Resumo

CISNEROS-LOPEZ, Ma. Eugenia et al. Cold tolerant sorghum hybrids and parental lines. II: Fusarium verticillioides (Sacc.) Nirenberg effects on seed yield and its components under field conditions. Agrociencia [online]. 2007, vol.41, n.3, pp.283-294. ISSN 2521-9766.

The expansion of sorghum (Sorghum bicolor L. Moench) crop to the Central High Valleys of México, where cold tolerant experimental sorghum hybrids (CTESH) are already available, is limited by their susceptibility to stem and head blight (Fusarium verticillioides) and by the small seed size. The tolerance to this pathogen of new CTESH and some of their parental lines, to which this trait had been incorporated, was evaluated. In 2003, an experiment was established under field and irrigation conditions at Montecillo, State of México, in which 12 hybrids, 3 A-lines, 5 B-lines, 3 R-lines and the open pollinated variety VA-110 were evaluated. Three inoculation treatments at the onset of flowering, were applied per genotype: 1) injection of a pathogen suspension (5×104 conidia mL−1); 2) injection with sterile water; and 3) control without inoculum or injection. A complete randomized blocks design with three replicates, in a factorial arrangement, was used. The variables analyzed were: induced, natural and total damage caused by the pathogen on the vascular tissue, and its effect on dry matter production and distribution, and on seed yield and its components (100-seeds weight and number of seeds per panicle). The average temperature and relative humidity were favourable to the disease expression. On the average, the hybrids group produced more dry matter, higher seed yield per panicle and of its components than the groups of parental lines. The average values of heterosis and heterobeltiosis for seed yield per panicle were 35 and 22%. Some hybrids, and B and R-lines were found with less severe damage to vascular tissue and with lower yield and seed components reductions caused by the pathogen infection. The yield average and the seed size of the new parental lines were higher than those of VA-110. The results indicate that tolerance to F. verticillioides and greater seed size were traits successfully incorporated to new parental lines of cold tolerant sorghum hybrids.

Palavras-chave : Fusarium verticillioides; sorghum bicolor; phytopathology; plant breeding; cold tolerance.

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