2. 440 R. C. Gupta et al. Cytologia 78(4)
Results
Details of meiotic chromosome numbers along with meiotic behaviour in each studied species
is as follows.
C. carinatum
Cytomorphological studies are made on 12 accessions of which plant no. 1 shows more resem-
blance to C. carinatum and plant no. 12 shows the minimum resemblance. Meiotically, all depict 2n=18
(Fig. 1) with 9 : 9 balanced chromosomal distribution during anaphases (Fig. 2).
Interestingly, all the plants are found to be heterozygous for reciprocal translocations involving 4–8
chromosomes in structural hybridity. Mostly, ring-shaped bivalents with two chiasmata and rod shaped
bivalents with one chiasma are observed. Besides bivalents, ring- and chain-shaped quadri-valents and
hexavalents are also observed with 4–3 and 6–5 chiasmata, respectively (Figs. 3, 4). The orientation of these
quadrivalents is both adjacent and successive with distal localization of chiasmata. Mostly, there is normal
distribution of chromosomes during anaphases and telophases, but a few PMCs show laggards and bridges
(Figs. 5–7) with abnormal microsporogenesis (Fig. 8). Pollen fertility is found to be high (82–98%) or low
(45–75%) in different accessions. Meiotic con-figurations vary from 1–2 VI, 1–2 IV, 2–9 II, and 0–2 I in
different populations (Table 1). Chiasmata frequency varies from 14.0–16.8 in 12 accessions (Table 2).
C. cinerariaefolium
Meiosis is normal with clear 9 bivalent formation, which leads to balanced segregation of
chromosomes and normal microsporogenesis resulting in high pollen fertility (Fig. 9). Mostly, bi-
valents are ring-shaped with an average of 16.2 chiasmata frequency per PMC.
C. coronarium
Cytological studies made on four different types of plants with white radiate (P-1), white ligu-late
(P-2), yellow radiate (P-3), and yellow ligulate (P-4) capitula. All embrace the same chromo-some
number of 2n=18 (Fig. 10). White radiate plants (P-1, P-2) show normal bivalent formation. In P-3, four
chromosomes are involved in reciprocal translocations (Fig. 11). The bivalents are mostly ring-shaped.
In P-3, 8.88% of the chromosomes show multiple associations. White ligulate plants (P-2) show PMCs
with normal bivalent formation except for a few with two univalents along with eight bivalents (Fig. 12).
Yellow radiate plants (P-3) show normal nine bivalent formation without any structural heterozygosity,
though in one cell, one trivalent along with one univalent and seven bivalents are observed. Meiosis is
perfectly normal with normal course of microsporogenesis. Yellow ligulate plants (P-4) show PMCs
with structural heterozygosity involving four chromo-somes. Some of the PMCs (4.5%) show 1–2
laggards during T-II (Fig. 13). Microsporogenesis is normal with high pollen fertility.
C. leucanthemum
Cytological studies on the species revealed the presence of 2n=36 at different stages of meio-sis
(Fig. 14). The course of meiosis is highly abnormal due to many irregularities during meiosis I and
meiosis II (Table 3). Meiotic abnormalities are in the form of non-synchronized bivalents or
chromosomes at M-I/II, chromatin stickiness at M-I, laggards and bridges during anaphases and
telophases, and some cells contain both lagging fragments and chromatin bridges (Figs. 15, 16). Further,
it leads to abnormal microsporogenesis in the form of 1–3 micronuclei (Fig. 17). Aside from all these
meiotic anomalies, pollen fertility is found to be high (89%).
3. 2014 Cytogenetical Studies in Seven Ornamental Species of Chrysanthemum (Asteraceae) 441
Figs. 1–17. Male meiosis in Chrysanthemum spp. (Scale bar = 10 µm). 1–8. C. carinatum 1. PMC at M-I
with 9II. 2. PMC at M-II with 2n=18. 3. PMC at M-I with 2IV+5II. 4. PMC at M-I with 1VI+6II. 5.
PMC at T-I with laggard. 6. PMC at T-II with laggards. 7. PMC at T-I with bridge. 8. Triad.
9. C. cinerariaefolium PMC at M-I with 9II. 10–13. C. coronarium 10. PMC at diakinesis with
9II. 11. PMC at M-I with 1IV+7II. 12. PMC at M-I with 8II+2I. 13. PMC at T-II showing lag-gards.
14–17. C. leucanmthemum 14. PMC at M-I with 18II. 15. PMC at T-I with bridge. 16.
PMC at A-I with laggards. 17. PMC at T-II showing micronuclei.
C. morifolium
Meiotical analysis shows 2n=36 with a lot of structural heterozygosity in PMCs with the for-
mation of quadrivalents (0.75), trivalents (0.08), and univalents (0.41) besides bivalents (16.01) per
PMC (Figs. 18, 19).
C. paludosum
Meiosis shows 2n=18 which is characterized by the presence of 0–1 VI, 6–9 II, and 0–2 I (Figs. 20,
21). The quadrivalents are always ring-shaped with four chiasmata whereas, the bivalents may be either
ring- or rod-shaped. Chromosomal distribution is usually normal but a few cells show 1–2 laggards at A-
I (Figs. 22, 23), which lead to multipolarity at T-II (Fig. 24). These abnormalities during anaphases are
reflected in the form of low pollen fertility (60.8%).
4. 442 R. C. Gupta et al. Cytologia 78(4)
Table 1. Overall chromosomal associations in 12 accessions of C. carinatum (2n=18).
Accession Number of Chromosomal configuration
Plant morphology PMCs
no.
VI IV II I
observed
1 White ray florets with purple disc 16 Average frequency/PMC 0.06 0.37 8.06 –
florets
% of chromosomes involved 2.08 8.33 89.59 –
2 Creamish white ray florets with 22 Average frequency/PMC 0.05 0.4 8.04 –
purple disc florets
% of chromosomes involved 1.52 9.09 89.39 –
3 Yellowish-red ray florets with red 16 Average frequency/PMC 0.12 0.50 7.62 –
colour disc florets
% of chromosomes involved 4.16 11.11 84.73 –
4 White ray florets with complete red 20 Average frequency/PMC 0.05 0.25 8.35 –
stripe at base, purple disc florets
% of chromosomes involved 1.66 5.56 92.77 –
5 White ray florets with broad maroon 20 Average frequency/PMC – 0.55 7.85 0.10
stripe at base
% of chromosomes involved – 12.22 87.23 0.55
6 Purplish ray florets with broad maroon 20 Average frequency/PMC 0.05 0.35 8.15 –
stripe at base, purple disc florets
% of chromosomes involved 1.66 7.77 90.56 –
7 Light purplish ray floret with broad 16 Average frequency/PMC 0.11 0.37 8.25 –
maroon stripe at base, disc florets
% of chromosomes involved 0.21 8.23 91.67 –
have purple
8 White ray florets with incomplete red 18 Average frequency/PMC 0.11 0.33 8.00 –
stripe at base
% of chromosomes involved 3.70 7.42 88.88 –
9 White ray florets with relatively less 21 Average frequency/PMC 0.47 0.28 8.28 –
complete red stripe at base
% of chromosomes involved 1.59 6.35 92.06 –
10 White ray floret with much less 16 Average frequency/PMC 0.31 0.56 8.69 –
shading of red ray floret
% of chromosomes involved 10.41 12.50 77.09 –
11 White ray florets with yellow reddish 14 Average frequency/PMC 0.12 0.37 7.75 0.14
disc floret
% of chromosomes involved 4.16 8.37 86.12 0.79
12 Yellow ray florets with yellow disc. 16 Average frequency/PMC 0.12 0.37 7.75 0.12
Florets but red dots are observed in
% of chromosomes involved 4.16 8.37 86.12 1.38
disc floret
Total: 215 Average frequency/PMC 0.15 0.33 7.94 0.02
C. segetum
Meiosis shows 2n=36 (Figs. 25, 26). Most of the bivalents are ring-shaped with two
chiasmata, and 1–3 are rod-shaped with single chiasma. Chromosomal distribution is usually
normal but a few cells show 1–2 laggards at A-I and T-II (Figs. 27–29), which lead to multipolar T-
II (Fig. 28). Microsporogenesis is abnormal with formation of dyads (Figs. 29–31). These
abnormalities resulted in low pollen fertility (71%).
The overall chromosomal associations in seven species of genus Chrysanthemum is compiled in Table 4.
C. cinerariaefolium and C. leucanthemum show pure bivalent formation. Besides biva-lents, quadrivalents,
trivalents, and univalents are also observed in two species viz. C. carinatum and C. morifolium. Trivalents are
not found in the rest of the species. Chiasmata frequency in Chrysanthemum species (Table 5) depict that it
varies from 15.2–16.2 per PMC in diploids (2n=18)
5. 2014 Cytogenetical Studies in Seven Ornamental Species of Chrysanthemum (Asteraceae) 443
Table 2. Analysis of chiasma frequency in C. cariantum accessions.
Chromosomal configuration
Total
Accession VI IV II chiasmata
(T
XTA
)
6XTA
5XTA
4XTA
3XTA
2XTA
1XA
1 0.006 0.06 0.12 0.25 6.93 1.25 16.4
2 – 0.04 0.13 0.27 5.54 2.5 15.1
3 – 0.12 – 0.50 6.75 0.75 16.8
4 0.50 – – 0.25 7.40 0.90 16.7
5 – – 0.55 – 5.55 2.30 14.9
6 – 0.05 0.25 – 7.00 1.15 16.5
7 0.23 – 0.37 – 5.93 2.31 16.8
8 – 0.10 0.20 0.10 6.60 0.80 15.9
9 – 0.04 0.04 0.20 4.52 1.61 16.1
10 – 0.31 0.43 0.06 5.50 1.81 15.7
11 – 0.21 0.14 0.21 5.92 1.64 15.7
12 – 0.12 0.25 0.12 6.50 1.50 14.0
Table 3. Data on meiotic abnormalities in C. leucanthemum.
PMCs showing PMCs showing PMCs showing
PMCs showing PMCs showing
bridges at laggards at
Total non-synchronized non-synchronized chromatin
PMCs bivalents at chromosomes at stickiness at
A-I/T-I A-II/T-II A-I/T-I A-II/T-II
M-I M-II M-I
Number 14 (51) 9 (48) 33 (51) 5 (90) 4 (129) 14 (90) 31 (129)
%age 27.4 18.7 64.7 5.5 3.1 15.5 24.0
Figure in parentheses represents total number of PMCs analyzed
and 33.9–59.4 per PMC in tetraploids (2n=36).
Discussion
The presently studied population of C. carinatum is diploid with 2n=18. This report is con-firmed by a
large number of researchers from India (Rana and Jain 1965, Chaudhuri et al. 1976) and abroad (vide:
Fedorov 1969). However, Bergman (1952) reported the presence of aneuploids and polyploid cytotypes
(2n=18, 26, 36, 37) in the species. The tetraploid and diploid cytotypes were reported by Shimotomai and Hara
(1935) and Tahara (1915). For C. cineariaefolium, the pres-ent report of 2n=18 confirms the earlier reports of
Chaudhuri et al. (1976). The present report of 2n=18 in C. coronarium is in conformity with the earlier reports
of a large number of researchers from India (Gupta 1969, Gupta and Gill 1984) and abroad (vide: Fedorov
1969). The tetraploid cy-totype of C. segetum (2n=36) is in line with the previous reports of some researchers
from India (Mehra and Remanandan 1974, Gupta and Gill 1983, 1989) and abroad (vide: Fedorov 1969). The
present report of 2n=36 for C. leucanthemum is in conformity with the previous reports by many researchers
from India and the Western Himalayas (Mehra et al. 1965, Mehra and Remanandan 1974, Gupta and Gill
1989). Besides this chromosome number, 2n=18 is also reported. From out-side, a well established
intraspecific polyploid series of 2x, 4x, 6x, 8x, and 10x with 2n=18, 36, 54, 72 and 90 is reported. The Indian
populations are known with chromosome numbers of 2n=18 and 36 only. Thus, the species shows intraspecific
polyploidy based on x=9. Gupta and Gill (1984) stud-ied Shimla populations and observed multivalents in the
form of 0–4 quadrivalents and 0–1 triva-lent in addition to the normal 10–18 bivalents and 0–2 univalents in
tetraploid populations. In the
6. 444 R. C. Gupta et al. Cytologia 78(4)
Figs. 18–31. Male meiosis in Chrysanthemum spp. (Scale bar = 10 µm). 18, 19. C. morifolium PMCs show-
ing 2n=36. 20–24. C. paludosum 20. PMC at M-I with 9II. 21. PMC at M-I with 1IV+7II. 22.
PMC at T-I with laggards. 23. PMC at T-II with laggards. 24. PMC at T-II with 5 poles. 25–
31. C. segetum 25, 26. PMCs at diakinesis with 2n=36. 27. PMC at M-II with 2n=36. 28.
PMC at A-I with laggard. 29. PMC at T-II with laggard. 30. Dyad. 31. PMC showing multi-
polarity at T-II.
present case, however, no clear-cut multivalent is observed, but the rest of the meiotic course is sim-ilar with
appreciably high pollen fertility. Gupta and Gill (1984) pointed out that between diploid and tetraploid
cytotypes, the tetraploids are found to be more luxuriant and robust with less dentate leaves, larger ray florets,
and large-sized achenes, pollen, and stomata as compared to diploids.
Similarly, the present report of tetraploid cytotype in C. morifolium also confirms the previous re-ports of the
species from India (Srivastava 1983, Gupta and Gill 1984). The chromosome report of 2n=18 in C. paludosum
is the first chromosome report for the species. The tetraploid cytotype of C. segetum (2n=36) is in line with the
previous reports of some researchers from India (Mehra and Remanandan 1974, Gupta and Gill 1983, 1989)
and abroad (vide: Fedorov 1969).
In the genus Chrysanthemum, 107 species are known cytologically, of which 50 species are at diploid
level and the remaining species show polyploid cytotypes. In these species, the chromo-some numbers vary
from 2n=10 to 2n=198 (C. lacustre). All the species of the genus are based on x=9. Thus, the genus is
monobasic. Among the polyploid cytotypes, hexaploids are the most com-mon (30%), followed by tetraploids
(27.5%) and octaploids (20%). Additionally, unbalanced poly-
7. 2014 Cytogenetical Studies in Seven Ornamental Species of Chrysanthemum (Asteraceae) 445
Table 4. Overall chromosomal associations in seven species of genus Chrysanthemum.
Taxa
Chromosome Chromosomal configuration
number (2n) IV III II I
C. carinatum 18 Average frequency/PMC 0.15 0.33 7.94 0.02
% of chromosomes involved 3.21 8.77 88.01 0.90
C. cinerariaefolium 18 Average frequency/PMC – – 18.00 –
% of chromosomes involved – – 100 –
C. coronarium 18 Average frequency/PMC 0.4 – 8.1 0.2
% of chromosomes involved 8.88 – 9.0 1.12
C. leucanthemum 36 Average frequency/PMC – – 18.00 –
% of chromosomes involved – – 100 –
C. morifolium 36 Average frequency/PMC 0.75 0.08 16.10 0.41
% of chromosomes involved 8.33 0.69 89.81 1.15
C. paludosum 18 Average frequency/PMC 0.64 – 7.58 0.23
% of chromosomes involved 14.37 – 84.33 1.30
C. segetum 36 Average frequency/PMC 0.55 – 16.7 0.2
% of chromosomes involved 6.19 – 93.20 0.61
Table 5. Chiasmata frequency in seven species of Chrysanthemum.
Chromosomal configuration
Total
Species VI IV III II chiasmata
(TXTA)
6XTA 5XTA 4XTA 3XTA 2XTA 2XTA 1XA
C. carinatum 0.24 0.11 0.248 0.21 – 6.17 1.54 15.8
(2n=18)
C. cinerariaefolium – – – – 7.2 1.8 16.2
(2n=18)
C. coronarium – – 0.365 0.05 – 6.05 1.92 15.2
(2n=18)
C. leucanthemum – – – – 27.64 35.5 59.4
(2n =36)
C. morifolium – – 0.75 – 0.08 15.83 0.91 34.5
(2n=36)
C. paludosum – – 0.64 – – 5.94 1.64 16.1
(2n=18)
C. segetum – – 0.5 – – 15.0 1.16 33.9
(2n=36)
ploids, i.e. triploids and pentaploids, are present in some species. Intraspecific polyploid cytotypes
on x=9 are present in 23 species. Aneuploid cytotypes are available in 13 species. B-chromosomes
are reported in eight species. Further, karyotypic chromosome dimorphism is reported in some of
the species of Chrysanthemum.
All the presently studied plants of C. carinatum are found to have multiple associations of four or six
chromosomes and are thus heterozygous for reciprocal translocations. The overall average chromosomal
association in these plants comes out to be 0.15VI + 0.33IV + 7.94II + 0.02I. Paria and Pradhan (1970), while
analysing the heterozygosity in C. carinatum, reported that 36.7% of the
8. 446 R. C. Gupta et al. Cytologia 78(4)
plants are homozygous with nine bivalent formation, 27.9% have one quadrivalent and seven biva-lents, 7.3%
have one hexavalent with five bivalents, 11.76% have two quadrivalents with five biva-lents, and the
remaining 16.1% have one hexavalent with one quadrivalent and four bivalents.
C. coronarium is found to have a high incidence of heterozygosity in plants with a radiate head,
whereas those with a ligulate head are found to be normal. Whether the absence of heterozygosity has
anything to do with the ligulate nature of the head cannot be ascertained on the basis of the present
studies. Gupta and Gill (1985) studied the cytogenetics of C. coronarium and concluded that
heterozygosity is high (40%) in the radiate type, but is very low in the ligulate type. However, there is no
correlation between structural hybridity and colour types. Paria and Pradhan (1970) ana-lyzed the
structural heterozygosity in the species and reported that out of 185 plants of C. coronar-ium, 11.8% are
homozygous with nine bivalent formation, 51.3% have one ring of four chromo-somes, 27.5% have one
ring of six chromosomes, 4.8% have two rings of four chromosomes, and 2.7% have ring of six and four
chromosomes.
Structural hybridity is also present in the diploid species C. paludosum. The presence of multi-
valents in tetraploids C. segetum and C. morifolium may be due to partial homology of the two ge-nomes
present in these species, or to structural hybridity. Further, the high frequency of ring shaped bivalents
and other multiple associations in these species of Chrysanthemum indicated that each chromosome can
accommodate two chiasmata, which are mostly localized at distal ends. The ori-entation of these
multivalents is both adjacent and successive.
The present studies have revealed that C. carinatum, C. coronarium, C. segetum, C. paludosum,
and C. morifolium have natural populations that clearly establish the adaptive role of chromosome
rearrangements in the evolution of the diploid species of Chrysanthemum. The adaptive value of
structural heterozygosity has been reported earlier by Burnham (1956) and Rees (1961).
The chromosomal rearrangements help in maintaining the favourable linked gene combination by
suppressing the crossing-over formation in these rearranged segments, which this will lead to lo-calization of
chiasmata, and also give the advantage of constancy and flexibility of genotype. Thus, these annual species of
Chrysanthemum can very well be listed along with classical examples of Oenothera and Rheo, where
interchange heterozygosity is found to have an adaptive significance.
The alternate disjunction is related to the same size of the arms of chromosomes and distal localiza-
tion of chiasma (Cleland 1956). Relatively high pollen fertility in the interchange heterozygotes can
be attributed to the precise disjunction of chromosomes by the alternate orientation of multiple
asso-ciations at M-I as has been reported in these species by Rana and Jain (1965) and Chaudhuri et
al. (1976). The high frequency of structural hybrids in an X-ray induced population of C. carinatum
and the increase in frequency of structural the hybridity in the colchicine treated progeny of C.
coronarium indicate that the complement of the species are adapted to chromosomal
rearrangements as sug-gested by Darlington (1963).
The presently studied cultivated plants of C. carinatum show a lot of morphological variabil-ity.
Many of these plants show characters of C. coronarium and appear to be the advanced genera-tions of
interspecific hybrids between C. carinatum and C. coronarium. Previously, Paria and Pradhan (1970)
and Chaudhuri et al. (1976) produced interspecific hybrids between the two species and reported that for
the hybrid species of two annual Chrysanthemum (C. cariantum and C. coro-narium), most of the
morphological characters resemble those of one or the other parent, while the other characters were
intermediate between the two parents.
The hybrids of C. coronarium and C. carinatum resemble C. carinatum eith respect to semi-erect growth
habit, leaf margin, and seed morphology, and resemble C. coronarium in colour of disc flo-rets and nature of
bracts of involucral scales (Chaudhuri et al. 1976). Further, they made reciprocal crosses between these two
annual species of Chrysanthemum and the resulting F1 and F2 genera-tions were studied morphologically and
cytologically. Along with normal nine bivalent formation, the multivalent involving 3–10 chromosomes with
average frequency ranging from 0.47–0.13 per
9. 2014 Cytogenetical Studies in Seven Ornamental Species of Chrysanthemum (Asteraceae) 447
PMC was observed. The average pollen and seed fertility of the F1 plants were 27.5% and 2.9%,
respectively, while F2 plants have 59% pollen fertility and 39.6% average seed fertility.
Chaudhuri et al. (1976) concluded based on their study on the cytology of the hybrid between these
two species that these two species are isolated from each other by segregational hybrid steril-ity and
hybrid breakdown type of isolating mechanisms. They further, pointed out the role of inver-sions in the
chromosome differentiation of the two species.
Srivastava (1983) induced polyploidy in C. carinatum. The diploids have normal meiosis with
16.8 average chiasma frequency per cell with 95.4% pollen fertility. In tetraploids, the average
chromosomal associations is 5IV+8II with 32.0 average chiasma frequency per cell. The pollen fer-
tility was also low (48.5%).
Gupta and Gill (1985) induced autotetraploidy and hypertriploidy in C. coronarium through colchicines
treatment. Further, autotriploid was produced from the open pollinated progeny of auto-tetraploids. From the
progeny of the autotriploids, a number of primary trisomics were recovered. Structural heterozygosity
involving variable numbers of chromosomes were reported in all these polyploids and aneuploids. Further,
these polyploids were found to be unstable.
From the above discussion, it is clear that the annual cultivated species of Chrysanthemum with
distal localization of chiasmata and large size of the chromosomes are well adapted to struc-tural
changes, particularly reciprocal translocations. Thus, for the improvement of these ornamental species,
induced chromosomal aberrations and mutations should be considered rather than autopoly-ploidy.
Further, due to self-incompatibility, the interspecific hybrids among these Chrysanthemum species can
also be tried for improvement of their floriculture value.
Acknowledgements
The authors are thankful to UGC, New Delhi for financial assistance under DRS-SAP II,
ASIST programme, and to DST for a grant under the FIST programme.
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