Effect of bunt infection on the frost resistance of wheat varieties and of lines containing Bt genes

In artificial infection experiments carried out in the nursery in Martonvásár in 1991, 1992 and 1993, studies were made on the bunt infection of wheat varieties bred in Martonvásár and of monogenic lines containing known resistance genes (Bll to Btl0, respectively). This was followed in 1993 by tests on the frost resistance of healthy wheat seedlings and wheat seedlings artificially infected with bunt in the frost-testing chamber of the Martonvásár phytotron. During the period of the experiment, the local pathogen population was avirulent to genes Bt9 and Btl0, and virulent to Bt7. Monogeniclines containing resistance genes Bt4, Bt5, Bt6 and Bt8 had good resistance, while that of lines containing Bt1, Bt2 and Bt3 was only moderate. Among the cultivated varieties, only three proved to be moderately resistant (Martonvásári 17′,‘Martonvásári 23′,‘Fatima 2′), while the remainder were susceptible or very susceptible. The frost resistance of plants infected with bunt was significantly lower, over an average of the varieties, than that of healthy plants. A close (r = 0.890) correlation was found between the bunt susceptibility of the varieties tested and the increase in frost kill due to infection, while no correlation was observed in this respect for monogenic lines containing various resistance genes (Bt).     

Complexity of the Gli-A3 locus in bread wheat

Two bread wheat cultivars, ‘Ariana 8’ and ‘Cajeme 71’, and 129 F₂, grains from the cross between them were analysed for gliadin composition. Two monodimensional (A-PAGE and SDS-PAGE) and two different two-dimensional (SDS-PAGE x SDS-PAGE and A-PAGE x SDS-PAGE) electrophoretic methods were used. Parents differed at the Gli-Al locus, detected by A-PAGE. The SDS-PAGE of the aqueous ethanol extractable protein under nonreduced conditions showed two bands of ‘Ariana 8’ and one of ‘Cajeme 71’, encoded by genes located 22 cM from the Gli-Al locus, and therefore, located at the Gli-A3 locus. This locus has been considered to contain genes coding for ω-gliadins alone. The two-dimensional maps of the parents showed that one band from ‘Ariana 8’ was an ω-gliadin, but the other two bands, one from each parent, were γ-gliadins. Results obtained indicated that GH-A3, like Gli-Al, is a complex locus coding for both ω-and γ-gliadins.     

Gli-B3/Glu-B2 encoded prolamins do not affect selected quality properties in the durum wheat cross 'Abadía'×'Mexicali 75'

A study was made of the effects of the Gli-B3/Glu-B2 encoded prolamins on durum-wheat quality. Twenty-six F₃ lines from the durum wheat cross ‘Abadia’בMexicali 75’ were analysed electrophoretically for prolamin composition and for the following quality parameters: SDS sedimentation value, mixing properties, and percentage grain protein and percentage vitreous kernels. The results showed that the presence or absence of the Gli-B3/Glu-B2 encoded prolamins did not result in any significant difference in the quality characteristics of the F₃ lines; however, as expected, the LMW glutenins encoded at Glu-B3 showed large differences and are therefore the major prolamins influencing durum wheat gluten quality.     

Induction of male sterility in wheat using organic ligands with high specificity for binding copper

Summary Because copper is extremely important to the development of normal polllen, an attempt was made to induce male sterility in wheat by applying specific copper-binding ligands to wheat plants. Four different chelates were used at two rates in three methods of application. All four chelates, cupferron, neocuproine, benzotriazole and cuprizone, reduced grain yield at high concentration applied to the soil at sowing but benzotriazole was most effective, even when applied at late tillering to either soil or foliage, and it also reduced yield to a lesser extent when applied at low concentration. At high concentration of benzotriazole (50 mg kg^-1 of dry soil) the percentage of pollen staining with I₂/KI was very low (0–7%) depending on method of chelate application), and this soil treatment resulted in complete male sterility. The appearance of the pollen, anthers, grain, ears and leaves in many cases mimicked that of normal copper deficiency, and also that caused by other recognised gametocides. These results raise the question of whether binding of copper or some other disturbance of copper metabolism may be the mechanism by which andro-gametocidal chemicals work and if so, dictate a theoretical basis for selecting such chemicals for testing.     

Genetics of resistance to Puccinia graminis tritici and Puccinia recondita tritici in Kenya Plume wheat

Summary Seven genes, viz. Sr5, Sr6, Sr7a, Sr8a, Sr9b, Sr12 and Sr17 were associated with seedling resistance to Puccinia graminis tritici in Kenya Plume wheat. The predominant field cultures were avirulent on seedlings with Sr7a, but possessed virulence for the other six genes. However, Sr7a did not confer adult-plant resistance when present on its own. Adult-plant resistance was attributed to Sr2 and possibly also to the interaction of Sr7a and Sr12.Two genes, Lr13 and Lr14a, were identified in seedling tests with various cultures of Puccinia recondita tritici. Lr13 conferred adult-plant resistance to the predominant field strains. Genetic recombination between Lr13 and Sr9b was estimated at 17.6±3.1%.     

Substitution Analysis of Plant Regeneration from Callus Culture in Wheat

The genetic determination of the plant regeneration ability of tissue cultures arising from immature embryos was studied using a ‘Chinese Spring’/‘Cheyenne’ substitution series. Plant regeneration proved to be polygenically determined. In tile current experiment the chromosomes 7B, 7D and ID were found to be effective, although the possibility of other chromosome effects cannot be excluded.     

Is the pedigree of the near-isogenic line Michigan Amber/8*Chancellor of bread wheat correct?

Summary It is shown that the near-isogenic line Michigan Amber/8^*Chancellor cannot derive from Michigan Amber. Marquillo is suggested as the donor cultivar.     

Wheat pollen dispersal under semiarid field conditions: potential outcrossing with Triticum aestivum and Triticum turgidum

Isolation distance is the main barrier to crop-to-crop gene-flow. A 3-year study assessed the maximum potential outcrossing under field conditions between two wheat cultivars (Triticum aestivum L.) and between wheat and durum wheat (Triticum turgidum L. var. durum). Outcrossing was measured by seed set on emasculated recipient plants placed at four sides with different distances from a 3 m × 3 m T. aestivum (cultivar Chinese Spring) pollen source. Frequencies of seed set at 0 m distance were 45% (37–56%) for T. aestivum cultivars and 18% (5–30%) with T. turgidum. These values agree with hybridization in non-limiting pollen conditions measured by manual crosses in greenhouse. The number of pollen grains and the outcrossing frequencies decreased at increasing distances influenced by the prevailing wind direction. Under semiarid conditions of this assay, viable pollen was found 14 m from the pollen source, with a maximum distance of 8 m at which cross-pollination decreases below 1%. Ambient conditions affect pollen viability, hybridization and pollen dispersal. Data presented in this paper emphasize the major role played by environmental conditions in outcrossing. Data obtained in one area may therefore not coincide with the prevailing situation in different locations and climates.     

Relationship between common wheat (Triticum aestivum L.) gluten proteins and dough rheological properties

This paper reports the correlation between the rheological properties of bread wheat dough and the types and quantities of endosperm proteins in 28 common wheat cultivars. Different methods were used to analyse the allelic composition of these cultivars and the relative quantities of the different proteins contributing to the gluten structure. Neither dough strength (W) nor tenacity/extensibility (P/L) correlated with allelic composition. Different wheats with the same allelic composition (i.e., with respect to glutenins) showed different rheological properties. The glutenins were the most influential components of W and P/L, especially the high molecular weight (HMW) glutenin subunits and in particular the type x form. These proteins seem to increase W and are the main constituents of the gluten network. The gliadins and low molecular weight (LMW) glutenin subunits appear to act as a “solvent”, and thus modify the rheological properties of the dough by either interfering with the polymerisation of the HMW glutenin subunits, or by altering the relative amounts of the different types of glutenin available. Thus, the protein subunits coded for by the alleles Glu-B1x7 and Glu-D1x5 stabilised the gluten network, whereas those coded for by Glu-B1x17 and Glu-D1x2 had the opposite effect. Dough properties therefore appear to depend on the glutenin/gliadins balance, and on the ratio of the type x and type y HMW proteins. The influence of external factors seems to depend on the allelic composition of each cultivar.     

Chromosomal location of genes for resistance to powdery mildew in common wheat (Triticum aestivum L. em Thell.). 8. Gene Pm32 in a wheat-Aegilops speltoides translocation line

The wheat-Aegilops speltoides translocation line L501 exhibits a disease response pattern distinctive from that of documented powdery mildew genes after inoculation with differential Blumeria graminis tritici isolates. Results based on cytological C-bandings and monosomic analyses reveal that a dominant resistance gene derived from Ae. speltoides is located on a T1BL·1SS chromosome translocation in this line. The new gene is designated Pm32. This revised version was published online in July 2006 with corrections to the Cover Date.