Identification and Toxicological Characterization of Alternaria japonica Strains.

Fungi of the genus Alternaria are producers of biologically active compounds. Alternaria japonica is pathogenic to small radish and certain other crucifers, but has not been studied in sufficient detail. Discrepant data on its toxic metabolites are available in the literature, possibly because a limited set of nutritive substrates was used in culturing or species identification of the strains was incorrect. The objectives of this study were to accurately identify the Russian A. japonica strains and to assess the A. japonica toxigenic potential. Four Russian A. japonica strains were identified using a multifaceted approach, which included analyses of morphological characters (the diameter and morphology of colonies grown on the diagnostic media potato carrot agar (PCA) and yeast extract-glucose (YES) agar for one week), the conidial size, and the presence of chlamydospores), the nucleotide sequences of DNA markers (ITS and EF1α regions), and chemotaxonomic data (mycotoxin production). Biomass and extractive substance yields of A. japonica cultures were found to significantly depend on the composition of the liquid medium. Minor differences between the A. japonica strains were detected via metabolite profiling by HPLC/MS-UV. Extracts of A. japonica cultures exerted phytotoxic activity toward small radish leaves and cytotoxicity toward Paramecium caudatum to a level comparable with that of A. tenuissima extracts. Brassicicolin A, dihydrobrassicicolin A, and phomenins A and B, which are known for several species of the genus Alternaria, were identified in A. japonica extracts. Mycotoxins (alternariol, its methyl ether, tentoxin, tenuazonic acid, and altenuene), which are characteristic of the cosmopolitan species A. tenuissima, were not detected in cultures of the A. japonica strains. Extract toxicity and the yield of extractive substances were studied in the A. japonica strains, and strain MFP244011 proved promising as a producer of known and, presumably, new toxins upon culture on the M1D synthetic medium or semisynthetic liquid media (e.g., the Sabouraud medium).

[The effectiveness of molecular markers for the identification of Lr28, Lr35, and Lr47 genes in common wheat].

The effectiveness of molecular markers for the identification of leaf rust resistance genes Lr28, Lr35, Lr47 transferred to common wheat was assessed the using samplesof Triticum spp. and Aegilops spp. from Ae. speltoides. Markers Sr39F2/R3, BCD260F1/35R2 of gene Lr35 and PS10 of Lr47 gene were characterized by high efficiency and were revealed in a line of common wheat containing these genes, and samples of Ae. speltoides (their donor). Marker SCS421 of Lr28gene and markers Sr39#22r, Sr39#50s, BE500705 of Lr35/Sr39 genes turned out to be less specific. Marker SCS421 was amplified in the samples of the T. timopheevii species, and markers Sr39#22r, Sr39#50s--in the Ae. speltoides, Ae. tauschii, T. timopheevii, line KS90WRC010 (Lr41), the sort of common wheat In Memory of Maistrenko, obtained using synthetic hexaploid T. timopheevii x Ae. tauschii and introgressive lines obtained using Ae. speltoides. Marker BE500705, which indicates the absence of Lr35/Sr39 genes, was not revealed in lines TcLr35 and MqSr39, in Ae. speltoides, Ae. tauschii and T. boeoticum (kk-61034, 61038). Analysis of the nucleotide sequences of amplification products obtained with the markers SCS421 and Sr39#22r indicated their low homology with TcLr28 and TcLr35. Using molecular markers, we showed a different distribution of Lr28 (77%), Lr35 (100%) and Lr47 (15%) genes in 13 studied samples ofAe. speltoides. In introgressive lines derived from Ae. speltoides, contemporary Russian sorts of common wheat and triticale variants Lr28, Lr35, Lr47 genes were not revealed.