tetraploid, murashige, skoog, sexual hybrids, endosperm culture, interploid crossing, seedless kinnow, kinnow

Kinnow mandarin is the major citrus cultivar of Pakistan. It is highly adapted to our soil and climatic conditions. A major drawback in Kinnow is its high number of seeds. Breeding for seedlessness of Kinnow has been the primary objective of these investigations.

Natural and conscious ploidy manipulations have played a significant role in the domestication and improvement of crops. Production of seedless triploid citrus fruits could lead to the improvement of internal quality of fresh fruits. Many triploid citrus varieties have been developed and released by breeders elsewhere. Kinnow being the major cultivar in Pakistan, has been focused in this study. Methods for production of triploids were investigated. Diploid Kinnow mandarin, Succari sweet orange and Sweet lime were crossed reciprocally with tetraploid Kinnow. Low fruit set, fruit drop and underdeveloped seeds hampered the breeding program. Immature and mature embryo culture methods were employed to achieve maximum recovery of hybrids. Embryos were excised from seeds at 3 and 7 months after pollination and cultured in vitro. Different media formulations based on Murashige and Skoog (MS), and Murashige and Tucker (MT) salts were used. MS supplemented with adenine sulphate (20 mg/l) and malt extract (500 mg/l) proved successful for embryo germination. Embryo proliferation was observed from 2.25% of all cultured embryos excised 3 month postpollination, only in case of 2x X 4x Kinnow crosses.

Description of recovered plants was made by morphological and cytological studies. Morphological observations showed no marked differences except significant differences in leaf size. Cytological examinations showed that stomatal density and size alongwith number of chloroplasts in guard cells of stomata could be a useful appliance to characterize polyploids. Most of the plants were triploid but tetraploid and diploid were also identified at varying frequencies. The greatest frequency of triploid plant recovery resulted when embryos were cultured in vitro after 3 month of pollination. Triploid plants identified on the basis of stomatal density, size and number of chloroplasts were confirmed by chromosome counts using light microscopy. Isozyme analysis was tried to distinguish plants of varied ploidy levels. Similar banding pattern in diploid and tetraploid Kinnow and their progenies were observed for glutamate oxaloacetate transaminase and maleic dehydrogenase isozyme system.

Endosperm of diploid Kinnow and Succari cultivars was also cultured in vitro for direct regeneration of triploids. Among the two media, only MS supplemented with Kinetin (0.5 mg/l), 2,4-0 (2 mg/l), myoinositol (100 mg/l) and thiamine HCI (5 mg/l) induced callus. Callus growth was comparatively better in Succari than Kinnow. A series of media in solid and liquid forms were also tested for both cultivars. On solid media, growth of callus derived from Succari was better. MS supplemented with SA (10 mg/l), NAA (0.1 mg/l) and malt extract (500 mg/l) yielded good callus of green colour. In liquid media, Kinnow produced maximum callus growth on 2MT added with casein hydrolysate (500 mg/l), GA3 (2 mg/l), SA (0.25 mg/l) and adenine (2 mg/l). No success in regeneration from callus was achieved on several recipes under trial.

As a result of this series of investigations, a number of triploids have been selected and propagated. The future trials and investigations of selected triploids are likely to deliver seedless Kinnow-type citrus varieties.

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
402.97 KB
2 1 Introduction 1
130.17 KB
3 2 Review Of Literature 8
534.01 KB
  2.1 Spontaneous Triploids 9
  2.2 Small Seeds 11
  2.3 Crossing Tetraploid Seeds With Diploids 12
  2.4 Crossing Diploid Seeds Parent With Tetraploids 13
  2.5 Embryo Rescue In Sexual Hybrids 15
  2.6 Somatic Hybridization 20
  2.7 Seedlessness Through Irradiation 21
  2.8 Mutagens 23
  2.9 Apomixis 24
  2.10 Identification And Characterization Of Triploids 26
  2.11 Endosperm Culture 33
4 3 Materials And Methods 37
212.65 KB
  3.1 Interploid Crossing 37
  3.2 Isolation And Culture Of Endosperm 44
5 4 Results And Discussion 47
3781.84 KB
  4.1 Interploid Hybridization 47
  4.2 Isolation And Culture Of Endosperm 136
6 5 Summary 147
149.25 KB
7 6 Conclusion 153
56.46 KB
8 7 Literature Cited 155
496.73 KB