K. K. Kidwell

Simple plant DNA isolation procedures

A key step in the analysis of plant DNA restriction fragments is the purification of sufficient quantities of good-quality DNA from plant tissues. High DNA yields are often needed for studies that require analysis of several Southern blots, and the purified DNA must be free of contaminants that interfere with restriction endonuclease digestion or electrophoretic separation of DNA fragments. Contaminants, such as polysaccharides, can cause shifts in mobility during electrophoresis resulting in misinterpretation of fragment differences among genotypes. This may not be a problem when analyzing a population that is segregating for a few expected restriction fragments. However, it can be a serious problem when analyzing many unique genotypes for fragment length polymorphisms.

Callus induction and plant regeneration from mature embryos of a diverse set of wheat genotypes

This paper compared the behavior of a diverse set of wheat genotypes in their tissue culture response. Significant differences were detected in plant regeneration, culture efficiency, and regeneration capacity when mature embryos of 47 wheat cultivars, breeding lines, and the common wheat progenitors, Triticum monococcum, T.tauschii, and Aegilops speltoides were compared. Although not currently used in wheat tissue culture, mature embryo-derived callus of cv. ‘Zak’ (SWS), ‘Scarlet’ (HRS), ‘Tara’ (SWS), ‘Jagger’ (HRW), ‘UC 1036’ (HRS), and ‘Kyle’ durum showed better or comparable plant regeneration than commonly cultured cultivars ‘Fielder’ and ‘Bobwhite.’ Of the three diploid wheat progenitors tested, Ae. speltoides regenerated the most plants. In one replicated experiment, callus induction was correlated with culture efficiency (r = 0.42; p = 0.002) and regeneration capacity (r = 0.39; p = 0.002), and in a second larger screen, callus induction correlated with the total number of plants regenerated (r = 0.6; p = 0.001. Immature and mature embryos of ‘Bobwhite’ and ‘Crocus’ were compared for callus induction and plant regeneration. Immature embryos were superior explants in terms of plant regeneration. However, sufficient numbers of plants can be regenerated from mature embryos saving on growth facility resources and time required for the collection of immature embryos.

Identification and mapping QTL for high-temperature adult-plant resistance to stripe rust in winter wheat (Triticum aestivum L.) cultivar ‘Stephens’

High-temperature adult-plant (HTAP) resistance from the winter wheat (Triticum aestivum) cultivar ‘Stephens’ has protected wheat crops from stripe rust caused by Puccinia striiformis f. sp. tritici for 30 years. The objectives of this study were to identify quantitative trait loci (QTL) for HTAP resistance in Stephens through genetic linkage analysis and identify DNA markers linked to the QTL for use in marker-assisted breeding. Mapping populations consisted of 101 recombinant inbred lines (RILs) through single-seed descent from ‘Stephens’ (resistant) × ‘Michigan Amber’ (susceptible). F5, F6 and F7 RILs were evaluated for stripe rust resistance at Pullman, WA in 1996, 1997 and 1998, respectively, whereas F8 RILs were evaluated at Mt Vernon, WA, USA in 2005. The 101 F8 RILs were evaluated with 250 resistance gene analog polymorphism (RGAP), 245 simple sequence repeat (SSR) and 1 sequence tagged site (STS) markers for genetic linkage map construction. Two QTL, which explained 48–61% of the total phenotypic variation of the HTAP resistance in Stephens, were identified. QYrst.wgp-6BS.1 was within a 3.9-cM region flanked by Xbarc101 and Xbarc136. QYrst.wgp-6BS.2 was mapped in a 17.5-cM region flanked by Xgwm132 and Xgdm113. Both two QTL were physically mapped to the short arm of chromosome 6B, but in different bins. Validation and polymorphism tests of the flanking markers in 43 wheat genotypes indicated that the molecular markers associated with these QTL should be useful in marker-assisted breeding programs to efficiently incorporate HTAP resistance into new wheat cultivars.

Adaptation of AACC Method 56-11, Solvent Retention Capacity, for Use as an Early Generation Selection Tool for Cultivar Development

ABSTRACT The solvent retention capacity (SRC) profile is useful for studying flour components contributing to end-use functionality. The method tests four different solvents with 5 g of flour each. Because of the amount of grain (30–40 g) typically needed to produce 20 g of flour for the SRC test, the method is not well-suited for assessing end-use quality of early generation breeding material, where grain quantities are limited. The method was therefore modified to require only 0.2 g of ground wheat instead of 5 g of flour per SRC solvent. The small-scale SRC results using whole meal had correlations of r = 0.86 for lactic acid, r = 0.85 for sodium carbonate, r = 0.78 for sucrose, r = 0.74 for sodium bicarbonate (the alkaline water retention capacity method) and r = 0.69 for water when compared with SRC values from full-scale tests using 5 g of flour. Overall, cultivars with SRC values at the extremes of the distribution were in the same ranked order for the small- and large-scale SRC test results. Howev...

Virulence of Rhizoctonia oryzae on Wheat and Barley Cultivars from the Pacific Northwest

Rhizoctonia oryzae (teleomorph = Waitea circinata) causes sheath spot of rice and root rot of wheat and barley. R. oryzae commonly is isolated from barley, wheat, and pea plants in eastern Washington and Idaho. Eight representative isolates were tested for virulence on spring barley (Hordeum vulgare cv. Baronesse), soft white winter wheat (Triticum aestivum cv. Madsen), and hard red spring wheat (cv. Scarlet) planted in natural soil in the greenhouse and maintained at 16°C. All isolates caused significant reduction of emergence in barley, but only seven of the eight isolates and one of the eight isolates reduced emergence of winter wheat and spring wheat, respectively. All isolates caused significant stunting and reduction in the number of seminal roots, root length, and number of root tips on wheat and barley. Some isolates also reduced the frequency of fine secondary roots, resulting in a reduction of the average root diameter. Spring barley was more susceptible to R. oryzae than winter or spring wheat. The main effects of both cultivar and isolate were significant, and there was a significant isolate-cultivar interaction. R. oryzae isolate 80042 was the most virulent on barley, whereas R. oryzae isolate 801387 was the most virulent on wheat. The two isolates from pea were intermediate in virulence on wheat and barley. When screening germ plasm for potential resistance, isolates exhibiting the maximum virulence for each host should be used.

Environmental influences on flour composition, dough rheology, and baking quality of spring wheat

ABSTRACT The highly variable environmental conditions across the Pacific Northwest (PNW) influence the milling and baking quality of wheat grain produced in this region. This study was conducted to compare the flour composition, dough rheology, and baking quality of soft and hard spring wheat grain produced in diverse environments. Thirteen soft and five hard spring wheat cultivars were grown at Lind, WA (semiarid) and Fairfield, WA (high precipitation) for three years. Grain was evaluated for flour composition, rheology, and experimental baked product quality. Flour composition, rheological properties, and baking qualities were primarily influenced by the environment. Protein contents, microSDS values, and water absorption levels were significantly (P < 0.0001) higher for all cultivars grown at Lind compared with those from Fairfield. Cookie diameters were larger (P < 0.0001) for soft flours from Fairfield, whereas loaf volumes were higher (P < 0.0001) for hard wheat flours from Lind. Results indicate th...

Relationships among genetic distance, forage yield and heterozygosity in isogenic diploid and tetraploid alfalfa populations

Isogenic diploid and tetraploid alfalfa (Medicago sativa L.) was studied with molecular markers to help understand why diploid performance and breeding behavior does not always predict that of tetraploids. In a previous study of partially heterozygous alfalfa genotypes, we detected a low correlation between yields of isogenic diploid (2x) and tetraploid (4x) single-cross progenies, and genetic distances were more highly correlated with yields of tetraploids than diploids. These differences may be related to the level of RFLP heterozygosity expected among progenies derived from heterozygous parents at the two ploidy levels. The objectives of this study were to determine the relationships among genetic distance, forage yield and heterozygosity in isogenic 2 x and 4 x alfalfa populations. Four diploid genotypes were chromosome doubled to produce corresponding isogenic autotetraploids, and these genotypes were mated in 4 × 4 diallels to produce 6 single-cross families at each ploidy level for field evaluation. Allele compositions of parents were determined at 33 RFLP loci by monitoring segregation of homologous restriction fragments among individuals within progenies, and these were used to estimate RFLP heterozygosity levels for all single-cross progenies at both ploidy levels. RFLP heterozygosity rankings were identical between progenies of isogenic diploid and tetraploid parents; but significant associations (P < 0.05) between estimated heterozygosity levels and forage yield were detected only at the tetraploid level. Since tetraploid families were nearly 25% more heterozygous than the corresponding diploid families, inconsistencies in the association between molecular marker diversity and forage yields of isogenic 2 x and 4 x single crosses may be due to recessive alleles that are expressed in diploids but masked in tetraploids. The gene action involved in heterosis may be the same at both ploidy levels; however, tetraploids benefit from greater complementary gene interactions than are possible for equivalent diploids.

Genotypic and environmental variation for flour swelling volume in wheat

ABSTRACT The gelatinization and swelling of wheat (Triticum aestivum L.) starch has an important effect on the quality of end-products, especially white salted noodles. This study was conducted to determine the genotypic and environmental variation for flour swelling volume (FSV) in wheat. FSV was measured for various spring and winter wheat cultivars grown in up to 31 unique environments and up to four crop years. Data were analyzed by organizing the data into eight balanced data sets. FSV ranged from ≈19 to 30 mL/g. Analysis of variance (ANOVA) indicated that cultivar was consistently a highly significant source of variation. Environments as unique combinations of locations and crop years were variably significant, as were locations, whereas crop years were always a significant source of variation. Only rarely were ANOVA interaction terms significant. Model R2 ranged from 0.87 to 0.98 for the eight data sets. Components of variation calculated from ANOVA model and total sums of squares indicated that cu...

Virulence of Pythium Species Isolated from Wheat Fields in Eastern Washington

Although Pythium root rot in wheat (Triticum aestivum) is well documented, limited information is available concerning which species of Pythium are most responsible for disease damage. The objective of this study was to examine the variation in virulence on wheat among isolates of Pythium collected from cereal grain fields in eastern Washington. Isolates of nine Pythium species were tested for virulence on spring wheat cultivars Chinese Spring and Spillman. Cultivars were planted in pasteurized soil infested with Pythium isolates and placed in a growth chamber maintained at a constant 16°C and ambient humidity. Plant height, length of the first true leaf, and number of seminal roots were recorded, and roots were digitally scanned to create computer files that were analyzed using WinRhizo software. Pythium isolates caused a significant reduction (P < 0.05) in the number of root tips, root length, and length of the first leaf. Differences in virulence were detected among species and among isolates within species. Isolate Pythium debaryanum 90136 and P. ultimum 90038 were the most virulent and may prove useful in future disease screening assays of Triticum germ plasm.

Evaluation of Adapted Wheat Cultivars for Tolerance to Pythium Root Rot

Genetic resistance in wheat (Triticum aestivum) against Pythium species would be an efficient means of control of this major root fungal pathogen, but so far no source has been identified. In addition, no long-term, sustainable options for controlling Pythium root rot are available; therefore, identifying and then incorporating genetic resistance into wheat cultivars would create an ideal method of control for this disease. The objective of this study was to examine the level of tolerance to Pythium root rot among a diverse set of wheat germ plasm collected from all major wheat production regions in the United States. Pythium debaryanum isolate 90136 and P. ultimum isolate 90038, previously identified as the most virulent Pythium isolates on wheat, were used to infest pasteurized soil, which was seeded with wheat genotypes and placed in a growth chamber maintained at a constant 16°C with a 12-h photoperiod and ambient humidity. Length of the first leaf and plant height measurements were recorded, and roots were digitally scanned to create computer files that were analyzed using WinRhizo software for length and number of tips. Significant (P < 0.05) differences in plant variables were detected among wheat genotypes in the presence of both Pythium species, and a significant (P < 0.0001) correlation between plant stunting and root loss was detected. Based on both shoot and root measurements, Caledonia, Chinese Spring, MN97695, and OR942504 appear to be highly susceptible to Pythium root rot, whereas genotypes KS93U161, OH708, and Sunco were the most tolerant to this disease.