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Abstract:The aims of this study were to clarify the reproductive biology of the Ustilago filiformis Schrank, as causal agent of the stripe smut of Glyceria multiflora, determine the infection process of the pathogen and analyze the histological changes associated hostGlyceria any fungus attack. Moreover, the life cycle of the fungus was elucidated for the first time. Both teliospores and basidiospores were found to be equally efficient in producing the infection in Glyceria plants after the plants had been inoculated. These results constitute an important contribution for the understanding of the epidemiology of the disease.

In the present study the aspects of discolouration that could influence both the production and consumption of amaranth were analyzed with the objectives to identify the presence of Alternaria alternata on seeds, to analyze possible changes in the anatomy of seed tissues and to detect the presence of fungal secondary metabolites. Component plating, histopathological and mycological analyses on discoloured seeds allowed i) location of propagules of A. alternata in all seminal components; ii) observation of hypertrophies in perisperm and embryo and iii) determination of several fungal secondary metabolites, mainly high concentrations of tenuazonic acid. To our knowledge, the information presented in this paper, related to physiological, histopathological changes and fungal secondary metabolites on discoloured seeds of (Amaranthus mantegazzianus syn. A. caudatus subsp. mantegazzianus (Pass) Hanelt affected by A. alternata, is the first worldwide record.

Th e eff ect of loose kernel smut fungus Sporisorium cruentum on Sorghum halepense (Johnson grass) was investigated in vitro and in greenhouse experiments. Smut infection induced a decrease in the dry matter of rhizomes and aerial vegetative parts of the plants evaluated. Moreover, the diseased plants showed a lower height than controls. Th e infection resulted in multiple smutted buds that caused small panicles infected with the fungus. In addition, changes were observed in the structural morphology of the host. Leaf tissue sections showed hyphae degrading chloroplasts and vascular bundles colonized by the fungus. Subsequently, cells collapsed and widespread necrosis was observed as a symptom of the disease. Th e pathogen did not colonize the gynoecium of Sorghum plants until the tassel was fully developed. Th e sporulation process of the fungus led to a total disintegration of anthers and tissues. When panicles were inspected before emergence, fungal hyphae were observed on fl oral primord. Histological sections of panicles showed fungal hyphae located in the parenchyma tissue and the nodal area. Infection occurred in the fl oral primordium before the tassel had fully developed and emerged from the fl ag leaf. Grains were replaced by sori surrounded by a thin membrane that usually was broken before or aft er the emergence of the panicle. Th e results, together with the signifi cant decrease of the dry matter of rhizomes and seeds of S. halepense, suggest that S. cruentum could be considered as a potential biocontrol agent in the integrated management of this weed.