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A study was made of the effects of garlic on the development of mycelium in the following phytopathogenic fungi: Fusarium solani (Mart.) Sacc., Rhizoctonia solani Kühn, Pythium ultimum Trow var. ultimum, and Colletotrichum lindemuthianum (Sacc. and Magnus) Briosi and Cav. A suspension of micronized garlic powder, which has volatile organic compounds mainly consisting of linear chain aldehydes, allyl sulfides and disulfides, was used for the trials. Mycelial development of the fungi was strongly inhibited at the maximum concentration of the aqueous extract tested (100 ml/liter); however only the growth of P. ultimum var. ultimum was entirely blocked. Transmission and scanning electron microscopy revealed cytomorphological alterations of the hyphae treated with garlic. R. solani and C. lindemuthianum hyphae appeared especially collapsed, while those of F. solani were less damaged, although thinner than the control hyphae. A general increase in vacuolization was also observed, with consequent reduction in the cytoplasm of the treated fungal cells. R. solani also revealed a thickening of the cell wall, whereas C. lindemuthianum revealed a singular accumulation of osmiophil bodies immediately under the cell membrane.

Fusarium oxysporum Schlecht. Fr. F. sp.gladioli (FOG) is the most important gladiolus pathogen. One of the most environmentally friendly methods to control its spread is to use cultivars that are minimally sensitive to the pathogen. Infected corm tissues in more resistant varieties have been shown to produce suberin layers that inhibit fungal iphae growth. RAPD analysis of genomes from 9 selected gladiolus cvs, chosen to be the most resistant and sensitive to FOG, were performed to verify DNA polymorphism levels. Total nucleic acid extraction was carried out with a chloroform-phenol method from tissues of plants in 3 growth stages. RAPD experiments were performed using 14 primers with varyingTaq polymerases and primer concentrations. Five of the primers tested gave no polymorphic profiles. Five primers produced polymorphic bands, allowing us to obtain RAPD profiles typical for one or more of the more resistant cvs. All the tested growth stages provided repeatable results, indicating the reliability of detected polymorphisms. Cloning the more interesting polymorphic DNA fragments in the future will verify the presence of specific genes related to FOG resistance mechanisms in gladiolus.