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Identification of the Alternaria and Fusarium Species Associated with Seeds of Brassica rapa

Xuehong Wu: China Agricultural University

<div><em>Brassica rapa</em> is an important vegetable in China and some diseases incited by plant pathogenic fungi are reported to cause yield loss on it. Among these plant pathogens, the <em>Alternaria</em> and <em>Fusarium</em> species can be seedborne. In the present study, the detection of seedborne <em>Alternaria</em> and <em>Fusarium</em> for twenty one varieties of <em>Brassica rapa</em> seeds from China were carried out by washing test and PDA plate methods. Besides, the effect on seed germination of the two kinds of fungi and their pathogenicity tests on detached leaves or seedlings of <em>Brassica rapa</em> were conducted as well. On the basis of morphological traits and molecular characteristics, the species of 113 <em>Alternaria</em> isolates from <em>B. rapa</em> seeds are<em> A. tenuissima</em>, <em>A. alternata</em>, <em>A. infectoria</em>, <em>A. brassicicola</em>, and <em>A. obovoidea</em>; and the species of 22 <em>Fusarium </em>isolates from <em>B. rapa</em> seeds are <em>F. equiseti</em>, <em>F. proliferatum</em>, <em>F. verticillioides</em>, <em>F. oxysporum</em>, and <em>F. tricinctum.</em> After dipping into spore suspension, the germination energy, percentage germination, germination index, and vigor index of <em>Brassica rapa</em> seeds decreased. Both <em>Alternaria</em> and <em>Fusarium</em> isolates selected could cause disease on the detached leaves or roots of seedlings of <em>Brassica rapa</em>. To the best of our knowledge, it’s the first report in China that <em>Brassica rapa</em> seeds can carry pathogenic strains of <em>Alternaria</em> and <em>Fusarium</em>.</div>