Estimation of biological parameters for germination of abutilon theophrasti medik

Background and Purpose: Velvetleaf seed longevity and prolonged emergence complicate assessing appropriate time for its control. Estimating biological parameters (base temperature and base water potential) is a first step towards development of emergence predictive model for this weed species in summer crops. Since, development of new model is time consuming, the aim of the research was to provide the data set of biological thresholds for Croatian ecotype and then to compare it with Italian velvetleaf thresholds to assess the implementation of AlertInf predictive weed emergence model from Italy to Croatia. Materials and methods: Laboratory experiments were conducted with 100 seeds per three replicates at seven constant temperatures (4, 8, 12, 16, 20, 24, 28°C) to estimate base temperature (Tb) and at seven water stress levels (0.00, –0.05, –0.10, –0.25, –0.38, –0.50, –0.80, –1.00 MPa) to estimate base water potential (Ψb). Results: Germination was fastest at temperature > 20°C with 3.6 days and at water stress level > –0.25 MPa with 4.9 days to complete 50% of germination (t50). The slowest t50 occurred at 4°C (41.9 days) and < –0.38 MPa (10.1 days). Estimated Croatian velvetleaf biological parameters are: 4.5°C (Tb) and –0.67 MPa (Ψb) with no significant difference compared to Italian ecotype, according to 95% confidence intervals overlapping. Conclusion: The results indicate that it could be possible to implement AlertInf model from Italy to Croatia for this weed species without additional adjustment. Nevertheless, next step of this implementation should include validation of estimated results in the field conditions.