Objective 4. Study the incidence of aflatoxin in almond and pistachio orchards and select atoxigenic A. flavus strains in Spain.
We have collected around 100 isolates from different Spanish Nut orchards. Firstly, we developed protocol methods for isolation of these species from Spanish soils using AFAPA and Si. Subsequently, the Aspergillus strains were identified according to their morphological characteristics (mainly type of spores and conidiophore). Those strains could not be unequivocally identified according to their morphological characteristics were identified according to their molecular profile using three DNA regions, ITS, Calmodulin, Bt (Varga et al., 2011; Studies n Mycology 69:57-80). Thirty isolates were characterized according to their ability to produce aflatoxin using Coconut Medium made with powdered coconut. Finally, the aflatoxin produced for the toxic isolates were quantified using an HPLC (Doster et. al. 2014: Plant Dis. 98:948-956). In addition, to identify risk factor associated with the aflatoxin contamination in nut crops in Spain, the susceptibility of different Spanish almond cultivars has been evaluated by artificial inoculations (Moral et al., Phytopathology 107(12): 75). According to our preliminary results, native atoxigenic strains of A. flavus have been isolated for future evaluations. Also, we have identified some Spanish almond cultivars moderately resistant to Aspergillus (then, aflatoxin contamination).
Objective 5. Develop predictive models for aflatoxin contamination in almond and pistachio
The entire set data obtained during the BIOCONTROL-A project and data coming from Michailides’ group have been used for: developing a sensitivity analysis and a mechanistic model to study the competence between toxin and atoxic isolates (Battilani et al. 2012. EFSA report 009-00812. Rossi et al. 2010. in: The Challenge and Use of Heterogeneity, 241-248.). This objective was conducted during a 1-month stay of Dr. Moral in the USCU (Rossi´s Lab). Currently, the sensitivity model is doing validated. In the case of the mechanistic model is still under develop. Interstate, and according to the senility model, in common seasons with low-common percentage of pistachio fruits showing Early Split (ES) or low population of pests in California, the aflatoxin contamination risk is very low, making unnecessary the treatments with biological control agents.
