John M. Clarke

Allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released from 1845 to 2004

Analysis of genetic diversity changes in existing gene pools of cultivated crops is important for understanding the impact of plant breeding on crop genetic diversity and developing effective indicators for genetic diversity of cultivated plants. The objective of this study was to assess genetic diversity changes in 75 Canadian hard red wheat (Triticum aestivum L.) cultivars released from 1845 to 2004 using 31 simple sequence repeats (SSRs) markers. A total of 267 SSR alleles were detected, and their allelic frequencies ranged from 0.01 to 0.97, with an average of 0.14. Significant allelic reduction was observed at only four SSR loci for the cultivars released from 1970 onwards. However, 51 alleles (about 19%) present in pre-1910 cultivars were undetected in cultivars released after 1990 and were spread over 27 SSR loci. The proportion of SSR variation accounted for by six breeding periods was 12.5%, by four ancestral families, 16.5%, and by eight breeding programs, 8.4%. The average genetic diversity measured by three different band-sharing methods did not change significantly among cultivars released from different breeding periods, breeding programs, and ancestral families. However, genetic shift was obvious in the cultivars released over the six breeding periods, reflecting well the various breeding efforts over years. These results clearly show the allelic reduction and genetic shift in the Canadian hard red spring wheat germplasm released over time. Consequently, more effort needs to be made to broaden the wheat breeding base and conserve wheat germplasm.

Effect of Fusarium head blight on semolina milling and pasta-making quality of durum wheat.

ABSTRACT Ten durum wheat cultivars harvested in Manitoba in 1995, which were downgraded primarily because of fusarium-damaged (FD) kernels, were subjected to mycological tests and evaluated for semolina milling and pasta-making quality. Fusarium graminearum was the primary fungus infecting kernels. The ratio of FD to deoxynivlaenol (DON) level varied slightly among cultivars but was generally near unity. Retention of DON in semolina was about 50%. FD had a negative impact on kernel weight and test weight, resulting in lower semolina yield. Semolina ash content and bran specks were not affected by FD, but semolina became duller and redder. FD had no effect on protein content, but gluten strength was weaker probably due to a lower proportion of glutenins as shown by reversed-phase high-performance liquid chromatographic analysis of sequentially extracted gluten proteins. The influence of FD on gluten strength was not sufficient to alter pasta texture. FD had a strong adverse effect on pasta color. Even for ...

Strongfield durum wheat

Strongfield durum wheat (Triticum turgidum L. var durum) is adapted to the durum production area of the southern Canadian prairies. It combines high yield, high grain protein concentration, and low grain cadmium concentration. Strongfield has shorter, stronger straw than Kyle, and has similar maturity and disease resistance to other currently registered durum cultivars. Key words: Triticum turgidum L. var durum, durum wheat, cultivar description, yield, protein, disease resistance

Effect of Environment and Genotype on Durum Wheat Gluten Strength and Pasta Viscoelasticity

ABSTRACT Data on the quality of durum wheat genotypes grown under eight environments (site-year combinations) were evaluated to determine the relative effects of genotype and environment on quality characteristics associated with gluten strength, protein content, and pasta texture. The 10 durum wheat genotypes assessed in this study represented a range of gluten strength types from the very strong U.S. desert durum genotype, Durex, to the medium strength Canadian genotype, Plenty. Considerable genetic variability was detected for all quality characteristics studied. Genotype-environment interaction was significant for all quality parameters evaluated, with the exception of mixograph development time. Genotypeenvironment interaction was most important in determining protein content and least important in determining gluten index, gluten viscoelasticity, and SDS sedimentation volume. The nature of the genotype-environment interaction was evaluated by determining the number of significant crossover (rank cha...

Concentration of cadmium and other elements in the grain of near-isogenic durum lines

Durum wheat (Triticum turgidum L. var durum) shows genetic variation for concentration of the heavy metal cadmium in the grain. This variation is being exploited to develop cultivars with low cadmium concentration, but there is no information on the effect of incorporation of the trait on uptake of other elements or on economic traits such as yield. Five pairs of near-isogenic high/low cadmium durum wheat lines and their parents were grown in a randomized complete block trial with three replications. Trials were grown at Swift Current, Saskatchewan in 1994, at Swift Current, Stewart Valley and Regina, Saskatchewan in 1995 and 1996, at Langdon and Fargo, North Dakota in 1995, and at Casselton and Langdon, North Dakota in 1996. Grain yield, test weight, kernel weight and protein concentration were determined. Grain cadmium, calcium, copper, iron, magnesium, manganese, nickel and zinc were measured by atomic absorption or inductively coupled plasma emission spectroscopy. The low cadmium trait had no signific...

Allelic variation at Psy1-A1 and association with yellow pigment in durum wheat grain.

The yellow pigment (YP) of durum wheat (Triticum turgidum L. var durum) semolina is due in part to the presence of carotenoid pigments found in the endosperm and is an important end-use quality trait. Phytoene synthase (Psy) is considered a rate-limiting enzyme in the carotenoid biosynthetic pathway and in this study, three alleles of Psy1-A1 were sequenced from four durum wheat cultivars and a co-dominant marker was developed for genetic mapping. Psy1-A1 mapped to chromosome 7AL near Xwmc809 in three durum mapping populations and was significantly associated with a pigment quantitative trait loci (QTL) identified on that chromosome. A second QTL localized 25xa0cM proximal to Psy1-A1 in two populations, and the interaction between the two QTL was not significant. Consistent with QTL mapping data, the Psy1-A1o allele was associated with elevated pigment in a validation population comprising 93 diverse cultivars and breeding lines. These results confirm an earlier hypothesis that Psy1, and at least one additional gene in the distal region of 7AL, are associated with grain YP differences in durum wheat. The functional co-dominant marker developed in this study differentiates the Psy1-A1 alleles reported here and could be used as a target to enhance YP selection in durum wheat breeding programs.

Shifting undesirable correlations

Wheat functions as a complex well-integrated organism with adaptation to many environments. Traits of wheat may be correlated to each other in a positive or a negative manner. The direction of the correlation is independent of breeding objectives and may change from one production environment to another. Grain yield is correlated positively with time to maturity in environments without terminal stress. The negative correlation between grain yield and grain protein concentration exemplifies an undesirable relationship in a wheat quality type in which protein concentration is positively correlated with bread loaf volume. However, this same correlation has an advantage to those end-products that are favored by low protein concentration such as confectionary products. To shift the negative correlation between grain yield and protein concentration requires assembling a more photosynthetically efficient, nitrogen-use efficient andor water-use efficient genotype in combination or separately. Simultaneous selection for quantitative and quality traits is a breeding strategy, which with the inclusion of marker assisted selection, can shift undesirable correlations.

Inheritance of yellow pigment concentration in seven durum wheat crosses

Yellow pigment concentration of the endosperm due to the presence of xanthophyll and other related compounds is an important processing quality characteristic in durum wheat (Triticum turgidum L. var. durum). There is also interest in plant pigments for health reasons because lutein, a major component of durum grain pigment, may play a role in prevention of age-related macular degen eration. Selection for pigment concentration of durum wheat is thus an important breeding objective. Clarification of environmental effects and the mode of inheritance would aid planning of crosses and selection strategies to improve pigment concentration. This study evaluated seven durum wheat crosses of high by low pigment concentration parents in five field trials grown at two or more locations for 2 or more years in western Canada. Pigment concentration varied with environment. A portion of the variability could be ascribed to environmental effects on kernel weight, which tended to be negatively correlated with pigment con...

Effects of nitrogen fertilizer on protein quantity and gluten strength parameters in durum wheat (Triticum turgidum L. var. durum) cultivars of variable gluten strength

ABSTRACT Field studies were conducted over three years at two locations in Saskatchewan, Canada, to determine the effect of nitrogen fertilizer on protein quantity and protein strength in 10 cultivars of durum wheat (Triticum turgidum L. var. durum) representing a range of gluten strength. Increasing nitrogen fertilizer resulted in increased protein content in all cultivars across environments. Cultivars were clearly differentiated on the basis of gluten strength using a gluten index (GI), SDS sedimentation (SDSS), alveograph indices of overpressure (P) and deformation energy (W), mixograph energy to peak (ETP), and mixograph bandwidth energy (BWE) at all fertilizer levels. Variable cultivar response to nitrogen fertilizer was observed only for protein content, GI, and alveograph W. The nature of the cultivar-by-fertilizer interaction for GI suggested that the conventional strength cultivars would benefit more from nitrogen fertilizer than the extra-strong types, which showed no change or slight decreases...

AC Navigator durum wheat

AC Navigator durum wheat is adapted to the Brown and Dark Brown soil zones of the Canadian prairies. It combines high yield with strong gluten properties. It is a semidwarf with shorter straw than all other registered cultivars in Canada, and has similar maturity to Kyle. Key words: Triticum turgidum L. var durum, durum wheat, cultivar description, yield, protein, disease resistance