Antigenic diversity in the major merozoite antigens ofTheileria parasites

Tropical Animal Health and Production -     

Use of computed tomography to evaluate pathologic changes in the lungs of calves with experimentally induced respiratory tract disease

OBJECTIVE: To optimize methods for the use of computed tomography (CT) to assess pathologic changes in the lungs of calves and to determine the effect of treatment on lung consolidation. ANIMALS: 10 male Holstein calves. PROCEDURES: Calves were anesthetized to facilitate CT imaging of the thorax. After initial images were obtained, pneumonia was induced in the calves by inoculation through a bronchoscope. Two calves were used in a preliminary study to refine the inoculation dose and optimize CT images. Four calves were administered florfenicol and 4 calves were untreated control animals. Serial images were obtained 24, 48, and 72 hours after inoculation. After final images were obtained, calves were euthanized, and lung consolidation was estimated by use of lung surface area scoring and water displacement. These estimates were compared with estimated lung consolidation obtained by use of CT. RESULTS: Calves had rapid disease progression. Percentage of lung consolidation was not significantly different between treatment groups for any of the estimation methods. Results of an ANOVA of the 3 assessment methods indicated significant differences among methods. Estimates of the percentage of lung consolidation obtained by use of surface area scoring and CT correlated well, whereas water displacement estimates correlated poorly with other methods of consolidation estimation. CONCLUSIONS AND CLINICAL RELEVANCE: Because of the correlation with other methods for estimation of lung consolidation, CT has the potential to be used to monitor disease progression in calves with experimentally induced respiratory tract disease.     

Analysis of durable resistance to stem rust in barley

Summary Since the mid-1940's, barley cultivars grown in the northern Great Plains of the USA and Canada have been resistant to stem rust caused byPuccinia graminis f. sp.tritici. This durable resistance is largely conferred by a single gene,Rpg1, derived from a single plant selection of the cultivar Wisconsin 37 and an unimproved Swiss cultivar. At the seedling stage, barley genotypes withRpg1 generally exhibit low mesothetic reactions at 16–20° C and slightly higher mesothetic reactions at 24–28° C to many stem rust pathotypes. This resistance is manifested by a low level of rust infection and mostly incompatible type uredia on adult plants.Rpg1 reacts in a pathotype-specific manner since some genotypes ofP. g. f. sp.tritici are virulent on cultivars carrying this gene in the field. Several factors may have contributed to the longevity of stem rust resistance in barley, a) since barley is planted early and matures early, it can sometimes escape damage from stem rust inoculum carried from the south; b) one or more minor genes may augment the level of resistance already provided byRpg1; c) the cultivation of resistant wheat cultivars and eradication of barberry have reduced the effective population size and number of potential new pathotypes ofP. g. f. sp.tritici, respectively; and d) virulent pathotypes ofP. g. f. sp.tritici andP. g. f. sp.secalis have not become established. This situation changed in 1989 when a virulent pathotype (Pgt-QCC) ofP. g. f. sp.tritici became widely distributed over the Great Plains. However,Rpg1 may still confer some degree of resistance to pathotype QCC because stem rust severities have been low to moderate and yield losses light on barley cultivars carrying the gene during the last four seasons (1989–1992). Several sources of incomplete resistance to pathotype QCC have been identified in barley. To facilitate the transfer of resistance genes from these sources into advanced breeding lines, molecular marker assisted selection is being employed.     

Mutation genetics of salt tolerance in barley: An assessment of Golden Promise and other semi-dwarf mutants

A review of research at the Scottish Crop Research Institute (SCRI) on the effects of semi-dwarfing genes on salt tolerance in barley is given. Work began in1993 with the fortuitous and unexpected result that the cultivar ‘Golden Promise’ showed considerable tolerance to salt. Golden Promise is a gamma-ray induced semi-dwarf mutant of the cultivar ‘Maythorpe’. The parent and mutant cultivars are presumed to be isogenic, but show significant differences in their responses to salt stress. The positive and pleiotropic effects of the mutant gene, commonly known as GPert were found to be effective in a number of genetic backgrounds. Earlier, in 1991 Frackowiak showed that the GPert mutation was allelic to the ari-e mutants in barley. The ari-emutants were salt tested and found to show the same positive responses to salt stress as Golden Promise. This supported the allelism tests, and consequently the GPert symbol was changed to ari-e.GP. The semi-dwarf mutant sdw1 (also known as denso) and the erectoides semi-dwarf mutant,ert-k ³² were also tested for their effects on tolerance to salt, but did not show any positive effects. Salt tolerance was therefore not a general phenomenon of semi-dwarf stature but specific to mutations at the Ari-e locus in these lines. Genetic markers (RAPDs, AFLPs and SSRs) have been used for fingerprinting, genetic mapping, and QTL analysis. The markers have helped 1) confirm the isogenic relationship between Maythorpe and Golden Promise, 2)clarify the confusion over the pedigree of Golden Promise, and 3) genetically map the ari-e.GPlocus and examine its pleiotropic effects. This revised version was published online in August 2006 with corrections to the Cover Date.     

The effect of introgressions of wheat D-genome chromosomes into 'Presto' triticale

Hexaploid triticale (X Triticosecale Wittmack) (2n= 6x= 42, AABBRR) and wheat (Triticum aestivum L.) (2n= 6x= 42, AABBDD) differ in their R and D-genomes. This produces differences in both agronomic and end-use quality characteristics. Our objective was to determine how introgressions of individual chromosomes from the D-genome of wheat affect these characteristics of a winter triticale 'Presto'. We studied the effects of 18 D-genome chromosome substitution lines, 15 sib-lines as controls, and five check cultivars at Lincoln, NE in 1996, using a randomized complete block design with two replications. The experiment was repeated at Lincoln and Mead, NE in 1997 and 1998 with 15 substitution lines that survived the first winter in Lincoln, along with their 12 control sibs and five check cultivars. Few D-genome chromosomes had positive effects. Chromosomes 2D, 4D, and 6D significantly reduced plant height when substituted for 2R, 4B, and 6R, respectively. No grain yield increases were associated with any of the D-genome chromosomes tested, but three substitutions decreased the grain yield. Depending on the allele of the hardness gene present, chromosome 5D increased or decreased kernel hardness when substituted for 5R or 5A, respectively. Introgressions of chromosomes 1D and 6D improved end-use quality characteristics of Presto. These results suggest that apart from beneficial effects of individual loci located on the D-genome chromosomes, no major benefit can be expected from D-genome chromosome substitutions.