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Bt-transformed maize contains genes from Bacillus thuringiensis encoding for insecticidal crystal proteins. Less insect damage on Bt maize stalks can cause a reduced infection by Fusarium species through plant injuries. This could affect the presence of plant-pathogenic Fusarium species on maize residues which serve as an inoculum source for subsequent crops. We collected overwintered maize stalks of four different Bt maize hybrids and their corresponding non-Bt lines in two consecutive years in a field trial in Germany. Fusarium spp. were isolated from 67% of 648 collected maize stalks. Identification with new multiplex PCR assays showed that F. graminearum, F. avenaceum, and F. proliferatum were the most abundant Fusarium species, isolated from 42%, 26%, and 15% of the stalks, respectively. Species abundances varied between varieties and collection years. No consistent difference was found between Bt and non-Bt stalks. Fusariumgraminearum isolates were subject to a population genetic structure analysis with eight newly developed microsatellites. Significant association of loci and overrepresentation of repeated multilocus haplotypes indicated a substantial asexual component of reproduction, supporting selection of haplotypes. The data suggested selection of particular F. graminearum haplotypes by collection years but not by maize Bt transformation. Haplotypic changes between years caused no divergence in the distribution of alleles, suggesting that gene flow beyond the field scale prevented substructuring. We present evidence for gene flow between our saprophytic F.graminearum population on maize residues and a wheat-pathogenic population from a field 100km distant

Within the framework of the European COST Action 816, afive-year collaboration between scientists from five Europeancountries has made an important contribution to biologicalcontrol of field and hedge bindweeds (Convolvulus arvensis andCalystegia sepium, respectively). A fungus Stagonosporaconvolvuli strain LA39, able to infect both field and hedgebindweed, was found in the UK and its biocontrol efficacyimproved by optimising mass production, formulation and storagetechniques. This fungus controlled bindweeds in both a cemeteryand in maize crops. Its use fits best in an integrated pestmanagement system where a green cover controls most of the weedsexcept the bindweeds. DNA marker analyses indicate that thefungus reproduces sexually, which could be used to furtherimprove this mycoherbicide. In addition, the insect Melanagromyzaalbocilia, which itself exhibits biocontrol potential againstbindweeds, may be used in combination with LA39 to improve theability of the fungus to penetrate the stem of bindweeds.Overall, the results suggest that S. convolvuli LA39 haspromising potential as a bioherbicide for control of field andhedge bindweed

A naphthazarin-producing (fusarubin, novarubin, javanicin, norjavanicin), highly pathogenic strain of Nectria haematococca (sexual state of Fusarium solani var. martii) was crossed with a non-naphthazarin-producing, slightly pathogenic mutant strain. This cross and several backcrosses were studied by unordered tetrad analysis. In all tetrads a 4: 4 ratio of naphthazarin-producing ascospore strains to non-naphthazarin-producing ones resulted. By two-factor analysis for this character and the markers determining mating type, sexual type, colonial growth, and perithecial colour respectively, parental-ditype, non-parental-ditype, and tetratype tetrads resulted. This indicates that the loss of the capacity to produce naphthazarins is due to a mutation at a single locus, which probably blocks the biosynthesis of a polyketide precursor. When the same tetrads were tested for pathogenicity, the strains could not be classified into a group with high pathogenicity and one with low pathogenicity, as they showed intermediate degrees of pathogenicity. It is therefore concluded that the degree of pathogenicity is polygenically inherited. The difference in the inheritance of the capacity to produce naphthazarins and of pathogenicity, as well as the appearance of highly pathogenic though non-naphthazarin-producing segregants, indicates that the capacity to produce novarubin, fusarubin, javanicin, and norjavanicin is not a major factor in the determination of a high degree of pathogenicity

Within the framework of the European COST Action 816, afive-year collaboration between scientists from five Europeancountries has made an important contribution to biologicalcontrol of field and hedge bindweeds (Convolvulus arvensis and Calystegia sepium, respectively). A fungus Stagonosporaconvolvuli strain LA39, able to infect both field and hedgebindweed, was found in the UK and its biocontrol efficacyimproved by optimising mass production, formulation and storagetechniques. This fungus controlled bindweeds in both a cemeteryand in maize crops. Its use fits best in an integrated pestmanagement system where a green cover controls most of the weedsexcept the bindweeds. DNA marker analyses indicate that thefungus reproduces sexually, which could be used to furtherimprove this mycoherbicide. In addition, the insect Melanagromyzaalbocilia, which itself exhibits biocontrol potential againstbindweeds, may be used in combination with LA39 to improve theability of the fungus to penetrate the stem of bindweeds.Overall, the results suggest that S. convolvuli LA39 haspromising potential as a bioherbicide for control of field andhedge bindweed.

The abundance and population structure of pseudomonads in soils collected from long-(1006 years) and short-(54 years) term grapevine monocultures in Switzerland were examined across five soil horizons within the 1.20e1.35 m range. Soil samples were baited with grapevine, and rhizosphere pseudomonads containing the biocontrol genes phlD (2,4-diacetylphloroglucinol synthesis) and/or hcnAB (hydrogen cyanide synthesis) were analyzed by MPN-PCR. The numbers of total, phlDþ and hcnABþ pseudomonads decreased with depth by 1.5e2 log (short-term monoculture) and 3e3.5 log (long-term monoculture). In addition, the percentages of phlDþ (except in short-term monoculture) and hcnABþ pseudomonads were also lower in deeper horizons. RFLP-profiling of phlDþ and hcnABþ pseudomonads revealed three phlD and twelve hcnAB alleles overall, but the number of alleles for both decreased in relation to depth. The only phlD allele found in deeper horizons was also found in topsoil, whereas one hcnAB allele (k) found in deeper horizons in long-term monoculture was absent in the topsoil. This suggests that certain Pseudomonas ecotypes are adapted to specific depths. Four hcnAB alleles enabled discrimination between monocultures. We conclude that soil depth is a factor selecting phlD and hcnAB genotypes, and that the allelic diversity of the two biocontrol genes decreases with depth.