Hybrid cotton production through exploitation of heterosis is the only way for having vertical improvement and betterment in seed cotton yield which has been stagnated in the recent years. The current study was conducted to evaluate the performance of F 2 population for studying mean performance, heterotic effects and inbreeding depression in upland cotton for polygenic traits. Parental genotypes and their F 2s were sown at Khyber Pakhtunkhwa Agricultural University, Peshawar during 2010, manually. All the traits revealed highly significant (p ≤ 0.01) variations for both parents and their F 2 hybrids. Mean performance for parents and their F 2 hybrids is: (5.26 to 7.12 & 4.43 to 6.60) seeds locule -1, (21.10 to 28.03 & 20.40 to 28.50) seed boll -1, (32.20 to 34.80 & 32.22 to 35.05) lint% and (62.87 to 85.47 & 45.94 to 92.04) seed cotton yield plant -1, respectively. Heterotic effects found over mid parent and better parent were: 66.66% & 46.66% (seeds locule -1), 60% & 30% (seed boll -1), 43.33% & 30% (lint %) and 36.66% & 16.66% (seed cotton yield plant -1), respectively. For the parameters: seeds locule -1 (11 & 10), seeds boll -1 (2 & 1) and seed cotton yield plant -1 (3 & 1) showed positive highly significant heterosis for both mid and better parent, respectively while lint% did not reveal any positive significant heterosis. F 2 populations i.e. CIM-499 × CIM-554 and CIM-554 × CIM-499 revealed highly significant heterotic effects over mid and better parent for all the traits except lint % while CIM-554 × CIM-707 showed highly significant heterotic effects for seeds locule -1 and seed cotton yield palnt -1. Positive economic heterotic effects were also exhibited by more than 50% of the F 2 population i.e., 76.66% for seed locule -1, 50% for seeds boll -1, 3.33% for lint% and 20% for seed cotton yield plant -1, respectively. By comparing F 2 mean values with F 1s, only lint % showed (0.00% to 15.55%) maximum inbreeding depression while negligible amount of inbreeding depression was observed for the remaining traits. However, negative inbreeding depression was revealed by majority of the F 2 population like 96.66% (seeds locule -1 & seeds boll -1), 60% (lint%) and 90% (seed cotton yield -1), respectively meant F 2 population has shown more stability even after segregation and have exceeded the check cultivars and better parents in performance.
Cotton (Gossypium hirsutum L.) is a major cash crop, often cross-pollinated, long day plant belonging to the family Malvacae. It is a sixth largest source of vegetable oil in the world and can boost up the economy of any country by producing edible oil for human consumption, feed (seed cake) for animals and local consumption in textile industries. Worldwide, most common cultivated species of cotton is Gossypium hirsutum L., a tetraploid, also called as upland cotton and provides 90% fiber production while Gossypium barbadense called as Egyptian cotton produces only 3% fiber. These both species are also known as new world cotton [
Heterosis (over better parent) is a best source for improvement of F1 and F2 hybrids for production. It has ability which can lead breeders for commercial utilization of valuable hybrid combinations in breeding program. It can also play a vital role for selection of potential parents with desired vigor, maternal effects and genetic variance. Hybrid cotton has successfully attracted the concentration of cotton breeders for commercial utilization of hybrid progenies [
Inbreeding depression is also related to high heterosis in F1 hybrids and has to search for moderate type of heterosis which has some stability to have less inbreeding depression at F2 level [
The F2 lines revealed larger range of adaptation regarding to their parents and F1 hybrids due to presence of genetic variation and larger heterogenity [
A successful cotton breeding program depends upon the choice and use of best parental lines for crossing and selection of favorable gene combinations. Improvements in cotton yields can be made by applying dependable tools to cotton breeders regarding to heterotic studies and inbreeding depression. For enhancement of production per unit area by proper availability of environment, identification and selection of genotypes with best genetic potential is a regular requirement. In view of economic importance of hybrid cotton cultivation and importance of selected hybrids in segregating generations, the current research was undertaken to study the genetic potential, heterotic effects and inbreeding depression for yield related traits in 6 × 6 F2 diallel populations of upland cotton.
Genetic material: Breeding material used during the study of genetic potential, heterotic effects and inbreeding depression for yield related traits in 6 × 6 F2 populations of upland cotton were consisted of six different Gossypium hirsutum L. genotypes i.e. CIM-446, CIM-496, CIM-499, CIM-506, CIM-554 and CIM-707 (having broad genetic base and varied by pedigree, date of release, seed cotton yield and fiber quality traits) and their 30 F2 cross combinations in a complete diallel fashion. Some of the characteristics of used varieties/genotypes during the study have been mentioned below.
Experimental design and field procedures: The mean performance, heterosis
and inbreeding depression in parental genotypes and their F2 populations of upland cotton for polygenic traits were conducted at Khyber Pakhtunkhwa Agricultural University, Peshawar during 2010. The hand sown method was used for parental genotypes and their F2s in a randomized complete block (RCB) design with three replications. Each treatment was consisted of two rows having four meter length with 30 cm plant to plant and 75 cm row to row distance. All the recommended cultural practices and inputs were applied for all the entries from time of sowing till the harvesting including fertilizer, hoeing, irrigation and pest control and the crop was grown in uniform conditions to reduce the environmental variability. Boll picking was done for two times on single plant basis and ginning was made with eight saw-gins.
Statistical analysis: Data for all the variables were analyzed through analysis of variance (ANOVA) [
Heterosis: The F2 heterosis over mid parents was calculated in terms of percent increase (+) or decrease (−) of F2 hybrids against its mid parent values according to the following formula [
Heterosis % = F ¯ 2 − M P ¯ M P ¯ × 100 (1)
The F2 heterobeltiosis (heterosis over better parents) was formulated in terms of percent increase/decrease of F2 hybrid over its better parent according to [
Heterobeltiosis % = F ¯ 2 − B P ¯ B P ¯ × 100 (2)
The “t” test was used to determine whether the mid and better parents F2 heterosis was significant or not. The “t” values were computed by using the following formula according to [
t = F ¯ 2 i j − M P ¯ i j / B P ¯ i j 3 8 ( E M S ) (3)
where;
F ¯ 2 i j = Mean of the ijth F ¯ cross.
M P ¯ i j = Mid parent value for the ijth cross.
B P ¯ i j = Better parent value for the ijth cross.
EMS = Error mean square.
For assessment of economic heterosis, the cultivar CIM-473 was used as check cultivar and was also grown with other cultivars but was not included in 6 × 6 diallel hybrids. The check cultivar was compared with mean values of other parental cultivars and F2 hybrids and economic heterosis was formulated.
Inbreeding depression: Inbreeding depression in F2 hybrids was calculated as percent decrease of F2 hybrids when compared with F1 hybrid means as outlined by [
InbreedingDepression % = F 2 − F 1 F 1 × 100 (4)
Regarding analysis of variance, the mean values for thirty six cotton genotypes including six parents and their 30 F2 hybrids revealed highly significant differences (p ≤ 0.01) for seeds per locule, seeds per bolls, lint % and seed cotton yield per plant, respectively (
Seeds per locule: Seeds per locule varied from 5.26 (CIM-554) to 7.12 (CIM-446) among parents and 4.43 (CIM-506 × CIM-496) to 6.60 (CIM-496 × CIM-499 & CIM-554 × CIM-707) in F2 population (
Parameters | Mean squares | CV % |
---|---|---|
Seeds locule−1 Seeds boll−1 Lint % Seed cotton yield plant−1 | 0.84** 4.99** 1.79** 352.52** | 4.12 10.82 2.81 8.83 |
**, Significant at p ≤ 0.01.
Parents and F2 Populations | Seeds locule−1 | Seeds boll−1 | Lint % | Seed cotton yield plant−1 (g) |
---|---|---|---|---|
CIM-446 | 7.12 | 28.03 | 32.27 | 62.87 |
CIM-496 | 6.04 | 25.97 | 33.70 | 85.47 |
CIM-499 | 5.46 | 22.13 | 34.07 | 75.86 |
CIM-506 | 5.49 | 22.20 | 34.80 | 84.26 |
CIM-554 | 5.26 | 21.10 | 33.12 | 55.74 |
CIM-707 | 5.54 | 24.03 | 32.20 | 73.09 |
CIM-446 × CIM-496 | 5.82 | 23.07 | 32.10 | 74.56 |
CIM-446 × CIM-499 | 5.71 | 23.43 | 32.77 | 45.94 |
CIM-446 × CIM-506 | 6.37 | 27.23 | 32.52 | 70.11 |
CIM-446 × CIM-554 | 6.19 | 25.27 | 33.05 | 72.56 |
CIM-446 × CIM-707 | 5.35 | 22.97 | 32.72 | 72.95 |
CIM-496 × CIM-446 | 6.20 | 26.53 | 35.05 | 80.99 |
CIM-496 × CIM-499 | 6.60 | 27.20 | 33.75 | 70.90 |
CIM-496 × CIM-506 | 4.89 | 20.40 | 34.08 | 61.57 |
CIM-496 × CIM-554 | 5.81 | 25.73 | 33.96 | 76.89 |
CIM-496 × CIM-707 | 6.05 | 24.20 | 32.71 | 52.97 |
CIM-499 × CIM-446 | 5.30 | 23.93 | 33.54 | 60.32 |
CIM-499 × CIM-496 | 5.37 | 24.07 | 33.54 | 59.89 |
CIM-499 × CIM-506 | 6.50 | 25.07 | 33.55 | 70.29 |
CIM-499 × CIM-554 | 6.19 | 26.07 | 34.59 | 73.79 |
CIM-499 × CIM-707 | 6.52 | 25.33 | 34.54 | 73.75 |
CIM-506 × CIM-446 | 6.53 | 25.53 | 32.22 | 61.76 |
CIM-506 × CIM-496 | 4.43 | 20.80 | 34.36 | 92.04 |
CIM-506 × CIM-499 | 5.48 | 21.77 | 33.12 | 73.13 |
CIM-506 × CIM-554 | 5.85 | 22.47 | 34.30 | 59.50 |
CIM-506 × CIM-707 | 6.52 | 28.50 | 33.85 | 75.25 |
CIM-554 × CIM-446 | 6.42 | 22.10 | 34.52 | 53.77 |
CIM-554 × CIM-496 | 5.52 | 21.67 | 34.13 | 60.91 |
CIM-554 × CIM-499 | 6.17 | 25.83 | 33.69 | 86.01 |
CIM-554 × CIM-506 | 5.65 | 24.80 | 33.59 | 74.17 |
CIM-554 × CIM-707 | 6.60 | 23.60 | 34.13 | 77.27 |
CIM-707 × CIM-446 | 6.15 | 22.23 | 33.35 | 59.89 |
CIM-707 × CIM-496 | 6.06 | 25.00 | 32.86 | 67.94 |
CIM-707 × CIM-499 | 5.98 | 25.23 | 33.44 | 77.55 |
CIM-707 × CIM-506 | 6.35 | 23.33 | 33.44 | 70.81 |
CIM-707 × CIM-554 | 6.09 | 23.53 | 33.24 | 53.55 |
LSD0.05 | 0.3985 | 4.356 | 1.210 | 7.437 |
F2 Populations | Seeds per Locules | Seeds per boll | ||||||
---|---|---|---|---|---|---|---|---|
MP (%) | BP (%) | Ec. Het (%) | Inb. Dep. (%) | MP (%) | BP (%) | Ec. Het (%) | Inb. Dep. (%) | |
CIM-446 × CIM-496 | −11.55 | −18.26 | 5.05 | −16.74 | −14.56 | −17.70 | −4.27 | −24.73 |
CIM-446 × CIM-499 | −9.22 | −19.80 | 3.07 | −20.91 | −6.58 | −16.41 | −2.78 | −24.39 |
CIM-446 × CIM-506 | 1.11 | −10.53 | 14.98 | −11.65 | 8.44 | −2.85 | 12.99 | −14.53 |
CIM-446 × CIM-554 | 0.00 | −13.06 | 11.73 | −21.74 | 2.89 | −9.85 | 4.85 | −22.60 |
CIM-446 × CIM-707 | −15.48 | −24.86 | −3.43 | −23.46 | −11.76 | −18.05 | −4.69 | −22.24 |
CIM-496 × CIM-446 | −5.78 | −12.92 | 11.91 | −16.55 | −1.74 | −5.31 | 10.08 | −23.74 |
CIM-496 × CIM-499 | 14.78** | 9.27** | 19.12 | −6.12 | 13.10 | 4.74 | 12.86 | −5.91 |
CIM-496 × CIM-506 | −15.10 | −19.04 | −11.73 | −33.11 | −15.28 | −21.45 | −15.35 | −36.78 |
CIM-496 × CIM-554 | 2.83 | −3.81 | 4.87 | −21.38 | 9.33 | −0.92 | 6.76 | −12.30 |
CIM-496 × CIM-707 | 4.49 | 0.17 | 9.21 | −9.57 | −3.20 | −6.82 | 0.41 | −18.93 |
CIM-499 × CIM-446 | −15.74 | −25.56 | −4.33 | −34.65 | −4.59 | −14.63 | −0.71 | −5.71 |
CIM-499 × CIM-496 | −6.61 | −11.09 | −3.07 | −15.57 | 0.08 | −7.32 | −0.12 | −25.66 |
CIM-499 × CIM-506 | 18.82** | 18.40** | 17.33 | −14.59 | 13.13 | 12.93 | 4.02 | −15.73 |
CIM-499 × CIM-554 | 15.49** | 13.37** | 11.73 | −9.90 | 20.63** | 17.80* | 8.17 | −11.90 |
CIM-499 × CIM-707 | 18.55** | 17.69** | 17.69 | −9.70 | 9.75 | 5.41 | 5.10 | −15.93 |
CIM-506 × CIM-446 | 3.65 | −8.29 | 17.87 | −11.76 | 1.67 | −8.92 | 5.93 | −20.49 |
CIM-506 × CIM-496 | −23.09 | −26.66 | −20.04 | −41.86 | −13.62 | −19.91 | −13.69 | −35.54 |
CIM-506 × CIM-499 | 0.18 | −0.18 | −1.08 | −23.78 | −1.75 | −1.93 | −9.67 | −21.72 |
CIM-506 × CIM-554 | 8.93** | 6.56* | 5.60 | −26.97 | 3.79 | 1.22 | −6.76 | −37.15 |
CIM-506 × CIM-707 | 18.33** | 17.69** | 17.69 | −12.13 | 23.32** | 18.60** | 18.26 | 2.41 |
CIM-554 × CIM-446 | 3.72 | −9.83 | 15.88 | −15.86 | −10.01 | −21. 16 | −8.30 | −32.77 |
CIM-554 × CIM-496 | −2.30 | −8.61 | −0.36 | −10.39 | −7.90 | −16.56. | −10.08 | −15.84 |
CIM-554 × CIM-499 | 5.11** | 13.00** | 11.37 | 0.00 | 19.52* | 16.72* | 7.18 | −10.87 |
CIM-554 × CIM-506 | 5.21 | 2.91 | 1.99 | −6.15 | 14.55 | 11.71 | 2.90 | −13.53 |
CIM-554 × CIM-707 | 22.22** | 19.13** | 19.13 | −6.78 | 4.60 | −1.79 | −2.07 | −19.04 |
CIM-707 × CIM-446 | −2.84 | −13.62 | 11.01 | −10.61 | −14.60 | −20.69 | −7.76 | −34.11 |
CIM-707 × CIM-496 | 4.66 | 0.33 | 9.39 | −23.77 | 0.00 | −3.74 | 3.73 | −22.84 |
CIM-707 × CIM-499 | 8.73** | 7.94** | 7.94 | −18.75 | 9.32 | 4.99 | 4.69 | −21.28 |
CIM-707 × CIM-506 | 15.24** | 14.62** | 14.62 | −3.64 | 0.95 | −2.91 | −3.20 | −21.95 |
CIM-707 × CIM-554 | 12.78** | 9.93** | 9.93 | −13.49 | 4.29 | −2.08 | −2.37 | −21.01 |
Check: CIM-473 = 5.54 Check: CIM-473 = 24.10. *: Significant.
to enhance the seed cotton yield at end. Highest negative inbreeding depression was noted in CIM-506 × CIM-496 while lowest negative inbreeding depression was observed in CIM-707 × CIM-506 having values −41.86% and −3.64%, respectively (
Seeds per boll: Seeds per boll varied from 21.10 (CIM-554) to 28.03 (CIM-446) among parental cultivars and 20.40 (CIM-496 × CIM-506) to 28.50 (CIM-506 × CIM-707) among F2 population (
Lint% (GOT): The lint % (GOT) varied from 32.20 (CIM-707) to 34.80 (CIM-506) among parents and 32.10 (CIM-446 × CIM-496) to 35.05 (CIM-496 × CIM-446) among F2 population (
Seed cotton yield per plant: Seed cotton yield varied from 55.74 (CIM-554) to 85.47 (CIM-496) among parental cultivars and 45.94 (CIM-446 × CIM-499) to 92.04 (CIM-506 × CIM-496) among F2 population (
F2 Populations | Lint % (GOT) | Seed cotton yield per plant (%) | ||||||
---|---|---|---|---|---|---|---|---|
MP (%) | BP (%) | Ec. Het (%) | Inb. Dep. (%) | MP (%) | BP (%) | Ec. Het (%) | Inb. Dep. (%) | |
CIM-446 × CIM-496 | −2.66 | −4.75 | −7.79 | −7.52 | 0.53 | −12.76 | −2.82 | −54.86 |
CIM-446 × CIM-499 | −1.20 | −3.81 | −5.86 | −1.97 | −33.77 | −39.44 | −40.12 | −45.66 |
CIM-446 × CIM-506 | −3.01 | −6.56 | −6.57 | 15.55 | −4.70 | −16.79 | −8.62 | −49.95 |
CIM-446 × CIM-554 | 1.10 | −0.21 | −5.06 | −4.73 | 22.35** | 15.41* | −5.42 | −58.98 |
CIM-446 × CIM-707 | 1.52 | 1.39 | −6.00 | 0.43 | 7.31 | −0.23 | −4.91 | −50.18 |
CIM-496 × CIM-446 | 6.27 | 4.04 | 0.68 | 8.54 | 9.2 | −5.24 | 5.57 | −52.91 |
CIM-496 × CIM-499 | −0.38 | −0.94 | −3.04 | −2.68 | −12.11 | −17.05 | −7.59 | 7.04 |
CIM-496 × CIM-506 | −0.50 | −2.07 | −2.10 | 3.15 | −27.45 | −27.96 | −19.75 | −27.92 |
CIM-496 × CIM-554 | 1.65 | 0.77 | −2.44 | −10.13 | 8.90 | −10.04 | 0.22 | −31.85 |
CIM-496 × CIM-707 | −0.73 | −2.94 | −6.03 | −7.89 | −33.19 | −38.03 | −30.96 | −31.87 |
CIM-499 × CIM-446 | 1.12 | −1.56 | −3.65 | −4.01 | −13.04 | −20.49 | −21.38 | −19.74 |
CIM-499 × CIM-496 | −1.00 | −1.56 | −3.65 | −10.13 | −25.75 | −29.93 | −21.94 | −49.33 |
CIM-499 × CIM-506 | −2.55 | −1.52 | −3.61 | −4.77 | −12.20 | −16.58 | −8.38 | −23.56 |
CIM-499 × CIM-554 | −2.97 | 1.53 | −0.60 | 3.19 | 12.14* | −2.73 | −3.82 | −27.43 |
CIM-499 × CIM-707 | −4.25 | −0.74 | −0.83 | −1.90 | −0.97 | −2.78 | −3.87 | 37.36 |
CIM-506 × CIM-446 | −3.90 | −7.41 | −7.44 | 4.01 | −16.05 | −26.70 | −19.50 | −65.40 |
CIM-506 × CIM-496 | 0.32 | −1.26 | −1.29 | −4.95 | 8.46 | 7.69 | 19.97 | −11.82 |
CIM-506 × CIM-499 | −3.80 | −4.83 | −4.85 | −5.34 | −8.66 | −13.21 | −4.68 | −40.00 |
CIM-506 × CIM-554 | 1.00 | −1.44 | −1.47 | 3.06 | −15.00 | −29.39 | −22.45 | −68.83 |
CIM-506 × CIM-707 | 1.04 | −2.73 | −2.76 | 9.76 | −4.35 | −10.69 | −1.92 | −0.48 |
CIM-554 × CIM-446 | 5.59 | 4.23 | −0.83 | 3.11 | −9.33 | −14.47 | −29.91 | −68.89 |
CIM-554 × CIM-496 | −2.15 | 1.27 | −1.95 | 1.70 | −13.73 | −28.74 | −20.61 | −32.30 |
CIM-554 × CIM-499 | 0.29 | −1.12 | −3.22 | −10.87 | 30.71** | 13.38** | 12.11 | −23.99 |
CIM-554 × CIM-506 | −1.08 | −3.47 | −3.50 | −2.47 | 5.96 | −11.97 | −3.32 | −50.97 |
CIM-554 × CIM-707 | 4.50 | 3.05 | −1.95 | −12.07 | 19.96** | 5.72 | 0.72 | −40.58 |
CIM-707 × CIM-446 | −3.47 | 3.35 | −4.19 | −2.66 | −11.90 | −18.06 | −21.94 | −50.65 |
CIM-707 × CIM-496 | −0.27 | −2.49 | −5.60 | 3.69 | −14.30 | −20.51 | −11.44 | −54.44 |
CIM-707 × CIM-499 | 0.93 | −1.85 | −3.94 | −2.11 | 4.13 | 2.23 | 1.08 | −1.71 |
CIM-707 × CIM-506 | −0.17 | −3.91 | −3.94 | −4.59 | −10.00 | −15.96 | −7.70 | 1.97 |
CIM-707 × CIM-554 | 1.77 | 0.36 | −4.51 | 0.00 | −16.87 | −26.73 | −30.20 | −58.89 |
Check: CIM-473 = 34.81 Check: CIM-473 = 76.72. *: Significant.
CIM-554) to 19.97% (CIM-506 × CIM-496). In case of inbreeding depression, all F2 populations showed negative inbreeding depression except three F2 hybrids. Overall, 36.66%, 16.66% and 20% heterosis was noted for mid parent, better parent and for economic heterosis (
The F2 hybrids manifested a remarkable percentage and ranges of mid parent, better parent and economic heterosis having negligible effects of inbreeding depression for majority of the characters of upland cotton. The remarkable heterotic performance for mid parent and better parent was revealed by the F2 population including, CIM-554 × CIM-707, CIM-499 × CIM-506, CIM-499 × CIM-707, CIM-506 × CIM-707, CIM-499 × CIM-554, CIM-554 × CIM-499, CIM-496 × CIM-446 and CIM-446 × CIM-554, respectively while CIM-496 × CIM-499, CIM-506 × CIM-707, CIM-496 × CIM-446, CIM-506 × CIM-496 and CIM-554 × CIM-499 were the F2 hybrids which showed the highest positive economic heterosis. Collectively, CIM-499 × CIM-554, CIM-554 × CIM-499, CIM-554 × CIM-707 and CIM-506 × CIM-707 showed superiorly with significant heterosis for yield and yield contributing traits for all parameters except lint%. Majority of the F2 population did not reveal inbreeding depression meant having superiority over F1s even after segregation which is more desirable for selection of best hybrid cotton. Overall, these parental cultivars and F2 hybrids can be used and studied for further betterment in advanced generations for improvement of seed cotton as they have the capabilities to produce excess yield and production of cotton in future breeding program.
Khan, B.A., Khan, N.U., Ahmed, M., Iqbal, M., Ullah, I., Saleem, M., Khurshid, I. and Kanwal, A. (2017) Heterosis and Inbreeding Depression in F2 Populations of Upland Cotton (Gossypium hirsutum L.). Agricultural Sciences, 8, 1283-1295. https://doi.org/10.4236/as.2017.811093