Genetic studies in upland cotton ( Gossypium hirsutum L . ) for earliness and yield contributing traits

The current experiment was conducted to evaluate the genetics for earliness and yield traits in upland cotton (Gossypium hirsutum L.) during Kharif season 2013 at Cotton Section, Agriculture Research Institute, Tandojam. The experiment was laid out in a randomized complete block design with three replications. The experiment consisted of fifteen genotypes in which ten F1 were developed from five parents crossed in a 5 x 5 diallel matting design for days to 1 flower, bolls formed at 90 days after planting, bolls opened at 90 days after planting, plant height (cm), sympodial branches plant, bolls plant, boll weight (g) and seed cotton yield plant (g). The genotypes were significantly different (P≤0.05) for days to 1 flower, bolls formed at 90 days after planting, bolls opened at 90 days after planting, plant height, sympodial branches plant, bolls plant and seed cotton yield plant. Among the genotypes, Sindh-1, CRIS-134 and Shahbaz were best general combiners for days to 1 flower, bolls formed at 90 days after planting, bolls opened at 90 days after planting, plant height, sympodial branches plant, bolls plant, boll weight and seed cotton yield plant. The F1 hybrids Sadori x Sindh-1, Shabaz x Haridost, Sadori x CIM-496 were best specific combiners for all the characters studied. The F1 hybrids Shahbaz x Sindh-1, Sadori x Sindh-1, Sadori x Haridost and Sadori x CIM-496 gave higher heterotic effects for all the studied traits.


Introduction
Cotton occupies a unique position in Pakistan's agrarian economy.Efforts on various aspects of the crop have been under way to increase overall production of the country.Cotton is principal component of Pakistan's economy owing to its 69% share in foreign exchange earning, 7.5% value addition in agriculture and 1.6% in GDP.It contributes about 78% in domestic oil production.It is a powerful source for our economic growth because it plays an efficient role in enhancing the national economy by earning a huge share of the total foreign exchange.It enhances textile exports of cotton with made items like raw cotton, cotton yarn, bed wear, towels, cotton cloths and synthetic fabrics knit wear and readymade garments to foreign countries and embrace more than $7.3 billion to the national economy which is around two thirds of the country's export earnings [1].Cotton breeders hence are very keen in determining the genetic potential of their inbred parents in hybrid combinations for two reasons.First is that, inbred parents be identified which form good individuals in specific combinations, which is commonly referred as specific combining ability (SCA) of the inbred parents.Second purpose is, to locate those inbred lines which perform very well when crossed with a series of other inbred parents referred as general combining ability (GCA) of the parents.Thus, former types of inbreds are useful for hybrid cotton development, whereas later types are desirable for hybridization and selection from segregation populations.The primary objectives of this study were to determine the genetic potential in upland cotton cultivars, such information can usefully be subjugated in articulating efficient selection program for synthesis and development of new cotton genotypes with improved traits for earliness and seed cotton yield.

Results and discussion
The study was conducted during Kharif season of 2013 at Cotton Section, Agriculture Research Institute, Tandojam in randomized complete block design with three replications.In context to evaluate genetics for earliness and yield related traits in upland cotton (Gossypium hirsutum L.).The experiment consisted of fifteen genotypes in which five were parents and the rest were F1 hybrids in a 5 x 5 diallel matting design for days to 1 st flower, bolls formed at 90 days after planting, bolls opened at 90 days after planting, plant height (cm), sympodial branches plant 1 , bolls plant 1 , boll weight (g) and seed cotton yield plant 1 (g).The obtained mean squares from analysis of variances exhibited highly significant differences (P≤0.05) for all the studied traits among the assessed genotypes except that of boll weight, which was nonsignificant (Table 1).This reveals that examined genetic materials have value to be used in more breeding programs for the improvement of upland cotton in respect to fiber and yield.Kaleri et al. [2] also reported that a set Bt and non-Bt cotton genotypes differed highly significantly at P ≤0.01 of probability level for plant height, 1 st sympodial node number, 1 st effective boll node number, sympodial branches plant -1 , bolls plant -1 , boll weight, seed index, micronaire value, staple length, ginning outturn percentage and seed cotton yield plant -1 .

Conclusion
All the genotypes were highly significant for most of the traits, however, boll weight was non-significant.Among the genotypes Sindh-1 and Shahbaz were best combiners for days to 1 st flower, bolls formed at 90 days after planting, bolls opened at 90 days after planting, plant height, sympodial branches plant 1 , bolls plant 1 , boll weight and seed cotton yield plant 1 .Among the F1 hybrids the crosses Sadori x Sindh-

Table 1 . Mean squares from analysis of variance for various quantitative traits in upland cotton
[3]ilarly, Abro et al.[3]showed that the variety Sadori proved to be best general combiner for plant height, number of bolls plant -1 and seed cotton yield.

Table 4 . Heterotic effects for various traits in upland cotton genotypes
H= Mid-parent heterosis; HB= Better parent heterosis

Table 5 . Heterotic effects for various traits in upland cotton genotypes
H= Mid-parent heterosis; HB= Better parent heterosis 1, Shabaz x Hari dost, Sadori x CIM-496 were best specific combiners for all the characters studied.The F1 hybrids Shahbaz x Sindh-1, Sadori x Sindh-1, Sadori x Hari dost and Sadori x CIM-496 recorded higher heterotic effects for all the traits.Authors' contributions Conceived and designed the experiments: SN Mari, Performed the experiments: SH Kaleri & AA Kaleri, Analyzed the data: AW Baloch & AA Kaleri, Contributed reagents/