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Cytology of Aloe trinervis (Asphodelaceae): A Newly Described Species from Indian Desert
2023 年 88 巻 1 号 p. 51-53
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2023 年 88 巻 1 号 p. 51-53
Aloe trinervis C.S.Purohit, Kulloli & Suresh Kumar has only species described from India and has narrow distribution in the state of Rajasthan. A. trinervis is related to the A. vera (L.) Burm.f. but very distinct by the vegetative and reproductive characteristics. Thus, in the present investigation, somatic chromosome number and karyotype analysis are reported for the first time in A. trinervis. The karyotype of the species is the 1C asymmetric category of Stebbins classification and the karyotypic formula is 2n=14=6sm+8st.
Aloe L. is one of the largest genera in the family Asphodelaceae having 600 species and it is distributed to the old world (Carter et al. 2011). Among the genus, most of the species are endemic to African countries (Crouch et al. 2013, Dessalegn 2013). Genus Aloe is represented by single species i.e., A. vera to the India in wild (Mao and Dash 2020). The species are mainly distributed to dry to arid zones. Recently, Kumar et al. (2020) described a new species of Aloe, A. trinervis C.S.Purohit, Kulloli, and Suresh Kumar from the Indian desert. The newly described species is only known from four localities of the Bikaner district of Rajasthan state; thus, it is included under the endangered category of IUCN (Kulloli et al. 2020) and shows affinities with A. vera. However, it is very distinct by many morphological characteristics and slightly sturdy habit than A. vera. Thus, cytological characteristics will be useful to understand the interrelationships between A. trinervis and A. vera. In the present communication, we have done the basic karyomorphological analysis of A. trinervis for the first time.
The material of A. trinervis for the present investigation was collected from the Shivbari-Jorbir area, Bikaner district, Rajasthan. The voucher specimen has been deposited in the Herbarium, Arid Zone Regional Centre, Botanical Survey of India, Jodhpur (BSJO).
The plants were grown in earthen pots in the botanical garden, Arid Zone Regional Centre, Jodhpur. Root tips were obtained from grown plants. Mitosis was studied from healthy root tips (5 to 12 mm) pretreated with a saturated aqueous solution of p-dichlorobenzene for 3–4 h at 9±3°C. The root tips were squashed in 2% propionic orcein for staining. A Leica DM750 microscope with attached an ICC50 W camera was used for taking pictures of chromosomes from freshly prepared slides. The method of Levan et al. (1964) was used for karyotype analysis. Ten plates with well-separated somatic chromosomes were used for analysis. The degree of karyotype asymmetry has been determined by using indices such as intrachromosomal asymmetry index (A1), interchromosomal asymmetry index (A2), asymmetry index (Ai), coefficient of variation of chromosome lengths (CVCL), coefficient of variation of the centromeric index (CVCI), gradient index (GI), symmetric index (SI), total chromosome length of haploid complement (THCL), and total form percent (TF%) (Zarco 1986, Paszko 2006) and the category of Stebbins (1971).
The somatic chromosome number of A. trinervis was observed 2n=14 (Fig. 1B, C). Karyotype analysis of the species is given in Table 1 and the basic parameters of the karyotype are given in Table 2.
| Chromosome pair | Length of the long arm (l) (µm) | Length of the short arm (s) (µm) | Total length c=l+s (µm) | d=l−s | Arm ratio r=l/s | Centromeric index i=s/c×100 | Centromeric position according to “i” |
|---|---|---|---|---|---|---|---|
| I | 16.25±4.99 | 4.08±1.27 | 20.33±6.21 | 12.18 | 3.99 | 20.05 | st |
| II | 14.86±4.35 | 3.23±0.87 | 18.10±5.11 | 11.63 | 4.60 | 17.87 | st |
| III | 13.74±3.78 | 2.87±0.96 | 16.61±4.61 | 10.87 | 4.79 | 17.27 | st |
| IV | 11.87±3.05 | 2.89±0.74 | 14.75±3.74 | 8.98 | 4.11 | 19.57 | st |
| V | 4.36±1.08 | 1.63±0.41 | 5.99±1.46 | 2.73 | 2.67 | 27.23 | sm |
| VI | 3.66±0.97 | 1.57±0.31 | 5.24±1.26 | 2.09 | 2.33 | 30.00 | sm |
| VII | 3.05±0.72 | 1.50±0.42 | 4.55±1.07 | 1.55 | 2.03 | 32.98 | sm |
| Parameters | Values |
|---|---|
| THCL | 85.56 |
| Range of TCL% | 5.3 to 23.8 |
| TF% | 20.8 |
| SI | 26.2 |
| GI | 22.4 |
| Range SC-LC (µm) | 4.55 to 20.33 |
| CVCL | 55.1 |
| CVCI | 27.0 |
| Ai | 14.9 |
| A1 | 0.19 |
| A2 | 0.55 |
| Karyotype formula (K) | 6sm+8st |
| Classification of Stebbins (1971) | 1C |
TCLH: Total chromosome length of haploid compliment, TCL%: Total haploid chromosome length percent, TF%: Total form percent, SI: Symmetric Index, GI: Gradient Index, SC: Small chromosome, LC: Large Chromosome, CVCL: Coefficient of variation (CV) of chromosome lengths, CVCI: Coefficient of variation (CV) of the centromeric index, Ai: Asymmetry index, A1: Intrachromosomal asymmetry index, A2: Interchromosomal asymmetry index.
The genus Aloe is diversified and distributed mainly in drier areas of the old world, especially in Africa. The genus is very distinct by morphological characteristics and shares some common cytological characters i.e., basic chromosome number (x)=7 and has bimodal karyotype i.e., six small chromosomes and eight large chromosomes (Sapre 1978, Vij et al. 1980, Takahashi et al. 1997, Brandham and Doherty 1998, Gunjan and Roy 2010).
TF% in A. vera was reported at 22.21 by Gunjan and Roy (2010); 24.83 and 20.64 by Nejatzadeh-Barandozi and Akbari (2013), while in the present investigation we have got 20.8 in A. trinervis. Gunjan and Roy (2010) reported small chromosome (SC)=4.27 µm and large chromosome (LC)=15.76 µm in A. vera; A. trinervis has a slight variation in small chromosome i.e., 4.55 µm and more variation in the length of large chromosome i.e., 20.33 µm. Gunjan and Roy (2010) reported CVCL=c 55, Ai=15.6, and A2=0.52 in A. vera; we got related results in A. trinervis of these indices i.e., 55.1, 14.9, and 0.55, respectively. However, they reported CVCI=c 30 and A1=0.64 in A. vera vary in A. trinervis i.e., 27 and 0.19, respectively. Gunjan and Roy (2010) and Chaudhari and Chaudhary (2012) reported 3B class of Stebbins classification in A. vera while A. trinervis categorized under the 1C class.
Aloe trinervis although very distinct by morphological characteristics from A. vera (Table 3). But shares many common cytological characteristics such as somatic chromosome number 2n=14, bimodal karyotype, and sm and st types of chromosomes (Table 2). However, Stebbins’s classification of both species varies, i.e., A. trinervis=1C while A. vera=3B. It may be because of variations in the length of chromosomes.
| Sr. no | A. trinervis | A. vera. |
|---|---|---|
| 1 | The leaf is light green with yellowish spots | The leaf is light green with reddish spots |
| 2 | Marginal teeth of the leaf recurved with brown colored | Marginal teeth of leaf deltoid with white colored |
| 3 | The inflorescence is always four to seven-branched (Fig. 1A) | Inflorescence unbranched rarely two branched |
| 4 | Flowers pale green with light brownish in middle | Flowers orange-yellow |
| 5 | Flowering and fruiting period June to October | Flowering and fruiting period November to February |
The authors are thankful to the Principal, HPT Arts & RYK Science College, Nashik, and Director, Botanical Survey of India, Kolkata for providing facilities and moral support to carry out this work.
