Molecular Identification and Mycotoxin Production by Alternaria Species Occurring on Durum Wheat, Showing Black Point Symptoms

Abstract

Black point is a fungal disease of wheat, mainly associated with mycotoxigenic <i>Alternaria</i> species. Affected wheat kernels are characterized by dark brown discolouration of the embryo region and reduction of grain quality. Potential risk is the possible accumulation of <i>Alternaria</i> mycotoxins, alternariol (AOH), alternariol-monomethyl ether (AME), tenuazonic acid (TA), and altenuene (ALT), provided by haemato-toxic, genotoxic, and mutagenic activities. One hundred and twenty durum wheat samples belonging to 30 different genotypes grown in Bologna and Modena areas, in Italy, showing black point symptoms, were analyzed for <i>Alternaria</i> species and their mycotoxin contamination. Alternariol was selected as an indicator of the capability of the <i>Alternaria</i> species to produce mycotoxin in vivo in field conditions. The data showed that <i>Alternaria</i> species occurred in 118 out of 120 wheat kernels samples, with the incidence of infected kernels ranging between 1% and 26%. Moreover, AOH was detected by using a HPLC with a diode array detector (LC-DAD) in 98 out of 120 samples with values ranging between 24 and 262 µg Kg^-1. Ninety-two <i>Alternaria</i> representative strains, previously identified morphologically, were identified at species/section level using gene sequencing, and therefore were analyzed for their mycotoxin profiles. Eighty-four strains, phylogenetically grouped in the <i>Alternaria</i> section, produced AOH, AME, and TA with values up to 8064, 14,341, and 3683 µg g^-1, respectively, analyzed by using a LC-DAD. On the other hand, eight <i>Alternaria</i> strains, included in <i>Infectoriae</i> Section, showed a very low or no capability to produce mycotoxins.