Resumo

CISNEROS-LOPEZ, Ma. Eugenia et al. Cold tolerant sorghum hybrids and parental lines. III: quality of seeds harvested from plants infected with Fusarium verticillioides (Sacc.) Nirenberg. Agrociencia [online]. 2007, vol.41, n.4, pp.405-415. ISSN 2521-9766.

One factor that limits commercial expansion of sorghum (Sorghum bicolor L. Moench) in the Central High Valleys of México is its susceptibility to stem and head blight, a disease caused by Fusarium verticillioides (F. moniliforme). Because of the lack of information on quality of seed harvested from plants infected with this fungus, in 2003 an experiment was set up in Montecillo, State of México, under irrigated field conditions. Twenty-four cold tolerant genotypes (hybrids, parental lines, and the variety VA-110) were assessed with three inoculation treatments: 1) injection of the pathogen in suspension (5×104 conidia mL-1); 2) injection with sterile water; 3) absolute control, without inoculum or injection, in a complete randomized blocks design with three replications. Harvested seed was assessed based on physiological quality (germination of normal and abnormal seedlings, dead seeds, vigor, and seedling dry matter production), physical quality (100-seed weight, volumetric weight, and number of seeds per gram), and sanitary quality (frequency of diseased seedlings). Also, tests were conducted to confirm the presence of F. verticillioides as the source of inoculum and transmission by seed. The seed harvested from the group of hybrids exhibited better physical quality characteristics than the groups of parents and VA-110, but these advantages were not reflected in better characteristics in terms of physiological or sanitary quality variables. The characteristics of seed quality of the group of hybrids were more similar to the group of male parents than to the group of female parents. As an average of the 24 genotypes, the seed harvested from plants inoculated artificially with F. verticillioides exhibited lower germination rate, vigor and 100-seed weight than those from the control plants, but there was no effect in seedling dry matter production or in percentage of diseased seedling. Artificial inoculation and injection with water had similar effects on most of the characteristics related to harvested seed quality. In the Central High Valleys of México, F. verticillioides and F. oxysporum are the causal agents of this disease in sorghum.

Palavras-chave : Fusarium oxysporum; Fusarium verticillioides; Sorghum bicolor; seed quality; phytopathology; cold tolerance.

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