Exotic plants, such as Eragrostis plana in southern Brazil, may cause significant problems in agriculture. This study aimed to elucidate the influence of E. plana rhizosphere soil on wheat germination and initial development. Bioassays with soil sampled from an infested agroecosystem were carried out using wheat as the target species. A factorial design was used, crossing soil from the horizontal and vertical distances from the E. plana tiller base and considering seasons as a blocking factor. The interaction between season and vertical and horizontal soil positions influenced normal wheat seed germination, with the lowest values (69%) observed in the winter bottom and intermediate soil positions. The highest abnormal seedling percentage (17.6%) was recorded in the summer middle vertical soil position. Dormant wheat seeds were higher (7%) in the spring bottom and distal soil positions. The season was the most important factor for germination, but hypocotyl, radicle, and total wheat seedling length also varied according to soil position. Shorter hypocotyls and seedlings were registered in the summer soil surface, while shorter radicles were observed in the proximal horizontal soil position in the same season. This variable response of wheat germination and seedling development to the infested soil demonstrated E. plana seasonality. The influence also varied according to the distance from the plant tiller base. These findings may be used to improve E. plana management in infested fields and to understand the mechanism of action of its allelochemicals in future research.

The high sensitivity of beans to herbicides is one of the limiting factors regarding the management of dicot weeds in bean crops. Protoporphyrinogen oxidase (PPO) inhibition is an important mechanism of action that has unregistered molecules with potential use in bean crops. The objectives of this study were to investigate the tolerance of Brazilian bean cultivars to distinct PPO inhibitors and to determine the existence of cross-tolerance in cultivars to the different PPO inhibitor chemical groups. In the first and second experiments, the BRSMG Talismã, Jalo Precoce, BRS Esplendor, and IPR 81 cultivars were subjected to saflufenacil doses pre- (0, 9.6, 14.1, 20.5, 30.0, and 43.8 g a.i. ‧ ha–1) and post-emergence (0, 0.7, 1.0, 1.5, 2.1, and 3.1 g a.i. ‧ ha–1). In the third experiment, the tolerance of 28 bean genotypes to saflufenacil (20.5 g a.i. ‧ ha–1) in pre-emergence was determined. In the fourth, fifth, sixth and seventh experiments, we investigated the cross-tolerance of bean to the fomesafen, flumioxazin, sulfentrazone, and saflufenacil herbicides, respectively. Even very low saflufenacil doses in post-emergence caused plants of all cultivars to die rapidly; therefore, the tolerance was much lower at this application time than in pre-emergence. There was high tolerance variability to saflufenacil among the 28 cultivars. The bean tolerance to fomesafen, flumioxazin, sulfentrazone, and saflufenacil applied pre-emergence depended on the cultivar and dose. Fomesafen was highlighted owing to its higher selectivity in relation to the different cultivars. No cross-tolerance pattern to the PPO inhibitor chemical groups applied in pre-emergence was observed among the evaluated bean cultivars. The results of this study could be of significance to farmers and technical assistance personnel, as well as for future research on cultivar breeding and the elucidation of biochemical and genetic mechanisms involved in herbicide tolerance.