SKCS Hardness Research Articles

Effects of the functional Gpc‐B1 allele on soft durum wheat grain, milling, flour, dough, and breadmaking quality

AbstractBackground and objectivesUtilization of durum wheat (Triticum turgidum subsp. durum) can be enhanced by increasing grain and flour protein content. One strategy to increase protein content is by introducing the functional Gpc‐B1 allele from wild emmer (Triticum turgidum subsp. dicoccoides).FindingsIntroduction of the functional Gpc‐B1 allele into soft kernel durum increased grain and flour protein by 17 g/kg, increased dough strength as evidenced by SDS sedimentation volume and Mixograph dough mixing parameters, and increased straight‐dough pan bread volume. When grown under arid conditions, high protein (151 g/kg) samples had decreased loaf volumes indicative of inelastic doughs. The functional Gpc‐B1 allele was associated with decreased test weight, a small increase in SKCS hardness, and a modest increase in flour ash; otherwise, milling performance was not affected.ConclusionsIntrogression of the Gpc‐B1 functional allele from dicoccoides into durum wheat can improve dough strength and breadmaking quality. The effect tends to be consistent over environments but overall, Gpc‐B1 made only a modest improvement in durum wheat breadmaking quality. Further studies with concomitant selection at other loci are needed to see the effects of Gpc‐B1 among elite germplasm.Significance and noveltyDurum wheat production and consumption will increase as bread quality improves. The functional Gpc‐B1 allele contributed to improved breadmaking quality. The present report is the first to examine the effect of this allele on breadmaking in durum wheat.

Identification and genetic characterization of extra soft kernel texture in soft kernel durum wheat (Triticum turgidum ssp. durum)

AbstractBackground and objectivesKernel texture (grain hardness) is a key determinant of wheat quality and utilization. Among soft wheats, softer kernels possess some advantages in processing and end‐product quality. Here, an extra soft kernel phenotype was identified and characterized in soft kernel durum wheat.FindingsA RIL population was developed by crossing “Soft Strongfield” with Kamut Khorasan wheat. Progeny kernels were selected for chalky appearance in the F2, F3, and F4. Kernel texture phenotypes measured by the SKCS in the F5, F6, and F7 were all less than 20 and ranged down to −12.6. Among F5:7 full‐sib RILs, there was indication of a single segregating genetic locus that was associated with a difference of about 7 SKCS hardness index (HI) units. Single marker–trait association and composite interval mapping both identified significant QTLs on chromosomes 4B and 1B with phenotypic effects of about 5 and 4 HI, respectively.ConclusionsQTL detected in the present study may be used to reduce kernel texture in soft durum to below zero, creating “extra soft” durum. These QTLs should also be available to be used in hard kernel durum to reduce kernel texture and may be transferrable to hexaploid wheat.Significance and noveltyThe creation of soft kernel durum wheat expanded the processing, end‐product quality, and utilization of durum wheat. A further reduction in kernel softness may expand further durum wheat's importance as a global food.

Compressive strength of Super Soft wheat endosperm

Wheat endosperm texture (hardness) largely determines end-product suitability. Since its development 25 years ago, the single kernel classification system (SKCS, a mechanical instrument that measures, among other properties, the force imparted on a kernel during crushing) has been used in breeding programs to differentiate soft wheats from hard wheats. Nominally, these have a soft to hard SKCS hardness index (HI) range of 25–75 (dimensionless units). However, in recent years, breeders have developed extremely soft (‘Super Soft’) lines having SKCS HI < 0. Until now, these very low SKCS HIs have not been corroborated with traditional methodologies that characterize mechanical strength. Herein, we report on the relationships between SKCS HI and three compressive strength properties (maximum stress, Young's modulus, and work) in Super Soft wheat. With respective correlation coefficients of 0.76, 0.66, and 0.75, we have found that the relationships between SKCS HI and compressive strength agree with prior research involving ordinary soft and hard wheats.

Re-evolution of Durum Wheat by Introducing the Hardness and Glu-D1 Loci

Durum wheat is an important crop worldwide. In many areas, durum wheat appears to have competitive yield and biotic and abiotic advantages over bread wheat. What limits durum production? In one respect, the comparatively more limited processing and food functionality. Two traits directly relate to these limitations: kernel texture (hardness) and gluten strength. We have addressed both using ph1b-mediated translocations from bread wheat. For kernel texture, ca. 28 Mbp of chromosome 5DS replaced about 20 Mbp of 5BS. SKCS hardness was reduced from ca. 80 to 20 as the puroindolines were expressed and softened the endosperm. Break flour yields increased from 17% to >40%. Straight-grade flour had low starch damage (2%), and a mean particle size of 75 µm. Crosses with CIMMYT durum lines all produced soft kernel progeny and a high degree of genetic variance for milling and baking quality. Solvent Retention Capacities (SRC) and cookie diameters were similar to soft white hexaploid wheat, showing that soft durum can be considered a “tetraploid soft white spring wheat”. Regarding gluten strength, CIMMYT durums contributed a high genetic variance, with the “best” progeny exhibiting SDS sedimentation volume, SRC Lactic Acid and Mixograph characteristics that were similar to medium-gluten strength U.S. hard red winter. The best loaf volume among these progeny was 846 cm3 at ca. 12.8% flour protein. To further address the issue of gluten strength, Soft Svevo was crossed with durum lines possessing Dx2+Dy12 and Dx5+Dy10. Bread baking showed that Dx5+Dy10 was overly strong, whereas Dx2+Dy12 significantly improved bread loaf volume. The best progeny produced a loaf volume of 1010 cm3 at 12.1% protein. As a comparison, the long-term in-house regression for loaf volume-flour protein for hard red ‘bread’ wheats is 926 cm3 at 12.1% protein. Obviously, from these results, excellent bread making potential has been achieved.

Identification of loci and molecular markers associated with Super Soft kernel texture in wheat

The preferential application of wheat flour in various end-use products is primarily driven by kernel texture (softness/hardness). Herein, a population of 268 F6 recombinant inbred lines (RILs) was developed by crossing the wheat cultivar Alpowa (‘normal’ soft) (SKCS HI = 20.2) with a related ‘Super Soft’ line (BC2SS163) (HI = −1.2). A set of 19 polymorphic markers including 16 Kompetitive allele specific PCR (KASP) and three simple sequence repeat (SSR) markers were targeted to three genomic regions (4BS, 1BS and 5AL) and used to genotype the RILs and parents. Four QTLs were detected for kernel texture using composite interval mapping (CIM) including one major QTL on 4BS, and three minor QTLs [5AL (2) and 1BS (1)]. Eight significant markers were identified using single marker-trait association (SMA) analysis and explained 3.8–28.0% phenotypic variation (PV). Two markers from the combined analyses were selected with the highest PV (8.0% and 36.7%). These two marker loci were independent and additive. RILs possessing both favorable (soft) alleles had an average SKCS hardness of 4.9 vs. 15.7 for the alternate haplotype. We conclude that the Super Soft trait is polygenic and that we have identified one of two or more major loci conferring this phenotype.

Milling performance of waxy wheat and wild‐type wheat using two laboratory milling methods

AbstractBackground and objectivesFlour and starch from waxy wheat (Triticum aestivum L) have unique properties such as high water‐holding capacity, low pasting temperature, low syneresis, and high resistance to retrogradation. However, the milling performance of waxy wheat was not well documented. In this study, the milling quality of a waxy wheat (Mattern) was evaluated by comparing its flour yield, chemical composition, flow properties, and particle size distribution with that of two wild‐type hard red winter (HRW) wheats (Wesley and Everest) using two laboratory milling methods. The effects of moisture level and tempering time on milling behavior for the waxy wheat (Mattern) were examined and compared with that of wild‐type wheat.FindingsWaxy wheat (Mattern) seemed to require more moisture during tempering than wild‐type wheats to achieve a similar drop in SKCS hardness. For Mattern, the overall grain hardness drop was minimal when tempering to moisture contents below 17.5%. When the tempering moisture content increased from 13% to 17.5%, the flour yield increased, but decreased after 17.5% moisture content. Tempering Mattern to 16% and higher resulted in a higher bran yield compared with shorts yield, although the yield of the shorts from Mattern was significantly greater than that of the shorts from both wild‐type wheats. The flour yield of Mattern was 65.1%, which was significantly lower than that of both wild‐type wheats (73.1% for Wesley and 72.2% for Everest).ConclusionsAt the same moisture content (16%), the hardness of the waxy wheat (Mattern) kernel decreased at a slower rate than the wild‐type wheat during tempering for 48 hr. The flour yield of the waxy wheat (Mattern) was significantly lower than that of wild‐type wheat. Mattern flour was less free‐flowing and more adhesive than the wild‐type HRW flour, mainly due to its smaller particle size and higher fat content.Significance and noveltyHigher optimal tempering moisture was needed to mill the waxy wheat (Mattern), and the yield of waxy wheat flour was maximized when the kernels were tempered at 17.5% moisture for 24 hr.

Bread wheat milling behavior: effects of genetic and environmental factors, and modeling using grain mechanical resistance traits.

Genetic (Pinb-D1 alleles) and environment (through vitreousness) have important effects on bread wheat milling behavior. SKCS optimal values corresponding to soft vitreous or hard mealy grains were defined to obtain the highest total flour yield. Near-isogenic lines of bread wheat that differ in hardness, due to distinct puroindoline-b alleles (the wild type, Pinb-D1a, or the mutated forms, Pinb-D1b or Pinb-D1d), were grown in different environments and under two nitrogen fertilization levels, to study genetic and environmental effects on milling behavior. Milling tests used a prototype mill, equipped with two break steps, one sizing step, and two reduction steps, and this enabled 21 individual or aggregated milling fractions to be collected. Four current grain characters, thousand grain weight, test weight, grain diameter, and protein content, were measured, and three characters known to influence grain mechanical resistance, NIRS hardness, SKCS hardness index, and grain vitreousness (a character affecting the grain mechanical behavior but generally not studied). As expected, the wild type or mutated forms of Pinb-D1 alleles led to contrasted milling behavior: soft genotypes produced high quantities of break flour and low quantities of reduction flour, whereas reverse quantities were observed for hard genotypes. This different milling behavior had only a moderate influence on total flour production. NIRS hardness and vitreousness were, respectively, the most important and the second most important grain characters to explain milling behavior. However, contrary to NIRS hardness, vitreousness was only involved in endosperm reduction and not in the separation between the starchy endosperm and the outer layers. The highest flour yields were obtained for SKCS values comprised between 30 and 50, which corresponded either to soft vitreous or hard mealy grains. Prediction equations were defined and showed a good accuracy estimating break and reduction flours portions, but should be used more cautiously for total flour.

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 controls. All hard and intermediate hardness alleles had decreased break flour yield, but intermediate hardness allele PINA‐P35S had higher break flour yield than common hard allele Pinb‐D1b. Intermediate and hard alleles resulted in increased abundance of larger and reduced levels of smaller flour particles. None of the missense alleles differed from their controls for loaf volume. The seven selected Pin alleles imparted defined levels of grain hardness and milling properties not previously available that may prove useful in wheat improvement.

Alveograph and Mixolab parameters associated with Puroindoline‐D1 genes in Chinese winter wheats

Grain texture is one of the most important characteristics of bread wheat and has a significant influence on end-use qualities. Forty-three Chinese cultivars were tested under three environments and used to characterise kernel hardness, Puroindoline-D1 alleles and Alveograph and Mixolab parameters. The results indicated that SKCS hardness was positively correlated with Alveograph tenacity and P/L and Mixolab protein weakening (C2) and water absorption and negatively correlated with Mixolab starch gelatinisation (C3), amylasic activity (C4) and starch gelling (C5). Variance analysis showed that Puroindoline-D1 had a significant impact on SKCS hardness and most Alveograph and Mixolab parameters. Furthermore, among three Puroindoline-D1 genotypes, PINA-null/Pinb-D1a possessed the highest SKCS hardness, Alveograph tenacity and W and Mixolab stability and water absorption but the lowest Alveograph extensibility and G and Mixolab C3, C4 and C5. Pina-D1a/Pinb-D1a had the lowest SKCS hardness, Alveograph tenacity and W and Mixolab C2, water absorption and stability but the highest Alveograph extensibility and G and Mixolab C3, C4 and C5. Pina-D1a/Pinb-D1b possessed the lowest Mixolab C2 - C1, C3 - C2, C4 - C3 and C5 - C4. Pina-D1a/Pinb-D1a was softer and had lower tenacity and water absorption. PINA-null/Pinb-D1a was harder and had higher tenacity and water absorption. Pina-D1a/Pinb-D1b had lower difference values among Mixolab parameters.

Discovery, distribution and diversity of Puroindoline-D1 genes in bread wheat from five countries (Triticum aestivum L.)

BackgroundGrain texture is one of the most important characteristics in bread wheat (Triticum aestivum L.). Puroindoline-D1 genes play the main role in controlling grain texture and are intimately associated with the milling and processing qualities in bread wheat.ResultsA series of diagnostic molecular markers and dCAPS markers were used to characterize Pina-D1 and Pinb-D1 in 493 wheat cultivars from diverse geographic locations. A primer walking strategy was used to characterize PINA-null alleles at the DNA level. Results indicated that Chinese landraces encompassing 12 different Puroindoline-D1 allelic combinations showed the highest diversity, while CIMMYT wheat cultivars containing 3 different Puroindoline-D1 allelic combinations showed the lowest diversity amongst wheat cultivars from the five countries surveyed. Two novel Pina-D1 alleles, designated Pina-D1s with a 4,422-bp deletion and Pina-D1u with a 6,460-bp deletion in the Ha (Hardness) locus, were characterized at the DNA level by a primer walking strategy, and corresponding molecular markers Pina-N3 and Pina-N4 were developed for straightforward identification of the Pina-D1s and Pina-D1u alleles. Analysis of the association of Puroindoline-D1 alleles with grain texture indicated that wheat cultivars with Pina-null/Pinb-null allele, possessing an approximate 33-kb deletion in the Ha locus, have the highest SKCS hardness index amongst the different genotypes used in this study. Moreover, wheat cultivars with the PINA-null allele have significantly higher SKCS hardness index than those of Pinb-D1b and Pinb-D1p alleles.ConclusionsMolecular characterization of the Puroindoline-D1 allele was investigated in bread wheat cultivars from five geographic regions, resulting in the discovery of two new alleles - Pina-D1s and Pina-D1u. Molecular markers were developed for both alleles. Analysis of the association of the Puroindoline-D1 alleles with grain texture showed that cultivars with PINA-null allele possessed relatively high SKCS hardness index. This study can provide useful information for the improvement of wheat quality, as well as give a deeper understanding of the molecular and genetic processes controlling grain texture in bread wheat.

Molecular and cytogenetic characterization of a small alien-segment translocation line carrying the softness genes of Haynaldia villosa

The wheat-alien small segment translocation (SAST) lines carrying the beneficial genes from wild species are useful genetic stocks for wheat improvement. In this study, to introduce the grain hardness-related genes of Haynaldia villosa (L.) Schur. into common wheat (Triticum aesitivum L.), the mature female gametes of whole-arm wheat--H. villosa translocation line T5VS·5DL was irradiated by 60CO-γ ray to develop SAST lines involving 5VS. Among the BC2F2 population, six homozygous SAST lines with different fragment sizes of 5VS were identified by GISH, and the exact fragment sizes were further defined using four 5VS-specific markers and four Ha gene-based markers. The results showed that five lines (NAU5VS-1 to NAU5VS-5) carried the softness gene Dina/Dinb of H. villosa, and that NAU5VS-5 had the smallest alien translocation segment, identified to be a 5VS-6AS·6AL terminal translocation. The translocation chromosome 5VS-6AS·6AL was proved to be stably inherited to the successive generations. In the BC3F2 generation, the individuals having the homozygous 5VS-6AS·6AL translocation chromosomes all showed soft grain texture, with an approximately 50% reduction in the SKCS hardness index compared with that of their backcrossing parent. Both the 5VS-6AS·6AL translocation line and the molecular markers developed in this study will be valuable in wheat breeding for soft grain quality improvement.

Chromosomal loci associated with endosperm hardness in a malting barley cross

A breeding objective for the malting barley industry is to produce lines with softer, plumper grain containing moderate protein content (9-12%) as they are more likely to imbibe water readily and contain more starch per grain, which in turn produces higher levels of malt extract. In a malting barley mapping population, 'Arapiles' × 'Franklin', the most significant and robust quantitative trait locus (QTL) for endosperm hardness was observed on the short arm of chromosome 1H, across three environments over two growing seasons. This accounted for 22.6% (Horsham 2000), 26.8% (Esperance 2001), and 12.0% (Tarranyurk 2001) of the genetic variance and significantly increased endosperm hardness by 2.06-3.03 SKCS hardness units. Interestingly, Arapiles and Franklin do not vary in Ha locus alleles. Therefore, this region, near the centromere on chromosome 1H, may be of great importance when aiming to manipulate endosperm hardness and malting quality. Interestingly, this region, close to the centromere on chromosome 1H, in our study, aligns with the region of the genome that includes the HvCslF9 and the HvGlb1 genes. Potentially, one or both of these genes could be considered to be candidate genes that influence endosperm hardness in the barley grain. Additional QTLs for endosperm hardness were detected on chromosomes 2H, 3H, 6H and 7H, confirming that the hardness trait in barley is complex and multigenic, similar to many malting quality traits of interest.

Association of Puroindoline b-B2 variants with grain traits, yield components and flag leaf size in bread wheat ( Triticum aestivum L.) varieties of the Yellow and Huai Valleys of China

A total of 169 wheat ( Triticum aestivum L.) varieties (landraces and cultivars) were used to asses the relationship between Puroindoline D1 alleles and Puroindoline b-B2 variants and grain hardness, other grain traits, yield components, and flag leaf size. Results indicated that the average SKCS hardness of Pinb-B2v3 varieties was significantly greater than that of Pinb-B2v2 varieties within the soft Puroindoline D1 haplotype sub-group. Conversely, no statistically significant difference was obtained for SKCS hardness between varieties with the Pinb-B2v3 vs. Pinb-B2v2 alleles within the two hard Puroindoline D1 haplotypes ( Pinb-D1b and Pinb-D1p sub-groups). Therefore, the Puroindoline b-B2 gene may have a bigger impact on soft wheat varieties than hard. Across all varieties, thousand-kernel weight, grain weight per spike, grain diameter, grain number per spike, flag leaf width and area of Pinb-B2v3 varieties were significantly greater than those possessing Pinb-B2v2. These results indicated that the Pinb-B2v3 allele was associated with preferable grain yield traits compared to the Pinb-B2v2 allele in bread wheat. This study provides evocative information for better understanding the molecular and genetic basis of wheat grain yield.

Prevalence of puroindoline alleles in wheat varieties from eastern Asia including the discovery of a new SNP in puroindoline b

Kernel texture (grain hardness) in common wheat (Triticum aestivumL.) is of primary technological importance and is largely determined by puroindoline gene sequence and expression. We investigated the puroindoline haplotypes of 246 Asian common wheat varieties. All but three were conclusively characterized for puroindoline a and b haplotypes. Of the total, 174 possessed the softPina-D1a/Pinb-D1a‘wild-type’ gene sequences with SKCS hardness indexes (HI) ranging from 13.5 to 61.8. Among the remaining 72 varieties with HIs of 56.1–97.8, nearly half (30) werePina-D1a/Pinb-D1b, 4 werePina-D1a/Pinb-D1c, 19 werePina-D1a/Pinb-D1p, 10 werePina-D1b/Pinb-D1a(‘a-null’), 3 werePina-D1l/Pinb-D1a, 2 possessed a new C-to-T SNP mutation at position 382, which is tentatively designatedPinb-D1ab, 1 was a ‘double null’ with neither puroindoline a nor b expressed and no PCR-detectable gene sequence, and 3 had undetermined/ambiguous puroindoline a sequence but possessedPinb-D1a. The double null was the hardest of all varieties tested with an HI of 97.8. The frequency of soft and hard varieties and puroindoline hardness haplotype varied depending on the origin of the varieties. The lowest frequency of hard varieties occurred in Korea and south-western Japan. Tibet and Pakistan also had low frequencies of hard varieties. The highest frequency of hard varieties appeared in north-east China followed by north-west China and Nepal. Within Asia, thePinb-D1pallele appears in a region extending from north-eastern China through Inner Mongolia, north-western China, Xinjiang and Tibet, with the greatest frequency in north-western China. This allele was also present in Pakistan and Afghanistan, but not found in Japan, and may have been dispersed along the ‘Silk Road’. All threePina-D1lvarieties came from China. The newly discovered SNP originated in Afghanistan and the ‘double null’ in Xinjiang.

Relationship Between Single Wheat Kernel Particle‐Size Distribution and Perten SKCS 4100 Hardness Index

ABSTRACTThe Perten Single Kernel Characterization system is the current reference method for determination of single wheat kernel texture. However, the SKCS 4100 calibration method is based on bulk samples. The objective of this research was to develop a single‐kernel hardness reference based on single‐kernel particle‐size distributions (PSD). A total of 473 kernels, drawn from eight different classes, was studied. Material from single kernels that had been crushed on the SKCS 4100 system was collected, milled, then the PSD of each ground single kernel was measured. Wheat kernels from soft and hard classes with similar SKCS hardness indices (HI 40–60) typically had a PSD that was expected from their genetic class. That is, soft kernels tended to have more particles at &lt;21 μm than hard kernels after milling. As such, a combination of HI and PSD gives better discrimination between genetically hard and soft classes than either parameter measured independently. Additionally, the use of SKCS‐predicted PSD, combined with other low level SKCS parameters, appears to reduce classification errors into genetic hardness classes by ≈50% over what is currently accomplished with HI alone.

Small‐Scale Bread‐Quality‐Test Performance Heritability in Bread Wheat: Influence of High Molecular Weight Glutenin Subunits and the 1BL.1RS Translocation

Small‐scale bread‐quality assays (grain protein content, SDS‐sedimentation volume [SDSS], and single‐kernel characterization system [SKCS] grain hardness) represent important tools in bread wheat (Triticum aestivum L.) breeding. The influence of high‐molecular‐weight glutenin (HMWG) subunits and the 1BL.1RS translocation on small‐scale bread‐quality assays and their heritability was investigated for F3 and F4 lines of two wheat populations. Lines with HMWG subunits 5+10 at Glu‐D1 showed significantly greater SDSS volume and SKCS hardness than those with subunits 2+12 or 4+12. Lines with HMWG subunit 20 at Glu‐B1 had a significantly lower SDSS volume than those with HMWG subunits 7+8 or 7+9. F4 lines bearing the 1BL.1RS translocation had significantly greater protein content. The distribution of SDSS volumes suggested that most bore the undesirable HMWG subunits 2+12, 4+12 or 20, but could be selected against if the SDSS volume &lt;6.0 mL. For SDSS volume, lines with HMWG subunits 5+10 had greater heritability in upward screening, whereas those with HMWG subunits 2+12 or 4+12 had greater heritability in downward screening. The above screening criterion provides an excellent tool for bread quality‐based wheat breeding, irrespective of hard × hard or hard × soft wheat crosses.

Molecular characterization of allelic variations at Pina and Pinb loci in Shandong wheat landraces, historical and current cultivars

Grain hardness is very important in determining the milling and end-use quality of bread wheat. The objectives of this study were to develop gene specific primers for the allele Pina-D1b, evaluate the method for the identification of Pinb-D1p with restriction enzyme PflMI and characterize allelic variations at Pina and Pinb loci in Shandong wheat germplasm. Based on the nucleotide sequences of Ha locus reported previously (CR626934 and CR626926), 121 primer sets were developed to test the Pina-D1b allele. Sequence alignment showed that the promoter region of Pina-D1b allele was highly conserved in the region from −1134 to −23 bp relative to the transcription start codon ATG. Pinb-D1p was first reported in Chinese wheat landraces, with a base A deletion at position 213 in the coding region. Restriction analysis of Pinb-D1p indicated that the base A deletion resulted in the missing of the cleavage site with enzyme PflMI and the digestion with PflMI was validated as a reliable tool for the identification of Pinb-D1p allele. A total of 523 wheat accessions from Shandong province including 431 landraces, 63 historical and 29 current cultivars were chosen for the test of SKCS hardness and identification of puroindoline alleles using DNA markers developed in this study and those reported previously. Frequencies of soft, mixed and hard genotypes were 3.9%, 20.4% and 75.6% in Shandong landraces; 68.3%, 19.0% and 12.7% in historical cultivars; and 27.6%, 58.6% and 13.8% in current cultivars, respectively. Frequencies of Pina-D1b, Pinb-D1b and Pinb-D1p were 38.0%, 0.9% and 59.6% in hard landraces; and 37.5%, 37.5% and 25% in hard historical cultivars, respectively, whereas the Pinb-D1b was the only genotype in hard current cultivars. A novel Pinb allele with double mutations at the positions 96 (C to A) and 213 (deletion of A) was found in three landraces and designated as Pinb-D1aa.

Prevalence of a novel puroindoline b allele in Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King)

Grain hardness is a major factor influencing the classification and end-use quality of bread wheat. In this study, 40 Yunnan endemic wheats, 21 historical cultivars and 66 current cultivars and advanced lines were investigated for kernel hardness and puroindoline alleles using molecular and biochemical markers. The frequencies of soft, mixed and hard genotypes were 10.0%, 5.0% and 85.0%, respectively, in Yunnan endemic wheats, whereas the corresponding frequencies were 47.6%, 23.8% and 28.6% in historical cultivars, and 36.3%, 6.1% and 57.6% in current cultivars and advanced lines. Four known puroindoline alleles, Pina-D1b, Pinb-D1b, Pinb-D1d and Pinb-D1e, were found in the hard wheat cultivars. Compared with endemic wheats and historical cultivars, current cultivars from Yunnan province have relatively high frequencies of Pina-D1b and Pinb-D1b alleles at 43.5% and 16.1%, respectively. All 32 hard Yunnan endemic wheats (Triticum aestivum ssp. yunnanense King) contained a new puroindoline b allele, designated Pinb-D1u, that was characterized as a single nucleotide (G) deletion at position 127 in the coding sequence of the Pinb gene, leading to a shift of the open reading frame (ORF) from position 14 in the deduced amino acid sequence and a stop codon corresponding to position Leu-18. The average SKCS hardness of genotypes with Pina-D1b (68.2) is significantly higher than those of Pinb-D1b (60.3) and Pinb-D1u (60.5). The study of puroindoline alleles in Yunnan germplasm could provide useful information for improving processing quality and further understanding the molecular basis of kernel hardness in bread wheat.

Puroindoline grain hardness alleles in CIMMYT bread wheat germplasm

Grain hardness is an important quality parameter of bread wheat ( Triticum aestivum L.) with importance for wheat classification and end use properties, and is controlled by the genes puroindoline a ( Pina) and puroindoline b ( Pinb). The presence of known hardness alleles was studied in a representative sample of 373 bread wheat lines from the breeding program at CIMMYT. The PINA-null mutation ( Pina- D1b) was the most frequent hardness allele and present in 283 of the 328 lines with hard endosperm. All other hard wheat had the glycine to serine mutation in PINB ( Pinb- D1b). A study of historically important CIMMYT bread wheat lines showed that Pina- D1b has been the dominating hardness allele since the inception of the wheat breeding program in Mexico. New puroindoline alleles have recently been introduced through the extensive use of synthetic hexaploid wheat, and the textural effects of various Aegilops tauschii-derived Pina and Pinb alleles were studied in 92 breeding lines derived from various crosses with synthetic wheat. Progeny lines with Pina- D1j/ Pinb- D1i were on average 10 SKCS hardness units softer than those carrying the allelic combination Pina- D1c/ Pinb- D1h. Further investigation is needed to validate the potential of such minor allelic differences for the improvement of soft wheat quality.

Kernel texture differences among US soft wheat cultivars

AbstractKernel texture is a key factor in the quality and utilization of soft wheat (Triticum aestivum L), yet the variation in kernel texture among US soft wheat cultivars is largely unknown. This study evaluated the following hypothesis: soft wheat cultivars differ in kernel texture due to minor genetic factor(s). Once identified, selected contrasting cultivars could serve as candidates for crop improvement and future genetic studies. To test the hypothesis, kernel texture (SKCS, Single Kernel Characterization System), NIR (near‐infrared reflectance) and Quadrumat break flour yield were evaluated for 30 cultivars drawn from the four major US soft wheat regions and sub‐classes (eastern and western soft white winter, soft red winter and Club). Cultivars were grown in replicated trials over 6 site‐years in Washington state. The results clearly indicated that relatively large, consistent genetic differences in kernel texture exist among US soft wheat cultivars. SKCS and NIR were fairly well correlated (r = 0.85) and tended to rank cultivars in the same order. However, individual cultivars deviated from this linear relationship and occasionally rankings changed substantially. Trends were observed among the geographical regions and sub‐classes, eg the first 13 hardest‐ranked positions (SKCS) were held by western cultivars (13 of the 16 total western cultivars). Quadrumat break flour yield provided an independent assessment of kernel texture and was not correlated with SKCS or NIR hardness. Four distinct cultivar groupings were made based on analysis of variance and two‐dimensional graphical assessment. Each group represented contrasting levels of kernel texture (SKCS or NIR) and break flour yield. Identification of the specific underlying gene(s) conferring kernel texture variation among US soft wheats awaits the next phase of research. Copyright © 2005 Society of Chemical Industry