Relationship Between Gluten Strength and Glutenin Proteins in Durum Wheat Cultivars

An electrophoretic study of gliadin and glutenin proteins, mainly low-molecular-weight (LMW) Glutenin Subunits, was undertaken to investigate possible assoeiations between these proteins and gluten strength. Thirty-eight durum wheat cultivars having different origins and currently grown in Spam were analysed. Different electrophoretic methods were used to analyse the seed storage proteins. Protein grain content was estimated and gluten strength was measured by the SDS-sedimentation test. New patterns for LMW glutenins were observed. Besides the known patterns of LMW-1, associated with γ-gliadin 42, and LMW-2 associated with γ-gliadin 45, six cultivars had LMW-2^? associated with γ-gliadin 43, one cultivar showed LMW-2* associated with γ-gliadin 44, and another cultivar, null for γ-42 and γ-45, had LMW-1^?. Significant differences for gluten strength were found among groups of cultivars with different LMW patterns. High molecular weight glutenins were found in general to be poor indicators of viscoelastic properties, although band 20 showed a negative influence on quality. The results are discussed in relation to development ol cultivars with good gluten strength.     

Effect of Water Status on Leaf Angle and Leaf Movement in Wheat

Water stress was imposed by watering withholding or application of PEG during the period following ligule emergence of Hag leaves or fifth leaves. Treatment reduced markedly the downward rotation of these youngest fully expanded leaves, and the angle finally reached. Leaf angle changes appear to be sensitive indicators of water shortage in wheat.     

Amplified fragment length polymorphism- and simple sequence repeat-based molecular tagging and mapping of greenbug resistance gene Gb3 in wheat

The greenbug, Schizaphis graminum (Rondani), is the most economically damaging aphid pest of wheat in the southern Great Plains of the USA. In this study, the single, dominant greenbug resistance gene, Gb3, was molecularly tagged and genetically mapped using amplified fragment length polymorphism (AFLP) and simple sequence repeat(SSR) markers. Three AFLP loci were associated with the Gb3 locus in linkage analysis with 75 F_2:3 families from the cross between two near‐isogenic lines (NILs) for Gb3,‘TXGBE273’ and ‘TXGBE281′. Two of these loci, XMgcc Pagg and Xmagg Patg cosegregate with Gb3 in the population analysed. Further analysis indicated that XMgcc Pagg and Xmagg Patg are specific for the Gb3 locus in diverse genetic backgrounds. Two SSR markers, Xgwm111 and Xgwm428 previously mapped in wheat chromosome 7D, were shown to be linked with Gb3, 22.5 cM and 33.1 cM from Gb3, respectively, in an F₂ population of ‘Largo’בTAM 107’, suggesting that Gb3 is located in the long arm of chromosome 7D. The two AFLP markers cosegregating with Gb3 are valuable tools in developing molecular markers for marker‐assisted selection of greenbug resistance in wheat breeding.     

An analysis of genes for resistance against Indian stem rust races in two bread wheat cultivars

Summary The genetic constitution of two bread wheat accessions from the International Spring Wheat Rust Nurseries (E 5883 and E 6032) has been studied for reaction to four Indian races of stem rust. Analysis of E 5883 has revealed that for each of the races 15C, 21 and 40 a single dominant gene operates for resistance. The dominant gene against race 15C was identified as Sr6. The dominant genes for resistance against races 21 and 40 were found to be different from the genes described so far. Resistance against race 122 is controlled by a single recessive gene producing characteristically a 2 type of reaction. This gene was identified as Sr8.The resistance of E 6032 against each of the races 15C, 21 and 40 is controlled by two genes, one dominant and one recessive, which act independently. Dominant genes effective against 15C, 21 and 40 were conclusively identified as Sr6, Sr5 and Sr9b, respectively. From the correlated behaviour against races 15C and 40 as well as from the phenotypes of the resistance reactions rhe same recessive gene, undescribed so far, operates against the two races. The second recessive gene operating against race 21 was also observed to be different from those so far designated. E 6032 was, however, found to be susceptible to races 122.The presence of Sr6 both in E 5883 and E 6032 against race 15C was further confirmed through F₂ and F₃ segregation data.     

Variation in pigment content of flour color in bread wheat (Triticum aestivum L.)

Summary Variation in pigment content of the flour of bread wheats (Triticum aestivum L.) was studied in the progenies of F₁ and F₂ of three crosses and their reciprocals. Reciprocal differences in pigment content were observed in the F₁ and F₂ means. Low pigment content was found to be partially dominant or over dominant in the crosses studied. There was evidence of substantial mid-parent F₁ heterosis in all crosses and betterparent F₁ heterosis in three crosses. In the F₂, heritability estimates were moderate to high. The F₂ frequency distributions were not normal. Estimation of effective factor pairs indicated the presence of one or two major gene pairs involved in the expression of pigment content in the flour. Action of modifiers was also assumed in one cross and its reciprocal. A factorial approach to metrical character suggested that the F₂ segregation ratios of low pigment content to high pigment content were 3:1, 15:1, 13:3 and 9:7 for the different crosses. Utilization of the findings in a wheat breeding program is briefly discussed.     

Morphology,geography and infraspecific taxonomics of Triticum dicoccoides Körn. A retrospective of 80 years of research

Summary Research on the morphology, geography and infraspecific taxonomics of Triticum dicoccoides Körn. performed during the 80 years since its rediscovery by Aaronsohn is reviewed. T. dicoccoides is a vluable genetic resource for the improvement of cultivated wheat. Its intraspecific structure is, however, not known sufficiently. It is evident that T. dicoccoides is subdivided into two morphologically and geographically distinct forms. The intepretations of these forms by various authors are diverse. There is also no consensus concerning their geographical within the general range of T. dicoccoides. It is necessary to carry out a detailed morphological study in order to define their taxonomical rank and specify their ranges. It would be expedient to perform comparative genetic, biochemical and agronomic investigations of the two T. dicoccoides infraspecific types.     

Vernalization of immature embryos of winter wheat genotypes

Summary The effect of direct vernalization of immature embryos on flowering was studied in six winter wheat genotypes. Fourteen-, 17-, and 20-day-old embryos were excised and vernalized for 0–6 weeks on synthetic medium during a conditioning period. Percent germination of embryos was high (overall 96.1%), and free from genotypic effects. Genotypes differed for flowering in response to cold treatment of excised embryos. Embryo vernalization was as effective as or more than conventional vernalization (control, seedling vernalization for 6 weeks). Seventeen-day-old embryos were the most responsive to vernalization. With a 5-week vernalization of 17-day-old embryos, the percentage of plants anthesed was higher than those from 14-and 20-day-old embryos. For 17-day-old embryos vernalized for 5 weeks, the mean number of days from culture to anthesis was less than that of 6 week vernalization, less than that of 14- and 20-day-old embryos, and less than controls.Purdue Univ., Agronomy Dept., W. Lafayette, IN 47907, USA.     

The importance of abortive stoma penetration in the partial resistance and nonhost reaction of adult barley and wheat plants to leaf rust fungi

Summary Early stages of the infection process of Puccinia hordei isolate 1.2.1 and of a P. recondita f.sp. tritici isolate were studied on adult plants of four barley lines and one wheat line. Two of the barley lines are extremely susceptible to P. hordei, the other two have a very high level of partial resistance.A histological study based on a trypan blue staining indicated that stoma penetration by P. hordei isolate 1.2.1 was equally successful on the susceptible as on the partially resistant adult barley plants. Abortion of substomatal vesicles was rare in all lines. These results do not support a hypothesis that mechanisms of partial resistance in adult plants differ from those in seedlings by a substantial abortive stoma penetration.Also in the nonhost combinations wheat-P. hordei and barley-P. recondita f.sp. tritici inhibition of stoma penetration and of substomatal vesicle development appears to play a biologically insignificant role in adult plants.The proportion of stoma penetration on the leaf sheaths of two of the barley lines was as high as on the leaf blades of the flag leaf and the leaf below the flag leaf. There was no evidence for stomatal exclusion as a crucial factor in the relatively low infectibility of leaf sheaths to leaf-blade specialized rust species.     

Chromosome Locations of Additional Barley Enzyme Loci Identified Using Wheat-Barley Addition Lines

Disomic wheat-barley addition lines carrying a full hexaploid set of chromosomes of the wheat cultivar Chinese Spring, plus a pair of either chromosome 1, 2, 3, 4, 6, or 7 from the barley cultivar Betzes, were assayed electrophoretically. Comparisons of zymograms of each addition line with the Chinese Spring wheat and Betzes barky parents of the addition lines gave direct (presumptive in the case of chromosome 5) evidence of the chromosomal locations of nine enzyme loci which have been useful genetic markers in studies of the population genetics, ecogeneties and breeding of barley. Previously reported chromosome locations of several loci were confirmed and evidence was presented for the existence and probable chromosome locations for additional enzyme loci.     

Cytology and Fertility of Hybrids and Amphiploids between Aegilops caudata L. ×Triticum turgidum (L.) Thell

Interspecific hybrids and amphiploids between Aegilops caudata L. (2n = 2x = 14, CC) and Triticum turgidum (L.) Thell. conv. durum Desf M. K. (2n = 4x = 28, AABB) were produced. Such hybrids can be used to introduce desirable traits such as disease resistance into cultivated durum wheats. One of the durum parents was a ph I mutation of the cv. ‘Cappelli’ used for testing the possibility of direct introduction of alien variation into cultivated species. The amphiploids were obtained both through colchicine chromosome doubling and as natural non-reductional mciosis products. In both hybrids and amphiploids, meiotic pairing and fertility were studied. Hybrids showed varying degrees of pairing and, in addition to the one involving the ph 1 mutant, one high pairing hybrid was found (Ae. caudata× cv. ‘Capinera’). Cytological examination of microsporogenesis in amphiploids revealed a high frequency of bivalent formation. Fertility proved to be a very variable character since some of the amphiploids were almost completely sterile. The use of amphiploids in breeding programmes is discussed in relation to meiotic and fertility data.