ITEMS FROM THE UNITED STATES

 

NORTH DAKOTA

 

USDA-ARS CEREAL CROPS RESEARCH UNIT

Northern Crop Science Laboratory, North Dakota State University, Fargo, ND 58078, USA.

Justin Faris, Timothy Friesen, Steven Xu, James Miller, Daryl Klindworth, Leonard Joppa, Karri Haen, Erik Doehler, Huangjun Lu, Kristin Simons, and Zhaohui Liu.

The construction of a BAC contig for chromosome walking at the Tsn1 locus in wheat. [p. 252-253]

Huangjun Lu, Karri M. Haen, John P. Fellers, Timothy L. Friesen, Steven W. Meinhardt, and Justin D. Faris.

Tsn1 conditions sensitivity to a host-selective proteinaceous toxin (Ptr ToxA) produced by the pathogenic fungus Pyrenophora tritici-repentis and plays an important role in pathogen-host recognition. A large F2 population consisting of 5,450 gametes was produced to develop a high-resolution map for positional cloning of the gene. High-resolution mapping delineated the Tsn1 gene to a 0.55 cM interval flanked by AFLP-derived markers Xfcg17 and Xfcg9 at 0.15 and 0.41 cM from the gene, respectively. More tightly linked markers were developed using chromosome walking in conjunction with complete sequencing of BACs identified in the Langdon durum BAC library. Although the Tsn1 gene lies within a recombination hot spot along the chromosome, our results indicate that recombination frequencies vary significantly within the BAC contig. From the regions that have been sequenced, we identified more than 10 genes, most of which are genes that encode cell wall-associated receptors or kinases. The product of the Tsn1 gene also may be a cell wall-associated protein that interacts with the toxin to manifest necrosis because plants having tsn1 or the null allele (deletion lines) are insensitive to Ptr ToxA. The cloning and characterization of Tsn1 will be helpful in better understanding the host-pathogen interaction.

Molecular cloning of the Q locus in wheat. [p. 253]

Kristin Simons, John P. Fellers, Harold Trick, Bikram S. Gill, and Justin D. Faris.

The Q locus played a major role in the domestication of polyploid wheat because it confers the square-headed phenotype and the free-threshing character, and it pleiotropically influences many other agronomically important traits. A physical contig spanning the Q locus on chromosome 5A was constructed using a T. monococcum BAC library. The 100-kb segment cosegregating with Q contained an APETELA2 (AP2)-like gene. This gene is a likely candidate for Q, because AP2 plays a major role in controlling floral homeotic gene expression in Arabidopsis. The AP2-like gene was sequenced from the free-threshing T. aestivum cultivar Chinese Spring, the free-threshing T. turgidum cultivar Langdon, and several nonfree-threshing wild relatives. Sequence comparisons revealed slight differences between free-threshing and nonfree-threshing species. EMS-treated T. aestivum lines were screened for mutations in the Q locus. Of six mutant lines, three were the result of large deletions encompassing the Q locus. The AP2-like gene in the remaining three lines had base substitutions that resulted in coding of a different amino acid or the alteration of a predicted exon/intron splice site. Transgenic individuals were created using a 5 kb subclone of a T. turgidum BAC containing the Q locus. These transgenic individuals mimicked the increased or decreased dosage effect of Q, suggesting the occurrence of silencing and over-expression, respectively.

Molecular mapping of resistance to Pyrenophora tritici-repentis race 5 and sensitivity to PtrToxB in wheat. [p. 253]

Justin D. Faris and Timothy L. Friesen.

Tan spot is an economically important foliar disease in the major wheat growing areas of the world. Multiple races of the pathogen have been characterized based on their ability to cause necrosis and/or chlorosis on differential wheat lines. Isolates of race 5 cause chlorosis only, and they produce a host-selective toxin designated Ptr ToxB that induces chlorosis when infiltrated into sensitive genotypes. We used the ITMI mapping population to identify genomic regions harboring QTL for resistance to fungal inoculations of PTR race 5 and to determine the chromosomal location of the gene conditioning sensitivity to Ptr ToxB. The toxin-sensitivity gene mapped to the distal tip of the short arm of chromosome 2B. This gene was responsible for the effects of a major QTL associated with resistance to the race 5 fungus and accounted for 69 percent of the phenotypic variation. Additional minor QTL were identified on the short arm of 2A, the long arm of 4A, and elsewhere on chromosome 2B. A multiple regression model consisting of the major QTL on 2BS identified by the toxin insensitivity gene, a marker underlying a minor QTL on 2B, a marker on 4AL, and an epistatic interaction accounted for 76 percent of the total phenotypic variation for resistance to PTR race 5. The results of this research indicate that Ptr ToxB is a major virulence factor, and the markers underlying significant QTL should be useful for introgression of resistance into adapted germ plasm.

Genetic and physical mapping of a gene conditioning sensitivity in wheat to a partially purified host-selective toxin produced by Stagonospora nodorum. [p. 253-254]

Zhaohui Liu, Justin D. Faris, Steven Meinhardt, Shaukat Ali, Jack B. Rasmussen, and Timothy L. Friesen.

Stagonospora nodorum is the causal agent of wheat leaf and glume blotch, an economically important disease in many wheat-growing areas throughout the world. Using filtration, ion-exchange and gel-filtration chromatography, we partially purified a toxin from culture filtrates of isolate Sn2000. This toxin, designated as SnTox1, showed selective action on several different wheat genotypes indicating that it is a host-selective toxin (HST). The ITMI mapping population was evaluated for toxin reaction and used to map the host gene conditioning sensitivity. This gene, designated as Snn1, was genetically mapped to the distal end of chromosome 1BS. The wheat cultivar Chinese Spring and all CS nullisomic-tetrasomic lines were sensitive to the toxin, with the exception of N1BT1D. Insensitivity also was observed when the 1B chromosome of CS was substituted by the 1B chromosome of an insensitive accession of Triticum dicoccoides. These results indicate that the toxin sensitivity gene resides on chromosome 1B, and suggest that sensitivity is dominant. A series of 1BS deletion lines were used to physically localize the sensitivity gene. Physical mapping indicated that Snn1 lies within a major gene-rich region on 1BS.

QTL analysis and mapping of resistance to Stagonospora nodorum leaf blotch in wheat. [p. 254]

Zhaohui Liu, Tim L. Friesen, Steven Meinhardt, Shaukat Ali, Jack B. Rasmussen, and Justin D. Faris.

Stagonospora nodurum leaf blotch (SNB) is an economically important foliar disease in the major wheat-growing areas of the world. Utilization of host resistance is considered to be the most important and preferred method to control disease. In related work, we identified a host-selective toxin (SnTox1) produced by the isolate Sn2000 and mapped the gene (Snn1) conditioning sensitivity to chromosome 1BS. Here, we screened the ITMI mapping population and cytogenetic stocks, including nullisomic-tetrasomic lines and CS-T. dicoccoides (CS-DIC) substitution lines, with isolate Sn2000 to identify QTL associated with resistance to SNB. QTL analysis revealed that Snn1 underlies a major QTL and explained 58.3, 47.7, and 27 percent of the phenotypic variation for 5, 7, and 10-day readings, respectively. This 1BS QTL, a minor QTL on chromosome 4BL, and an interaction between Snn1 and a marker on chromosome 2B, explained as much as 66 percent of the total phenotypic variation. An additional QTL on chromosome 7BL was identified for the 10-day readings. Toxin sensitivity was highly correlated with chlorotic flecking on the leaves, which occurred in the early stages of disease development. N1BT1D and CS-DIC 1B were absent of chlorotic flecking and less susceptible to the fungus. These results in combination with the decreased effects of the 1BS QTL from 5 to 7 to 10 days indicate that the toxin is a major virulence factor, and is most effective in the early stages of the interaction.

Evaluation of synthetic hexaploid wheats for seedling resistance to tan spot and Stagonospora nodorum blotch. [p. 254]

Steven S. Xu and Timothy L. Friesen.

Production of synthetic hexaploid wheat (SHW or synthetic) lines (2n = 6x = 42, AABBDD) is a practical way to generate a useful germ plasm source for the transfer of desirable traits from Ae. tauschii and tetraploid wheat to bread wheat. The Wide Hybridization Program at CIMMYT recently selected and characterized two sets of elite SHW lines (Elite 1 and Elite 2). Thus far, some important traits such as agronomic performance, quality traits, and resistance to various diseases have been evaluated. However, their resistance to tan spot and SNB has not been evaluated. Tan spot and SNB are important foliar diseases of bread wheat and durum wheat. These two diseases have ability to cause serious yield losses. Because the majority of current bread and durum wheat cultivars are susceptible, there is a need to find new sources of high level resistance to tan spot and SNB and transfer the resistance to local cultivars. In this study, 120 elite CIMMYT SHW lines and their durum wheat parents were inoculated with P. tritici-repentis race 1 and a standard field isolate (Sn2000) of S. nodorum, respectively, in two separate, three-replication experiments. The seedling reactions to P. tritici-repentis and S. nodorum were evaluated 7 and 10 d postinoculation, respectively. The plant leaves also were infiltrated with the host selective toxin Ptr ToxA at the two-leaf stage and sensitivity was evaluated 3-4 d post infiltration. As expected, most SHW lines were the same as their durum parents in their sensitivity to Ptr ToxA, because the sensitivity locus Tsn1 is located on chromosome 5B. However, a few of the synthetics were different from their durum parents, suggesting that heterozygosity and heterogeneity might exist in some of the SHW lines and durum parents. The toxin sensitivity significantly increased susceptibility of the synthetics to tan spot but had no significant effects on durum parents. The data showed that 56 (46.7 %) and 36 (30.0 %) SHW lines were resistant to tan spot and SNB, respectively, whereas resistance was almost absent in the durum parents. These results suggest that the elite CIMMYT synthetics are an excellent source of new resistance to tan spot and SNB and should be useful in developing new resistant cultivars and adapted germplasm in bread wheat.characterization of an elite subset. Ann Wheat Newslet 46:76-79.

Chromosomal locations of novel glutenin subunits and gliadins in wild emmer wheat. [p. 255]

Steven S. Xu, Khalil Khan, Daryl L. Klindworth, Justin D. Faris, Gloria Nygard.

Triticum turgidum subsp. dicoccoides (DIC), known as wild emmer, is the tetraploid progenitor of durum and bread wheat. Wild emmer has many useful traits such as pest resistance, high protein content, and unique protein compositions. The glutenin and gliadin proteins of wild emmer wheat have potential for improvement of durum wheat quality. The objective of this study was to determine the chromosomes controlling the high molecular weight (HMW) glutenin subunits and gliadin proteins present in three T. turgidum subsp. dicoccoides accessions (Israel-A, PI-481521, and PI-478742), which were used as chromosome donors in Langdon durum-T. turgidum subsp. dicoccoides (LDN-DIC) chromosome substitution lines. The three T. turgidum subsp. dicoccoides accessions, their respective LDN-DIC substitution lines, and a number of controls with known HMW-glutenin subunits were analyzed by SDS-PAGE, Urea/SDS-PAGE, and A-PAGE. The results revealed that all three T. turgidum subsp. dicoccoides accessions possess Glu-1A alleles that are the same as or similar to those reported previously. However, each T. turgidum subsp. dicoccoides accession had a unique Glu-B1 allele. The new Glu-B1 alleles were designated as Glu-B1be in Israel-A, Glu-B1bf in PI-481521, and Glu-B1bg in PI-478742. Results from A-PAGE indicated that there were eight, twelve, and nine unique gliadin proteins bands, which were assigned to specific chromosomes, in PI-481521, PI-478742, and Israel-A, respectively. The identified glutenin and gliadin proteins in the LDN-DIC substitution lines provide the basis for evaluating their effects on end-use quality, and they are also useful biochemical markers for identifying specific T. turgidum subsp. dicoccoides chromosomes or chromosome segments.

Agronomic and quality characteristics of T1AS·1AL-1DL translocation lines of durum wheat carrying Glu-D1d. [p. 255]

Daryl L. Klindworth, Gary A. Hareland, Elias M. Elias, and Steven S. Xu.

Markets for durum wheat could be expanded if cultivars with dual-purpose end-use could be developed. The Glu-D1d allele encoding glutenin subunits 5+10 imparts good baking quality to hexaploid wheat. The objective of this study was to test the agronomic and baking quality of T1AS·1AL-1DL translocation lines of durum wheat with Glu-D1d. Translocation lines were classified according to the presence of either low-molecular weight I (LMWI; weak gluten) or LMWII (strong gluten) banding patterns conditioned by the Glu-B3 locus. Advanced generation translocation lines in a Renville background were grown in yield trials conducted at two locations in North Dakota from 1998 through 2002. Translocation lines were milled and mixing and baking characteristics determined. Only two translocation lines did not differ statistically from Renville for yield and were similar to Renville for lodging score, heading date, and plant height. The translocation lines had reduced thousand kernel weight and a high 'G x E' interaction for farinogram characteristics. Compared to Renville, mean loaf volumes were not improved. Translocation lines having LMWI had better mixing stability and loaf volume than lines having LMWII. Although 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.

High-throughput marker identification and mapping in wheat using TRAPs (Target Region Amplification Polymorphism). [p. 255-256]

Justin D. Faris, Steven S. Xu, Zhaohui Liu, and Jinguo Hu .

High-throughput marker technologies are necessary for the rapid mapping of plant genomes to identify genomic regions harboring genes governing desirable traits and for marker-assisted selection. The recently developed TRAP technique employs an 18mer random primer in combination with a fixed 18mer primer designed based on known EST sequences to amplify genomic fragments. The random primers are 3' end-labeled with IR dye 700 or IR dye 800 for autodetection on a Li-Cor Global DNA Sequencer. We applied the TRAP technique to two sets of tetraploid Langdon durum-T. turgidum subsp. dicoccoides (LDN-DIC) disomic chromosome substitution lines to determine the number and chromosomal locations of polymorphic TRAP markers. The LDN-DIC (PI481521) disomic substitution set has been characterized with 37 PCR reactions resulting in the identification of 642 TRAP markers. The markers were distributed among all 14 chromosomes, and the number per chromosome ranged from 19 (3B) to 72 (7A). The second disomic substitution set [LDN-DIC (PI4787420] has been partially characterized with 91 polymorphic markers identified from five PCR reactions. On average, 17 polymorphic markers were observed per PCR reaction in the LDN-DIC lines. In addition, we assessed the number of polymorphic markers and genetic map locations of TRAPs in a hexaploid wheat recombinant inbred population derived from 'BR34/Grandin'. In this population, we observed an average of 20 polymorphic markers per PCR reaction. The TRAP markers are useful for genome characterization, tagging desirable genes, and high-throughput mapping of wheat populations.

Genetic stocks and germ plasm in tetraploid and hexaploid wheat available for distribution. [p. 256-257]

Steven S. Xu, Justin D. Faris, Daryl L. Klindworth.

The mission of our wheat germ plasm enhancement program primarily includes the development and characterization of new genetic stocks and germ plasm in durum and hard red spring wheat. Leonard R. Joppa (ARS retired) and the late Norman D. Williams developed a number of valuable genetic stocks and germ plasms using classical cytogenetic approaches. Many of them have not been characterized and released to the public. We have engaged in efforts in characterizing these materials using molecular cytogenetics and DNA marker technologies. Some of these lines also have been recently evaluated for resistance to various diseases, Hessian fly, and seed-storage-protein compositions. Here, we summarize the genetic stocks and germ plasm available for distribution. We are able to provide a small seed sample (20-30 seeds/line) upon request.

Langdon durum-T. turgidum subsp. dicoccoides disomic substitution lines. Three sets of Langdon durum-T. turgidum subsp. dicoccoides (LDN-DIC) disomic substitution lines were developed by L.R. Joppa using T. turgidum subsp. dicoccoides accessions Israel-A, PI481521, and PI478742 as the chromosome donor in Langdon background. The set based on PI481521 has all 14 chromosome substitutions available, but the substitution for chromosome 2B for the set based on Israel-A and three substitutions (2A, 3A, and 3B) in the set based on PI478742 are not available.

Langdon durum-Ae. tauschii SH wheat. Dr. Leonard R. Joppa developed a number of spontaneous synthetic hexaploid wheat from partially fertile hybrids between LDN and different Ae. tauschii accessions in the 1980s. We recently developed a new synthetic line from a cross between LDN and Ae. tauschii PI476874, which has a tough rachis. Some Ae. tauschii accessions were received from National Small Grains Collection (NSGC), Aberdeen, ID, others were provided respectively by E.R. Kerber (Agriculture and Agri-Food Canada, Winnipeg, Manitoba, Canada) and E. Nevo (University of Haifa, Haifa, Israel). Except for the synthetic line from cross 'LDN/PI 268210' was named as Largo and released as greenbug-resistant germ plasm, other lines have not been characterized previously. These synthetics have recently been evaluated for resistance to tan spot, SNB, leaf and stem rust, and Hessian fly. We currently are evaluating their resistance to FHB and seed-storage protein compositions. The synthetics that are available for seed distribution are listed in Table 1 .

Durum wheat T1AS·1AL-1DL translocation lines carrying Glu-D1d. Four translocation lines with the pedigree 'LDN 1D (1A)/LEN//LDN/3/2*Renville' and with glutenin subunits 1Dx5 and 1Dy10 from the Glu-D1d allele are available. These lines were produced in an effort to develop dual-purpose (good baking and pasta quality) durum wheat. The lines are identified as L092, L252, S99B33, and S99B34. Three of the lines carry the LMWII-banding pattern derived from Renville and conditioned by the Glu-B3 gene. The fourth line, L252, carries the LMWI-banding pattern derived from LDN. Quality tests have indicated L252 has better mixing traits and slightly better loaf volume than the translocation lines with LMWII. In trials conducted in North Dakota from 2000-02, S99B33 and S99B34 were the highest yielding of the translocation lines and similar in yield to Renville. These lines should be useful to breeders attempting to produce dual-purpose durum or for cereal chemists studying effects of Glu-D1d in a durum background.

Induced mutants in hexaploid and tetraploid wheat and miscellaneous stocks. N.D. Williams induced many mutants in hexaploid and tetraploid wheat, primarily through application of EMS to seeds. Male-sterile mutants in hexaploid wheat include the FS2, FS3, FS6, FS20, and FS24 mutants that have been reported in the literature. Additional recessive male sterile mutants that have not been reported in the literature are also available, and all are known to be allelic to either ms1 or ms5. Chlorina mutants are available in both hexaploid and tetraploid wheat that have been reported in the literature. Additional abnormal chlorophyll mutants, such as virescent and albino, genetics have not been studied. Lines derived from conventional breeding techniques include a durum line carrying the blue aleurone trait and lines carrying genes conditioning the branched spike trait in durum wheat.

Publications. [p. 257]

• Faris JD, Friebe B, and Gill BS. 2003. Genome mapping. In: Encyclopedia of Grain Science. (In press).
• Faris JD, Fellers JP, Brooks SA, and Gill BS. 2003. A bacterial artificial chromosome contig spanning the major domestication locus Q in wheat and identification of a candidate gene. Genetics 164: 311-321.
• Friesen TL, Xu SS, Faris JD, Rasmussen JB, Miller JD, and Harris MO. 2003. Evaluation of Langdon durum-Aegilops tauschii synthetic hexaploid wheats for their seedling reaction to tan spot, Stagonospora leaf blotch, leaf rust, stem rust, and Hessian fly. In: Proc 10th Internat Wheat Genet Symp (Pogna NE, Romano M, Pogna EA, and Galterio G eds). Istituto Sperimantale per la Cerealicoltura, Rome, Italy. 3:1133-1135.
• Haen KM, Lu HJ, Freisen TL, and Faris JD. 2004. Genomic targeting and high-resolution mapping of the Tsn1 gene in wheat. Crop Sci (In press).
• Maleki L, Faris JD, Bowden RL, Gill BS, and Fellers JP. 2003. Physical and genetic mapping of wheat kinase analogs and NBS-LRR resistance gene analogs. Crop Sci 43:660-670.
• Xu SS, Hu J, and Faris JD. 2003. Molecular characterization of Langdon durum-Triticum dicoccoides chromosome substitution lines using TRAP (target region amplification polymorphism) markers. In: Proc 10th Internat Wheat Genet Symp (Pogna NE, Romano M, Pogna EA, and Galterio G eds). Istituto Sperimantale per la Cerealicoltura, Rome, Italy. 1:91-94.
• Xu SS, Khan K, Klindworth DL, Faris JD, and Nygard G. 2004. Chromosomal locations of genes for novel glutenin subunits and gliadins in wild emmer wheat (Triticum tugidum L. var. dicoccoides). Theor Appl Genet 108 (In press).
• Zou JJ, Singh RJ, Lee J, Xu SS, Cregan PB, and Hymowitz T. 2003. Assignment of molecular linkage groups to soybean chromosomes by primary trisomics. Theor Appl Genet 107:745-750.