North African knapweed (Centaurea diluta Aiton) is an annual weed that is widespread in southern Spain and is of increasing concern in dryland cropping systems. Despite its expanding range in Spain, there is limited information on the emergence timing and pattern of this species, knowledge of which is critical for developing more timely and effective management strategies. Therefore, there is a need to develop simple and reliable models to predict the timing and emergence of this annual weed under dryland conditions. A multi-location field experiment was established across Spain in 2016 to 2017 to assess the emergence of C. diluta. At each of 11 locations, seeds were sown in the fall, and emergence was recorded. Overall emergence averaged 39% in the first year across all sites and 11% in the second year. In both years, the main emergence flush occurred at the beginning of the growing season. A three-parameter Weibull function best described seedling emergence of C. diluta. Emergence models were developed based on thermal time (TT) and hydrothermal time (HTT) and showed high predictability, as evidenced by root mean-square error prediction values of 10.8 and 10.7, respectively. Three cardinal points were established for TT and HHT at 0.5, 10, and 35 C for base, optimal, and ceiling temperatures, respectively, while base water potential was estimated at −0.5 MPa.

SummaryPeroxisomal ABC transporters have been studied extensively in Arabidopsis but not in monocotyledonous species. Using barley, it is shown that their biochemical functions are conserved in flowering plants.

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Winter wild oat [Avena sterilis spp. ludoviciana (Durieu) Gillet & Magne referred to as A. sterlis here] is one of the major species of the Avena genus given its high competitive ability to infest cereal crops worldwide, with special concern in Spain. A nine-location field experiment was established across Spain where a total of 400 A. sterilis seeds per location were sowed in four replicates in autumn 2016 to monitor the emergence during two growing seasons in dryland conditions. The data were used to test the predictable ability of a previous published model and to develop a new model, if required. Overall, the average percentage of emergence was 30% during the first season, and 21% during the second one. In both seasons, the main emergence flush occurred between November and February. According to the phenological stage, A. sterilis achieved the tillering earlier in southern sites, between 25 November and the end of December, compared with northern sites where this stage was reached at the end of January. The newly developed model described the emergence with precision, using three cardinal temperatures to estimate the thermal time (TT). The three cardinal points were established at -1.0, 5.8 and 18.0 C for base (Tb), optimum (To) and ceiling temperature (Tc), while the base water potential (Ψb) was established at -0.2 MPa for the hydrothermal time (HTT) estimation. This study contributes to improve the prediction for the emergence of A. sterilis, and provides knowledge for Decision Support Systems (DSS) for the control of this weed.