James E. Jurgenson

Genetic Mapping of Pathogenicity and Aggressiveness of Gibberella zeae (Fusarium graminearum) Toward Wheat

ABSTRACT Gibberella zeae is the major fungal pathogen of Fusarium head blight of wheat and produces several mycotoxins that are harmful to humans and domesticated animals. We identified loci associated with pathogenicity and aggressiveness on an amplified fragment length polymorphism based genetic map of G. zeae in a cross between a lineage 6 nivalenol producer from Japan and a lineage 7 deoxynivalenol producer from Kansas. Ninety-nine progeny and the parents were tested in the greenhouse for 2 years. Progeny segregated qualitatively (61:38) for pathogenicity:nonpathogenicity, respectively. The trait maps to linkage group IV, which is adjacent to loci that affect colony pigmentation, perithecium production, and trichothecene toxin amount. Among the 61 pathogenic progeny, the amount of disease induced (aggressiveness) varied quantitatively. Two reproducible quantitative trait loci (QTL) for aggressiveness were detected on linkage group I using simple interval analysis. A QTL linked to the TRI5 locus (trichodiene synthase in the trichothecene pathway gene cluster) explained 51% of the variation observed, and a second QTL that was 50 centimorgans away explained 29% of the phenotypic variation. TRI5 is tightly linked to the locus controlling trichothecene toxin type. The two QTLs, however, were likely part of the same QTL using composite interval analysis. Progeny that produced deoxynivalenol were, on average, approximately twice as aggressive as those that produced nivalenol. No transgressive segregation for aggressiveness was detected. The rather simple inheritance of both traits in this interlineage cross suggests that relatively few loci for pathogenicity or aggressiveness differ between lineage 6 and 7.

Expanded Genetic Map of Gibberella moniliformis (Fusarium verticillioides)

ABSTRACT Gibberella moniliformis (Fusarium verticillioides) is primarily a pathogen of maize, but it can also cause disease in other crop species. This pathogenicity, as well as the contamination of food- and feedstuffs with the fumonisin mycotoxins, results in economically significant losses to both farmers and food processors. The dissection of important biological characters in this fungus has been hampered by the lack of a uniformly dense genetic map. The existing restriction fragment length polymorphism-based map contains significant gaps, making it difficult to routinely locate biologically important genes, such as those involved in pathogenicity or mycotoxin production, with precision. We utilized amplified fragment length polymorphisms (AFLPs) to saturate the existing genetic map and added 486 AFLP markers to the ∼150 markers on the existing map. The resulting map has an average marker interval of 3.9 map units and averages ∼21 kb/map unit. The additional markers expanded the map from 1,452 to 2,188 map units distributed across 12 chromosomes. The maximum distance between adjacent markers is 29 map units. We identified AFLP markers less than 1 map unit from the mating type (MAT) locus and 2.5 map units from the spore killer (SK) locus; eight AFLP markers map within 8.5 units of the FUM1 (fumonisin biosynthetic) locus. The increased saturation of this map will facilitate further development of G. moniliformis as a model system for the genetic and population genetic studies of related, but less genetically tractable, plant pathogenic fungi.

Isozyme and amplified fragment length polymorphisms fromCephalosporium maydis in Egypt

Isoenzyme and amplified fragment length polymorphisms (AFLP) variation within a set of 48 isolates ofCephalosporium maydis was characterized. These isolates included ten cultures that have served as standards in the Egyptian maize resistance breeding program and 38 additional strains collected from 11 governates in Egypt during the 1997 growing season. Eight isozymes also were tested, but only five (acid phosphatase, fumerase, gtucose 4-phosphate isomerase, isocitrate dehydrogenase, and malate dehydrogenase) produced identifiable bands and all five of these enzymes were monomorphic. Sixty-eight AFLP primer-pair combinations were used and 865 bands were scored, of which 288 (33%) were polymorphic and could be used to discriminate four distinct subgroups, or lineages. Representatives from only two of the four lineages are included in the set of ten strains that has been used to challenge new lines in the Egyptian maize breeding program. From among these 68 primer-pair combinations, we identified a set of four AFLP primer-pairs that were strongly correlated (Pearson‘sr > 0.85) with the full data set that can be used as markers to determine the distribution of these lineages and to identify new lineages in field populations.

Isolate specific detection of mycorrhizal fungi using genome specific primer pairs

Random amplification of polymorphic DNA analysis was used to generate DNA fragments that are unique to isolates of two arbuscular mycor- rhizal fungi, Glomus mosseae and Gigaspora margarita. Sequence analysis of these fragments allowed gener- ation of primer pairs, and subsequent specific iden- tification of these genomes even in the presence of competing genomic DNAs. This approach can be used to specifically detect the presence of these fungi in mixtures of spores or infected roots.

Alignment of Genetic and Physical Maps of Gibberella zeae

ABSTRACT We previously published a genetic map of Gibberella zeae (Fusarium graminearum sensu lato) based on a cross between Kansas strain Z-3639 (lineage 7) and Japanese strain R-5470 (lineage 6). In this study, that genetic map was aligned with the third assembly of the genomic sequence of G. zeae strain PH-1 (lineage 7) using seven structural genes and 108 sequenced amplified fragment length polymorphism markers. Several linkage groups were combined based on the alignments, the nine original linkage groups were reduced to six groups, and the total size of the genetic map was reduced from 1,286 to 1,140 centimorgans. Nine supercontigs, comprising 99.2% of the genomic sequence assembly, were anchored to the genetic map. Eight markers (four markers from each parent) were not found in the genome assembly, and four of these markers were closely linked, suggesting that >150 kb of DNA sequence is missing from the PH-1 genome assembly. The alignments of the linkage groups and supercontigs yielded four independent sets, which is consistent with the four chromosomes reported for this fungus. Two proposed heterozygous inversions were confirmed by the alignments; otherwise, the colinearity of the genetic and physical maps was high. Two of four regions with segregation distortion were explained by the two selectable markers employed in making the cross. The average recombination rates for each chromosome were similar to those previously reported for G. zeae. Despite an inferred history of genetic isolation of lineage 6 and lineage 7, the chromosomes of these lineages remain homologous and are capable of recombination along their entire lengths, even within the inversions. This genetic map can now be used in conjunction with the physical sequence to study phenotypes (e.g., fertility and fitness) and genetic features (e.g., centromeres and recombination frequency) that do not have a known molecular signature in the genome.

Derivation of a physical map of chloroplast DNA from Nicotiana tabacum by two-dimensional gel and computer-aided restriction analysis

A combined approach was used to derive a detailed physical map of Nicotiana tabacum chloroplast DNA for the restriction enzymes SalI, SmaI, KpnI, and BamHI. Complete maps for the restriction enzymes SalI, SmaI, and KpnI were derived by using two-dimensional agarose gel analysis of fragments obtained by reciprocal double digestion of chloroplast DNA. We have characterized a complete cloned library of N. tabacum chloroplast DNA which contains overlapping restriction fragments resulting from partial digestion by BamHI. With these clones and existing data, we used a novel computer-aided analysis to derive a detailed map for the enzyme BamHI. A comparison and compilation of all published N. tabacum chloroplast DNA restriction maps is presented. Differences between ours and a previously published SmaI and BamHI restriction map are discussed.

Synthesis, Characterization, and Antimicrobial Studies of Some 2-Substituted Benzaldehyde-2-Furanthiocarboxyhydrazones and their Ni(II), Cu(II), AND Zn(II) Complexes

Abstract Several 2-substituted benzaldehyde-2-furanthiocarboxyhydrazones and their nickel(II), copper(II), and zinc(II) complexes have been synthesized. These compounds were characterized by their elemental analyses and infrared spectra. Electrical conductivities and magnetic susceptibilities of the metal complexes were also measured. All compounds were tested against inhibition of growth of f. coli and B. subtilis. Minimum inhibitory concentrations of the active compounds are reported. Results of screening against HIV are also reported.

Taxonomy of a mixed Cylindrocystis assemblage from Vermont soil. II: Isozyme variations

Summary Isolates of Cylindrocystis obtained from Vermont and Pennsylvania have been analysed. Isozymes of the enzymes Malate Dehydrogenase, Isocitrate Dehydrogenase, Shikimate Dehydrogenase, and Malic enzyme have been compared. Analysis of each enzyme revealed considerable variability among the strains examined. Isozyme patterns were invariant, however, for all enzymes within groups delineated by cell morphology and location of isolation. This variant yet invariant isozyme distribution is considered in terms of species delineation in this taxonomically difficult group of algae.