During the past decade, the plant disease called scab or Fusarium head blight of wheat and barley has reached epidemic proportions in North America and elsewhere in the world. Scab is an economically devastating plant disease, not only because it causes significant reduction in seed yields and quality, but also because infested seeds are often contaminated with trichothecene and estrogenic mycotoxins that pose a serious threat to animal health and food safety. To test whether the primary etiological agent of scab, the fungus Fusarium graminearum, is panmictic throughout its range, allelic genealogies were constructed from six single-copy nuclear genes from strains selected to represent the global genetic diversity of this pathogen. Excluding one hybrid strain, all six genealogies recovered the same seven biogeographically structured lineages, suggesting that they represent phylogenetically distinct species among which gene flow has been very limited during their evolutionary history. Parsimony analysis of the combined data set comprising 7,120 aligned nucleotide characters resolved most relationships among the seven lineages of the F. graminearum clade and related fusaria included in the study. Phylogenetic evidence is also presented for introgressive hybridization and intragenic recombination among lineages of the F. graminearum clade in nature.

Potato starch with anomalous stable (constant with time) paste viscosity has been proposed as a natural replacement for cross-linked starch, Embut its behavior and the influencing factors are not well understood. Starch from 44 samples of potato tubers representing 34 genotypes was analyzed for phosphorus, mean granule diameter, amylose, cal-600cium, magnesium, sodium, and potassium. Except for granule diame-> ter, sodium, and potassium, each of those properties correlated C significantly with one or more of five paste characteristics determined using the Brabender Visco-amylograph. Three samples had a stable > viscosity in 1 yr of the study, but their behavior was not associated with unusual values of the other measured properties. The stable vis-200cosity is probably a heritable trait influenced by cultural and climatic factors.