Mapping QTLs for grain hardness and puroindoline content in wheat ( Triticum aestivum L.)

Genes for puroindoline-a (Pin-a), puroindoline-b (Pin-b) and grain-softness proteins (GSP) have been shown to be linked to the dominant Ha locus responsible for the soft texture of the grain. Though linkage has been demonstrated of the puroindoline genes to the Ha locus, there is no clear evidence that puroindoline content is the product of the gene Ha. A segregating population of 115 recombinant inbred lines (RILs) originating from a cross between the hexaploid Synthetic wheat ( Triticum durum x Aegilops tauschii, W 7984) and the cultivar 'Opata' (M 85) was studied in two different experimental years to detect Quantitative Trait Loci (QTLs) for three traits: grain hardness (Hard), puroindoline-a (Pin-a) and puroindoline-b (Pin-b) contents. The detection of QTLs was performed using marker linear regression. Negative correlation coefficients (-0.86 and -0.80) were identified between grain hardness and puroindoline content (a and b, respectively) on data obtained in 1996. Results obtained in 1999 confirmed the negative correlation between Hard and Pin-a (-0.73); however a positive correlation coefficient was found with Pin-b content (0.41). Total phenotypic variation explained by each QTL was calculated (R2). For each of the Hard, Pin-a and Pin-b traits one major QTL was detected on the short arm of chromosome 5D, located close to the mta9 allele (puroindoline-a). For the first year (1996) the QTL in this region explained around 63% of the phenotypic variability in grain hardness, 77% in Pin-a and 45% in Pin-b contents. These values were confirmed in trials carried out in 1999 with a R2 value of 0.71, 0.72 and 0.25 for Hard, Pin-a and Pin-b, respectively. In 1996 and 1999 a second major QTL was detected for grain hardness on the long arm of the same chromosome. Present results indicate that it cannot be definitely concluded that puroindoline content represents a linear explanation for variations in grain hardness.     

Starch-bound 2S proteins and kernel texture in einkorn, <Emphasis Type="Italic">Triticum</Emphasis> <Emphasis Type="Italic">monococcum</Emphasis> ssp <Emphasis Type="Italic">monococcum</Emphasis>

The starch granule proteins from 113 einkorn wheat (Triticum monococcum ssp monococcum) accessions were analyzed by acidic, polyacrylamide gel electrophoresis (A-PAGE), and two-dimensional A-PAGE x SDS-PAGE. All accessions were confirmed to contain equal amounts of two polypeptide chains corresponding to puroindoline B (Pin-B), as well as a prominent component plus a faint band corresponding to puroindoline A (Pin-A). When compared with soft-textured common wheat, “monococcum” accessions showed an increase of 3.2- and 2.7-fold in Pin-A and Pin-B levels on the starch granules, respectively. In addition, all accessions contained a novel component of the 2S super-family of seed proteins named Einkorn Trypsin Inhibitor (ETI), which was found to be encoded as a pre-protein 148 residues long. Wild-type ETI encoded by allele Eti-A ^m 1a and “valine-type” ETI encoded by allele Eti-A ^m 1b, which occurred in 107 and six einkorn accessions, respectively, were found to accumulate on starch granules as a mature protein of 121 amino acids with a hydrophobic central domain. The einkorn accessions exhibited an average SKCS index as low as −2.05 ± 11.4, which is typical of extra-soft kernels. The total surface area of starch granules in “monococcum” wheat, as determined by visual assessments in counting chambers, was estimated at 764 mm²/mg of starch, and was about 1.5 times higher than that for common wheat. The results are discussed in relation to the identification of factors that cause the extra-soft texture of einkorn kernels.     

Molecular and biochemical characterization of puroindoline a and b alleles in Chinese landraces and historical cultivars

Kernel hardness that is conditioned by puroindoline genes has a profound effect on milling, baking and end-use quality of bread wheat. In this study, 219 landraces and 166 historical cultivars from China and 12 introduced wheats were investigated for their kernel hardness and puroindoline alleles, using molecular and biochemical markers. The results indicated that frequencies of soft, mixed and hard genotypes were 42.7, 24.3, and 33.0%, respectively, in Chinese landraces and 45.2, 13.9, and 40.9% in historical cultivars. The frequencies of PINA null, Pinb-D1b and Pinb-D1p genotypes were 43.8, 12.3, and 39.7%, respectively, in hard wheat of landraces, while 48.5, 36.8, and 14.7%, respectively, in historical hard wheats. A new Pinb-D1 allele, designated Pinb-D1t, was identified in two landraces, Guangtouxianmai and Hongmai from the Guizhou province, with the characterization of a glycine to arginine substitution at position 47 in the coding region of Pinb gene. Surprisingly, a new Pina-D1 allele, designated Pina-D1m, was detected in the landrace Hongheshang, from the Jiangsu province, with the characterization of a proline to serine substitution at position 35 in the coding region of Pina gene; it was the first novel mutation found in bread wheat, resulting in a hard endosperm with PINA expression. Among the PINA null genotypes, an allele designed as Pina-D1l, was detected in five landraces with a cytosine deletion at position 265 in Pina locus; while another novel Pina-D1 allele, designed as Pina-D1n, was identified in six landraces, with the characterization of an amino acid change from tryptophan-43 to a ‘stop’ codon in the coding region of Pina gene. The study of puroindoline polymorphism in Chinese wheat germplasm could provide useful information for the further understanding of the molecular basis of kernel hardness in bread wheat.     

Puroindoline A-gene expression is involved in association of puroindolines to starch

Puroindolines largely influence cereal grain hardness. In order to understand how they exert this influence, we carried out a molecular analysis of the pina and pinb genes of many Italian wheat cultivars. On the basis of their pin genotypes they could be divided into three groups: Pina-D1a/Pinb-D1a; Pina-D1a/Pinb-D1b; and Pina-D1b/Pinb-D1a. Five cultivars from each group were chosen to be studied to examine the quantity of puroindolines associated with starch (friabilin) and the amount not associated with starch. In addition, the level of pina expression was measured using RT-PCR. Soft cultivars (Pina-D1a/Pinb-D1a) exhibited the highest level of expression of pina; among the hard cultivars, those with the Pina-D1a/Pinb-D1b genotype showed a lower level of expression, while those with the Pina-D1b/Pinb-D1a genotype did not express pina. Total puroindoline and friabilin content was then measured by flow cytometry. Soft Pina-D1a/Pinb-D1a cultivars displayed high puroindoline content that was primarily starch associated. Hard Pina-D1b/Pinb-D1a cultivars had very low puroindoline content with no puroindoline bound to starch. Hard Pina-D1a/Pinb-D1b cultivars were highly heterogeneous with respect to both the content of puroindolines and the level of association with starch. The accurate quantification of puroindolines in starch-bound and not starch-bound forms in association with molecular analysis, indicates that pina expression and presence controls the abundance of total puroindoline and its association with starch.Communicated by H.F. Linskens     

Mutations in wheat starch synthase II genes and PCR-based selection of a SGP-1 null line

Wheat (Triticum aestivum L.) starch synthase II, which is also known as starch granule protein 1 (SGP-1), plays a major role in endosperm starch synthesis. The three SGP-1 proteins, SGP-A1, B1 and D1, are produced by three homoeologous SSII genes, wSSII-A, B, and D. Lines carrying null alleles for each SGP-1 protein have previously been identified. In this report, the mutations occurring in each wSSII gene were characterized, and PCR-based DNA markers capable of detecting the mutations were developed. In the null wSSII-A allele, a 289 bp deletion accompanied by 8 bp of filler DNA was present near the initiation codon. A 175 bp insertion occurred in exon 8 of the null wSSII-B allele. The insertion represented a recently discovered miniature inverted-repeat transposable element (MITE) named Hikkoshi that was first found in a wheat waxy gene. A 63 bp deletion was found at the region surrounding the junction of the fifth exon and intron of the null wSSII-D allele. Based on this information, we designed primer sets to enable us to conduct allele-specific amplifications for each locus. The applicability of these primer sets for breeding programs was demonstrated by reconstructing a line lacking all three SGP-1 proteins using marker-assisted selection. These markers will also be useful in breeding programs aimed at obtaining partial mutants missing one or two SGP-1 proteins.     

Puroindoline-b mutations control the lipid binding interactions in mixed puroindoline-a:puroindoline-b systems

The interactions have been investigated of puroindoline-a (Pin-a) and mixed protein systems of Pin-a and wild-type puroindoline-b (Pin-b+) or puroindoline-b mutants (G46S mutation (Pin-bH) or W44R mutation (Pin-bS)) with condensed phase monolayers of an anionic phospholipid (L-alpha-dipalmitoylphosphatidyl-dl-glycerol (DPPG)) at the air/water interface. The interactions of the mixed systems were studied at three different concentration ratios of Pin-a:Pin-b, namely 3:1, 1:1 and 1:3 in order to establish any synergism in relation to lipid binding properties. Surface pressure measurements revealed that Pin-a interaction with DPPG monolayers led to an equilibrium surface pressure increase of 8.7 +/- 0.6 mN m-1. This was less than was measured for Pin-a:Pin-b+ (9.6 to 13.4 mN m-1), but was significantly more than was measured for Pin-a:Pin-bH (4.0 to 6.2 mN m-1) or Pin-a:Pin-bS (3.8 to 6.3 mN m-1) over the complete range of concentration ratio. Consequently, surface pressure increases were shown to correlate to endosperm hardness phenotype, with puroindolines present in hard-textured wheat varieties yielding lower equilibrium surface pressure changes. Integrated amide I peak areas from corresponding external reflectance Fourier-transform infrared (ER-FTIR) spectra, used to indicate levels of protein adsorption to the lipid monolayers, showed that differences in adsorbed amount were less significant. The data therefore suggest that Pin-b mutants having single residue substitutions within their tryptophan-rich loop that are expressed in some hard-textured wheat varieties influence the degree of penetration of Pin-a and Pin-b into anionic phospholipid films. These findings highlight the key role of the tryptophan-rich loop in puroindoline-lipid interactions.     

Kernel texture and hordoindoline patterns in barley (Hordeum vulgare)

Hordoindolines, the tryptophan-rich polypeptides affecting grain hardness in barley, appeared as three pairs of polypeptides in the acidic polyacrylamide gel electrophoresis (A-PAGE) and two-dimensional A-PAGE?×?SDS-PAGE patterns of starch-granule proteins from 18 barley cultivars. On capillary RP-HPLC/nESI-MS/MS spectrometry, one pair of polypeptides was found to correspond to hordoindoline A (HINA), one to hordoindoline B1 (HINB1) and one to hordoindoline B2 (HINB2), the two polypeptides of each pair deriving from post-translational cleavage of a native hordoindoline at different positions at the N-terminus and/or C-terminus. Amongst the barley cultivars analyzed, cvs Hart and Sundance, which were claimed to be unique in lacking the Hina gene coding for HINA, revealed similar Hina coding sequences and accumulated hordoindoline HINA on their starch granules. The amount of total hordoindolines (HINA?+?HINB1?+?HINB2) on the starch granules, as quantified by densitometric scanning of A-PAGE gels, was comparable with that of puroindolines (PINA?+?PINB) in soft-textured wheat. By contrast, the amount of B-type hordoindolines (HINB1 and HINB2 combined) was 50?% lower than that of PINB, suggesting that the absence of barley cultivars with soft kernels is likely due to the reduced amount of B-type hordoindolines accumulated on the starch granules. Approximately 22 and 27?% of the phenotypic variation for kernel hardness in 56 barley cultivars analyzed by the Single Kernel Characterization System (SKCS) were explained by differences in kernel weight and B-type hordoindoline level, respectively. By contrast, the outer husk of barley grain showed no effect on the SKCS index.     

Molecular Characterization of Puroindolines and their Encoding Genes in Aegilops Ventricosa

Puroindolines, the tryptophan-rich proteins controlling grain hardness in wheat, appeared as two pairs of 13 kDa polypeptides in the Acid-PAGE (A-PAGE) and two-dimensional A-PAGE×SDS-PAGE patterns of starch-granule proteins from wild allotetraploid wheat Aegilops ventricosa Tausch. (2n = 4x = 28, genomes D^vD^vN^vN^v). Puroindoline pair a1 + a2 reacted strongly with an antiserum specific for puroindoline-a from common wheat (Triticum aestivum L.), whereas puroindoline pair b1 + b2 exhibited A-PAGE relative mobilities similar to that of puroindoline-b in Aegilops tauschii (Coss.), the D-genome donor to both common wheat and Ae. ventricosa. Puroindolines a2 and b1 were found to be encoded by alleles Pina-D1a and Pinb-D1h on chromosome 5D^v, respectively, whereas puroindolines a1 and b2 were assumed to be under the genetic control of chromosome 5N^v. Puroindoline a1 encoded by the novel Pina-N1a allele exhibited a high level of amino acid variation with respect to puroindoline-a. On the other hand, the tryptophan-rich region of puroindoline b2 encoded by allele Pinb-N1a showed a sequence change from lysine-42 to arginine, with no effect on the amount of protein b2 accumulated on the starch granules. A partial duplication of the pin-B gene (Pinb-relic) was identified about 1100 bp downstream from Pinb-D1 on chromosome 5D^v. The present findings are the first evidence of a tetraploid wheat species in which four puroindoline genes are expressed. The potential of Ae. ventricosa as a source of genes that may be used to modulate endosperm texture and other valuable traits in cultivated wheat species is discussed.     

A novel codominant marker for selection of the null Wx-B1 allele in wheat breeding programs

Waxy protein (granule-bound starch synthase I) is a key enzyme in the synthesis of amylose in endosperm tissue. The amylose content of wheat flour plays a significant role in determining Japanese udon noodle quality. Most wheat cultivars suitable for producing udon noodles have a low amylose level due to a lack of Wx-B1 protein conditioned by null Wx-B1 alleles. It was previously determined that the entire coding region of the wheat Wx-B1 gene is deleted in the most common null allele. However, the extent and breakpoints of the deletion have not been established. In this study, the position of the 3′ deletion breakpoint was refined by mapping with PCR-based markers. Using information from this analysis, a chromosome walk was initiated and the DNA sequence flanking the deletion breakpoints was obtained. The deletion included a 3,872 bp region downstream from the termination codon of Wx-B1 gene. Based on similarity with T. monococcum sequences, it was estimated that approximately 60 kb upstream of the Wx-B1 gene was also deleted. Using this sequence information, a codominant marker for the identification of the Wx-B1 null allele was developed. This marker can unambiguously identify heterozygous plants, which will accelerate the selection of partial waxy mutants carrying the Wx-B1 null allele.     

Characterization of puroindolines in the control of endosperm texture in common wheat lines with substitutions of homeologous group-5 chromosomes

The genetic control of grain hardness and its association with the specific friabilin content on starch granules of common wheat cultivars and lines with intervarietal substitutions of homeologous group-5 chromosomes were studied. A significant correlation was revealed between the technological parameters of grain hardness (mean size of flour particles) and the specific content of puroindolines on the starch surface estimated in terms of starch doses. The results obtained allowed the method of starch doses to be used to identify soft and hard wheat cultivars and lines based on an analysis of a single grain. The biochemical analysis confirmed the previously obtained estimates of flour-grinding properties of wheat cultivars and substitution lines and allowed specific genotypes to be characterized according to the composition of puroindolines. The influence of chromosomes 5D and 5A of donor wheat cultivars on the activity of the Ha loci of recipient cultivars was revealed and found to be associated with the composition of PIN products and with the expression of the Pina-D1 and Pinb-D1 genes.     

Isolation of polymorphic microsatellite markers for Begonia sutherlandii Hook. f.

Seven polymorphic microsatellite loci have been characterized for investigating population structure in the patchily distributed herb Begonia sutherlandii. Two loci (BSU3 and BSU4) exhibited population specific null alleles; primer redesign and allele sequencing for one of these loci showed two transition mutations in the original primer site. Two loci exhibited imperfect repeat polymorphisms due to single base pair indels in the flanking region (locus BSU6) and in the microsatellite region itself (BSU7). Transversion mutations were also found in the microsatellite region of locus BSU7. The remaining three loci amplified in all individuals tested and appeared to conform to a simple stepwise mutation pattern.     

Variability and genetics of spacer DNA sequences between the ribosomal-RNA genes of hexaploid wheat (Triticum aestivum)

Summary Using restriction enzyme digests of genomic DNA extracted from the leaves of 25 hexaploid wheat (Triticum aestivum L. em. Thell.) cultivars and their hybrids, restriction fragment length polymorphisms of the spacer DNA which separates the ribosomal-RNA genes have been examined. (From one to three thousand of these genes are borne on chromosomes 1B and 6B of hexaploid wheat). The data show that there are three distinct alleles of the 1B locus, designated Nor-B1a, Nor-B1b, and Nor-B1c, and at least five allelic variants of the 6B locus, designated Nor-B2a, Nor-B2b, Nor-B2c, Nor-B2d, and Nor-B2e. A further, previously reported allele on 6B has been named Nor-B2f. Chromosome 5D has only one allelic variant, Nor-D3. Whereas the major spacer variants of the 1B alleles apparently differ by the loss or gain of one or two of the 133 bp sub-repeat units within the spacer DNA, the 6B allelic variants show major differences in their compositions and lengths. This may be related to the greater number of rDNA repeat units at this locus. The practical implications of these differences and their application to wheat breeding are discussed.     

Allelic variations in <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci of historical and modern Iranian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Proline and glutamine-rich wheat seed endosperm proteins are collectively referred to as prolamins. They are comprised of HMW-GSs, LMW-GSs and gliadins. HMW-GSs are major determinants of gluten elasticity and LMW-GSs considerably affect dough extensibility and maximum dough resistance. The inheritance of glutenin subunits follows Mendelian genetics with multiple alleles in each locus. Identification of the banding patterns of glutenin subunits could be used as an estimate for screening high quality wheat germplasm. Here, by means of a two-step 1D-SDS-PAGE procedure, we identified the allelic variations in high and low-molecular-weight glutenin subunits in 65 hexaploid wheat (Triticum aestivum L.) cultivars representing a historical trend in the cultivars introduced or released in Iran from the years 1940 to 1990. Distinct alleles 17 and 19 were detected for Glu-1 and Glu-3 loci, respectively. The allelic frequencies at the Glu-1 loci demonstrated unimodal distributions. At Glu-A1, Glu-B1 and Glu-D1, we found that the most frequent alleles were the null, 7 + 8, 2 + 12 alleles, respectively, in Iranian wheat cultivars. In contrast, Glu-3 loci showed bimodal or trimodal distributions. At Glu-A3, themost frequent alleles were c and e. At Glu-B3 the most frequent alleles were a, b and c. At Glu-D3 locus, the alleles b and a, were the most and the second most frequent alleles in Iranian wheat cultivars. This led to a significantly higher Nei coefficient of genetic variations in Glu-3 loci (0.756) as compared to Glu-1 loci (0.547). At Glu-3 loci, we observed relatively high quality alleles in Glu-A3 and Glu-D3 loci and low quality alleles at Glu-B3 locus.     

Eleven new microsatellites for hop (Humulus lupulus L.)

We present a new set of 11 polymorphic microsatellite primer sequences for use with Humulus lupulus. Microsatellite‐enriched libraries for GA_n and GT_n types of repeats were produced. Sequencing of 72 clones revealed 42 unique inserts containing microsatellites, out of which 19 primer pairs were designed and microsatellite amplification was tested on 39 wild hops and cultivars. Eleven primer pairs showed single locus amplification with 2–13 alleles, average 7.2, of which 17 unique alleles were discovered. One primer pair amplified too strong stutter bands, one locus was monomorphic and multilocus amplification was obtained with the remaining six primer pairs.     

Copy number variations of CBF genes at the Fr‐A2 locus are essential components of winter hardiness in wheat

Winter hardiness is important for the adaptation of wheat to the harsh winter conditions in temperate regions and is thus also an important breeding goal. Here, we employed a panel of 407 European winter wheat cultivars to dissect the genetic architecture of winter hardiness. We show that copy number variation (CNV) of CBF (C‐repeat Binding Factor) genes at the Fr‐A2 locus is the essential component for winter survival, with CBF‐A14 CNV being the most likely causal polymorphism, accounting for 24.3% of the genotypic variance. Genome‐wide association mapping identified several markers in the Fr‐A2 chromosomal region, which even after accounting for the effects of CBF‐A14 copy number explained approximately 15% of the genotypic variance. This suggests that additional, as yet undiscovered, polymorphisms are present at the Fr‐A2 locus. Furthermore, CNV of Vrn‐A1 explained an additional 3.0% of the genotypic variance. The allele frequencies of all loci associated with winter hardiness were found to show geographic patterns consistent with their role in adaptation. Collectively, our results from the candidate gene analysis, association mapping and genome‐wide prediction show that winter hardiness in wheat is a quantitative trait, but with a major contribution of the Fr‐A2 locus.     

Identification of genetic loci affecting amylose content and agronomic traits on chromosome 4A of wheat

 Chromosome 4A of wheat carries the Wx-B1 gene encoding the granule-bound starch synthase involved in amylose synthesis in the endosperm. To determine the pleiotropic effects of this locus and effects of independent QTLs on agronomic traits, genetical analysis of chromosome 4A was conducted using 98 single-chromosome recombinant substitution lines derived from a cross of Chinese Spring and Chinese Spring (Kanto107 4A) with a low amylose content due to the null Wx-B1b allele. For amylose content, most of the genetic variation was explained by the allelic difference at the Wx-B1 locus. An additional QTL of minor effect was mapped in the 6.2-cM Xbcd1738/Xcdo1387 interval on the short arm, where the allele from Kanto107 led to an increase in amylose content. Field trials over two seasons revealed a pleiotropic effect of Wx-B1, or else the effect of a closely linked QTL, on ear emergence time. A QTL linked to Wx-B1 was detected for plant height. For plant yield and its components, there was no evidence for significant main effects associated with Wx-B1 or adjacent regions. One plant-yield QTL was identified by RFLP markers on the short arm and this was identical to QTLs controlling spikelet number/ear and grain weight/ear. At these QTLs for agronomic traits, alleles from Kanto107 contributed to an earlier emergence time, a height reduction and an yield increase. Received: 10 August 1998 / Accepted: 3 November 1998     

Molecular differentiation of null alleles at <Emphasis Type="Italic">ZCCT</Emphasis>-<Emphasis Type="Italic">1</Emphasis> genes on the A,B, and D genomes of hexaploid wheat

A dominant allele of the vernalization gene Vrn-2 is the wild type conferring winter growth habit, whereas a recessive vrn-2 allele confers spring growth habit. The recessive vrn-2 allele is mutated due to the deletion of the complete gene (a null form) or alternation of a key amino acid in the VRN-2 protein (a nonfunctional form) in diploid wheat or tetraploid wheat. VRN-2 is also denoted ZCCT due to the presence of a zinc finger and a CCT domain in its protein. There are two paralogous ZCCT genes at the VRN-2 locus in diploid Triticum monococcum and three paralogous ZCCT genes on each of the A and B genomes in tetraploid wheat, but little is known about the allelic variation in VRN-2 in hexaploid wheat. In the study reported here, we performed a one-shot PCR to simultaneously amplify the promoter regions of the three ZCCT-1 genes from hexaploid wheat, including the 302-bp fragment from ZCCT-A1, the 294-bp fragment from ZCCT-B1, and the 320-bp fragment from ZCCT-D1. Each amplicon could be differentiated by electrophoresis in an acrylamide/bisacrylamide gel. This PCR marker for different lengths of the three ZCCT-1 genes was used to search for null alleles in hexaploid wheat. A null allele was found in each of ZCCT-A1, ZCCT-B1, and ZCCT-D1 among 74 cultivars and genetic stocks of U.S. hexaploid wheat. Among 54 Chinese wheat cultivars, breeding lines, and landraces, we identified three accessions carrying a single null allele at ZCCT-A1, three accessions carrying a null allele at ZCCT-B1, and one accession carrying a double null allele at both ZCCT-A1 and ZCCT-D1. The potential application of these natural ZCCT-1 mutant materials in wheat breeding programs and studies on the genetics of wheat is discussed.     

The determinants of grain texture in cereals

Kernel hardness is an important agronomic trait that influences end-product properties. In wheat cultivars, this trait is determined by thePuroindoline a (Pina) andPuroindoline b (Pinb) genes, located in theHardness locus (Ha) on chromosome 5DS of the D genome. Wild type alleles code puroindoline a (PINA) and puroindoline b (PINB) proteins, which form a 15-kDa friabilin present on the surface of water-washed starch granules. Both the proteins are accumulated in the starch endosperm cells and aleurone of the mature kernels.Puroindoline-like genes coding puroindoline-like proteins in the starch endosperm occur in some of the genomes of Triticeae and Aveneae cereals. Orthologs are present in barley, rye and oats. However, some genomes of these diploid and polyploid cereals, like that ofTriticum turgidum var.durum (AABB) lack thepuroindoline genes, having a very hard kernel texture. The two wild type alleles in opposition (dominant loci) control the soft pheno-type. Mutation either inPina orPinb or in both leads to a medium-hard or hard kernel texture. The most frequent types ofPin mutations are point mutations within the coding sequence resulting in the substitution of a single amino acid or a null allele. The latter is the result of a frame shift determined by base deletion or insertion or a one-point mutation to the stop codon. The lipid-binding properties of the puroindolines affect not only the dough quality but also the plants’ resistance to pathogens. Genetic modification of cereals withPuroindoline genes and/or their promoters enable more detailed functional analyses and the production of plants with the desired characteristics.     

The inheritance of a urease-null trait in soybeans

Summary Four soybean seed urease nulls (lacking both the activity and antigen of the embryo-specific urease) were intermated and the F₁ and F₂ seed examined for urease activity. Both generations were without urease activity, and the nulls were therefore considered noncomplementing. In crosses of each null line to cultivars homozygous for the allelic, codominantly inherited urease slow or fast isozyme, the F₁ seed expressed the embryo-specific urease isozyme of the urease-expressing parent. A 3 1 segregation for presence and absence of urease was observed in progeny from F₁ and heterozygous F₂ plants. The F₂ and F₃ from fastXnull combinations revealed that urease-positive seed were all phenotypically urease fast, while the same seed from slowXnull combinations showed a segregation of one seed containing a fast urease, either exclusively or in a heterozygous state with the slow isozyme, for every 69 phenotypic slows. Data pooled from F₂ plants which segregate for both the presence (Sun) and absence (Sun) of urease and for the fast (Eu1-b) or slow (Eu1-a) urease allele indicate that the null lesion (Sun) is linked to Eu1 by approximately one map unit. The evidence is consistent with two models: (1) sun is an allele at the embryo-specific urease isozyme locus (Eu1) and that a high degree of exchange (and/or conversion) within the locus results in a 1% recombination frequency between the null trait and urease allozyme; (2) sun is at a distinct locus which is separated by one map unit from the embryo-specific urease isozyme locus (Eu1) upon which it acts in the cis position. Polyadenylated embryo RNA from one of the null lines, PI 229324, exhibited no urease template activity in vitro. Thus, the lack of urease antigen is due to lack of accumulation of translatable urease mRNA. The availability of soybeans lacking seed urease should be extremely useful to breeders as a trait for linkage studies and to geneticists as a transformation marker.Portions of this work were funded by the Illinois and Missouri Agricultural Experiment Stations, the SOHIO-University of Illinois Center of Excellence in Crop Molecular Genetics and Genetic Engineering and by grants PCM-8219652 from the National Science Foundation and USDA/SEA-CRCR-1-1374 from the USDA Competitive Grants Office     

Analysis of diversity of russian and Ukrainian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars for high-molecular-weight glutenin subunits

The allelic diversity of high-moleculat-weght glutenin subunits (HMWGS) in Russian and Ukrainian bread wheat cultivars was analyzed. The diversity of spring wheat cultivars for alleles of the Glu-1 loci is characterized by medium values of the polymorphism polymorphism information content (PIC), and in winter wheats it varies from high at the Glu-A1 locus to low at the Glu-D1 locus. The spring and winter cultivars differ significantly in the frequencies of alleles of the glutenin loci. The combination of the Glu-A1b, Glu-B1c, and Glu-D1a alleles prevails among the spring cultivars, and the combination of the Glu-A1a, Glu-B1c, and Glu-D1d alleles prevails among the winter cultivars. The distribution of the Glu-1 alleles significantly depends on the moisture and heat supply in the region of origin of the cultivars. Drought resistance is associated with the Glu-D1a allele in the spring wheat and with the Glu-B1b allele in the winter wheat. The sources of the Glu-1 alleles were identified in the spring and wheat cultivars. The analysis of independence of the distribution of the spring and winter cultivars by the market classes and by the alleles of the HMWGS loci showed a highly significant association of the alleles of three Glu-1 loci with the market classes in foreign cultivars and independence or a weak association in the Russian and Ukrainian cultivars. This seems to be due to the absence of a statistically substantiated system of classification of the domestic cultivars on the basis of their quality.