Grain Yield, Quality and Deoxynivalenol (DON) Contamination of Durum Wheat (Triticum Durum Desf.): Results of National Networks in Organic and Conventional Cropping Systems

This work shows the results of trials carried out over three years (2006-2008) within the national networks of durum wheat grown under conventional and organic cropping systems in six representative locations of the main cultivation areas of Italy. The main aspects of grain yield and grain quality were analyzed, particularly assessing the hygienic health status of the grain in relation to the possible presence of deoxynivalenol (DON) contamination. DON is considered the most common trichothecene mycotoxin found in the wheat grain, causing significant reductions in grain yield and adverse effects for human or animal consumption. In the studied period the average grain yields were quite interesting both in conventional samples (5.85 t ha-1) and in organic ones (4.91 t ha-1). As expected, the organic yields were significantly different(-16%). However, in the southern locations the same differences were lower (-5%), thus emphasizing the limited impact of the higher inputs of the conventional cropping in these environments. The reduced nitrogen input is notoriously the most critical point of organic wheat, because the protein content is the most sensitive parameter of grain quality. The protein content was significantly different among year, fields location and cropping system, but not among their interactions. Grain protein content in organic wheat was lower than in conventional one all over the three years; anyway, differences were somewhat limited (only about 1% in the southern locations and 0.5% in central Italy). Among cultivars no significant differences in the protein content were recorded. Mean levels of DON contamination during the study period were generally lower, with only a sample exceeding the legal limit of 1750 ppb. Among the main factors, year and location (and their interaction) had a strong influence on DON contamination, accounting for 75% of the observed variability. DON levels in 2008 at Papiano-PG were dramatically high; the strong influence of the year-location interaction may be due to this fact. Cropping system and cultivar, although significant, had a low influence; however, their interaction accounted for 13% of total variance. Cropping system – location interaction accounted for 5% of the total variability. Very low levels of DON were detected in the southern locations with both cropping systems; the lower levels were recorded in organic wheat samples. In the central Italy areas DON could represent a potential hazard, but even in these organically cropped environments wheat gave the best results. Lower concentrations of DON were detected in organic wheat samples, either in less favourable years for the occurrence of Fusarium (2006 and 2007) and in the more favourable one (2008). Regarding the role of the varietal choice, Creso revealed to be the less susceptible to DON contamination, probably as it is the best adapted to the areas of the Central Italy, where Fusarium is more widespread.