2024 Volume 89 Issue 2 Pages 153-156
The detailed karyomorphological studies were undertaken for two varieties of Coix lacryma-jobi L., namely C. lacryma-jobi var. puellarum (Balansa) E.G. Camus & A. Camus and C. lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf. The present communication deals with meiotic and somatic chromosome numbers, total chromosome length, arm ratio, centromeric position, and Stebbins classification. Somatic chromosome number 2n=20 and meiotic number n=10 were observed in both varieties. Karyotypes of both varieties of C. lacryma-jobi fell under the 4A asymmetric category of Stebbins classification. Chromosome number and karyomorphology of C. lacryma-jobi var. puellarum are reported for the first time.
Genus Coix L. is well-known for its fodder and rich nutritious food. The utricles are also used for ornamentation of cloths and jewelry by tribal people. The genus is taxonomically very difficult because it shows a high range of variation among its taxa. Earlier the genus comprised several species but now has only three species and three varieties namely, Coix aquatica Roxb., C. gasteenii B.K.Simon, C. lacryma-jobi L., C. lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf, C. lacryma-jobi var. puellarum (Balansa) E.G.Camus & A.Camus, and C. lacryma-jobi var. stenocarpa Oliv. (Madhav and Gosavi 2022a). Because of high variations in morphology and habitat in the genus Coix, many workers have done cytological works in different taxa (Koul and Paliwal 1964; Rao 1977; Clayton 1981; Sapre et al. 1985; Christopher and Mini 1988; Christopher and Jacob 1990, 1991; Han et al. 2004; Barve and Sangeetha 2008; Gosavi and Yadav 2011; Rao and Nirmala 2011; Cai et al. 2014), but now most of the taxa subsumed and few kept under variety rank. Thus, to understand the species, variety, and variations of the Coix need to thoroughly work on cytology. The present communication is the first step in carrying out the basic karyomorphology of C. lacryma-jobi var. ma-yuen and C. lacryma-jobi var. puellarum.
The utricles and plant specimens of C. lacryma-jobi var. puellarum (Balansa) E.G. Camus & A.Camus and C. lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf (Fig. 1A, D) for the present investigation were collected from the Upper Sichey in Sikkim and Mawblang in Meghalaya, respectively. The voucher specimens have been deposited in the Herbarium, Department of Botany, Shivaji University Kolhapur (SUK).
Coix lacryma-jobi var. puellarum (Balansa) E.G. Camus & A.Camus (A–C, G) and C. lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf. (D–F, H). (A, D) inflorescences and utricles; (B, E) meiotic chromosome plates; (C, F) somatic chromosome plates; (G, H) idiograms. Scale bars=10 µm (B, C, E, F) and 2 µm (G, H).
Root tips were obtained from germinated seeds (utricle) for mitotic study. Seeds germinated between the moist blotting papers in the glass Petri plates. 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 an attached 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 studied for analysis. The degree of karyotype asymmetry has been determined by using Intrachromosomal asymmetry index (A1), Interchromosomal asymmetry index (A2), Asymmetry index (Ai), Coefficient of variation of the centromeric index (CVCI), Coefficient of variation of chromosome lengths (CVCL), Gradient Index (GI), Symmetric Index (SI), Total haploid chromosome length percent (TCL%), Total chromosome length of haploid complement (TCLH), Total form percent (TF%), indices (Zarco 1986, Paszko 2006), and the categories of Stebbins (1971).
For meiotic studies early budding male spikelets were fixed in a Carnoy’s fluid in the morning time (7:00 a.m to 7:15 a.m.); anthers were separated from fixed spikelets and squashed in 2% propionic-orcein. Results were obtained from mounted slides.
C. lacryma-jobi var. ma-yuen and C. lacryma-jobi var. puellarum shares common meiotic chromosome number n=10 (Fig. 1B, E), somatic chromosome number 2n=20 (Fig. 1C, F), karyotypic formula 2n=20=20m and 4A category of Stebbin’s classification (Table 3). Karyotype analysis of the C. lacryma-jobi var. ma-yuen is given in Table 1 and C. lacryma-jobi var. puellarum is given in Table 2. The basic parameters of the karyotype of both varieties are given in Table 3. Idiograms of both taxa have been drawn in Fig. 1G and 1H, respectively.
| Chromosome pair | Length of long arm (l) (µm) | Length of short arm (s) (µm) | Total length c=l+s (µm) | d=l–s (µm) | Arm ratio r=l/s | Centromeric index i=s/c×100 | Centromeric position according to “i” |
|---|---|---|---|---|---|---|---|
| I | 2.41±0.54 | 1.77±0.38 | 4.18±0.62 | 0.64 | 1.36 | 42.37 | m |
| II | 2.07±0.26 | 1.75±0.27 | 3.82±0.48 | 0.33 | 1.19 | 45.74 | m |
| III | 2.12±0.38 | 1.52±0.13 | 3.64±0.47 | 0.60 | 1.39 | 41.77 | m |
| IV | 2.00±0.36 | 1.45±0.22 | 3.45±0.42 | 0.54 | 1.37 | 42.14 | m |
| V | 1.98±0.40 | 1.37±0.12 | 3.35±0.45 | 0.61 | 1.45 | 40.88 | m |
| VI | 1.84±0.29 | 1.34±0.28 | 3.17±0.43 | 0.50 | 1.37 | 42.13 | m |
| VII | 1.68±0.23 | 1.38±0.21 | 3.07±0.41 | 0.30 | 1.22 | 45.12 | m |
| VIII | 1.71±0.22 | 1.23±0.22 | 2.94±0.38 | 0.49 | 1.40 | 41.74 | m |
| IX | 1.63±0.23 | 1.24±0.23 | 2.87±0.43 | 0.39 | 1.31 | 43.20 | m |
| X | 1.46±0.24 | 1.08±0.13 | 2.54±0.36 | 0.38 | 1.35 | 42.56 | m |
| Chromosome pair | Length of long arm (l) (µm) | Length of short arm (s) (µm) | Total length c=l+s (µm) | d=l–s (µm) | Arm ratio r=l/s | Centromeric index i=s/c×100 | Centromeric position according to “i” |
|---|---|---|---|---|---|---|---|
| I | 2.03±0.30 | 1.60±0.33 | 3.63±0.42 | 0.43 | 1.27 | 44.02 | m |
| II | 1.85±0.18 | 1.59±0.18 | 3.44±0.35 | 0.26 | 1.16 | 46.20 | m |
| III | 1.82±0.26 | 1.54±0.22 | 3.35±0.35 | 0.28 | 1.18 | 45.79 | m |
| IV | 1.72±0.19 | 1.53±0.15 | 3.25±0.30 | 0.19 | 1.12 | 47.06 | m |
| V | 1.73±0.16 | 1.41±0.19 | 3.14±0.24 | 0.32 | 1.23 | 44.91 | m |
| VI | 1.63±0.11 | 1.40±0.21 | 3.04±0.21 | 0.23 | 1.17 | 46.17 | m |
| VII | 1.61±0.16 | 1.28±0.12 | 2.89±0.25 | 0.32 | 1.25 | 44.44 | m |
| VIII | 1.54±0.14 | 1.25±0.17 | 2.79±0.28 | 0.28 | 1.23 | 44.93 | m |
| IX | 1.47±0.16 | 1.12±0.14 | 2.59±0.26 | 0.34 | 1.31 | 43.35 | m |
| X | 1.44±0.19 | 1.01±0.19 | 2.44±0.27 | 0.43 | 1.43 | 41.24 | m |
| Indices | Coix lacryma-jobi var ma-yuen | C. lacryma-jobi var puellarum |
|---|---|---|
| TF% | 42.782 | 35.172 |
| SI | 74.770 | 54.255 |
| GI | 60.747 | 46.478 |
| CVcl | 14.778 | 27.696 |
| CVci | 3.589 | 34.290 |
| Ai | 0.530 | 9.497 |
| A1 | 0.698 | 0.492 |
| A2 | 0.148 | 0.276 |
| Range of TCL% | 5.30–23.79 | 7.99–11.86 |
| THCL | 33.04 | 30.56 |
| Karyotype formula | 2n=20m | 2n=20m |
| Classification of Stebbins (1971) | 4A | 4A |
C. lacryma-jobi var. lacryma-jobi is widely distributed throughout the tropics in different habitats thus, the taxon shows high variation in its morphology especially in its size, shape, and colors of utricle as compared to other varieties. While, C. lacryma-jobi var. ma-yuen is cultivated in China, Myanmar, and northeast India for its medicinal and rich potential food value, and C. lacryma-jobi var. puellarum is distributed in Southeast Asia (Xi et al. 2016; Madhav and Gosavi 2022a, b). In the C. lacryma-jobi different cytotypes were reported such as n=5 and 10; 2n=10, 16, 20, 21, 22, 27, 29, 30, 31, 39, 40, and 41 (Koul and Paliwal 1964; Koul 1965; Rao 1973, 1977; Venkateshwaralu et al. 1976; Christopher and Mini 1988; Christopher and Jacob 1990; Christopher et al. 1989; Rao and Nirmala 1993; 1994a, b, 2001, 2011; Christopher et al. 1995a, b, 1996, 1997; Nirmala 2003; Han et al. 2004; Barve and Sangeetha 2008; Gosavi and Yadav 2011; Cai et al. 2014). Among them 2n=20 is dominated number in the C. lacryma-jobi (Liu et al. 2020) and the same result we have got in the present investigation of C. lacryma-jobi var. ma-yuen and C. lacryma-jobi var. puellarum. The chromosome number in C. lacryma-jobi var. ma-yuen has been reconfirmed as reported by Mehra (1882) and Venkateswarlu et al. (1976), but we did not get 2n=30 as reported by Christopher and Jacob (1989, 1990). Chromosome number of lacryma-jobi var. puellarum report here for the first time.
Christopher and Jacob (1989) reported that ACL=3.25 µm, the range of chromosome size=2.66 to 3.91 µm, TCL=97.72 µm, chromosome formula=2M+13m, and the class of Stebbins classification=1A in C. lacryma-jobi var. ma-yuen. However, in the present investigation, we have got nearby similar ACL=3.30 µm and the range of chromosome size=2.54–4.18 µm but differences in TCL=66.08 µm, chromosome formula was 10m, and the class of Stebbins classification=4A. The present work agreed with Liu et al. (2020) for the statement of predominant chromosome number 2n=20 in C. lacryma-jobi. C. lacryma-jobi var. puellarum (Balansa) E.G. Camus & A. Camus, and C. lacryma-jobi var. ma-yuen (Rom.Caill.) Stapf. showed common category 4A of the Stebbins classification, while earlier workers reported category 1A in C. lacryma-jobi var. ma-yuen (Christopher and Jacob 1989). Based on the above results, it is confirmed that C. lacryma-jobi var. ma-yuen showed a similar ratio between the smallest and largest chromosomes. Due to the variable length of the chromosomes, the category has changed in the present work to 4A, which may be the key factor for the observed morphological variations.
Tremendous cytogenetical and evolutionary work has been done on the genus Coix, but the intrageneric categories of the genus remain doubtful. Therefore, it is necessary to work on the basic karyomorphology related to the classical taxonomy of the genus Coix.
Authors (KVCG and NAM) are grateful to Science and Engineering Research Board, (SERB), New Delhi for providing financial assistance (Project file No. CRG/2018/001381). The authors are also thankful to the heads of the respective institutes for providing the necessary laboratory facilities. We thank the two anonymous reviewers for their valuable comments and for improving the manuscript.
Nilesh Appaso Madhav: methodology, performing experiments, data analysis, and revising the manuscript. Arun Nivrutti Chandore: work design, data analysis, and drafting and revising the manuscript. Kumar Vinod Chhotupuri Gosavi: conceptualization, work design, investigation, drafting, and revising the manuscript.
