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Title of Thesis

Institute/University/Department Details
Institute of Pure and Applied Biology/ Bahauddin Zakaria University Multan
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
malformation, mango inflorescence, biotic diseases, sindhri, anwar rataul, dusehri, malda, fajri, s.s.-i, chaunsa, seedling mango, langra, f. mangiferae

Global mango production is seriously hampered by several biotic diseases. Malformation is the major threat to mango crop in Pakistan. No orchard is found free from the attack of the disease. Controversy on the cause of the disease, serious economic consequences and lack of multidimensional studies emphasized to devise a comprehensive study to combat this malady.

On commencement of the project, latest report on current disease development based on extensive survey of a variety of cultivars covering a larger area of the Punjab was not available. So disease assessment studies were conducted with the objective to record the disease position, update the existing statistics and explore the scientific estimation of the disease. Assessment was done in 40 orchards of eight districts of the Punjab province. Malformation showed 100% prevalence in the surveyed orchards. Mean of two years data revealed that Jhang was the most affected district with 63.18% severity while Khanewal was least affected with 12.98% severity.

Although variation in severity in districts and even trees of the same cultivars were observed, but in fully malformed trees, typical malformation symptoms like hypertrophy, thickening of rachis and bunching of floral parts were observed. All the traditional mango cultivars were more or less disposed to the disease. Seedling mango proved to be the highly susceptible showing 40.12% severity during two assessment years. Eight cultivars viz. Seedling mango, Sindhri, Anwar rataul, Dusehri, Malda, Fajri, S.S.-I and Chaunsa with nine disease rating were graded susceptible. Only one cultivar Langra appeared to be moderately susceptible with 7 disease rating.

The interactions of districts, cultivars and fungus were studied by assay of 1500 malformed tissues obtained from five local cultivars of 10 districts. Data revealed the association of five fungi. F. mangiferae was the dominant fungus causing 65.0 and 93.33% tissue and sample's infection respectively. F. pallidoroseum, Alternaria alternata, F. oxsporum and F. equiseti showed 1.59, 1.53, 0.46, 0.26 and 11.99, 9.99, 2.00, 1.33% tissue and sample's infection respectively. Comparative distribution of F. mangiferae in three cultivars of ten districts exhibited cumulative infection of 85.72% (1543 of 1800 tissues) as compared to non malformed ones which showed only 20.44% infection (368 of 1800 tissues).

Twenty representative isolates of fungus F. mangiferae were identified from 10 local and 2 exotic cultivars growing at 14 locations of Pakistan. All the malformation isolates conformed to the attributes of the species. The colonies were mostly tinged with purple color on reverse of petridishes. Macroconidia were three septate, slightly sickle shaped to straight with dorsal and ventral surfaces almost parallel. Microcoidia were fusiform, obovoid and oval to elliptical. The size of macroconidia fell in the reported range of 3.5-5 x 45-60 µm.

The attempt to manifest disease by artificial inoculations proved successful. Four, 6 months old mango seedlings out of six and one 2 years old plant of Chaunsa cultivar produced malformation to the extent of 66.66 and 33.33% respectively. Symptoms were produced by wound inoculation (flap cut method) only as compared to spore spray, carborundum abrasion and control. The studies provided the evidence that the fungus F. mangiferae is the cause of the disease. Out of two isolates tested, FM -16 proved to be pathogenic. Reisolation from the inoculated parts confirmed the identity of FM-16. Isolate FM-6 was unable to display symptoms.

Random amplified polymorphic DNA (RAPD) analysis was employed for genomic DNA of twenty isolates using 50 random primers. A total of 393 amplification products were produced with an average of 7.86 bands per primer. The size of the amplified products was in the range of 250 bp to 3 kbp. Contrary to morphological and cultural similarities, variation in banding pattern of isolates was reflected. The isolates were discriminated into two clusters with 13 and 7 isolates in A and B cluster respectively. The most closely related isolates were FM-4 and FM-6 with 92.5% genetic similarity.

The ultrastructural studies confirmed the inter and intracellular presence of the fungus F. mangiferae in malformed mango buds and its role in disease causation. No fungus was detected in healthy tissues, cells or intercellular spaces. Cell orientation in healthy cells was well organized and clear. No such distinction could be made in cells of malformed buds.

The immunogold labeling provided the potential for precise localization of fungal sections. Polyclonal antisera raised were found specific towards the isolates of F. mangiferae. The ultrathin sections trimmed from buds infected with isolate FM-2 and FM-17 showed labeling specificity when sections coated with respective immuno globulin G (IgG) were examined under Transmission Electron Microscope (TEM). Tiny gold granules (15 ‹m) were seen dusted with peculiarity over the surface of osmicated cross sections lying within tissue of malformed bud only. The fungal ingress in intercellular space was clearly evident at higher magnification. The results indicated the precision of labeling reactions.

Eight fungicides were screened for their in vitro effect after three time periods on mycelial growth of F. mangiferae. Benlate 50 WP and Carbendazim proved to be the best fungicides giving 100% suppression of the colony growth. Generally a decrease in colony growth was observed with increasing concentrations of the fungicides. The fungicides were classified into three types i.e. I, II and III, in reference to the sensitivity of F. mangiferae. Fugus proved highly sensitive (S) to Benlate 50 WP, Carbendazim, Topsin-M 70 WP and Copper oxychloride 50 WP which were assigned type I with 100% suppression at minimum inhibitory concentrations (MICs).

In field trial, effect of clipping of malformed branches at ½ , l' and 1½€™ distance behind the panicles combined with Benlate 50 WP spray (@ 1.5 gm 1-1 water) in the respective treatments was evaluated. Pruning 1 ½ and ½ ' descended with 69.38, 48.77 and 38.59% decrease over previous years count (control). The treatment where clipping was done at 1 ½ ' distance followed by spray of Benlate proved to be the best giving 72.04% decrease over previous years count.

Download Full Thesis
3356.47 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
178.08 KB
2 1 General Introduction 1
216.8 KB
  1.1 The Genus Mangifera 1
  1.2 Botanic Characters 1
  1.3 Origin 5
  1.4 Distribution And Spread 5
  1.5 Local Cultivation 7
  1.6 Economic Importance 7
  1.7 Nutritive Value 7
  1.8 Diseases And Disorders 8
  1.9 Malformation 8
  1.10 Need For The Project 11
  1.11 Objectives 11
3 2 Disease Assessment Studies 12
303.87 KB
  2.1 Introduction 12
  2.2 Materials And Methods 15
  2.3 Results 18
  2.4 Discussion 27
4 3 Distribution Of Fungi: Determination Of Fungi Associated With Symptomatic And Non Symptomatic Tissues Of Mango 32
557.55 KB
  3.1 Introduction 32
  3.2 Materials And Methods 37
  3.3 Results 39
  3.4 Discussion 62
5 4 Pathogenicity Studies By Artificial Inoculations 68
243.97 KB
  4.1 Introduction 68
  4.2 Materials And Methods 70
  4.3 Results 72
  4.4 Discussion 78
6 5 Characterization Of Isolates Of F . Mangiferae Through RAPD 80
385.28 KB
  5.1 Introduction 80
  5.2 Materials And Methods 83
  5.3 Results 87
  5.4 Discussion 94
7 6 Detection 100
871.68 KB
  6.1 Introduction 100
  6.2 Materials And Methods 105
  6.3 Results 110
  6.4 Discussion 124
8 7 Control Strategies 132
852.86 KB
  7.1 Introduction
  7.2 Material And Methods 136
  7.3 Results 139
  7.4 Discussion 151
  7.4 Conclusive Discussion 156
  7.5 References 158
  7.6 Appendices 183