A STUDY ON CORRELATION AND ASSOCIATION OF CHARACTERS OF EXACUM TETRAGONUM ROXB. IN NORTH KERALA, INDIA

Western Ghats provide asylum to several endemic plants. Exacum tetragonum Roxb. is one of the important endemic herbs inhabiting the hilly tracts and midlands of Kerala, the state of India located towards the south-western side of the Western Ghats. The plant is used for treating fever, stomach disorders, gout, diabetics, and eye diseases. It is also found associated with antioxidant, anti-inflammatory, anti-helminthic and anti-hyperglycemic activities. Correlation and association of characters of this important medicinal plant was analyzed based on the observations on thirteen salient morphological characters recorded from twenty three populations of the species distributed across Malappuram, Thrissur, Kozhikode and Palakkad Districts of Kerala State of India. All the characters studied such as plant height, number of leaves, number of flowers, number of inflorescences, leaf length, leaf breadth, peduncle length, pedicel length, internodal length, leaf area, mean stem girth, number of branches and fresh weight of plants showed statistically significant variations between the populations. Number of flowers showed significant positive correlation with the maximum number of characters (ten characters) whereas number of leaves showed significant positive correlation with the minimum number of characters (two characters). By factor analysis, two factors could be extracted and fresh weight of plant was found to be the lead character. Significant variability with regard to morphological characters indicates the strong genetic base of the plant species in the field. However, drastic changes in its habitat for various reasons can certainly cause severe threats to its continued existence and hence appropriate actions to conserve the natural habitats of this species are vital.

Western Ghats provide asylum to several endemic plants. Exacum tetragonum Roxb. is one of the important endemic herbs inhabiting the hilly tracts and midlands of Kerala, the state of India located towards the south-western side of the Western Ghats. The plant is used for treating fever, stomach disorders, gout, diabetics, and eye diseases. It is also found associated with antioxidant, anti-inflammatory, antihelminthic and anti-hyperglycemic activities. Correlation and association of characters of this important medicinal plant was analyzed based on the observations on thirteen salient morphological characters recorded from twenty three populations of the species distributed across Malappuram, Thrissur, Kozhikode and Palakkad Districts of Kerala State of India. All the characters studied such as plant height, number of leaves, number of flowers, number of inflorescences, leaf length, leaf breadth, peduncle length, pedicel length, internodal length, leaf area, mean stem girth, number of branches and fresh weight of plants showed statistically significant variations between the populations. Number of flowers showed significant positive correlation with the maximum number of characters (ten characters) whereas number of leaves showed significant positive correlation with the minimum number of characters (two characters). By factor analysis, two factors could be extracted and fresh weight of plant was found to be the lead character. Significant variability with regard to morphological characters indicates the strong genetic base of the plant species in the field. However, drastic changes in its habitat for various reasons can certainly cause severe threats to its continued existence and hence appropriate actions to conserve the natural habitats of this species are vital. 711 anti-oxidant, thrombolytic and anti-inflammatory agent (Ashwini et al., 2015). It contains various phytochemicals such as phenols, saponins, flavonoids and alkaloids. Naga people have been using Exacum tetragonum against malaria fever since long (Rao, 1983). The plant is used as an antidiabetic herb in Kerala (Sreelatha et al., 2007). In Khao Kho District of Thailand the species is considered as a valuable medicinal herb (Chuakul, 2000). Roots of Exacum tetragonum contain a colouring matter and hence it is used in alcoholic drinks in Germany and Switzerland (Torfida, 1944). Whole plant is used as tonic and stomachic by Ambalabe rural community (Vinayaka et al., 2016). Decoction of leaves and bark of Exacum tetragonum is used by Angami Nagas for curing malarial fever (Rao, 1983). It is widely used for curing human ailments like diabetes, malaria, skin disorders, fungal diseases and inflammation (Marles and Farnsworth, 1995).
The species is seen limited to small pocket areas even in vast stretches of grassland. This unique feature accompanied by the drastic social changes has subjected the plant to the threat of extinction (Sreelatha et al., 2007). The forest ecosystems of Western Ghats are under severe threat due to a variety of reasons. Understanding the genetics and interrelationship of the quantitative characters of such plants is an important step towards developing strategies for conservation. Hence the present study has been carried out to analyze the correlation and association of characters of Exacum tetragonum based on thirteen morphological characters (Table 1).

Materials and Methods:-
Twenty three natural populations of the plant were located at different parts of Malappuram, Thrissur, Kozhikode and Palakkad Districts of Kerala State of India during August-November 2018. The populations were frequently visited to assess their growth and when the plants matured and flowered, twelve plants were collected at random from each population so as to represent intrapopulational variability appropriately. The collected plants were observed for thirteen quantitative morphological characters. Correlation of these characters was analyzed as suggested by Rangaswami (1995). Study of association of characters was carried out to group the characters based on their relationship and also to find out the lead characters in each group. Study of character association of Exacum tatragonum was carried out using principal component analysis with the help of the statistical software STATISTICA. Factor analysis of thirteen morphological characters of Exacum tetragonum has been studied based on UPGMA method using STATISTICA software. Two factors were extracted from the data based on the relative contribution of the variable towards the variability of the species. Based on factor loading, plant height, number of flowers, numbers of inflorescences, leaf length, peduncle length, pedicel length, internodal length, leaf area, mean stem girth and fresh weight were grouped under factor 1 and number of leaves, leaf breadth and number of branches under factor 2 (Tables 4, 5 and 6).

Results and Discussion:-
It can be assumed that there is a sharing of common alleles between plant height, number of flowers, numbers of inflorescences, leaf length, peduncle length, pedicel length, intermodal length, leaf area, mean stem girth and fresh weight come under factor 1 and there is a sharing of common alleles between number of leaves, leaf breadth and number of branches under factor 2. In factor 1, fresh weight can be considered the lead character since it shows the maximum factor loading.
Grouping of variables can be used as a tool in selection programmes in future when commercialization of medicinal plant production may necessitate development of improved strains. Factor analysis has been used to group variables in different plants like rubber (Abraham et al., 2002), cardamom (Radhakrishnan et al., 2004) and chillies (Hrideek et al., 2006). Though considerably high field level variability is present in the plant species under study, steps should be taken to conserve its natural habitats from anthropogenic destruction and to augment its genetic base.