Morphological characters of kepel (Stelechocarpus burahol) from Kulon Progo, Yogyakarta, Indonesia

Kepel is a rare plant that becomes the identity plant of Special Region of Yogyakarta and often used as natural perfume and bio-pharmaceutical. This research was conducted to identify the vegetative characterization of kepel and to determine the variety of kepel in Kulon Progo Regency, Special Region of Yogyakarta, Indonesia. The study was conducted from December 2018 to March 2019. The research method used was survey method with sampling purpose in 12 sub-districts in Kulon Progo. Kepel plant that have produced fruits, healthy, and normal growth were used as samples. Each plant was observed and the vegetative parameters were measured including the trunk, the leaf, and the canopy. The observation variables according to the description for Annonaceae. The data were analyzed using cluster analysis. Morphological characters from 36 samples in Kulon Progo had a high diversity based on similarity analysis in 14 variables with coefficient of similarity 35-92%. There are four clusters with a similarity level of 49,5%. Cluster 1 has 10 samples (27.78%), Cluster 2 has 22 samples (61.11%), Cluster 3 has 2 samples (5.56%), and Cluster 4 has 2 samples (5.56%). Kepel Wates5 is expected to be a high-yielding variety based on the number of tubercles and tree age.

Kepel is a unique plant that the canopy has shape resembling a triangle, the color of young leaves are pink, the flowers are unisexual monoecious flower (male flowers are in tree branches, while female flowers are in main stem), and the fruits located on the stem. Kepel is currently listed in the "List of Rare Plants" The scarcity of Kepel has entered the category of Conversation Dependent (CD) which means that the existence of Kepel has been difficult to find because it has been scarce and if conservation is not done immediately, the status of Kepel can increase to be vulnerable. The first step that can be done for the conservation of Kepel plants is the identification and characterization of Kepel  The study was conducted using a survey method with purposive sampling. Plants used as samples with the criteria of fruitful, healthy, and normal growth. Based on the initial survey throughout Kulon Progo, there were 35 trees that fulfilled the requirements as sample plants for observing the morphological characters of the Kepel. Data retrieval is done by collecting data directly through observing the vegetative characters of Kepel plants including canopy, stem, and leaves. Observation variables are based on descriptions for Annonaceae (Annona cherimolla) plants from International Biodiversity, International Plant Genetic Resources Institute (IPGRI) [6].

Data Analysis
Data from observations of plant morphology are presented in the form of scoring, then analyzed to assess the similarity matrix using the SIMQUAL (Similarity for Qualitative Data) procedure. Grouping of matrix data (cluster analysis) and making dendograms is done by the Unweigthed Pair-Group Method Arithmetic Average (UPGMA) method using numerical taxonomic and multivariate system (NTSYS) version 2.02i [7].

Morphological Characters of Kepel in Kulon Progo Regency
Based on survey in Kulon Progo Regency, 36 samples of kepel were obtained in all of sub-districts. The sample were characterized by 16 variables of vegetative characters, including canopy, stem, and leaf characters. The data in Table 1 and Table 2 revealed the similarity of characters in leaf margin, while there were variations in canopy shape, crown diameter, stem circumference, trunk ramification, trunk colour, number of tubercles, shape of leaf blade, shape of leaf base, shape of leaf apex, leaf color, leaf length , leaf width, and stem length. Kepel plants in the Kulon Progo are almost entirely plants that grow in the yard of a home or office, and garden. Plants height were varying between 7.1 -18 meters, and based on interviews with owners or managers, kepel age about 18-100 years. Table 1 indicated that all plants in Kulon Progo Regency have pyramidal canopy forms with 3 different shapes, and have 1-3 trunk ramification. The canopy diameters were from 3.75 to 8.2 meters. The trunk up to 1,36 m in stem circumference with the color of trunk light brown, geige, gray to brown, and the bark covered with numerous tubercles. The number of tubercles in one meter trunk length ranges from 1 to 19 tubercles. The amount of tubercle in kepel tree can predict the amount of fruit produced. Sunarto [8] and Lim [9] mentioned that kepel tree is an erect and evergreen tree which can reach up to 25 m tall. Its trunk is up to 40 cm in diameter. It is dark gray-brown to black and characteristically covered with numerous thick tubercles.
Leaf blade of Kepel from 36 plants in Kulon Progo are dominated by elliptic and lanset forms ( Table 2.). Leaf margins from all entire accessions do not undulate. The shape of leaf base obtuse and acute, there is no rounded and cordate form and the leaf apex acute and acuminate, none is rounded. The color of mature leaves is light green to dark green. Leaf lengths 14.5-23.6 cm, leaf width 4.6-9.7 cm, and petiole length 0.4-1.5 cm. Van Heusden [10] and Hatmi and Widyayanti [11] stated that leaves of burahol are corious to subcoriaceous, occasionally membranous, more or less shiny above, less shiny beneath, (dark) brown to dry, glabrous on both sides or sometimes sparsely pubescent beneath, usually with numerous brown to red beneath, lamina (narrowly) elliptic to elliptic-oblong, sometimes too narrowly obovate, obovate-oblong. Leaves are 8-31 cm long, 2.5-9.5 cm wide, base acute, sometimes to rounded, tapering to acute, caudate, or acuminate.
Based on International Biodiversity [6], descriptor for Annonaceace plants is only represented by Annona cherimolla (Cherimoya). The descriptor is explained vegetative character of Annonaceae plant, especially in Cherimoya including tree age, height, trunk, and leaves, but there is no specific character for Stelechocarpus burahol. Canopy shape of St. burahol was like a cone or pyramid [12][13], but there were no further explanation. In this research we found that Stetechocarpus burahol in Kulon Progo have four different forms of canop especially the top of canopy, they are: Pyramidal 1 (acute), Pyramidal 2 Acuminate, Pyramidal 3 (obtuse), and Pyramidal 4 (random). There are three forms of suckering in the descriptor for Annona cherimolla (absent, <5 suckers, and >5 suckers). In this research we found that all Kepel plants there no have suckers, all plants are erect evergreen tree, and the bark characteristically covered with numerous thick tubercles.

Cluster Analysis
Based on similarity analysis from 12 differences observation variables, it was known that 36 kepel accessions in Kulon Progo district have a high level of variation in the vegetative character with coefficient of similarity between 36-92% or have a diversity level of 8-64%. Kepel plants until now can only be propagated using seeds and very difficult to propagated using vegetative propagation [8, [14][15] so that genetic diversity in kepel is quite high. The results of cluster analysis indicated that with a similarity level of 36% there were two big clusters ( Figure 2). Cluster A has 34 samples (94.44%) and cluster B has 2 samples (5.56%). The differences between clusters I and II are mainly in shape of leaves, shape of leaf base and leaf apex.  11%), cluster 3 has 2 samples (5.56%), and cluster 4 has 2 samples (5.56%). The formation of clusters indicated that the accession that form in the same cluster have close relationships because they have many similarities in their morphological characteristics. whereas the separation in clusters indicated a long relationship because they have many differences in their morphological characteristics [16][17]. In addition, the dendrogram based on vegetative characters of 36 samples of kepel plant also shows there are 2 pairs of plants that are really closely related with the similarity coefficient 92% or with a level of diversity of 8%. These samples were D5 and G1 (Kalibawang 5 and Panjatan 1); and also C1 and E1 (Sentolo1 and Samigaluh1). Distribution of kepel plant in Kulon Progo and distribution of kepel plants that have a high degree of similarity are shown in Figures 3.   Distribution of kepel trees in Kulon Progo district spread in 12 sub-districts: Temon, Kokap, Sentolo, Kalibawang, Samigaluh, Girimulyo, Panjatan, Wates, Pengasih, Nanggulan, Galur, and Lendah (Fig. 3). Based on the cluster distribution (shown in the same color), it can be seen that the distribution of kepel trees on the same cluster spread from north to south. Kepel trees that have a 92% coefficient of similarity indicate that they have very close relatives. Two pairs that have close relatives are in a long distance, otherwise, the kepel plants in the short distances have high diversity. It was indicated that kepel plants in Kulon Progo have a very high diversity and it was not influenced by the proximity of the place of growth. This is possible because until now, plant propagation of kepel plants only be done generatively and it cannot be propagated by vegetative methods, so that it has a fairly high diversity.
Based on observational data of vegetative characters. it cannot be ascertained which that kepel accession has superior characteristics because the superior characteristics of kepel are determined not only by vegetative character, but also by generative characters, especially kepel fruit. However, from the data of observation and calculation of the number of tubercles in the trunk, it indicated that the number of tubercles in plant sample C4, E1, E2, H2, and I1 has the highest number of tubercles per meter trunk compared to other plants. Tubercle is small bump like round warts on the trunk of the tree and where flowers and fruit appear. Therefore. the more tubercles in the stem. it is strongly suspected that the tree is more productive in producing flowers and fruit. Further research is needed to identify not only the generative character of the kepel but also molecular character of kepel trees to get more complete information as a data base for kepel germplasm for conservation and breeding.   The vegetative characters of 5 selected accession of Kepel tree with 14 variables indicates a difference. Accession H2 located in Wates sub-district is estimated to have the potential as a plant with superior character. This is shown in the Comparison of vegetative characters from 5 samples selected (Table 3). The H2 (Wates 2), which is in the tree age 15 years with 10.2 tree height, crown diameter 7.9 m, and 3 trunks ramification, it has 17 tubercles in 1 m trunk length. Wates 5 really has the potential to have the highest productivity, however, it need further research in generative character, especially, fruit performances

Conclusion
Vegetative character from 36 samples of Kepel plants in Kulon Progo, Yogyakarta city has a high diversity based on similarity analysis in 14 variables with coefficient of similarity 35-92%. The results of cluster analysis indicated that there are four clusters with a similarity level of 49,5%. Cluster 1 has 10 samples (27.78%), cluster 2 has 22 samples (61.11%), cluster 3 has 2 samples (5.56%), and cluster 4 has 2 samples (5.56%). Kepel sample E5 located in Wates sub-district (Wates5) is expected to be a high-yielding variety based on the number of tubercles and tree age.