Variance analysis of F1, F2 hybrids, and their inbred parents at various cotton belt
The varianceFi analysis was performed for 15 F1, F2 hybrids, and their eight inbred parents. The variance was extremely significant (P < 0.01) for majority of traits in at various cotton belt (Table 2 and 3). All agronomic, yield and fiber quality traits except FU and FE showed significant differences in F1 generation among the combinations in Anyang (Table 2). Similarly, the differences among the combinations of F2 generation reached significant or extremely significant for all traits except FE and FS which indicated that the differences in these traits were mainly caused by genetic variation. The female inbred lines had non-significant variance for most of agronomic traits in both F1 and F2 generations. In contrast, female inbred lines demonstrated significant variance for majority of yield and fiber quality traits in both generations. The female variance was extremely significant and improved for in F2 generation for SCY, LY, BN, BW, LP and FL. Furthermore, female inbred lines exhibited significant difference for PH, SFBL, FE, and FS only in F2 as compared to F1 generation. The male inbred lines had significant variance in eight traits in F1 generation, while the difference was significant only in seven traits in F2 generation. The female × male interaction variance was significant for majority of traits in both generations except HFFB, FE and MIC. Table 3 summarized the analysis of variance results for all traits in Alar. All combinations in F1 displayed extremely significant differences in agronomic and yield traits whereas FL and FS related fiber quality traits had significant differences. Similarly, F2 only showed significant difference in agronomic and yield traits. The variance was significant among female parents for most of traits in F1 generation specifically in LFFB, SFBL, SCY, LY, BN, LP, FL, FS, and MIC. The variance for male inbred had significant difference in 80% agronomic and some yield traits. For example, LP had highly significant difference in F1 generation. In contrast, PH, HFFB, SFBL, and FE had highly significant differences in F2. Interestingly, the female × male interaction variance was extremely significant for PH, HFFB, LFFB, FBN, and BW.
Table 2
Analysis of variance and heritability analysis of each trait in Anyang
Trait | Generation | Block | Combination | F | M | M×F | Error | H2(%) | h2(%) |
PH | F1 | 2.55 | 9.54** | 1.24 | 3.95* | 5.09** | 2.95 | 75.66 | 42.49 |
| F2 | 0.81 | 5.80** | 4.09* | 5.67** | 2.09 | 3.79 | 65.23 | 52.61 |
HFFB | F1 | 7.93** | 4.15** | 1.65 | 11.56** | 1.01 | 1.09 | 55.20 | 55.04 |
| F2 | 8.90** | 6.77** | 7.10 | 16.73** | 1.06 | 0.63 | 69.82 | 69.18 |
LFFB | F1 | 1.77 | 17.65** | 1.15 | 0.95 | 17.54** | 1.05 | 85.04 | 2.57 |
| F2 | 1.12 | 9.27** | 1.49 | 1.89 | 6.99** | 0.80 | 74.50 | 23.55 |
SFBL | F1 | 1.30 | 17.73** | 1.80 | 0.87 | 16.45** | 1.90 | 85.77 | 12.46 |
| F2 | 4.00* | 12.74** | 5.55* | 1.26 | 7.39** | 0.67 | 82.10 | 43.97 |
FBN | F1 | 2.57 | 10.80** | 3.25 | 4.87* | 4.45** | 0.08 | 78.86 | 54.53 |
| F2 | 2.84 | 17.05** | 0.81 | 4.30* | 8.90** | 0.06 | 85.49 | 47.30 |
SCY | F1 | 2.89 | 10.84** | 5.68* | 4.14* | 4.23** | 0.04 | 79.46 | 57.38 |
| F2 | 0.79 | 8.79** | 10.79** | 1.53 | 3.45** | 0.04 | 76.56 | 57.45 |
LY | F1 | 1.38 | 15.99** | 18.99** | 8.88** | 2.75* | 0.01 | 86.27 | 78.27 |
| F2 | 1.86 | 14.98** | 16.60** | 1.88 | 4.31** | 0.01 | 85.72 | 69.97 |
BN | F1 | 0.81 | 4.84** | 0.91 | 5.00* | 2.27* | 0.64 | 58.92 | 41.48 |
| F2 | 1.40 | 3.37** | 8.71** | 2.23 | 1.37 | 0.42 | 50.43 | 44.27 |
BW | F1 | 1.82 | 17.91** | 9.73** | 1.08 | 7.90** | 0.03 | 87.44 | 58.57 |
| F2 | 0.31 | 10.06** | 20.39** | 3.13 | 2.30** | 0.07 | 79.78 | 71.04 |
LP | F1 | 3.79* | 27.26** | 21.06** | 1.94 | 6.59** | 0.30 | 91.92 | 76.85 |
| F2 | 2.42 | 16.44** | 38.86** | 4.41* | 2.23* | 0.40 | 87.30 | 82.10 |
FL | F1 | 2.52 | 15.70** | 19.00** | 7.9** | 2.83* | 0.24 | 86.08 | 77.57 |
| F2 | 1.12 | 6.43** | 27.29** | 13.44** | 0.77 | 0.50 | 70.80 | 70.80 |
FU | F1 | 1.54 | 1.46 | 7.13* | 1.91 | 0.68 | 0.65 | 25.81 | 25.81 |
| F2 | 3.10 | 2.70* | 1.30 | 1.26 | 2.42* | 0.69 | 37.17 | 7.44 |
FE | F1 | 0.48 | 1.16 | 1.22 | 3.22 | 0.69 | 0.00 | 15.33 | 15.33 |
| F2 | 0.74 | 4.84** | 6.00* | 5.62* | 1.60 | 0.00 | 60.78 | 52.98 |
FS | F1 | 3.67* | 20.44** | 0.98 | 0.51 | 23.87** | 0.27 | 88.40 | 0.00 |
| F2 | 0.29 | 6.64** | 6.09* | 2.75 | 2.98* | 0.60 | 69.23 | 48.91 |
MIC | F1 | 1.93 | 10.17** | 33.57** | 13.43** | 1.10 | 0.04 | 79.83 | 79.13 |
| F2 | 1.89 | 2.16* | 4.68* | 4.00* | 0.91 | 0.07 | 34.43 | 34.43 |
*and ** denote significant differences at 0.05 and 0.01 levels, respectively. F (female), M (male). |
Table 3
Analysis of variance and heritability analysis of each trait in Alar
Trait | Generation | Block | Combination | F | M | M×F | Error | H2(%) | h2(%) |
PH | F1 | 3.93* | 64.24** | 0.12 | 6.76** | 25.49** | 4.25 | 96.08 | 64.03 |
F2 | 1.31 | 13.53** | 3.87 | 4.55* | 5.58** | 9.35 | 82.75 | 56.43 |
HFFB | F1 | 1.74 | 4.57** | 0.31 | 1.68 | 4.17** | 1.70 | 57.84 | 13.33 |
F2 | 0.09 | 32.00** | 0.10 | 3.84* | 19.01** | 0.35 | 92.31 | 46.13 |
LFFB | F1 | 0.28 | 12.06** | 4.35* | 7.06** | 3.76** | 1.07 | 80.09 | 63.70 |
F2 | 0.31 | 14.10** | 4.05 | 2.04 | 8.14** | 0.72 | 83.25 | 43.43 |
SFBL | F1 | 0.34 | 30.88** | 8.23** | 8.31** | 7.49** | 0.69 | 92.23 | 75.40 |
F2 | 5.31** | 6.15** | 6.63* | 4.89* | 2.11 | 2.34 | 67.45 | 55.42 |
FBN | F1 | 4.67* | 5.09** | 2.51 | 2.30 | 3.21** | 0.32 | 60.33 | 31.16 |
F2 | 4.12* | 5.73** | 0.10 | 2.51 | 4.40** | 0.30 | 65.17 | 25.69 |
SCY | F1 | 0.05 | 5.76** | 5.09* | 2.82 | 2.74* | 0.15 | 65.27 | 45.14 |
F2 | 0.23 | 4.78** | 5.48* | 2.16 | 2.43 | 0.09 | 60.18 | 41.27 |
LY | F1 | 1.69 | 6.43** | 7.74** | 1.56 | 3.03** | 0.03 | 68.99 | 48.02 |
F2 | 0.13 | 4.34** | 10.44** | 2.47 | 1.57 | 0.03 | 58.87 | 51.09 |
BN | F1 | 0.43 | 4.09** | 5.48* | 5.88* | 1.35 | 0.76 | 55.55 | 50.39 |
| F2 | 0.20 | 1.26 | 2.24 | 0.41 | 1.25 | 0.74 | 15.67 | 8.68 |
BW | F1 | 2.95 | 9.13** | 1.73 | 2.02 | 6.54** | 0.07 | 74.39 | 27.14 |
| F2 | 3.34* | 9.74** | 0.93 | 2.15 | 7.39** | 0.04 | 75.44 | 23.12 |
LP | F1 | 1.49 | 6.99** | 26.24** | 8.50** | 1.04 | 1.00 | 72.35 | 72.02 |
F2 | 0.49 | 3.59** | 7.83** | 2.45 | 1.50 | 1.41 | 52.27 | 44.25 |
FL | F1 | 1.25 | 2.28* | 5.67* | 3.15 | 1.00 | 1.37 | 35.46 | 35.46 |
F2 | 3.40 | 1.27 | 6.88* | 1.77 | 0.62 | 1.45 | 22.79 | 22.79 |
FU | F1 | 2.19 | 0.75 | 0.22 | 0.09 | 1.19 | 0.85 | 6.06 | 0.00 |
F2 | 0.12 | 1.37 | 0.87 | 2.04 | 1.07 | 1.10 | 12.86 | 10.79 |
FE | F1 | 2.03 | 1.02 | 1.00 | 2.29 | 0.75 | 0.00 | 9.66 | 9.66 |
F2 | 0.38 | 1.12 | 1.22 | 4.52* | 0.55 | 0.00 | 18.28 | 18.28 |
FS | F1 | 0.05 | 2.22* | 7.63** | 5.70* | 0.68 | 2.04 | 39.46 | 39.46 |
F2 | 0.12 | 1.30 | 5.65* | 2.77 | 0.60 | 1.74 | 23.22 | 23.22 |
MIC | F1 | 0.93 | 1.06 | 6.63* | 6.41** | 0.32 | 0.10 | 23.60 | 23.60 |
F2 | 0.90 | 0.84 | 3.92 | 2.15 | 0.48 | 0.08 | 13.36 | 13.36 |
*and**denote significant differences at 0.05 and 0.01 levels, respectively.F (female), M (male). |
Heritability analysis of F1, F2 hybrids, and their eight inbred parents at various cotton belt
Heritability estimates the ratio of genetic variance to phenotypic variance. The broad-sense heritability (H2) and narrow-sense heritability (h2) were determined for all traits. Heritability analysis for Anyang is detailed in Table 2. According to the results, the percentage of H2 was strong for majority of traits in both hybrid generations. In particular, LFFB, SFBL, FBN, SCY, LY, BW, LP, FL, and FS stated H2 greater than 70% in both hybrid generations. Conversely, BN and FU had low percentage of H2 relative to others traits in both hybrid generations. Further results determined that h2 was strong and above 50% HFFB, SCY, LY, BW, LP, and FL in both F1 and F2 hybrids. LFFB and FU had very low h2 in both generations than all other traits. Heritability analysis for Alar detected that H2 for PH, LFFB, SFBL, and BW were great than 65% in both F1 and F2.The heritability of fiber traits in Alar were relatively more lower than Anyang. Specifically, FU and FE had low h2. Interestingly, the h2 of some traits in F2 generation were higher than that in F1 generation. For instance, SCY, BN, BW, LP in Anyang and LY in Alar had higher h2. These findings put forth a clue that it is significant to select these traits in F2 generation. The traits with lower heritability can easily affected by the environment. Hence, these traits can be improved through longer screening cycles during breeding measures.
General combining ability analysis of inbred parents at various cotton belt
General combining ability analysis is useful to screen superior inbred parents for specific or a set of traits. Based on results of combining ability analysis, GCA of the parental line was different and altered with generation, trait, and environment (Table 4). In Anyang, parental lines P1, P4, and P7 had higher GCA for SCY and LY in both hybrid generations. Furthermore, these parental lines comparatively had better GCA manifestation for others traits in F1 and F2. In particular, P1 showed higher GCA for HFFB, LFFB, SFBL, SCY, LY, BN, and MIC. P4 had greater GCA for SCY, LY, BW, LP and FU. P7 showed superior GCA for SCY, LY, BN, BW, LP, FU, and MIC. Apart from these inbred lines, P6 had better GCA for SCY, BW, FL, PH, HFFB. P2 and P8 exhibited positive GCA in more than five agronomic characteristic and fiber quality traits. It was observed that GCA was quite undulating in Alar. The parental lines P2, P4, and P7 were detected with higher GCA for SCY and LY in both F1 and F2. P2 GCA was specifically well in many traits such as PH, LFFB, SFBL, FBN, SCY, LY, BN, FL, FU, FE, and FS. P4 showed better GCA for SFBL, FBN, SCY, LY, BW, LP, and FL. GCA of P7 were strong for SCY, LY, BN, LP, and MIC. In addition, P8 showed better GCA in six traits and had greater value for LFFB and SFBL. Overall, the GCA of P4 was improved for LFFB, FBN, LY, BW, LP, and MIC in F2 than F1 in both cotton belt. However, GCA of P6 was improved for PH and HFFB in F2 in both cotton belts. The P7 showed higher GCA in F2 for SCY, LY, and BN in Anyang while P5 had improved GCA in F2 for LFFB and SFBL at Alar cotton belt. These results revealed importance of these inbreed lines to improve specific trait or set of traits in different cotton belts.
Table 4
General combining ability of parents in Anyang and Alar
Environment | Parent | Generation | PH | HFFB | LFFB | SFBL | FBN | SCY | LY | BN | BW | LP | FL | FU | FE | FS | MIC |
Anyang | P1 | F1 | 1.73 | 9.41 | 8.55 | 6.43 | -1.21 | 2.68 | 2.49 | 1.68 | 1.01 | -0.20 | -3.58 | -0.23 | -0.46 | -1.35 | 3.71 |
| | F2 | -0.68 | 4.67 | 1.45 | 4.8 | -5.91 | 1.78 | 1.40 | 4.21 | -2.37 | -0.43 | -3.89 | -0.79 | -0.75 | -3.65 | 1.86 |
| P2 | F1 | 0.37 | -3.02 | 6.96 | 6.46 | 1.53 | 4.74 | 5.50 | 6.06 | -1.16 | 0.87 | -0.42 | 0.13 | 0.20 | -1.60 | 3.71 |
| | F2 | 0.90 | -3.21 | 4.58 | 0.01 | 2.28 | -3.48 | -3.43 | -0.01 | -3.35 | 0.16 | -0.64 | 0.53 | 0.07 | 0.83 | 1.86 |
| P3 | F1 | 1.95 | -2.25 | -5.96 | -7.32 | 4.65 | 2.52 | 3.72 | 3.24 | -0.67 | 1.30 | 3.45 | -0.22 | 0.36 | 1.69 | -7.55 |
| | F2 | 2.63 | 0.09 | -2.21 | -3.36 | 3.27 | -2.36 | -0.74 | -2.53 | 0.22 | 1.79 | 2.40 | -0.32 | 0.07 | 2.60 | -5.37 |
| P4 | F1 | -3.35 | -2.89 | -4.62 | -0.23 | -1.39 | 1.26 | 2.13 | -2.36 | 3.78 | 0.86 | -0.03 | 0.57 | -0.13 | 2.47 | -0.04 |
| | F2 | -2.53 | -6.85 | 2.56 | -1.01 | 2.11 | 6.80 | 8.13 | 1.15 | 5.31 | 1.12 | 0.41 | 0.53 | 0.23 | -0.65 | 0.21 |
| P5 | F1 | -0.71 | -1.25 | -4.92 | -5.33 | -3.58 | -11.20 | -13.84 | -8.63 | -2.95 | -2.84 | 0.58 | -0.26 | 0.03 | -1.21 | 0.17 |
| | F2 | -0.32 | 5.30 | -6.38 | -0.44 | -1.75 | -2.74 | -5.35 | -2.82 | 0.18 | -2.64 | 1.71 | 0.06 | 0.39 | 0.87 | 1.45 |
| P6 | F1 | 0.65 | 1.15 | -4.42 | 2.68 | -1.33 | 2.61 | -0.41 | -1.83 | 4.51 | -2.88 | 2.25 | -0.10 | 0.16 | -0.21 | -4.09 |
| | F2 | 1.42 | 2.71 | -2.03 | -1.18 | -1.33 | 2.47 | -0.02 | -2.57 | 5.25 | -2.28 | 1.45 | 0.14 | 0.30 | 1.24 | -0.83 |
| P7 | F1 | -1.07 | 0.61 | 1.92 | -8.10 | -0.97 | 4.02 | 9.09 | 1.93 | 2.18 | 4.93 | -3.43 | 0.58 | -0.13 | -1.97 | 6.43 |
| | F2 | -0.45 | -0.20 | -1.39 | -4.14 | 1.23 | 7.39 | 12.03 | 5.11 | 2.22 | 4.52 | -3.14 | 0.36 | -0.39 | -3.10 | 2.89 |
| P8 | F1 | 0.42 | -1.76 | 2.50 | 5.41 | 2.31 | -6.63 | -8.68 | -0.10 | -6.69 | -2.06 | 1.18 | -0.48 | -0.03 | 2.17 | -2.34 |
| | F2 | -0.98 | -2.50 | 3.42 | 5.32 | 0.10 | -9.86 | -12.01 | -2.54 | -7.47 | -2.24 | 1.69 | -0.50 | 0.10 | 1.86 | -2.07 |
Alar | P1 | F1 | -12.90 | 3.41 | 16.69 | 1.95 | -7.58 | -4.84 | -2.17 | -10.15 | 3.41 | 2.39 | -2.50 | -0.03 | -0.20 | -4.06 | 5.33 |
| | F2 | -9.15 | 2.85 | 0.74 | -1.47 | -8.62 | -1.00 | 0.36 | 2.19 | 0.33 | 1.33 | -1.45 | 0.56 | 0.03 | -0.83 | 0.76 |
| P2 | F1 | 13.32 | -1.98 | 15.19 | 23.89 | 4.53 | 8.33 | 6.38 | 10.67 | -2.33 | -3.30 | 1.63 | 0.07 | 0.29 | 2.36 | -1.39 |
| | F2 | 4.29 | -0.16 | 6.44 | 10.91 | 3.28 | 5.48 | 5.13 | 2.14 | 2.82 | -0.39 | 1.71 | 0.58 | 0.20 | 3.07 | 1.42 |
| P3 | F1 | 0.99 | -0.41 | -24.71 | -25.07 | -3.49 | -0.70 | 0.39 | 2.88 | -6.48 | 1.42 | -2.17 | -0.1 | -0.36 | -1.43 | -2.51 |
| | F2 | 2.45 | 2.30 | -19.32 | -24.17 | 3.68 | -4.12 | -3.84 | -1.38 | -1.84 | 0.25 | 0.68 | -0.87 | 0.03 | -1.43 | -1.47 |
| P4 | F1 | -8.08 | -6.24 | -4.69 | 9.25 | 2.84 | 2.06 | 1.69 | 2.78 | 2.13 | 0.59 | 0.51 | -0.11 | -0.03 | -0.52 | -0.49 |
| | F2 | -3.14 | -11.38 | 5.94 | 13.99 | 6.16 | 1.68 | 3.15 | -2.51 | 4.05 | 1.57 | 0.46 | -0.27 | 0.36 | -1.35 | 1.87 |
| P5 | F1 | 6.66 | 5.22 | -2.48 | -10.02 | 3.70 | -4.86 | -6.29 | -6.18 | 3.27 | -1.10 | 2.53 | 0.17 | 0.29 | 3.64 | -0.94 |
| | F2 | 5.56 | 6.39 | 6.20 | 0.74 | -4.50 | -2.04 | -4.8 | -0.44 | -5.35 | -2.76 | -1.41 | 0.01 | -0.62 | 0.54 | -2.58 |
| P6 | F1 | -0.13 | -1.71 | -6.07 | -5.83 | -4.62 | -3.71 | -4.68 | -6.56 | 3.35 | -1.21 | 1.45 | 0.07 | 0.13 | 1.01 | -0.09 |
| | F2 | 5.01 | 1.38 | 1.93 | -0.44 | -0.16 | -0.59 | 0.08 | 0.14 | 0.67 | 0.73 | -0.01 | 0.32 | -0.13 | -1.66 | 0.89 |
| P7 | F1 | -1.02 | 1.04 | -5.82 | -10.53 | 3.82 | 6.60 | 9.34 | 5.67 | -0.62 | 3.47 | -2.70 | -0.16 | -0.16 | -3.11 | 2.47 |
| | F2 | -2.12 | -1.67 | -12.91 | -13.31 | -0.90 | 4.85 | 6.82 | 3.73 | 1.50 | 1.95 | -2.11 | -0.29 | -0.03 | -0.68 | 1.42 |
| P8 | F1 | 1.16 | 0.68 | 11.89 | 16.36 | 0.80 | -2.89 | -4.66 | 0.89 | -2.72 | -2.26 | 1.25 | 0.09 | 0.03 | 2.10 | -2.38 |
| | F2 | -2.89 | 0.29 | 10.98 | 13.75 | 1.06 | -4.25 | -6.90 | -3.87 | -2.16 | -2.68 | 2.12 | -0.03 | 0.16 | 2.35 | -2.31 |
Special combining ability analysis of F1 and F2 hybrids at various cotton belt
The SCA reveals performance of a cross and provide an opportunity for utilization of heterosis in breeding. Our analysis revealed all combinations SCA was altered with traits and environments (Table 5). In Anyang, some combinations including 9, 10, and 12 had higher SCA for SCY and LY in both F1 and F2 hybrids. Specially, combination 9 had shown higher SCA for LFFB, SCY, LY, BN, BW, FE, and MIC. Combination 10 had good SCA for SCY, LY, BW, LP, FL, and FS. Wherein, combination 12 had better performances with higher SCA for LFFB, SFBL, SCY, LY, BN, BW, FL, and FS. Furthermore, it was observed that combinations 1, 8, 13, and 15 had shown relatively higher SCA more than five traits in both generations. The SCA analysis results at Alar are shown in Table 6. Among all combinations, the 2, 8, and 11 were detected with better SCA in both F1 and F2. In particular, combination 2 had shown higher SCA for nine traits including SCY, LY, BW, LP, FL, FU, FE, FS, and MIC. Interestingly, this combination SCA was improved in F2 for PH, HFFB, FL, FU, FE, and FS. It was observed that Combination 8 showed better performance as well as high SCA for SCY, LY, BW, LP, FU, and FE. The combination 11 exhibited higher SCA in eight traits including PH, LFFB, FBN, SCY, LY, BW, FE, and MIC. Beside these, combinations 3, 6, 9, 14, 15, had higher SCA for most of traits in F2 as compared to F1. These combinations most probably can be selected in F2 breeding generation to improve these traits at Alar cotton zone. Overall, analysis results revealed that combinations 9 and 2 had improved performance in F2 at both cotton belts which emphasize selection of these combination in earlier generations would be effective for future breeding program.
Table 5
Hybrid combination F1, F2 Special Combining Ability in Anyang
Combination | Generation | PH | HFFB | LFFB | SFBL | FBN | SCY | LY | BN | BW | LP | FL | FU | FE | FS | MIC |
1 | F1 | 1.79 | 0.18 | -7.24 | -3.62 | -1.23 | -7.71 | -5.71 | -5.32 | -2.35 | 1.96 | -1.39 | -0.37 | 0.16 | -0.43 | 1.79 |
| F2 | -1.83 | -1.89 | -0.89 | -1.35 | 0.86 | 4.44 | 5.90 | 2.73 | 1.31 | 1.61 | 0.68 | 0.83 | 0.36 | -0.82 | 3.10 |
2 | F1 | -1.37 | -1.91 | 2.93 | 7.92 | 0.81 | 0.85 | 1.17 | -1.78 | 2.29 | 0.37 | -0.35 | -0.38 | 0.00 | -3.26 | 1.79 |
| F2 | 0.46 | 1.14 | 1.68 | -2.72 | -0.31 | -1.18 | -0.77 | -0.87 | -0.48 | 0.21 | 0.03 | -0.17 | 0.03 | -0.96 | 3.10 |
3 | F1 | -0.42 | 1.74 | 4.31 | -4.30 | 0.41 | 5.12 | 5.32 | 1.01 | 3.84 | 0.25 | 1.05 | 0.05 | -0.16 | -1.14 | -1.96 |
| F2 | 1.37 | 0.74 | -0.78 | 4.07 | -0.55 | -3.40 | -3.96 | -0.55 | -3.00 | -0.74 | 0.14 | -0.23 | 0.03 | 2.25 | -1.45 |
4 | F1 | -0.29 | 2.15 | 3.94 | -0.89 | -1.52 | -3.03 | -3.60 | -1.77 | -1.00 | -0.51 | 1.08 | 0.27 | 0.33 | -0.43 | -0.08 |
| F2 | 0.02 | -0.09 | -2.29 | -3.21 | -2.52 | 0.81 | 0.61 | -0.73 | 2.14 | 0.10 | -0.91 | -0.25 | -0.13 | 1.58 | -2.07 |
5 | F1 | -1.24 | -0.78 | 2.22 | 3.03 | 2.04 | 4.77 | 2.83 | 7.85 | -2.78 | -2.07 | -0.39 | 0.44 | -0.33 | 5.26 | -1.54 |
| F2 | -0.95 | 0.49 | 7.85 | 2.29 | -0.78 | -0.68 | -1.79 | -0.58 | 0.03 | -1.18 | 0.07 | -0.17 | -0.30 | -2.06 | -2.69 |
6 | F1 | 1.53 | -1.37 | -6.16 | -2.14 | -0.52 | 0.64 | 2.79 | 3.47 | -3.00 | 1.83 | 0.52 | 0.39 | 0.16 | -0.47 | 0.04 |
| F2 | 0.93 | -0.40 | -5.55 | 0.92 | 3.31 | -3.54 | -2.73 | -0.19 | -3.02 | 0.86 | 0.29 | 0.64 | 0.07 | 0.88 | -0.62 |
7 | F1 | 0.81 | 0.29 | 7.12 | 8.35 | 0.00 | -2.5 | -4.23 | 1.61 | -4.08 | -1.81 | -0.16 | 0.23 | 0.00 | -4.15 | -2.46 |
| F2 | -0.21 | -1.82 | -1.33 | 0.00 | 2.09 | -3.92 | -4.09 | -1.21 | -2.47 | 0.09 | -0.90 | 0.42 | -0.26 | -1.07 | -1.86 |
8 | F1 | 1.26 | 1.50 | -7.56 | -20.89 | 0.76 | -1.82 | -2.01 | -2.28 | 0.13 | -0.26 | 1.13 | -0.20 | -0.16 | 4.33 | 1.29 |
| F2 | -0.53 | 0.94 | 0.51 | 6.23 | 1.04 | -1.89 | -2.71 | -3.24 | 1.53 | -0.81 | 1.26 | -0.69 | -0.26 | -2.09 | 1.03 |
9 | F1 | -2.07 | -1.79 | 0.44 | 12.54 | -0.76 | 2.40 | 2.24 | 0.36 | 1.79 | -0.31 | -2.27 | -0.57 | 0.33 | -0.16 | 1.92 |
| F2 | 0.74 | 0.88 | 0.82 | -6.24 | -3.12 | 8.87 | 9.22 | 4.96 | 3.18 | -0.28 | -0.76 | 0.26 | 0.07 | -1.81 | 1.65 |
10 | F1 | -2.26 | -4.29 | -8.99 | -11.46 | 1.36 | 1.28 | 1.22 | -3.16 | 5.16 | 0.54 | 0.77 | 0.15 | -0.33 | 0.45 | -0.79 |
| F2 | 1.19 | 2.95 | -1.78 | 0.85 | -0.62 | 0.48 | 0.31 | -0.31 | 0.78 | 0.14 | 0.11 | -0.64 | 0.39 | 4.09 | -0.21 |
11 | F1 | 0.13 | 3.44 | -5.18 | 7.87 | -4.47 | 7.07 | 2.93 | 1.84 | 5.36 | -3.78 | 0.87 | -0.03 | -0.13 | 0.91 | -1.84 |
| F2 | 0.19 | -0.01 | -1.51 | -4.12 | 3.64 | -0.90 | -3.17 | -2.54 | 1.71 | -2.47 | -0.97 | -1.47 | -0.43 | -0.06 | -2.48 |
12 | F1 | 2.13 | 0.85 | 14.18 | 3.59 | 3.12 | 1.64 | 3.07 | 0.17 | 1.79 | 1.44 | 0.51 | 0.16 | -0.30 | 7.41 | 0.67 |
| F2 | -1.38 | -2.94 | 3.29 | 3.26 | -3.02 | 5.10 | 4.86 | 2.07 | 2.95 | -0.30 | 0.87 | -0.25 | 0.23 | 2.03 | -1.24 |
13 | F1 | -0.06 | 1.68 | 5.17 | 7.62 | 1.39 | -3.30 | -3.30 | 1.27 | -3.97 | 0.01 | -2.18 | 0.16 | 0.03 | -3.20 | 0.67 |
| F2 | 0.82 | 0.84 | 6.30 | 3.71 | 0.20 | 5.29 | 6.67 | 3.79 | 1.47 | 1.55 | -1.40 | 0.92 | 0.23 | -0.16 | 0.41 |
14 | F1 | 1.23 | -2.25 | 7.60 | 2.07 | 0.86 | 0.63 | 1.36 | 1.41 | -0.79 | 0.81 | 1.19 | 0.30 | 0.03 | 0.59 | -1.84 |
| F2 | 0.84 | -2.57 | -8.52 | -1.69 | -3.59 | -9.68 | -9.83 | -4.23 | -5.32 | 0.18 | 1.67 | -0.01 | 0.07 | 0.23 | 0.41 |
15 | F1 | -1.17 | 0.57 | -12.77 | -9.70 | -2.25 | -6.04 | -4.05 | -4.69 | -2.38 | 1.52 | -0.39 | -0.58 | 0.36 | -5.71 | 2.34 |
| F2 | -1.66 | 1.73 | 2.23 | -2.01 | 3.39 | 0.20 | 1.48 | 0.90 | -0.81 | 1.03 | -0.17 | 0.81 | -0.10 | -2.04 | 2.89 |
Table 6
Hybrid combination F1, F2 Special Combining Ability in Alar
Combination | Generation | PH | HFFB | LFFB | SFBL | FBN | SCY | LY | BN | BW | LP | FL | FU | FE | FS | MIC |
1 | F1 | -1.51 | 4.72 | 19.99 | 15.79 | -8.91 | -3.06 | -3.63 | 3.95 | -2.67 | -0.29 | 2.06 | 0.46 | 0.20 | 1.04 | -1.03 |
| F2 | -2.45 | -5.79 | -12.34 | 2.04 | -6.97 | -5.03 | -5.81 | 2.53 | -1.58 | -0.65 | -0.10 | -0.22 | -0.03 | -1.64 | -0.89 |
2 | F1 | -4.73 | -4.42 | -11.35 | -3.32 | 3.04 | 2.96 | 2.93 | -4.18 | 5.92 | 1.59 | 1.09 | 0.40 | 0.20 | 0.85 | 0.99 |
| F2 | 1.35 | -1.69 | 17.96 | 11.00 | -6.17 | 7.78 | 8.33 | 5.31 | 0.80 | 0.47 | 2.36 | 0.54 | 0.30 | 2.81 | 0.44 |
3 | F1 | 12.55 | 2.84 | 2.17 | -9.70 | 1.35 | -4.76 | -6.06 | -3.23 | -3.89 | -1.79 | -0.87 | -0.49 | -0.13 | 0.27 | -1.26 |
| F2 | 6.29 | 3.73 | 7.81 | 10.07 | 5.92 | 0.52 | -1.05 | 4.54 | 1.46 | -1.52 | -0.35 | -0.72 | -0.03 | 0.40 | 2.00 |
4 | F1 | -4.03 | 1.93 | -3.71 | -4.50 | 5.02 | 2.56 | 3.39 | 4.38 | 0.00 | -0.07 | -0.07 | 0.11 | 0.03 | 0.67 | -1.93 |
| F2 | -1.58 | -2.75 | -16.18 | -14.48 | 3.46 | -3.33 | -0.96 | -6.90 | -3.07 | 2.39 | 1.08 | 0.29 | 0.13 | 0.44 | -0.67 |
5 | F1 | -2.28 | -5.07 | -7.11 | 1.72 | -0.50 | 2.31 | 3.38 | -0.92 | 0.65 | 0.55 | -2.21 | -0.49 | -0.29 | -2.83 | 3.23 |
| F2 | -3.60 | 6.50 | 2.76 | -8.63 | 3.76 | 0.06 | -0.52 | -5.48 | 2.38 | -0.68 | -3.00 | 0.10 | -0.36 | -2.01 | -0.89 |
6 | F1 | -3.08 | -10.07 | -5.85 | -13.64 | 3.46 | -0.24 | 0.67 | 0.51 | -5.78 | 0.10 | -1.17 | -0.01 | -0.49 | -0.32 | -0.22 |
| F2 | 1.13 | -0.40 | 3.78 | 0.75 | 0.55 | 1.87 | 4.29 | 3.38 | -5.56 | 2.19 | -0.32 | -0.51 | -0.13 | 1.94 | -1.42 |
7 | F1 | 0.31 | 4.84 | 2.06 | 1.60 | -0.09 | -7.83 | -7.72 | -5.19 | -1.59 | 0.40 | -0.09 | -0.54 | 0.00 | -0.07 | 1.12 |
| F2 | 3.96 | 5.54 | -4.74 | 0.15 | -0.85 | -3.76 | -4.34 | -2.72 | -1.17 | -0.58 | -0.50 | 0.49 | -0.30 | -1.40 | -1.42 |
8 | F1 | -6.05 | 2.99 | -3.40 | -2.59 | -6.55 | 9.04 | 11.20 | 7.13 | 2.40 | 0.04 | -1.61 | 1.00 | 0.16 | -1.53 | -0.45 |
| F2 | -7.23 | -4.77 | 2.60 | 1.09 | -5.64 | 0.44 | 2.15 | -4.64 | 3.41 | 1.79 | 0.20 | 0.80 | 0.36 | -0.47 | 2.14 |
9 | F1 | 2.21 | -0.04 | 3.91 | 13.45 | -1.60 | -0.01 | -1.49 | -1.89 | 2.61 | 0.25 | -0.70 | -0.75 | -0.16 | -2.11 | 0.90 |
| F2 | -1.94 | 3.73 | 6.55 | 2.16 | 3.17 | 2.72 | 0.17 | 2.60 | 2.24 | -2.56 | -0.24 | -0.70 | 0.03 | 0.46 | -0.53 |
10 | F1 | 6.61 | 2.28 | 3.29 | 1.18 | 4.79 | -0.96 | -2.66 | -0.56 | 2.36 | -0.79 | 3.57 | 0.30 | 0.49 | 4.02 | -1.34 |
| F2 | 4.08 | -4.10 | -8.18 | -4.15 | 2.77 | -1.27 | -2.27 | 1.39 | 1.07 | -0.84 | 0.86 | -0.08 | 0.03 | -0.54 | 1.25 |
11 | F1 | 4.60 | 5.36 | -14.13 | -2.15 | 5.46 | 3.30 | 2.97 | -4.46 | 8.46 | 0.18 | -0.89 | -0.46 | 0.29 | -0.72 | 1.26 |
| F2 | 1.32 | 6.19 | 8.56 | -2.80 | 6.42 | 3.16 | 1.52 | -5.91 | 7.13 | -1.53 | 0.41 | 0.73 | 0.16 | -0.30 | 2.31 |
12 | F1 | 4.41 | -0.42 | 9.29 | 1.71 | -2.95 | 4.87 | 4.79 | 9.37 | -4.33 | -2.00 | -1.00 | 0.14 | -0.20 | -0.79 | -2.11 |
| F2 | -5.31 | -3.85 | -13.22 | -11.15 | 7.02 | -4.02 | -4.00 | -2.58 | 0.37 | 0.11 | -1.86 | -1.03 | 0.00 | -1.42 | 0.98 |
13 | F1 | -6.50 | -5.83 | 1.23 | 12.29 | 5.20 | -4.28 | -5.14 | -3.90 | 1.49 | 1.76 | 2.47 | -0.51 | -0.03 | 1.26 | 1.70 |
| F2 | 0.94 | 1.03 | -10.4 | -11.16 | -0.29 | -0.97 | -1.10 | 0.10 | -4.88 | -0.27 | 0.15 | -0.09 | -0.33 | 0.07 | -4.14 |
14 | F1 | 1.82 | -1.89 | -0.20 | -8.95 | -3.42 | -2.55 | -1.89 | -2.49 | -2.61 | -0.18 | 0.77 | 0.64 | 0.13 | 1.44 | 1.03 |
| F2 | 3.53 | -0.98 | 9.63 | 12.32 | -6.62 | 0.61 | 0.79 | 4.30 | 0.83 | 0.17 | -0.84 | 0.41 | -0.16 | -0.90 | 1.20 |
15 | F1 | -4.33 | 2.78 | 3.81 | -2.90 | -4.29 | -1.35 | -0.72 | 1.48 | -3.01 | 0.24 | -1.36 | 0.19 | -0.20 | -1.19 | -1.88 |
| F2 | -0.48 | -2.40 | 5.42 | 12.78 | -6.53 | 1.21 | 2.79 | 4.10 | -3.45 | 1.52 | 2.14 | -0.02 | 0.33 | 2.55 | -0.36 |
The screening of hybrids with excellent heterosis in multiple traits
In this study, we further analyzed the level of MPH, BPH, CH, and HD for different traits, hybrid combinations, and cotton belt. The analysis results revealed that level of heterosis altered with trait, hybrid combination, generation, and environment (Additional file 1). The majority of combination in Anyang had shown highest heterosis for yield traits as compared to agronomic and fiber quality traits. For instance in F1 generation, the combination 12 exhibited highest MPH (45.9%) for LY. Combination 6 was top BPH producing among all combinations. It had 36.3% higher LY than better parent. Moreover, highest CH was 28.4% which had shown by combination 7 for BN. Most combinations HD was positive for yield traits but negative for agronomic and fiber quality traits. It may be because of negative MPH, BPH, and CH in agronomic and fiber quality traits. Among F2 generation, LY had highest MPH (24.0%), BPH (20.9%), and CH (11.6%). This strong vigor was witnessed in combination 5, 1, and 9, respectively. Intriguingly, combination 9 had outstanding MPH, BPH, and CH in multiple traits as compared to other combinations. The analyzed results in Alar stated that F1 had highest CH for LY (36.5%). This was exhibited by combination 8. However, combination 2 had highest MPH (21.9%) and BPH (19.7%) for SCY among others. Beside this, a positive HD was measured for most yield traits among all hybrid combinations. While agronomic and fiber quality traits had negative HD in most hybrid combinations. The results revealed hybrid combinations had shown positive MPH, BPH, and CH for yield traits in F2 generation. Interestingly, combination 2 and 9 had shown outstanding heterosis in multiple traits at Alar cotton belt. Overall analysis determined that combination 9 had best hybrid vigor in both generation and cotton belt. Therefore, it can be considered an outstanding hybrid for both cotton zones.
Subsequently, this study further screened top eight hybrid combinations with superior performance in multiple traits. The results revealed CH, MPH and BPH in selected hybrids were altered with generation and cotton belts (Fig. 1, Additional file 2). It was determined that more than 6 combinations had better CH, MPH, and BPH in both generations and cotton belts. However, some of combinations had superior CH, MPH and BPH in both generations but one cotton belt. In this regard, combination 12 had similar performance in Anyang while combination 2 and combination 9 in Alar. Beside this, some combinations exhibited strong vigor in both cotton belts but only in one generation. Such as combination 2 and combination 7 had shown better CH, MPH and BPH in F1. Combination 9 displayed better CH, MPH and BPH in F2. Combination 2 was observed with strong CH and MPH in F2. Comparatively, combination 2 and 9 showed excellent performance in multiple traits for both generations and cotton belts. These encouraging results evaluate the potential of F2 hybrids to improve cotton productivity in China.
Correlations among various traits in two different cotton belts
Relationship between traits is dynamic factor in selection of plant breeding materials. The correlation analysis between agronomic, yield and fiber quality traits in Anyang is summarized in Fig. 2A. A significant positive correlation was observed among yield (SCY, LY) and yield components (BN, BW, LP). All fiber quality traits except FU showed negative correlation with yield traits. A significant positive correlation among FU and yield was detected. The correlation between yield and agronomic traits were either non-significant negative or positive. Similar results were observed among most of fiber quality and agronomic traits. Most of fiber quality traits including FL, FE, and FS had positive correlation with each other. However, MIC had strong negative correlated with FL and FS but positive correlation with FU. The correlations were undulating among agronomic traits. For instance, PH had significant negative correlation with LFFB and MIC, had significant positive with FBN and FS. A significant positive correlation was observed between SFBL and LFFB.
The correlation analysis in Alar revealed SCY had significant positive correlation with LY and BN whereas LY was positively correlated with BN and BW (Fig. 2B). The correlation of BW was significant positive only for FE and MIC. LP showed significant negative correlation with FL and FS. In contrast, it had significant positive correlation with MIC. Among fiber quality traits, FL had a significant positive correlation with FE and FS. MIC had significant negative relationship with FL and FS. The agronomic traits had shown diverse correlations but few were significant. For instance, PH had extremely positive correlation with HFFB, FBN and FL. It had negatively correlated with LP and MIC. Moreover, SFBL was positively correlated with FS. FBN was positively correlated with FL and FE. Overall, analysis results propose that agronomic, yield, and fiber quality traits can be improved independently in both cotton belts.