Population structure of plant-pathogenic Fusarium species in overwintered stalk residues from Bt-transformed and non-transformed maize crops

• Published in: European journal of plant pathology Vol. 116; no. 2; pp. 129 - 143
• Main Authors: Naef, A, Défago, G
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Kluwer Academic Publishers 01.10.2006; Springer; Springer Nature B.V
• Subjects: alleles; asexual reproduction; Bacillus thuringiensis; Biological and medical sciences; Cereal crops; Corn; corn stover; Crop diseases; Crop residues; crops; field experimentation; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Fusarium graminearum; Fusarium proliferatum; Gene flow; Genetic structure; Genetics; Haplotypes; Hybrids; insecticidal proteins; loci; Phytopathology. Animal pests. Plant and forest protection; plant damage; polymerase chain reaction; Population structure; Zea mays; Europe; Germany; Bt maize residues; Monocotyledones; Bacillus thuringiensis; Insecta; Identification; Bacillaceae; Population genetics; Cereal crop; Fungi; Bacillales; Gene; Gramineae; Population genetic structure; Microsatellite DNA; Angiospermae; Bacteria; Fungi Imperfecti; Haplotype; Saprophytic Fusarium survival; Thallophyta; Zea mays; Microsatellites; Fusarium graminearum; Multiplex polymerase chain reaction; Population structure; Protein; CrylAb protein; PCR-based identification; Pathogenicity; Allele; Arthropoda; Isolate; Spermatophyta; Invertebrata
• ISSN: 0929-1873; 1573-8469
• DOI: 10.1007/s10658-006-9048-x

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. Fusarium graminearum 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 100 km distant.