Combining ability estimates and gene action for seed cotton yield, its components and fibre quality parameters in intraspecific crosses of upland cotton (Gossypium hirsutum L.)

Introduction

Cotton, often referred to as the "King of Fibre," is one of the most significant economic crops globally, serving as the primary source of natural fibre for the textile industry. Upland cotton (Gossypium hirsutum L.) accounts for approximately 95% of global cotton production. In India, cotton plays a pivotal role in the agricultural economy, contributing substantially to national income and foreign exchange earnings (Alkuddsi et al., 2013) [1] . With advancements in spinning technologies and the expanding range of cotton applications, the improvement of fibre quality has become a top priority in cotton breeding programs (Liang et al., 2013) [11] . Breeding new cultivars with both high yield and superior fibre quality is now the central objective for cotton breeder's worldwide (Ashokkumar et al., 2010) [2] . In Punjab, cotton is the third most important crop and is cultivated over an area of approximately 5.05 lakh hectares. However, all the currently recommended varieties and hybrids in the state possess only medium fibre quality. Despite decades of breeding efforts, there has been limited progress in enhancing fibre traits. Furthermore, cotton yields have stagnated over the past decade, possibly due to a narrow genetic base initially constrained by polyploidization and domestication bottlenecks and later exacerbated by the overuse of elite germplasm in breeding programs. These programs have typically captured only a small portion of the existing genetic variation (Brubaker et al., 1999) [3] . To overcome this genetic stagnation, the use of exotic germplasm has emerged as a valuable strategy. Introducing new alleles-particularly those associated with high fibre strength-from foreign genetic resources, such as accessions from the United States, holds promise for cotton improvement. Selecting the right parental lines is the cornerstone of any successful breeding program. Estimating the general combining ability (GCA) of germplasm lines for lint yield and fibre quality helps identify parents capable of contributing to simultaneous genetic improvement of these traits. The line × tester mating design (Kempthorne, 1957) [6] provides a systematic framework for identifying suitable parental combinations. This approach not only helps estimate GCA and specific combining ability (SCA) but also sheds light on the underlying genetic control of important traits, guiding the formulation of effective breeding strategies. The present study was therefore conducted to evaluate the GCA and SCA of exotic and locally available cotton genotypes for seed cotton yield, its yield components, and fibre quality traits, with the goal of identifying superior parents and cross combinations for future breeding programs.

Material and Methods

An experiment was conducted at the experimental field of the Department of Plant Breeding and Genetics, Punjab Agricultural University during Kharif 2010 and Kharif 2011. The breeding material consisted of four females viz. PIL-138, PIL-139, LH 900 and RS 875 and twenty testers including eight exotic accessions viz. EC676023, EC676021, EC676015, EC676017, EC676018, EC676022, EC676014, EC676026 and twelve indigenous lines namely PIL-138, PIL-139, PIL-137, RC-85, RC-8, PIL-8, PIL-8H, CIM240, RC 240, F-1040, IL-92, RC-79. The females were crossed with males in lines × tester mating design to develop eighty crosses during Kharif, 2010. The seeds of the parental lines and their corresponding 80 F₁ hybrids were sown during the Kharif season of 2011 using a randomized complete block design (RCBD) with three replications. Each plot consisted of a 6-meter row, with a spacing of 75 cm between rows and 60 cm between plants. Three seeds were dibbled per hill to ensure uniform germination, and later thinned to retain one healthy seedling per hill. Observations were recorded on five competitive plants per genotype in each replication for 13 traits: days to square initiation, number of monopods per plant, number of sympods per plant, number of bolls per plant, plant height (cm), days to maturity, boll weight (g), seed cotton yield per plant (g), harvest index (%), ginning outturn (%), 2.5% span length (mm), fibre strength (g/tex), and fibre fineness (µg/inch). The mean values for each trait across replications were subjected to analysis of variance (ANOVA) as per the method of Panse and Sukhatme (1964). Line × tester analysis, following the method proposed by Kempthorne (1957) [6] , was conducted to estimate General Combining Ability (GCA) effects of the parents and Specific Combining Ability (SCA) effects of the hybrids for the traits under investigation.

Results and Discussion

Analysis of variance

The 24 parental lines and 80 hybrids evaluated in this study exhibited significant variation for all the yield components and fibre quality traits analyzed (Tables 1 &2), indicating the presence of substantial genetic variability within the experimental material. Analysis of variance revealed that the mean squares for parents vs. hybrids were significant for all characters except boll weight, suggesting the presence of average heterosis in most traits (Table 1). Further, line × tester analysis (Table 2) showed highly significant mean squares for lines, testers, and line × tester interactions across all traits, confirming differential combining ability among the genotypes. Notably, the magnitude of specific combining ability (SCA) effects was greater than that of general combining ability (GCA) effects for most traits, including days to square initiation, number of monopods and sympods per plant, number of bolls per plant, plant height, boll weight, seed cotton yield, harvest index, 2.5% span length, fibre strength, and fibre fineness. This indicates a predominance of non-additive gene action in the inheritance of these traits. However, for days to maturity and ginning outturn, additive gene action was more prominent, as evidenced by higher GCA effects. These findings suggest that high performance in yield components and fibre quality traits did not always align within the same genotypes, reflecting independent genetic control of these parameters. The GCA/SCA ratios and degree of dominance further supported the predominance of non-additive gene action for most traits. These results are consistent with previous studies reporting non-additive gene effects for number of bolls, boll weight, and seed cotton yield (Ashokkumar et al., 2010) [2] , although other studies have highlighted the role of both additive and non-additive effects (Kumaresan et al., 1999) [9] . Similarly, non-additive gene action has been emphasized in the inheritance of seed cotton yield (Kumar et al., 2014), while fibre strength and micronaire have been attributed to additive gene action, and fibre length to non-additive gene action (Lukange et al., 2007) [14] . Ashokkumar et al. (2010) [2] also noted a significant role of non-additive gene effects in the inheritance of fibre quality traits, supporting the present findings. The magnitude of GCA variances were higher than SCA variance for days to maturity (Simon et al., 2013) [18] and ginning outturn (Jatoi et al., 2011) [4] indicating the importance of additive gene action for these characters. The results of this study would suggest that heterosis breeding was suitable for all the characters including fibre properties except ginning outturn and days to maturity. The nonadditive gene actions are also important for varietal adaptability.

General combining ability analysis

Combining ability analysis provides valuable insights for selecting suitable parents based on the performance of their hybrids, and plays a crucial role in heterosis breeding. In the present study, the lines PIL-138 and RS875, along with testers F-1040 and EC676015, emerged as the best general combiners, exhibiting significant GCA effects for the majority of yield-related and fibre quality traits (Table 3). Among the lines, PIL-138 consistently demonstrated strong general combining ability for key yield attributes, including number of sympods per plant, number of bolls per plant, boll weight, seed cotton yield per plant, and ginning outturn. Similarly, the tester F-1040 ranked highest for number of bolls per plant, boll weight, and number of sympods per plant, making it a strong general combiner for seed cotton yield and its component traits. Additionally, RC-85 was also identified as a superior male parent for seed cotton yield. For other traits, RS875 emerged as the best general combiner for early square initiation, reduced plant height, lower monopod number, earlier maturity, and superior 2.5% span length, making it a valuable female parent for these traits. The line PIL-139 was identified as the best general combiner for fibre strength and fibre fineness, whereas LH900 was noted for its strong GCA effects on harvest index. In terms of testers for fibre quality traits, EC676015 was identified as the best general combiner for 2.5% span length, and a good general combiner for fibre strength and fibre fineness. PIL-8 and EC676018 were identified as top general combiners for fibre fineness and fibre strength, respectively.

Other notable general combiners included:- EC676017 for number of monopods per plant and plant height  RC-8 for early square initiation  PIL-136 for harvest index and ginning outturn  EC676021 for earliness (days to maturity) Overall, PIL-138 and F-1040 stand out as valuable sources of favorable alleles for improving seed cotton yield and its contributing traits, while RS875, PIL-139, and EC676015 offer strong potential for enhancing fibre quality characteristics.

Specific combining ability analysis

Based on the SCA effects presented in Table 4, most of the hybrid combinations exhibiting high SCA values resulted from crosses between geographically diverse parents. This observation aligns with the findings of Joshi and Dhawan (1966) [5] , who reported high SCA effects in hybrids derived from genetically diverse parental lines.

Analysis of specific combining ability revealed

significant variation across the 80 hybrids evaluated. A total of:  8 hybrids exhibited significant negative SCA effects for days to square initiation,  9 hybrids for plant height,  29 hybrids for days to maturity,  5 hybrids for number of monopods per plant, and  22 hybrids for fibre fineness, suggesting potential for earliness, compact plant architecture, and finer fibre traits.

Conversely, a significant number of hybrids showed positive SCA effects, indicating favorable contributions for yield and fibre traits: When genetic variation arises from additive gene effects, selection from segregating populations is an effective strategy for identifying plants with a desirable combination of traits. In contrast, when non-additive gene action predominates, as indicated for many traits in this study, heterosis breeding becomes a more suitable approach for exploiting hybrid vigor and improving cotton yield and quality.

Conclusion

The present investigation demonstrated significant genetic variability among parents and their hybrids for yield components and fibre quality traits, highlighting the potential for genetic improvement in upland cotton. The predominance of non-additive gene action for most traitsincluding seed cotton yield, number of bolls per plant, boll weight, and fibre quality parameters-suggests that heterosis breeding can be effectively utilized to enhance productivity and fibre characteristics. Lines such as PIL-138 and RS 875, and testers like F-1040 and EC676015, emerged as superior general combiners for multiple traits and can serve as valuable parental lines in breeding programs. Several hybrids, notably RS 875 × RC-85, LH 900 × RC-240, and PIL-138 × EC676018, displayed high specific combining ability and desirable trait combinations, indicating their potential for direct exploitation or use in further selection programs. This study reinforces the usefulness of line × tester analysis for identifying promising parental combinations and understanding gene action governing key agronomic and fibre traits. The integration of elite and exotic germplasm with diverse genetic backgrounds offers a viable strategy to break the existing yield plateau and achieve simultaneous improvement in yield and fibre quality in cotton.

References

1. Alkuddsi YA, Rao MRG, Patil SS, Gowda TH, Josh M. Combining ability analysis for seed cotton yield (kapas yield) and its components in intra hirsutum hybrids and forming heterotic boxes for exploitation in cotton. Genomics and Applied Biology. 2013;4:35-49.
2. Ashokkumar K, Ravikesavan R, Prince KSJ. Combining ability estimates for yield and fibre quality traits in line × tester crosses of Upland Cotton (Gossypium hirsutum L.). International Journal of Biology. 2010;2:179-189.
3. Brubaker CL, Bourland FM, Wendel JF. The origin and domestication of cotton. In: Smith CW, Cothren JT, editors. Cotton: origin, history, technology, and production. New York: Wiley and Sons; 1999. p. 3-32.
4. Jatoi WA, Baloch MJ, Veesar NF, Panhwar SA. Combining ability estimates from line × tester analysis for yield and yield components in upland cotton genotypes. Journal of Agricultural Research. 2011;49:165-172.
5. Joshi AB, Dhawan ML. Genetic improvement in yield with special reference to self-fertilization crops. Indian Journal of Genetics and Plant Breeding. 1966;26:101113.
6. Kempthorne O. An Introduction to Genetic Statistics. New York: John Wiley and Sons, Inc; London: Chapman & Hall, Ltd; 1957. p. 191-200.
7. Kumar SK, Ashokkumar K, Ravikesavan R. Genetic effects of combining ability studies for yield and fibre quality traits in diallel crosses of upland cotton (Gossypium hirsutum L.). African Journal of Biotechnology. 2014;3:119-126.
8. Chawla R, Mondal K, Pankaj MS. Mechanisms of plant stress tolerance: Drought, salinity, and temperature extremes. Plant Science Archives. 2022;4(8). DOI: https://doi.org/10.51470/PSA.2022.7.2.04
9. Kumaresan D, Senthilkumar P, Ganesan J. Combining ability studies for quantitative traits in cotton (Gossypium hirsutum L.). Madras Agricultural Journal. 1999;18:430-432.
10. Meenakshi Sahu, Pallabi Dutta. Air Pollution and Public Health: Linking Exposure to Disease. Environmental Reports; an International Journal. 2020. DOI: https://doi.org/10.51470/ER.2020.2.1.01
11. Liang Z, Cheng HU, Hua HUA, ZhaoHu LI, JinPing HUA. Construction of a linkage map and QTL mapping for fiber quality traits in upland cotton (Gossypium hirsutum L.). Chinese Science Bulletin. 2013;58:32333243.
12. Ayana DT, Olika GI. Effect of mulching practice as soil moisture conservation for tomato (Lycopersicon esculentum Mill.) production under supplemental irrigation in Yabello district of Borana zone, Ethiopia. Acta Biology Forum. 2024;3(2):43-47.
13. Lenmem Y, Narayana Swamy G, Ramesh G, Gupta S, Mohiuddin M. Integrating Water Management, Nutrient Inputs, and Plant Density: A Holistic Review on Optimizing Cotton Yield under Variable Agroecosystems. Plant Science Review. 2020. DOI: https://doi.org/10.51470/PSR.2020.01.01.01
14. Lukange EP, Labuschagne MT, Herselman L. Combining ability for yield and fibre characteristics in Tanzanian cotton germplasm. Euphytica. 2007;161:383-389.
15. Renjan B. Enhancing Intercropping Research and Practices in Modern Agricultural Landscapes. Agriculture Archives: an International Journal. 2023.
16. Singh A, Yadav SS, Joshi E, Khambalkar PA. Sustainable groundwater management, addressing depletion through advanced technology and policy. Environmental Reports. 2022.
17. Asma J, Subrahmanyam D, Krishnaveni D. Tungro virus disease in India: historical insights and contemporary prevalence trends in rice cultivation. Agriculture Archives; 2023.
18. Simon SY, Kadams AM, Aliyu Combining ability analysis in F1 hybrids of cotton (Gossypium species L.) by diallel method in Northeastern Nigeria. Greener Journal of Agricultural Sciences. 2013;3:90-97.
19. Kempthorne O. An introduction to genetic statistics. John Wiley and Sons, 1 st Edition, New York, USA. 1957, p. 456-471.
20. Yu J, Zhang K, Li S, Yu S, Zhai H, Wu M, et al. Mapping quantitative trait loci for lint yield and fiber quality across environments in a Gossypium hirsutum × Gossypium barbadense backcross inbred line population. Theoretical and Applied Genetics. 2013;126:275-287.
21. Afreen A, Khasim SM, Bathool SU, Tehseen F. Evaluation of Anti-inflammatory activity of Jacquemontia caerulea leaf methanolic extract in Wistar rats. Journal of American Medical Science and Research; 2024.