Antagonistic Activity of Fungal Strains against Crown Rot.

The crown rot of wheat is a destructive soil-borne pathogen that severely reduces the yield and quality of wheat. This study aimed to screen and identify the antagonistic strains against (), which is the dominant pathogen associated with the crown rot of wheat in China, and evaluate their biosynthetic potential. The antagonistic strains were screened via a dual-culture antagonism assay, and then identified by combining the morphological characteristics and internal transcribed spacer gene sequencing. The polyketide synthases (PKS-I and PKS-II) and non-ribosomal peptide synthetase (NRPS) genes in the antagonistic strains were detected via specific amplification of chromosomal DNA. Eleven out of 157 fungal strains, including six strains with matrix competition and five strains with antibiosis, were obtained. The eleven antagonistic strains belonged to the following four genera: , , and . The inhibition rate of six strains with matrix competition was greater than 50%, with S2-22 demonstrating the highest at 80.3%. The width of the inhibition zone of R-17 among the five strains with antibiosis was the widest at 11 mm. Among the eleven antagonistic strains, three strains of and the strain only contained the PKS-II gene, the strain contained PKS-I and PKS-II genes, three strains of contained PKS-II and NRPS genes, while three strains of did not contain any genes. These results demonstrated potential strains for the biocontrol of the crown rot of wheat. In particular, R-17 can be investigated further as a promising agent, and the active substances secreted by antagonistic strains may be synthesized by other pathways.