Cotton is known as the king of fiber crops and belongs to the family Malvaceae. In the world, it is cultivated as the most significant natural fiber and cash crop. A line x tester analysis was designed pointing towards the identification of best heterotic crosses for yield, fibre quality and economically important traits in upland cotton (Gossypium hirsutum L.). The current research was conducted at Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, six parents and nine crosses of cotton under RCBD Design with three replications. Data were collected on the plant's height, first fruiting branch, first effective boll-bearing branch's node number, monopodial and sympodial branches, no of fruiting nodes on each plant, weight and no of bolls, internodal distance, the yield of seed cotton per plant, the seed index, the lint index, the length and strength of the fiber, the uniformity ratio and micronaire value. Analysis of variance shown significant difference among all the studied traits. According to our findings for mean performance cross Kehkshan X CIM-602 best combiner for plant height, number of fruiting branches and fiber length, MNH-998 X CIM-602 best combiner for number of boll per plant, FH-215 X MNH-998 best combiner for GOT% while for better parent heterosis Kehkshan X CIM-602 shown maximum se performance and positive significantly associated with plant height, number of sympodial branches and seed index, MNH-998 X Kehkshan shown highest mid parent heterosis and significantly associated with number of bolls per plant and cross FH-215 X Kehkshan shown maximum se performance for mid parent heterosis which is significantly associated with lint index, micronaire value and seed index, While better parent heterosis FH-215 X Kehkshan shown maximum heterobeltiosis and positively significant associated with plant height, number of monopodial branches, sympodial branches and seed index. Therefore, CIM-622 X CIM-602 shown maximum heterobeltiosis and significant associated with seed cotton yield per plant. The best performer crosses could be utilized in future cotton breeding programme for development of new variety to boost up cotton industry.

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*Corresponding author: zahidakram721@gmail.com

Copyright 2023 TBPS

1. INTRODUCTION

Cotton is also referred to as "white gold," and main source of natural fiber. The cotton fiber is pure cellulose and their plant was grown like a shrub in nature. The cotton fiber is used to make yarn which is further utilized for making towels, curtains, and socks, etc. Its fiber also utilized in textile industry for cloth making (Stewart and Rossi 2010). A substantial amount of oil (16-27%) is haul out from cotton seed and seed cake is used in the livestock industry. The extracted oil from cotton seed is used as vegetable oil for making fries etc. because the taste of cotton seed oil is like to coconut oil. Moreover, it is an basic source of fat, vitamins and antioxidants (Dowd et al. 2010). Upland cotton shares around 90% of the world's cotton production, whereas only 3% is made up of Egyptian cotton (Fang et al. 2017). According to the Food and Agriculture Organization of the United Nations (FAO), the total cultivated area of cotton worldwide in 2021 was approximately 33.32 million hectares having production 25.58 million metric tons while in Pakistan total cultivated area of cotton was around 2.47 million hectares having their production is 8.93 million metric tons (FAO, 2021). Cotton has a significant position in the economy and agriculture of Pakistan. In Pakistan, during 2020-21 it is contributing 0.6% share in GDP of Pakistan and 3.1 % of the total value added in agriculture (GOP, 2020-21). The population of world is continuously increasing therefore; it is essential to enhance the productivity of crops to fulfill the requirement of textile industry. The utilization of many breeding tools in the cotton crop to enhanced their production to fulfill the demand of textile sector (Farooq et al. 2014). The information on the association between the traits should be available for plant breeder to understand the genetic basis of yield related parameters.

All the yield-related parameters are associated with each other in a way that increases or decreases in one characters directly affects others. Thus, assessment of phenotypic and genotypic association among these traits are helpful to initiate the breeding programs. The information on the correlation among several plant traits is helpful in the selection of suitable breeding programme (Teklewold et al. 2000). Phenotypic correlation demonstrates the visual observation although genotypic correlation estimates the inheritance of traits (Desalegn et al. 2009). Hybrid cotton is a positive approach for significant improvement in genetic potential for fibre quality and yield or yield related traits. Cotton is highly amenable for both heterosis and recombination breeding. Heterosis has considerably remained as one of the significant developments in cotton breeding method (Ranganatha et al. 2013; Choudhary et al. 2014). Numerous studies have been conducted on yield and yield related traits, but some work has been reported on the genetics and heterosis of yield fibre quality traits in cotton breeding. Many scientists described that cotton genotypes differ in fibre quality traits. Fibre quality of a specific cotton genotype is a combination of different characteristics, comprising fibre strength, fibre length, fineness or micronaire and fibre elongation. These parameters have their individual significance in spinning, weaving and dying units (Feng et al. 2011). Fibre length and strength properties mainly influence textile processing. In addition, fibre uniformity is also of remarkable value to the textile sector. It is significantly associated with the effective spinning and weaving processes, which change the fibre into fabrics. Ahuja, (2003) suggested that developing high fibre length and strength variety or hybrids is required to current modernized spinning mills. Hereafter, it is the need of the day to improve fibre quality in the dominating hirsutum genotypes, to fulfill the requirements of growing processing and textile sector. The estimates of per se performance and heterosis provided useful information with regard to the possibilities and extent of improvement in the fibre characters of breeding material through selection. The studies on heterosis in upland cotton for improvement of fibre traits has also been done by (Feng et al. 2011; Patil et al. 2012; Abro et al. 2014; Tuteja and Banga 2014). Keeping in view that the basic objectives of this study to estimates the heterosis among various morphological and fibers parameters using Line × Tester analysis, for the development of superior cross combination which can be utilized in the future cotton breeding programs.

1. MATERIALS AND METHODS

2.1. Plant Material and Experimental Site

The plant material consisted of six cotton lines collected from the Department of Plant Breeding and Genetics. The experiment was conducted in the experimental area of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan. The experimental site lies at 31º latitude and 73º longitudes while the elevation of land is about 184.2 m above sea level. The texture of the experimental soil was loamy.

2.2. Crossing Scheme

The six cotton varieties were crossed to develop nine F1 hybrids. The detail of parents and crosses are given in Table 1.

Table 1: Description of experimental material

2.3. Development of Crosses

During the winter season 2020-21, six varieties were planted in pots and placed in the greenhouse. Six different varieties were crossed to developed hybrids between February and March 2021. Hand pollination and emasculation were used to develop hybrids. Crossing was initiated one week after flower initiation. Flower buds that would likely open the following day were picked for emasculation. To avoid natural outcrossing, the anthers of the selected buds were carefully removed with the aid of forceps. Emasculation was performed from 3 to 6 PM. The next morning, between 9 and 11 AM, male parent pollen was used to pollinate the emasculated buds. One flower of the male parent fertilized four to five flower buds of the female parent. To avoid cross-pollination with unwanted pollen after pollination, the staminal column was once more wrapped with a straw tube of a white color. The white straw tubes were removed four days after pollination, when fertilization was complete. In order to generate enough crossed bolls for each cross combination, considerable care was taken to guarantee that the parents were not nicked.

2.4. Evaluation of Parents and Crosses

In 3rd June 2021, F1 hybrids along with the parents were planted in a randomized complete block design with three replications. Each replication consisted of a single row for each entry containing 10 plants. Row-to-row and plant-to-plant distances were maintained at 75 and 30cm, respectively. All the recommended agronomic practices were done during the whole experiment. Five guarded plants were randomly selected from each F1 progeny and the parents from each replication for data collection.

2.5. Data Collection

Parameters included in this study are Plant height (cm), Number of monopodial branches, No of Sympodial branches, Number of fruiting nodes per plant, Node number for 1st fruiting branch, Node no for first effective boll bearing branch, Number of bolls per plant, Boll weight (g), Height node ratio (cm), Seed index, Seed cotton yield per plant, Ginning Out Turn, Fiber Length, Fiber Strength, Micronaire value and Uniformity Ratio. Furthermore, lint index, ginning out turn and earliness index was measured by following formulas:

Lint index         =   weight of 100 seeds x ginning outturn percentage x100

                                       100 – ginning outturn percentage

GOT%               =               lint weight (g) x 100

                                            Seed cotton yield (g)       

Earliness index   =        seed cotton weight of 1st harvest x 100

                                       Seed cotton weight from all harvested

Statistical Analysis

Recorded data for all parameters was subjected to analysis of variance for all the character as described by (Steel et al. 1997). The percent increase (+) or decrease (-) of F¹ over mid and better parents was determined using following formula (Mather and Jink. 1982).

1. RESULTS

Mean square of the line × tester analysis observed significant (p ≤ 0.05) genetic differences among the genotypes for Node for first effective boll bearing branches and fiber strength, whilst highly significant differences were shown (p ≤ 0.01) between the genotypes for plant height, number of monopodial branches, number of sympodial branches, Number of fruiting nodes per plant, Node number for 1st fruiting branch, Number of bolls per plant, Boll weight, Seed index, Seed cotton yield per plant, Ginning Out Turn, Fiber Length, Micronaire value, Uniformity Ratio, Lint index and Earliness index. Moreover, non-significant (p ≥ 9.05) difference among the genotypes for height node ratio. So it is reporting that maximum genetic variability among the studied materials which can be utilized in future for the development of improved cotton varieties Table 2.

According to the mean performance Table 3 and 4 for parents and crosses highest values of plant height has (114.55) showed by CIM-622 and the lowest value was (94.23) exhibited by Kehkashan and VH-367. In F1 crosses, (119.38) was highest value by Kehkshan×CIM-602 and (89.66) was lowest plant height recorded for FH-215×kehkshan. The parents VH-367 showed the highest values of number of sympodial branches were (25.3) and the lowest value was (19.30) revealed by CIM-602. In F1 crosses, Kehkshan×CIM-602 was highest number of sympodial branches (29.9) and FH-215×kehkshan has lowest number of sympodial branches (18). According to our findings Parent CIM-622 achieved the highest values of number of monopodial branches has (2.8) and CIM-602 and FH-215 has the lowest value of number of monopodial branches (1.5). While F1 cross CIM-622×Kehkshan has the highest mean of number of monopodial branches (3.1) and (1.2) was lowest mean by FH-215×kehkshan. Therefor parent, VH-367 has the maximum mean value for Number of fruiting nodes per plant (25.3) and CIM-602 has the lowest Number of fruiting nodes per plant (19.3), whilst in F1 crosses Kehkshan×CIM-602 has the highest number of Number of fruiting nodes per plant (29.9) and FH-215×kehkshan has the lowest Number of fruiting nodes per plant (18). In parents CIM-602 has the maximum mean value for Node number for 1st  fruiting branch  (8.9) and  FH-215  has  the lowest mean  value  for Node number for 1st fruiting branch (7.2). Moreover, in F1 crosses MNH-998×CIM-602 has the maximum mean value for Node number for 1st fruiting branch (7.62) and FH-215×kehkshan and CIM-622×CIM-602 revealed the lowest Node number for 1st fruiting branch (6.4). The parent VH- 367 attained the maximum Node number for first effective boll bearing branch (11.9) and parent MNH-998 had the lowest Node number for first effective boll bearing branch (9.6), while in F1 crosses FH-215×CIM-602 achieved the maximum Node number for first effective boll bearing branch (11) and CIM-622×Kehkshan has the lowest mean value (7.75). According to our results, maximum Number of bolls per plant was recorded in parent VH-367 (21.7) which is consider as high yielding and minimum Number of bolls per plant was recorded in MNH-998 (10.7). While in F1 crosses, MNH-998×CIM-602 has the maximum Number of bolls per

Table 2: Analysis of variance for different characters in upland cotton

Table 3: Mean performance of parents for different characters in upland cotton

Table 4: Mean performance of F1 hybrids for different characters in upland cotton

plant (24.8) and VH-367×CIM-622 has the minimum Number of bolls per plant (17.1). The results in Table 3 and 4 showed that the parent VH-376 attained a higher value for Boll Weight (3.7) and lower value in parent CIM-622 (2). While in F1 crosses, (3.4) was highest mean exhibited by CIM-622×CIM-602 and (2.5) was lowest mean showed by MNH-998×CIM -602 for Boll Weight. According to our results maximum height node ratio was reported in parent Kehkashan (3.5) and lowest height node ratio was exhibited in VH-367 (3.2), while in F1 hybrid crosses FH-215× CIM-602 and Kehkshan×CIM-602 reported the maximum (3.72) and lowest (3.19) for height node ratio respectively. According to the Table 3 and 4, parent CIM-602 and VH-367 have the highest mean value (8.5) and CIM-622 and Kehkashan have the lowest mean value (6.5) for seed index. While in F1 crosses, the maximum value (9) shown by the FH-215×kahkshan and kahkshan×CIM-602. Therefore, in parents, highest values of mean were 78.9 exhibited by VH-367 and the lowest value was 30.7 by MNH-998, While F1 crosses, 75.19 was highest was highest value of seed cotton yield revealed by CIM-622×CIM-602 and 50.6 was lowest value showed by FH-215×kehkshan for seed cotton yield per plant. In parents, highest values of ginning out turn were (46.5) showed by CIM-622and the lowest value was (39.6) revealed by CIM-602. In F1 crosses, (48.08) was highest ginning out turn exhibited by CIM-622×CIM-602 and the lowest ginning out turn was (36.42) presented by VH-367×CIM-622. For fiber length.in parents, highest values of mean were (29.35) showed by MNH-998 the lowest value was (24.65) by FH-215.in F1 crosses, (27.45) was highest mean by Kehkshan×CIM-602 and 23.75 was lowest mean by VH-367×CIM-622. However, in parents, highest values of mean were (27.4) showed by MNH-998 the lowest value was (26.2) exhibited by CIM-602 In F1 crosses, (30.75) was highest mean by FH-215×MNH-998 and (24.15) was lowest mean by FH-215×CIM-602 for fiber strength.

According to our findings for micronaire highest mean value from all parents were (5.25) showed by CIM-622 and the lowest value was (4.3) presented by FH-215.in F1 crosses, (5.5) was highest mean by FH-215×kehkshan and 4.00 was lowest mean by CIM-622×Kehkshan. Mean comparison values are given in Table 2 and 3 for uniformity ratio. In parents, highest values of mean were (84.3) showed by CIM-622 the lowest value was (81.9) by Kehkashan.in F1 crosses, (85.2) was highest mean by VH-367×FH-215 and (81.5) was lowest mean by VH-367×CIM-622. It revealed that in parents, highest values of lint index were (316.7) showed by VH-367and the lowest value was (223.4) revealed by Kehkashan. In F1 crosses, (371.6) was highest lint index exhibited by Kehkshan×CIM-602 and the lowest lint index was (210.47) presented by CIM-622×CIM-602. While It depicted that mean comparison values are given in Table 2 and 3 for earliness index. In parents, highest values of mean were 78.58 showed by CIM-622 and the lowest value was 42.62 revealed by VH-367. In F1 crosses, 75.65 was highest mean exhibited by FH-215xkehkshan and 25.14 was lowest mean by KehkshanxCIM-602.

3.1. Better Parent and Mid Parent Heterosis

3.1.1. In this Experiment for Plant Height

FH-215×kehkshan showed the lowest heterosis (-4.206) while two crosses VH-367×FH-215 and FH-215×CIM-602 exhibited the maximum heterosis (16.14) and (16.64). Four crosses VH-367×FH-215, FH-215×CIM-602, CIM-622×Kehkshan and Kehkshan×CIM-602 revealed positive significant heterosis (16.14, 16.64, 11.43 and 23.39) while four crosses MNH-998×CIM-602, FH-215×kehkshan, CIM-622×CIM-602, VH-367×CIM-622 and FH-215×MNH-998 revealed non-significant positive and negative heterosis. VH-367×CIM-622 showed the lowest heterobeltiosis (-11.08) and Kehkshan×CIM-602 displayed the highest heterobeltiosis (18.38). Five crosses showed significant positive and negative heterobeltiosis. While remaining four crosses revealed non-significant heterobeltiosis. The estimates of heterosis and heterobeltiosis are shown in Table 5 and 6. VH-367×CIM-622 revealed the lowest value of heterosis (21.41) while two crosses Kehkshan×CIM-602 and MNH-998×CIM-602 showed the maximum value of heterosis (45.8) and (43.8). Four crosses MNH-998×CIM-602, CIM-622×CIM-602, FH-215×CIM-602 and Kehkshan×CIM-602 revealed positive significant heterosis (43.8, 30.16, 29.20and 45.8) while five crosses FH--215×kehkshan, VH-367×FH-215, CIM-622×Kehkshan, VH-367×CIM-622 and FH-215×MNH-998 revealed non-significant positive and negative heterosis. VH-367×CIM-622 exhibited the lowest value for heterobeltiosis (-25.29) and MNH-998×CIM-602 showed the highest value of heterobeltiosis (42.04). Four crosses showed significant positive and negative heterobeltiosis. While remaining five crosses revealed non-significant  heterobeltiosis.  Formation of  more sympodial branches increases the  opportunity for  more  number of bolls produced by the individual plant. For node number of effective boll bearing branches, the estimates of heterosis and heterobeltiosis are shown in table 4.3.2. VH-367×CIM-622 displayed the lowest heterosis (28.31) while cross MNH-998×CIM-602 showed the maximum heterosis (5.97). Three crosses MNH-998×CIM-602, FH-215×CIM-602 and Kehkshan×CIM-602 revealed positive significant heterosis (5.97, 4.26 and 1.92) while six crosses revealed non-significant negative heterosis FH-215×kehkshan, CIM-622×CIM-602, VH-367×FH-215, CIM-622×Kehkshan, VH-367×CIM-622, FH-215×MNH-998 (-15.7, -6.1, -12, -26.1, -28.3 and -12.8) respectively. VH-367×CIM-622 exhibited the lowest value for heterobeltiosis (-31.9) and FH-215×CIM-602 showed the highest value of heterobeltiosis (3.77). Three crosses presented significant positive heterobeltiosis. While remaining six crosses revealed non-significant negative heterobeltiosis. According to our findings for earliness index, the estimates of heterosis and heterobeltiosis are shown in table 4.4.2. Kehkshan×CIM-602 exhibited the lowest heterosis (-56.77) while crosses FH-215 ×Kehkashan showed the maximum heterosis (13.12). Three crosses FH-215×kehkshan, CIM-622×Kehkshan and VH-367×CIM-622 revealed positive significant heterosis (13.12, 7.15 and 17.8) while six crosses MNH-998×CIM-602, CIM-622×CIM-602, VH-367×FH-215, FH-215×CIM-602, FH-215×MNH-998 and Kehkshan×CIM-602 revealed significant negative heterosis.

Kehkshan×CIM-602 showed the lowest heterobeltiosis (-57.08) and FH-215×kehkshan exhibited the highest heterobeltiosis (1.002). One cross showed significant and positive heterobeltiosis. While remaining eight crosses revealed  negative  non-significant  heterobeltiosis.  The  estimates  of  heterosis  and  heterobeltiosis  for number of

Table 5: Estimated Mid parent heterosis effects of F1 hybrids for different traits in upland cotton