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Genetic Retrospect of Seedcotton Yield and its CompComponents from a 6-Parent Gossypium hirsutum Diallel Cross Under Water Stress Conditions.

Byline: Munaiza Baloch Bashir Ahmad Ansari Moula Bux Kumbhar and Muhammad Ibrahim Keerio

Abstract: A six-by-six complete F1 Gossypium hirsutum L. diallel cross of three pre-screened drought tolerant and three drought susceptible varieties (CRIS-134 CRIS-342 SINDH-1 NIAB-78 SADORI and BH-160) was evaluated for genetic parameters during 2009 at Sindh Agriculture University farm Tandojam. The characters studied were number of bolls per plant sympodial branches per plant seedcotton yield per plant and lintcotton yield per plant. The objective of such study was to assess the effect of irrigation stress on the genetic inheritance pattern of above quantitative traits as to how far the genetic parameters are affected due to irrigation stress in the F1 diallel generation. Irrigation treatments were four; normal seven irrigations schedule five irrigations four irrigations (medium stress) and three irrigations up to 150 days of crop maturity (stress conditions). CRIS-134 in seven Sadori in five and CRIS-342 in four and three irrigations treatments were the most recessive parents contributing increasing boll number into their progenies while BH-160 in seven CRIS-342 in five and Sindh-1 in four and three irrigations treatments proved to be the most dominant parents responsible for contributing decreased boll number per plant into their progenies. Seedcotton per plant was partial dominant in seven irrigations treatment while it inherited as an overdominant trait in five four and three irrigations respectively. BH-160 was the most recessive of all with increased sympodia contributing attributes in seven and four irrigations whereas Niab-78 in five and CRIS-342 in stress were the most recessive parents. Sindh-1 was the most dominant parent in seven five and three irrigation treatments while CRIS-342 in four irrigations yielded decreased sympodia contributing attributes into their progenies. Sindh-1 in seven BH-160 in five and three and CRIS-342 in four irrigations treatments proved to be the most recessive parents with increasing seedcotton yield attributes while CRIS-342 in seven and five and

Sindh-1 in four and three irrigations were the most dominant parents contributing decreased seedcotton yield into their progenies. Inheritance trend of lintcotton per plant was similar to that of seedcotton yield per plant.

Keywords: Genetic retrospect Gossypium hirsutum diallel cross irrigation stress.

INTRODUCTION

Economically quite a number of species experience variable soil-water contents depending on irrigation rainfall leaf area transpiration and evaporation index. Thus during their life cycle all crops experience drought of various intensities at one time or the other causing yield reduction. Drought induces a wide range of plant responses including stomatal closure changes in gene expression accumulation of abscisic acid (ABA) production of osmotically active compounds and the synthesis of protective proteins that scavenge oxygen radicals or act as molecular chaperones [1]. According to Quisenberry [2] drought resistance is the ability of a genotype within a species to be relatively more productive than others under moisture deficit. Levitt [3] divided drought resistance into drought avoidance and drought tolerance. Short duration growth constitutes an important attribute of drought escape with respect to relative yield advantage of early genotypes under prevailing/available water conditions 4]. Dehydration avoidance is also synonymously used for drought tolerance enabling higher 'hydration' level under soil or atmospheric water stress. The basic concept of dehydration avoidance is in fact retaining a high level of tissue 'hydration' inspite of stress environment. In that case plant's various physiological biological and metabolic processes involved in growth and yield are not internally expressed to stress or are protected from stress.

Crop improvement for drought tolerance through integration of adaptive traits is a promising option. Significant progress in recent years has led to the identification of several traits that have relevance in improving drought tolerance as well as development of suitable high throughout phenotyping strategies. For a comprehensive improvement in drought tolerance several traits need to be introgressed into a single elite genetic background. The emphasis here is to identify relevant traits and adopt conventional and /or molecular approaches to introgress them into an elite background with higher yield potential. Plant breeders and plant physiologists are of the opinion that genotypes well adapted and higher yielding in drought areas can be bred and managed more effectively and efficiently if their attributes that confer drought resistance could properly be identified and used as selection criteria in objectively defined breeding programs [5-8]. Numerous studies have consensus that physiological and metabolic changes in plants are caused by water stress [9-10]. Important of these changes are suppression of photosynthesis and deregulated accumulation of growth hormones consequently affecting final crop yield [9]. Thus varietal selection plays an important role in water use efficiency for higher cotton production. Improved production package technologies and scheduling methodology have promoted productivity and water use efficiency. The genetic yield potential of today's cotton plant in our country is at least 5 to 10 times the average yields that we attain each year. The primary cause of potential yield reductions is unfavorable environment haphazard and irregular application of package of production technology and ill-management of irrigation resources.

The diallel cross among selected parents can provide information on the genetic variances in a population derived by random mating of these parents. Since last three decades the diallel cross analysis has received considerable rapidity in most of the plant breeding programs because it fulfills specific needs of the plant breeders. The analysis provides a systemic approach for detecting parents and crosses superior for the traits under investigation. In addition it helps plant breeders to choose most efficient method of selection on the basis of estimates of various genetic parameters. Therefore systematic and successful hybridization program for yield improvement demands an understanding of the genetic architecture of yield and yield components to be bred [11] and requires information on (a) inheritance of yield and its morpho- physiological components (b) the nature of relationship between yield and these components and (c) the efficacy of such genetic inheritance patterns in the selection process. The purpose of the present research endeavors was firstly to identify the available cotton germplasm for drought tolerance in different irrigation regimes as against normal/recommended irrigation dose; and secondly to obtain information regarding the extent of variation of genetic parameters of these identified drought tolerant and susceptible varieties. In addition the present investigations were extended to identify the hybrids and parents possessing superior dominant gene combinations for drought tolerance for further utilization by cotton breeders while embarking upon any defined cotton breeding strategy. MATERIALS AND METHODS

Six pre-screened cotton (Gossypium hirsutum L.) varieties for drought resistance [12]; CRIS-134 CRIS- 342 Sindh-1 as drought tolerant and NIAB-78 SADORI and BH-160 as drought susceptible were intercrossed and complete F1 diallel coss created. All 36 entries (15 one-way crosses + 15 reciprocals + 6 parents) were sown as F1 diallel cross during 2009 in four-replicated Randomized Complete Block Design. All other cultural and agronomic practices were performed as per the need of the crop and experimental design. Three seeds were dibbled per hill spaced at one foot and the rows were distanced at 2.5 feet apart. Later one healthy plant was left per dibble. Three rows each 15 feet long were provided to each entry per irrigation treatment per replication. Irrigation treatments were four that is three irrigations (i.e. 55 95 and 125 days after planting); four irrigations (i.e. 50 70 90 and 110 days after planting); five irrigations (i.e. 40 60 80100 and 120 days after planting) and seven irrigations (normal or control) at 35 50 65 80 95 110 and 125 days after planting. At maturity ten consecutive plants were randomly selected per entry per replication per irrigation treatment and treated as index plants for recording observations on number of bolls per plant number of sympodia per plant seedcotton yield per plant and lintcotton yield per plant. Quantitative genetic analysis of this diallel experiment followed the procedures of Hayman Jinks and Aksel and Johnson [11 13-14]. Before conducting the diallel analysis the pre-requisite conditions of meeting five assumptions of diallel cross must be satisfied [11]. Here we would explain how our experimental material of 6x6 Gossypium hirsutum complete F1 diallel cross of selected drought susceptible and tolerant varieties satisfied these assumptions.

The condition of "homozygous parents" in the present studies was satisfied by selfing individual parental lines before they were used in hybridization program [12]. The condition of normal diploid segregation in the present case may be met by explaining that though cotton is an amphidiploid (allotetraploid) of A and D genomes [15] it has established itself as genetically stable over the years and behaves as normal diploid in subsequent generations [16]. The progenitor A and D genomes though differ enough in the resulting allotetraploid (2n=4x) yet they facilitate appropriate pairing of each set of chromosomes at meiosis as in normal diploid species [17]. Thus it has been made clear that many genes in Gossypium are inherited in functionally diploid manner. According to Kearsey and Pooni [18] quantitative genetic analysis in such organisms can be performed using standard methods considering normally segregating diploids. No reciprocal

differences" were checked after Hayman's [19] procedure of analysis of variance of diallel tables where significance of the component c' indicates failure of this hypothesis. The remaining three assumptions of no multiple allelism' independent action of non-allelic genes' and uncorrelated gene distribution' were checked by analysis of variance of Wr - Vr values for arrays of each diallel table. Heterogeneity of Wr - Vr variances will reveal non validity of these assumptions. In the present case the 't' value for Wr-Vr mean squares (Tables 2 to 5) were non-significant for all the characters and therefore the assumptions are satisfied.

After satisfying the validity of assumptions the quantitative genetic analysis yielded components of genetic variation (D H1 H2 F and h2) and second degree statistics (variances and covariances) parameters [V0L0 V0L1 V1L1 W0L01 and (ML1-ML0)2] from which the following genetic ratios and parameters were determined: (a) Average degree of dominance (H1/D)1/2. If the value of this ratio is zero there is no dominance; if it is greater than zero but less than 1 there is partial dominance and if it is greater than 1 it denotes over-dominance. (b) The ratio of dominant and recessive genes in the parents estimated as [(4DH )1/2 + 1 F] / [(4DH1)1/2 - F]. If this ratio is 1 the dominant and recessive genes in the parents are in equal proportion; if it is less than 1 it indicates an excess of recessive genes; but if it is greater than 1 an excess of dominant genes is indicated. (c) The number of groups of genes which control the character and exhibit

dominance is given by [h2/H2] and (d) the proportion of genes with positive and negative effects in the parents is estimated as [H2/4H1]. If the positive and negative alleles are symmetrically distributed this ratio equals to 0.25. Ratio less than 0.25 indicates preponderance of negative effects and greater than 0.25 excess of positive allele effects.

RESULTS AND DISCUSSION

The assumption of no reciprocal differences' as satisfied through analysis of variance of diallel table [19] is shown in Table 1. In this analysis of variance component a' tests the significance of additive gene effects and b' the dominance gene effects while b1' explains the mean deviation of hybrids from their mid- parent values. The dominance deviations if predominantly in one direction will result in significant b1' in the analysis of variance. Component b2' indicates the extent to which the mean dominance of deviations within a given array of diallel table differs from those of other arrays. Therefore significance of b2' in the analysis of variance will imply that some of the parents contain excess of dominant alleles controlling the particular character. Component b3' tests the portion of dominance deviations attributable to individual particular hybrid. The differences between reciprocal crosses are assessed by the significance of component

c' and the maternal effects are reflected by component d'. In the present case additive gene effects components in normal seven irrigations treatment was significant for all the characters implying the importance of additive gene effects and general combining ability of the parents. Component b' was also significant for all the four characters indicating that the dominance gene effects were important explaining additive x nonadditive and nonadditive x nonadditive gene effects interaction for these characters. Partitioning b' component of variation into b ' b ' and b3' components dominance effects get also partitioned into direction of dominance dominance deviations attributed to the parental arrays and dominance deviations ascribable to the individual hybrids. Accordingly b1' was highly significant (Pless than 0.01) for all the four characters implying that the dominance was unidirectional. Component b1 was nonsignificant for number of bolls per plant and

sympodia per plant only in five irrigations treatment signifying that the selection for these characters would not yield fruitful results. Component b2' was highly significant (Pless than 0.01) indicating that these dominance deviations are attributed to parental arrays and b3' was highly significant (Pless than 0.01) also implying that the dominance was caused by the hybrid combinations in other words due to divergent heterozygosity of the hybrids. Component 'c' was non-significant in seven and four irrigations treatments but highly significant in other treatments. Due to significant component c' the assumption of no differences between the reciprocal crosses' gets non-validated in the diallel analysis. This non-validity is removed by plugging in the common mean of a cross and its reciprocal in the off-diagonal cells of the diallel matrix. Component d' was highly significant for bolls per plant seedcotton yield per plant and lintcotton yield per plant. These maternal

effects not ascribed to component c' would not be considered in the diallel analysis especially when the common mean of the cross and its reciprocal has been plugged in the diallel matrix. These diallel tables were constructed by putting the common mean of a hybrid and it's reciprocal irrespective of the fact that whether the reciprocal differences were significant or not (Tables 2 to 5) and then analysis carried out. These tables have been supplemented by variances and covariances and other second degree statistics parameters from which the genetic components of variation were calculated. These components of genetic variation are also given in these diallel tables individually for each character. From these components of genetic variation genetic parameters were calculated which provided the basis for interpreting the genetic retrospect and inheritance pattern of a particular character and thus interpreted accordingly.

Genetic parameters are also given in these diallel tables. Inheritance of Bolls Per Plant Number of bolls per plant under normal seven irrigation treatment (Table 2) was inherited as an over dominant trait because the average degree of dominance parameter [H1AD] measured 1.033. The proportion of dominant and recessive genes in the parents [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was 0.509 indicating that parents contained preponderantly recessive genes in them. The proportion of negative and positive allele effects in the parents [H2A4H1] was 0.219 indicating that negative allele affects excessively distributed in the parents were responsible for contributing decreased boll number attributes into their progenies through their recessive genes. The number of groups of genes controlling dominance loci in the

Table 1: Mean squares from the analysis of variance of diallel table for validity test of 6x6 F1 complete cotton diallel

###cross under four irrigation regimes during 2009 for four characters at Sindh Agriculture University farm

###Tandojam

###Source of###D.F.###Number###Sympodial###Seedcotton###Lintcotton###Number of###Sympodial###Seedcotton###Lintcotton

###variation###of bolls###branches###yield per###yield per###bolls per###branches###yield per###yield per

###per plant###per plant###plant###plant###plant###per plant###plant###plant

###Reps.###3###1.55###1.76###3.52###0.34###7.05###0.50###2.81###0.26

###a###5###128.41###141.08###2672.10###259.04###253.13###130.40###3807.90###369.55

###b###15###31.01###8.42###247.18###24.00###40.18###7.41###599.16###57.99

###b1###1###22.40###3.32###964.43###93.51###1.18 ns###0.36 ns###1874.37###181.84

###b2###5###13.83###8.42###116.54###11.29###18.77###5.68###378.35###36.90

###b3###9###41.51###8.98###240.07###23.34###54.41###9.16###580.15###55.95

###c###5###1.19 ns###0.22 ns###3.73 ns###0.36 ns###1.89###7.26###3.14 ns###0.32 ns

###d###10###4.60###0.35 ns###6.01###0.58###2.61###3.32###7.09###0.68

###Error###105###0.69###0.35###1.82###0.18###0.38###0.48###1.74###0.17

###Reps.###3###5.60###1.46###95.06###9.30###1.39###20.40###24.12###1.93

###a###5###510.31###129.34###6887.30###667.53###446.05###102.94###5043.05###486.17

###b###15###233.81###8.06###2909.16###281.74###182.08###7.81###2403.87###230.44

###b1###1###1003.05###3.84###19223.71###1859.65###1195.45###12.35###20527.07###1939.27

###b2###5###426.72###12.29###4160.08###403.14###249.20###8.27###2528.54###247.58

###b3###9###41.17###6.18###401.48###38.98###32.19###7.00###320.91###31.058

###c###5###10.32ns###0.36ns###28.27ns###2.69ns###6.93###1.36###82.34###8.03

###d###10###3.01ns###0.61ns###34.07ns###3.29ns###1.97ns###0.41###14.95ns###1.44ns

###Error###105###4.83###0.63###43.78###4.24###1.05###0.41###9.44###0.96

parents [h2AH2] was 0.20 implying that at least one group of genes is operative in governing/conditioning the inheritance pattern of number of bolls/plant. The broad sense heritability was 99.9% and the narrow sense heritability was 57.3% indicating that number of bolls/plant is highly heritable and further significant amount of improvement up to the tune of 57% could be realized if progenies are selected under defined high selection pressure following pedigree progeny selection procedure.

In case of five irrigations the average degree of dominance measured [H1AD]1/2=1.320 indicating that boll number was inherited as an over dominant trait. The number of dominant and recessive genes in the parents [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was 0.433 implying that parents contained preponderance of recessive genes in them. The proportion of negative and positive allele effects in the parents [H2A4H1] was 0.026 implying that negative allele effects are in excess in the parents that are responsible for contributing decreased boll number attributes into their progenies. The number of group of genes controlling dominance loci in the parents [h2AH ] was equal to 0.032 indicating that at least one group of genes was responsible/operative in governing/conditioning the inheritance pattern of boll number in this irrigation treatment. The broad sense heritability was 99.6% and narrow sense heritability was 97% indicating that boll number in five irrigations treatment is also highly heritable and quite responsive under intensive selection pressure to yield significant improvement through pedigree selection pressure

Inheritance of Sympodial Branches

In seven irrigations treatment [H1AD] was 0.941 depicting nearly complete dominance inheritance pattern of sympodial branches per plant (Table 3). The proportion of dominant to recessive genes in the parents [(4DH1) + F]A[(4DH1) F] was 0.343 implying that the recessive genes are in preponderance in the parents. The proportion of positive and negative allele effects [H2A4H1] was equal to 0.188 and since this estimate was less than 0.25 excess of negative allele effects in the parents contributing decreased sympodial branches/plant attributes into their progenies.

The number of effective factors as given by [h2AH2] was 0.103 implied that at least one group of genes controls the dominance at parents' loci and governs the inheritance pattern of sympodial branches in this treatment. The broad sense heritability was 98.9% and the narrow sense heritability was 84.2% suggesting that the character is highly heritable and significant improvement up to the tune of 84% can be brought about if desired combinations are selected under defined intensive selection pressure from progeny rows.

Table 2: Estimates of Genetic Components of Variation Genetic Parameters Variances and Covariances for Number

###of Bolls/Plant in 66 F1 Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm

###Tandojam

SEVEN IRRIGATIONS:

###Parents###CRIS-###CRIS342###SINDH1###NIAB-78###SADORI###BH-160###Wr###Vr###Wr- Vr###Wr+ Vr

###134

###CRIS-134###43.595###40.821###38.931###38.300###36.945###32.954###11.313###12.940###-01.628###24.253

###CRIS-342###40.821###41.233###34.994###35.145###40.056###39.838###07.625###08.084###-0.459###15.708

###SINDH-1###38.931###34.994###32.653###35.293###35.273###35.290###06.784###04.045###02.740###10.829

###NIAB-78###38.300###35.145###35.293###36.648###35.040###34.175###04.086###02.173###01.912###06.259

###SADORI###36.945###40.056###35.273###35.040###36.145###33.004###06.811###05.552###01.259###12.363

###BH-160###32.954###39.838###35.290###34.175###33.004###34.500###01.815###06.516###-4.700###08.331

###D=###15.321###[H1/D] =###1.033###V0L0###15.478

Genetic###H1 =###15.599###Genetic###

###[(4DH 1) + F] A [(4DH1) -F]=

###0.509###V0L1###02.403

components###paramet

###2

of variation###H2 =###13.636###ers###[h /H2]=###0.200###V1L1###05.888

###F=###07.732###[H2/4H1] =###0.219###W0L01###05.754

###2###2###2

###h =###02.723###[h (b)###]=###0.990###(ML1-ML0)###14.378

###E=###00.156###[h

###2

Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm Tandojam

Table 3: Estimates of Genetic Components of Variation Genetic Parameters Variances and Covariances for Sympodia

###Per Plant in 66 F1 Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm

###Tandojam

SEVEN IRRIGATIONS:

###Parents###CRIS-134###CRIS342###SINDH1###NIAB-78###SADORI###BH-160###Wr###Vr###Wr- Vr###Wr+ Vr

###CRIS-134###19.375###24.325###20.863###19.525###19.713###19.313###05.266###03.801###01.465###09.067

###CRIS-342###24.325###25.975###21.800###22.838###21.438###24.363###03.529###03.024###00.505###06.553

###SINDH-1###20.863###21.800###20.725###19.388###18.350###17.000###03.200###03.204###-0.004###06.404

###NIAB-78###19.525###22.838###19.388###19.175###16.563###18.150###05.371###04.280###01.091###09.651

###SADORI###19.713###21.438###18.350###16.563###18.025###18.013###03.748###02.827###00.920###06.575

###BH-160###19.313###24.363###17.000###18.150###18.013###19.825###06.305###06.810###-0.505###13.116

###D=###7.837###[H1/D] =###0.941###V0L0###7.925

Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm Tandojam

Table 4: Estimates of Genetic Components of Variation Genetic Parameters Variances and Covariances for Seed-

###Cotton Yield in 66 F1 Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm

###Tandojam

SEVEN IRRIGATIONS:

###Parents###CRIS-134###CRIS342###SINDH1###NIAB-78###SADORI###BH-160###Wr###Vr###Wr- Vr###Wr+ Vr

###CRIS-134###135.125###145.613###130.413###130.325###126.375###115.788###109.852###96.644###13.208###206.497

###CRIS-342###145.613###139.675###127.975###130.425###134.813###140.638###76.335###44.533###31.803###120.868

###SINDH-1###130.413###127.975###101.200###116.988###118.213###120.750###138.062###106.995###31.067###245.057

###NIAB-78###130.325###130.425###116.988###110.850###116.775###113.913###116.449###71.091###45.358###187.540

###SADORI###126.375###134.813###118.213###116.775###114.625###112.413###112.994###71.677###41.317###184.672

###BH-160###115.788###140.638###120.750###113.913###112.413###109.425###105.162###128.466###-23.304###233.628

###D=###235.54###[H1/D] =###0.801###V0L0###235.991

Genetic###H1 =###141.81###Genetic###

###[(4DH 1) + F] A [(4DH1) -F]=

###0.301###V0L1###55.668

components###parameters###2

of variation###H2 =###122.72###[h /H2]=###1.090###V1L1###86.568

###F=###32.139###[H2/4H1] =###0.216###W0L01###109.809

###2###2###2

###h =###133.72###[h###(b)###]=###0.998###(ML1-ML0)###52.261

Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm Tandojam

Table 5: Estimates of Genetic Components of Variation Genetic Parameters Variances and Covariances for Lint-

###Cotton Yield in 66 F1 Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm

###Tandojam

SEVEN IRRIGATIONS:

###Parents###CRIS-###CRIS342###SINDH1###NIAB-78###SADORI###BH-160###Wr###Vr###Wr- Vr###Wr+ Vr

###134

###CRIS-134###42.058###45.320###40.589###40.561###39.334###36.039###10.643###09.360###01.284###20.003

###CRIS-342###45.320###43.473###39.830###40.593###41.959###43.771###07.397###04.315###03.083###11.712

###SINDH-1###40.589###39.830###31.498###36.411###36.794###37.580###13.374###10.362###03.012###23.736

###NIAB-78###40.561###40.593###36.411###34.500###36.346###35.454###11.280###06.885###04.395###18.162

###SADORI###39.334###41.959###36.794###36.346###35.675###34.985###10.947###06.945###04.001###17.892

###BH-160###36.039###43.771###37.580###35.454###34.985###34.058###10.191###12.443###-2.253###22.634

###D=###22.820###[H1/D] =###0.810###V0L0###22.864

Genetic###H1 =###13.766###Genetic###

###[(4DH 1) + F] A [(4DH1) -F]=###0.302###V0L1###05.393

components###parameters

###2

of variation###H2 =###11.916###[h /H2]=###1.088###V1L1###08.385

###F=###03.101###[H2/4H1] =###0.216###W0L01###10.639

###2###2###2

###h =###12.965###[h###(b)###]=###0.998###(ML1-ML0)###16.266

###2

###E=###00.043###[h###(n)###]=###0.781###`t' of Var. of Wr -Vr n.s.

FIVE IRRIGATIONS:

###CRIE-134###36.968###37.701###37.213###36.551###34.913###31.936###05.136###04.643###00.493###09.779

###CRIS-342###37.701###34.633###35.681###37.499###38.041###39.371###-2.464###02.930###-5.394###00.465

###SINDH-1###37.213###35.681###27.130###31.038###31.253###31.528###13.889###13.116###00.773###27.006

###NIAB-78###36.551###37.499###31.038###28.455###29.984###25.920###17.860###20.878###-3.018###38.737

###SADORI###34.913###38.041###31.253###29.984###30.065###25.441###15.809###19.096###-3.287###34.905

###BH-160###31.936###39.371###31.528###25.920###25.441###26.300###14.385###28.996###-14.611###43.381

###D=###18.40###[H1/D] =###1.025###V0L0###18.445

Genetic###H1 =###35.03###Genetic###

###[(4DH 1) + F] A [(4DH1) - F]=###0.413###V0L1###07.686

components###parameters

###2

of variation###H2 =###28.91###[h /H2]=###4.033###V1L1###14.943

###F=###-6.25###[H2/4H1] =###0.054###W0L01###10.769

###2###2###2

###h =###25.23###[h (b)###]=###0.999###(ML1-ML0)###14.002

###2

###E=###0.041###[h (n)###]=###1.073###`t' of Var. of Wr - Vr n.s.

FOUR IRRIGATIONS:

###CRIS-134###37.235###47.486###28.768###30.138###28.651###31.041###16.310###54.386###-38.076###70.695

###CRIS-342###47.486###23.903###41.319###44.073###38.916###43.024###17.835###68.708###-50.873###86.544

###SINDH-1###28.768###41.319###24.210###29.633###31.219###31.563###-6.118###31.943###-38.061###25.825

###NIAB-78###30.138###44.073###29.633###21.128###30.816###29.279###04.026###54.764###-50.738###58.790

###SADORI###28.651###38.916###31.219###30.816###19.525###29.024###05.838###38.716###-32.878###44.554

###BH-160###31.041###43.024###31.563###29.279###29.024###22.090###06.057###46.229###-40.172###52.286

###D=###39.81###[H1/D] =###1.009###V0L0###40.871

Genetic###H1 =###205.2###Genetic###

###[(4DH 1) + F] A [(4DH1) - F]=###0.338###V0L1###13.900

components###parameters###2

of variation###H2 =###138.8###[h /H2]=###5.052###V1L1###49.124

###F=###51.02###[H2/4H1] =###0.092###W0L01###07.325

###2###2###2

###h =###257.7###[h (b)###]=###0.995###(ML1-ML0)###14.304

###2

###E=###1.060###[h (n)###]=###0.561###'t' of var. of Wr-Vr n.s.

Complete Cotton Diallel Cross During 2009 at Sindh Agriculture University Farm Tandojam

In case of five irrigations the average degree of dominance [H1AD]1/2 was 0.799 depicting partial dominance inheritance pattern of sympodial branches in this treatment. The proportion of dominant and recessive genes in the parents [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was 0.401 showing that some of the parents contained excess of recessive genes in them. The distribution of positive and negative allele effects in the parents [H2A4H1] was equal to 0.005 suggesting that negative allele effect are in preponderance in parents in this asymmetrical distribution and contribute decreased sympodial branches/plant attributes into their progenies. The numbers of group of genes controlling dominance at parents' loci are [h2AH2] =0.155 meaning that at least one group of genes is controlling/governing the inheritance pattern of sympodial branches in this treatment. The broad and narrow sense heritability was 97.5% depicting that the character is highly heritable in this irrigation treatment and quite a significant amount of improvement is expected to be brought about while selecting the genotypes/hybrid combinations under high selection pressure from the progeny rows.

In case of four irrigations treatment the mean degree of dominance [H1AD]1/2 was 0.884 meaning that sympodial branches are also inherited as partial dominant trait in this medium stress treatment. [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was equal to 0.329 implying that the parents contained excess of recessive genes in them. The distribution of positive and negative allele effects in the parents [H2A4H1] was 0.030 implying that negative allele effects are in preponderance in the parents and are responsible for contributing decreased sympodial branches/plant attributes into their progenies through their recessive genes. The numbers of effective factors that control the dominance at parents' loci are [h2AH2] =5.726 implying that at least six groups of genes are controlling the inheritance pattern of this character in this medium stress irrigation treatment. The broad and narrow sense heritability was 92% depicting that sympodial

ranches are also highly heritable in this treatment and quite a significant amount of improvement is realized if selection is made under intensive selection pressure from the hybrid progenies rows.

Under stress conditions of three irrigations treatment sympodial branches/plant also inherited as partial dominant trait as the mean degree of dominance [H1AD]1/2 was equal to 0.693. The proportion of dominant and recessive genes [(4DH1) + F]A[(4DH1) _ F] was equal to 0.369 implying that the recessive genes are in preponderance in the parents and the distribution of positive and negative allele effects [H2A4H1] was 0.094 suggesting negative allele effects contributing decreased attributes are in preponderance. [h2AH ]=1.194 implied that at least one group of genes is governing the inheritance pattern of sympodial branches in this stress irrigation treatment. The broad sense heritability was 98% and narrow sense heritability was 86% suggesting that the character is also highly heritable even under stress conditions and quite significant improvement could be brought about while selecting the desired genotypes from progeny rows even under high selection pressure.

Inheritance of Seedcotton Yield

Seedcotton inherited as partial dominant trait in the normal seven irrigations treatment as [H1AD]1/2 was equal to 0.801 (Table 4). The proportion of dominant to recessive genes in the parents [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was 0.301 indicating that recessive genes were in excess in the parents. The proportion of positive and negative allele effects in the parents [H2A4H1]=0.216 and since this was less than 0.25 (equilibrium stage where negative and positive allele effects are equally distributed in the parents) negative effects are quite pronounced and are responsible for contributing somewhat decreased yielding capacity attributes into their progenies. The number of group of factors controlling the dominant loci in the parents [h2AH ] was 1.09 indicating that at least one group of genes is operative and governs/conditions the inheritance pattern of yield in this treatment. The broad sense heritability was 99.8% and the narrow sense heritability was 78% meaning that seedcotton yield/plant is highly heritable and sufficient improvement up to the tune of 78% could be realized if desired genotypes are selected under defined intensive selection pressure from the single progeny rows hybrid combinations In case of five irrigations the average degree of dominance [H1AD]1/2 was equal to 1.202 indicating that seedcotton yield is over dominantly inherited. The oroportion of dominant and recessive genes in the parents [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was 0.413 indicating that some of the parents preponderantly contained recessive genes in them as compared to others. The distribution of negative and positive allele effects in the parents [H2A4H1] was equal to 0.054 indicating that negative allele effects are in excess in the parents that contribute decreased yielding capacity attributes into their progenies. The number of group of genes controlling dominance in the parents loci [h2AH2]=4.03 suggested that at least four groups of genes are operative and govern the inheritance pattern of seedcotton yield/plant in this irrigation treatment. The broad sense heritability was 99.9% and the narrow sense heritability was 107% indicating that seedcotton yield is highly heritable in this irrigation treatment and quite significant yield improvement could be realized while selecting desirable hybrid combinations for yield under high/intensive selection pressure from the single progeny rows following pedigree method.

In case of four irrigations seedcotton yield also inherited as an overdominant trait as the average degree of dominance [H1AD]1/2=1.3 was greater than unity. The proportion of dominant to recessive genes in the parents [(4DH1)1/2 + F] A [(4DH1)1/2 _ F] was equal to 0.338 and since this value was less than one recessive genes were interpreted in excess in the parents. The distribution of positive and negative allele effects in the parents as given by [H2A4H1] was 0.092 which was less than 0.25 meaning that negative allele effects were in preponderance in the parents and were responsible for contributing decreased yield attributes into their progenies. The number of group of genes controlling dominance loci in the parents [h2AH2] was equal to 5.06 indicating that at least five groups of genes are operative that condition the inheritance pattern of seedcotton yield/plant in this medium irrigation stress treatment. The broad sense heritability of 99.5% and the narrow sense heritability of 55.9% imply that though the seedcotton yield/plant is highly heritable character under medium irrigation stress yet not very substantial yield improvement could be realized if desired plants/genotypes are selected under high selection pressure.

In case of three irrigations treatment average degree of dominance [H1AD] was 1.2 and therefore seedcotton yield was also inherited as over-dominant trait in this stress irrigation treatment. The proportion of dominant to recessive genes in the parents as measured by [(4DH1)1/2 + F] A [(4DH1)1/2 _ F] was 0.370 implying that parents contained excess of recessive genes in them. The proportion of positive and negative allele effects in the parents [H2A4H1] was 0.051 indicating negative allele effects are preponderantly distributed in the parents and are responsible for contributing decreased yield attributes into their progenies through their recessive genes. The group of effective factors controlling dominance loci in the parents was [h2AH2]=11.7 implied that yield is polygenically controlled by at least eleven groups of genes conditioning the inheritance pattern of seedcotton yield in this stress irrigation treatment.

The broad sense heritability was 99.9% and the narrow sense heritability was 182% meaning that quite significant amount of improvement in yield could be sought under stress irrigation treatment if progenies with desired yield attributes are selected under intensive selection pressure. Inheritance of Lint Yield

In seven irrigations treatment (Table 5) lint yield was inherited as partially dominant character as the average degree of dominance measured [H1AD] =0.810. The proportion of dominant and recessive genes in the parents [(4DH1)1/2 + F] A [(4DH1) F] was equal to 0.302 indicating that most of the parents contained preponderance of recessive genes in them. The proportion of positive and negative allele effects in the parents [H2A4H1] was 0.216 showing that negative alleles were in excess in the parents and were responsible for contributing decreased lint yield/plant attributes into their progenies through their recessive genes. The number of groups of genes controlling dominance at the parents' loci [h2AH2] was equal to 1.088 implying that there were at least one to two groups of genes controlling the inheritance pattern of lint yield in this irrigation treatment. The broad sense heritability was 99.8% and the narrow sense heritability was 78% showing that the character is highly heritable and subsequently significant improvement up to the tune of 75% could be realized in lint yield while selecting the desired genotypes/hybrid combinations under intensive selection pressure.

In case of five irrigations lint yield again inherited as an overdominant trait because the average degree of dominance [H1AD]1/2 measured 1.025. The proportion of dominant to recessive genes in the parents as estimated by parameter [(4DH1)1/2 + F]A[(4DH1)1/2 _ F] was equal to 0.413 implying that there was preponderance of recessive genes in the parents. The proportion of positive and negative allele effects in the parents [H2A4H1] was 0.054 implying that the negative allele effects are in excess in the parents and are responsible for contributing decreased lint yield attributes into their progenies. The number of groups of genes controlling the inheritance pattern [h2AH2] was 4.033 indicating that at least four groups of genes were governing of inheritance pattern of lint yield and controlling dominance at the parents' loci. The broad sense heritability was 99.9% and narrow sense heritability as 107% showing that the character is also highly heritable in this irrigation

treatment and subsequently significant amount of improvement could be realized while selecting the desired hybrid combinations under intensive selection pressure from the progeny rows keeping in mind the pedigree of those single progeny rows.

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