Isolation and identification of pathogenic fungi of stem rot in Crocus sativus

Key words: 
• Crocus sativus /
• stem rot /
• corm /
• molecular identification /
• fungal disease /
• Aspergillus niger

Abstract:   Objective  This study, with an investigation into the identification and isolation of the rot disease pathogen of Crocus sativus, the main disease of which is fungal disease, is intended to provide scientific basis for the prevention and control of saffron stem rot and the development of special fungicides.   Method  First, the pathogenic fungi were isolated from infected corms by tissue separation method using ‘Saffron No. 1’ as the test material. Then an analysis was made of the sequences of conserved internal transcribed spacer (ITS) and RNA polymerase Ⅱ subfamily (RPB2) by PCR amplification, sequencing and phylogenetic tree construction. At last, pathogenic bacteria were isolated from infected corms and grafted back to plants to verify the pathogenic characteristics of fungi under the planting mode of saffron.   Result  The morphological characteristics of the corm-pathogenic fungi isolated were highly similar to those of Aspergillus niger. The conserved sequences of ITS and RPB2 of the candidate pathogenic fungi had 99.6% homology to the same DNA sequence of A. niger from other plants with the same evolutionary branch. In the soil planting mode, inoculation with A. niger solution significantly increased the incidence of corm (P＜0.01).   Conclusion  A. niger is one of the fungal diseases that cause the rot of saffron bulbs. [Ch, 7 fig. 32 ref.]