The means squares of 50 cotton genotypes revealed the significant differences among genotypes, treatments, genotypes×treatments interaction for the traits like relative cell injury, chlorophyll contents, canopy temperature, boll retention and seed cotton yield (Table 2). The most tolerant and sensitive genotypes were selected for crossing based on heat susceptibility index (HSI) and cluster analysis as selection criteria. Heat Susceptibility index (HSI) for fifty cotton genotypes was observed from 0.23 to 3.72. The lower value of HSI as indicator of tolerance was observed in 8 genotypes including FH-Noor (0.23), NIAB-545 (0.25), FH-Lalazar (0.49), FH-458 (0.56), NIAB-878 (0.58), FH-466 (0.64), IR-NIBGE-8 (0.67) and Weal-AG-Shahkar (0.68). Based on higher value of HSI the 5 genotypes viz., CIM-602 (2.68), Silky-3 (3.00), FH-326 (3.10), SLH-12 (3.18) and FH-442 (3.72) were found sensitive (Fig. 1). Cluster analysis demonstrated genotypic variability under control and high temperature stress. Based on highest and lowest mean values of studied traits the genotypes further classified as tolerant in one cluster and sensitive genotypes in another cluster (Fig. 2 and 3). The tolerant 8 genotypes were selected as lines (females) and 5 testers as sensitive (males) parents to study the genetics of 40F1 regarding combining ability effects, heterosis and gene action under Line × Tester mating design. The means squares values following Line × Tester design for June (control) and April-sowing (high temperature stress) depicted significant variations among genotypes, crosses, lines, testers, L×T, parents, and cross vs parent for various traits viz., relative cell injury, chlorophyll contents, canopy temperature, boll retention, number of sympodial branches, bolls per plant, hundred-seeds weight, plant height, and seed cotton yield. Boll weight remained non-significant under both treatments. Under June-sowing, L×T, parents and cross vs parents also remained non-significant for hundred seeds weight. Similarly, L×T revealed non-significance for canopy temperature under control. While, under April-sowing hundred seeds weight showed non-significant results for L×T and cross vs parents (Table 3).
Genetic components of variations (GCA and SCA variances) predicting gene action
The results of general combining ability (GCA) variance correspondent with additive variance, while specific combining ability (SCA) variance operates with dominance variance. Therefore, GCA and SCA variances were used to determine the type of gene action. This study showed the higher SCA variances along with dominance variance, conferred non-additive type gene action controlling the expression of all traits under control and high temperature stress (Table 4).
GCA and SCA effects for relative cell injury
General and specific combining ability (GCA & SCA) effects were preffered negative and significant regarding improvement for relative cell injury. Under control conditions, female parents namely FH-Lalazar (-6.79), FH-Noor (-2.22), NIAB-545 (-1.7), NIAB-878 (-1.57) and Weal-AG-Shahkar (-1.64) displayed GCA effects negative and significant. While, male parents viz., FH-326 (-3.78), SILKY-3 (-3.45) and SLH-12 (-3.2) exhibited negative and significant GCA effects. Under high temperature stress conditions, the female parents like FH-Lalazar (-7.49), NIAB-545 (-2.47) and FH-Noor (-1.66) revealed significant negative GCA effects, while among the male parents including SLH-12 (-4.32), FH-326 (-5.41), Silky-3 (-3.25) showed maximum negative GCA effects (Table 5). Under control condition the crosses viz. FH-466×CIM-602 (-15.2), FH-Lalazar×FH-442 (-8.0) showed significant and negative SCA effects for relative cell injury (Table 6). While, under high temperature the crosses viz., FH-466×CIM-602 (-17.1), NIAB-878×CIM-602 (-9.36) indicated significant and negative SCA effects for relative cell injury (Table 7).
GCA and SCA effects for chlorophyll contents
Maximum chlorophyll contents were claimed against high temperature stress following GCA and SCA significantly positive for improving this trait. Under control temperature conditions the female parents including IR-NIBGE-8 (4.02) and FH-Noor (3.98) were showing positive and significant GCA effects for chlorophyll contents. While none of the male parents were revealed significant and positive GCA & SCA effects. Under high temperature stress FH-458 (3.46) among female parents, while CIM-602 (1.30) among male parents indicated significantly positive GCA effects for chlorophyll contents (Table 5). Under control condition a cross IR-NIBGE-6×SILKY-3 (6.45), whilst the crosses namely NIAB-545×FH-442 (7.33) and NIAB-878×SLH-12 (6.25) under high temperature stress revealed positive and significant SCA effects for chlorophyll contents (Table 6 and 7).
GCA and SCA effects for canopy temperature
Canopy temperature with negative and significant GCA and SCA effects was claimed for decreasing its value to improve tolerance in cotton. Under control temperature conditions none of female parents showed negative and significant GCA effects.
Table 3 Mean square values of line × tester analysis for various traits under control and high temperature stress during 2020
Control
|
SOV
|
df
|
RCI
|
CC
|
CT
|
BR
|
SB
|
PH
|
B/P
|
BW
|
HSW
|
SCY
|
Rep.
|
2
|
0.09
|
12.5
|
3.44
|
3.5
|
2.5
|
83.1
|
4.5
|
0.05
|
0.18
|
10.6
|
Gen.
|
52
|
319.4**
|
113.4**
|
4.27**
|
254.3**
|
22.4**
|
423.4**
|
94.1**
|
0.32ns
|
1.74*
|
1240.1**
|
Cross
|
39
|
231.3**
|
75.3**
|
2.95**
|
186.7**
|
19.3**
|
313.9**
|
104.1**
|
0.29 ns
|
1.95*
|
445.7**
|
Line
|
7
|
371.7**
|
207.9**
|
5.64**
|
135.2**
|
13.7**
|
602.2**
|
77.6**
|
0.46 ns
|
4.59**
|
785.9**
|
Tester
|
4
|
739.8**
|
32.8**
|
5.89**
|
1200.9**
|
43.7**
|
205.0**
|
256.2**
|
0.98 ns
|
5.80**
|
376.3**
|
L×T
|
28
|
123.5**
|
48.3**
|
1.86n.s
|
1531.2**
|
17.2**
|
257.5**
|
89.0**
|
0.15 ns
|
0.73ns
|
370.5**
|
Parents
|
12
|
598.8**
|
135.7**
|
7.64**
|
459.3**
|
32.5**
|
607.1**
|
68.9**
|
0.47 ns
|
1.19 ns
|
3007.8**
|
Cross vs Parent
|
1
|
404.0**
|
1328.3**
|
15.03**
|
431.2**
|
19.6**
|
2486.8**
|
7.0*
|
0.003ns
|
0.01n.s
|
11010.9**
|
High temperature stress
|
SOV
|
df
|
RCI
|
CC
|
CT
|
BR
|
SB
|
PH
|
B/P
|
BW
|
HSW
|
SCY
|
Rep.
|
2
|
7.5
|
2.5
|
1.3
|
13.8
|
3.8
|
115.5
|
0.9
|
0.01
|
0.19
|
4.59
|
Gen.
|
52
|
387.0**
|
103.9**
|
6.14**
|
303.9**
|
57.3**
|
1197.6**
|
167.8**
|
0.37 ns
|
2.25**
|
3474.2**
|
Cross
|
39
|
303.1**
|
59.9**
|
5.45**
|
236.4**
|
38.0**
|
958.5**
|
167.7**
|
0.33 ns
|
2.09**
|
1760.7**
|
Line
|
7
|
323.6**
|
39.8**
|
6.69**
|
181.4**
|
24.1**
|
1699.2**
|
170.8**
|
0.48 ns
|
6.11**
|
3048.0**
|
Tester
|
4
|
1164.7**
|
34.8**
|
3.61**
|
1505.5**
|
17.3**
|
1139.4**
|
263.4**
|
1.29 ns
|
5.07**
|
431.6**
|
L×T
|
28
|
174.9**
|
68.6**
|
5.39**
|
68.8**
|
44.4**
|
747.5**
|
153.2**
|
0.15 ns
|
0.66 ns
|
1628.7**
|
Parents
|
12
|
690.9**
|
173.2**
|
7.28**
|
516.4**
|
91.8**
|
1421.5*
|
148.5**
|
0.51 ns
|
2.92*
|
6885.1**
|
Cross vs Parent
|
1
|
10.7**
|
984.9**
|
19.53**
|
389.6
|
397.2**
|
7838.0**
|
403.7**
|
0.15 ns
|
0.39 ns
|
29368.5**
|
Note: Rep= replication, Gen= genotype, L×T = line×tester, *= Significance at 5%, **= Significance at 1%, df= degree of freedom, RCI= Relative cell injury percentage, CC= Chlorophyll contents, CT= Canopy temperature, BR= Boll retention, B/P= Bolls per plant, BW= Boll weight, SB= Sympodial branches, HSW= Hundred seeds weight, PH=Plant height, SCY= Seed cotton yield.
Table 4 Estimation of genetic components of variation under control and high temperature stress
Trait
|
Control
|
High temperature stress
|
GCA Var.
|
SCA Var.
|
Additive Var.
|
Dominance Var.
|
GCA Var.
|
SCA Var.
|
Additive Var.
|
Dominance Var.
|
RCI
|
1.900
|
40.92
|
7.60
|
163.66
|
2.261
|
58.03
|
9.04
|
232.14
|
CC
|
0.477
|
9.58
|
1.90
|
38.33
|
-0.152
|
19.69
|
-0.61
|
78.77
|
CT
|
0.019
|
-0.05
|
0.076
|
-0.18
|
0.0009
|
1.402
|
0.0035
|
5.60
|
BR
|
2.33
|
18.07
|
9.32
|
72.27
|
2.955
|
22.768
|
11.823
|
91.07
|
SB
|
0.037
|
5.37
|
0.148
|
21.465
|
-0.113
|
14.323
|
-0.453
|
57.29
|
PH
|
0.996
|
80.37
|
3.986
|
321.47
|
3.722
|
244.843
|
14.888
|
979.37
|
B/P
|
0.27
|
28.55
|
1.07
|
114.19
|
0.255
|
50.275
|
1.0199
|
201.10
|
BW
|
0.003
|
0.04
|
0.010
|
0.180
|
0.003
|
0.047
|
0.0124
|
0.18
|
HSW
|
0.021
|
0.22
|
0.085
|
0.895
|
0.025
|
0.201
|
0.101
|
0.80
|
SCY
|
1.325
|
122.12
|
5.302
|
488.49
|
2.327
|
541.404
|
9.309
|
2165.61
|
Note: GCA= General combining ability, SCA= Specific combining ability, Var.= Variance, RCI = Relative Cell Injury, CC = Chlorophyll Contents, CT = Canopy Temperature, BR = Boll Retention, B/P = Bolls per Plant, BW = Boll Weight, SB = Sympodial Branches, HSW = Hundred Seeds Weight, PH = Plant Height, SCY = Seed Cotton Yield.
Whereas, male parent FH-326 (-0.67) revealed negative and significant GCA effects for canopy temperature. Under high temperature conditions only the female parents like NIAB-545 (-0.75) and Weal-AG-Shahkar(-0.63) showed GCA effects significantly negative (Table 5). Under control condition the crosses like FH-Noor×SLH-12 (-1.86) and FH-Lalazar×SILKY-3 (-1.79) showed negative, significant SCA effects for canopy temperature (Table 6). Under high temperature stress some desirable crosses viz., FH-466×FH-442 (-2.18), and FH-Lalazar×FH-326 (-2.14) revealed negative and significant SCA effects for improving canopy temperature (Table 7).
GCA and SCA effects for boll retention
Boll retention percentage could be improved through positive/significant GCA and SCA effects. Under control condition, GCA effects positive and significant found among female parents including FH-Noor (1.87), FH-458 (2.15), FH-Lalazar (4.64) and NIAB-545 (0.9). The male parents FH-326 (10.73) and SILKY-3 (5.55) showed significantly positive GCA effects under control condition. While, under high temperature stress, positive and significant GCA effects were recorded in female parents viz., FH-Noor (1.99), FH-458 (3.21) and FH-Lalazar (5.81), while the male parents including FH-326 (9.5) and SILKY-3 (6.07) revealed significantly positive GCA effects for boll retention (Table 5). Under control condition among crosses, the crosses viz., FH-Noor×FH-442 (11.6) and FH-458×CIM-602 (6.1), showed significant and positive SCA effects (Table 6). Under high temperature stress, the best crosses viz., FH-Noor×FH-442 (12.95) and FH-458×CIM-602 (6.2) revealed significantly positive SCA effects (Table 7).
GCA and SCA effects for bolls per plant
The number of bolls per plant is an important yield component, which may be improved through positive general and specific combining abilities effects. Among the females the genotypes FH-Noor (1.02), FH-Lalazar (3.09) and NIAB-878 (2.49) showed significantly positive GCA effects under control conditions as well as the male parents including FH-326 (3.65) and CIM-602 (2.98). Under high temperature stress the female genotypes namely FH-Noor (3.28), FH-Lalazar (4.95) and NIAB-545 (1.62) indicated GCA effects significantly positive. The male parents viz., FH-326 (4.47) and CIM-602 (1.55) displayed significant and positive GCA effects under high temperature
Table 5 Estimation of general combining ability (GCA) effects for various traits under control and high temperature stress
Control
|
Lines
|
RCI
|
CC
|
CT
|
BR
|
SB
|
PH
|
B/P
|
BW
|
HSW
|
SCY
|
FH-Noor
|
-2.22**
|
3.98**
|
-0.33 ns
|
1.87**
|
-0.46 ns
|
-8.84**
|
1.02*
|
0.04 ns
|
0.08 ns
|
-3.7**
|
FH-458
|
4.06**
|
0.86 ns
|
-0.15 ns
|
2.15**
|
-1.03**
|
0.45 ns
|
-2.91**
|
-0.18**
|
-0.23**
|
-0.11 ns
|
FH-466
|
9.89**
|
-1.88 ns
|
-0.1 ns
|
-3.68**
|
0.26 ns
|
-0.23 ns
|
-2.91**
|
0.03 ns
|
-0.71**
|
-8.6**
|
FH-Lalazar
|
-6.79**
|
-6.31**
|
-0.72 ns
|
4.64**
|
-1.45**
|
2.22*
|
3.09**
|
0.31**
|
0.93**
|
0.39 ns
|
Weal-Ag-Shahkar
|
-1.64**
|
1.37 ns
|
-0.27 ns
|
-4.2**
|
0.00 ns
|
12.13**
|
0.96*
|
0.08**
|
-0.71**
|
12.62**
|
NIAB-545
|
-1.7**
|
-3.93**
|
-0.12 ns
|
0.9**
|
1.12**
|
-2.84**
|
-0.77 ns
|
0.08**
|
0.27**
|
-7.34**
|
IR-NIBGE-8
|
-0.02ns
|
4.02**
|
0.37 ns
|
-1.02**
|
1.29**
|
-5.82**
|
-0.98*
|
-0.24**
|
0.00 ns
|
-1.28*
|
NIAB-878
|
-1.57**
|
1.89 ns
|
1.32**
|
-0.66**
|
0.26 ns
|
2.93**
|
2.49**
|
-0.12**
|
0.38**
|
8.01**
|
S.E
|
0.23
|
1.14
|
0.37
|
0.18
|
0.27
|
1.04
|
0.473
|
0.02
|
0.06
|
0.53
|
Testers
|
|
FH-326
|
-3.78**
|
-0.66 ns
|
-0.67*
|
9.5**
|
0.01 ns
|
2.64**
|
3.65**
|
0.31**
|
0.71**
|
6.37**
|
Silky-3
|
-3.45**
|
-0.25 ns
|
-0.09 ns
|
5.55**
|
-0.81**
|
-4.2**
|
-0.31 ns
|
0.02 ns
|
0.31**
|
-2.54**
|
SLH-12
|
-3.2**
|
1.67 ns
|
-0.21 ns
|
-3.52**
|
-1.8**
|
2.32**
|
-3.6**
|
-0.24**
|
-0.30**
|
-3.05**
|
CIM-602
|
1.18**
|
0.6 ns
|
0.58*
|
-5.31**
|
1.19**
|
1.02 ns
|
2.98**
|
-0.1**
|
-0.45**
|
1.35**
|
FH-442
|
9.25**
|
-1.36 ns
|
0.39 ns
|
-6.21**
|
1.41**
|
-1.78*
|
-2.72**
|
0.01 ns
|
-0.28**
|
-2.14**
|
S.E
|
0.184
|
0.902
|
0.289
|
0.141
|
0.21
|
0.83
|
0.374
|
0.023
|
0.050
|
0.43
|
High temperature stress
|
Lines
|
RCI
|
CC
|
CT
|
BR
|
SB
|
PH
|
B/P
|
BW
|
HSW
|
SCY
|
FH-Noor
|
-1.66**
|
1.10 ns
|
0.09 ns
|
1.99**
|
0.52 ns
|
-12.8**
|
3.28**
|
0.06*
|
-0.27**
|
-5.59**
|
FH-458
|
1.83**
|
3.46**
|
-0.31 ns
|
3.21**
|
0.06 ns
|
5.16**
|
-2.58**
|
-0.18**
|
-1.05**
|
-1.27*
|
FH-466
|
9.06**
|
-0.46 ns
|
1.16**
|
-3.62**
|
-1.54**
|
0.11 ns
|
-5.45**
|
0.03 ns
|
-0.3**
|
-18.3**
|
FH-Lalazar
|
-7.49**
|
0.13 ns
|
0.23 ns
|
5.81**
|
-0.74**
|
-6.27**
|
4.95**
|
0.34**
|
0.73**
|
-8.28**
|
Weal-Ag-Shahkar
|
0.38ns
|
-0.56 ns
|
-0.63*
|
-4.04**
|
2.59**
|
7.86**
|
0.75 ns
|
0.03 ns
|
-0.52**
|
30.62**
|
NIAB-545
|
-2.47**
|
-1.22 ns
|
-0.75**
|
0.37 ns
|
0.46 ns
|
17.6**
|
1.62**
|
0.05 ns
|
0.62**
|
6.3**
|
IR-NIBGE-8
|
0.68**
|
-1.65*
|
0.68*
|
-2.18**
|
-0.34 ns
|
-13.7**
|
-2.18**
|
-0.25**
|
0.17**
|
-3.09**
|
NIAB-878
|
-0.33ns
|
-0.81 ns
|
-0.46 ns
|
-1.53**
|
-1.01**
|
2.13*
|
-0.38 ns
|
-0.08**
|
0.61**
|
-0.46 ns
|
S.E
|
0.24
|
0.79
|
0.28
|
0.19
|
0.31
|
0.93
|
0.40
|
0.03
|
0.06
|
0.55
|
Testers
|
|
FH-326
|
-5.41**
|
-0.14 ns
|
-0.10 ns
|
10.73**
|
1.02**
|
7.28**
|
4.47**
|
0.36**
|
0.7**
|
7.01**
|
Silky-3
|
-3.25**
|
-1.46*
|
-0.03 ns
|
6.07**
|
-0.82**
|
7.78**
|
0.51 ns
|
0.02 ns
|
0.2**
|
-1.61**
|
SLH-12
|
-4.32**
|
1.13 ns
|
0.66**
|
-4.02**
|
-0.94**
|
-4.34**
|
-3.24**
|
-0.19**
|
-0.14**
|
0.83 ns
|
CIM-602
|
1.41**
|
1.30*
|
-0.18 ns
|
-5.64**
|
0.47 ns
|
-5.12**
|
1.55**
|
-0.21**
|
-0.47**
|
-2.91**
|
FH-442
|
11.56**
|
-0.82 ns
|
-0.35 ns
|
-7.14**
|
0.27 ns
|
-5.6**
|
-3.28**
|
0.02 ns
|
-0.29**
|
-3.32**
|
S.E
|
0.19
|
0.63
|
0.22
|
0.15
|
0.25
|
0.73
|
0.32
|
0.02
|
0.05
|
0.43
|
Note: RCI = Relative Cell Injury, CC = Chlorophyll Contents, CT = Canopy Temperature, BR = Boll Retention, B/P = Bolls per Plant, BW = Boll Weight, SB = Sympodial Branches, HSW = Hundred Seeds Weight, PH = Plant Height, SCY = Seed Cotton Yield.
stress (Table 5). The desirable crosses like Weal-AG-Shakar×SLH-12 (9.6) and NIAB-878×SILKY-3 (8.1) were selected based on positive and significant SCA effects under control condition (Table 6). Under high temperature stress, among desired crosses the best crosses like Weal-ag-Shakar×SLH-12 (17.7) and NIAB-878×SILKY-3 (13.4) displayed positive and significant SCA effects for improving bolls per plant (Table 7).
GCA and SCA effects for boll weight
Positive and significant GCA & SCA effects may contribute towards increasing single boll weight. Among female parents under control condition, FH-Lalazar (0.31), Weal-AG-Shahakar (0.08) and NIAB-454 (0.08) were indicating the significantly positive GCA effects, whereas among male parents FH-326 (0.31) was found significantly positive GCA for boll weight. Under high temperature stress condition female parents, FH-Lalazar (0.34) and FH-Noor (0.06), whereas male parent FH-326 (0.36) indicated positive and significant GCA effects for boll weight (Table 5).
The best crosses under control included NIAB-878×FH-326 (0.5) and FH-466×FH-442 (0.4) followed positive and significant SCA effects (Table 6). Similarly, under high temperate stress also included these NIAB-878×FH-326 (0.4) and FH-466×FH-442 (0.3) for improving single boll weight (Table 7).
GCA and SCA effects for sympodial branches per plant
Sympodial branches per plant required higher in numbers which could be improved through positive GCA and SCA effects. Under control condition, the female parents viz., NIAB-545 (1.12) and IR-NIBGE-8 (1.29), and the male parents viz., CIM-602 (1.19) and FH-442 (1.41) showed GCA effects highly positive and significant regarding sympodial branches per plant. Under high temperature stress the female parent Weal-AG-Shahkar (2.59), and the male parent FH-326 (1.02) depicted positive and significant GCA effects regarding sympodial branches per plant (Table 5). The SCA among crosses viz., FH-Lalazar×SLH-12 (4.1), and IR-NIBGE-8×SLH-12 (4.6) revealed better performance because of significantly positive effects for sympodial branches under control condition (Table 6). Similarly, under high temperature stress the crosses viz., Weal-AG-Shahakar×SLH-12 (8.0) and NIAB-878×Silky-3 (5.9) displayed significantly positive SCA effects trough which sympodial branches may be improved to bear more fruit (Table 7).
GCA and SCA effects for hundred-seeds weight
Positive and significant general combing ability effects (GCA) under control conditions indicated in female parents viz., FH-Lalazar (0.93), NIAB-545 (0.27) and NIAB-878 (0.38). Whereas, among male parents, namely FH-326 (0.71) and SILKY-3 (0.31) were found significantly positive for hundred seed weight. Under high temperature stress conditions four female parents including FH-Lalazar (0.73), NIAB-545 (0.62), IR-NIBGE-8 (0.17) and NIAB-878 (0.61) showed positive and significant GCA effects. Whereas, male parents FH-326 (0.7) and SILKY-3 (0.2) indicated positive and significant GCA effects regarding hundred seeds weight under high temperature stress (Table 5). Under control condition some good crosses like FH-Noor×FH-442 (0.9) and NIAB-878×FH-326 (0.74) were predicting significantly positive SCA effects for hundred seeds weight (Table 6). Under high temperature stress the best performing crosses included FH-Noor×SLH-12 (0.8) and FH-458×FH-442 (0.7) which indicating positive and significant SCA effects for hundred seeds weight (Table 7).
GCA and SCA effects for plant height
Plant height may be improved through positive GCA effects among the parents. The female parents namely FH-Lalazar (2.22), Weal-AG-Shahakar (12.13) and NIAB-878 (2.93), while the males FH-326 (2.64) and SLH-12 (2.32) depicted significantly positive GCA effects under control condition. Under high temperature stress, GCA effects regarding plant height were found significantly positive among females viz., FH-458 (5.16), Weal-AG-Shahkar (7.86), NIAB-545 (17.6) and NIAB-878 (2.13), while the males viz., FH-326 (7.28) and SILKY-3 (7.78) indicated GCA effects significantly positive regrading plant height (Table 5). Positive and significant SCA effects observed amongst the crosses, but the superior crosses viz., FH-Noor×FH-326 (18.8), FH-Noor×FH-442 (13.3) revealed positive and significant SCA effects under control condition (Table 6). Under high temperature stress, amongst the crosses the best performing crosses viz., Weal -AG-Shahkar×SLH-12 (32.4) and FH-NOOR×CIM-602 (30.1) described positive and significant SCA effects regarding plant height (Table 7).
GCA and SCA effects for seed cotton yield
Positive and significant general and specific combining abilities (GCA & SCA) effects are important regarding improvement in seed cotton yield. Under control condition the female parents like Weal-AG-Shahkar (12.62) and NIAB-878 (8.01), while the male parents FH-326 (6.37) and CIM-602 (1.35) indicated significant and positive GCA effects. Under high temperature stress the female parents namely Weal-AG-Shahkar (30.62) and NIAB-545 (6.34), while male parent FH-326 (7.01) revealed best positive and significant GCA effects with improved seed cotton yield (Table 5). Under control condition, SCA were observed in some promising crosses viz., Weal-AG-Shahkar×SLH-12 (21.9) and NIAB-878×SILKY-3 (18.8) which showed positive and significant SCA effects regarding seed cotton yield (Table 6).Under high temperature stress, among elite crosses viz., Weal-AG-Shahkar×SLH-12 (77.51) and NIAB-878×SILKY-3 (41.4) indicated highly positive and significant SCA effects with improved seed cotton yield than other cross combinations (Table 7).
Estimation of heterosis (Better-parent) under control and high temperature stress conditions
Heterosis (better-parent) refers F1 superiority in one or more traits. Generally positive heterosis is required but in case of and relative cell injury and canopy temperature, negative heterosis may be desired. Better-parent heterosis for relative cell injury was observed between -49.3 to 25.1% under control condition and ranged from -46.7 to 2.8% under high temperature stress. Under control condition the cross combinations viz., FH-Lalazar×FH-326 (-49.3%), NIAB-545×FH-326 (-47.0%) indicated negative and significant better-parent heterosis (Table 6). Under high temperature stress the cross combinations namely NIAB-545×FH-326 (-46.7%) and FH-Lalazar×Silky-3 (-46.3%) displayed negative and significant better-parent heterosis for relative cell injury (Table 7). For chlorophyll contents better-parent heterosis was found between -63.6 to 10.7% and -56.1 to 4.6% following control and high temperature stress, respectively. Positive and significant better-parent heterosis among crosses could not observed for chlorophyll contents under both treatments (Table 6 and 7).
For canopy temperature negative and significant heterosis was claimed to improve tolerance against high temperature stress. Better-parent heterosis was observed between -16.5 to 1.2% under control and -14.3 to 7.0% under high temperature stress conditions. The cross combinations namely FH-Lalazar×FH-326 (-16.5%) and FH-458×FH-326 (-14.0%) showed negative and significant better-parent heterosis under control condition (Table 6). While, the combinations viz., NIAB-878×SILKY-3 (-14.3%) and FH-Lalazar×FH-326 (-12.6%) exhibited negative and significant better-parent heterosis under high temperature stress condition for canopy temperature (Table 7). Boll retention indicated better-parent heterosis from -41.2 to 14.0% under control and -50.1 to 11.2% under high temperature stress conditions. Under control condition the crosses including FH-Lalazar×FH-326 (14.07%) and FH-Lalazar×SILKY-3 (8.3%) displayed highly positive and significant better-parent heterosis in favor of boll retention (Table 6). Similarly, under high temperature stress condition the cross combinations like FH-Lalazar×FH-326 (11.2%) and FH-Lalazar×SILKY-3 (7.5%) indicated positive and significant better-parent heterosis with respect to boll retention (Table 7). Better parent heterosis regarding bolls per plant was determined between -41.8 to 26.9% and -61.5 to 55.5% following control and high temperature stress conditions, respectively. Under control condition crosses like IR-NIBGE-8×FH-326 (26.9%) and NIAB-878×SILKY-3 (21.5%) revealed positive and highly significant better-parent heterosis with subject to bolls per plant (Table 6). While, highly significant and positive heterosis over better-parent was observed in crosses including FH-Lalazar×SILKY-3 (55.5%) and FH-Lalazar×FH-326 (50.0%) under high temperature stress condition in favor of bolls per plant (Table 7). Boll weight during control condition displayed better-parent heterosis between -18.6 to 14.5%, while under high temperature stress ranged from -19.3 to 12.7%. Under control condition the crosses namely NIAB-878×FH-326 (14.5%) and FH-466×FH-442 (11.1%) indicated significantly positive better-parent heterosis (Table 6). Under high temperature stress the crosses like NIAB-878×FH-326 (12.7%) and NIAB-545×FH-326 (9.9%) revealed significant and positive better-parent heterosis for boll weight (Table 7).
Hundred seed weight showed better-parent heterosis from -19.9 to 16.4% and -29.3 to 8.1% following control and high temperature stress conditions, respectively. Under control condition the crosses viz., NIAB-878×FH-326 (16.4%) and FH-458×FH-326 (11.5%) displayed positive and significant better-parent heterosis (Table 6). Whereas, crosses like NIAB-545×FH-326 (8.1%) and NIAB-878×FH-326 (7.14%) determined significantly positive better-parent heterosis under temperature stress in favor of hundred seeds weight (Table 7). For sympodial branches per plant, better-parent heterosis was recorded from -43.8 to 22.2% under control condition and ranged between -59.7 to 40.6% under high temperature stress condition. Positive and significant better-parent heterosis determined by the crosses like IR-NIBGE-8×SLH-12 (22.2%) and IR-NIBGE-8×CIM-602 (13.4%) under control condition (Table 6). Whereas, the crosses including Weal-ag-Shahkar×SLH-12 (40.6%) and FH-Noor×FH-326 (14.8%) showed significantly positive better-parent heterosis under high temperature stress regarding sympodial branches per plant (Table 7).
Table 6 Calculation of specific combining ability (SCA) and heterosis (Better-parent) in different promising crosses for each trait under control condition
Traits
|
Crosses
|
SCA
|
Crosses
|
Heterosis
(Better-parent)
|
RCI
|
FH-466×CIM-602
|
-15.2
|
FH-Lalazar×FH-326
|
-49.3
|
FH-Lalazar×FH-442
|
-8.0
|
NIAB-545×FH-326
|
-47.0
|
CC
|
IR-NIBGE-8×SILKY-3
|
6.4
|
-
|
-
|
-
|
-
|
-
|
-
|
CT
|
FH-NOOR×SLH-12
|
-1.8
|
FH-Lalazar×FH-326
|
-16.5
|
FH-Lalazar×SILKY-3
|
-1.7
|
FH-458×FH-326
|
-14.0
|
BR
|
FH-NOOR×FH-442
|
11.6
|
FH-Lalazar×FH-326
|
14.0
|
FH-458×CIM-602
|
6.1
|
FH-Lalazar×SILKY-3
|
8.3
|
B/P
|
Weal-ag-Shakar×SLH-12
|
9.6
|
IR-NIBGE-8×FH-326
|
26.9
|
NIAB-878×SILKY-3
|
8.1
|
NIAB-878×SILKY-3
|
21.5
|
BW
|
NIAB-878×FH-326
|
0.5
|
NIAB-878×FH-326
|
14.5
|
FH-466×FH442
|
0.4
|
FH-466×FH442
|
11.1
|
HSW
|
FH-NOOR×FH-442
|
0.9
|
NIAB-878×FH-326
|
16.4
|
NIAB-878×FH-326
|
0.7
|
FH-458×FH-326
|
11.5
|
SB
|
IR-NIBGE-8×SLH-12
|
4.6
|
IR-NIBGE-8×SLH-12
|
22.2
|
FH-Lalazar×SLH-12
|
4.1
|
IR-NIBGE-8×CIM-602
|
13.4
|
PH
|
FH-NOOR×FH-326
|
18.8
|
Weal-ag-Shahkar×CIM-602
|
22.9
|
FH-NOOR×FH-442
|
13.3
|
FH-Lalazar×CIM-602
|
6.1
|
SCY
|
Weal-AG-Shahkar×SLH-12
|
21.9
|
NIAB-878×SILKY-3
|
18.4
|
NIAB-878×SILKY-3
|
18.8
|
NIAB-878×FH-326
|
5.5
|
Note: RCI= Relative Cell Injury, CC= Chlorophyll Contents, CT= Canopy Temperature, BR= Boll Retention, B/P= Bolls per Plant, BW= Boll Weight, SB= Sympodial Branches per plant, HSW= Hundred Seeds Weight, PH= Plant Height, SCY= Seed Cotton Yield.
Table 7 Calculation of specific combining ability (SCA) and heterosis (Better-parent) in different promising crosses for each trait under high temperature stress condition
Traits
|
Crosses
|
SCA
|
Crosses
|
Heterosis
(Better-parent)
|
RCI
|
FH-466×CIM-602
|
-17.1
|
NIAB-545×FH-326
|
-46.7
|
NIAB-878×CIM-602
|
-9.3
|
FH-Lalazar×SILKY-3
|
-46.3
|
CC
|
NIAB-545×FH-442
|
7.3
|
-
|
-
|
NIAB-878×SLH-12
|
6.2
|
-
|
-
|
CT
|
FH-466×FH-442
|
-2.1
|
NIAB-878×SILKY-3
|
-14.3
|
FH-Lalazar×FH-326
|
-2.1
|
FH-Lalazar×FH-326
|
-12.6
|
BR
|
FH-NOOR×FH-442
|
12.9
|
FH-Lalazar×FH-326
|
11.2
|
FH-458 × CIM-602
|
6.2
|
FH-Lalazar×SILKY-3
|
7.5
|
B/P
|
Weal-Ag-Shakar×SLH-12
|
17.7
|
FH-Lalazar×SILKY-3
|
55.5
|
NIAB-878×SILKY-3
|
13.4
|
FH-Lalazar×FH-326
|
50.0
|
BW
|
NIAB-878×FH-326
|
0.4
|
NIAB-878×FH-326
|
12.7
|
FH-466×FH-442
|
0.3
|
NIAB-545×FH-326
|
9.9
|
HSW
|
FH-NOOR×SLH-12
|
0.8
|
NIAB-545×FH-326
|
8.1
|
FH-458×FH-442
|
0.7
|
NIAB-878×FH-326
|
7.1
|
SB
|
Weal-ag-Shakar×SLH-12
|
8.0
|
Weal-ag-Shahakar×SLH-12
|
40.6
|
NIAB-878×SILKY-3
|
5.9
|
FH-NOOR×FH-326
|
14.8
|
PH
|
Weal-ag-Shahkar×SLH-12
|
32.4
|
FH-458×SILKY-3
|
9.5
|
FH-NOOR×CIM-602
|
30.1
|
-
|
-
|
SCY
|
Weal-ag-Shahkar×SLH-12
|
77.5
|
NIAB-878×SILKY-3
|
31.9
|
NIAB-878×SILKY-3
|
41.4
|
NIAB-878×FH-326
|
8.4
|
Note: RCI= Relative Cell Injury, CC= Chlorophyll Contents, CT= Canopy Temperature, BR= Boll Retention, B/P= Bolls per Plant, BW= Boll Weight, SB= Sympodial Branches per plant, HSW= Hundred Seeds Weight, PH= Plant Height, SCY= Seed Cotton Yield.
Plant height under control condition revealed better-parent heterosis ranged from -39.0 to 22.9% and ranged from -46.84 to 9.55% under high temperature stress condition. Under control condition crosses like Weal-AG-Shahkar×CIM-602 (22.9%) and FH-Lalazar×CIM-602 (6.1%) revealed positive and highly significant better-parent heterosis for plant height (Table 6). Whereas, under high temperature stress condition a cross combination i.e., FH-458×SILKY-3 (9.5%) displayed positive and significant better-parent heterosis regarding plant height (Table 7). Positive and significant heterosis in F1 would be the dire need for achieving the objective of higher seed cotton yield. Therefore, better-parent heterosis in favor of seed cotton yield found between -65.6 to 18.4% under control and rang from -75.1 to 31.9% under high temperature stress conditions. Better-parent heterosis for seed cotton in crosses like NIAB-878×SILKY-3 (18.4%), NIAB-878×FH-326 (5.5%) was recorded under control condition (Table 6). While, under high temperature stress the crosses viz., NIAB-878×Silky-3 (31.9%) and NIAB-878×FH-326 (8.4%) depicted positive and significant better-parent heterosis that could be helpful regarding improvement in seed cotton yield under high temperature stress (Table 7).