Identification and Characterization of Fusarium nirenbergiae Associated with Saffron Corm Rot Disease

Saffron (Crocus sativus L.) is the most expensive spice plant and is distributed widely around the world. However, its production is limited by corm rot, a disastrous disease, attributed to Fusarium oxysporum in many regions of the world. In 2020, extensive surveys were carried out in Zhejiang, Shanghai, Anhui, and Guizhou provinces as saffron growing areas of China. Fourteen single-spore isolates were obtained from rotted corms and identified as F. nirenbergiae according to morphological appearance and multilocus phylogenetic analysis with translation elongation factor 1-alpha (tef1), DNA-directed RNA polymerase II largest subunit (rpb2), and beta-tubulin (tub2). Results of the pathogenicity assay supported the conclusion that F. nirenbergiae is the pathogen responsible for corm rot. In this study, we obtained the whole genome sequence of two highly virulent F. nirenbergiae strains via the Illumina HiSeq platform. Genome sequence assemblies of approximately 52.7 and 52.2 Mb were generated for isolates WY5 and SH1, respectively. To the best of our knowledge, this is the first report of F. nirenbergiae causing C. sativus corm rot in China and indeed worldwide. Results from this research contribute to our understanding of genetic diversity, genomic information, and host determination, which will enable researchers to design appropriate management measures for this hazardous disease.