Theor Appl Genet (1984) 67:419-426
9 Springer-Verlag 1984
Studies on the crossability relationships of some spinous Solanums S. V. R a t * and B. G. S. R a t Department of Botany, Andhra University, Waltair-530 003, India Received March 2, 1983; Accepted August 29, 1983 Communicated by K. Tsunewaki Summary. Cytogenetic studies involving six species of spinous S o l a n u m s have been made using the parameters of crossability/fertility relationships and chromosome pairing in parental and derived hybrid genomes. These studies have made it possible to integrate hybrid reproductive performance with observed cytological phenomena and draw inferences on concerned intergenomic homeologies. It has been found that species' differences, as they exist, are ascribable to chromosome repatterning, in their divergence and maintenance as distinct taxa. In the light of these studies, the grouping of these species has to be reconsidered. Key words: Spinous S o l a n u m s - Crossability relationships - Interspecific hybrids - Chromosome repatterning - S. m e l o n g e n a
Introduction Spinous S o l a n u m s , which enjoy worldwide distribution, constitute an important group of plants of considerable economic value. They have been in usage both as vegetables and more particularly as plants of medicinal value (Kirtikar and Basu 1935; Chadha 1952). Although they are reported to constitute a distinct morphological group (Clarke 1883) separated by reproductive barriers from tuberous and nontuberous, and non-spinous S o l a n u m s (Bhaduri 1951), the crossability relationships amongst them remain illdefined. Earlier attempts at interspecific hybridization yielded variable results (Swaminathan 1949; Mittal 1950; Bhaduri 1951; Magoon etal. 1962; Narasimha Rat 1968; Rajasekaran 1969) so that the evolutionary * Present address: Geneticist, C.T.R.I. Research Station, Hunsur-571 105,India
trends in their divergence as distinct taxa need to be better understood. Such studies could also have the way for their better utilization as plants with useful alkaloids in the light of reports of genetic manipulation of their alkaloids through hybridization (Solomon and Crane 1969; Zutshi 1966), which has become possible only with an understanding of intergenomic relationships of different species In the light of the above considerations, interspecific hybridization was attempted involving six widely distributed and commonly used spinous S o l a n u m s . Results of their crossability relationships are presented in this paper.
Materials and methods The six species used are S. surattense Burm. F. (= S. xanthocarpum Schrad. and Wendl), S. melongena L., S. indicum L., S. indicum var. 'multiflora' Whight (Fyson 1932), S. trilobatum L., and S. torvum Swartz. With the exception of S. melongena, all the others were derived from their natural wild habitats. The method used for interspecific crossing experiments was devised by the authors (Veerabhadra Rat and Rat 1977). Meiotic studies of pollen mother cells were done by customary technique of fixation in 3:1 isopropyl alcohol:propionic acid and squashing in 2% propionocarmine. Results Data on the attempts of interspecific hybridization are presented in Table 1. In 22 of 30 attempted cross combinations, some fruit was obtained. In five combinations there were complete maternal diploids indicating the apomictic nature of the pistillate parents. Even in these cases a large number of pollinations failed to yield hybrids. In all, ten interspecific hybrids were obtained for further studies. Many of these hybrids
T a b l e 1. R e s u l t s o f t h e a t t e m p t e d
cross pollinations of different spinous Solanum species investigated
Parental species Pistillate
Staminate
No. of pollinations made
No. of fruits obtained
Maternal diploids (%)
Hybrid obtained ( + ) or not (-)
Frequency of hybrid seed a
Nature of hybrid b V/W/L
S. surattense
S. melongena S. indicum S. indicum v a r .
10 78 102
7 60 31
1 30
+ + +
46.00 22.40 3.00
V L W
S. trilobatum S. torvum
86 26
38 4
17 100
+ -
13.10
V W
S. surattense S. indicum S. indicum v a r .
16 33 24
3 4
+ -
0.56
V
-
-
'multiflora'
S. melongena
"multiflora'
S. indicum
S. trilobatum S. torvum
62
13
3
-
S. surattense S. melongena S. indicum v a r .
63 37 58
7 11
-
+ +
12.60 0.02
V L
'multiflora'
S. indicum v a r . 'multiflora'
S. trilobatum
S. trilobatum S. torvum
24 17
7
-
+
0.02
L
S. S. S. S. S.
surattense melongena indicum trilobatum torvum
89 50 46 42 79
19 31 32 2 26
-
+
0.03
L
S. S. S. S.
surattense melongena indicum indicum v a r .
109 108 38 126
49 5 2 8
90 100 -
+ +
0.08
W
0.70
V
106
3
-
-
74 34 64 38
3
100 -
-
68
-
-
-
-
'multiflora'
S. torvum S. torvum
S. S. S. S.
surattense melongena indicum indicum v a r .
'multiflora'
S. trilobatum No. hybrids obtained No. ovules per flower x No. crosses b V=vigours; W=weak; L=lethal
T a b l e 2. C h r o m o s o m e Parental species a
X 100
associations and chiasma frequencies in parental genomes Stage and no. of PMCs analysed
Mean occurrence of
Chiasma frequency
Univalents
Mean
Range
Terminalization coefficient
Bivalents Rods
Rings
S. surattense
Diak. M-I
50 44
-
8.44 9.45
3.56 2.54
15.56 14.54
14-17 13-16
0.668 0.869
S. melongena
Diak. M-I
80 54
-
1.75 6.55
10.25 5.45
22.37 17.55
21-24 17-19
0.978 0.918
S. indicum
Diak. M-I
64 54
0.11
2.06 3.50
9.94 8.39
21.93 20.22
19-23 17-23
0.720 0.790
S. indicum v a r .
Diak. M-I
72 48
-
2.05 2.00
9.95 10.00
22.77 22.47
18-26 20-24
0.865 0.937
Diak. M-I
82 80
0.17 0.30
8.25 9.97
3.66 1.87
15.57 15.25
12-20 15-18
0.810 0.816
'multiflora'
S. trilobatum
a S. torvum w a s n o t r e p r e s e n t e d s i n c e v i a b l e h y b r i d s w e r e n o t o b t a i n e d i n v o l v i n g it
Diak.
Diak. M-I Diak. M-I Diak. M-I
0.05
0.50
91.50
95.00
Diak. M-I
Diak. M-I Diak. M-I Diak. M-I
85 65 35 60
49 41
20
32 36
45 33 82 25 21 45
Stage and no. of PMCs analysed
0.05
0.50
2.40
0.75
Pollen fertility (%)
0.11 0.33 0.05 0.18
0.48 0.41
0.72
1.43 0.83
0.44 0.54 2.08 0.92 4.71 4.08
Univalents Rings 7.86 7.81 2.28 2.92 1.33 1.55 2.06 1.58 1.72
5.02 4.34 9.02 7.41 9.10 7.30
Rods 3.13 2.72 8.08 7.88 6.95 7.88 8.48 9.95 8.61
5.98 6.43 2.76 4.16 2.80 4.12
Bivalents
99.00
99.5
45.5
42.5
56.0
3.0
20.5
50.0
%
Mean occurrence of associations
" L = laggards; B = bridge; I = inversion bridge and fragment T. C. = terminalization coefficient
surattense X melongena surattense X trilobatum trilobatum x surattense surattense x indicum var. 'multiflora' S. indicum var. 'multiflora' x S. surattense S. trilobatum x S. indicum vat. 'multiflora' S. melongena x S. indicum S. indicum • S. melongena
S. S. S. S. S. S. S. S.
Interspecific hybrid
Table 3. Cytological data on interspecific hybrids of spinous Solanums
0.10 0.01
0.12 0.31
0.81
0.13 0.18 0.19 0.28 0.14 0.13 0.31 1.66
Trivalents
20.00 20.63 13.51 14.14 11.04 11.60 13.40 13.16 13.10
17.24 16.56 21.11 19.00 19.47 19.56
0.15
0.14
0.28 0.26 0.01 -
Mean
0.26 0.45 0.13 0.16 0.09 0.15
Others
Chiasma frequency
13 23 14-23 17-24 15-23
13-20 11-22
9-15
12 21 8-15
18-22 17-24 9-17 12-21 8-17 6-21
Range
0.56 0.75 0.72 0.79
0.56 0.75
0.75
0.79 0.80
0.80 0.82 0.69 0.79 0.55 0.82
T.C.
I/B 3% I/K/B 10%
L/B 3%
L/B 26%
L/B 28%
L/B 20% L/B 22% L/B 61%
A-I
L/B 10% I/L/B 9.5%
L/B 9%
L/B 28%
L/B 38%
L/B 23% L/B 32% L/B 58%
A-II
Anaphase abnormalities
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9 Springer-Verlag 1984
Studies on the crossability relationships of some spinous Solanums S. V. R a t * and B. G. S. R a t Department of Botany, Andhra University, Waltair-530 003, India Received March 2, 1983; Accepted August 29, 1983 Communicated by K. Tsunewaki Summary. Cytogenetic studies involving six species of spinous S o l a n u m s have been made using the parameters of crossability/fertility relationships and chromosome pairing in parental and derived hybrid genomes. These studies have made it possible to integrate hybrid reproductive performance with observed cytological phenomena and draw inferences on concerned intergenomic homeologies. It has been found that species' differences, as they exist, are ascribable to chromosome repatterning, in their divergence and maintenance as distinct taxa. In the light of these studies, the grouping of these species has to be reconsidered. Key words: Spinous S o l a n u m s - Crossability relationships - Interspecific hybrids - Chromosome repatterning - S. m e l o n g e n a
Introduction Spinous S o l a n u m s , which enjoy worldwide distribution, constitute an important group of plants of considerable economic value. They have been in usage both as vegetables and more particularly as plants of medicinal value (Kirtikar and Basu 1935; Chadha 1952). Although they are reported to constitute a distinct morphological group (Clarke 1883) separated by reproductive barriers from tuberous and nontuberous, and non-spinous S o l a n u m s (Bhaduri 1951), the crossability relationships amongst them remain illdefined. Earlier attempts at interspecific hybridization yielded variable results (Swaminathan 1949; Mittal 1950; Bhaduri 1951; Magoon etal. 1962; Narasimha Rat 1968; Rajasekaran 1969) so that the evolutionary * Present address: Geneticist, C.T.R.I. Research Station, Hunsur-571 105,India
trends in their divergence as distinct taxa need to be better understood. Such studies could also have the way for their better utilization as plants with useful alkaloids in the light of reports of genetic manipulation of their alkaloids through hybridization (Solomon and Crane 1969; Zutshi 1966), which has become possible only with an understanding of intergenomic relationships of different species In the light of the above considerations, interspecific hybridization was attempted involving six widely distributed and commonly used spinous S o l a n u m s . Results of their crossability relationships are presented in this paper.
Materials and methods The six species used are S. surattense Burm. F. (= S. xanthocarpum Schrad. and Wendl), S. melongena L., S. indicum L., S. indicum var. 'multiflora' Whight (Fyson 1932), S. trilobatum L., and S. torvum Swartz. With the exception of S. melongena, all the others were derived from their natural wild habitats. The method used for interspecific crossing experiments was devised by the authors (Veerabhadra Rat and Rat 1977). Meiotic studies of pollen mother cells were done by customary technique of fixation in 3:1 isopropyl alcohol:propionic acid and squashing in 2% propionocarmine. Results Data on the attempts of interspecific hybridization are presented in Table 1. In 22 of 30 attempted cross combinations, some fruit was obtained. In five combinations there were complete maternal diploids indicating the apomictic nature of the pistillate parents. Even in these cases a large number of pollinations failed to yield hybrids. In all, ten interspecific hybrids were obtained for further studies. Many of these hybrids
T a b l e 1. R e s u l t s o f t h e a t t e m p t e d
cross pollinations of different spinous Solanum species investigated
Parental species Pistillate
Staminate
No. of pollinations made
No. of fruits obtained
Maternal diploids (%)
Hybrid obtained ( + ) or not (-)
Frequency of hybrid seed a
Nature of hybrid b V/W/L
S. surattense
S. melongena S. indicum S. indicum v a r .
10 78 102
7 60 31
1 30
+ + +
46.00 22.40 3.00
V L W
S. trilobatum S. torvum
86 26
38 4
17 100
+ -
13.10
V W
S. surattense S. indicum S. indicum v a r .
16 33 24
3 4
+ -
0.56
V
-
-
'multiflora'
S. melongena
"multiflora'
S. indicum
S. trilobatum S. torvum
62
13
3
-
S. surattense S. melongena S. indicum v a r .
63 37 58
7 11
-
+ +
12.60 0.02
V L
'multiflora'
S. indicum v a r . 'multiflora'
S. trilobatum
S. trilobatum S. torvum
24 17
7
-
+
0.02
L
S. S. S. S. S.
surattense melongena indicum trilobatum torvum
89 50 46 42 79
19 31 32 2 26
-
+
0.03
L
S. S. S. S.
surattense melongena indicum indicum v a r .
109 108 38 126
49 5 2 8
90 100 -
+ +
0.08
W
0.70
V
106
3
-
-
74 34 64 38
3
100 -
-
68
-
-
-
-
'multiflora'
S. torvum S. torvum
S. S. S. S.
surattense melongena indicum indicum v a r .
'multiflora'
S. trilobatum No. hybrids obtained No. ovules per flower x No. crosses b V=vigours; W=weak; L=lethal
T a b l e 2. C h r o m o s o m e Parental species a
X 100
associations and chiasma frequencies in parental genomes Stage and no. of PMCs analysed
Mean occurrence of
Chiasma frequency
Univalents
Mean
Range
Terminalization coefficient
Bivalents Rods
Rings
S. surattense
Diak. M-I
50 44
-
8.44 9.45
3.56 2.54
15.56 14.54
14-17 13-16
0.668 0.869
S. melongena
Diak. M-I
80 54
-
1.75 6.55
10.25 5.45
22.37 17.55
21-24 17-19
0.978 0.918
S. indicum
Diak. M-I
64 54
0.11
2.06 3.50
9.94 8.39
21.93 20.22
19-23 17-23
0.720 0.790
S. indicum v a r .
Diak. M-I
72 48
-
2.05 2.00
9.95 10.00
22.77 22.47
18-26 20-24
0.865 0.937
Diak. M-I
82 80
0.17 0.30
8.25 9.97
3.66 1.87
15.57 15.25
12-20 15-18
0.810 0.816
'multiflora'
S. trilobatum
a S. torvum w a s n o t r e p r e s e n t e d s i n c e v i a b l e h y b r i d s w e r e n o t o b t a i n e d i n v o l v i n g it
Diak.
Diak. M-I Diak. M-I Diak. M-I
0.05
0.50
91.50
95.00
Diak. M-I
Diak. M-I Diak. M-I Diak. M-I
85 65 35 60
49 41
20
32 36
45 33 82 25 21 45
Stage and no. of PMCs analysed
0.05
0.50
2.40
0.75
Pollen fertility (%)
0.11 0.33 0.05 0.18
0.48 0.41
0.72
1.43 0.83
0.44 0.54 2.08 0.92 4.71 4.08
Univalents Rings 7.86 7.81 2.28 2.92 1.33 1.55 2.06 1.58 1.72
5.02 4.34 9.02 7.41 9.10 7.30
Rods 3.13 2.72 8.08 7.88 6.95 7.88 8.48 9.95 8.61
5.98 6.43 2.76 4.16 2.80 4.12
Bivalents
99.00
99.5
45.5
42.5
56.0
3.0
20.5
50.0
%
Mean occurrence of associations
" L = laggards; B = bridge; I = inversion bridge and fragment T. C. = terminalization coefficient
surattense X melongena surattense X trilobatum trilobatum x surattense surattense x indicum var. 'multiflora' S. indicum var. 'multiflora' x S. surattense S. trilobatum x S. indicum vat. 'multiflora' S. melongena x S. indicum S. indicum • S. melongena
S. S. S. S. S. S. S. S.
Interspecific hybrid
Table 3. Cytological data on interspecific hybrids of spinous Solanums
0.10 0.01
0.12 0.31
0.81
0.13 0.18 0.19 0.28 0.14 0.13 0.31 1.66
Trivalents
20.00 20.63 13.51 14.14 11.04 11.60 13.40 13.16 13.10
17.24 16.56 21.11 19.00 19.47 19.56
0.15
0.14
0.28 0.26 0.01 -
Mean
0.26 0.45 0.13 0.16 0.09 0.15
Others
Chiasma frequency
13 23 14-23 17-24 15-23
13-20 11-22
9-15
12 21 8-15
18-22 17-24 9-17 12-21 8-17 6-21
Range
0.56 0.75 0.72 0.79
0.56 0.75
0.75
0.79 0.80
0.80 0.82 0.69 0.79 0.55 0.82
T.C.
I/B 3% I/K/B 10%
L/B 3%
L/B 26%
L/B 28%
L/B 20% L/B 22% L/B 61%
A-I
L/B 10% I/L/B 9.5%
L/B 9%
L/B 28%
L/B 38%
L/B 23% L/B 32% L/B 58%
A-II
Anaphase abnormalities
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