D. E. Falk

Relationship between gibberellins, height, and stress tolerance in barley (Hordeum vulgare L.) seedlings

The relationship between gibberellin (GA) levels, height, and stress tolerance was investigated using barley (Hordeum vulgare L.) seedlings, which were exposed to heat stress (50 °C for 3 h) and a free radical generator (Paraquat). Barley cv. Perth seedlings were treated with GA-inhibitors, either a triazole or one of two acylcyclohexanediones. They were tested along with four mutants that were either responsive (MC96 and dwf1) or non-responsive (MC90 and Dwf2) to applied growth-active GAs. Analyses of seedlings, whether mutants, or treated with GA-inhibitors, gave a negative correlation between height and tolerance. We also observed that the shorter seedlings with the least amount of growth active GAs were the most tolerant to stress. The overall results of this study suggest that reduced GA levels or sensitivity to GA, with a concomitant reduction in height are important for induction of stress tolerance.

A model for incorporating novel alleles from the primary gene pool into elite crop breeding programs while reselecting major genes for domestication or adaptation

Cost, time, linkage drag, and genetic drift work against the incorporation of potentially valuable alleles from exotic or non-adapted germplasm into elite crop plants, particularly for quantitative traits. We present a model, motivated by narrow-leafed lupin (Lupinus angustifolius), for efficient incorporation of new alleles from exotic or non-adapted donors into elite gene pools during two phases of breeding. In Phase 1, probability functions from the binomial distribution provide at least 95% confidence that a potentially valuable donor allele (A′) will survive two cycles of backcrossing to elite lines and is fixed in BC2-derived lines. During backcrossing, up to 6 major domestication or adaptation genes from the elite parents are reselected and made homozygous in BC2S0 : 1 family rows. Each plant in the BC2S0 : 1 contains on average 12.5% donor alleles, with >95% probability that a particular donor allele is homozygous in at least one fully domesticated plant in the BC2S0 : 1 population. Plants in these rows or subsequent field trials are selected for valuable quantitative traits, and crossed into elite germplasm to commence Phase 2. Phase 1 is rapid and relatively low cost, and provides a continuous flow of novel genetic diversity into the elite breeding pool.

Resistance to powdery mildew in a doubled haploid barley population and its association with marker loci

The genetic basis of resistance to powdery mildew (Erysiphe graminis DC. f.sp. hordei Marchal) was analyzed using doubled haploid barley (Hordeum vulgare L.) lines from the cross Harrington/TR306. Based on infection types observed after inoculation with defined single-conidium isolates, the lines were classified into four groups. The observed phenotypic ratio fit a two-locus model. The two putative loci were mapped relative to molecular markers. One coincided with the previously mapped dMlg locus on chromosome 4. Based on the observed infection types, Harrington carries the Mlg resistance allele, and TR306 carries a second locus on chromosome 7 (5H); this was tentatively designated Ml(TR). It is the first reported race-specific powdery mildew resistance gene located on that chromosome. These two loci were also detected by simple interval mapping of disease severity data from naturally infected field plots. Composite interval mapping with the first two resistance loci as co-factors detected an additional locus on chromosome 6, with a minor effect on resistance. Finally, superimposing the race-specific classification onto the field data provided evidence for a minor-effect locus on chromosome 7 (5H). The Mlg locus had the largest effect, the Ml(TR) locus had an intermediate effect and the other two loci had very small effects. This study demonstrates the effectiveness of an integrated approach to identifying and mapping resistance loci using classification data from inoculated experiments and quantitative data from field experiments.

Indirect selection for lower deoxynivalenol (DON) content in grain in a winter wheat population

Selection for Fusarium head blight (FHB) resistance and lower deoxynivalenol (DON) content is an important goal in many wheat-breeding programs worldwide. Preliminary screening for less severe FHB symptoms in the early segregating generations can be an important tool to assist breeders in determining which lines to advance to homozygosity. The objectives of this study were: (1) to test influence of plant height, heading date, presence of awns and number of spikelets per spike on FHB index and DON content and (2) to estimate the reliability of indirect selection for lower DON content based on FHB index. A Ruby × Frontana winter wheat population was spray inoculated with a spore suspension of Fusarium graminearum in 2001 and 2002. Plant height was significantly associated with DON content in both years; taller lines accumulated less DON than shorter ones. The moderately resistant lines, based on FHB index after in oculation, had a statistically lower DON accumulation compared with the highly susceptible one...

QTL Identification, Mega-Environment Classification, and Strategy Development for Marker-Based Selection Using Biplots

SUMMARY This paper describes a biplot approach to QTL identification based on phenotypic data from multiple environments, and demonstrates its use in the investigation of QTL-by-environment patterns. The effects of each marker on the target trait were estimated for each environment, leading to a marker-by-environment two-way table. This table was then visually investigated in a marker-by-environment biplot. In the biplot, markers with short vectors should have little or no associations with the trait and can be deleted. The remaining markers would fall into clusters, each suggesting the existence of one or more QTL with similar QTL-by-environment patterns. Within each cluster, the marker with the longest vector should be the one located closest to the QTL. When each QTL is represented by its closest marker, the marker-by-environment biplot is referred to as a QTL-by-environment (QQE) biplot. It can help visualize (1) groups of QTL with similar environmental responses; (2) major vs. minor QTL; (3) the average effect of a QTL and its stability across environments; (4) groups of environments with similar expressions of QTL effects, and (5) QTL allele combinations for maximizing/minimizing the expression of the trait for each mega-environment.

Barley somaclones associated with high yield or resistance to powdery mildew

A study was conducted to evaluate the usefulness of somaclonal variation as a means to obtain powdery mildew resistance in the background of an agronomically elite, high-yielding barley (Hordeum vulgare L.) cultivar. A total of 170 Ro-derived lines were regenerated from embryo-induced callus of the barley cultivar Léger. Forty-five lines were selected and evaluated in replicated field plots at two locations in Eastern Canada. In comparison with Léger, one of the 45 lines was higher yielding, one produced a greater test weight, two had a greater seed weight, and one was shorter in plant height. Three lines were found to segregate for resistance to powdery mildew (Erysiphe graminis DC ex Merat f. sp. hordei EM). Many of the single-plant selections from the three resistant lines showed resistance to powdery mildew under field conditions for two years. Three lines were eventually promoted to the official registration tests in Ontario. One of the three lines was subsequently registered as a new cultivar (AC Malone) in Canada. To our knowledge, AC Malone is the worlds first barley cultivar selected from somaclonal variation. The results of this study demonstrate that it is possible to obtain high- yielding or disease-resistant lines from callus culture in barley.

Exploring Functionality of Hard and Soft Wheat Flour Blends for Improved End-Use Quality Prediction

Blending wheat or flour to meet end-use requirements is a critical part of the production process to deliver consistent quality products. The functionality of commercial Canadian hard red wheat flour (HWF) and soft red wheat flour (SWF) blends with ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (HWF/SWF, w/w) was investigated with new and standard methods to discern which functional properties may be indicators of bread quality and processing performance. Rheological characteristics including farinograph water absorption behavior, dough development time (DT), stability, extensigraph extensibility, and gluten aggregation of wheat flours were significantly influenced by the proportion of HWF in blends of SWF and HWF (P < 0.05). The SWF content in the blends had negative linear relationships with the protein content, lactic acid solvent retention capacity, water absorption, and GlutoPeak peak torque. Polynomial relationships were observed for sodium dodecyl sulfate sedimentation volume, DT, stability, exten...

Protein Structural Features in Winter Wheat: Benchmarking Diversity in Ontario Hard and Soft Winter Wheat

A set of 32 winter wheat lines and varieties was selected to benchmark Ontario winter wheat as a first step toward improving quality. Protein secondary structure, total and accessible thiols, rheological properties, gluten aggregation kinetics, and network forming capabilities of different polymers were determined for each wheat line. Results revealed that there were statistically significant differences among the lines selected (P < 0.05). The differences between hard and soft wheat classes were not as large as would be expected, however, despite the range of quality parameters measured. Benchmarks revealed that several soft wheat lines outperformed hard wheat lines in standard breadmaking quality measures. Protein conformation changed significantly as the moisture content of the samples increased to mimic different model product systems: flour, dough, and batter. The conformation of the flour samples exhibited different patterns between hard and soft wheat classes, although these differences became narr...

Resistant Starch Content Is Related to Granule Size in Barley

Physical properties of resistant starch (RS) were examined in a range of barley genotypes to determine the contribution of starch and seed physical characteristics to the RS component. Thirty-three barley genotypes were studied, which varied significantly in their RS, amylose, and starch contents and grain yield. From 33 genotypes, 13 exhibiting high RS were selected for detailed physicochemical analysis of starch. In high-RS varieties, granule size and number were unimodal, compared with normal starches from a reference genotype, which showed a bimodal distribution. Principal component analysis (PCA) showed that a higher content of granules <15 µm was positively correlated with RS and amylose content, whereas the proportion of granules 15–45 µm was negatively correlated with the RS and amylose contents. Physical fractionation of starches by centrifugation into different population sizes demonstrated that size alone is not an accurate indicator of the population of A-type and B-type granules within a give...

Early generation testing of common bean (Phaseolus vulgaris L.) populations in sole crop and in maize/bean intercrop

Few plant-breeding studies have examined methodology for improving common bean (Phaseolus vulgaris L.) yields by selecting in an intercrop situation. We hypothesized that early-generation testing would be as useful in a maize (Zea mays L.)/bean intercrop as in sole crop for identifying superior bean populations for yield. F2 to F5 bulks of six selected crosses and their F5-derived advanced lines were evaluated in sole crop or intercrop. The F2 and F5 bulks were evaluated together in a preliminary trial in one location, while the advanced lines were evaluated with the F3s in one location, and with the F4s in two locations. Within sole crop, selection of the best three populations, based on F2 performance, provided 67% of the top advanced lines. The rank correlation between average bulk yield across generations and the average line yield was positive and significant. Within intercrop, selection of the best three populations provided 56% of the top advanced lines. The rank correlation between advanced line y...