Reduction of olive pollen germination when exposed to herbicides in vitro

The main objective of this research was to investigate the possibility of pollen germination reduction in ‘Arbequina’ and ‘Koroneiki’ olive cultivars bdue to contamination by glyphosate (N-(Phosphonomethyl) glycine) and 2,4-D (2,4-dichlorophenoxyacetic acid).. Underdoses of glyphosate (0.19 and 1.92 g L-1) and 2,4-D (0.16 and 1.61 g L-1) were added to the culture medium for pollen grain germination. A control treatment, without herbicide addition, was also included in the trial. The experimental design was completely randomized, with three replications. Each plate was a replication and each one consisted of 100 pollen grains were counted after incubation. Pollen grains were considered germinated when their tube length was at least twice of their diameter. The results inferred that there were reductions in germination of 44% and 38.2% for Arbequina and Koroneiki, respectively, when they were subjected to a underdose of 0.19 g L-1 of glyphosate. Total inviability for both cultivars, that is 100% non-germinated pollen, occurred at the underdose of 1.92 g L-1 of glyphosate and for both underdoses of 2,4-D (0.16 and 1.61 g L-1). The results suggest that there was a high sensitivity of olive pollen to extremely low doses of glyphosate and 2,4-D in vitro. It represents a concern about olive groves`productivity due to the recurrence of herbicide drift during the olive flowering period.