PhD Thesis

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/48

Browse

Subject: search.filters.subject.Genetics

Search Results

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Genetic improvement in Dendrobium orchids through hybridization and molecular characterization
    (Department of Plant Breeding and Genetics, College of Agriculture,Vellayani, 2023) Amrutha Unni, M.; Beena Thomas
    The present study entitled “Genetic improvement in Dendrobium orchids through hybridization and molecular characterization’ was carried out at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, during 2018-2022, with an objective to assess the genetic variability in commercially important Dendrobium orchids to develop superior hybrids and confirming hybridity through molecular markers. Twenty Dendrobium orchid genotypes with desirable traits and widespread market acceptance were collected, planted in the greenhouse and assessed for variability, heritability, genetic advance and correlation. Analysis of variance showed significant differences among the genotypes for all the characters studied. For the majority of the analysed traits, the mean performance has a broad range of variation among the parents. D. Thong Dang Yellow showed higher mean performance for internode length and plant height. Of the 20 genotypes, 15 flowered, while five genotypes failed to flower due to environmental factors and less adaptations. So the floral characters of 15 genotypes were studied. D. White represented desirable mean values for inflorescence diameter and inflorescence number per plant, D. Rabit Gold showed higher mean performance for pollen fertility and days to first flower opening from inflorescence, D. Gift by God Candy showed higher mean value for flower width in front view and days to last flower opening from first flower and D. Burana Pearl x D. Burana White showed higher peduncle length and vase life. For the vegetative characters, the thickness of leaf exhibited the highest GCV (66.16%) and PCV (69.54 %). High heritability coupled with high genetic advance was recorded for plant height, number of leaves per shoot, number of aerial roots, length of aerial roots, thickness of the shoot, internodal length, length of the leaf and leaf area which indicated that these traits were controlled by additive gene action. For the floral characters the maximum PCV and GCV were found in flower width in front view. All the floral characters showed high heritability along with high genetic advance, demonstrating that these traits were controlled by additive gene action. Plant height showed the strongest positive correlation with the number of aerial roots among the vegetative characters. Significant highly positive correlation was found between the number of inflorescences per plant and the inflorescence axis diameter. Days to first flower opening from inflorescence emergence recorded significant positive correlation with inflorescence axis diameter. Out of the 15 genotypes studied, three genotypes exhibited seasonal flowering nature and all others were free flowering. Inflorescence axis was found to be pendulous in D. Yaya and the rest of the genotypes produced erect or arching type of inflorescence axis. Flower fragrance were present in D. Red Fairy, D. Thong Dang Yellow, D. Popeyes and D. Gift by God Candy. Shape of flower was found as full and round, flat and surfaced with broad sepals and petals. In the study, thirty ISSR primers were used to examine the genetic diversity of 20 orchid hybrid genotypes used in this study. A total of 102 bands were produced, out of which 57 bands found were polymorphic and 45 bands were monomorphic in nature. Polymorphic information content value of the primer ranged between 0- 0.49. Dendrogram was generated using NTSYS-pc 2.02e software and the twenty genotypes were grouped into five clusters. Divergent lines identified were D. Pink bfc, D. Pearl Red Lip and D. King Dragon. The best ten parental genotypes were crossed based on flower synchronization and availability of pollen. A total of 20 cross combinations were attempted. Incompatibility reactions were noticed at different stages ranging from flower abscission before the onset of any visible post pollination change to instances where seeds germinated but aborted in culture. Mature green capsules were harvested from 12 combinations at 70 to 90 per cent maturity. The 12 combinations were inoculated in vitro, but four of them did not produce any seeds in the capsule and one did not germinate. All seven in vitro cultured combinations were successfully germinated and were sub cultured three to four times. The basal media used for the in vitro propagation was half MS. The in vitro growth of the hybrid Dendrobium was improved by supplementing with BA (1 mg/l), IAA (0.1 mg/1) and charcoal (4g/l) was found to be effective. Deflasked seedlings with three or more leaves and three or more roots were then transferred in half MS media. There was significant variance among the number of days required for germination, protocorm development, emergence of first leaf, the first shoot, the first root primordia and deflasking. At deflasking, there were noticeable variations in seedling morphology among the seven hybrid combinations. The present research work identified 10 commercially popular hybrid genotypes that excelled in floral features and diversity attributes. The hybrid plantlets developed through hybridization are to be hardened and maintained in net house for evaluation of morphological and floral traits. These can be utilized in further crop improvement programmes in Dendrobium.
  • No Thumbnail Available
    Item
    Characterization and distant hybridization for biotic stress tolerance in bitter gourd (Momordica charantia L.)
    (Department of Plant Breeding and Genetics College of Horticulture, Vellanikkara, 2018) Asna, A C; Jiji Joseph
  • No Thumbnail Available
    Item
    Genotyping of Rf (restoring fertility) loci of rice varieties of Kerala using molecular markers
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2017) Rajib Das; Jayalekshmy, V G
  • No Thumbnail Available
    Item
    Inheritance of yield and resistance to shoot and fruit borer (Leucinodes orbonalis GUEN.) in brinjal (Solanum melongena L.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2017) Gangadhara, K; Mareen Abraham
  • No Thumbnail Available
    Item
    Characterisation and genetic improvement in rose (Rosa spp.) through mutagenesis
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2017) Brunda, S M; Lekha Rani, C
  • No Thumbnail Available
    Item
    Identification of molecular markers linked to iron toxicity tolerance through bulk segregant analysis (BSA) in rice (Oryza sativa L.)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2016) Amaranatha Reddy, M; Rose Mary Francies
    Globally rice is the most important food crop, serving as staple food for more than half of the world’s population. As in other parts of the country, rice is the major food crop grown in Kerala too. The total annual production of rice is however insufficient to meet the total demand in the state. Iron toxicity prevalent in the rice growing tracts of the state, further compounds the problem of low rice production. Although, several attempts to ameliorate the iron toxic soil conditions are being made, the best way to combat this stress and increase rice production in the affected soils is to develop varieties tolerant to iron toxicity. The present investigation on 'Identification of molecular markers linked to iron toxicity tolerance through bulk segregant analysis (BSA) in rice (Oryza sativa L.)’ was conducted at College of Horticulture, Kerala Agricultural University (KAU), Vellanikkara, Thrissur during 2013 to 2015 year. The study involved screening of thirty rice genotypes for response to iron at toxic levels, hybridization between the most tolerant and susceptible genotype, production of F2 generation of this cross, parental polymorphism study using molecular markers and Bulk Segregant Analysis (BSA). The thirty rice genotypes were selected on the basis of their response to iron stress under KSCSTE project: ‘Donor identification for tolerance to iron toxicity in rice (Oryza sativa L.)’. Further screening of the thirty genotypes (Confirmation test 1 and 2) as per the method advocated by Shimizu et al. (2005) to confirm their tolerance or susceptibility to iron toxicity revealed existence of high significant differences among the genotypes with respect to leaf bronzing and biomass produced under varying concentrations of iron (0 ppm, 600ppm and 800ppm of Fe). Considering that at higher concentrations of Fe, a lower leaf bronzing and reduction in biomass, is a valid criterion for identifying genotypes tolerant to Fe stress, twelve genotypes viz., Cul-8709, Cul-210-29, AM-10-7, Cul-90-03, PM-709, ASD-16, ASD-18, Abhaya, IR-1552, T(N)-1, IR-36 and Cul-3 213 were found to be highly susceptible to iron stress while genotypes Cul-8723, Tulasi, Cul-18716, Kargi and IVT-33 were identified as the most tolerant ones. Selfing of F1s obtained on hybridizing the genotype (Tulasi) and genotype (CUL-8709) which were found respectively to be most tolerant and most susceptible to iron stress was done, to produce F2 population for the conduct of bulk sergegant analysis (BSA). Phenotyping of F2 plants under iron at toxic levels indicated presence of wide variability for shoot length, root length, total number of roots, number of fresh roots, shoot weight, root weight and visual scoring for iron-toxicity symptoms. The measures of skewness and kurtosis for various traits revealed a large quantitative variability. All the above traits except iron content in root of F2 lines exhibited a positive platykurtic distribution pointing to presence of gene interaction in trait expression. Measures of skewness and kurtosis also indicated occurrence of transgressive segregation in the F2 population. Leaf bronzing the typical symptom of Fe toxicity, showed a strong negative correlation with shoot length, root length, total number of roots, number of fresh roots, shoot weight and root weight. The results indicated that leaf bronzing is associated with growth reduction due to Fe2+ toxicity in this F2 population. Parental polymorphism (Tulasi and CUL-8709) survey using 338 Rice Microsatellites (RM) markers revealed 37 RM markers polymorphic between the two. These 37 polymorphic rice microsatellites markers (SSR markers) were found to be distributed over all 12 linkage groups of rice varying between one in case on Chromosome 7 to five each on Chromosome 2, 9 and 10. Bulk segregant analysis indicated that out of the 37 microsatellite markers that were polymorphic between parents seven viz., RM 263, RM 107, RM 12292, RM 24616, RM 24664, RM 13619 showed clear co-segregation with the susceptible parent and susceptible bulk, and resistant parent and resistant bulk. Probability of all seven putative markers was highly significant (P < 0.001) indicating strong association of these markers to the genomic region governing Leaf Bronzing Index which is a valid indicator of tolerance to iron toxicity. Through single marker analysis, three probable quantitative trait loci (QTL’s) of Leaf Bronzing Index were identified, each on 214 chromosome 1, 2 and 9. The QTL on chromosome 1 was located between 42.8 Mb and 43.2 Mb and associated with markers RM 12255 and RM 12292. The QTL for LBI was found to be associated with RM 13619 and RM 263 markers and placed between 24.9 Mb and 25.9 Mb on chromosome 2 while on chromosome 9, it was a located between 19.3 Mb and 20.1 Mb and linked to marker RM 107, RM 24616 and RM 24664.
  • No Thumbnail Available
    Item
    Induction of genetic variability in kacholam(Kaempferia Galanga L.)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 1997) Kanakamany, M T; Namboodiri, K M N