Andrew C. Hogg

Wheat puroindolines interact to form friabilin and control wheat grain hardness

Wheat grain is sold based upon several physiochemical characteristics, one of the most important being grain texture. Grain texture in wheat directly affects many end use qualities such as milling yield, break flour yield, and starch damage. The hardness (Ha) locus located on the short arm of chromosome 5D is known to control grain hardness in wheat. This locus contains the puroindoline A (pina) and puroindoline B (pinb) genes. All wheats to date that have mutations in pina or pinb are hard textured, while wheats possessing both the ‘soft type’ pina-D1a and pinb-D1a sequences are soft. Furthermore, it has been shown that complementation of the pinb-D1b mutation in hard spring wheat can restore a soft phenotype. Here, our objective was to identify and characterize the effect the puroindoline genes have on grain texture independently and together. To accomplish this we transformed a hard red spring wheat possessing a pinb-D1b mutation with ‘soft type’ pina and pinb, creating transgenic isolines that have added pina, pinb, or pina and pinb. Northern blot analysis of developing control and transgenic lines indicated that grain hardness differences were correlated with the timing of the expression of the native and transgenically added puroindoline genes. The addition of PINA decreased grain hardness less than the reduction seen with added PINB. Seeds from lines having more ‘soft type’ PINB than PINA were the softest. Friabilin abundance was correlated with the presence of both ‘soft type’ PINA and PINB and did not correlate well with total puroindoline abundance. The data indicates that PINA and PINB interact to form friabilin and together affect wheat grain texture.

Applying Real-Time Quantitative PCR to Fusarium Crown Rot of Wheat

Fusarium crown rot (FCR) of wheat is a persistent problem that causes significant losses worldwide. In Montana, FCR is caused primarily by Fusarium culmorum and F. pseudograminearum. Recently, a real-time quantitative PCR (QPCR) assay was developed for FCR using primers and probes specific for a segment of the trichodiene synthase (tri5) gene. The purpose of this study was to determine the utility of QPCR for accessing FCR severity on wheat in field experiments. In 2004 and 2005, plots of spring and durum wheat were inoculated with varying levels of F. pseudograminearum oat inoculum and grown under rain-fed conditions. Two weeks prior to harvest, plants were collected from the plots and assessed for FCR severity and analyzed by QPCR for Fusarium DNA quantities. Disease severity scores (DSS) and Fusarium DNA quantities were positively correlated with each other for all three cultivars in 2004 but for only the durum cultivar in 2005 (P < 0.05). In 2004, grain yields for both spring wheat cultivars were negatively correlated with Fusarium DNA quantities (P > 0.05). When DSS and Fusarium DNA quantities negatively correlated with yield, both measurements were comparable in predicting yield reduction (R = -0.64 and -0.77, respectively). Results indicate that this QPCR assay is effective in measuring FCR severity in wheat.

Distribution and Prevalence of Fusarium Crown Rot and Common Root Rot Pathogens of Wheat in Montana

Distribution of Fusarium crown rot (FCR) and common root rot (CRR) pathogens associated with wheat (Triticum aestivum) in 91 fields in Montana were determined during the 2008 and 2009 crop seasons using real-time quantitative polymerase chain reaction (qPCR) and conventional isolation methods. Correlations (P < 0.001) were found between detection methods for both diseases. FCR was detected in 57% of the fields and CRR was detected in 93% of the fields surveyed. Percent incidence based on isolation from individual tillers was Bipolaris sorokiniana (15%), F. culmorum (13%), and F. pseudograminearum (8%). FCR populations were highly variable across the regions and were not detected in any fields from the Gb5 soil types of Judith Basin and Fergus counties. The spatial distributions of FCR and CRR were affected by elevation, soil type, and temperature. High FCR populations were associated with spring wheat crops rather than winter wheat based on qPCR (P < 0.001). FCR and CRR could produce yield losses in a range of 3 to 35%. This study is the first time that qPCR was used to survey these two pathogen groups, and the merits and weakness of qPCR relative to traditional isolation methods are discussed.

Comparison of pathogenicity of the Fusarium crown rot (FCR) complex (F. culmorum, F. pseudograminearum and F. graminearum) on hard red spring and durum wheat.

Fusarium species involved in the Fusarium crown rot (FCR) complex affect wheat in every stage of development from seedling to grain fill. This study was designed to compare the aggressiveness of the FCR complex members including F. culmorum, F. pseudograminearum and F. graminearum in causing seedling blight, decreased plant vigour and crown rot. To assess their relative pathogenicity, two hard red spring wheat cultivars and two durum wheat cultivars were inoculated in the field with five isolates from each of the three species for two years. Significant differences in patterns of pathogenicity were identified. In particular, F. culmorum caused greater seedling blight while F. pseudograminearum and F. graminearum caused greater crown rot. Greatest yield reductions were caused by F. pseudograminearum. Cultivar differences were identified with respect to seedling disease and late season crown rot. No interactions were identified between cultivar performance and isolates or species with which they were challenged.

Nutritional and Quality Traits of Pasta Made from SSIIa Null High-Amylose Durum Wheat

Food products that are high in fiber and low in glycemic impact are healthier. Amylose is a form of resistant starch that mimics dietary fiber when consumed. A durum wheat (Triticum durum) line was created that lacks starch synthase IIa (SSIIa) activity, a key enzyme in amylopectin biosynthesis, by identifying a null mutation in ssIIa-B following mutagenesis of a line that has a naturally occurring ssIIa-A null mutation. Our objective here was to compare seed, milling, pasta, and nutritional characteristics of the SSIIa null line with a wild-type control line. The SSIIa null line had increased amylose and grain protein with lower individual seed weight and semolina yield. Refined pasta prepared from the SSIIa null semolina absorbed less water, had increased cooking loss, had a shorter cook time, and was considerably firmer even after overcooking compared with the wild-type line. Color of the SSIIa null cooked and uncooked pasta was diminished in brightness compared with the wild type. Nutritionally, the S...

Mutagenesis-Derived Puroindoline Alleles in Triticum aestivum and Their Impacts on Milling and Bread Quality

Wheat (Triticum aestivum) end-product quality is impacted by grain hardness, which is determined by the Hardness locus consisting of the Puroindoline a and Puroindoline b genes, Pina and Pinb, respectively. Hard wheats commonly contain just one of two Pin mutations. We previously demonstrated the creation and preliminary hardness testing of 46 Pin missense alleles. In this study we examine the degree that individual Pin missense alleles confer unique milling and bread quality traits. Three Pina (PINA-R103K, -G47S, and -P35S) and four Pinb (PINB-D34N, -T38I, -G46D, and -E51K) missense alleles were chosen because they impart variable grain hardness levels, with one allele conferring soft seed texture, three conferring intermediate hardness (single-kernel characterization system [SKCS] hardness approximately 50), and three conferring hard grain texture (SKCS hardness greater than 60). All but two of the alleles (PINA-R103K and PINA-G47S) resulted in higher total flour yield when compared with wild-type contr...

Impacts of SSIIa-A Null Allele on Durum Wheat Noodle Quality

ABSTRACT A small increase in amylose content may impact end-product quality of wheat. The effect of elevated amylose content in durum wheat is not known. We surveyed 255 durum wheat accessions and found two genotypes that lacked the SGP-A1 protein. These genotypes were crossed to Mountrail, an adapted durum genotype, to create populations segregating for the SSIIa-Ab null allele. Our goal was to determine the influence of allelic variation at the SSIIa-A locus on semolina properties and end-product quality with noodles as a test product. Amylose content increased 3% and cooked noodle firmness increased 2.8 g·cm for the SSIIa-Ab class compared with the SSIIa-Aa class for the PI 330546 source, but no change in either trait was detected between classes for the IG 86304 source. The SSIIa-Ab class had a 10% reduction in flour swelling compared with the SSIIa-Aa class for both crosses. Grain protein and semolina yield did not differ between SSIIa-A classes. The relationship between flour swelling power and nood...

Creation and Characterization of a Double Null Puroindoline Genotype in Spring Wheat

Wheat (Triticum aestivum L.) grain hardness is controlled by the Ha locus, which is composed of two closely linked genes, Puroindoline a (Pina) and Puroindoline b (Pinb). Hard grain results from mutations in either of the Pin genes. Previous results have shown that the Pina-D1b (Pina null) allele has harder grain than other naturally occurring Pin alleles. Our goal was to create, identify, and characterize a double null Pin genotype by identifying a Pinb null mutation in a variety carrying the Pina-D1l null allele. Seeds of Fortuna, which has a premature stop codon in Pina, were treated with ethyl methanesulfonate. Two premature stop codon mutations were identified in Pinb using direct sequencing. The double null Pin haplotype was characterized after backcrossing to the parent variety Fortuna to create Pina null populations segregating for the presence of Pinb. The double null group was 6 units harder than the single null with no difference in other kernel characteristics. The milling characteristics diff...

Novel ssIIa Alleles Produce Specific Seed Amylose Levels in Hexaploid Wheat

Novel starch synthase II (ssIIa) alleles were created in a soft wheat (Triticum aestivum L.) via ethyl methanesulfonate mutagenesis and combined by crossing to create four unique ssIIa triple mutant haplotypes. A range of starch amylose content was obtained from the ssIIa triple mutant lines (35.6–46.8%), with moderate increases in amylose content found in lines carrying two ssIIa null alleles and one partially functional ssIIa allele. Seeds from all ssIIa triple mutants had significantly higher amylose and protein contents but also lower starch content, kernel weight, and flour swelling power compared with their wild-type sister lines. Seed starch amylose content was negatively correlated with individual kernel weight (r = –0.54), starch content (r = –0.85), and flour swelling power (r = –0.91) but positively correlated with grain protein (r = 0.78), demonstrating that unique ssIIa triple mutant null combinations confer defined levels of seed starch amylose, protein content, and kernel size. The ssIIa mu...