Morphological and molecular characterization of pathogenic isolates of Fusarium spp. obtained from gladiolus corms and their sensitivity to Jatropha curcas L. oil

The State of Morelos is the third biggest gladiolus producer in Mexico. However, this ornamental is affected by the disease named corm rot or fusarium yellows, characterized by leaf yellowing, epinasty and wilting, and caused by fungi of the genus Fusarium. The first objective was to corroborate the pathogenicity of the 45 isolates obtained. The second objective was to identify and characterize morphologically and molecularly by polymerase chain reaction-internal transcribed spacer (PCR-ITS), the highly pathogenic isolates and comparatively analyze the fungal species involved with the reference strain Fusarium oxysporum f. sp. gladioli (Fog). The third objective was to quantify the phorbol esters in Jatropha curcas oil and evaluate their antifungal potential on mycelial growth and conidial germination of different Fusarium species. Eleven isolates were highly significant pathogenic (P < 0.001). Three fungal species were identified in basal stems and damaged corms taken from field plants, namely F. oxysporum, Fusarium solani and Fusarium proliferatum. Molecular analyzes corroborated the species identified and their sequences were deposited in the National Center for Biotechnology Information (NCBI) gene bank. The percentage of oil obtained was 61.5 %; the phorbol ester content in the oil was 1.52 mg g-1 of 12,13-phorbol myristate. All species identified and the reference strain was sensitive to the 5 mg mL-1 oil concentration.   Key words: Corm rot, Fusarium, molecular analysis, phorbol esters, Fusarium development.