Generation mean analysis based estimation of heritability and genetic advance for yield, fibre quality and oil content in cotton (Gossypium hirsutum L.)

Introduction

Cotton (Gossypium hirsutum L.) is the leading natural fibre crop of global importance, contributing significantly to the textile industry, rural livelihoods, and the agricultural economy. Improving seed cotton yield and fibre quality has long been a major objective of cotton breeding programmes. However, yield and most of its component traits are complex and polygenic in nature, governed by both additive and non-additive gene effects as well as environmental influences. Consequently, phenotypic superiority alone may not accurately reflect the true genetic potential of a genotype, thereby necessitating a thorough understanding of genetic parameters for effective crop improvement. Among various genetic parameters, heritability and genetic advance play a pivotal role in formulating breeding strategies. Heritability provides an estimate of the proportion of total phenotypic variance attributable to genetic factors, while genetic advance indicates the expected genetic improvement under selection pressure. The simultaneous consideration of both parameters offers a better prediction of the response to selection than either alone. High heritability coupled with high genetic advance generally indicates the predominance of additive gene action, suggesting that simple phenotypic selection can be highly effective. Conversely, high heritability associated with low genetic advance often reflects the role of non-additive gene effects and environmental interaction, where hybridization or recurrent selection strategies may be more beneficial (Johnson et al. 1955; Robinson et al. 1949) [9, 21] . Although numerous studies have reported genetic variability for individual traits in cotton, cross-specific and trait-wise estimates across multiple generations provide more precise insights into the nature of gene action and the scope of improvement. Considering the importance of genetic parameters in breeding decisions, the present investigation was undertaken to estimate narrow-sense heritability (h²ns) and expected genetic advance as a percentage of mean (GA%) for yield, its component traits, and fibre quality parameters across four diverse cotton crosses. The ultimate aim was to identify traits amenable to improvement through direct selection and to develop effective breeding strategies for enhancing yield potential and fibre quality in cotton.

Materials and Methods

The present investigation was carried out at the Regional Cotton Research Station, Navsari Agricultural University, Bharuch, Gujarat, India, during kharif 2023 for hybridization and kharif 2024 for field evaluation. The experimental material comprised five generations, namely P₁, P₂, F₁, F₂, and F₃, derived from four diverse cotton crosses viz., GBHV 276 × GBHV 278, GBHV 276 × GN Cot 32, G. Cot 16 BG II × GBHV 281, and BC-68-2 BG II × GBHV 217. Hybridization was undertaken using Doak's (1934) hand emasculation and pollination technique to ensure genetic purity. Field evaluation was conducted using a Randomized Complete Block Design (RCBD) with three replications, and each plot consisted of two rows, each 6.0 m in length, with a spacing of 120 cm between rows and 45 cm between plants. Recommended agronomic and plant protection practices were strictly followed throughout the crop season to maintain uniform crop growth. Observations were recorded on ten randomly selected plants from each of the P₁, P₂, and F₁ generations, while forty plants were sampled from each of the F₂ and F₃ generations.

Data were collected for phenological traits such as days to 50% flowering; plant architecture traits including plant height, number of monopodial branches, and number of sympodial branches; yield components such as number of bolls per plant, boll weight, seed cotton yield per plant, lint yield per plant, seed index, lint index, and ginning out-turn; fibre quality traits including fibre length, fibre strength, and fibre fineness; and the economic trait oil content. Fibre quality traits were measured using a High-Volume Instrument (HVI), while oil content was estimated using Soxhlet extraction.

Statistical Analysis

The narrow sense heritability was calculated by using the formula suggested by Warner (1952) [23] as follows:

Where, h 2 ns = Heritability in narrow sense VF 2 = Variance of F 2 generation D = Additive genotypic variance

Estimation of Expected Genetic Advance under Selection

The expected genetic advance at 5% selection intensity was estimated by using formula suggested by Allard (1960) [4] .

Expected genetic advance = h 2 (ns) × K ×σp h 2 (ns) = Heritability in narrow sense σp = Phenotypic standard Deviation K = Selection differential (K = 2.06 at 5% selection pressure)

Expected genetic advance as per cent of mean was estimated by the following formula: Genetic advance Expected genetic advance as% of mean = ×100 X Where, X = Mean of the character under study

Results and Discussion

The present investigation assessed the magnitude of narrowsense heritability (h²ns) and genetic advance as a percentage of mean (GA%) across four cotton crosses for 13 phenological, plant architecture, yield, fibre quality, and economic traits. The simultaneous interpretation of heritability and GA% values provide meaningful insights into the underlying gene action and environmental influence governing each trait. Generally, high heritability coupled with high GA% indicates the predominance of additive gene action, suggesting that simple phenotypic selection would be effective for genetic improvement, whereas high heritability with low GA% points to non-additive gene action or environmental influence, warranting alternative breeding strategies such as heterosis breeding or recurrent selection. The estimates of h²ns and GA% for all traits in the four cotton crosses are presented in Table 1. A comparative visualization of trait-wise heritability and GA% trends for the individual crosses is depicted in Figures 1234.

Phenological Traits

For phenological traits, days to first flowering exhibited consistently high heritability across all crosses, ranging from 86.72% in Cross I to 96.16% in Cross III, along with moderate GA% values between 11.60 and 19.19%. This combination suggests the predominance of additive gene action with minimal environmental effects, implying that direct selection in early segregating generations would be effective for developing early-flowering genotypes. These results align with the findings of Patel et al. (2020) [18] , who also reported the efficiency of phenotypic selection for flowering time improvement in cotton. Similarly, days to maturity recorded high heritability values (84.30-94.20%) across all crosses with moderate GA% (10.50-17.30%), indicating that additive gene effects largely govern maturity duration. Therefore, selection based on phenotypic performance would enable effective improvement for earliness, which is desirable under changing climatic conditions and resource constraints. These findings are further supported by Lingaiah et al.

(2021) [11,12] , reinforcing the potential for efficient selection for earliness in cotton breeding programs.

Plant Architecture Traits Among plant architecture traits, plant height showed moderate to high heritability values ranging from 65.40% in Cross I to 82.30% in Cross II, with moderate GA% ranging from 12.54 to 18.63%. The highest heritability in Cross II combined with the highest GA in Cross I indicates the role of both additive and non-additive gene effects, suggesting that pedigree selection would be suitable for improving this trait in cotton breeding programs. Similar results for plant height improvement through pedigree selection were also reported by Ramesh et al. (2017) [19] , reinforcing the utility of this approach. The number of monopodia per plant exhibited very high heritability (>78%) across all crosses, with the maximum value in Cross III (92.30%). Furthermore, GA% was also extremely high (>50%), particularly in Cross III (90.16%). This combination of high heritability and high GA strongly indicates additive gene action, suggesting that direct selection in early generations would be highly effective for improving plant architecture through increased monopodia number. Similar observations were also reported by Meena et al. (2019) [14] , who highlighted the efficiency of earlygeneration selection for monopodia improvement in cotton.

Likewise, the number of sympodia per plant showed consistently high heritability (>80%), with Cross II recording the highest GA (63.93%). These results confirm that additive genetic effects control sympodial branching, implying that simple phenotypic selection in segregating generations would enhance the productivity potential of cotton genotypes by improving plant architecture. Comparable findings were noted by Sreelakshmi and Babu (2022) [22] , further validating the role of additive gene action in governing sympodial branching.

Yield and Economic Traits

Yield-contributing traits such as the number of bolls per plant exhibited moderate to high heritability (51.50-73.70%) along with high genetic advance as a percentage of the mean (GA%) exceeding 30%, particularly in Cross III. This combination suggests the predominance of additive gene effects, indicating that direct selection would be effective for improving boll number-a critical determinant of seed cotton yield. Similar results were reported by Lingaiah et al.

(2021) [11,12] , who also emphasized the role of additive gene action in the inheritance of boll number. (2017) [19] . Seed cotton yield per plant recorded moderate heritability values (50.10-53.00%) along with moderate to high GA% (15.72-24.10%) across all crosses. This pattern suggests the involvement of both additive and non-additive gene effects in yield inheritance. Hence, selection in later segregating generations, coupled with the simultaneous improvement of component traits, would be advantageous. Similar conclusions were drawn by Ramesh et al., (2017) [19] who advocated delayed selection strategies for traits influenced by both additive and non-additive effects. Lint yield per plant exhibited high heritability (>70%) combined with high GA% (>40%), with Cross IV showing the highest GA (43.90%). The predominance of additive gene action in this trait indicates that early-generation selection would be effective for improving lint yield, as also reported by Ramesh et al. (2017) [19] . Oil content recorded high heritability values (>72%) accompanied by moderate to high GA% (14.30-22.40%), especially in Cross I. The predominance of additive effects suggests that simple phenotypic selection would be highly effective for enhancing oil content in cottonseed, thereby increasing the economic value of the crop. Similar observations were noted by Patel et al. (2020) [18] , who also reported the efficiency of direct selection for this trait.

Fibre Quality Traits

For fibre quality traits, fibre length and fibre strength exhibited high heritability values exceeding 72% but were associated with low genetic advance as a percentage of the mean (GA%) below 9%. This combination suggests the predominance of non-additive gene effects and a substantial environmental influence on these traits. Consequently, heterosis breeding rather than simple phenotypic selection would be more effective for improving fibre length and fibre strength in cotton, as also noted by earlier studies (Ramesh et al., 2017) [19] . In contrast, fibre fineness recorded high heritability values exceeding 82% along with high GA% greater than 26%, particularly in Cross III (G. Cot 16 BG II × GBHV 281) and Cross IV (BC-68-2 BG II × GBHV 217). This association of high heritability with high GA% highlights the predominance of additive gene action, indicating that simple phenotypic selection would be effective for improving fibre fineness-an essential quality parameter for the textile industry (Meena et al., 2019) [14] . Across the four crosses, Cross III and Cross IV consistently exhibited high heritability combined with high genetic advance for key yield and quality traits such as monopodia, sympodia, bolls per plant, boll weight, lint yield, seed index, fibre fineness, and oil content. These crosses thus represent promising genetic material for cotton improvement programs targeting simultaneous enhancement of yield and fibre quality traits. Cross I (GBHV 276 × GBHV 278) and Cross II (GBHV 276 × GN Cot 32), although exhibiting moderate heritability for some traits, also displayed favorable genetic parameters for oil content, lint yield, and plant architecture traits. This indicates their potential utility in specific trait-improvement objectives through direct selection or hybridization programs, depending on the genetic architecture of the target traits.

Conclusion

The present investigation involving four cotton (Gossypium hirsutum L.) crosses revealed substantial genetic variability for yield, yield-attributing, and fibre quality traits, as [1,8,13] suggesting that direct phenotypic selection in segregating generations would be effective for these traits. [5] and Kadam et al. (2025) [10] . This genetic architecture indicates the efficiency of earlygeneration selection for improving these yield-contributing traits. Moreover, lint yield per plant (h²ns: 70. [15] and Rauf et al. (2024) [20] , suggesting that simple selection procedures would be effective for improving these traits in cotton breeding programs.

Conversely, seed cotton yield per plant exhibited moderate heritability (50.10-53.00%) with moderate GA (15.72-24.10%), indicating the influence of both additive and nonadditive gene effects. Such genetic control, as reported by Dhivya et al. (2014) [6] and Adeela et al. (2021) [2] , necessitates deferring direct selection for yield per se to later generations, while focusing on yield components initially for effective genetic improvement. [3,16] advocating heterosis breeding or recurrent selection strategies for improving these fibre quality parameters. Among the four crosses, G. Cot 16 BG II × GBHV 281 and BC-68-2 BG II × GBHV 217 consistently exhibited high heritability combined with high genetic advance for key yield and fibre quality traits. These crosses, therefore, emerge as promising parental combinations for developing high-yielding cotton genotypes with superior fibre quality (Nawaz et al., 2019; Meena et al., 2022) [17,15] . Overall, traits governed by additive gene action with high h²ns and GA (e.g., monopodia, sympodia, bolls per plant, boll weight, lint yield, seed index, fibre fineness, oil content) can be effectively improved through direct selection, while traits influenced by non-additive effects (e.g., fibre length, fibre strength, seed cotton yield) require hybridization and heterosis breeding approaches for genetic enhancement.

Acknowledgement

AcknowledgementsThe authors gratefully acknowledge the Regional Cotton Research Station, Navsari Agricultural University, Bharuch, Gujarat, for providing field and laboratory facilities. We are also grateful to the faculty members of the Department of Genetics and Plant Breeding, NAU, Navsari.

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