Natural Contamination with nivalenol and deoxynivalenol in durum wheat germplasms in Argentina

PALACIOS, S.; FARNOCHI, M.; RAMIREZ, M.; REYNOSO, M.; ZAPPACOSTA, D.; SORESI, D.; TORRES, A.

Merida

Congreso; VI Latinamerican Congress of Mycotoxins; 2010

VI Latinamerican Congress of Mycotoxins

Background: In Argentina durum wheat (Triticum durum Desfontaines) is manly used for the elaboration of dried “pasta”. The national production of “pasta” in 2008 reached 369,600 ton and the consumption per capita was estimated in 8.5 kg/year. The total production is devoted to the local market, since an important decrease in the cropping area, in the last decades, made impossible the international market. This decrease can be explained by different factors such as: a) the demand of varieties with differentiated quality, b) the advance of new commodities with best profitability and c) decrease in the yield and grain quality due to fungal diseases, mainly Fusarium head blight (FHB). Previous studies in our country have shown that the main pathogen associated with FHB is F. graminearum Schwabe. Mycotoxins are frequently associated with the growth and invasion of cereal grains by FHB fungi, being the trichothecenes the most important ones. FHB is the disease that more challenges present for its control. The search for resistant germplasms is one of the strategies to reduce the impact of this disease.   Aim: The aims of this work were to evaluate the incidence of F. graminearum and Fusarium spp. and, the contamination with nivalenol (NIV) and deoxynivalenol (DON) in cultivars and lines used in a program of breeding of durum wheat in Argentina.    Materials and Methods: From varietal trials carried out at Experimental Station in La Dulce, in Buenos Aires Province, 26 durum wheat seed samples (cultivars and lines) were collected during the 2009 harvest season. To determine the percentage (%) of kernel infection by F. graminearum and Fusarium spp., 100 kernels per sample were placed onto Nash Snyder modified pentachloronitrobenzene medium (PCNB). The plates were incubated at 25°C for 7 days with a 12/12 photoperiod under cool-white and black-light fluorescent lamps. Single-spore cultures were obtained. Identification of Fusarium species was done on carnation leaf agar (CLA) and potato dextrose agar (PDA) according to Leslie and Summerell (2006). The analysis of NIV and DON was performed using the methodoly proposed by AOAC (1995). The HPLC system consisted of a Hewlett Packard model 1100 pump (Palo Alto, CA) connected to a Hewlett Packard 1100 Series variable wavelength detector and a data module Hewlett Packard Kayak XA (HP ChemStation Rev. A.06.01). Chromatographic separations were performed on a Luna™ C18 reversed-phase column (100 x 4.6 mm, 5 µm particle size) connected to a guard column SecurityGuard™ (4 x 3.0 mm).   Results and Discussion: All the durum wheat germplasms evaluated showed 100% of contamination with Fusarium spp. F. proliferatum, F. equiseti,  F. semitectum, F. oxysporum  and F. graminearum were the most frecuently species isolated.  The contamination was variable dependent on the cultivars or line evaluated. F graminearum recorded a low level of contamination (8%), this result, could be explained because the dry climate (especially during heading) does not allow F.  graminearum infection. The meteorological conditions have an influence from the beginning of heading to early grain development. Factors such as RH affect F. graminearum infection and fungal invasion, F. graminearum grows ideally at or above 92-94% RH. Although the F. graminearum incidence was low, both NIV and DON were detected in 10 and 11 samples, respectively. The levels of NIV, in positive samples, ranged from 132.00 to 752.00 µg/kg. The levels of DON were low, compared with the level accepted by European Community (1,750.00 µg/kg), except in one cultivar that showed a level of 7,719.00 µg/kg. Conclusion: There was different behavior in the durum wheat germplasms in relation with incidence of F. graminearum and DON and NIV levels. Some cultivars were very susceptible, since in a year with climatic conditions not inductive for FHB, showed high levels of mycotoxin contamination.