Items from the United States - North Dakota.

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, and Huangjun Lu.

Genomic targeting and high-resolution mapping of the Tsn1 locus in wheat. [p. 215]

Karri M. Haen and Justin D. Faris.

Tan spot, caused by the fungal pathogen P. tritici-repentis (PTR) causes severe yield losses in wheat and durum. The Tsn1 gene acts dominantly to confer sensitivity to a host-selective proteinacious toxin (Ptr ToxA) produced by the fungus. Our objectives were to 1) target markers to the Tsn1 genomic region and 2) develop a high-resolution map of the Tsn1 locus. The techniques of methyl sensitive and traditional AFLP and cDNA-AFLP were combined with BSA using RSLs and chromosome-deletion lines to target markers to the Tsn1 genomic region. Over 500 primer combinations were screened resulting in the identification of 47 positive fragments that were converted to RFLP markers and mapped in segregating populations. High-resolution mapping was performed by analyzing 1,266 gametes derived from a cross between the cultivar Kulm and the synthetic hexaploid W-7976. Nineteen low-copy markers closely linked to Tsn1 have been identified, and two markers flank the Tsn1 locus at 0.2 and 0.4 cM. Tsn1 is located within a gene-rich recombination hot spot region. Based on estimated physical to genetic distance ratios within the region, the predicted physical distance separating the flanking markers may be less than 200 kb. Therefore, these markers will serve as a basis for the map-based cloning of Tsn1. The isolation of Tsn1 will further our knowledge of wheat­tan spot interactions and host-pathogen interactions in general.

A BAC contig spanning the major domestication locus Q in wheat and identification of a candidate gene. [p. 215]

Justin D. Faris, John P. Fellers, Steve Brooks, and Bikram S. Gill.

The Q locus played a major role in the domestication of wheat because it confers the free-threshing character and influences many other agronomically important traits. We constructed a physical contig spanning the Q locus using a T. monococcum BAC library. Three chromosome walking steps were performed by complete sequencing of BACs and identification of low-copy markers through similarity searches of database sequences. The BAC contig spans a physical distance of about 300 kb corresponding to a genetic distance of 0.9 cM. The physical map of T. monococcum had perfect colinearity with the genetic map of wheat chromosome arm 5AL. Recombination data in conjunction with analysis of fast-neutron deletions confirmed that the contig spanned the Q locus. The Q gene was narrowed to a 100-kb segment that contains an APETALA2 (AP2)-like gene that cosegregates with Q. AP2 is known to play a major role in controlling floral homeotic gene expression and thus, is an excellent candidate for Q.

 

Genomic analysis of segregation distortion and recombination in durum wheat. [p. 216]

Justin D. Faris and Huangjun Lu.

Distorted segregation ratios of genetic markers are often observed in progeny of inter- and intraspecific hybrids and may result from competition among gametes or abortion of the gamete or zygote. Homoeologous group 5 chromosomes of the Triticeae are known to possess segregation distortion factors, and detailed analysis of Ae. tauschii chromosome 5D indicated that it possessed at least three different segregation distortion loci that conferred gametophytic competition among pollen when an F1 plant was used as a male parent. In this study, we developed genetic linkage maps of chromosome 5B in male and female populations derived from Langdon (LDN) durum and Langdon/T. turgidum subsp. dicoccoides 5B disomic chromosome substitution (LDN-DIC 5B). Genetic markers in the female population had expected segregation ratios, and the recombination frequencies were similar to those found along chromosome 5B in other wheat and durum populations. However, segregation ratios of markers in the male population were highly skewed in favor of LDN alleles, and recombination frequencies were severely suppressed. At least two distorter loci appear to be present along chromosome 5B of durum, and they are likely homoeoalleles of those identified in Ae. tauschii. We are now in the process of assessing chromosome 5A in for segregation distortion in crosses derived from 'LDN/LDN-DIC 5A'. This research agrees with previous research in that segregation distortion is likely the result of gametophytic competition for preferential fertilization in a heterogeneous pollen population, and it suggests that this phenomenon may lead to reduced recombination frequencies.

 

Identification and characterization of a durum/Aegilops speltoides chromosome translocation conferring resistance to stem rust. [p. 216]

Erik Doehler, Justin Faris, Steven Xu, James Miller, and Leonard Joppa.

Homozygous durum/Ae. speltoides translocation lines were produced by homoeologous recombination and tested for reaction to the stem rust pathogen. The durum parent is a universal susceptible line, but the Ae. speltoides chromosome translocation conditions seedling resistance to at least nine races of stem rust. RFLP analysis indicates that the translocation chromosome involved is durum chromosome 2B, and it consists of the short arm and most of the long arm derived from Ae. speltoides. Experiments are underway to identify the Ae. speltoides chromosome involved in the translocation, to determine if the gene(s) on the translocated segment confer resistance to all races of stem rust, and to determine if this gene(s) is the same or different from Sr32 and Sr39, which also were derived from Ae. speltoides by translocations to hexaploid wheat chromosome 2B.

 

Disease evaluation of 40 synthetic hexaploid wheat lines for their seedling reaction to tan spot and Stagonospora leaf blotch. [p. 216]

Timothy L. Friesen, Steven S. Xu, and Justin D. Faris,

Forty SH wheats (2n = 6X = 42, AABBDD) developed by L.R. Joppa were produced by crossing the durum wheat Langdon with 40 Ae. tauschii accessions. These SH lines were evaluated for seedling resistance to St. nodorum and P. tritici-repentis. Evaluations were also done for sensitivity to the host selective toxin, Ptr ToxA, a major necrosis inducing toxin of P. tritici-repentis. Evaluations of resistance were done 7 days postinoculation for tan spot and 10 days postinoculation for Stagonospora leaf blotch with a 24-h wet period following inoculation. North Dakota field isolates of St. nodorum and P. tritici-repentis (race 1) were used in the evaluation. Both diseases were evaluated on a one to five reaction scale with 1 being resistant, 2 moderately resistant, 3 moderately resistant/moderately susceptible, 4 susceptible, and 5 highly susceptible. Langdon, the durum parent in each SHW line, was moderately susceptible to tan spot and highly susceptible to Stagonospora leaf blotch. The SHs showed average tan spot disease reactions ranging from 1.33 to 4.17 with Langdon averaging 3.33. Average disease reactions for Stagonospora leaf blotch ranged from 1.67 to 4.67 with Langdon averaging 4.83. These results indicate that some Ae. tauschii accessions are contributing resistance to St. nodorum and P. tritici-repentis. These SHW lines should prove useful for incorporation into breeding programs for crop improvement.

 

Resistance to tan spot in CIMMYT elite synthetic hexaploid wheats and their durum parental lines. [p. 217]

Steven S. Xu and Timothy L. Friesen.

CIMMYT developed and characterized two sets of elite SH wheats (ELITE 95 and ELITE 2) and evaluated resistance of the lines to stripe rust, leaf rust, Fusarium head blight, Karnal bunt, Septoria tritici blotch, and spot blotch (Mujeeb-Kazi and Delgado 2001; Kujeeb-Kazi et al. 2000). In this study, 120 SHW lines from the ELITE 95 and ELITE 2, along with their durum wheat parents, were evaluated for seedling resistance to tan spot of wheat and sensitivity to the host selective toxin, Ptr ToxA. The original seed for the evaluation was obtained from Wheat Genetics Resource Center, Kansas State University, Manhattan, KS. Plant leaves were infiltrated with Ptr ToxA at the 2-leaf stage, and evaluation of sensitivity was conducted 3-4 days post infiltration. After evaluation of sensitivity, all the plants were inoculated with P. tritici-repentis (race 1) and evaluation was done 7 days post inoculation. The disease was scored on a one to five scale with 1 being resistant, 2 moderately resistant, 3 moderately resistant/moderately susceptible, 4 susceptible, and 5 highly susceptible. Evaluation results indicated that most SHW lines are the same as their parental durum lines in the sensitivity to ToxA because the sensitivity locus is located on chromosome 5B and sensitivity is dominant. However, some SH lines differed from their durum parents in reaction to Ptr ToxA. Differences could be due to the heterozygosity of the sensitivity locus, heterogeneity of the durum parents, or outcrossing of the SH lines. The original pedigree of the CIMMYT synthetics showed that the durum parents of a number of SH lines are the F1 hybrids of two durum cultivars. The SH lines have average disease reactions from 1.00 to 3.5, compared with durum parent lines of 2.67 to 5.0. Fifteen of 120 SH lines were highly resistant and may be good sources for improving tan spot resistance in wheat.

References.

  • Mujeeb-Kazi A and Delgado R. 2001. A second, elite set of synthetic hexaploid wheats based upon multiple disease resistance. Ann Wheat Newslet 47:114-116.
  • Mujeeb-Kazi A, Fuentes-Davila G, Delgado R, Rosas V, Cano S, Cortés A, Juarez L, and Sanchez J. 2000. Current status of D-genome based, synthetic, hexaploid wheats and the characterization of an elite subset. Ann Wheat Newslet 46:76-79.

 

Reciprocal transfer of chlorina genes derived from hexaploid and tetraploid chlorina mutants. [p. 217]

Daryl L. Klindworth, Noman D. Williams, and S. S. Maan.

In 1978, Sasakuma et al. (Crop Sci 18:850-853) reported on the inheritance of several male-sterile mutants of wheat. The mutants FS2, FS3, FS20, and FS24 were conditioned by a recessive gene, with three of the mutants being allelic to each other. We wanted to determine the allelic relationship of these genes to ms1, which is the only mapped recessive male-sterile mutation in wheat. We crossed the mutants to Cornerstone (ms1c) to determine allelic relationships. We found that mutants FS2, FS3 and FS24 were allelic to ms1, and, therefore, the mutations in these lines must be located in chromosome arm 4BS. A monosomic study of the FS20 mutant was conducted and the mutated gene was located to chromosome 3A. From a telosomic analysis of the FS20 gene, we found the the mutated gene in FS20 was located in chromosome arm 3AL. A linkage chi-square test indicated that the FS20 gene was not linked to the centromere of chromosome 3A. The gene symbol ms5 was assigned to the mutated gene in FS20, and gene symbols ms1d, ms1e, and ms1f were assigned to the mutations in FS2, FS3, and FS24, respectively. The ms5 gene may be useful for mapped based cloning of a male-sterility gene from wheat

 

Publications. [p. 217-218]

  • Faris JD, and Gill BS. 2002. Genomic targeting and high-resolution mapping of the domestication gene Q in wheat. Genome 45:706-718.
  • Faris JD, Friebe B, and Gill BS. 2002. Wheat genomics: exploring the polyploid model. Curr Genomics 3:577-591.
  • Friesen TL, Ali S, Kianian S, Francl LJ, and Rasmussen JB. 2003. Role of host sensitivity to Ptr ToxA in development of tan spot of wheat. Phytopathology 93:in press.
  • Huang S, Sirikhachornkit A, Su X, Faris J, Gill B, Haselkorn R, and Gornicki P. 2002. Genes encoding acetyl-CoA carboxylase and 3-phosphoglycerate kinase of the Triticum/Aegilops complex and the evolutionary history of polyploid wheat. Proc Natl Acad Sci USA 99:8133-8138.
  • Huang S, Sirikhachornkit A, Faris JD, Su XJ, Gill BS, Haselkorn R, and Gornicki P. 2002. Phylogenetic analysis of the acetyl-CoA carboxylase and 3-phosphoglycerate kinase loci in wheat and other grasses. Plant Mol Biol 48:805-820.
  • Klindworth DL, Williams ND, and Maan SS. 2002. Chromosomal location of genetic male sterility genes in four mutants of hexaploid wheat. Crop Sci 42:1447-1450.
  • Maleki L, Fellers JP, Faris JD, Bowden RL, and Gill BS. 2003. Physical and genetic mapping of wheat NBS-LRR and kinase class resistance gene analogs. Crop Sci 43:660-670.