F. R. Clarke

Identification of QTL and association of a phytoene synthase gene with endosperm colour in durum wheat

The yellow colour 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. We hypothesized that variation in the genes coding for phytoene synthase (Psy), a critical enzyme in carotenoid biosynthesis, may partially explain the phenotypic variation in endosperm colour observed among durum cultivars. Using rice sequence information, primers were designed to PCR clone and sequence the Psy genes from Kofa (high colour) and W9262-260D3 (medium colour) durum cultivars. Sequencing confirmed the presence of four Psy genes in each parent, corresponding to a two member gene family designated as Psy1-1, Psy1-2 and Psy2-1 and Psy2-2. A genetic map was constructed using 155 F1-derived doubled haploid lines from the cross W9262-260D3/Kofa with 194 simple sequence repeat and DArT® markers. Using Psy1-1 and Psy2-1 allele-specific markers and chromosome mapping, the Psy1 and Psy2 genes were located to the group 7 and 5 chromosomes, respectively. Four quantitative trait loci (QTL) underlying phenotypic variation in endosperm colour were identified on chromosomes 2A, 4B, 6B, and 7B. The Psy1-1 locus co-segregated with the 7B QTL, demonstrating an association of this gene with phenotypic variation for endosperm colour. This work is the first report of mapping Psy genes and supports the role of Psy1-1 in elevated levels of endosperm colour in durum wheat. This gene is a target for the further development of a molecular marker to enhance selection for endosperm colour in durum wheat breeding programs.

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

Lillian hard red spring wheat

Lillian, hard red spring wheat (Triticum aestivum L.), exhibited reduced cutting by the wheat stem sawfly (Cephus cinctus Nort.) and is adapted to the Canadian prairies. Lillian produced significantly more grain yield than AC Abbey and Neepawa and its grain yield and protein concentration were similar to AC Barrie. It matured significantly earlier than Superb and Laura, and had improved resistance to leaf rust and leaf spotting diseases compared to AC Abbey. Lillian is eligible for all grades of the Canada Western Red Spring (CWRS) wheat class. Key words: Triticum aestivum L., cultivar description, grain yield and protein, resistance wheat stem sawfly, leaf and stem rust

Temperature effects on seed germination and expression of seed dormancy in wheat

Because preharvest sprouting decreases quantity and quality of wheat grain, researchers need effective protocols to assess response to preharvest sprouting conditions. The aim of this study was to determine which temperature gives the greatest difference in seed germination and expression of seed dormancy in 10 spring wheat genotypes. The genotypes were grown in the field near Swift Current, Saskatchewan in 2000 in a randomized complete block with four replicates. Seed samples were harvested at approximately 25% moisture content (wet weight basis) and dried to 12% moisture content with minimal after-ripening. Germination was under controlled environment at temperatures of 10, 15, 20 and 30 °C in darkness. A weighted germination index (WGI) was calculated. The analysis of WGI, for each temperature, showed highly significant (p ≤ 0.01) genotype effects on germination. Most genotypes decreased in WGI (increased dormancy) as temperature was increased from 10 to 30 °C. The greatest differences in seed germination tended to be at 15 °C and 20 °C. The level of seed dormancy depended on the genotype and germination temperature.

Physiological characteristics of recent Canada Western Red Spring wheat cultivars: Yield components and dry matter production

Genetic yield gains have been difficult to achieve within the Canada Western Red Spring (CWRS) wheat (Triticum aestivum L.) class because of stringent quality requirements and a short growing-season environment with low precipitation and high temperatures. Understanding the physiological basis of yield gains may provide breeders with better insight in selecting parents and screening tools to identify desirable genotypes. The objective of the present study was to compare four new CWRS wheat cultivars with two older cultivars, Neepawa and Marquis, for yield components and dry matter production. When grown at Swift Current, SK, for 3 yr, the average yield for the group of new cultivars was 34.3% higher than that of Marquis (P < 0.01), and 5.9% higher than that of Neepawa (P = 0.10). The new cultivars, as a group, had significantly increased kernel weight, kernels per spike, yield per spike, and spike-filling rate relative to either of the older cultivars. When cultivars were compared individually, all four o...

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 and\or 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...

Influence of plant host quality on fitness and sex ratio of the wheat stem sawfly (Hymenoptera: Cephidae)

Abstract A resurgence of the wheat stem sawfly, historically the most important pest of wheat in the northern Great Plains, has been observed in western Canada over the past decade. Host plant resistance in the form of solid-stemmed cultivars remains the primary management strategy for this pest. The objectives of this study were to determine the effects of wheat cultivar on wheat stem sawfly fitness and sex ratio. The cultivars studied varied with respect to stem diameter and pith expression and included representatives of the red seed, solid-stemmed spring and red seed, hollow-stemmed common and durum wheat classes. We present results from a primary study conducted in southern Alberta from 2001 to 2003 and a similar smaller study conducted in 1987 and 1991. All of the solid-stemmed cultivars (AC Eatonia, AC Abbey, Lancer, Leader) reduced female weights, size, fecundity, and in some cases, larval survivorship in the cut stubs and delayed date of adult emergence in the laboratory. Males were less responsive to this aspect of host quality. The hollow-stemmed durum cultivar AC Navigator had similar negative effects and deserves further study. A number of other hollow-stemmed wheats (McKenzie, AC Intrepid, Katepwa, and the durum AC Avonlea) had intermediate but inconsistent negative effects on sawfly fitness. The varieties that maximized sawfly fitness were AC Cadillac, CDC Teal, and Kyle (durum). Sawfly sex ratios were affected by stub diameter in our current and historical cultivar studies. Larger diameter stubs produced significantly more females and smaller diameter stubs produced more males. Furthermore, stubs that failed to produce adults had significantly smaller diameters than those that produced females but similar to those that produced males. The effect of the solid stem trait on sex ratio was inconsistent. Only Lancer had a male-biased sex ratio, whereas the other varieties had no consistent pattern. These results, however, are similar to other published reports that have noted inconsistent effects of the solid trait on sex ratio. Planting a solid-stemmed cultivar in a rotation that includes broad-leaved crops is recommended to reduce sawfly damage and future populations.

Identification and mapping of leaf, stem and stripe rust resistance quantitative trait loci and their interactions in durum wheat.

Leaf rust (Puccinia triticina Eriks.), stripe rust (Puccinia striiformis f. tritici Eriks.) and stem rust (Puccinia graminis f. sp. tritici) cause major production losses in durum wheat (Triticum turgidum L. var. durum). The objective of this research was to identify and map leaf, stripe and stem rust resistance loci from the French cultivar Sachem and Canadian cultivar Strongfield. A doubled haploid population from Sachem/Strongfield and parents were phenotyped for seedling reaction to leaf rust races BBG/BN and BBG/BP and adult plant response was determined in three field rust nurseries near El Batan, Obregon and Toluca, Mexico. Stripe rust response was recorded in 2009 and 2011 nurseries near Toluca and near Njoro, Kenya in 2010. Response to stem rust was recorded in field nurseries near Njoro, Kenya, in 2010 and 2011. Sachem was resistant to leaf, stripe and stem rust. A major leaf rust quantitative trait locus (QTL) was identified on chromosome 7B at Xgwm146 in Sachem. In the same region on 7B, a stripe rust QTL was identified in Strongfield. Leaf and stripe rust QTL around DArT marker wPt3451 were identified on chromosome 1B. On chromosome 2B, a significant leaf rust QTL was detected conferred by Strongfield, and at the same QTL, a Yr gene derived from Sachem conferred resistance. Significant stem rust resistance QTL were detected on chromosome 4B. Consistent interactions among loci for resistance to each rust type across nurseries were detected, especially for leaf rust QTL on 7B. Sachem and Strongfield offer useful sources of rust resistance genes for durum rust breeding.

Commander durum wheat

Commander durum wheat is adapted to the durum production area of the Canadian prairies. It combines high yield, high grain pigment concentration, and very strong gluten properties. Commander is a semidwarf with strong straw, and has similar maturity and disease resistance to other registered durum cultivars. Key words: Triticum turgidum L. var durum, durum wheat, cultivar description, yield, gluten strength, disease resistance