Waxy protein deficiency and chromosomal location of coding genes in common wheat

Deficiency of the wheat waxy (Wx) proteins (Wx-A1, Wx-B1 and Wx-D1) was studied in 1,960 cultivars derived from several countries. Gel electrophoretic analyses revealed that the null allele for the Wx-A1 protein occurred frequently in Korean, Japanese and Turkish wheats but was relatively rare in cultivars from other countries and regions. About 48% of the wheats deficient for the Wx-B1 protein were from Australia and India. One Chinese cultivar lacked the WxD1 protein. While 9 Japanese cultivars were deficient in both the Wx-A1 and Wx-B1 proteins, no cultivars lacked both the Wx-A1 and Wx-D1 proteins, both the Wx-B1 and Wx-D1 proteins or all three Wx proteins. Two-dimensional gel electrophoresis revealed polymorphisms of the three Wx proteins that varied according to isoelectric points or molecular weight. The Wx-A1 gene coding the Wx-A1 protein and the Wx-B1 gene coding the Wx-B1 protein were localized in the distal regions of chromosome arms 7AS and 4AL, respectively, by deletion mapping using the deletion lines developed in the common wheat cultivar Chinese Spring.     

Specific features in using SNP markers developed for allopolyploid wheat

In this work, we analyzed 54 domestic cultivars of hexaploid (common) wheat Triticum aestivum L. (AABBDD genome) and accessions of tetraploid wheats of the Timopheevi group (AAGG) and rye Secale cereale (RR) using 21 SNP markers for common wheat. It was demonstrated that application of the SNP markers developed and verified for particular common wheat cultivars in allele-specific PCR analysis of other cultivars with different geographic origins could lead to an incorrect estimation of the similarity between the genotypes tested. The studied SNP markers of common wheat are inappropriate for analyzing genomes of other cereal species, in particular, T. timopheevii wheats and rye S. cereale.     

Cytogenetic structure of common wheat cultivars from or introduced into Spain

Summary Chromosome arrangements of twenty-eight cultivars of common wheat, Triticum aestivum L., from or introduced into Spain are compared with that of Chinese Spring taken as a pattern. All the cultivars analyzed differ from Chinese Spring by one or two reciprocal translocations. When 12 out of 28 cultivars were compared it was concluded that a minimum number of thirteen interchanges are present, involving at least ten different chromosomes of the complement. The interest of a reappraisal of the rôle of interchanges in the evolution of Gramineae is pointed out.     

Seedling root response of some Kenyan bread wheat cultivars grown in acid nutrient culture solution containing aluminum

The objective of this study was to determine whether a series of Kenyan bread wheat cultivars differed in tolerance to aluminum toxicity. Fourteen Kenyan wheat cultivars representing current and former widely grown cultivars of diverse pedigree origin, and two control cultivars, Maringa (Al-tolerant) and Siete Cerros (Al-susceptible), were tested in solution cultures with 0 (control), 148, 593, and 2370 M Al at pH 4.6. Highly significant (p0.01) differences in seedling growth were observed among cultivars for root mass, root length and root tolerance index (RTI). Significant (p0.05) cultivar × treatment interactions were observed for root mass and RTI. All characters were negatively affected by increased Al concentration, with root length and root mass being affected the most. RTI is a commonly used index which measures the relative performance of individual cultivars with and without aluminum stress. High levels of tolerance to Al were identified in the Kenyan cultivars by evaluating RTI with this simple nutrient solution technique. Romany and Kenya Nyumbu had RTI values approaching those of the Al tolerant Brazilian cultivar Maringa, a spring wheat standard that has been used for high Al tolerance.     

Origin and diversity of North American hard spring wheats

Genetic diversity is an important safeguard against crop vulnerability to biotic and abiotic stresses. Coefficient-of-parentage (COP) values of 248 North American hard spring wheat (Triticum aestivum L. em. Thell) cultivars released from 1901 to 1991 were used to estimate the genetic similarity of cultivars. COP values were used: to (1) quantify germ plasm sources and their contributions to the North American hard spring wheat gene pool; (2) measure changes in genetic diversity through time; and (3) identify major groupings of related cultivars. Landraces and local cultivars that contributed to the formation of the gene pool were: spring wheat (64%), winter wheat (16%), T. turgidum var. durum L. (10%), and T. turgidum var. emmer L. (8%). Fife, Hard Red Calcutta, and Turkey Red accounted for 18%, 13%, and 8%, respectively, of the hard spring wheat origins. Era and Butte in the US, and Neepawa and HY 320 in Canada, were the most commonly used named parents of cultivars released from 1981 to 1991. Both Canada and US had the greatest level of similarity among new cultivar releases in the 1930s (Canada: r=0.39, US: r=0.34). Genetic similarity in the US declined to r=0.14 in the 1940s and remained relatively constant thereafter. Similarity among released Canadian cultivars remained relatively high until the 1970s when the introduction of new market classes resulted in a 50% reduction in genetic similarity to approximately the same level of similarity found in the US. Cluster analysis was used to group cultivars released after 1941 into 13 clusters of similar genotypes. The cultivar clusters may have value for the stratified sampling of spring wheat germ plasm or in identifying diverse germ plasm for intermating.Contribution of the Idaho Agric. Exp. Stn. publication no. 95731. Missouri Pub. No. 12338     

RFLP patterns of gliadin alleles in Triticum aestivum L.: implications for analysis of the organization and evolution of complex loci

A correspondence between RFLP patterns and gliadin alleles at the Gli-1 and Gli-2 loci was established in a set of 70 common wheat (T.aestivum L.) cultivars using -gliadin (K32) and -gliadin (pTU1) specific probes. All Gli-B1 and Gli-D1 alleles which differed in encoded -gliadins showed definite RFLP patterns after hybridization with the K32 probe. Two groups of Gli-B1 alleles, Gli-B1b-like and Gli-B1e-like, were identified, and these could originate from distinct genotypes of the presumptive donor of the B-genome. Intralocus recombination and/or gene conversion as well as small deletions, gene silencing and gene amplification were assumed to be responsible for the origin of new gliadin alleles. Silent -gliadin sequences were shown to exist in all of the genotypes studied. K32 also differentiated Gli-A1a from all other Gli-A1 alleles as well as the Gli-B11 allele in cultivars carrying the 1B/1R (wheat/rye) translocation. PTU1 was shown to recognize several Gli-A2 alleles, but not the Gli-B2 or Gli-D2 alleles. Moreover, this probe hybridized to chromosome 1R sequences suggesting the existence of rye gene(s), probably silent, for -gliadin-like proteins on chromosome 1R.     

Wheat growth responses of cultivars to H+ concentration

Shoot length (cm), shoot fresh weight (g/pot), root length (cm), and root fresh weight (g/pot) were measured on six cultivars of wheat (Triticum aestivum L. cv Saluda, C9733, Gore, Stacy, FL301, and FL302) grown at pH 6.0, 5.5, 5.0, 4.5, or 4.0 for 14 days in white quartz flintshot sand. Plants were watered on alternate days with pH-adjusted buffer solutions. All measured plant parameters decreased as H⁺ concentration increased from pH 6.0 to 4.0. Decreased lengths of shoots and roots were similar among the cultivars as the pH decreased. This indicated a uniform response of wheat cultivars to excess H⁺ concentration in the soil solution; however, the decrease in shoot and root length was only about 50% as large as was previously reported for sorghum [Sorghum bicolor (L.) Moench.].     

Identification of C-banded chromosomes in meiosis of common wheat,Triticum aestivum L.

Summary The C-banding pattern of nine meiotic chromosomes of common wheat (Triticum aestivum L.) as described. In F₁s of crosses between monosomics of Chinese Spring and two Spanish wheat cultivars, univalent chromosomes were used to aid the recognition and analysis of the C-banding pattern for the individual chromosomes. The identification of one chromosome involved in one translocation in Chinese Spring x Pané 247 has been made through heterochromatin bands observed in the chromosomes involved in multivalents.     

Cultivar and cultivar x environment effects on the development of callus and polyhaploid plants from anther cultures of wheat

Summary Plants of three common wheat (Triticum aestivum L. em. Thell) cultivars and one randomly selected doubled-haploid line derived by anther culture from each of the three cultivars were each grown in three environments, a field environment, a greenhouse environment, and a growth chamber environment. Anthers containing largely miduninucleate to late uninucleate microspores were cultured and calli were induced to regenerate plants in order to assess the effects of cultivar, cultivar family (cultivar and corresponding doubled-haploid derivative), anther-donor plant environment, and cultivar X environment interaction on androgenic responses. Large differences in response were observed among cultivars as well as between cultivars and doubled-haploids. Differences between cultivar and doubled-haploid within cultivar family usually resulted from higher frequency of response in the cultivar, contrary to the hypothesis that anther culture per se constitutes a general selective device for superior androgenic responses. Also, in a second experiment, anther callusing frequency was greater in the cultivar Kitt than in any of five unique doubled-haploid lines derived from Kitt. Significant effects were also observed in the first experiment for the interactions of cultivar family X environment as well as doubled-haploid vs. cultivar X environment, although the effect of environment itself was less significant than these interactions.Contribution from the USDA, SEA, AR, Beltsville, Md, and the Department of Agronomy, University of Maryland, College Park, Md, as scientific article No. A-3413, contribution No. 6486     

Identification and chromosomal location of four subfamilies of the rubisco small subunit genes in common wheat

Summary Three different 3 noncoding sequences of wheat rubisco small subunit (SSU) genes (RbcS) were used as probes to identify the gene members of different RbcS subfamilies in the common wheat cultivar Chinese Spring (CS). All genes of the wheat RbcS multigene family were previously assigned to the long arm of homoeologous group 5 and to the short arm of homoeologous group 2 chromosomes of cv CS. Extracted DNA from various aneuploids of these homoeologous groups was digested with four restriction enzymes and hybridized with three different 3 noncoding sequences of wheat SSU clones. All RbcS genes located on the long arm of homoeologous group 5 chromosomes were found to comprise a single subfamily, while those located on the short arm of group 2 comprised three subfamilies. Each of the ancestral diploid genomes A, B, and D has at least one representative gene in each subfamily, suggesting that the divergence into subfamilies preceded the differentiation into species. This divergence of the RbcS genes, which is presumably accompanied by a similar divergence in the 5 region, may lead to differential expression of various subfamilies in different tissues and in different developmental stages, in response to different environmental conditions. Moreover, members of one subfamily that belong to different genomes may have diverged also in the coding sequence and, consequently, code for distinguishable SSU. It is assumed that such utilization of the RbcS multigene family increases the adaptability and phenotypic plasticity of common wheat over its diploid progenitors.     

Introgression of diverse genes for resistance to rusts into an improved wheat variety, Kalyansona

Breeding for resistance to the three rusts of wheat usually requires incorporation of genetically independent factors conferring resistance to each rust. Linked resistance genes in some alien translocation stocks permit concurrent transference of resistance for more than one rust. Alien derived resistances, however, are often reported to be associated with reduced yield and other undesirable characters. In our experience, backcross breeding when given a limited number of backcrosses (3–6) and with suitable selection procedures has resulted in lines giving yields higher or comparable to the recurrent wheat parent Kalyansona and resistance to one, two or all three rusts without any adverse effects. Some of the rust resistant derivatives also show resistance to Neovossia indica (Karnal bunt). The derivatives thus developed when used as parents in a breeding programme have produced several improved cultivars with high yields, superior grains and diversity for resistance to rust pathogens. One of the cultivars, named Vaishali (DL784-3), has been officially released for cultivation in the country.     

The pattern of amyloplast DNA accumulation during wheat endosperm development

The accumulation of amyloplast DNA during endosperm development was studied in two cultivars of spring wheat, Triticum aestivum L. Chinese Spring (CS) and Spica, small and relatively larger-grained cultivars, respectively. Endosperms were isolated between 9 and 45 days post anthesis (dpa) and the amyloplast DNA content of endosperm nucleic-acid extracts was measured by quantitative hybridisation with a homologous chloroplast-DNA probe. The endosperm cells of CS and Spica accumulated amyloplast DNA during development in a similar way. In both cultivars there was a large increase in the amount of plastid DNA (ptDNA) per endosperm between 9 and about 15 dpa, after which there was no further increase. Because nuclear DNA continued to accumulate until 24 dpa, the percentage contribution of amyloplast DNA to total DNA fluctuated in both cultivars during development, reaching maxima at 12 dpa of about 1.00% and 0.85%, and dropping to apparently constant levels of 0.60% and 0.52% in CS and Spica, respectively, by 24 dpa. In both cultivars, the average number of ptDNA copies per amyloplast was calculated to increase from about 10 copies at 9 dpa to about 50 copies in the mature amyloplasts at 31 dpa. However, the heavier endosperms of Spica contain more cells than those of CS and the varieties therefore differed in the amount of ptDNA that accumulated per endosperm: Spica endosperms accumulated 110 ng of ptDNA by 15 dpa, compared with only 85 ng in CS. The apparent accumulation of ptDNA copies in wheat amyloplasts during endosperm development contrasts with the decline in chloroplast-DNA copies in wheat chloroplasts during leaf development.Abbreviations CS Chinese Spring - ctDNA chloroplast DNA - dpa days post anthesis - kbp 10³ base pairs - nDNA nuclear DNA - ptDNA plastid DNA - mtDNA mitochondrial DNA     

Identification of RFLP markers linked to the cereal cyst nematode resistance gene (Cre) in wheat

The cereal cyst nematode (CCN) (Heterodera avenae Woll.) is an economically damaging pest of wheat in many of the worlds cereal growing areas. The development of CCN-resistant cultivars may be accelerated by the use of molecular markers. The Cre gene of the wheat line AUS 10894 confers resistance to CCN. Using a pair of near-isogenic lines (NILs) that should differ only in a small chromosome segment containing the Cre locus, we screened 58 group-2 probes and found two (Tag605 and CDO588) that detect polymorphism between the NILs. Nulli-tetrasomic and ditelosomic lines confirmed that the restriction fragment length polymorphism (RFLP) markers identified were derived from the long arm of wheat chromosome 2. Crosses between AUS 10894 and Spear and the NIL AP and its recurrent parent Prins were used to produce F₂ populations that gave the expected 31 segregation ratio for the resistance gene. Linkage analysis identified two RFLP markers flanking the resistance gene. Xglk605 and Xcdo588 mapped 7.3 cM (LOD=6.0) and 8.4 cM (LOD=6.7), respectively, from the Cre locus.     

New cytoplasmic male sterility sources in common wheat: Their genetical and breeding considerations

Summary Nuclei from Triticum aestivum L. cultivars Penjamo 62 and Siete Cerros 66 were introduced into the cytoplasms of different species of Aegilops and some subspecies (varieties) of T. dicoccoides by backcrossing. The sterile alloplasmic lines obtained were compared with the normal cultivars used as the recurrent pollen parents. According to the cytoplasmic effect, these cytoplasms were subdivided into three main groups. The first group possesses C^u type cytoplasm, the second one possesses M type and the third group includes S, C and G type. Promising male sterile cytoplasms for hybrid wheat production were found in Ae. mutica, Ae. triuncialis and T. dicoccoides var. spontaneovillosum. Based on these results and other information some conjectures were made concerning hybrid wheat breeding and phylogenetic differentiations of the cytoplasm.     

Polymorphism and chromosomal location of endogenous α-amylase inhibitor genes in common wheat

Summary Polymorphism of an endogenous -amylase inhibitor in wheat was studied using iso-electric focusing followed by monoclonal antibody — based immunoblotting. Ten isoforms of the inhibitor detected in common wheat and its wild counterparts were assigned to five homoeologous loci. Three -amylase inhibitor loci (Isa-1) were identified in common wheat and located on the long arms of chromosomes 2A, 2B and 2D. In a sample of 27 bread wheats, eight durum wheats, and 12 diploid wheat relatives, amphiploids and triticales, a high resolution isoelectric-focusing separation demonstrated two active and one null allele at the Isa-A1, two alleles at the Isa-B1, one allele at the Isa-D1, four alleles at the Isa-S1, and one allele at the Isa-G1 locus. The most frequent electrophoretic pattern of common wheat cultivars consisted of two isoforms, encoded respectively by the Isa-B1b, Isa-D1 a alleles and the Isa-Alnull allele. All the durum wheats had only one inhibitor form controlled by allele Isa-B1b, which was accompanied by the null allele at the Isa-A1 locus.Contribution No. 210 of the Food Science Department, University of Manitoba     

In vitro microspore reaction of different German wheat cultivars

Summary The in vitro microspore androgenesis reaction of 25 commercial German spring (including 4 Triticum durum) and 50 winter wheat cultivars was investigated. Tremendous genotypical differences were found in microspore response. The best-responding winter wheat cultivai, Florida, is characterized by the presence of a 1B/1R wheat-rye translocation chromosome. The significance of this finding and other genetic systems for future use of haploids in plant breeding is discussed.     

Survival of five wheat curl mite,Aceria tosichilla Keifer (Acari:Eriophyidae), strains on mite resistant wheat

The survival of the wheat curl mite (WCM), Aceria tosichilla Keifer, on five sources of resistant wheat (Triticum aestivum L.) was determined for collections of mites from Kansas (including a strain adapted to TAM 107), South Dakota and Texas, USA and Alberta, Canada. Sources of resistance to Aegilops squarrosa L. and Agropyron elongatum (Host) were resistant to WCMs from South Dakota and Alberta, but susceptible to WCMs from Kansas and Texas. Two wheats with resistance to rye (Secale cereale L.), PI 475772 and TAM 107, were resistant to all WCM collections except the strain from Kansas that was selected for adaptation to TAM 107. A common wheat (PI 222655) was resistant to all WCM collections except the one from Alberta, Canada. Because WCMs have overcome the resistance of TAM 107 in Kansas, the only resistance now available in commercial cultivars may be lost. Results indicate that PI222655 is the best source of resistance to replace TAM 107 in the USA but it may not be effective in Canada. Resistance to Ae. squarrosa and A. elongatum could be deployed against WCMs in Alberta and South Dakota but these sources may not be effective in Kansas and Texas. However, one WCM collection from each location may not represent the general mite population of an area. Therefore, any new sources of resistance should be evaluated fully against WCMs from areas where they are likely to be used in commercial cultivars.     

Genetic control of endosperm proteins in wheat

Summary Total endosperm proteins extracted from both several common wheat cultivars and some intervarietal substitution lines derived from them were fractionated according to their molecular weight in a high resolution one-dimensional gel electrophoresis. The four donor cultivars and the recipient one — Chinese Spring, possessed differentially migrating protein bands in the fractions of high molecular weight (HMW) glutenins and gliadins. Several of these bands were identified for the first time in this study. By utilizing intervarietal substitution lines the control of the HMW glutenins and gliadins by chromosomes of homoeologous group 1 was either reaffirmed or, for the new bands, established. Several HMW gliadin subunits showed a considerable variation in their staining intensity in the intervarietal substitution lines indicating that their expression was dependent on the genetic background.This paper is based on a portion of a dissertation to be submitted by G. Galili in partial fulfilment of the Ph.D. requirements of the Feinberg Graduate School, The Weizmann Institute of Science, RehovotThe Marshall and Edith Korshak Professor of Plant Cytogenetics     

High-throughput genotyping for a polymorphism linked to soybean cyst nematode resistance gene Rhg4 by using TaqmanTM probes

An individual soybean breeder can generate over one hundred thousand new genotypes each year. The efficiency of selection in these populations could be improved if these genotypes were effectively screened with one DNA marker that identified an important gene, and if laboratory throughput was high and costs were low. Our aim was to develop a rapid genotyping procedure for resistance to the soybean cyst nematode. A high-throughput genotyping method was developed with fluorogenic probes to distinguish between two insertion polymorphisms in alleles of an AFLP marker that is located about 50 kbp from the Rhg4 gene candidate. The assay uses the 5 exonuclease activity of Taq polymerase in conjunction with fluorogenic probes for each allele. The method can be used for scoring the polymorphism in a recombinant inbred line population and for screening parent lines in a breeding program. The Taqman^TM method of determining genotype was accurate in 90% of scores in the RIL population compared to 95% accuracy with electrophoresis. Among 94 cultivars that are parents in our breeding program allele 2 that is derived from the sources of resistance to SCN was common in resistant cultivars (30 of 56) but rare in susceptible cultivars (3 of 38). Therefore, this method can be applied to automated large-scale genotyping for soybean breeding programs.     

Specificity of an antibody to a subunit of high-molecular-weight storage protein from wheat seed and its reaction with other cereal storage proteins (prolamins)

An antiserum to subunit 2 from the high-molecular-weight (HMW) subunits of the glutenin fraction of Triticum aestivum cv. Highbury was shown to react with related subunits from other cultivars of wheat. The reaction was measured quantitatively by laser nephelometry in polyethylene glycol phosphate-buffered saline after dissolving the HMW fraction in 0.1 M acetic acid; urea used to dissolve the HMW prolamins inhibited the reaction, in some cases at the low concentration of 0.06 M. A study of the comparative reactions of other cereal prolamins was made. D hordein, the homologous HMW protein of barley, showed less reaction, which was more inhibited by urea than the wheat subunits. Some -gliadins from the wheat cultivars Chinese Spring and Cheyenne reacted more strongly than the injected fraction and there was less inhibition by urea. A-, - and ₃ of wheat also reacted with the antiserum while a secalin of rye of M_r 40000 gave a weak reaction.Abbreviations HMW high molecular weight - PAGE polyacrylamide-gel electrophoresis - PBS phosphate-buffered saline - PE pyridylethylated - SDS sodium dodecyl sulphate