Combining Ability Estimates for Yield and Fibre Quality Traits in Line X Tester Crosses of Upland Cotton , ( Gossypium hirsutum )

This study was to estimate the GCA of the parents and SCA considered for the development of high yielding and better quality cultivars. Eleven genotypes and 28 F1 hybrids obtained by crossing 4 lines and 7 testers in line X tester mating system were sown in randomized complete block design. L X T analysis revealed significant GCA and SCA effects for all the traits except earliness. Among the parents: MCU 12 for number of bolls per plant, boll weight, seed cotton yield per plant, F 1861 for seed cotton yield and number of bolls per plant, SOCC 17 for earliness, SURABHI for number of sympodia and TCH 1641 for ginning outturn and lint index with high GCA. Parent F 776 and F1861 were good combiners for fibre quality traits. The high yielding quality hybrids were deducted with significant SCA effects for seed cotton yield and fibre characteristics.


Introduction
Cotton (Gossypium hirsutum L.) is an important fibre crop and plays a vital role as a cash crop in commerce of many countries such as USA, China, India, Pakistan, Uzbekistan, Australia and Africa.Cotton crop is mainly cultivated for fibre.Development of new variety with high yield and fibre quality is the primary objective of all cotton breeders.The first step in successful breeding program is to select appropriate parents.Line x Tester analysis provides a systematic approach for detection of appropriate parents and crosses in terms of investigated traits.This method was applied to improve self and cross-pollinated plants (Kempthorne 1957).Previous studies showed that variation in seed cotton yield and its components were controlled by genes acting additively and non-additively.Shakeel et al.,(2001), Ahuja and Dhayal (2007) revealed that number of bolls, boll weight and seed cotton yield were influenced by the genes acting non-additively and in contrast studies of Khan and Idris (1995).Kumaresan et al. (1999) indicated that both additive and non-additive gene effects were important for controlling number of bolls and seed cotton yield.However, Lukange et al. (2007) revealed additive gene effects for fibre strength and microanire value and non-addidive gene action for fibre length.Non-additive gene action for fibre quality traits: fibre length, fibre strength and micronaire value have been reported by Baloch et al. (1997), Hassan et al. (1999 and2000), Ahuja and Dhayal (2007) and Preetha and Raveendran (2008).The purposes of this research were to estimate the GCA and SCA effects for seed cotton yield, its components and fibre quality traits among 4 genotypes taken as female, and 7 taken as male G. hirsutum lines and to determine appropriate parents and crosses for the investigated traits.

Plant materials
The materials used in the present study was developed by crossing four local cultivars, viz: MCU 5, MCU 12, SURABHI, and SVPR 2 with 7 diverse genetic accessions : F 776, F 1861, SOCC 11, SOCC 17, TCH 1641, TCH 1644and TCH 1646 all belonging to G. hirsutum.When the parental lines started to flower, these were crossed in line x tester fashion.Some of the buds of parents were also selfed.Maximum numbers of crosses were made to develop sufficient F 1 seed.

Field layout
The F 1 seed of 28 hybrids and parents were planted in the field during Kharif 2005-2006 crop season at Cotton Breeding Station Coimbatore, Tamil Nadu (India).Each entry was sown in three replications following randomized complete block design.Each genotype seed was sown in a 3 plot of 4.5 meter length adopting a spacing of 75 cm between rows and 30 cm between the plants in the row, so as to have 15 plants per row.

Data analysis
Data were recorded on middle five competitive plants for all the 17 characters viz., Days to first flowering, days to 50% flowering on whole plot basis, plant height (cm), number of sympodia per plant, number of bolls per plant, boll weight (g), number of seeds per boll, ginning outturn (%), lint index (g), seed index (g), seed cotton yield per plant (g), 2.5% span length (mm), fibre strength (g/tex), micronaire value (μg/inch), uniformity ratio and fibre elongation (%).Lint samples were submitted to Central Institute for Research on Cotton Technology unit at Coimbatore, Tamil Nadu (India) for analysis of fibre quality traits: 2.5% span length (mm), Micronaire value (μg/inch), fibre strength (g/tex) and fibre elongation (%).

Statistical Analysis
The mean values of the characters measured in 59 genotypes in each replication were analysed for Analysis of variance, estimation of Standard Error and Critical Difference by adopting the method suggested by Panse and Sukhatme (1964).Prior to estimation of combining ability effects, the data on 16 traits was subjected to path coefficient analysis suggested by Dewey and Lu (1959) to study direct contribution of different traits and nature of their relation to seed cotton yield.The Line x Tester analysis of combining ability was performed as suggested by Kempthorne (1957).

Results
Significant difference among parents and hybrids revealed presence of genetic diversity among them.From the parents versus hybrids components of variance, it was observed that significant heterosis (average) was exhibited by all the characters except days to first flowering and days to fifty per cent flowering (Table 1).Path coefficient analysis at genotypic level indicated that out of sixteen traits under study, six traits viz: boll weight, number of sympodia per plant, lint index, number of seeds per boll, uniformity ratio and micronaire value depicted direct effects in desirable directions on seed cotton yield (Table 2).The genotypic correlations of these traits with seed cotton yield were also positive for all of these characters and desirable negative for days to first flowering and micronaire value.Using the technological evolution of yarn developed from solely ring-based spinning to predominately rotor and air-jet spinning, need for intensification of fibre property profiles to suit the automated spinning systems.Nevertheless, successful rotor spinning requires high fibre strength for all yarn counts, along with fibre fineness for fine count yarns.The stable more productive air-jet spinning requires a minimum, but uniform fibre length, fibre fineness, and to a less extent strong fibre.On the differing, ring spinning requires a minimum fibre length, fibre strength, and to a lesser extent fibre fineness.Thus fibre length and fibre strength being indispensable traits though showing negative direct effect on seed cotton yield were not excluded for further analysis for combining ability.Seed cotton yield exhibited positive but non-significant association with fibre length and fibre strength.Its correlation with micronaire value, uniformity ratio and elongation percentage was non-significant and negative.Mean squares of genotypes, GCA and SCA for all the characters under study were significant except days to 50 per cent flowering indicating prevalence of genetic diversity among parents and F 1 hybrids.
The combining ability analysis gives useful information regarding selection of parents based on the performance of their hybrids and further it helps for the exploitation of heterosis.Among the parents, the best general combiner was line MCU 12 and testers F 1861 and SOCC 17 recorded significant gca effects for bolls per plant.Apart from this MCU 12 has recorded high gca for seed cotton yield, number of bolls per plant and while F 1861 exhibited high gca effects for number of bolls per plant and seed cotton yield.Therefore the line MCU 12 and tester F 1861 were identified as good source of favourable genes in improving yield characters.Further the study revealed that high and significant gca effects for seed cotton yield result from combined effect of yield component, number of bolls which is an concordance with results of Patel et al. (1992).Significant and positive gca effects were recorded for number of sympodia the line Surabhi presented in Table 3.For fibre quality characters MCU 5 and MCU12 showed high significant gca for 2.5 % span length and bundle strength.Similarly among the testers F776 recorded high gca for both fibre length and strength.In addition it also showed high gca for 2.5 per cent span length (F 776) as indicated in Table 3.The specific combining ability value of any cross was helpful in predicting the performance of the better parents.Out of the 28 hybrids, only three hybrids, MCU 12 x F 1861, SVPR 2 x F 776 and MCU 5 x TCH 1644 showed significantly negative sca effects for earliness.Beyond the 28 hybrids MCU5 x TCH 1641 for plant height and ginning outturn, MCU 12 x TCH 1641 for number of sympodia per plant, MCU 12 x SOCC 17 and MCU12 x F 1861 for number of bolls, Surabhi x F 1861 for boll weight per plant, Surabhi x SOCC 11 for number of seeds per boll, MCU 5 x TCH 1644 and MCU 12 x SOCC 11 for lint index, MUC 5x TCH 1646 for seed index were exhibited to significant high sca expression, presented in Table 4.The hybrid MCU 5 x SOCC11 for ginning outturn and MCU 5 x TCH 1646 for seed index had superior per se performance, with high sca effects.The hybrids can be exploited as basic material for breeding Specific combining ability effects of these crosses were related with general combining ability effects of their parents as they involved at least one parent with high or average GCA effects for particular traits.Similar results have been reported by Punitha et al.(1991), Khan and Idris (1995), Baloch et al.(1997), Hassan et al. (1999), Kalwar and Babar (1999), Kumaresan et al. (1999), Hassan et al. (2000), Shakeel et al. (2001) and Ahuja and Dhayal (2007).Mean values for characters of parents and F 1 hybrids are given in Table 6.The means of F 1 crosses were higher than those of parents in all the characters.In majority of cross combinations having significant SCA effects showed better mean performance (average performance over three replication of a cross for a trait) as reflected by positive association between them indicating that the cross combinations may be selected either on the basis of SCA or mean performance or in combination.Several workers found that hybrids superior with fibre quality traits were not good in seed cotton yield and vice-versa [Tuteja et al. (1995); Hassan et al. (1999); Jagtap (1994); Neelam Dheva et al. (2002)].In the present study, of the best three cross combinations: MCU 12 x F 1861, MCU 12 x SOCC 17 and MCU 12 x SOCC 11 exhibited high heterotic effect and per se performances for seed cotton yield per plant.Four hybrids recorded significant and positive sca effects for fibre elongation percentage, the hybrids being SVPR 2 x TCH 1641, Surabhi x TCH 1644, MCU 12 x SOCC 17 and MCU 5 x F 1861.Among these, SVPR 2 x TCH 1641 and MCU 12 x SOCC 17 had superior per se performance, significant standard heterosis with high sca effects for fibre elongation.For ginning outturn MCU 5 x TCH 1641 had superior per se performance, significant standard heterosis with high sca effects.These hybrids can be exploited as basic material for breeding purposes.

Discussion
The 11 parents and 28 hybrids used in this study varied significantly for each yield component and fibre quality parameter evaluated (Table 1, 3).These data indicated that the highest values of yield components and fibre quality parameters do not follow same pattern in every line i.e. the parent or the cross with high yield or its component traits did not necessarily had high fibre quality parameters.GCA variances were lower than SCA variances for all the characters as indicated by their lower ratios indicating predominance of non-additive gene action (dominant or epistasis) in the inheritance for all of these traits (Sprague and Tatum 1942).Studies of Shakeel et al. (2001) and Ahuja and Dhayal (2007) revealed that number of bolls, boll weight and seed cotton yield were influenced by the genes acting non-additively and in contrast studies of Khan and Idris (1995), and Kumaresan et al. (1999) indicated that both additive and nonadditive gene effects were important for controlling number of bolls and seed cotton yield.However, Lukange et al. (2007) revealed additive gene effects for fibre strength and microanire value and non-addidive gene action for fibre length.Non-additive gene action for fibre quality traits: fibre length, fibre strength and micronaire value have been reported by Baloch et al. (1997), Hassan et al. (1999 and2000), Ahuja and Dhayal (2007) and Preetha and Raveendran (2008).Predominance of non additive gene action for days to fifty per cent flowering, plant height, number of bolls per plant and boll weight was observed by Neelam Deva et al. (2002), number of sympodia per plant reported by Valarmathi and Jehangir, (1998), number of seed per boll, ginning outturn [Sandhu et al. (1993)], lint index, seed cotton yield [Patel et al. (1992); Ahuja and Dhayal (2007)].These results suggested that heterosis breeding was suitable for all the characters including fibre properties.The non-additive gene actions are also important for varietal adaptability.Amudha et al. (1997); Mandloi et al. (1998) and Modi et al. (1999) also observed superior per se performance with high SCA effects for ginning outturn.The results indicate the predominance of non-additive genetic variation in the inheritance of these characters, which was in accordance with results, was obtained by Krishna Rao (1998).The hybrid combinations, which were, have good sca and per se performance for seed cotton yield, indicated the possibility for simultaneous improvement of seed cotton yield and yield-attributed traits by exploring these hybrids.
Among the derived hybrids, five hybrids recorded significant and positive sca effects for uniformity ratio.The hybrid between Surabhi x TCH 1644 exhibited high sca for uniformity ratio.Six hybrids recorded significant and positive sca effects for bundle strength, with MCU 5 x SOCC 17 recording the highest value followed by Surabhi x F 776, MCU 5 x F 1861, MCU 12 x TCH 1644, MCU 12 x TCH 1641 and Surabhi x TCH 1646.Among these, the hybrid MCU 5 x SOCC 17 exhibited (good x poor general combiner) sca for bundle strength and MCU 12 x TCH 1644 (moderate x good general combiner) for micronaire were the other crosses with high per se performance and high sca effects for the characters mentioned (Table.5).The four cross combinations recorded significant and positive sca effects for fibre elongation percentage being SVPR 2 x TCH 1641, Surabhi x TCH 1644, MCU 12 x SOCC 17 and MCU 5 x F 1861.The results indicated the predominance of non-additive genetic variation in the inheritance of these characters.The presence of parallelism between per se and heterosis in present study suggest the possibility of direct exploitation of these hybrids for commercial exploitation.The study indicated the possibility of developing hybrids with high seed cotton yield and quality traits through heterosis breeding.