Invasion and Colonization of Pathogenic Fusarium oxysporum R1 in Crocus sativus L. during Corm Rot Disease Progression.

The corm rot of saffron caused by (Fox) has been reported to be the most destructive fungal disease of the herb globally. The pathogen, R1 (Fox R1) isolated by our group from Kashmir, India, was found to be different from f.sp. commonly reported corm rot agent of saffron. In the present study, Fox R1 was further characterized using housekeeping genes and pathogenicity tests, as R1 f.sp. race 4. Though Fox R1 invaded the saffron plant through both corm and roots, the corm was found to be the preferred site of infection. In addition, the route of pathogen movement wastracked by monitoring visual symptoms, semi-quantitative PCR, quantitative-PCR (q-PCR), real-time imaging of -tagged R1, and Fox R1 load quantification. This study is the first study of its kind on the bidirectional pathogenesis from corm to roots and vice-versa, as the literature only reports unidirectional upward movement from roots to other parts of the plant. In addition, the colonization pattern of Fox R1 in saffron corms and roots was studied. The present study involved a systematic elucidation of the mode and mechanism of pathogenesis in the saffron strain R1 pathosystem.