Development and utilization of single nucleotide polymorphic markers on udp-glucosyl transferases to develop Fusarium head blight resistant wheat varieties

Non-Peer Reviewe

Characterization of Arabinoxylans and β-glucans in Canadian hard red spring wheat cultivars

Non-Peer Reviewe

A simple novel expedited spike culture-derived variation creation strategy in wheat

A wheat (Triticum aestivum L.) immature spike culture system was used to expeditiously generate mutations for use in wheat improvement programs. Wheat immature spikes in culture were treated with three concentrations of ethylmethane sulphonate (EMS) to generate a spike culture derived variant (SCDV) population. EMS in a concentration dependent manner affected seed development in wheat immature spike cultures. Based on the number of seeds produced, inclusion of EMS (25 mM) for three hours in immature spike culture medium generated variants in wheat cv. AC Nanda. The wheat AC Nanda SCDV population showed variation in several phenotypic characters. Flag leaf (length, angle and sheath length), length of first and second internode, spike length, number of spikes, number of seeds per spike and seed weight, showed variation below and above the non-treated controls. A molecular screening technique combining simple sequence repeat (SSR) oligonucleotide primers with high resolution melt (HRM) PCR with EvaGreen was used to identify the variants. Screening for starch branching enzyme IIb (SbeIIb) revealed 75 lines with point mutations. Combining SSR and SbeIIb, a total of 100 Kbp portion of wheat DNA was screened. The estimated mutation frequency in SbeIIb was one per 20.8 Kbp. The spike culture system utilizes very small amounts of EMS for a brief period, thus needs minimal handling of EMS and saves one generation of plant growth in a greenhouse. The morphological variants observed are similar to those reported for seed-derived variants using EMS

Genetic analysis of developmental traits associated with enhanced winter survival in autumn-seeded rye (Secale cereale L.)

Non-Peer Reviewe

cDNA-AFLP analysis of cold-acclimated wheat plants reveals unique transcript profiles in crown tissues

Non-Peer ReviewedLow temperature (LT) adversely affects the productivity of plants. Hence, improving the cold hardiness of crop plants is an important goal in agriculture. However, further understanding of LT tolerance mechanisms in plants is required to achieve this objective. In wheat, survival of crown tissues after exposure to below freezing temperatures during the winter determines successful crop stand establishment at the onset of spring season. Therefore, identification of differentially expressed genes in crown tissues of cold acclimated wheat plants is important as it can allow dissection of molecular mechanisms and biochemical pathways within these tissues. In this study, cDNA-AFLP global transcriptomic profiles of crown tissues cold acclimated at 6oC for 0, 2, 14, 21, 35, 42, 56 and 70 days were compared among a cold hardy winter (vrn-A1) cv. Norstar, a tender spring habit (Vrn-A1) cv. Manitou and two reciprocal near-isogenic lines derived from these two parents differing at the vernalization locus. A total of 2061 differentially expressed transcript-derived fragments (TDFs) were identified using 37 pairs of standard AFLP primer combinations, 30 of which were considered unique due to their genotypic and temporal presence or absence. The remaining TDFs showed differential expression patterns in the four genotypes. Cluster analysis of the unique TDFs revealed influence of the genetic background on expression of these TDFs. BLAST searches of 240 sequenced TDFs showed that 87% of the TDFs had similarity to genes coding for products involved in known functions such as signal transduction, RNA processing and translation, transcription, flowering, cell wall synthesis, metabolism, and protein folding. Thirty-two TDFs did not show similarity to any known genes. Quantitative real-time PCR (QPCR) analyses of these unknown TDFs validated their differential expression patterns. Characterization of their biological function will contribute to an understanding of the role of these novel genes in LT tolerance in wheat. These results suggest that crown tissues undergo a complex adaptive process by changing the expression levels of several genes that determine the level of LT tolerance

Quantitative expression of cold-acclimation genes in wheat (Triticum aestivum L.)

Non-Peer ReviewedWinter wheat (Triticum aestivum L.) is seeded in the fall, regrowth resumes in spring, culminating in an early summer harvest. Yield is generally 20-25% higher than spring wheat. However, winter damage/kill can reduce yield. The low fall temperature allows the wheat plant to cold acclimate – a process during which physiological and biochemical changes occur resulting in the plant being able to withstand freezing temperatures. Specific cold regulated (COR) genes, such as Wcs120, are involved in these changes. Expression of COR genes are induced by transcriptional activators, such as WCBF1, in response to low temperature (LT). However, winter damage can still occur due to genetic differences limiting low temperature acclimation. An understanding of this cold acclimation/tolerance process will allow for better breeding strategies to improve winter wheat survival. Thus, the objective of this study was to determine the quantitative expression of some COR genes from field and growth chamber-grown winter and spring wheats using quantitative real-time PCR and establish their correlation, if any, to LT50 values (temperature at which 50% of plants are killed). Winter wheat (Norstar), spring wheat (Manitou) and two near-isogenic lines (Spring Norstar and Winter Manitou derived from reciprocal crosses of the two varieties) were used. Leaves were sampled on three dates (Sept. 29, Oct. 12 and Oct. 26, 2004) for the field grown plants and after 0, 2, 7, 14, 21, 28, 42, 56, 70, 84 and 98 days of LT acclimation for the growth chamber-grown plants. Relative expression of Wcs120 and WCBF1 genes were determined. Initial expression was high for both genes upon exposure to low temperature for all four lines from the growth chamber experiment. Expression decreased upon longer acclimation periods. The winter hardy wheat, Norstar, showed highest relative expression for both genes compared to the three other lines. This research implies that response to LT is very rapid and that accumulated LT tolerance (LT50) and LT tolerance gene translation, as revealed by accumulation of Wcs120, lags considerably

Expression analysis of low temperature-induced genes in wheat

Non-Peer ReviewedWheat (Triticum aestivum L.) is a widely adapted, economically important crop exhibiting winter, spring and intermediate growth habits. Winter wheat is seeded in the fall, over-winters, resumes growth in spring and is harvested in early summer. It also requires a period of low temperature (LT) exposure, experienced during the fall, to switch from the vegetative to reproductive phase in spring, a process known as vernalization. Low temperature also allows the wheat plant to cold-acclimate to withstand freezing winter temperatures. There has always been an interest to grow winter wheat because of its yield advantage over spring wheat. However, LT tolerance needs to be improved to prevent winter kill and maximize its yield potential. To achieve this more detailed understanding of molecular mechanisms underlying LT tolerance is required. Thus, objectives of this study were to determine the expression of a LT-induced gene and cDNA-AFLP profile in leaf and crown tissues of LT-exposed wheat plants. Survival of crown tissues after exposure to sub-zero temperatures is an indication of the level of LT tolerance of a cultivar. Thus, pattern and levels of expression of LT-induced genes and identification of LT-induced transcripts in this tissue will add to understanding of LT tolerance. Genotypes used in this study included a winter hardy cultivar, Norstar, a tender spring cultivar, Manitou and two-near-isogenic lines with the Vrn-A1 (spring Norstar) and vrn-A1 (winter Manitou) alleles of Manitou and Norstar, respectively. The dominant Vrn-A1 locus confers spring habit and therefore no requirement for vernalization. Quantitative real-time polymerase chain reaction (QPCR) for the cold-regulated gene, Wcor410, indicated that in leaf tissue the Vrn-A1 locus determined level of expression, being higher in the lines having the recessive vrn-A1 allele compared to the dominant Vrn-A1 allele lines. In the crown tissue, the Norstar genetic background led to the higher level of expression than in the Manitou background. cDNA-AFLP analysis also exhibited variable profiles between the two tissues

Allelic diversity of HMW and LMW glutenin subunits and ω-gliadins in Canadian hard red spring bread wheat (Triticum aestivum L.) developed over 150 years

Non-Peer ReviewedWheat (Triticum aestivum L.) is a major cereal crop that is grown around the world. Wheat based products are an important component of human diet as source of calories and proteins. The wheat grain storage proteins are made up of glutenin and gliadin subunits that form gluten in the dough, when wheat flour is mixed with water. The viscoelastic properties of wheat dough lend itself to make diverse food products consumed around the world. During the past few years, wheat gluten has been blamed for increased incidence of some chronic diseases such as obesity and associated cardiovascular ailments and type-2 diabetes. The main objective of this study was to study the diversity in wheat glutenins and gliadins, the two proteins that make up gluten, during 150 years of wheat improvement in Canada. A set of 37 hard red spring wheat cultivars were grown during 2013 and 2014, in a randomized complete block design with four replicates at the Kernen farm, University of Saskatchewan. Cultivars were selected based on the year of release from 1860 to 2007 and subdivided into historical and modern wheats. Historical cultivars included 11 entries released in Canada from 1860 until 1935 and the modern group included 26 cultivars released after 1935 and up to 2007. Gluten protein composition was determined by SDS-PAGE. Most of the genotypes in both groups had the combination Glu-A1b (2*), Glu-B1c (7+9) and Glu-D1d (5+10) for the high molecular weight glutenins (HMW-GS). Another allele that remained stable was the low molecular weight glutenin (LMW-GS) Glu-A3e present in 91% (historical) to 58% (modern) of the cultivars. Most variation was observed in the frequency of appearance of the most common subunits in the LMW-GS Glu-B3 and Glu-D3. For instance, in the historical group, the most common alleles were the Glu-B3b’ (55%) and the Glu-D3a (37%) or Glu-D3b (36%) whereas in modern cultivars Glu-B3h (58%) and the Glu-D3c (58%) were most frequent. Regarding ω-gliadins encoded by the Gli-B1, a relative high proportion of the historical genotypes carried the Gli-B1b subunit whereas in modern cultivars the Gli-B1d (58%) was common. No major alterations in the gluten subunits were observed between the Canadian historical and modern hard red spring wheat cultivars developed over the last century and half. However, subtle differences were found in the HMW-GS and the LMW-GS Glu-A3, and the frequency of appearance in the Glu-D3 and Glu-B3 (LMW-GS) and the Gli-B1 (ω-gliadins). The impact of the alterations on the incidence of Celiac disease is currently being studied

Genetic mapping of pre-harvest sprouting resistance loci in bread wheat (Triticum aestivum L.)

Non-Peer ReviewedPre-harvest sprouting (PHS) in bread wheat (Triticum aestivum L.) is the germination of mature grain while still in spike. PHS causes downgrading of grain quality which severely limits its end use. In western Canada, cool and wet weather during harvest makes the crops susceptible to PHS. Breeding for PHS tolerance in wheat is challenging on phenotypic basis because PHS is inherited quantitatively and strongly affected by environmental conditions. A mapping population of one hundred and fifty one doubled haploid (DH) lines from a cross between two spring wheat cultivars ND690 (non-dormant) and W98616 (dormant) was developed for genetic mapping of PHS resistance loci. Initially, 20 dormant and 20 non dormant lines were used for genetic mapping with SSR (Simple sequence repeat) and AFLP (Amplified Fragment Length Polymorphism) markers. A total of 550 markers (300 SSR markers and 250 AFLP) markers have been mapped on different chromosomes. Five chromosomal regions on the chromosomes 1A, 3B, 4A, 5B and 6B associated with pre-harvest sprouting were identified in this study

Identification and validation of QTLs associated with pre-harvest sprouting tolerance in bread wheat

Non-Peer ReviewedPre-harvest sprouting (PHS) is the in-spike germination of physiologically mature grain in response to relatively high humidity due to untimely rains prior to harvest. PHS in bread wheat (Triticum aestivum L.) results in substantial economic loss, as it decreases the functional quality of wheat grain. The Canadian Grain Commission sets the limit of percentage severely sprouted and total sprouted grain depending on the grade and wheat classes. Pre-harvest sprouted wheat is reduced in grade and value, depending on the quantity of sprouted kernels present in a sample. Breeding for PHS tolerance in wheat is challenging on phenotypic basis because PHS is inherited quantitatively and highly influenced by environmental conditions. Seed dormancy is the main factor responsible for conferring the PHS resistance to the grains of bread wheat. The objectives of this study were to identify and validate the major quantitative loci (QTL) for pre-harvest sprouting (PHS) resistance in bread wheat. A F1-derived doubled haploid (DH) population of 151 lines from a cross between two spring wheat cultivars ND690 (nondormant) and W98616 (dormant) was used to identify the genomic regions associated with PHS tolerance. A total of 950 polymorphic markers (369 SSR, 306 AFLP, 267 DArT and 8 EST) have been used to develop a genetic map and to identify QTLs for PHS tolerance. Interval mapping revealed a major QTL on chromosome 4A explaining 25% phenotypic variation in this mapping population. Forty two Canadian wheat cultivars and germplasm lines were screened with the DNA marker in the QTL region on chromosome 4A for validation. 113 BC1F1 plants from four different backcrosses were screened with the marker associated with PHS resistance. Marker assisted back crossing reduced the population size in BC1F1 generation by 40.7%. This information will help the plant breeders to pyramid this QTL with other QTLs from different PHS resistance sources