Rice Seed Dormancy.

In Costa Rica, transgenic crops are grown just as winter nurseries; however, there is not a ban on growing transgenic crops intended for human consumption. Rice (Oryza sativa) is a staple food in Costa Rica, and transgenic herbicide-resistant rice could be an alternative for growers to improve weed control and to reduce labor costs. The information that would help decision makers to accept or reject permits to grow transgenic rice includes gene flow, seed dispersal, and seed survival after harvest. Therefore the objective of this experiment was to determine the effect of seed burial on seed mortality, germination, and dormancy of two rice cultivars under field conditions. Seed of the rice cultivars Palmar18 and CR5272 were buried at 0, 15, and 30 cm in a commercial rice field under irrigation in Guanacaste Province. The experiment was established twice in the same location and samples were collected once a month for 12 months. Variables evaluated were mortality, germination, and viability with the tetrazolium test. The results show that mortality was greater on seeds buried at 15 cm and 30 cm than at 0 cm. Seed on the soil surface showed the highest germination percentages during the first months of the experiment. A small percentage of seeds buried at 15 cm and 30 remained dormant, with greater dormancy observed for Palmar 18 than for CR-5272. Our results indicate that avoiding seed burial after harvest could be a strategy to manage volunteer rice plants in the field.