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Quality Trait Variation in Major Hard Red Spring Wheat Cultivars Released in North Dakota Since 1968

August 12, 2008

By Underdahl, J L Mergoum, M; Schatz, B; Ransom, J K

ABSTRACT Over the last 40 years, grain yield of hard red spring wheat (HRSW) (Triticum aestivum L.) has increased dramatically in North Dakota and neighboring regions. This yield increase has caused some concern that recent higher yielding cultivars might be released at the expense of quality performance. A two-year study was initiated in 2004 to examine the changes in quality performance of HRSW cultivars released by North Dakota State University (NDSU) over the past 40 years. The experiment was conducted in North Dakota at three and two sites in 2004 and 2005, respectively. The study included 33 HRSW genotypes laid out in a randomized complete-block design with four replicates. Grain protein content, flour- extraction yield, mixogram scores, Falling Number, glutograph scores, water absorption, dough character score, and loaf volumes did not vary significantly with year of release. Linear regression of cultivar means on year of release showed an annual increase in crumb color score of 0.4%/yr since 1968. Grain volume weight showed a significant and positive correlation with crumb color score (r = 0.62, P

Breadbaking characteristics are the primary end-use criteria used to select HRSW genotypes in the northern part of the United States, although market diversification has expanded the use of hard wheats beyond breads to include other products such as Asian noodles (Souza et al 2004). The high protein content and superior gluten quality of HRSW makes it ideal for many baked products. Flour mills worldwide use HRSW as a blending wheat to increase the gluten strength of other wheat classes with lower protein. These flour blends can be used to make an assortment of bread products and Chinese-type noodles. Yeast breads, hard rolls, whole grain breads, pizza crusts, and bagels are some of the many products that have superior appearance and taste when made using high-quality spring wheat.

There are several critical end-use quality traits required to produce high-quality spring wheat for milling and baking purposes (Guttieri et al 2000). These characteristics include grain protein content, milling quality, dough handling characteristics, and breadmaking properties. Indicators of milling quality include grain volume weight, 1,000-kernel weight, and flour extraction yield (Finney et al 1987). Indicators of baking quality include grain protein content, mixing time, mixing tolerance, water absorption, loaf volume, and crumb color. Guttieri et al (2000) suggested, however, that selecting for key quality attributes is difficult, and that protein content, flour extraction yield, and loaf volume have not been improved significantly with selection when compared with historical cultivars.

Hard red spring wheat grown in the northern Great Plains of North America is a premium class of wheat used in end-use applications requiring high gluten strength. Specific breeding objectives of the wheat improvement programs in the spring wheat region over the past century include improving or maintaining disease resistance, improving breadmaking quality, and improving grain yield potential (Deckard et al 1987). Increasing grain yield and yield stability are of primary importance for wheat breeders due to the increasing demand for this grain. However, because the relationship between grain yield and the quality among cultivars is generally negative, maintenance of adequate breadmaking quality places some constraints on the improvement of yield potential.

A comparison of cultivars released over the past 40 years by the NDSU breeding program could determine whether end-use quality improvement has been made. Determining genetic gain, or lack thereof, in quality traits can help researchers consider strategies for future improvements in crop quality.

This study was conducted to assess genetic variation in quality traits of HRSW cultivars released by NDSU since 1968 that have been grown in North Dakota and neighboring states. Specific objectives were to 1) determine whether quality traits have been maintained during the past 40 years, 2) examine the gain or loss achieved in quality traits resulting from breeding efforts, and 3) observe correlations between quality traits.

MATERIALS AND METHODS

Procedures

Twenty-six HRSW cultivars released over the past 40 years from the NDSU HRSW breeding program, three NDSU experimental lines with the potential for future release, and three widely grown cultivars in North Dakota from other breeding programs were included in this study (Table I). The cultivar 2375 was released by Pioneer HiBred in 1990, Briggs was released by the South Dakota Ag Experiment Station in 2002, and Hanna was released by AgriPro in 2002. Also, the Canadian cultivar Marquis, released in 1911, one of the first cultivars widely grown in North Dakota, was included for comparison purposes.

Experiments were conducted at three locations in 2004 and two locations in 2005. In 2004, experiments were conducted at the Dalrymple Experiment Plots near Casselton, ND; at Carrington Research Extension Center near Carrington, ND; and at a cooperator’s farm site located south of Lisbon, ND. In 2005, experiments were conducted at the Prosper Research Site near Prosper, ND, and at the Carrington Research Extension Center. The sites were representative of the eastern (Casselton and Prosper), eastcentral (Carrington), and south-eastern (Lisbon) regions of North Dakota. The soils at the Casselton and Prosper sites were a Beardon (fine-silty, mixed, superactive, frigid, Aerie Calciaquolls)-Perella (fine-silty, mixed, superactive, frigid, Typic Endoaquolls) association with a 0-1% slope. At Carrington, soils were a Heimdal (coarse-loamy, mixed, superactive, frigid, Calcic Hapludolls)-Emrick (coarse-loamy, mixed, superactive, frigid, Pachic Hapludolls) association with a 0-3% slope. Soils at Lisbon were a Barnes (fine-loamy, mixed, superactive, Udic Haploborolls)-Svea (fine-loamy, mixed, superactive, Pachic Udic Haploborolls) association with a 0-3% slope. At Casselton and Prosper, nitrogen (N) in the form of urea (46-0-0) was applied at 84 kg/ha during the Fall before seeding. At the Carrington site, N in the form of anhydrous ammonia was applied at 135 kg/ha the Fall before seeding. At the Lisbon site, N in the form of urea was broadcast and incorporated at 168 kg/ha before seeding. In 2004, the planting dates were 15 April at Lisbon, 17 April at Casselton, and 27 April at Carrington. In 2005, the planting dates were 3 and 5 May at Prosper and Carrington, respectively. Plots were harvested from the middle to the end of August in both years, and plants exhibited little or no noticeable shattering. Planting rates were 108 kg/ha at Casselton, Prosper, and the Carrington sites, and 135 kg/ha at the Lisbon site.

Entries were arranged in a randomized complete-block design with four replicates. Experimental units at the Casselton, Prosper, and Carrington locations were 2.4 m long by 1.2 m wide and consisted of seven rows 15.2 cm apart. At Lisbon, plots were 3.6 m long by 1.2 m wide and consisted of seven rows 15.2 cm apart.

Data Collection for Agronomic and Quality Traits

Grain samples were cleaned by using a clipper grain cleaner before yields and volume weights were measured. Grain yield (Mg/ha) was determined by weighing the cleaned grain harvested from each plot. Grain-volume weight (GVW) (kg/m^sup 3^) was measured according to Approved Method 55-10 (AACC International 2000).

Clean samples were cleaned once again on a dockage tester (Carter- Day, Minneapolis, MN) before measuring the pertinent data. Grain protein content (GPC) (g/kg) was measured according to Approved Method 46-30 (AACC International 2000) using an Infratec 1226 cold grain analyzer expressed on a 120 g/kg moisture basis and measured for each replicate. Thoroughly cleaned wheat grains on two of the four field replicates were tempered to 15.5% moisture for 16 hr before milling on a Brabender Quadromat Jr mill according to standard procedures used at the Department of Cereal and Food Sciences at North Dakota State University. The flour extraction percentage (g/kg) was calculated by dividing the flour weight of straight-grade flour over the total grain weight milled (150 g). Two replicates of each entry were ground whole for the Falling Number test using a cyclone sample mill (Udy Corporation, Fort Collins, CO). The Falling Number test (sec) was done according to Approved Method 56-81B (AACC International 2000). The Falling Number test was conducted with a 7-g sample of flour and as-is percent moisture basis.

TABLE I

List of 33 Hard Red Spring Wheat Genotypes and Year of Release, Origin, and Quality Trait Means Across Five North Dakota Environments During 2004 and 2005a

Two replicates of each entry milled into flour on the Quadromat Jr. mill were then used for the pertinent tests. The mixograph test was done using a mixogram with a 10-g bowl (National Manufacturing, TMCO Division, Lincoln NE). Water (6 mL) was added to 10 g of flour and mixed for at least 8 min. Overall mixograph scores were determined visually on a 1-8 scale in comparison with standard mixograph reference charts developed by the Plant Sciences Department at NDSU. A score of 1, 2, or 3 indicated very poor mixing strength and consistency, while a score of 7 or 8 indicated very strong dough strength and consistency. Four components were measured for each mixogram: mixogram peak time (min), mixogram peak height (cm), mixogram height after 8 min (cm), and descending slope (cm/ min). The descending slope was measured by taking the average height at peak time minus the average height 2 min later and dividing by two. The glutograph test (sec) was done according to manufacturer instructions of the Glutograph-E. This test measured the stretching and elastic properties of wet gluten and was expressed as the number of seconds it takes to stretch a total of 800 BU. The glutograph test measures gluten quality by stretching the wet gluten. A sample of the wet gluten is placed between two corrugated plates. The upper plate stands still while the lower plate rotates with a constant force. This shear stress stretches the sample more or less depending on the strength of the gluten. After wet gluten is stretched to a set deflection by the Glutograph-E, the sample is released and the glutograph score is recorded in seconds it takes to reach this point of deflection (800 BU). The stronger the gluten, the longer the time it takes to stretch 800 BU. Baking tests were conducted using flour from one of the two milled replicates. Dough was prepared for baking, noting water absorption (%), mixing time (min), and dough handling characteristics on a scale of 1-10, using a 3-hr fermentation system. The baking procedure followed the standard method used at the NDSU Plant Sciences Department. Baking was done using 25-g flour pup loaves baked at 220[degrees]C for 25 min. The bread formula consisted of 25 g of flour; mixed with a baking solution of water, 5% sugar, 3% compressed yeast, and 1% salt. Also, 1 cm^sup 3^ of DohTone enzyme supplement and 1 cm^sup 3^ of bromate- plus-phosphate were used per loaf. The finished loaves were analyzed for volume based on the displacement of canola seeds expressed in cubic centimeters. The crumb and crust colors were determined by scoring the loaves visually using a constant illumination source on a scale of 1-10 based on creamy, bright-white crumb color and a golden-brown crust color. A 1 0 score represents the creamy brightwhite crumb color and the golden-brown crust color indicates high quality.

TABLE I

List of 33 Hard Red Spring Wheat Genotypes and Year of Release, Origin, and Quality Trait Means Across Five North Dakota Environments During 2004 and 2005a

Data Analyses

Data were subjected to analysis of variance using the GLM subprogram of the Statistical Analysis System (SAS Institute, Cary, NC). Within the model, genotypes were considered fixed effects, and environments and blocks were considered random effects. The genotype- by-environment mean square was used as the denominator when testing the level of significance for genotypes. A level of significance of 95% was used on all statistical analyses. Error variances were homogeneous among the five environments, so a combined analysis of variance was conducted.

Means were separated using an F-protected LSD procedure. Correlations between all quality traits were calculated using combined data by pooling the homogeneous correlation coefficients from each environment. Regression analysis using year as the independent variable on individual environment means and overall combined means was done to determine the level of annual progress made for a particular trait over the past 40 years.

Marquis and Glupro cultivars were omitted from the statistical analysis (their overall means across environments for each trait are still shown in Table I). Marquis was omitted because it was released 57 years before the next oldest cultivar in this study. Glupro (a cultivar derived from a cross with T. dicoccoides) was omitted due to its poor agronomic and high protein characteristics.

TABLE II

Mean Squares and Significance for Quality Traits of 33 Hard Red Spring Wheat Cultivars/Lines Grown Over Five North Dakota Environments During 2004 and 2005a-c

TABLE III

Mean Squares and Significance for Baking Traits Over Five North Dakota Environments During 2004 and 2005a-c

TABLE IV

List of 33 Hard Red Spring Wheat Genotypes, Year of Release, and Mixograph Component Means Across Five North Dakota Environments During 2004 and 2005(a,b)

RESULTS

Environmental Conditions and Data Analyses

Environment had a significant effect on GPC, mixogram peak height, mixogram height after 8 min, descending slope, and glutograph scores for quality traits (Table II). Environment had a significant effect on all baking traits except for crust color (Table III). Casselton 2004 and Carrington 2005 produced the highest quality grain. Compared with environments in 2004, disease levels were higher in 2005 environments, particularly leaf diseases and Fusarium Head Blight. Higher disease levels in 2005 not only caused significant losses in grain yield, but it also substantially affected agronomic and quality traits. Consequently, in 2005, loaf volume, mixing time, grain yields, and GVW were lower than in 2004. However, Falling Numbers, water absorption, and dough-handling characteristics were substantially higher in 2005. In 2004, high flour-extraction yield and mixing time were recorded at Casselton. In 2005, Carrington had the highest GPC and mixograph scores. Table IV shows the mixograph component means for the 33 cultivars/lines. The annual rates of improvement for the different quality traits calculated for each individual environment were variable (Table V).

A significant genotype-by-environment interaction was identified for GPC, mixogram peak time, mixogram peak height, mixogram height after 8 min, and glutograph scores across all environments (Table II). Genotypes differed significantly for all the quality and breadmaking traits studied except dough character score and crust color (Table III). Table VI summarizes the correlations among the quality traits.

Grain Quality Traits

Mean GPC over five environments was 147.2 g/kg (Table I). Cultivars released before 1980 had a mean GPC of 148.4 g/kg, cultivars released between 1980 and 1989, between 1990 and 1999, and the “modern cultivars,” referring to those released after 1999, had a mean of 145.0, 144.3, and 150.3 g/kg, respectively. Among the 10 highest GPC genotypes, seven genotypes belonged to the modern group. This includes four cultivars from NDSU (Alsen [Frohberg et al 2006], Dapps and Steele-ND [Mergoum et al 2005], Glenn [Mergoum et al 2006]), the SDSU cultivar Briggs, and two NDSU experimental lines (ND 751 and ND 802).

TABLE V

Environment Means, Linear Regression Coefficients on Year of Release (b), and Proportion of Entry Sums of Squares by Linear Regression for 15 Quality Traits Using 31 Hard Red Spring Wheat Cultivars/Lines Grown in Five North Dakota Environments During 2004 and 2005a,b

GPC has been maintained with a slight increase of 0.08 g/kg/yr since 1968 (Table V). The gain in GPC varied significantly with environments, ranging from -0.03 to 0.21 g/kg/yr. The Carrington 2005 environment was the only one to show a significant positive regression coefficient for the grain protein content with year of release. In general, the drier environments produced higher GPC and lower flour extraction yields. Excluding Glupro, Dapps had the highest grain protein percentage in four environments, while Coteau had the highest GPC in the other environment. Grain protein content showed a significant and positive correlation with mixogram scores, mixogram height after 8 min, and descending slope (Table VI). Coteau, Dapps, Steele-ND, and Glenn showed a significant increase in grain protein content compared with Waldron, released in 1968 (Table I).

Mean flour-extraction yield over the five environments was 684.9 g/kg (Table I). Over all environments, the flour extraction yields have been maintained with a small positive value of 0.15 g/kg/yr since 1968 (Table V). The mean value for annual gain in flour extraction yield varied significantly with environments (from -0.87 to 0.97 g/kg/yr). At Lisbon, a significant negative regression coefficient for flour-extraction yield and year of release was observed. However, a significant positive coefficient was recorded at Prosper. Flour extraction yield was positively correlated with mixogram peak height (Table VI).

The mean Falling Number over the five environments was 474 sec (Table I). Cultivars released before 1980 had a mean Falling Number of 507 sec; while those released between 1980 and 1989, 1990 and 1999, and the modern cultivars had a mean of 476, 447, and 473 sec, respectively. A slight, but nonsignificant decrease was noted for Falling Number of 1.51 sec/yr since 1968 (Table V). Mean annual gain for Falling Number varied significantly among environments (from – 2.44 to 1.27 sec/yr). Data from Carrington 2004 and Prosper 2005 showed a significant negative regression coefficient for Falling Number means with year of release, while data from Carrington 2005 showed a significant positive coefficient. Falling Numbers were not correlated with any other quality traits (Table VI). A total of 11 genotypes had a significant lower Falling Number than Waldron (Table I).

The mean mixogram score over the five environments was 5.6 (Table I). A 1-8 visual scale established by the NDSU Cereal Science Laboratory was used to score the mixograph test. This scale was established in comparison with standard mixograph reference charts. Based on this scale, the higher score indicates stronger dough strength. This score is a simplification and combination of all mixograph information such as mixograph peak time, peak height, and tolerance. Mixogram scores slightly increased by 0.01/yr since 1968 (Table V). Mean annual gain for mixogram scores varied with environments ranging from 0.00 to 0.02/yr. Prosper 2005 was the only environment to show a significant positive regression coefficient between the mixogram score and year of release. NDSU genotypes Dapps, Glenn, and ND 751 exhibited the highest mixogram scores consistently across all environments. The mixogram scores showed a positive correlation with GPC, glutograph scores, mixogram peak height, mixogram height after 8 min, and descending slope (Table VI). The mixogram reference score was correlated mostly with mixogram peak height and mixogram height after 8 min. A total of 11 cultivars among the 30 genotypes showed a significant increase in mixogram scores compared to Waldron (Table I). The mean mixogram peak time over the five environments was 3.4 min, the mixogram peak height was 5.8 cm, the mixogram height after 8 min was 5.0 cm, and the descending slope was 0.46 cm/min (Table IV). A total of 21 genotypes had a longer significant mixogram peak time than Waldron. Excluding Glupro, eight of 10 highest mixogram peak heights were for genotypes released in 1999 or later. This included all five NDSU released cultivars (Alsen, Dapps, Steele-ND, Glenn, and Howard [Mergoum et al 2006]), and the three NDSU experimental lines (ND 751, ND 802, and ND 803). A total of 11 genotypes had a significantly higher mixogram peak height than Waldron. Similarly, a total of 12 genotypes had a significantly higher mixogram peak height after 8 min than Waldron. Among the genotypes released after 1999, seven had the highest descending slope value, including all five NDSU released cultivars and NDSU experimental lines ND 802 and ND 803. Five genotypes had a significantly larger descending slope value than Waldron. Data from all five environments shows that there was no change in mixogram peak time, mixogram peak height, mixogram height after 8 min, and descending slope since 1968 (Table V). The NDSU experimental line ND 751 consistently had the highest mixogram peak time across all environments while Glenn consistently had the highest mixogram peak height and mixogram height after 8 min. The NDSU experimental line ND 802 consistently had the highest descending slope value across all environments.

The mean glutograph score over all environments was 60.7 sec (Table I). There was no trend between gluten strength and year of release (Table V). The mean annual gain in gluten strength was from – 0.51 to 0.17 sec/yr, with no significant regression between the glutograph scores and year of release. Len and ND 751 had the highest glutograph scores across all environments. Glutograph scores were positively correlated with mixogram scores, mixing time, and mixogram peak time (Table VI). Eleven genotypes had a significantly stronger glutograph score than Waldron (Table I).

Breadmaking Characteristics

The mean water absorption over the five environments was 61.2% (Table I) with no change since 1968 (Table V). The mean change in water absorption ranged from -0.03 to 0.04%/yr, with no significant regression coefficient between water absorption and year of release. Glenn and ND 803 showed the highest water absorption percentages consistently across all environments. These two genotypes absorbed significantly more water than Waldron (Table I).

TABLE VI

Genotypic Correlation Among Quality Trait Means of 31 Hard Red Spring Wheat Cultivars/Lines Released Between 1968 and 2006 Grown in Five North Dakota Environments During 2004 and 2005a-c

The average dough character score over all environments was 9.3 (Table I). Eight among the 16 highest dough character genotypes were released after 1999. This includes four NDSU cultivars (Alsen, Dapps, Steele-ND, and Glenn), the SDSU cultivar Briggs, the Agripro cultivar Hanna, and two NDSU experimental lines (ND 751 and ND 803). Overall, there were no changes in dough characteristic scores since 1968 (Table V). Mean annual gain in dough character varied from – 0.01 to 0.04/yr, with no significant regression coefficients with year of release.

Mean loaf volume over all environments was 1 89.5 cm^sup 3^ (Table I). Cultivars released before 1980 had a mean loaf volume of 186.0 cm^sup 3^, and those released between 1980 and 1989, 1990 and 1999, and 2000 or after, had mean values of 186.5, 191.1, and 188.8 cm^sup 3^, respectively. Overall, there were no significant changes in loaf volume achieved since 1968 (Table V). The mean annual gain in loaf volume ranged from 0.09 to 0.32 cm^sup 3^/yr. Prosper 2005 was the only environment to show a significant regression coefficient between loaf volume and year of release. The cultivar Glenn and the experimental line ND 751 consistently had the highest loaf volume across all environments. Loaf volume was positively correlated with crumb color, mixing time, and mixogram peak time (Table VI). A total of seven genotypes had a larger significant loaf volume than Waldron (Table I).

On a 1-10 scale, with 1 being the worst and 10 being the best crumb color, mean crumb color score over all environments was 7.9 (Table I). Over all five environments, there was a positive correlation between the year of release with crumb color (Table VI). Cultivars released before 1980 had a mean crumb color of 7.5, while those released between 1980 and 1989, 1990 and 1999, and the modern cultivars had mean values of 7.8, 7.9, and 8.1, respectively. Six among the 10 highest-scored genotypes for crumb color were released after 1999. This includes Alsen, Dapps, Glenn, Hanna, ND 751, and ND 803 (Table I).

Over the five environments, a significant increase in crumbcolor score of 0.02/yr since 1968 occurred (Table V). This translates into an annual mean gain in crumb color of 0.4%/yr since 1968. Mean annual gain for crumb color varied with environment, ranging from 0.01 to 0.03/yr. In 2004, there was a significant regression coefficient for crumb color score at all locations. Alsen, Dapps, Glenn, and ND 751 showed the highest crumb color scores across all environments. Crumb color score was positively correlated with loaf volume (Table VI) and GVW (r = 0.62, P

The overall mean of mixing time was 3.1 min (Table I) with no significant change in mixing time observed since 1968 (Table V). The annual mean gain in mixing time varied from -0.01 to 0.01/yr, with each environment showing no significant regression coefficient between mixing time and year of release. Mixing time was positively correlated with glutograph score, loaf volume, and mixogram peak time (Table VI). Ten genotypes had a significantly longer mixing time than Waldron (Table I).

Grain Yield and Grain-Volume Weight (GVW) Results

Grain yield and GVW overall and entry means are shown in Table I to help identify the gain for these agronomic traits during the past 40 years. However, interrelationships among and ANOVA for each of the agronomic traits are presented elsewhere (Underdahl et al 2008). Grain yield increased from 2.79 to 4.21 Mg/ha since 1968 (Table I), equal to an annual increase of 30.4 kg/ha/yr since 1968 (data not shown). This represents an annual gain in grain yield of 1.3%/yr. The annual increases in grain yield ranged from 15.3 to 60.0 kg/ha/ yr depending on the environment. Over five environments, GVW increased significantly by 1 .25 kg/m^sup 3^/yr since 1968 (data not shown). This amounted to a mean annual gain in GVW of 0.2%/yr since 1968. Increases were significant for each environment but varied from 0.73 to 1 .95 kg/m/yr.

DISCUSSION

Within modern adapted cultivars, it is common to observe a negative correlation between grain yield and GPC. We did not observe a significant negative correlation between grain yield and GPC, even though grain yield was substantially higher among the newer cultivars/lines. We found that GPC did not decrease but has remained the same since 1968 (Table V). This finding differed from previous reports that showed that the newer, higher-yielding genotypes had lower protein concentrations (Cox et al 1989; Souza et al 1993). Even though GPC was not significantly associated with release year, simply maintaining the same GPC is an excellent achievement considering grain yield improved by 51% since 1968. Therefore, our findings seem to support the results of Cox et al (1989), who suggested that GPC tends to be negatively correlated to yield, but the correlation is not strong enough to inhibit simultaneous improvement in both grain yield and GPC.

Correlations between GPC and other quality traits in our study agree with Guttieri et al (2000) and Graybosch et al (1996), who reported that as GPC increases, mixograph scores also increase (Table VI). Similar to our results, Souza et al (1993) and Cox et al (1989) reported no significant change in flour yield over years of release in both spring and winter wheat grown in the Pacific Northwest and central Great Plains, respectively. Flour extraction yield in spring wheat grown in Idaho was positively correlated with mixogram peak height (r = 0.42, P

We found that the Falling Numbers in our study decreased by 1.51 sec/yr, which was not a significant change. Falling Numbers in this study had negative correlations with loaf volume (r = -0.25), mixing time (r = -0.24), and mixogram peak time (r = -0.24) (Table VI), which suggests that even though Falling Numbers are decreasing, the observed change did not significantly affect the quality parameters, as all genotypes had acceptable Falling Number values.

Souza et al (1993) found that mixograph peak time, peak height, and mixing tolerance increased with time among HRSW cultivars released between 1911 and 1990 in the Pacific Northwest region of the United States. Mixogram scores and mixograph components in our study all remained relatively constant. The consistency in mixogram components shows that the HRSW breeding program has continued to select for a certain mixograph profile that meets the baking industry requirements in the United States and overseas. Also, mixogram visual reference charts seem to be a reliable method for quick and accurate scoring. Similar to results found in this study, Souza et al (1993) found that the mixograph height was positively correlated with flour protein and flour yield. Breadmaking quality traits have also been maintained since 1968 (Tables I and IV). The results from this study found water absorption, dough character score, and loaf volume have remained steady over the past 40 years. This result differs from previous findings by Cox et al (1989) and Souza et al (1993), who reported that water absorption and loaf volume were improved among modern cultivars grown in Kansas and Idaho, respectively. Similar to our results, Souza et al (1993) also reported a positive correlation between loaf volume and crumb color. Souza et al (1993) and He and Hoseney (1992) reported that loaf volume in general depends on flour protein content. Data from our study did not support this relationship.

This study showed that crumb color score has significantly improved by 0.4%/yr since 1968, with no change in crust color score or mixing time. Previous studies have also reported that crumb color has improved in the modern released cultivars (Cox et al 1989; Souza et al 1993). Previous work by Souza et al (1993) had reported correlations between crumb color appearance and the mixogram peak height and loaf volume. The results from this study showed only a correlation between crumb color appearance and loaf volume.

The results from this study on quality suggest that there was no decline in overall quality traits of HRSW cultivars grown over the past 40 years. This agreed with Souza et al (1993), who suggested the results of a quality study disagree with the milling and baking industry observations of declining quality. Cox et al (1989) also saw no evidence of a decline in end-use quality for hard red winter wheat cultivars. The same study (Cox et al 1989) suggested the deterioration in quality of hard red winter wheat that is perceived by the baking industry must be caused by other, nongenetic factors such as environmental changes, milling practices, or commercial baking formulations.

CONCLUSIONS

Selection for quality traits as well as agronomic traits and disease resistance in the HRSW breeding programs at NDSU and other breeding programs has led to the maintenance in quality traits, better agronomic performance, and better disease resistance among recently released cultivars. The results from this study on quality determined that 1) no evidence of a decline over time has occurred in the improvement of end-use quality attributes for HRSW genotypes, even though agronomic traits have been improved in the past four decades; 2) overall, significant increases were observed in crumb grain appearance scores since 1968; 3) GPC, flour-extraction yield, mixogram scores, water absorption, dough character scores, loaf volume, and mixogram peak height have been maintained. Although these traits have not significantly increased, they were a step in the positive direction. Many of these quality traits are already considered very good and their improvement will likely be difficult. Considering the level of agronomic improvement between 1968 and 2006, the maintenance and improvement of the quality and breadmaking traits should be considered a great accomplishment by the spring wheat breeding programs in the region in general and at NDSU in particular.

ACKNOWLEDGMENTS

This work is dedicated to James Faller, who passed away recently, for his dedication and continuous support to accomplish this work and all other research projects at the HRSW breeding program at NDSU. We would like to extend our deep gratitude to the NDSU HRSW staff for all their help and support to carry out this work. Many thanks to Truman Olson and the spring wheat quality lab, as well as Deckard, Meyer, Elias, Berzonsky, Simsek, and many other faculty members, who reviewed or provided many constructive and pertinent suggestions to improve the quality of this research.

Cereal Chem. 85(4):507-514

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Underdahl, J. L., Mergoum, M., and Ransom, J. K. 2008. Agronomic traits improvement and associations in hard red spring wheat cultivars released in North Dakota from 1968 to 2006. Crop Sci. 48:158-166.

[Received November 19, 2007. Accepted January 3, 2008.]

J. L. Underdahl,1 M. Mergoum,1,2 B. Schatz,3 and J. K. Ransom1

1 Dept. Plant Sciences, North Dakota State University, Fargo, ND 58105.

2 Corresponding author. Phone: (701) 231-8478. Fax: (701) 231- 8474. E-mail: Mohamed.Mergoum@ndsu.edu

3 NDSU Carrington Research Extension Center, Carrington, ND 58421.

doi: 10.1094/CCHEM-85-4-0507

(c) 2008 AACC International, Inc.

Copyright American Association of Cereal Chemists Jul/Aug 2008

(c) 2008 Cereal Chemistry. Provided by ProQuest Information and Learning. All rights Reserved.




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