genetic studies of yield traits in cotton (gossypium hirsutum l.)

Genetic studies of yield traits in cotton

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GENETIC STUDIES OF YIELD TRAITS IN COTTON (GOSSYPIUM HIRSUTUM L.) Tariq Manzoor Khan* and M. Uzair Qasim**

ABSTRACT This study was carried out in the Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan during the year 2009-10. The research project comprised five parental genotypes (COKER-4601, 199F, MNH129, MS-39 and CRIS-134) and their 20 crosses in a diallel set. F1 seed was sown in the field during the cropping season June, 2009 in randomized complete block design with three replications. Data regarding plant height, number of monopodial branches, number of sympodial branches, number of bolls per plant, boll weight and seed cotton yield were collected and subjected to the analysis of variance to study genotype differences for these characters. The characters were further tested for fitness to the additive dominance model for genetic analysis. The results manifested that additive type of gene action with partial dominance was involved in the inheritance of all above traits except for monopodial branches for which over-dominance type of gene action was observed. Non-allelic interaction was found to be absent. KEYWORDS: Gossypium hirsutum; crossbreeding; F1 hybrid; agronomic characters; Pakistan.

INTRODUCTION Cotton (Gossypium hirsutum L.) is an important cash crop of Pakistan as well as of the world. The country earns a sustainable amount of foreign exchange through export of raw cotton and its products. It accounts for 7.3 percent of value added in agriculture and about 1.6 percent in GDP of the country (2). This crop was sown on extensive area of 2.82 million hectares during 200809 with a production of 11.8 million bales (2). Cotton crop provides basic raw material to local textile industry as per its requirement of 15 million bales. In addition cotton seed is a big source of edible oil. Due to expansion in textile industry the cotton demand is increasing day by day which can be met either by increasing area under cultivation or by improving per hectare yield. The most important factor in the process of crop production has always been a *Assistant Professor, **M.Sc. Student, Department of Plant Breeding & Genetics, University of Agriculture, Faisalabad, Pakistan.

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T. M. Khan and M. U. Qasim

good variety in any crop. Cotton breeders managed to produce high yielding varieties through various genetic manipulations and breeding approaches and consequently, a significant progress was achieved in this connection (2). As the yield improvement in agricultural crops is a continuous process, breeders are busy all the time in adopting new techniques and approaches for improving cotton production based on the information generated through genetic analyses of the varieties and/or species. The diallel technique (6, 7) is a useful tool to obtain precise information about the type of gene action involved in the expression of various plant characters. Some earlier scientists (1) conducted a 5x5 complete diallel analysis and observed additive type of gene action for plant height and sympodial branches per plant. Bertini et al. (4) observed dominance effects for number of bolls, boll weight and fibre yield. Mingbaoa et al. (10) studied 16 lines as male and top crossed with three elite cultivars. They noted that boll weight had the largest additive proportion while boll number had the least additive proportion. They further observed the largest and least dominant proportion for lint yield and boll weight, respectively (4). Eight genetically diverse genotypes of desi cotton were studied by Mukhtar et al. (11) for 11 economical characters using diallel crossing system. The estimates revealed that additive and non-additive type of gene action were involved in the expression of all characters except the number of monopodial branches per plant for which only additive type of gene action was involved. Saravanan et al. (15) and Soomro et al. (18) studied diallel set of crosses of some parents of cotton for genetic effects on different traits. The additive type of gene action was seen for boll weight. However, plant height, number of bolls per plant and seed cotton yield per plant revealed effects with over dominance type of gene action. Shakeel et al. (16) conducted 5x5 diallel cross experiment to obtain genetic information on yield and yield components. Vr/Wr graph revealed that over dominance type of gene action was operative for number of bolls per plant and seed cotton yield while additive type of gene action with partial dominance for boll weight was observed. The present research was conducted to obtain the genetic information for some economic traits of cotton plant by using diallel technique. The information thus generated may help the breeders to launch a successful breeding programme for cotton. MATERIALS AND METHODS This study was carried out in glasshouse and experimental fields of Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Pakistan during the year 2009-10. Five parental genotypes J. Agric. Res., 2012, 50(1)


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(COKER-4601, 199F, MNH-129, MS-39 and CRIS-134) and their 20 crosses were studied in a diallel set. The crossed seed was sown in randomized complete block design with three replications. Each of 25 entries was planted in a single row having 30 cm plant to plant and 75 cm row to row spacing in each replication. The data were collected for plant height, number of monopodial branches, number of sympodial branches, number of bolls, boll weight and seed cotton yield. The data were subjected to the analysis of variance (ANOVA) following Steel et al. (17) to study genotype differences. The data were further tested for fitness to the additive dominance model for genetic analysis (6, 7). RESULTS AND DISCUSSION Analysis of variance revealed significant differences among the parents and their F1 progenies for all characters (Table 1). Table 1.

Analysis of variance for some yield traits of cotton in 5 × 5 diallel cross.

Characters Replications (df=2) ns Plant height 17.65 ns No. of monopodial branches 0.093 ns No. of sympodial branches 0.813 ns No. of bolls per plant 5.883 ns Boll weight 0.030 ns Seed cotton yield 120.725 NS = Non-significant, **Significant at P = 0.01

Mean squares Genotypes (df=24) 1804.16** 7.83** 117.48** 104.2** ns 0.87 926.67**

Error (df=48) 19.54 0.927 9.036 5.340 0.066 89.760

Plant height The mode of gene action was endorsed by the position of regression line in Vr/Wr graph (Fig. 1). As regression line intercepts Wr axis above the point of origin, it showed that additive genes with partial dominance were found controlling the inheritance of plant height. Absence of epistasis was seen as the regression line did not deviate significantly from the unit slope. The distribution of array points on the regression line suggests that variety MNH129 being nearest to the point of origin, carried maximum dominant genes while the variety MS-39 possessed maximum recessive genes for plant height as it is located away from the point of origin in Vr/Wr graph. The results seemed to be compatible with some earlier findings (1, 4, 9, 11, 18, 19). J. Agric. Res., 2012, 50(1)

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Number of monopodial branches The Vr/Wr graph (Fig 2) revealed that number of monopodial branches is governed by over-dominance type of gene action as the regression line intercepted Wr axis below the origin. Epistasis was absent as the regression line did not deviate significantly from a unit slope. The results are in line with the findings of earlier scientists (1) who reported over-dominance type of gene action in phenotypic manifestation of this character. Number of sympodial branches The data (Fig.3) indicated that regression line intercepted the Wr-axis above the origin revealing that additive gene action with partial dominance was involved in the inheritance of sympodial branches. The regression line did not deviate significantly from a unit slope thereby suggesting the absence of non-allelic interaction. Some earlier scientists (1, 9, 13) also observed similar results for this trait. The distribution of array points on regression line revealed that variety CRIS-134 had maximum dominant genes being closest to the origin whereas variety COKER-4601 had maximum recessive genes being farthest from the point of origin.

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Number of bolls The data (Fig. 4) revealed that regression line intercepted Wr- axis above the origin indicating additive gene action with partial dominance for number of bolls. As the regression line did not deviate from unit slope, it confirmed the absence of epistasis. Additive type of gene action, as observed in the present studies, was also seen by some earlier scientists (3,12, 15, 16). The array points distribution on regression line indicated that variety CRIS-134 possessed maximum dominant genes being closest to the origin whereas variety 199F had maximum recessive genes being farthest from the point of origin. Boll weight Additive type of gene action was also observed for boll weight, as the regression line intercept Wr axis above the origin(Fig. 5). Some scientists (3, 8, 12, ) had found similar type of gene action for boll weight. The variety MS-39 possessed maximum dominant genes as it lies nearest to the point of origin whereas variety 199F carried maximum recessive genes for boll weight as being located far away from the point of origin (Fig. 5).

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Seed cotton yield The graphic representation (Fig. 6) revealed that regression line intercepted Wr-axis above the origin revealing additive gene action with partial dominance in seed cotton yield. Epistasis was found to be absent as the regression line did not deviate significantly from unit slope. These findings are similar to those of earlier researchers (11). From the distribution of array points on the regression line (Fig.6) it is observed that CRIS-134 possessed maximum dominant genes while variety MS-39 had maximum recessive genes being nearest and at distal position from the origin, respectively. CONCLUSION The study concludes that additive type of gene action with partial dominance was involved in the phenotypic expression for most of the plant traits (plant height, number of sympodial branches, number of bolls, boll weight and seed cotton yield) except monopodial branches in which over-dominance type of gene action was observed. The characters under study could be improved through simple selection according to the results observed. However, in case of monopodial branches one must consider hybrid development to improve this trait as it was controlled by overdominance gene action.

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The distribution of array points along the regression line for different plant traits indicated the existence of genetic variation in plant material. Thus variation could be exploited through appropriate breeding programme. Epistasis was found absent which may facilitate the application of single plant selection and recurrent selection for the improvement of these characters. The presence of additive genetic effects for characters may be helpful to cotton breeders. It reveals a good index of heritability and is transmitted from parents to offsprings. REFERENCES 1. 2. 3.

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