Genetic studies of earliness in Gossypium hirsutum L.

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1 RESEARCH ARTICLE Shakeel et al., IJAVMS, Vol. 6, Issue 3, 2012: doi: /ijavms.147 Genetic studies of earliness in Gossypium hirsutum L. Amir Shakeel 1, Jehanzeb Farooq 3 *Ameer Bibi 1, Shaham Hamayoun Khan 1 and M. Farrukh Saleem 2 1 Department of Plant Breeding and Genetics, 2 Department of Agronomy, University of Agriculture, Faisalabad. 3 Cotton Research Institute, Ayub Agricultural Research Institute, Faisalabad. Pakistan. Corresponding author s ameerbibi@gmail.com) Rec.Date: May 13, :04 Accept Date: Jun 17, :15 Abstract The present studies were designed to obtain suitable parents and crosses by estimating GCA and SCA of various traits relating to earliness, yield and fiber quality. The experiment comprised of eight genotypes including three male testers COKER310, LRA-5166 and CP-15/2 and five lines naming PB- 899, FH1000, MNH-552, BH-160, CIM-496. These genotypes were crossed in a line x tester fashion and combining ability effects were computed for various traits. Both additive and non-additive genetic effects were present in controlling the plant traits. Among lines CIM-496 proved the best general combiner for almost all the traits followed by PB-899, FH-1000, BH-160 and MNH-552. Among testers best combining ability effects were shown by CP-15/2 for almost all the traits studied. The hybrids showing good specific combining effects are CIM-496 CP-15/2 for days to squaring, days to flowering, number of bolls per plant and seed cotton yield, PB-899 CP-15/2 for horizontal flowering interval, number of days taken to first boll opening and fiber fineness, BH-160 LRA-5166 for boll maturation period, MNH-552 LRA-5166 for node number for first fruiting branch, FH-1000 COKER-310 for height of first fruiting branch, BH-160 COKER-310 for mean maturity date and earliness index, FH-1000 LRA-5166 for seed cotton yield and fiber length, FH-1000 CP-15/2 for lint percentage. The results of present investigation will facilitate the selection in cotton breeding program to develop varieties possessing early maturity in early generations for the traits showing additive effects and later generation selection for the traits exhibiting non-additive genetic effects. Hybrid breeding might be fruitful in case of crosses showing vigor for yield, earliness and fiber quality. Keywords: General combining ability, Specific combining ability, Variance, Line tester, Cotton, earliness Introduction Cotton is an important non-food cash crop which occupies unique position in global trade as it is the major agricultural and industrial crop. Cotton is the leading fiber crop grown over 80 countries worldwide 13. Cotton not only an essential source of foreign exchange in Pakistan but also provides income to the local people 4,3,27. Pakistan is predominantly an agricultural country, and due to varying environmental conditions, from north to south, an array of crops is grown in winter, autumn, spring and

2 summer seasons. Spring wheat Triticum aestivum is staple food of people in Pakistan, and thus crop is grown on an extensive area, following different rotation systems, to meet the demand of food supply to increasing population. Wheat-cotton-wheat rotation is normally practiced in southern Punjab. This rotation system along with cultivation of late maturing cotton varieties results in delayed planting of wheat crop thus severely affecting wheat yield 27. Breeding for early maturing varieties is the only solution for this problem. Early maturing cotton varieties can also avoid losses due to diseases and insect pest complex 28. In the month of September cotton belt of Punjab is severely affected due to onset of whitefly, pink bollworm and other sucking insect pests. The yields may also be reduced during 3 rd week of September and 4 th week of October due to high population of Heliothis 6. Late maturing of cotton results in the development of poor grading fiber characteristics like staple length, fineness and strength decline in late pickings and late picking also affected the ginning out percentage, seed index and lint index. Many crop breeders have tried to improve early maturity genotypes. Early maturing varieties increased the possibility that harvest can be completed before cold and rainy weather. In another way early maturity of cotton is preferred because of decreasing inputs of fertilizer, irrigation, crop protection and providing proper time for rotation of the other crops. Earliness in cotton is a complex character which is assessed by measuring many plant traits. The traits like node of first fruiting branch, number of vegetative branches, percent of bolls on vegetative branches are vital for measuring earliness, 1 st sympodial node number on main stem, date of 1 st flower and date of 1 st open boll were used for assessing earliness in cotton 9. To formulate breeding programme related to earliness availability of two components is essential, firstly, there must be variation in the genetic material and secondly, the variation must be under the control of additive component. The study of the literature shows that information on both these components regarding earliness in Gossypium hirsutum is very little. Some breeders also reported variation for earliness in cotton 5, 25. While the role of additive gene effects for days taken to flowering have also been depicted by 18. Combining ability analysis is an important tool for the selection of desirable parent together with the information regarding nature and magnitude of gene effect controlling quantitative traits. There are two ways for finding combining ability, one way is through line Tester fashion and other is through diallel fashion. Work on combining ability studies is reported by many researchers few of them are mentioned here 10. Therefore, in order to breed early maturing cotton varieties, it is necessary for the breeders to have working knowledge on inheritance of plant characters related to earliness of cotton crop. In present studies 8 varieties of varying maturity and agronomic characters were selected and crossed in Line Tester fashion 20 and hybrid seeds along with their parents were planted in field. The information given here may be helpful to breeders doing research work on early maturity of cotton. Material and Methods The present experiment was carried out at experimental area of the department of Plant Breeding and Genetics, University of Agriculture, Faisalabad during the year The experiment material consisted of eight parental genotypes namely PB-899, FH1000, MNH-552, BH-160, CIM496, COKER310, LRA-5166 and CP-15/2. Out of these eight parents three were used as a male i.e. COKER310, LRA-5166 and CP-15/2 and 5 were used as a female i.e. PB-899, FH1000, MNH-552, BH- 160 and CIM496. The parents were sown in earthen pots placed in glass house during November During germination and growth, glass house conditions were possibly controlled and recommended

3 agronomic practices were carried out. At flowering stage 5 lines were crossed to 3 testers followed by line tester fashion to generate 15 F 1 hybrids along with 8 self. At maturity, selfed and crossed bolls were picked and was ginned with single roller ginning machine. The seeds of 15 crosses and their 8 parents were field planted during May-June Each of 23 entries was sown followed by randomized complete block design in 3 replications. The seeds were sown in rows having 11 plants spaced 30 cm plant to plant distance and 75 cm row to row distance. For measuring the characters 5 representative, undamaged plants were selected in each line and marked for identification. Data regarding appearance of 1 st square and flower was taken by counting number of days from planting to the appearance of 1 st square and 1 st flower respectively. For vertical flower interval number of days between flowerings at corresponding nodes on successive fruiting branch, up the main stem was recorded from each guarded plant. The number of days between the appearances of flowers on the same fruiting branch is called horizontal flowering interval and data regarding to this character was collected from each plant. Number of days from sowing to the opening of 1 st boll was counted from each tagged plant. The time from anthesis of the flower until the resulting boll sufficiently open to see the lint is referred as boll maturity period. Boll maturation period in each family and in each replication was calculated as: Boll maturation period (days) = Days taken to 1 st boll opening Days taken to 1 st flower. Nodes to 1 st fruiting branch counted from zero node (cotyledonary node) to the node at which first flower was appeared. The height of first fruiting branch was recorded in centimeters from zero node to first sympodial branch with the help of measuring tape The procedure to calculate mean maturity date was given by 12 which is calculated by formula MMD = W1H1 + W2H WnHn / W1 + W Wn Earliness index is calculated as mean yield of first picking divided by total yield and multiplied by 100 of each family in each replication for the purpose of data analysis. Average boll weight in grams (g) was calculated by dividing the total seed cotton yield per plant with the total number of bolls of that plant. Mean boll weight of each plant was taken in grams (g) and then overall averaged. Number of bolls counted from the guarded plants upto final picking. The bolls were picked and seed cotton yield was calculated in grams (g). The harvest was weighed with the help of electrical balance and finally averages were made from each tagged plant. Cleaned and dry samples of seed cotton were weighed and then ginned separately with single roller electric ginning machine. The lint obtained from each sample was weighed and ginning out turn % was calculated by the following formula Ginning outturn (%) = Weight of lint / Weight of seed cotton 100 Fiber characteristics such as staple length, fiber fineness and fiber strength of each guarded plant were measured by using spin lab HVI-900. This computerized instrument provides us true profile of raw fiber. It measures the most important characters such as staple length (mm), fiber fineness (µg/inch) and fiber strength (g/tex) with in quick period of time according to international trading standards. Statistical analysis: Data on all the characters of 23 entries were subjected to simple analysis of variance technique 29 in order to determine genotypic differences for the characters. The characters showing significant genotypic differences were subjected to line tester analysis given by 20 to estimate the general and specific combining ability effects. Results

4 Results of mean squares from analysis of variance showed that genotypic differences for all the characters were significant Table-1a&1b. Parents were significant for all characters except vertical flowering interval, days taken to first boll opening, boll maturation period, mean maturity date and earliness index. Crosses were significant for days to squaring, days to flowering, horizontal flowering interval, days taken to first boll opening, boll maturation period, node number for first fruiting branch, mean maturity date, boll weight, bolls per plant, seed cotton yield, lint percentage and fiber fineness. Parents vs crosses was significant for days to squaring, days to flowering, horizontal flowering interval, days taken to first boll opening, node number for first fruiting branch, height of first fruiting branch, mean maturity date, earliness index, boll weight, bolls per plant and seed cotton yield. Mean squares of lines were significant for node number for first fruiting branch, mean maturity date, earliness index, and fiber length and fiber strength. Testers were non-significant for all the characters. Line Tester was significant for days to squaring, vertical flowering interval, horizontal flowering interval, boll maturation period, height of first fruiting branch, boll weight, bolls per plant, seed cotton yield, lint percentage and fiber fineness. General combining ability effects: Negative estimates of general combining ability were desirable for days to squaring and days to 1 st flower. Effects of general combining ability (GCA) on controlling number of days to squaring were variable for parents Table-2a&2b. All parents showed negative GCA except CIM-496, MNH-552, CP-15/2. For reduction of maturity duration this negative value is suitable. Among lines BH-160 showed maximum negative and significant value of GCA (-2.42) followed by PB- 899 (-1.42) and FH-1000 (-0.21) which showed that these are good general combiners for reduction in number of days to squaring. Among testers LRA-5166 (-0.82) and COKER-310 (-0.54) are good general combiner for the character respectively. Among lines MNH-552 (3.31) and in testers CP-15/2 (1.36) displayed positive and significant results but undesirable GCA effects. For number of days to flowering CIM-496 (-1.20) displayed desired maximum negative and significant GCA effects. Next to CIM-496 the good general combiner lines were MNH-552 (-0.98) and BH-160 (- 0.32) respectively as they also showed negative GCA for the character. Two lines i.e. PB-899 (1.85) and FH-1000 (0.65) displayed positive GCA for the character which showed that both are not good general combiners but among testers CP-15/2 (-0.06) and COKER-310 (-0.008) displayed negative and desirable GCA effects. LRA-5166 (0.07) showed positive GCA but it is undesirable in case of days to flowering. For vertical flowering interval among lines BH-160 and MNH-552 displayed negative GCA effects which revealed that they are good general combiners. PB-899, CIM-496 and FH-1000 displayed positive GCA for the character respectively which revealed that they are not good general combiners as positive estimates are not desirable in case of vertical flowering interval. Among testers CP-15/2 and LRA-5166 marked as good general combiners respectively for character as they had negative GCA. COKER-310 was not good general combiner for the character as it has positive GCA for the character. Among the lines CIM-496 (-0.15) displayed maximum negative and significant GCA for horizontal flowering interval which revealed that it is good general combiner followed by BH-160 (-0.042), while MNH-552 (0.04), PB-899 (0.07) and FH-1000 (0.08) respectively displayed positive GCA which is not desirable for horizontal flowering interval. Among the testers COKER-310 (-0.05) and CP-15/2 (-0.03) showed negative GCA and marked as good general combiners. LRA-5166 (0.08) though showed positive GCA but positive effects are not desirable. Less number of days required for 1 st boll opening. CIM-496 (-2.48) followed by FH-1000 (-1.19) and MNH-552 (-0.02) displayed maximum negative and significant GCA thus proving good combiners for this trait. BH-160 (2.42) and PB-899 (1.27) proved poor general combiners as they had maximum

5 positive GCA which is undesirable for earliness in cotton. Among the testers COKER-310 (-0.49) and LRA-5166 (-0.44) showed maximum negative GCA for the aforementioned character which revealed them as good general combiners, while CP-15/2 (0.94) displayed positive GCA, which is not desirable for days to 1 st boll opening. CIM-496 (-2.34) marked as a good general combining line for boll maturation period as it displayed maximum negative and significant GCA, while PB-899 (2.82) displayed maximum positive GCA for the character which showed that it is poor general combiner for boll maturation period. Among the testers LRA-5166 (-0.33) and CP-15/2 (-0.28) showed maximum negative GCA for the character which revealed them as good general combiners, while COKER-310 (0.61) displayed positive GCA, thus showing poor combining ability. For node number to 1 st fruiting branch CIM-496 (-0.82) displayed maximum negative and significant GCA, while FH-1000 (1.47) displayed maximum positive GCA for the character which showed that it is poor general combiner for the character. Among the testers CP-15/2 (-0.30) showed maximum negative GCA for the character which revealed it as good general combiners, while COKER- 310 (0.22) displayed positive GCA, which is indicative of its poor combining ability in case of node number to 1 st fruiting branch. Height of 1 st fruiting branch is required in negative. The line MNH-552(-1.01) marked as a good general combiner for this character by showing negative desirable GCA, while CIM-496 (1.08) displayed maximum positive estimates for the character which are not desirable for this trait. Among the testers LRA-5166 (-0.14) showed maximum negative GCA thus revealed it as good general combiners, while CP-15/2 (0.11) displayed maximum positive GCA, which is of no use in case of height of 1 st fruiting branch. Effects of general combining ability (GCA) on controlling mean maturity date were variable for parents. CIM-496 (-1.38) marked as a good general combining line for the character as it displayed maximum negative and significant GCA followed by FH-1000 (-0.83). Among the testers COKER-310 (- 0.65) and CP-15/2 (-0.08) showed maximum negative GCA for the character which revealed them as good general combiners, while LRA-5166 (0.74) displayed positive but undesirable GCA. Effects of general combining ability (GCA) on controlling earliness index were variable for parents. MNH-552 (2.93) marked as a good general combining line as it displayed positive and significant GCA followed by FH-1000 (1.18). Among the testers CP-15/2 (1.31) showed maximum positive GCA for the character which revealed its good combining ability, while LRA-5166 (-0.98) displayed negative GCA which is not required in case of earliness index. For boll weight CIM-496 (0.20) displayed maximum positive GCA followed by MNH-552 (0.077) while FH-1000 (0.007) displayed minimum estimates which showed that it is poor general combiner for boll weight. Among the testers CP-15/2 (0.022) showed maximum GCA while LRA-5166 ( ) displayed negative GCA, which is not desirable in case of boll weight. The line CIM-496 (1.45) displayed maximum positive GCA followed by BH-160 (1.40), while MNH-552 (-1.75) displayed negative GCA for bolls per plant. Among the testers LRA-5166 (3.44) showed maximum and significant GCA while CP-15/2 (-1.82) displayed negative GCA, this showed that it is poor general combiner for the character. For seed cotton yield maximum positive and significant GCA was shown by the line CIM-496 (1.27), followed by FH-1000 (0.56) while BH-160 (-0.65) displayed maximum negative GCA. Among the testers maximum and significant GCA was shown by LRA-5166 (3.01), while CP-15/2 (-2.47) displayed negative GCA.

6 The line CIM-496 (1.27), displayed maximum positive and significant GCA followed by FH (0.56), while BH-160 (-0.65) displayed maximum and negative GCA for lint percentage. Among the testers CP-15/2 (0.98) showed maximum and significant GCA for the character while COKER-310 (0.85) displayed negative GCA. The line MNH-552 (0.70), displayed maximum positive and significant GCA followed by FH (0.58), while PB-899 (-0.64) displayed maximum negative GCA for fiber length. Among the testers CP-15/2 (0.57) showed maximum and significant GCA while, LRA-5166 (-0.58) displayed negative and undesirable GCA for fiber length. For fiber strength MNH-552 (1.04), marked as a good general combining line as it displayed maximum positive and significant GCA followed by CIM-496 (0.88), while PB-899 (-1.07) displayed maximum and negative GCA. Among the testers COKER-310 (0.16) showed maximum and significant GCA for the character which revealed it as good general combiners, while LRA-5166 (-0.27) displayed negative GCA, this showed that it is poor general combiner for the character. The lines BH-160 (-0.28) and FH-1000 (-0.13) displayed maximum negative GCA in case of fiber fineness. CIM-496 (0.23) and PB-899 (0.23) proved poor general combiners as they had maximum positive GCA for the characters which is undesirable for fiber fineness. Among the testers COKER-310 (- 0.07) and CP15/2 (-0.05) showed maximum negative GCA for the character which revealed them as good general combiners, while LRA-5166 (0.12) displayed positive GCA. Specific Combining ability effects: Specific combining ability of the cross CIM 496 CP 15/2 (-2.84) was negative and significant followed by MNH 552 CP 15/2 (-2.34), BH 160 COKER-310 (-2.22) for number of days to squaring Table-3a&3b. BH 160 CP 15/2 (2.08) displayed maximum positive SCA which is not desirable for this trait. The value for the degree of dominance (δ 2 D/ δ 2 A) was 3.56 which is indicative of non-additive gene effects Table-4a&4b. The hybrid CIM-496 CP-15/2 (-1.45) showed maximum negative and significant SCA for days to 1 st flower and marked as good specific combiner. The hybrids FH-1000 LRA-5166 (-0.96), MNH 552 COKER-310 (-0.86) and PB-899 COKER 310 (- 0.81) also displayed negative desirable specific combining ability effects. The hybrids FH 1000 COKER-310 (1.45) and CIM 496 LRA 5166 (0.98) displayed positive SCA effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was 2.28 which showed over dominance. The cross PB 899 COKER-310 (-0.24) showed maximum negative and significant SCA for vertical flowering interval. The cross combination CIM 496 LRA 5166 (-0.16) remained 2 nd regarding desirable negative SCA effects, while all other crosses displayed positive SCA effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed that character is controlled by additive gene action. For horizontal flowering interval the cross PB-899 CP-15/2 (-0.25) displayed maximum negative desirable and significant SCA followed by BH-160 LRA-5166 (-0.17), while BH 160 CP 15/2 displayed positive SCA effects for the character which showed that these are not good specific combiners as for earliness positive SCA indicates increase in maturity duration. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed that character is controlled by additive gene action. For number of days to 1 st boll opening hybrid PB-899 LRA-5166 (-3.84) displayed maximum negative and significant SCA followed by BH-160 LRA-5166 (-2.28), FH-1000 CP-15/2 (-1.38), MNH-552 LRA-5166 (-1.35), CIM-496 COKER-310 (-1.03) and FH-1000 COKER-310 (-0.27) respectively, while all other crosses showed positive SCA especially maximum positive SCA was shown by MNH-552 CP-15/2 (3.31) which revealed poor SCA effects for the character. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed over dominance. The hybrid BH-160

7 LRA-5166 (-2.5), displayed maximum negative and significant GCA followed by PB-899 CP-15/2 (- 2.33), while maximum positive SCA was shown by MNH-552 CP-15/2 (2.60) which revealed poor SCA effects for boll maturation period. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed over dominance. For node number to 1 st fruiting branch PB-899 CP-15/2 (-0.82) and MNH-552 LRA-5166 (- 0.58) displayed maximum negative SCA for the character and marked as good specific combiners, while FH-1000 LRA-5166 (0.75) displayed maximum positive SCA values for the character. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was 0.48 which showed additive effects. The hybrids FH-1000 COKER-310 (-1.63) and BH-160 LRA-5166 (-1.3) displayed maximum negative SCA for the character and marked as good specific combiners, while FH-1000 LRA-5166 (2.6) displayed maximum positive SCA values for height of first fruiting branch which showed that this hybrid has not good specific combining ability effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed additive effects. Regarding mean maturity date the hybrids BH-160 COKER-310 (-1.10) and MNH-552 CP- 15/2 (-0.87) displayed maximum negative SCA for the character and marked as good specific combiners, while MNH-552 COKER-310 (1.48) displayed maximum positive SCA values for the character which showed that this hybrid has not good specific combining ability effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed additive effects. The hybrids BH-160 COKER-310 (3.05) and FH-1000 CP-15/2 (1.54) displayed maximum positive SCA for the character and marked as good specific combiners, while BH-160 LRA-5166 (-2.57) displayed maximum negative SCA values for the character which showed that this hybrid has not good specific combining ability effects for earliness index. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was -3.2 which showed additive effects. The hybrids MNH-552 COKER-310 (0.36) and BH-160 CP-15/2 (0.16) respectively displayed maximum positive SCA for boll weight and marked as good specific combiners, while MNH- 552 CP-15/2 (-0.25) displayed maximum negative SCA values for the character. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed additive effects. The cross combinations CIM-496 CP-15/2 (5.93) and FH-1000 LRA-5166 (5.52) displayed maximum positive SCA for the character and marked as good specific combiners, while FH-1000 CP-15/2 (-6.24) displayed maximum negative SCA values for the character followed by CIM-496 LRA-5166 (-5.2) which showed that these hybrid have not good specific combining ability effects for boll number per plant. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed over dominance effects. For seed cotton yield per plant FH-1000 LRA-5166 (15.70) and CIM-496 CP-15/2 (14.64) displayed maximum positive SCA for the character while, FH-1000 CP-15/2 (-17.98) displayed maximum negative SCA values for the character followed by CIM-496 COKER-310 (-8.42) which showed that these hybrid have not good specific combining ability effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was (Table 4.39) which showed additive effects. For lint percentage the hybrids FH-1000 CP-15/2 (2.04) and CIM-496 CP-15/2 (1.17) showed maximum positive and significant SCA while, BH-160 CP-15/2 (-1.88) displayed maximum negative SCA values followed by FH-1000 COKER-310 (-1.33) which showed that these hybrid are not good specific combiners for lint percentage. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was 17.9 which over dominance effects. For fiber length hybrids CIM-496 LRA-5166 (0.54) and FH-1000 LRA5166 (0.52) proved good specific combiners by showing maximum positive and significant SCA, while MNH-552

8 LRA5166 (-0.86) displayed maximum negative SCA value for the character followed by CIM-496 CP- 15/2 (-0.38) which showed that these hybrid have not good specific combining ability effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed additive effects. Regarding fiber strength the hybrids BH-160 CP-15/2 (0.77) and FH-1000 LRA5166 (0.55) displayed maximum positive and significant SCA for the character while BH-160 COKER-310 (-0.45) displayed maximum negative SCA value for this trait followed by CIM-496 CP-15/2 (-0.42). The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was which showed additive effects. Negative estimates of fiber fineness are desirable. Maximum negative and significant SCA effects were shown by the hybrids CIM- 496 LRA-5166 (-0.34) and PB-899 CP-15/2 (-0.17) while CIM-496 CP-15/2 (0.26) displayed maximum positive SCA value for the character followed by BH-160 LRA-5166 (0.25) which showed that these hybrid have not good specific combining ability effects. The value of ratio of dominance to additive (δ 2 D/ δ 2 A) was 5.8 which showed over dominance. Discussion Earliness of crop maturity is an important objective in most cotton breeding programs, although the developmental factors that determine it are not completely understood. It is apparent that no single criterion provides an adequate indicator for earliness, and that effective alteration of maturity is achieved by selecting for more than one component of earliness. Biometrical analysis of the data revealed that variation in days to squaring, days to flowering, vertical flowering interval, horizontal flowering interval, days taken to first boll opening, boll maturation period, node number for first fruiting branch, height of first fruiting branch, mean maturity date, earliness index, boll weight, number of bolls per plant, seed cotton yield, lint percentage, fiber length, fiber strength, fiber fineness were genetically manifested. The genetic variability in each character was further partitioned into various components i.e. due to general and specific combining ability as out lined by 20. The relative contribution of general and specific combining ability provided some understanding on the genetic control of the characters. Additive and non-additive genes effects are discussed below for all the traits. Non-additive genetic effects were predominant for number of days to squaring, days to flowering, days taken to 1 st boll opening, boll maturation period, bolls per plant, lint percentage and fiber fineness. Presence of non-additive genetic effects for days to squaring, flowering and days taken to 1 st boll opening were confirmed from the findings of 10 while the results shown by 16, 14 were different. They reported additive genetic effects for these three traits. 27 reported the involvement of both additive and non-additive effects in the traits like days to 1 st flower, days taken to 1 st boll opening and boll maturation period while studying a diallel cross. In case of bolls per plant 23, 24 reported non-additive genetic effects while additive effects were found in the studies of 2. For lint percentage non additive genetic effects were found by 17, 19. While opposite results were shown by 1. For fiber fineness non additive genetic effects were reported by 19 while findings of 23 depicted that fiber fineness is under the control of additive genetic effects. For traits like vertical and horizontal flowering interval, height of 1 st fruiting branch, mean maturity date, earliness index, boll weight, seed cotton yield, fiber length and fiber strength additive genetic effects were predominant. 16 also reported additive gene action for mean maturity date. Regarding earliness index and seed cotton yield contribution of additive and dominance effects were reported by 27. For node number for first fruiting branch and height of 1 st fruiting branch additive genetic effects appeared to be predominant in the studies of 18, 26. For boll weight additive genetic effects were found in the studies of 1, 21. While this result differs from those showed by 23. For seed cotton yield additive genetic effects were reported by 2 while 23, 19 showed that non-additive effects controlled the seed

9 cotton yield. For fiber length additive genetic effects were found in the studies of 19 while 17 showed that fiber length is controlled by non-additive gene action. For fiber strength, additive genetic components appeared to be predominant in the current study thus confirms the findings of 23, 22 while 19 that nonadditive effects control this character. Variation in the results with other researchers may be due to genotypic and environmental differences. The present results may provide a guide line to breeder while handling breeding material. It had been reported that the characters controlled by non additive gene action may have low heritability 15, suggesting that the segregating population are not amenable to selection pressure in early generations like F 2, as selection must be delayed till the genes are established in the breeding population. By contrast, variation in characters controlled by additive gene action might have high heritability 15, as these characters were controlled by the additive gene action so, plants having good characters would easily identified in F 2 population. For earliness traits genotypes CIM-496, MNH-552, BH-160, FH-160 and PB-899 proved good general combiners and among the testers the genotypes CP-15/2, LRA-5166 and COKER-310 proved good for most of the earliness traits. Number of days to squaring is an important indicator of earliness. Early maturity in cotton was determined by the faster squaring or flowering mode, more squaring or flowering sites on fruiting branches for this character, lines (PB-899, FH-1000 and BH-160) and testers (LRA-5166 and COKER- 310) proved good general combiners. It had been reported that parents having good GCA for a particular trait are expected to yield good hybrids and this behavior of the parents was found to be valid in present studies. e.g. BH-160 COKER-310, PB-899 LRA-5166, FH-1000 COKER-310 and FH-1000 LRA-5166 proved good hybrids for number of days to squaring, as they involve parents that have good general combining ability for the character. It is not always necessary that all the hybrids are produced from parents having high GCA sometimes; the parents with poor GCA may nick well to produce potential hybrids e.g. CIM-496 CP-15/2 and MNH-552 CP-15/2. The present case is supported by 7 in their studies. Days taken to open first flower were reliable and efficient parameters for predicting earliness of any variety 8 for the character lines (CIM-496, MNH-552 and BH-160) and testers (CP-15/2 and COKER- 310) proved good general combiners, so the hybrids i.e. CIM-496 CP-15/2, MNH-552 COKER-310, PB-899 COKER-310, FH-1000 CP-15/2, BH-160 COKER-310, and BH-160 LRA-5166 proved good hybrids for number of days to flowering, as they involve parents that have good general combining ability for the character. It is not always necessary that all the hybrids are produced from parents having high GCA; sometimes the parents with poor GCA may nick well to produce potential hybrids e.g. FH LRA-5166 and PB-899 LRA For vertical flowering interval it is stated that if flowering intervals were shortened by only one day, this character alone could shorten the growing season by more than one week 11, for this trait lines (BH-160 and MNH-552) and testers (CP-15/2 and LRA-5166) proved good general combiners, so yield good hybrids i.e. CIM-496 LRA-5166, FH-1000 LRA-5166, MNH-552 CP-15/2, BH-160 CP- 15/2, FH-1000 CP-15/2, BH-160 COKER-310, proved good hybrids for vertical flowering interval, as they involve parents that have good general combining ability for the character. PB-899 COKER-310 produced good combination though it involved a parent with poor GCA. For horizontal flowering interval, lines (CIM-496 and BH-160) and testers (COKER-310 and CP-15/2) proved good general combiners, so the hybrids produced by these parents were good e.g. PB-899 CP- 15/2, BH-160 LRA-5166, BH-160 COKER-310, CIM-496 LRA-5166, FH-1000 CP-15/2, MNH-

10 552 COKER-310, and MNH-552 CP-15/2. FH-1000 LRA-5166 also proved a good combination in spite of the involvement of apparent with poor GCA. Number of days for first boll opening is important character for measuring earliness. Early maturity in cotton is measured by the days required from flower to boll opening. For this character lines (CIM-496, FH-1000 and MNH-552) and testers (COKER-310 and LRA-5166) proved good general combiners. Hybrids i.e., BH-160 LRA-5166, MNH-552 COKER-310, FH-1000 CP-15/2, MNH-552 LRA-5166, CIM-496 COKER-310, BH-160 COKER-310 and FH-1000 COKER-310 proved good hybrids for number of days for first boll opening, as they involve parents that have good general combining ability for the character. For boll maturation period, lines (CIM-496 and MNH-552) and testers (LRA-5166 and CP-15/2) proved good general combiners. So parents having good general combining ability yield superior hybrids e.g. BH-160 LRA- 5166, PB-899 CP-15/2, MNH-552 COKER-310, FH-1000 CP-15/2, MNH-552 LRA-5166, CIM- 496 CP-15/2 and CIM-496 COKER-310. Node number for first fruiting branch is reliable indicator of earliness, Production of large proportion of the total crop at lower main stem nodes may also lead to earlier crop maturity through greater retention of fruits initiated early in the season and avoidances of extended boll filling periods from fruit initiated later in the growing season at upper main stem nodes 11.The lines (CIM-496, MNH-552 and PB-899) and testers (CP-15/2) proved good general combiners. So, good general combiners are expected to yield good hybrids e.g. PB-899 CP-15/2, MNH-552 LRA-5166, CIM-496 LRA-5166, BH-160 CP-15/2, FH-1000 CP-15/2, PB-899 LRA-5166 and MNH-552 COKER-310. The crosses like FH COKER-310 and BH-160 COKER-310 though involved parents having poor GCA but they displayed good results. For height of first fruiting branch, lines (MNH-552, PB-899 and BH-160) and testers (LRA- 5166) proved good general combiners. So, hybrids e.g. BH-160 LRA-5166, PB-899 CP-15/2, MNH- 552 LRA-5166, MNH-552 COKER-310 and PB-899 LRA-5166 proved good hybrids for height of first fruiting branch. The crosses that involved one inferior parent yet performed better are FH-1000 COKER-310 and FH-1000 CP-15/2. For mean maturity date, lines (CIM-496 and FH-1000) and testers (COKER-310 and CP-15/2) proved good general combiners. So, hybrids e.g. BH-160 COKER-310, MNH-552 CP-15/2, CIM-496 COKER-310, FH-1000 CP-15/2 and CIM-496 CP-15/2 proved good hybrids for mean maturity date. MNH-552 LRA-5166 and PB-899 LRA-5166 displayed good results in spite of the involvement of one of average GCA parents. For earliness index, lines (CIM-496 and FH-1000) and testers (COKER-310 and CP-15/2) proved good general combiners. So, hybrids e.g. FH-1000 CP-15/2, MNH-552 LRA-5166 and FH LRA-5166 proved good hybrids for earliness index, as they involve parents having good general combining ability. CIM-496 LRA-5166, PB-899 LRA-5166 and PB-899 COKER-310 also showed better results. Significant GCA and SCA effects were reported by 7, for boll weight, lines (CIM-496, MNH-552 and BH-160) and testers (CP-15/2) proved good general combiners. So, hybrids e.g. MNH-552 COKER-310 and FH-1000 LRA-5166 proved good hybrids for boll weight, as they involve parents that have good general combining ability for the character. For number of bolls per plant, lines (CIM-496 and BH-160) and testers (LRA-5166) performed well because of high GCA, so they produced good hybrids (CIM-496 CP-15/2, FH-1000 LRA-5166 and BH-160 CP-15/2). For seed cotton yield, lines (FH-1000, CIM-496 and BH-160) and testers (LRA-5166) performed thus produced good hybrids (FH LRA-5166, CIM-496 CP-15/2 and BH-160 CP-15/2), while some crosses performed well even they have not good parents e.g. MNH-552 COKER-310 and PB-899 COKER-310. Significant contribution of GCA than SCA in controlling seed cotton yield have also been found by 7.

11 For lint percentage, lines (CIM-496 and FH-1000) and testers (CP-15/2) performed well as they have high GCA, so they produced good hybrids (FH-1000 CP-15/2 and CIM-496 CP-15/2), while some crosses performed well even they have not good parents e.g. BH-160 LRA-5166 and BH- 160 COKER-310. For fiber length, lines (MNH-552 and FH-1000) and testers (CP-15/2 and COKER- 310) performed well because having high GCA, so they produced good hybrids (FH-1000 LRA-5166, MNH-552 COKER-310 and MNH-552 CP-15/2), while some crosses performed well even they involved parents having poor GCA e.g. CIM-496 LRA-5166 and PB-899 CP-15/2. For fiber strength, lines (MNH-552 and CIM-496) and testers (COKER-310 and CP-15/2) performed well because having high GCA, so they produced good hybrids (BH-160 CP-15/2,, MNH-552 COKER-310 and CIM-496 COKER-310), while some crosses performed well even without the involvement of parents having high GCA e.g. FH-1000 LRA For fiber fineness, lines (BH-160, FH-1000 and MNH-552) and testers (COKER-310 and CP-15/2) performed well because of high GCA, so they produced good hybrids (PB- 899 CP-15/2, MNH-552 CP-15/2 and FH-1000 LRA-5166), while some crosses provide fruitful results even without the involvement of parents having high GCA e.g. CIM-496 LRA Conclusion: The results obtained from present studies tell us about the breeding methods that should be adopted to make early maturing cotton varieties. Intensive selection in F 2 population should be done in characters showing additive effects, while characters showing non-additive effects hybrid production might be fruitful. Among lines CIM-496 and PB-899 showed good general combining ability effects while the tester CP-15/2 exhibited promising results regarding GCA. The hybrids that showed good specific combining ability effects includes CIM-496 CP-15/2 for days to squaring, days to flowering, number of bolls per plant and seed cotton yield, CIM-496 LRA-5166 for vertical flowering interval, PB-899 CP-15/2 for horizontal flowering interval, number of days taken to first boll opening and fiber fineness, BH-160 LRA-5166 for boll maturation period, MNH-552 LRA-5166 for node number for first fruiting branch, FH-1000 COKER-310 for height of first fruiting branch, BH-160 COKER-310 for mean maturity date and earliness index, BH-160 CP-15/2 for boll weight and fiber strength, FH LRA-5166 for seed cotton yield and fiber length, FH-1000 CP-15/2 for lint percentage should be used as a material for developing new early maturing cotton varieties. The hybrid FH-1000 LRA showed high SCA for all the traits except for lint percentage, while for most of the traits the cross CIM-496 CP-15/2 showed good SCA effects so the material obtained for these two crosses should be advanced for developing early maturing cotton varieties. References 1.Ahmad M and Azhar FM. Genetic mechanism controlling seed cotton yield and its components in F 1 and F 2 generation of G. hirsutum L. Int J Agri Bio., 1999; 1(4): Ahmad QK, Khan IA, Zubair M, et al, Inheritance of lint yield and quality characters in cotton. The Pak Cottons., 1997; 41(1-2): Ali MA, Abbas A, Younas M, et al. Genetic basis of some quantitative traits in upland cotton. Plant Omics., 2009; 2: Ali MA and Khan IA. Assessment of genetic variation and inheritance mode of some metric traits in cotton (Gossypium hirsutum L.) J Agric Soc Sci., 2007; 4: Anjum R, Soomro AR and Chang MA. Measurement of earliness in upland cotton. Pak J Biol Sci., 2001; 4(4): Anonymous. Annual Progress Report of Central Cotton Research Institute, Multan ; 2001Pp

12 7.Azhar FM, Hussain A and Shakeel A. Combining ability of plant characters related to earliness in Gossypium hirsutum L. J Agric & Soc Sci., 2007; 3(2): Babar SB, Soomro AR, Anjum R, et al. Two preliminary reliable indicators of earliness in cotton-ii. Asian J Plant Sci., 2002; 1: Baloch MJ and Baloch QB. Plant characters in relation to earliness in cotton (Gossypium hirsutum L.) In Proc Pak Acad Sci., 2004; 41: Basbag S, Ekinci R and Gencer O. Combining ability and heterosis for earliness characters in line tester population of Gossypium hirsutum L. Hereditas., 2007; 144: Bednarz, CW and Nichols RL. Phenological and morphological components of cotton crop maturity. Crop Sci., 2005; 45: Christidis BG and Harrison GJ. Cotton Growing Problems. McGraw Hill Book Co., Inc., New York Dutt Y, Wang XD, Zhu YG, et al. Breeding for high yield and fibre quality in coloured cotton. Plant Breeding., 2004; 123: El-Feki TA, Abdel-Gelil MA and Zeina AA. Diallel analysis of cotton hybrids (G. barbadence L.).1. Egyptian J Agri Res., 1998; 76(1): Falconer DS and Mackay. Introduction to Quantitative Genetics, 3rd Longman, London, UK Gomma AMA and Shaheen AMA. Earliness studies in inter-specific cotton crosses. Annals of Agric Sci. Cairo., 1995; 40(1): Hassan G Mahmood G Razaq A, et al. Combining ability in inter-varietal crosses of upland cotton. Sarhad J Agri., 2000; 16(4): Iqbal M, Chang MA, Jabbar A, et al. Inheritance of earliness and other characters in upland cotton. Online J Bio Sci., 2003; 3: Karademir C, Karademir E, Ekinci R, et al. Combining ability estimates and heterosis for yield and fiber quality of cotton in line x tester design. Not. Bot. Hort. Agro bot. Cluj., 2009; 37 (2) Kempthorne O. Introduction to Genetic Statistics. John Wiley and Sons, Inc. New York Khan MAJ, Khan MA and Lodhi TE. Genetic study of yield and yield related components in cotton (Gossypium hirsutum L.). JAPS., 1999; 9(1): Lukange EP, Labuschagne MT and Herselman L. Combining ability for yield and fibre characteristics in Tanzanian cotton germplasm. Euphytica., 2007; 161: Murtaza N, Qayyym MA and Khan MA. Estimation of genetic effects in upland cotton for fiber strength and staple length. Int J Agric Biol., 2004; 6(1): Neelima S, Reddy VC and Reddy AN. Combining ability studies for yield and yield components in American cotton (Gossypium hirsutum L.). Ann Agri Biol., 2004; Res 9(1): Panhwar GN, Soomro RA and Anjum R, et al. Predicting earliness in cotton during crop development stage-11. Asian J Pl Sci., 2002; 1: Rauf S, Shah KN and Afzal I. A genetic study of some earliness related characters in cotton (Gossypium hirsutum L.). Caderno de Pesquisa Ser Bio Santa Cruz do Sul., 2005; 17(1): Shakeel A, Farooq J, Ali MA, et al. Inheritance pattern of earliness in cotton (Gossypium hirsutum L.) Aust J Crop Sci., 2011; 5(10): Steel RGD and Torrie JH. Principles and procedures of statistics: A biometrical approach. 2nd Ed. 1997; Mcgraw hill book Co., Inc., New York.

13 Table-1a: Mean squares from analysis of variance for earliness related traits Source of DF Days to Days to Vertical Horizontal Days to Boll Node Height Mean Earliness variation squaring flowering flowering flowering 1 st boll maturity number of 1 st maturity index interval interval opening period for 1 st fruiting date fruiting branch branch Replications * * * Treatments * 6.79* 0.047* 0.211* 31.81* 12.70* 3.64* 25.14* 7.58* 37.77* Parents * 5.42* * * 41.7* Crosses * 6.13* * 22.64* 17.50* 2.97* * Parents vs * 25.59* * 342.6* * 168.6* 43.7* 306.5* crosses Lines * * 39.56* Testers Lines testers * * 0.126* * * Error Total

14 Table-1b: Mean squares from analysis of variance for yield and fiber related traits Source of variation DF Boll weight (g) Bolls per plant Seed cotton yield (g) Lint percentag e (%) Fiber length (mm) Fiber strength (tppsi) Fiber fineness (µg/inc h) Replications * 89.81* Treatments * * * 7.88* 3.23* 5.87* 0.254* Parents * * * 10.18* 5.91* 12.30* 0.312* Crosses * 55.22* * 7.25* * Parents vs crosses * * * Lines * 7.73* Testers * Lines testers * 54.42* * 6.05* * Error Total

15 Table- 2a: General combining ability estimate of 5 lines and 3 testers for earliness related traits Parents Days to Days to Vertical Horizontal Days to Boll Node Height Mean Earliness squaring flowering flowering flowering 1 st boll maturity number of 1 st maturity index interval interval opening period for 1 st fruiting date fruiting branch branch Lines PB * * 2.82* * -2.37* FH * * BH * * CIM * * -2.48* * 1.08* -1.38* MNH * -0.98* * * S.E. (GCA Lines) S.E. Testers COKER LRA * CP-15/2 1.36* * (GCA Testers)

16 Table- 2b: General combining ability estimate of 5 lines and 3 testers for yield and fiber related traits Parents Boll Bolls per Seed cotton Lint percentage Fiber Fiber strength weight (g) plant yield(g) (%) length(mm) (tppsi) Fiber fineness (µg/inch) Lines PB * * -1.07* 0.22* FH * * BH * * -0.28* CIM * * * MNH * 1.04* S.E. (GCA Lines) Testers COKER * LRA * 3.01* * * CP-15/ * 0.57* S.E. (GCA Testers)

17 Table-3a: Specific combining ability estimate of 15 hybrids for earliness related traits Hybrid Days to Days to combinations squaring flowering Vertical flowering interval Horizontal flowering interval Days to 1 st boll opening Boll maturity period Node number for 1 st fruiting branch Height of 1 st fruiting branch Mean maturity date Earliness index PB * * COKER-310 PB 899 LRA PB 899 CP * -0.25* -3.84* /2 FH * 0.15* COKER-310 FH * LRA 5166 FH 1000 CP /2 BH COKER-310 BH * LRA 5166 BH 160 CP * * /2 CIM COKER-310 CIM * LRA 5166 CIM 496 CP -2.84* -1.45* /2 MNH * COKER-310 MNH LRA 5166 MNH * 2.60* CP 15/2 S.E. (SCA)