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Genetic Variability Studies in Oncidium Orchids
Abstract
An investigation was carried out with eighteen Oncidium orchid genotypes for the assessment of genetic variability and heritability in 2023. In this investigation, variation due to genotypes for all the traits under study was found significant indicating high amount of variability among different genotypes for different traits providing ample scope for selection and further evaluation as well as improvement in the shelf life and other traits. Number of base leaves per plant, length of inflorescence(cm), petal length (cm), petal width (cm), and lip length (cm) had high heritability estimates along with high genetic advance expressed as per cent of mean which implied that these traits are controlled by genes which are additive in nature. Simple selection for such characters would be rewarding. In addition, vase life of flowers (days) had moderate heritability estimates along with moderate genetic advance expressed as per cent of mean, it may require a sustained effort and might be enhanced by complementary strategies such as environmental management and advanced breeding techniques. GCV (%) was found high in petal width which is close to PCV (%) indicating that variability of the trait is largely due to genetic factors with minimal environmental influence. High heritability (>60%) combined with high genetic advance (>20%) was exhibited by majority of the characters under study indicating additive gene action for these characters and it provides a scope for further improvement of these traits in advance generations.
... Variability can manifest phenotypically through differences in floral morphology, leaf structure, or growth habit, as well as genotypically, which may enhance adaptability to various environmental stresses (Aswini et al, 2024). Biometric tools such as genotypic coefficient of variation (GCV) and phenotypic coefficient of variation(PCV), heritability and genetic advance are essential for measuring genetic divergence among genotypes and can be used to improve the various genera of monopodials for utilizing their potential for intra and intergeneric hybridization. ...
Monopodial orchids are highly valued for their ornamental appeal, longevity, and adaptability. This study aimed to evaluate the genetic variability among selected monopodial orchid genotypes to support breeding programs for development of hybrid varieties. Twelve monopodial orchid varieties, including monogeneric and bigeneric hybrids were evaluated using a Completely Randomized Design (CRD) with twelve treatments and six replications. The selected materials were evaluated by recording observations on their vegetative and floral characters. Various parameters of variability, heritability and expected genetic advance were calculated. The mean and standard errors were worked out as per standard methods and then coefficients of variation were computed. Significant variations were observed among the genotypes, particularly in inflorescence length, flower count, and vase life, with high heritability and genetic advance estimates. These findings highlight the genetic potential of monopodial orchids for hybridization, emphasizing the importance of selecting genetically diverse parents to enhance flower quality, productivity, and stress resistance. This study contributes to the development of novel monopodial orchid hybrids with superior commercial traits for both domestic and international markets.
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Oncidiumconsists of 750 species of sympodial epiphytic orchids from America, Mexico and Argentina. Hybridization of Oncidiumorchids with Brassia orchids, Miltonia orchids and Odontoglossum orchids resulting in an Oncidium orchid that has some warmth toleranceand beautiful flowers. Hybrids and some commercial species are used for cut flowers, hanging baskets and potted plants. The present investigation was carried out with 8 hybrids of Oncidium orchids which were grown with recommended package of practices under greenhouse condition. Observations were taken on 60 morphological characteristics which could be used in future for crop improvement programme for developing new Oncidium hybrids.
Oncidium 'Gower Ramsey' (Onc. GR) is a popular cut flower, but its color is limited to bright yellow. The β-ring carotene hydroxylase (BCH2) gene is involved in carotenoid biogenesis for pigment formation. However, the role of BCH2 in Onc. GR is poorly understood. Here, we investigated the functions of three BCH2 genes, BCH-A2, BCH-B2, and BCH-C2, isolated from Onc. GR to analyze their roles in flower color. RT-PCR expression profiling suggested that BCH2 genes were mainly expressed in flowers. The expression of BCH-B2 remained constant while that of BCH-A2 gradually decreased during flower development. Using Agrobacterium tumefaciens to introduce BCH2 RNA interference (RNAi), we created transgenic Oncidium plants with downregulated BCH expression. In the transgenic plants, flower color changed from the bright yellow of the wild type to light- and white-yellow. BCH-A2 and BCH-B2 expression levels were significantly reduced in the transgenic flower lips, which make up the major portion of Oncidium flower. Sectional magnification of the flower lip showed that the amount of pigmentation in the papillate cells of the adaxial epidermis was proportional to the intensity of yellow coloration. HPLC analyses of the carotenoid composition of the transgenic flowers suggested the major reductions in neoxanthin and violaxanthin pigments. Conclusively, BCH2 expression regulated the accumulation of yellow pigments in Oncidium flower, and the down regulation of BCH-A2 and BCH-B2 changed the flower color from bright yellow to light- and white-yellow. This article is protected by copyright. All rights reserved.
An experiment was carried out using 20 native Dendrobium orchids in Completely Randomized Design (CRD) with three replications at the Orchidarium of Landscape, Ornamental and Floriculture Division, HRC, BARI, Gazipur during the period to estimate genetic variability, genetic parameters and correlation coefficient among different flower components. Highly significant variations were observed among the genotypes for all the characters. High broad sense heritability with high genetic advance was observed in spike length (94.00% and 98.29), rachis length (95.34% and 93.85), flower durability (94.00% and 89.00) and floret number (70.50% and 65.47) indicating additive gene action, suggesting the possibility of improvement of these traits through selection. Other characters exhibited moderate broad sense heritability with low genetic advance. The number of florets per spike recorded a highly significant association with flower durability, rachis length and spike length. Durability of flower had significant positive correlation with rachis length, flower size and spike length at both genotypic and phenotypic level. Highly significant positive correlation was also found between rachis length and spike length. However, the correlation study revealed that selection of parents should be done based on characters such as floret number, rachis length and flower durability which would be useful in a breeding program. The path analysis revealed that rachis length, durability of flower and number of flowers per spike had contributed maximum direct effects on flower yield, indicating the importance of these three characters as selection criteria for native Dendrobium orchid.
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