25-08-2017, 09:32 PM
Karyomorphology in Nine Species of Jute
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Karyotype analysis from root tip mitosis yields a wealth of information about the homology
and composition of the genomes, and it has been revealed as the basis of cytogenetic manipulations
in gene transfer and crop improvement (Saha and Datta 2002, Parvatham and Sree Rangasamy
2004, Carvalho et al. 2008). Karyomorphological studies in Jute (Corchorus, Tiliaceae) species,
including the cultivated members C. capsularis L. and C. olitorius L. (extensively used for fibre
production with commercial purposes), are scarce (Banerjee 1932, Rao and Datta 1953, Sharma
and Roy 1958, Datta et al. 1966, Paria and Basak 1973). The small size of chromosomes and
presence of lignin in cell wall produces some difficulties in the hydrolysis of material and improper
staining. For that reasons, photoplate evidence of jute mitotic chromosomes is lacking.
The present paper encompasses karyotype analysis focused in 9 species of Corchorus. On the
one hand, 2 cultivated species were considered (C. capsularis and C. olitorius), and on the other
hand, a representative sample of 7 wild species were selected (C. aestuans L., C. fascicularis Lam.,
C. pseudocapsularis L., C. pseudoolitorius Islam and Zaid, C. tridens L., C. trilocularis L. and
C. urticaefolius Wight and Arnott) all of them growing in India. The applicability of the present
work is the possible exploitation of the desirable wild germplasms into an efficient breeding with
cultivated species-a major thrust area of Jute Industries in India.
The main goals of our study are: i) To obtain a metaphase plate microphotograph framework
by Imaging Techniques and accurate numerical data; ii) To carry out a clustering analysis on the
basis of karyomorphological data to ascertain interrelationship of the studied species.
* Corresponding author, e-mail: dattaanimesh[at]gmail.com
©2009 The Japan Mendel Society Cytologia 74(3): 273–279, 2009
Materials and methods
Samples of Corchorus species (C. capsularis–JRC 321, C. olitorius–JRO 524, C. aestuans–
WCIJ 088, C. fascicularis–WCIJ 150, C. pseudocapsularis CIM 036, C. pseudoolitorius OIN 507,
C. tridens–WCIJ 149, C. trilocularis–KBA 222 and C. urticaefolius–WCIJ 070) were obtained
from germplasms bank of the Central Research Institute for Jute and Allied Fibres, Nilgunj,
Kolkata, West Bengal. Seeds were presoaked in distilled water for 12 h and allowed to germinate
(30°C2°C) in petriplates lined with moist filter papers. Root tips were collected at 12 pm to
12.30 pm, pretreated with 0.05% colchicine solution at 30°C2°C for 3 h and fixed in a propionoalcohol
solution (1 : 3, v:v). Roots were washed in distilled water, digested with 0.5% pectinase for
10–15 min at 16°C and macerated in 1M HCl for 30 min to 1 h. Samples were stained in 2% acetoorcein
for 2 to 3 h and squashed in 45% acetic acid. Three metaphase plates for each species were
analyzed through Image Analyzing System (Micro ImageTM Lite Software-version 4.0 for
Windows, 47N 40155 2000 0515 MAN VG MIX) as suggested by Fukui (1986).
The chromosomes were classified as median (m) and sub median (sm) according to the
position of the centromere (Hirahara and Tatuno 1967). On the basis of chromosome length,
chromosomes of the species studied were morphologically graded into the following types: type A,
long (3.26m m); type B, medium (2.26–3.25m m) and type C, small (1.25–2.25m m). Arm ratio
(short arm length/long arm length), presence of secondary constriction (sc), total haploid chromatin
length, TF% (proportion of short arm in the total chromatin length), relative chromosome length of
each chromosome represented as per cent length of the longest chromosome, and S% (relative
length of shortest chromosome compared to the longest) were also analyzed. Among the
chromosome types, somatic chromosome pairs were graded according to chromosome length.
Karyomorphological data was scored (presence-1, absence-0) in the 9 species and entered into a
binary data matrix. Based on the results of karyotype analysis, proximity matrix was generated for
all possible pair of combinations from Squared Euclidean Distance and used to construct the
dendogram by the unweighted pair group method by arithmetic mean (UPGMA). The data were
analyzed using software SPSS (v. 10.0.1).
Results and discussion
Karyotyping details (somatic chromosome pairs, absolute chromosome length, arm ratio,
F value (%), relative chromosome length (%) and centromeric nature of the chromosomes) of
individual chromosome pair in 9 species of Corchorus are listed in Table 1. The chromosome
number, karyotype formula, TF%, haploid chromatin length and S% of the species are also
summarized in Table 2. Metaphase plates and their related ideograms of the studied species are
enclosed in Figs. 1–20.
Karyotype analysis revealed the chromosome number 2n14 for all species (excepting
C. fascicularis with 2n28 chromosomes in 11.54% cells, 26 metaphase plates analyzed), but with
distinct karyotypes. The karyotypes exhibited the formation of 3 (C. fascicularis) 2 (C. capsularis,
C. olitorius, C. aestuans, C. pseudocapsularis, C. pseudoolitorius) and 1 (C. tridens, C. trilocularis
and C. urticaefolius) morphologically distinct chromosome types. The somatic chromosome
complement of 9 species of Corchorus had 1 pair of chromosomes with secondary constriction in
the longest pair, with the exception of C. pseudocapsularis (Figs. 11–12, sc-C1C1). Satellites were
always associated with short arm. The karyotypes highlighted prevalence of median chromosomes
(F%: 40.00–50.00%) though there were few sub-median (F%: 31.00–39.15%) types. Analysis of
2n28 chromosomes (Figs. 9–10) in C. fascicularis (karyotype formula: 4Am
sc16Bm8Cm,
absolute chromosome length–1.90m m to 3.74m m; TF%–45.37, S%–50.80) suggested duplication
of 2n14 chromosomes in few cells. All chromosome pairs in C. fascicularis, C.