Assessment of diversity in native orchids

Abstract

A study entitled ‘Assessment of diversity in native orchids’ was conducted in the Department of Floriculture and Landscaping, College of Agriculture, Vellanikkara, from July 2019 to June 2020. The objective of the study was to assess the diversity among the native orchid accessions by evaluating their morphological characters. The morphological characters of twenty three native orchid accessions conserved under the Department of Floriculture and Landscaping were studied. Based on the growth habit, five accessions were classified as monopodial orchids and 18 accessions were classified as sympodial orchids. The accessions viz; Acampe praemorsa, Aerides crispa, Rhynchostylis retusa, Vanda thwaitesii and Luisia sp. were grouped under monopodials, and the accessions belonging to genera viz; Dendrobium, Eria, Pholidota, Bulbophyllum, Flickingeria, Coelogyne, Cymbidium and Oberonia were grouped under sympodials. The quantitative vegetative characters varied significantly among the accessions. Among the monopodial accessions, Acampe praemorsa (VKA/NOR-3) recorded maximum plant height (43.36 cm), internodal length (2.40 cm), leaf length (23.94 cm), leaf width (2.76 cm) and leaf sheath length (3.60 cm). In sympodial orchid accessions, plant height recorded was highest for Dendrobium moschatum (VKA/NOR-37) (75.20 cm). The highest plant spread was observed in Luisia sp. (VKA/NOR-7) (1571.28 sq.cm) among monopodials, whereas Dendrobium crumenatum (VKA/NOR-34) (3979.22 sq.cm) was superior in terms of this parameter among the sympodials. These two species also recorded maximum number of leaves compared to other accessions (89.20 and 95.80). Among sympodials, Cymbidium accessions were observed to be superior in terms of the parameter leaf length, and maximum leaf length was recorded in Cymbidium ensifolium (VKA/NOR- 43) (43.50 cm). Variability was also noted among the accessions with regard to qualitative vegetative characters viz; leaf shape, leaf orientation, leaf arrangement and root colour. Nine native orchid accessions bloomed during the study period were evaluated for their floral characters. Among them Dendrobium crumenatum (VKA/NOR-34) exhibited three flowering seasons (April-May, October, Dec-Jan). The accessionPholidota imbricata (VKA/NOR-29) recorded highest spike length as well as rachis length (49.66 cm and 23.50 cm). The number of florets per spike recorded was maximum in Rhynchostylis retusa (VKA/NOR-4) (99.33). Largest showy flower among the accessions was observed in Dendrobium moschatum (VKA/NOR-37) with maximum flower size of 54.37 sq.cm, highest petal length (3.98 cm), petal width (2.94 cm), petal to petal distance (6.89 cm), length of dorsal sepal (3.49 cm), width of dorsal sepal (1.63 cm), and length of lateral sepal (3.01 cm). Lip (labellum) is the most attractive feature of an orchid flower and is found to have variations. The accession Dendrobium crumenatum (VKA/NOR-34) (2.75 cm) was found to have maximum lip (labellum) length and Dendrobium moschatum (VKA/NOR-37) (2.28 cm) was found to have maximum lip (labellum) width. The longevity of spike on plant recorded was maximum for Dendrobium ovatum (VKA/NOR-60) (12.00 days), and the longevity of florets on spike recorded was maximum in Acampe praemorsa (VKA/NOR-3) (19.00 days). The pollen viability (%) was found to be more than 90 percentage for all the accessions flowered and it was noted maximum for Rhynchostylis retusa (VKA/NOR- 4) (98.27 percentage). Cluster analysis at 75 percentage similarity among the accessions done based on their quantitative characters resulted in different clusters containing accessions with similar morphological traits. Among sympodials most of the accessions were grouped under Cluster A with common characters for plant spread as well as leaf width. With respect to quantitative floral characters most of the accessions were grouped under Cluster A and they showed similarity for characters such as number of spikes, flower size, petal length and width, petal to petal distance, dorsal sepal to lip distance, length and width of lateral sepal and dorsal sepal, and also length and width of lip and column. Wide variation was observed in spike orientation, petal shape, petal curvature and lip shape. The accessions were also noted for the presence of flower fragrance, and it was recorded in Dendrobium crumenatum (VKA/NOR-34), Dendrobium fimbriatum (VKA/NOR-27), Dendrobium moschatum (VKA/NOR-37), Acampe praemorsa (VKA/NOR-3), Rhynchostylis retusa (VKA/NOR-4) and Eria fragrans (VKA/NOR- 25). The floral parts of the accessions also exhibited different sepal, petal, lip and column colouration.Based on morphological evaluation, superior accessions were identified for commercial traits and accordingly they were grouped as pot plant types (VKA/NOR-4, VKA/NOR-39, VKA/NOR-29), fragrant flowered types (VKA/NOR-27, VKA/NOR- 34, VKA/NOR-37, VKA/NOR-4, VKA/NOR-3) accessions with long spike (VKA/NOR-4, VKA/NOR-29), greater number of florets (VKA/NOR-4, VKA/NOR- 29) and highest longevity (VKA/NOR-29, VKA/NOR-3). Diversity assessment using cluster analysis has revealed the variability as well as similarity existed among native orchid accessions on the basis of their morphological characters. The findings are highly useful for identification of superior accessions which can be utilized for crop improvement programmes and also for commercial floriculture.