Analysis of variability for qualitative and quantitative traits in Coleus forskohlii Briq. C. Kavitha, E. Vadivel1, K. Rajamani and C. Thangamani Horticultural College and Research Institute Tamil Nadu Agricultural University, Coimbatore-641 003, India E-mail: ckavi_2k@yahoo.com ABSTRACT Thirty seven Coleus forskohlii genotypes collected from different regions of Tamil Nadu and Karnataka were subjected to diversity analysis based on NBPGR descriptors. Eleven qualitative and fourteen quantitative traits of C. forskohlii were evaluated to assess the morphological variations available among the collected genotypes. For qualitative traits, a large number of genotypes out of 37 clustered together at 74 % similarity in four different groups. The dendrogram contract based on fourteen quantitative traits for the same set of genotypes did not reveal a clear pattern in grouping and the genotypes were grouped into ten different clusters. Cluster analysis of various sets of data revealed different groups of genotypes for each of the data set. A poor congruence observed among data sets of qualitative and quantitative traits in the comparison indicated that the morphological traits are not suitable for precise discrimination of closely related genotypes in C. forskohlii. Key words: Coleus forskohlii, morphological traits, cluster analysis 1 Directorate of Extension Education, TNAU, Coimbatore – 641 003 INTRODUCTION Coleus forskohlii Briq is a root medicinal crop recorded in ancient Ayurvedic Materia Medica under the Sanskrit name ‘Makandi’ and ‘Mayani” (Shah, 1996). It belongs to the mint family of plants, Lamiaceae. In Ayurveda, the tuberous roots of Coleus are used as drug for heart diseases, abdominal colic, respiratory disorder, insomnia and convulsions (Ammon and Muller, 1985). The roots of the plant are a natural source of forskolin, a labdane diterpenoid that increases cellular levels of cyclic Adenosine Mono-Phosphate (cAMP) thereby influencing several aspects of metabolism.The therapeutic properties of forskolin contributed to the emergence of C. forskohlii as a taxon of importance in modern medicine. The exclusive presence of forskolin and the current recognition of its status as a unique plant species with high medicinal importance internationally, render a high profile for this particular crop. In this indigenous medicinal plant, knowledge on genetic variability within species will greatly help in direct exploitation of variability as cultivars and indirectly as base materials for various breeding programmes. MATERIAL AND METHODS Thirty seven genotypes collected from different regions of Tamil Nadu (17 genotypes) and Karnataka (20 genotypes) were grown in the field in a randomized block design with two replications at the Botanical Garden, Tamil Nadu Agricultural University, Coimbatore. The diversity in terms of morphological variations among the collected genotypes was documented following Singh et al (2003). Observations were taken on five randomly selected plants from each genotype for qualitative and quantitative traits. Qualitative traits that depict an array of characters were converted into binary characters (Sneath and Sokal, 1973) based on the variations present in each trait. The presence or absence of phenotypes was given the score of 1 and 0, receptively. The quantitative data gathered on different traits were standardized to zero mean and a unit variance. Sequential Agglomerative Hierarchical Non- overlapping (SAHN) clustering was performed on squared Euclidean distance matrix and similarity matrix using dice coefficient for quantitative and binary data respectively utilizing the Unweighted Pair Group Method with Arithmetic Averages (UPGMA) method. Analysis of data was done using NTSYSpc version 2.02 (Rohlf, 1994). RESULTS AND DISCUSSION Observations for eleven qualitative traits from five randomly selected plants of 37 different C. forskohlii genotypes indicated that two traits viz., plant habit and lamina margin did not show any difference between genotypes. The distribution of 37 genotypes based on their phenotype variants for qualitative traits observed is furnished in Table 1. For qualitative traits, a large number of genotypes clustered together at 74% similarity in four different groups (Fig 1). The extent of genetic diversity assessed based on these eleven qualitative traits with the minimum set of NBPGR descriptors of C. forskohlii revealed no satisfactory measures of diversity. J. Hort. Sci. Vol. 2 (1): 44-46, 2007 Table 1. Number of phenotype variants observed for various qualitative traits across 37 Coleus forskohlii genotypes Character Score Phenotype No. of genotypes Plant habit 1 Annual stem 37 with perennial rootstock 2 Biennial - 3 Perennial - Mode of reproduction 1 Asexual 19 2 Sexual 18 Plant growth habit 1 Erect 16 2 Sub - erect 21 Root/tuber branching 1 Profuse 22 2 Sparse 15 Root/tuber shape 1 Straight 18 2 Fusiform 19 Stem pubescence 0 Glabrous 2 3 Sparse 16 5 Medium 7 Dense 19 Lamina margin 1 Crenate 37 Lamina pubescence 3 Sparse 2 5 Medium 34 7 Dense 1 Lamina colour 1 Pale green 2 2 Purple green - 3 Dark green 35 Flower colour* 1 Pink-purple - 2 Pale-purple 2 3 Lilac - 4 Violet 16 Susceptibility 1 Very low or 34 to biotic stress no visible sign of susceptibility 3 Low 4 5 Intermediate - 7 High 1 9 Very high - *Only flowering genotypes were scored An additional 14 phenotypic quantitative characters were evaluated to enable diversity comparisons. The percentage of variation for individual traits varied from 4.41 (number of roots/tubers per plant) to 10.37 (root/tuber diameter) (Table 2). In the fourteen traits observed, the root/ tuber diameter showed the highest variation ranging from 0.38 cm (CF 3) to 0.90 cm (CF 30). Leaf yield per plant, number of branches per plant and root/tuber length also showed considerable variation. A minimum of 130.41 g and a maximum of 291.20 g leaf yield per plant were observed in CF 8 and CF 14, respectively. The number of branches was maximum in CF 23 (14.97) and minimum in CF 16 (7.62). The root/tuber length was 5.08 cm and 38.27 cm in CF 15 and CF 13, respectively. The dendrogram construction based on fourteen quantitative traits for 37 C. Coefficient Fig 1. Dendrogram of Coleus forskohlii genotypes for qualitative traits using UPGMA based on Dice Coefficient Table 2. Mean, range, coefficient of variation and standard deviation for each of the 14 quantitative traits Trait Mean Range CV (%) SD Number of roots/tubers per plant 25.36 16.12 - 45.77 4.41 1.12 Root/tuber length (cm) 23.60 5.08 - 38.27 7.46 1.76 Root/tuber diameter (cm) 0.63 0.38 - 0.96 10.37 0.07 Number of branches per plant 9.55 7.62 - 14.97 8.57 0.82 Stem diameter 1.53 1.05 - 2.06 7.25 0.11 Number of leaves per plant 172.28 94.00 -368.68 6.26 10.79 Lamina length (cm) 6.06 4.61 - 7.62 7.10 0.43 Lamina width (cm) 3.76 2.43 - 5.12 7.18 0.27 Petiole length (cm) 1.20 0.86 - 1.61 4.17 0.05 Leaf yield per plant (g) 202.21 130.41 -291.20 8.63 17.45 *Days to 50% flowering 84.73 65.00 - 95.00 7.20 8.49 Plant height(cm) 31.07 24.12 - 49.26 5.86 1.82 *Days to fruit maturity 106.25 95 - 115 8.72 9.27 **Forskolin / Coleonol content in roots (%) 1.25 1.14 - 1.40 7.03 0.09 * Only flowering genotypes were scored ** Only non-flowering (tuberous) genotypes were scored J. Hort. Sci. Vol. 2 (1): 44-46, 2007 45 Exploitation of genetic variability in Coleus forskohlii forskohlii genotypes did not reveal a clear pattern in grouping and the genotypes were grouped into ten different clusters (Fig 2). Morphological description can provide unique identification of genotypes, and are being used as descriptors for initial screening (Troyer, 1986). However they are not reliable us they reflect not only the genetic constitution of the cultivar, but also the interaction of the genotypes with the environment (Patterson and Weatherup, 1984). In the present study, cluster analysis of various sets of data revealed dissimilarity in groups of genotypes for each of the data set. A poor congruence among data sets of qualitative and quantitative traits showed in that the morphological traits alone may not be appropriate to assess Fig 2. Dendrogram of Coleus forskohlii genotypes for quantitative traits using UPGMA based on Squared Euclidean Distance of standardised data Mean the genetic diversity in C. forskohli as it is known that multiple genotypes can give phenotypes of similar outward appearance (Ravi, 2000).. In the present study, surveys failed to confirm similar patterns of diversity among combinations of qualitative and quantitative traits. G x E interaction effects were found to cause aberrant means for morphological traits. Though morphological traits have been used in assessing the genetic diversity of a species, the accuracy of the assessment is questionable. The availability of a limited number of morphological traits, their poor or unknown genetic control, environmental influence on the phenotypic expression, and difficulties in stage-specific identification are major impediments in using these as genetic traits for genetic diversity analysis. Thus morphological traits are inexpensive useful indicators for a preliminary, varietal identification. They can be used as a fast and simple general tool for assessing genetic diversity among phenotypically distinguishable cultivars, although they are inefficient on account of the time and cost involved. REFERENCES Ammon, H. P. T. and Muller, A. B. 1985. Forskolin: from an ayurvedic remedy to a modern agent. Planta Medica, 46: 473-477. Patterson, H. D. and Weatherup, S. T. C. 1984. Statistical criteria for distinctness between varieties of herbage crops. J. Agril. Sci., 102: 57-68. Ravi, M. 2000. Molecular markers based varietal profiling and monitoring in rice (Oryza sativa L.). M.Sc. thesis, Tamil Nadu Agricultural University, Coimbatore. Rohlf, F. J. 1994. NTSYS-PC: Numerical taxonomy and multivariate analysis system version 2.2. State University of New York, Stonybrook, New York. Shah, V. 1996. Cultivation and utilization of medicinal plants (supplement), RRL, CSIR, Jammu Tawi, pp 385-411. Singh, B. M., Mahajan, R. K., Umesh Srivastava and Pareek, S. K. 2003. Minimal Descriptors of Agri- Horticultural Crops. Part IV: Medicinal and Aromatic Plants. National Bureau of Plant Genetic Resources, Pusa Campus, New Delhi, pp 59-64. Sneath, P. H. A. and Sokal, R. R. 1973. Numerical taxonomy. Freeman, San Francisco and London. Troyer, A. F. 1986. United States Patent: Inbred corn line. Patent No.45948110. U.S.Patent Office, Washington, DC. J. Hort. Sci. Vol. 2 (1): 44-46, 2007 46 Kavitha et al (MS Received 28 October 2006, Revised 14 May 2007)