Karyotype Report
Karyomorphological analysis of Pterocarpus santalinus (Fabaceae): An endemic tree species from Eastern Ghats of India
2024 年 89 巻 1 号 p. 61-64
詳細
2024 年 89 巻 1 号 p. 61-64
Pterocarpus santalinus (Fabaceae) is one of the endemic and rare species of Eastern Ghats. The present study reveals the karyomorphology of P. santalinus along with somatic chromosome number 2n=20 exhibiting the karyotype formula i.e., 20 m. The karyotype belongs to 1A of Stebbins category.
The genus Pterocarpus Jacq. belongs to the family Fabaceae and is represented by ca. 37 species in the world of which four species occur in India (Pullaiah et al. 2019). These are P. dalbergioides, P. indicus, P. marsupium, and P. santalinus. Among these P. santalinus is one of the most valued species found in South India. This species occurs as an endemic in the hills of Kadapa, Kurnool, Chittoor, Nellore, and Prakasam districts of Andhra Pradesh and occasionally occurring in some pockets of adjoining states of Karnataka and Tamil Nadu at an altitude range of 200–900 m (Pullaiah and Chennaiah 1997).
Pterocarpus is derived from the Greek words pteron (wing) and karpos (fruit), referring to the winged pod, while santalinus originates from the Latin sandal and inus (meaning similar to), i.e., a plant with characteristics similar to Indian sandalwood, Santalum album L. (Botanical Survey of India 2012). P. santalinus is also prized for its hard, dark purple, bitter heartwood (Navada and Vittal 2014). In India, the natural range of P. santalinus used to be a very restricted area of 15,540 km2 in the southeast (Sarma 1993). Currently, P. santalinus is found exclusively in a well-defined forest tract of Andhra Pradesh in Southern India. The color and fragrance of P. santalinus heartwood are derived from santalins while the pleasant aroma is caused by the presence of terpenoids. A dye prepared from the heartwood of P. santalinus is used as a stain in light microscopy, as a coloring agent in pharmaceutical preparations, in food, leather and textile industries, and as a textile dye (Teixeira da Silva et al. 2019). Cytogenetical data on endemic species are important from the perspective of understanding their biology. Cytological information such as chromosome number and the karyotype symmetry of chromosomes is valuable in presuming evolution and interrelationships inside the group. Chromosome data is a further parameter that can improve the existing classification. The report presents chromosome number and karyotype in P. santalinus. providing basic cytogenetic information.
Seeds of P. santalinus, were collected from trees (Fig. 1A–C) at Palakonda hills (N14°07′44.40″E07859′22.46″) 392 m and Guvvalachervu RF (KDP), Kadapa district, Andhra Pradesh, India. The voucher specimen is deposited in the Herbarium, Department of Botany, Yogi Vemana University-CN & AMR 5108 (YVUH). For mitotic chromosome studies the root tips were collected from germinated seeds. Root tips were pre-treated with a saturated aqueous solution of paradichlorobenzene at 8–10°C for 4–5 h. Washed root tips with water were hydrolyzed in 1 M HCl and squashed after staining in 2% propionic orcein. Ten well-spread somatic chromosome plates were used for karyotype analysis. The well-spread chromosome plates were photographed with a Carl Zeiss Axio Imager A2 attached with a camera. The chromosome number study followed Mane et al. (2020) and Pawar et al. (2021). Types of chromosomes were evaluated by using centromeric index (i) (Levan et al. 1964), Karyotype morphometric characters were evaluated by calculating haploid complement length together with intrachromosomal asymmetry index (A1) and inter chromosomal asymmetry index (A2) as given by Zarco (1986).
(A) habit, (B) flowers, (C) fruits, (D) somatic chromosome plate, (E) Karyotype. Scale bars=5 µm.
Somatic chromosome number 2n=20 was observed in P. santalinus (Fig. 1D). Chromosomes ranged from 1.19±0.26 µm to 2.84±0.36 µm in length and all of them were observed to be metacentric (Table 1). The total chromosome length of the haploid complement was 20.17±0.50 µm. The total form percentage was 42.34. The symmetric index was 73.44 and the gradient index was 41.91. The coefficient of variation of chromosome lengths and the coefficient of variation of the centromeric index were 24.71 and 6.77, respectively. A1 and A2 were 0.24 and 0.25, respectively. The karyotype formula was 20 m belonging to 1A of Stebbins category (1971). Fig. 1E shows the karyogram.
| Chromosome pair | Long arm (l) (µm) | Short arm (s) (µm) | c=l+s (µm) | d=l−s (µm) | r=l/s | i=s/c ×100 | Centromeric position |
|---|---|---|---|---|---|---|---|
| 1 | 1.67±0.22 | 1.17±0.18 | 2.84±0.36 | 0.50±o.11 | 1.44±0.12 | 41.08±1.70 | m |
| 2 | 1.50±0.20 | 0.94±0.18 | 2.44±0.32 | 0.56±0.20 | 1.64±0.29 | 38.33±3.81 | m |
| 3 | 1.40±0.19 | 1.02±0.23 | 2.42±0.33 | 0.38±0.27 | 1.43±0.36 | 41.96±6.80 | m |
| 4 | 1.27±0.23 | 0.98±0.26 | 2.25±0.43 | 0.29±0.20 | 1.34±0.25 | 43.27±4.91 | m |
| 5 | 1.23±0.24 | 0.86±0.18 | 2.09±0.35 | 0.38±0.16 | 1.48±0.26 | 40.72±4.57 | m |
| 6 | 1.17±0.20 | 0.81±0.18 | 1.98±0.35 | 0.36±0.10 | 1.47±0.22 | 40.71±3.89 | m |
| 7 | 1.07±0.20 | 0.77±0.17 | 1.84±0.33 | 0.29±0.15 | 1.42±0.28 | 41.80±4.92 | m |
| 8 | 0.90±0.15 | 0.73±0.15 | 1.63±0.24 | 0.17±0.16 | 1.28±0.31 | 44.63±6.21 | m |
| 9 | 0.81±0.17 | 0.67±0.19 | 1.48±0.30 | 0.15±0.17 | 1.29±0.40 | 44.68±5.90 | m |
| 10 | 0.61±0.10 | 0.58±0.16 | 1.19±0.26 | 0.02±0.12 | 1.08±0.24 | 48.71±5.74 | m |
c: total length, d: difference, r: arm ratio and i: centromeric index
Out of 37 species of Pterocarpus, chromosome numbers of only eight species are reported (Table 2). Bhaskar (1981) reported the only somatic chromosome number 2n=22. The present study revealed that the species P. santalinus exhibits a somatic chromosome number of 2n=20 and there is a need for further cytological study in the remaining species for cytological understanding and relationships among species in the genus.
| Sr. No. | Species | Chromosome numbers | References | |
|---|---|---|---|---|
| n | 2n | |||
| 1 | P. erinaceus Poir. | 22 | Miege (1960) | |
| 2 | P. indicus Willd. | 11 | Gill and Husaini (1982) | |
| 22 | Sanjappa and Dasgupta (1981) | |||
| 10 | Sarkar et al. (1975) | |||
| 44 | Yeh et al. (1986) | |||
| 3 | P. macrocarpus Kurz | 22 | Tixier (1965) | |
| 4 | P. marsupium Roxb. | 22 | Kumari and Bir (1990) | |
| 5 | P. rohrii Vahl | 10 | Bawa (1973) | |
| 6 | P. santalinoides L’Hér. ex DC. | 22 | Mangenot and Mangenot (1958) | |
| 7 | P. santalinus L. F. | 22 | Bhaskar (1981) | |
| 20 | Present communication | |||
| 8 | P. acerifolius Willd. | 22 | Sanjappa and Dasgupta (1981) | |
The authors are grateful to the respective Head, Department of Botany and Principal of Balwant College, Vita, and Abasaheb Marathe Arts and New Commerce, Science College, Rajapur for providing the necessary facilities. We are also grateful to DST-FIST and RUSA for the financial assistance. The authors are thankful to Dr. B.M.K. Reddy, Chairman of Andhra Pradesh State Biodiversity Board (APSBB) for his constant support and guidance.
Conceptualization and methodology, RNM, CN, AMR, and GBP; fieldwork, collection of specimens and analyses, CN, RNM, and GBP; cytological work and data analyses, RNM and GBP. All authors have read and agreed to the published version of the manuscript.
