Breeding Studies On Common Wheat:

Nadya Adly Riad Abd El-nour

The main objective of the present study was to determine thegenetic variance components for some quality traits in wheat. Five wheatvarieties and/or lines were chosen on the basis of their variabilities in thestudied traits. A half diallel set of crosses involving the five parents wasevaluated for, protein, amino acids, gluten, hydration coefficient, moisture,ash, fiber and extracted flour, shorts, fine bran and bran (AACC, 1983).Seventeen amino acids were determined as mg/g sample. Analysis ofvariance was performed for each quality trait. Heterosis was computed asthe percentage deviation of FI mean performance from mid- parent andbetter- parent. Data were genetically analyzed according to Griffing(1956), method 2, model I, Hayman (1954 a and b) and Jinks (1954).Heritability was estimated as Mather and Jinks (1971). The obtainedresults can be summarized as follows:1- Analysis of variance, mean and heterosis:a: Protein and amino acids determined as mg/g sample:1- Significant mean squares due to genotypes along with parents andcrosses were detected for protein and most amino acids (mg/gsample).2- The parental variety P2 gave the highest mean value for protein andseven amino acids. The Fl cross (p3 x PS) was the best combinationfor protein and-rune amino acids since it gave the highest mean values.3- The two crosses (p3 x P4 ) and (p3 x PS) expressed the best heterosisfor protein and most of the studied amino acids.b: Other quality traits:1- Mean squares due to genotypes along with parents and crosses weresignificant for gluten, ash, fiber, as welI as extracted flour and finebran.2- The parent P2 expressed the best mean performance for gluten andextracted flour, while parent PI had the highest value for ash andfiber. The best FI mean values for gluten, ash, and fiber wereobtained for the crosses (p2 x P5(, (p2 x P3) and (Pl x P4),respectively.3- Significant and positive heterotic effects were obtained for gluten inthe crosses P3 x P4, P3 x P5 and P4 x P5 and for extracted flour inboth pl x P3 and P3 x P5.11-Combining ability analysis:a: Protein and amino acids determined as mglg sample:1- Significant mean squares due to both general and specific combiningability were detected for protein and all amino acids studied. HighGCNSCA ratios which largely exceeded the unity were obtained formost traits, indicating that the largest part of the total geneticvariability associated with these traits was a result of additive andadditive x additive types of gene action.2- The parents P2 and P3 seemed to be the best general combiners forprotein and alI amino acids.3- The most desirable SeA effects for protein and most amino acids weredetected in the cross (p3 x P5), folIowedby the cross (p3 x P4).b: Other quality traits:1- General and specific combining ability variances were significant forgluten, ash, fiber and extracted flour. The GCNSCA ratio revealedthat additive and additive x additive gene effects were more importantthan non additive ones for such traits.2- Parent P2 appeared to be the best general combiner for gluten, fiberand extracted flour.3- The best SCA effects were obtained in the crosses (p3 x P4), and (P3x P5) for gluten, and extracted flour, respectively. Four crossesexpressed desirable SCA effects for fine bran.111-Genetic components analysis:a: Protein and amino acids determined as mglg sample:1- The additive component D was appreciable for all traits except alanineamino acid, while the two dominant components HI and H2 weresignificant for all traits except serine amino acid.2- Dominance of heterozygous loci (h2) was unidirectional in 17 out ofthe studied 22 traits with increasing alleles being dominant overdecreasing ones. Overdominance was detected for all traits understudy.3- The alleles of positive and negative effects were not equally distributedamong the parental populations for protein and most amino acids.4- High heritability values in broad sense were detected for all traits.However, narrow sense heritability values ranged from high to lowfor the traits under study.b: Other quality traits:1- Appreciable values for both additive and dominance components weredetected for the traits; gluten, ash, fiber, and extracted flour and finebran.2- Increasing alleles of dominance seemed to be dominant over thedecreasing ones at heterozygous loci and for fiber and fine branoverdominance was indicated for all traits.3- Negative and positive alleles are equally distributed among the parentsfor fiber and flour traits.4- High heritability values in broad sense accompanied by low tomoderate values in narrow sense were obtained for the traits understudy.IV-Graphical analysis:1- The intersection of regression line below the origin point for moststudied traits, revealed overdominance for such traits.2- The distribution of parental varieties along the regression line showedthat varieties P2, P3, and P5 possess an excess of genes behaved asdominant, while the variety P4 possess an excess of genes behaved asrecessive ones for most of the traits studied.3- Significant and positive correlation values between Yr and Wr + Vrwere detected for fiber and leucine, phenylalanine, tyrosine, thrionine,and total amino acids (mglg sample). This indicated that decreasinggenes were dominant over increasing ones for these traits.Appreciable negative correlation values were obtained for protein,gluten; as well as glutamic acid and proline (mg/g sample), revealingthat increaser genes were dominant over decreaser ones.