Pathogenic fungi for biocontrol of Sagittaria montevidensis and selectivity for irrigated rice crop

Abstract:

The objective of this work was to identify, in the mycobiota of Sagittaria montevidensis, species of pathogenic fungi with potential to act as a bioherbicide, as well as to evaluate their selectivity for irrigated rice crop. The fungi species Fusarium oxysporum and F. semitectum of the mycobiota of S. montevidensis and six spore concentration levels (0, 1x10³, 1x10⁴, 1x10⁵, 1x10⁶, and 1x10⁷ spores mL^-1), applied on S. montevidensis plants in the stage of one sagittate leaf and on rice plants in the R4 growth stage, were assessed. The progeny of the culture was evaluated. Isolates of F. oxysporum and F. semitectum had greater impact on S. montevidensis plants; however, they were not effective in controlling the species when applied in the seedling stage with one sagittate leaf. The application of F. oxysporum and F. semitectum in the flowering stage of irrigated rice plants causes yield losses, reduction in the vigor of produced seeds, and reduction in root length and plant shoot.

Index terms:
Oryza sativa; Sagittaria montevidensis; biocontrol of weeds.