Heritability and correlation analysis in Bt and non-Bt cotton ( Gossypium hirsutum L . ) genotypes

The present research was carried out to analysis the heritability and correlation in 24 Bt and nonBt cotton genotypes for yield, yield related and fiber traits, including plant height (cm), first sympodial node number, first effective boll node number, sympodial branches plant, bolls plant, boll weight (g), seed index (g), micronaire value (μg/inch), staple length (mm), ginning outturn percentage and seed cotton yield plant (g). The results exhibited that genotypes differed significantly at P ≤0.01 for all the traits studied. It indicates that the significant genetic diversity among the genotypes for further evaluation. High heritability estimates in broad sense was found for most of the studied traits except 1 effective boll node number, which displayed moderate heritability estimates. High heritability values for majority of the traits suggested that the variation observed was mainly under genetic control and was less affected by environmental factors, referring the influence of additive gene action for most of the studied traits. Hence, the improvement of these traits can be made through direct phenotypic selection. Among the recorded traits, only four traits i.e. 1 effective boll node number, sympodial branches plant, bolls plant and ginning outturn percentage developed a significant and positive associations with seed cotton yield plant. Thus, selection for these traits will assist in selecting genotypes with greater seed cotton yield plant.


Introduction
Cotton (Gossypium hirsutum L.) belongs to the family Malvaceae, and is grown almost all over the world from the time immemorial.Cotton is mainly grown for fiber, which is the economic component and plays a vital role for uplifting the country's economy [1].In breeding population, the presence of enough magnitude of variability is more effective and important criteria for selection.Therefore, it is necessary to understand the presence of variability in a population to adopting most appropriate breeding technique for improvement of the various characters in cotton.To maintain the high productivity level of any crop, genetic variability offered in nature or created in the course of crop breeding is of immense significance.
During hybridization programs, genetic similarity within a crop species is readily barrier and main cause of genetic vulnerability.To create new genetic complexes, it is very necessary that genetic diversity should be available in cultivated and wild germplasm for higher yield, fiber and tolerance to various biotic and abiotic stresses [2].Correlation coefficient is one of the key statistical approaches that can assist to plant breeders in selection crop plants for higher yields.Therefore, knowledge of interrelationships between yield and its contributing factors will improve the effectiveness of breeding programs through the use of suitable selection indices [3].The current study was aimed to estimate heritability and determine correlations among various quantitative and qualitative traits in Bt and non-Bt cotton genotypes.

Analysis of variance
The results revealed that the mean squares (Table 1) of all the genotypes differed highly significantly at P ≤0.01 of probability level for all the studied traits, such as 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 , suggesting that studied materials proved its worth for further evaluation, especially for the improvement of yield and fiber traits in upcoming breeding programs.Almost similar results were also reported by several other workers, including Baloch

Mean performance
The data regarding mean performance of genotypes is given in

Correlation coefficients
Cotton seed yield is the resultant product of component character which is not under the direct control of any single gene.Thus, an improvement of component characters leads to a consequent improvement in the yield.Therefore, the understanding of the mechanism of association that is, cause and effect relationship provides the foundation for formulating suitable selection criteria for breeding program on the basis of yield components for achieving rational improvement of yield and its components [10].The estimates of correlation coefficients were worked out among 11 yield and fiber quality related characters with seed cotton yield plant -1 (Table 4).Of the total traits, three traits, namely1 st effective boll node number (r=0.240*), sympodial branches plant -1 (r=0.498**) and bolls plant -1 (r=0.895**) had significant positive association with seed cotton yield plant -1 .Hence, selection for these traits will help in selecting genotypes with higher seed cotton yield plant -1 .Similar results of positive association between yield and fiber quality traits were reported by Ashokkumar and Ravikesavan [11].The inter correlation among the important component traits is also imperative in order to decide which trait to be given due weightage in exercising selection.The inter correlation among the quantitative and qualitative traits viz, plant height with sympodial branches plant -1 (r=0.373**) and bolls plant -1 (r=0.252*); 1 st sympodial node number with micronaire value (r=0.282**); 1 st effective boll node number with bolls palnt -1 (r=0.237*) and staple length (r=0.203*);sympodial branches plant -1 with bolls plant -1 (r=0.440**) and ginning outtern percentage with micronaire value (r=0.717**) were positive and significant, indicating the possibility of simultaneous improvement of these traits.Similar results were reported by Kalpande et al. [12].However, among the yield contributing traits, it is interesting to note that bolls plant -1 developed significant negative inter correlation with ginning outtern percentage (r=-0.295**)and micronaire value (r=-0.241*),suggesting that great care should be taken while selection is being carried out for bolls plant - 1 .