Browsing by Author "Aswini, M S"

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    Morpho- molecular characterisation and hybridisation in Oncidium and equitant oncidium orchids
    (Department of Genetics and Plant Breeding, College of Agriculture, Vellayani, 2025-07-30) Aswini, M S; Beena Thomas
    The present research programme entitled “Morpho-molecular characterisation and hybridisation in Oncidium and equitant Oncidium orchids” was carried out in the Department of Genetics and Plant Breeding, College of Agriculture, Vellayani during 2022-24. This research programme aimed to develop novel hybrids in Oncidium orchids as it is a less focused commercially important orchid species for crop improvement programmes. A total of twenty parental genotypes were collected from different nurseries across South India viz., Oncidium Jairak Fragrance (P1), Oncidium Jairak Fragrance OngKnot (P2), Oncidium J.F. Ha-Nu-Man (P3), Oncidium J.F. Pra-Lak(P4), Oncidium J.F. Montho (P5), Oncidium Guan Shin Rouge Ruby (P6), Oncidium Spacerace coco (P7), Brassia arcuigera (P8), Oncidium Sharry Baby (P9), Oncidium Yuan Nan Gold (P10), Oncidium Winterwonder white fairy (P11), Oncidium Kampangsan White (P12), Oncidium Golden Shower (P13), Oncidium Hybrid Miltasssia Sheloib Tolkein (P14), Oncidium Narisara SS (P15), Miltasia Royal Robe (P16), Oncidium Gum Pagan (P17), Oncidium Wild Cat 'Golden Red Star', Tolumnia Jairak Firm Sweet Pink (P19) and Tolumnia William Thurston (P20) were chosen for the research. They were subjected to evaluation for various qualitative and quantitative traits. Evaluation of parents was done for twenty-four quantitative traits. In addition, sixteen quality traits were also estimated in all the parental genotypes. In this study, for most of the traits, genotypic variance was observed close to the phenotypic variance, indicating that genetic factors predominantly control the variation in these traits. The PCV and GCV values were high for petal width, indicating substantial variability. Heritability was high (>60%) for nearly all traits, such as plant height, number of flowers per inflorescence, flower length, flower width, petal length, petal width, lip length, lip width, vase life and longevity of flowers in the stalk. Meanwhile, all the floral traits had high genetic advance as a percentage of the mean, indicating significant potential for improvement through selection, making them prime candidates for targeted breeding efforts. Overall, this analysis highlighted the strong potential for genetic enhancement of these traits in future breeding programs. In the correlation analysis, longevity of flowers in stalk or inflorescence exhibited a strong significant and positive correlation with vase life and length of inflorescence both at genotypic and phenotypic level. In the path analysis study, petal length stood out with the highest positive direct effect, making it the primary trait associated with enhancing the longevity of flowers. In this research programme, twenty parents were subjected to the molecular polymorphism study with the aid of twenty-five different ISSR (Inter Simple Sequence Repeat) markers. The ratio of absorbance at 260 nm and 280 nm (A260/A280) of all twenty extracted DNA samples of parents ranged between 1.80 and 2.03, indicating nearly 100% purity for the samples. The concentration of samples ranged between 445 and 1553 µg/ml. In this polymorphism study, UBC 844, UBC 824, UBC 807, UBC 818 and UBC 810 have shown higher PIC value. The percentage of polymorphic loci was found more for the primers UBC 807, UBC 808 and UBC 899 followed by UBC 810 and UBC 824. Further, hybridisation was carried out with the best ten genotypes selected based on flower synchronisation, flowering nature and variability studies. A total of seventy- three cross combinations were attempted based on flower synchronisation and flowering nature. P3, P4, P5, P8, P9, P10, P12, P16, P18 and P19 were the parents involved in the hybridisation process. Incompatibility reactions were noticed at different stages ranging from flower abscission before the onset of any visible post-pollination change to instances during the development of the capsule (seed pod). All the five cross- combinations obtained (P3 x P9, P10 x P5, P12 x P19, P19 x P5 and P5 x P19) were germinated successfully, sub-cultured at respective periods and planted successfully after the evaluation of plantlets. Oncidium species exhibit both self-incompatibility and interspecific pollination barriers, critical for maintaining genetic diversity and hybrid vigour. Following successful pollination, the developing capsule underwent several changes before harvest. Initially, the ovary showed slight enlargement and turned green. The longest capsule was obtained for the cross P10 x P5 (O. Yuan Nan Gold x Oncidium Jairak Fragrance Montho) and the shortest capsule was obtained for the cross P19 x P5 (Tolumnia Jairak Firm Sweet Pink x Oncidium Jairak Fragrance Montho). The cross combination P10 x P5 (O. Yuan Nan Gold x O. Jairak Fragrance Montho) recorded the highest days in this process and the lowest by P19 x P5. The total days required for green capsule harvest in successful crosses was minimum in the cross-combination P19 x P5. Orchid seeds are difficult to germinate naturally since it is devoid of natural storage organs for food reserves and the embryo is naked. In vitro germination using media like MS supplemented with benzylaminopurine (BAP) and Indoleacetic acid (IAA) has shown promising results. Out of five cross combinations in different bottles, all the combinations exhibited greening thereby initiating protocorm formation. In vitro propagation study revealed that the shortest time for initial germination was observed in P19 x P5 (Tolumnia Jairak Firm Sweet Pink x O. Jairak Fragrance Montho) (less than 1 month), while the longest is in P12 x P19 (1 month and 3 weeks). The fastest time for deflasking is also seen in P19 x P5 (O. Kampangsan White x Tolumnia Jairak Firm Sweet Pink) (7 months and 1 week), whereas the longest is in P12 x P19 and P5 x P19 (8 months and 1 week). This variation highlighted the influence of genetic combinations on growth stages in Oncidium orchid cross-combinations. Wide variation in days for different stages was noticed among different cross-combinations. The total days for initial germination ranged from 4 weeks to 1 month and 3 weeks. Further, days to protocorm formation varied from 1 month 4 weeks to 3 months and 1 week. The first leaf initiation started in 3 months and 2 weeks and ended up to 3 months and 4 weeks. Shoot initiation occurred from 4 months, 2 weeks of culturing to 5 months and 3 weeks of culturing. The roots were finally produced in 6 months to 6 months and 3 weeks. The deflasking was done for each cross-combination from 7 months, 1 week to 8 months, 1 week. Deflasked plantlets were subjected to morphological evaluation. Among the five cross combinations, P5 x P19 (Oncidium Jairak Fragrance Montho x Tolumnia Jairak Firm Sweet Pink) was observed as the longest plantlet for leaf length, root length, a greater number of roots and a higher root diameter. This indicated robust growth in seedling height, potentially due to favourable genetic combinations. The longest leaf reflected that superior leaf development is beneficial for photosynthesis and vigour. The longest root aids for better root extension, nutrient and water uptake. In conclusion, this research on Oncidium and equitant Oncidium orchids successfully integrated morpho-molecular characterisation, hybridisation and in vitro propagation to develop novel hybrids with significant genetic potential. Molecular diversity analysis using ISSR markers facilitated parental variability analysis, while hybridisation efforts yielded five promising cross-combinations, with P5 x P19 (Oncidium Jairak Fragrance Montho x Tolumnia Jairak Firm Sweet Pink) emerging as the most robust in terms of seedling vigour, leaf and root development and overall growth performance making it a promising candidate for further development. The study also optimised in vitro propagation protocols, ensuring successful germination and plantlet establishment. These findings underscore the potential of Oncidium orchids for commercial breeding, paving the way for further genetic enhancement and large-scale propagation.