Greenhouse Studies Reveal Increased Aggressiveness of Emergent Canadian Fusarium graminearum Chemotypes in Wheat.

The role of Fusarium graminearum trichothecene-chemotypes in disease outcomes was evaluated by point inoculation in a series of wheat lines with different levels of resistance to Fusarium head blight (FHB). Four inocula, each consisting of a composite of four strains with either 15-acetyldeoxynivalenol (ADON) chemotypes from "traditional" or emergent populations, a 3-ADON chemotype, or a nivalenol (NIV) chemotype, were compared. The evaluated wheat included Canadian lines with different levels of FHB resistance/susceptibility and double haploid lines developed from crosses of these lines. Highly resistant lines were resistant to infection by all of the F. graminearum chemotypes evaluated. In the moderately susceptible/resistant wheat lines, the 3-ADON producers and the emergent 15-ADON population were, in some instances, more aggressive and resulted in higher Fusarium damaged kernel scores and levels of trichothecene accumulation. The data presented in this study demonstrate the importance of growing highly resistant wheat cultivars in the current climate of an evolving F. graminearum population, and suggest that moderate levels of FHB resistance may not be sufficient to minimize trichothecene contamination of grain from F. graminearum-infected wheat.

Development and assessment of DArT markers in triticale.

Triticale (X Triticosecale Wittm.) is a hybrid derived by crossing wheat (Triticum sp.) and rye (Secale sp.). Till date, only a limited number of simple sequence repeat (SSRs) markers have been used in triticale molecular analyses and there is a need to identify dedicated high-throughput molecular markers to better exploit this crop. The objective of this study was to develop and evaluate diversity arrays technology (DArT) markers in triticale. DArT marker technology offers a high level of multiplexing. Development of new markers from triticale accessions was combined with mining the large collection of previously developed markers in rye and wheat. Three genotyping arrays were used to analyze a collection of 144 triticale accessions. The polymorphism level ranged from 8.6 to 23.8% for wheat and rye DArT markers, respectively. Among the polymorphic markers, rye markers were the most abundant (3,109) followed by wheat (2,214) and triticale (719). The mean polymorphism information content values were 0.34 for rye DArT markers and 0.37 for those from triticale and wheat. High correlation was observed between similarity matrices derived from rye, triticale, wheat and combined marker sets, as well as for the cophenetic values matrices. Cluster analysis revealed genetic relationships among the accessions consistent with the agronomic and pedigree information available. The newly developed triticale DArT markers as well as those originated from rye and wheat provide high quality markers that can be used for diversity analyses and might be exploited in a range of molecular breeding and genomics applications in triticale.

Use of hen lysozyme for protection against bacterial contamination ofin vitro embryo cultures.

Curative treatments with antibiotics and hen egg white lysozyme (HEWL) were used to salvage embryo cultures contaminated withBaccillus subtilis. The use of HEWL gave good control ofBaccillus subtilis, but no control ofErwinia. HEWL was better than antibiotics, being much less phytotoxic. The antibiotics piperacillin, ampicillin and imipenem were also found to be ineffective againstErwinia. HEWL, at a final concentration of 1 mg per mL, was used as a preventive and curative agent for routine use in embryo culture ofTriticum aestivum and other Triticeae, as it cured from 30% to 50% of bacterial contamination problems over a one year period. Standardin vitro culture precautions remained essential, as certain bacteria were not controlled by HEWL.