Effect of Post-infection Application of Fungicides on the Apple Scab Pathogen, Venturia inaequalis (Cke.) Wint.

The Ergosterol-biosynthesis inhibiting (EBI) fungicides had a prolonged inhibitory effect on the growth and sporulation of the fungus, Venturia inaequalis thereby preventing development of typical apple scab symptoms. Atypical lesions in the form of chlorotic or reddish brown flecks had reduced viable sporulation with deleterious effect on subcuticular hyphae when fungicide was applied beyond 144 h but before 170h after inoculation. Myclobutanil (45μg a.i./ml) had the maximum inhibitory effect on sporulation and colony growth while bitertanol (187.50 μg a.i./ml) showed only a temporary inhibition of fungal growth and sporulation. Ultra-structural studies also exhibited different levels of fungitoxicity by different fungicides when applied 144 h after inoculation.     

Cellulolytic Ability of the Scab Fungus, Venturia inaequalis

Cellulase and β-D-glucosidase activity have been identified in Venturia inaequalis, the causal agent of apple scab. Most of the activity of the enzymes was associated with the mycelium after homogenization. The activities were relatively weak in vitro compared to those of other plant pathogens. With a new screening technique, β-D-glucosidase hyperproducing mutants were obtained.     

De Novo RNA Sequencing and Transcriptome Analysis of Colletotrichum gloeosporioides ES026 Reveal Genes Related to Biosynthesis of Huperzine A

Huperzine A is important in the treatment of Alzheimer’s disease. There are major challenges for the mass production of huperzine A from plants due to the limited number of huperzine-A-producing plants, as well as the low content of huperzine A in these plants. Various endophytic fungi produce huperzine A. Colletotrichum gloeosporioides ES026 was previously isolated from a huperzine-A-producing plant Huperzia serrata, and this fungus also produces huperzine A. In this study, de novo RNA sequencing of C. gloeosporioides ES026 was carried out with an Illumina HiSeq2000. A total of 4,324,299,051 bp from 50,442,617 high-quality sequence reads of ES026 were obtained. These raw data were assembled into 24,998 unigenes, 40,536,684 residues and 19,790 genes. The majority of the unique sequences were assigned to corresponding putative functions based on BLAST searches of public databases. The molecular functions, biological processes and biochemical pathways of these unique sequences were determined using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) assignments. A gene encoding copper amine oxidase (CAO) (unigene 9322) was annotated for the conversion of cadaverine to 5-aminopentanal in the biosynthesis of huperzine A. This gene was also detected in the root, stem and leaf of H. serrata. Furthermore, a close relationship was observed between expression of the CAO gene (unigene 9322) and quantity of crude huperzine A extracted from ES026. Therefore, CAO might be involved in the biosynthesis of huperzine A and it most likely plays a key role in regulating the content of huperzine A in ES026.     

Assessment of Sensitivities to Anilinopyrimidine- and Strobilurin-fungicides in Populations of the Apple Scab Fungus Venturia inaequalis

The sensitivity of Venturia inaequalis populations to the anilinopyrimidine fungicides pyrimethanil and cyprodinil was analysed by microscopic in vivo analysis of conidiophore formation. The sensitivity to the strobilurin kresoxim-methyl was analysed using an in vitro germination assay and by determination of the diseased leaf area and conidia produced in vivo. Baseline sensitivities were determined with V. inaequalis populations from control orchards that had never been treated with fungicides. Comparison of the baseline sensitivities with sensitivities of populations obtained from orchards that had received 43 anilinopyrimidine treatments over 4 years, or from an orchard with 54 kresoxim-methyl treatments over 6 years indicated that no resistance to these fungicides has developed at the sites sampled.