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Published online 1 January 2005
Published in Crop Sci 45:77-84 (2005)
© 2005 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
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Published in Crop Sci. 45:77-84 (2005).
© 2005 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA

CROP BREEDING, GENETICS & CYTOLOGY

Agronomic and Quality Characteristics of 1AS.1AL-1DL Translocation Lines of Durum Wheat Carrying Glutenin Allele Glu-D1d

Daryl L. Klindwortha,*, Gary A. Harelanda, Elias M. Eliasb and Steven S. Xua

a USDA-ARS, Northern Crop Science Lab., P.O. Box 5677, State Univ. Stn., Fargo, ND 58105
b Dep. of Plant Sciences, North Dakota State Univ., Fargo, ND 58105

* Corresponding author (klindwod{at}fargo.ars.usda.gov).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Markets for durum wheat (Triticum turgidum L. var. durum) could be expanded if cultivars with dual-purpose end-use could be developed. The Glu-D1d allele, located on chromosome 1D of bread wheat (T. aestivum L.), encodes for high-molecular-weight glutenin subunits 1Dx5 and 1Dy10, and this allele is highly desirable for good baking quality. Lines of durum carrying Glu-D1d on a 1AS.1AL-1DL translocation chromosome and also segregating for the low-molecular-weight I (LMWI; weak gluten) or low-molecular-weight II (LMWII; strong gluten) allele of Glu-B3 were available for this study. Our objective was to test the agronomic and baking quality of the 1AS.1AL-1DL translocation lines. The translocation lines in a ‘Renville’ background, and carrying either the LMWI or LMWII banding patterns, were grown in yield trials conducted at two North Dakota environments from 1998 through 2002. Grains from translocation lines were milled and mixing and baking characteristics were determined. Grain yield of translocation lines were lower than that of Renville, but the two highest yielding translocation lines were similar to Renville for lodging score, heading date, and plant height. The translocation lines had reduced 1000-kernel weight and a significant genotype x environment interaction for farinogram characteristics. Compared with Renville, mean loaf volumes were not improved. Translocation lines having LMWI had better mixing stability and loaf volume than lines having LMWII. While the results suggest agronomic traits can be sufficiently improved, commercial production of the translocation lines may not be feasible without more consistent mixing traits and improved baking characteristics.

Abbreviations: HMW, high molecular weight • LMW, low molecular weight • MTI, mixing tolerance index


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
IN RECENT YEARS, plant-breeding objectives have included development of crop cultivars with dual-purpose end-use. In hexaploid wheat, this has included efforts to develop wheat with good baking quality for domestic markets and good noodle quality for Asian markets (Lang et al., 1998). Durum wheat has traditionally been used for pasta products in the domestic American markets, although its use in baked goods is common in southern Italy, the Middle East, and North Africa (Boggini et al., 1995; Boyacioglu and D'Appolonia, 1994). Consequently, studies of bread-making quality of durum wheat have been reported by several authors, including Boggini and Pogna (1989), Boggini et al. (1995), Liu et al. (1996), Ammar et al. (2000), and Marchylo et al. (2001). Durum cultivars with both good pasta-making and bread-making quality would be an advantage to increase market demand for durum products.

Wheat flours are composed of many protein, carbohydrate, and lipid components that contribute to quality. While glutenin proteins are considered the most important components for good quality in durum and hexaploid wheat, the glutenins most responsible for good quality differ in the two species. In hexaploid wheat, the high-molecular-weight (HMW) glutenins are most responsible for good bread-making quality, and of these, the glutenin subunits encoded by the Glu-D1d allele are considered the best (Payne et al., 1984; Shewry et al., 1992). This allele codes for HMW subunits 1Dx5 and 1Dy10 (5+10) and is located on chromosome arm 1DL. In durum wheat, the low-molecular-weight (LMW) glutenin subunits encoded by the Glu-B3 gene and located on chromosome arm 1BS are most responsible for good pasta quality (Ciaffi et al., 1991; Brites and Carrillo, 2001). Together, the Glu-B3, Glu-A3, and Glu-B2 genes condition several LMW banding patterns, including the LMWI and LMWII patterns (Nieto-Taladriz et al., 1997). The LMWI type produces weak gluten, whereas the LMWII type produces strong gluten that is highly desirable for good pasta qualities. Because good pasta- and bread-making qualities are imparted by different genes, transfer of Glu-D1d to durum may result in good baking quality without loss of pasta-making quality imparted by LMWII (Glu-B3).

Manipulation of the Glu-D1 locus has been suggested as a means to improve baking quality of hexaploid wheat. Rogers et al. (1990) studied the glutenin and gliadin in nulli-tetrasomic lines of ‘Chinese Spring’ to determine dosage effects of glutenin genes. They found that chromosome 1D, carrying Glu-D1a (subunits 1Dx2 and 1Dy12), had the biggest positive effect on baking quality, whereas chromosome 1A, carrying Glu-A1c (a null allele), had a negative impact on quality. They proposed increasing the dosage of Glu-D1d and reducing the dosage of the null allele of Glu-A1c to improve baking quality.

One approach to introducing the Glu-D1d allele into related species is through chromosome substitution or translocation. Lukaszewski and Curtis (1992) produced a 1R.1D translocation to transfer Glu-D1d to triticale (xTriticosecale Wittmack). Additionally, Lukaszewski and Curtis (1994) induced 1A.1D translocations carrying Glu-D1d in ‘Rhino’ triticale. Ballesteros et al. (2003a) reported the development of both a 1D(1A) and 1D(1Hch) substitution and a 1DL.1HchS translocation in tritordeum (xTritordeum Asch. et Graebn.). A substantial improvement in baking quality was observed in the tritordeum substitution lines (Ballesteros et al., 2003b). In durum wheat, Liu et al. (1995) reported improvement in baking quality in ‘Langdon’ substitution lines carrying the Glu-D1a allele. However, because the Langdon 1D(1A) and 1D(1B) substitution lines have reduced yield, they are not practical for production purposes.

To mitigate effects of chromosome 1D on agronomic traits, at least four groups have attempted to produce durum translocation lines carrying the Glu-D1d allele. Blanco et al. (2002) backcrossed the 1AS.1DL translocation carried in Rhino-6 triticale, which was produced by Lukaszewski and Curtis (1994), into a durum background. Lukaszewski (2003) also transferred the 1AS.1DL translocation from Rhino-6 triticale to durum wheat and reported that the segment of chromosome 1D that carried Glu-D1d was spontaneously transferred to chromosome 1B in two independent events. Vitellozzi et al. (1997) reported isolation of a 1AS.1AL-1DL translocation induced through ph1-mediated homeologous pairing. Joppa et al. (1998) produced 1AS.1AL-1DL translocation lines through homeologous pairing in double monosomics (13" + 1'1A + 1'1D).

While 1AS.1AL-1DL translocation lines carrying Glu-D1d have been isolated, little has been reported in the literature concerning effects of the translocation on agronomic and quality traits. Joppa et al. (1998) reported the results of a preliminary study on baking quality in 1AS.1AL-1DL translocation lines. If cultivars carrying the 1AS.1AL-1DL translocation are to be grown commercially, information is needed on effects of the translocation on agronomic traits, especially yield, and detailed studies of baking quality are needed. The objective of our study was to provide information on these traits using advanced generation lines selected from the breeding materials reported by Joppa et al. (1998). In addition to carrying the 1AS.1AL-1DL translocation, the lines reported by Joppa et al. (1998) did not all carry the same LMW subunits. Because the Glu-B3 gene conditioning the LMWII phenotype (strong gluten) is so important for good pasta quality, we classified the translocation lines for the presence of LMWI or LMWII to test whether the LMW glutenin subunits affected baking quality of the translocation lines.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Selection of Translocation Lines
Joppa et al. (1998) reported development of 16 F4 families of 1AS.1AL-1DL translocation lines having the pedigree Langdon1D(1A)/Len//Langdon/3/2*Renville. With the objective of producing advanced generation translocation lines, we selected 12 families in the field for vigor and similarity to Renville for plant ideotype. Ten spikes were randomly harvested from each family. Two F5 seeds from each spike were planted in a greenhouse. Selections were made for vigorous plants that phenotypically resembled Renville in plant height, maturity, chaff color, and spike morphology. From the 218 mature plants, we harvested 120 F5 families. The HMW and LMW banding pattern of the 120 F5 families was determined as described in the electrophoretic procedures.

Because of greenhouse space restrictions, we could rapidly increase only four of the 120 families for initial yield trials. We made selections among the 120 F5 families for seed yield and large, plump kernels. Four plants, identified as L092, L147, L232, and L252, were increased in the greenhouse and advanced to yield trials in 1998–1999. To sample a broader portion of the variability within the population of translocation lines, we grew all 120 F5 families in the field in 1998 and selected spikes from vigorous plants having good seed set. Seventy-two translocation lines, identified as S99B1 thru S99B70, L092, and L252, were grown in a single-replication, single-row yield trial in 1999 and in a replicated yield trial in 2000 using procedures described below. Because of poor yields and lodging susceptibility, we selected only 14 of these 72 lines for quality testing. In summary, the quality tests included four translocation lines for years 1998-1999, and 14 translocation lines for years 2000 through 2002. Only L092 and L252 were present in all 5 yr of testing.

Electrophoretic Procedures
All of the original 12 F4 families from which we selected spikes were known to be homozygous for the 1AS.1AL-1DL translocation. Most were also known to be homozygous for either LMWI or LMWII banding pattern. Whenever possible, we assigned the LMW glutenin composition to the 120 newly selected F5 families on the basis of its parental data. For segregating parental lines, kernel halves were squashed with a hammer and the proteins analyzed by SDS-PAGE using the procedure of Singh et al. (1991). Within some segregating families, three LMW banding patterns were observed (Fig. 1) . Families having the LMWI and LMWII banding patterns had three bands in the LMW region of the gel. To distinguish the LMWI (Fig. 1, Lanes 5, 6, and 9) from the LMWII (Fig. 1, Lanes 7, 8, and 10) types, the upper band in the LMW region was particularly useful. In the LMWII type, the upper band was broader and stained more intensely than the other LMWII bands in the same lane or the upper band of the LMWI type. The upper band of the LMWI type was narrow and stained less intensely than the other LMWI bands in the same lane. The lower band in the LMW region was also diagnostic for LMWI vs. LMWII. In the LMWII type, the lower band had slightly faster mobility than the lower band of the LMWI types. The third banding pattern observed was similar to the banding pattern that was observed in Len (Fig. 1, Lanes 2–4). We saved only those families that were similar either to Langdon (LMWI) or Renville (LMWII). We tested six seeds per family and classified families as homozygous LMWI or LMWII if all six seeds produced the proper banding pattern. From these tests, we determined that all the translocation lines in yield trials had the LMWII banding pattern except for L147, L252, and S99B19, which had the LMWI pattern.



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  		Fig. 1. Electrophoregram displaying high (HMW) and low molecular weight (LMW) banding patterns of 1AS.1AL-1DL translocation lines. Lane 1 is Len Hard Red Spring Wheat carrying HMW bands 2*, 5, 7, 9, and 10; Lanes 2-8 are 1AS.1AL-1DL translocation lines carrying HMW bands 5, 6, 8 and 10 and LMW banding patterns of Len (Lanes 2-4), LMWI (Lanes 5-6),and LMWII (Lanes 7-8); Lane 9 is Langdon (LDN) carrying HMW bands 6 and 8 and LMWI pattern; and, Lane 10 is Renville (RNV) carrying HMW bands 6 and 8 and LMWII pattern. In the HMW region of the gel, arrows in Lane 1 point to HMW bands 5 and 10 in Len. In the LMW region of Lane 10, arrows point to the two LMW bands in Renville that are diagnostic for the LMWII banding pattern.

 
Yield Trials
Yield trials of the translocation lines were conducted at Fargo (1998 through 2002), Casselton (1998 and 2000), and Prosper, ND (1999, 2001, and 2002). The experimental design was a randomized complete block with four replications in each year except 2000, where there was only sufficient seed from the 1999 increase to plant three replications. The soil series at Fargo is a Fargo silty clay (fine, montmorillonitic, frigid Vertic Haplaquoll). The soil at Prosper and Casselton is a Perella-Bearden silty clay loam complex. Perella is a fine-silty, mixed, frigid Typic Haplaquoll and Bearden is a fine-silty, frigid, Aeric Calciaquoll. Planting dates of the 10 trials were between 3 and 22 May. The planting rate was 40 kernels per meter of row. Experimental units consisted of four-row plots, 3.2 m long, and rows that were 30 cm apart.

Durum cultivars included in the trials as checks for agronomic traits were Renville and Langdon in 1998–1999, and Renville, Ben, Monroe, Lebsock, Rugby, and Maier in 2000 through 2002. ‘Len’ hard red spring wheat was included in the trials in all years as a baking quality check. Data were collected for yield, heading date, plant height, lodging, and culms per meter of row. Yield was measured on a whole-plot basis. Heading date was recorded as number of days past 30 June when 50% of the culms had spikes completely emerged. Lodging was scored on a 0-to-9 scale (0 = no lodging and 9 = 100% lodging). Plant height was measured as the distance from the ground to the tip of the apical spikelet, with awns excluded. The number of culms per meter was determined by counting the number of culms in one of the central rows. While two trials were planted in 2001, the Prosper trial was abandoned because of an unusually heavy rainfall at flowering, which resulted in severe lodging in even the most lodging-resistant cultivars, and low yields and kernel weight. Although yields at Fargo in 2001 were good and lodging was not severe, test weights were low and the samples were not milled.

Quality Tests
Four 1AS.1AL-1DL translocation lines in 1998–1999 and 14 translocation lines in 2000 and 2002 were tested for quality traits. Renville and Len were included as quality checks. Because there was only sufficient seed produced from a three- or four-replication yield trial to conduct a single replication of quality traits, each sample was prepared by taking equal portions of grain from each replication. Tests of cleaned samples followed AACC approved methods (AACC, 2000). Data collected included test weight, 1000-kernel weight, wheat protein, wheat ash, and falling number. Samples were milled in a Bühler mill (AACC Method 26-41). Dough mixing traits were characterized on the farinograph (AACC Method 54-21). Baking quality was evaluated using an optimized straight-dough bread-baking procedure (AACC Method 10-10B). Baked loaf weight was 100 g in 1999 and 2002. Because of low flour yields, 25-g samples of loaves were baked in 2000; and samples were not baked in 1998.

Statistical Tests
Agronomic data from individual environments were analyzed as randomized complete blocks by Statistix (Analytical Software, 1998). For analysis of agronomic data combined across environments, the SAS Proc GLM (SAS Institute, 1999) procedure was used. The main effects were entry and environment, and were treated as fixed effects and random effects, respectively. The entry main effect was tested by the mean square for the entry x environment interaction. Means were separated by least significant difference (LSD). Because there was only a single replication of data for quality traits from each environment, quality traits of the 14 translocation lines and two check cultivars were analyzed by Proc GLM, with environments treated as replications, and main effects being entries and years, with entries being a fixed effect and years being random. Because strong gluten durum wheat, conferred by LMWII, is so important for durum quality, we also analyzed quality traits by classifying the translocation lines for LMW-class. Two translocation lines having LMWI were placed into a LMWI class, and the 12 translocation lines having LMWII were placed into a LMWII class. So that comparisons could be made to the checks, Renville and Len were each placed into a separate class. The quality data were then re-analyzed with LMW-class as a fixed effect and years as a random effect. The LMW-class mean squares were tested with the LMW-class x years mean square as the error term. Means were separated by LSD. A separate analysis of the quality data was also conducted for each year, with the experimental design being a RCBD and treating environments as replications


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
In the trials of the four translocation lines studied in 1998–1999, both the entry and entry x environment effects were highly significant (Table 1). Renville had a mean yield of 336.1 g m–2, while L092, the highest yielding translocation line, yielded 303.8 g m–2. From the analyses of individual environments, we found that three translocation lines were significantly lower in yield than Renville at all environments (means not shown). However, at two environments, L092 did not differ significantly from Renville for yield. It was because of the poor yield performance of these translocation lines that the additional translocation lines were selected in 2000 to determine if lines having better yielding ability were present in the original population.


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  		Table 1. Analysis of variance and mean yields of three check cultivars and four 1AS.1AL-1DL translocation lines of durum tested at Fargo (1998–1999), Casselton (1998), and Prosper, ND (1999).

 
Analyses of variance for five agronomic traits tested in 2000 through 2002 are shown in Table 2. Entry effects were highly significant for all five characters; however, the entry x environment interactions were also highly significant for all characters except culms per meter. The significant entry x environment interactions were mainly due to differences in magnitude rather than rank changes; therefore, means were combined over environments and tested by LSD (Table 3). Comparisons of the translocation lines with Renville and Ben were of particular interest since Renville is a parent of the lines and Ben is a widely grown North Dakota cultivar. Two translocation lines, S99B33 and S99B34, were better yielding than the remaining translocation lines. In the analysis of the five individual locations, these two lines were always among the top half in yield, with each being the highest yielding translocation line at two locations. Each did not differ significantly from Ben at three environments. Line S99B33 did not differ significantly from Renville at three locations; and, S99B34 did not differ from Renville at one location, and was significantly better than Renville at Fargo in 2000. However, in that environment, the yield of Renville was only 80.6% of Ben's yield, and the yield of Renville did not differ significantly from any of the other translocation lines. Therefore, the apparently good performance of the translocation lines at Fargo in 2000 was more a reflection of the poor performance of Renville in that environment, rather than the good performance of the translocation lines. The two lines carrying LMWI (L252 and S99B19) were among the lowest yielding entries in the trials. We concluded that while S99B33 and S99B34 had better yield than the original selections, L092 and L252, additional yield improvement is needed.


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  		Table 2. Analysis of variance for agronomic trials of 14 1AS.1AL-1DL translocation lines and seven check cultivars grown in five trials conducted in eastern North Dakota from 2000 through 2002.{dagger}

 

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  		Table 3. Agronomic means and LSD values from five trials of 14 1AS.1AL-1DL translocation lines and seven check cultivars grown in eastern North Dakota from 2000 through 2002.{dagger}

 
In general, the translocation lines tended to be later heading and had fewer culms per meter than Renville, but the best yielding lines had earlier heading dates (not significantly different from Renville), and more culms per meter than the lower yielding lines (Table 3). For lodging score, most of the lines were either better than Renville, or were not significantly different from Renville. Plant height for most lines was not significantly different from Renville.

Quality data were analyzed both on an entry basis and on a LMW-class basis. Because we are presenting means for all traits on the basis of LMW-class, only the ANOVA for the analysis of LMW-class is shown (Table 4). The year and year x LMW-class interaction could not be measured for loaf volume because of the different loaf sizes baked in different years. Constriction of loaf volume occurs in 25-g loaves. As a result, loaf volume of a 25-g loaf is less than one-fourth that of a 100-g loaf. Therefore, loaf volume data from each year were analyzed as a separate randomized complete block.


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  		Table 4. Analyses of variance of quality traits of 14 1AS.1AL-1DL translocation lines and two check cultivars grown when the translocation lines and checks are classified into four classes based on low-molecular-weight banding pattern.{dagger}

 
The analysis of quality traits on a LMW-class basis indicated nonsignificant year x LMW-class effects for 10 traits (Table 4). Of the six traits having significant LMW-class x year interactions, five were farinogram traits. A similar result was observed in the analysis based on entries rather than LMW-class, where four of the six possible farinogram traits had significant entry x year interactions (ANOVA not shown). This indicated that the lines did not perform consistently for mixing characteristics in different years. Because farinogram traits measure mixing characteristics that are interrelated (for example, longer stability usually results in longer time to breakdown), it is not surprising that these characteristics tend to behave similarly in regards to presence/absence of genotype by environment interactions.

For the LMW-class main effect, the significant LMW-class x year interactions resulted in nonsignificant differences for several of the characteristics (Table 4). Means for each quality trait for the four LMW-classes are shown in Table 5. Means for those traits having significant LMW-class effects were compared by LSD. To be useful as a baking durum, the comparisons of farinograph and baking data to Len are appropriate; but, for other quality traits, comparisons to Renville are appropriate. The translocation lines had test weights similar to Renville but had significantly lower 1000-kernel weight. Both whole wheat and flour protein of the translocation lines were higher than those of Renville, and this probably reflected the lower grain yield of the translocation lines. Flour extraction was also lower for translocation lines than that for Renville. The farinogram data indicated that the translocation lines had water absorption similar to Renville and significantly higher than Len. Though differences were usually nonsignificant, both groups had mean farinogram mixing characteristics inferior to Len, with the LMWI group being better than those of the LMWII group and better than Renville. Farinogram mixing characteristics of the LMWII group were more similar to Renville than the LMWI group. Results of bake absorptions were similar to those of farinograph absorptions. Mix times of the LMWI and LMWII groups were significantly longer than those of Renville or Len. Translocation lines had mean loaf volume lower than either check. Loaf volumes of the LMWI lines were significantly better than those of the LMWII lines, and did not differ from Renville. Loaf volume of both the LMWI and LMWII groups were significantly lower than that of Len. Carotenoid pigments imparted a slightly yellow color to the crumb.


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  		Table 5. Means and LSD tests for quality traits of 1AS.1AL-1DL translocation lines classified for low-molecular-weight banding pattern, and two check cultivars grown in eastern North Dakota from 2000 through 2002.{dagger}

 
While the LMW-class main effects were nonsignificant for four of the six farinogram traits, comparisons of the means indicated trends for mixing characteristics that were confirmed by analyzing the data as a RCBD for each year. To increase the number of years in the analysis, we have added data from L092 and L252, which were tested in 1998 and 1999. To illustrate the results, data from seven entries are presented for three traits, percent protein, farinogram stability, and loaf volume (Table 6). L252, having LMWI, had longer stability than Len in 1998 and 2000. However, both L252 and L092 had shorter stability than Len and Renville in the other two years. This observation is consistent with an entry x year interaction for farinogram stability. In contrast, relative to each other, the translocation lines performed consistently with L092 having shorter stability than L252. Loaf volume of L252 was consistently better than that of L092; but both were lower than Len. The lines S99B33 and S99B34 were the highest yielding translocation lines, and both carry the LMWII banding pattern and performed similarly to L092 in quality tests. The line S99B51, which also carries the LMWII banding pattern, was noteworthy in that it had the longest stability among all LMWII translocation lines. However, this long stability was associated with improved loaf volume only in 2002, when its loaf volume was equal to that of Renville (Table 6). S99B51 was among the lowest yielding and was the latest heading entry in the trials (Table 3).


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  		Table 6. Percent protein, dough mixing stability, and loaf volume of five 1AS.1AL-1DL translocation lines and two check cultivars grown at two environments per year between 1998 through 2002 in eastern North Dakota.{dagger}

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The Glu-D1d allele encodes for HMW subunits 1Dx5 and 1Dy10, and there has been debate over which of these two subunits conditions good baking quality (Lafiandra et al., 1993). Subunit 1Dx5 has been used to produce transgenic lines. Transgenic lines in which 1Dx5 subunits are overexpressed produce doughs that are so strong that they are unsuitable for commercial production (He et al., 1999; Rooke et al., 1999; Darlington et al., 2003); and it was hypothesized that overexpression of 1Dx5 resulted in doughs containing excessively cross-linked polymers. Subsequently, it has been hypothesized that mixing and baking qualities are influenced by the proper ratio of x:y subunits. To test this hypothesis, Butow et al. (2003) isolated and incorporated purified 1Dy10 into flour of transgenic 1Dx5 wheat. They observed that the decrease in the Dx/Dy ratio resulted in a weakening of the flour. Masci et al. (2003) observed a decrease in SDS sedimentation values in transgenic lines that overexpressed a LMW glutenin subunit, and this is further evidence that overexpression of a glutenin subunit may result in decreased quality. In our study, 1Dx5 and 1Dy10 in the translocation lines are neither overexpressed nor present in lopsided ratios. Despite this, flour of the translocation lines had excessively strong mixing characteristics in some environments. This suggests that good mixing characteristics may be controlled not only by the ratio of x:y subunits, but also by the combination and ratios of other HMW and LMW glutenin subunits, or gliadins present in the flour. This is supported by the fact that translocation lines carrying LMWI had better mixing and baking characteristics than lines carrying the strong gluten LMWII banding patterns.

The breeding of strong gluten durum cultivars, having the LMWII banding pattern and conditioned by the Glu-B3 gene, was an important contribution to improved durum quality. Marchylo et al. (2001) found that strong-gluten Canadian durum had mixing characters similar to good quality bread wheat, and yet had lower loaf volume than bread wheat. Baking formulations are known that will produce good quality bread products using up to 60% durum flour of presently grown strong gluten cultivars (Hareland and Puhr, 1998). As a consequence, commercial production of the translocation lines may not be advantageous to the market unless baked goods can be produced with 100% durum flour.

As a group, the translocation lines were inferior to Renville in yield. Both decreased tillering and kernel weight appeared to contribute to this yield reduction. However, it should still be possible to select translocation lines having acceptable agronomic traits for production. The translocation lines had only two backcrosses to Renville; therefore, despite selection for phenotypic similarity to Renville, genes from Len and Langdon are probably included in the genome of the translocation lines, and this may contribute to a yield reduction. While most of the translocation lines suffered from poor yielding ability, there were some lines with better yielding ability. The yielding ability of the population as a whole may also have been limited by a narrow genetic base. While the translocation lines were originally selected from 12 F4 families, the 14 translocation lines used in the study were derived from only six of those families.

Quality traits of the translocation lines are more problematic than agronomic traits. Translocation lines did not exhibit improved loaf volume and dough mixing characteristics were highly influenced by environment. Translocation lines having the LMWI banding pattern consistently had better mixing characteristics and better loaf volume than LMWII lines. Even in the years in which L252 (the LMWI type) had longer mixing stability than Len (1998 and 2000), loaf volumes were still lower than that for Len (Table 6). Dexter et al. (1994) found that starch damage in milled durum resulted in decreased mixing stability and decreased loaf volume. However, our results cannot be easily explained as being caused by starch damage. If starch damage were a factor in our results, then Renville should be affected similarly to the translocation lines. High absorption values are normally associated with starch damage, and the translocation lines actually had slightly lower absorption than Renville (Table 5). Also, Dexter et al. (1994) noted that the effects of starch damage decrease at higher protein levels; and, in our study, a comparison of years 2000 vs. 2002 shows that stability decreased but protein increased (Table 6).

The fact that translocation lines carrying LMWI had better baking quality than the LMWII lines suggests two possibilities. Compared to the LMWII types, the two LMWI lines had higher protein content and lower yields. Breeding of LMWI and LMWII translocation lines having equal protein content and yielding ability would answer whether the differences observed between the LMWI and LMWII translocation lines were associated with yield and protein content. Second, the better baking quality of LMWI compared to LMWII translocation lines may indicate that addition of HMW glutenin subunits 5+10 alone is insufficient to improve quality. Differences in glutenins and gliadins from other loci may affect mixing and baking quality in the 1AS.1AL-1DL translocation lines similar to having the proper ratio of Dx/Dy glutenin subunits. Because the Glu-B3 locus is closely linked to the gliadin gene Gli-B1, it is likely that the translocation lines carrying LMWII banding patterns have {gamma}-gliadin 45, while those carrying the LMWI banding pattern have {gamma}-gliadin 42. However, it is not clear that these gliadins could be the cause of the better baking quality of LMWI types vs. LMWII types in our study because it has been shown that the gliadins encoded by Gli-B1 possibly influence elasticity but do not contribute to gluten strength (Ruiz and Carrillo, 1995). Other glutenin/gliadin combinations with 5+10 (Glu-D1d) need to be considered, including those from the Glu-B1, Glu-A3, and Glu-B3 alleles. Therefore, it may still be possible to select 1AS.1AL-1DL translocation lines having good baking characteristics. But, because the market demands good pasta quality provided by strong-gluten LMWII-type cultivars, breeding of translocation lines carrying both LMWII and improved baking quality will be necessary before a dual-purpose durum can be released for commercial production.

Received for publication December 22, 2003.


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Crop Science 2005 45: xi. [Full Text]  



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D.L. Klindworth, S.S. Xu, and E.M. Elias
Registration of Four Durum Germplasms Carrying Glutenin Allele Glu-D1d on a 1AS.1AL-1DL Translocation Chromosome
Crop Sci., February 24, 2006; 46(2): 1002 - 1003.
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