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Oral: Fungal Diseases


Worldwide distribution of the sweet potato strains of Ceratocystis fimbriata
Q. LI (1), T. Harrington (2), J. Li (3) (1) China Agricultural University/Postdoctoral Fellows Workstation of Haidian Science Park, China; (2) Iowa State University, U.S.A.; (3) China Agricultural University, China

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Ceratocystis fimbriata is a complex of species with a wide host range and worldwide geographical distribution. However, a sweet potato strain appears to be host specialized to cause black rot of storage roots. Isolates from black rotted roots of sweet potato (Ipomoea batatas) in China, Japan, Indonesia, Papua New Guinea, New Zealand and the USA had identical ITS rDNA sequences and only minor variation in 14 microsatellite loci (only two alleles each for two loci, and the other loci monomorphic). Three Ipomoea microsatellite genotypes (C1, C2 and C3) were found among the 12 isolates from sweet potato in China, two genotypes were found in the three isolates from Japan, and the other 17 isolates had identical microsatellite markers. The DNA sequences of the mating type genes of sweet potato isolates were most similar to those of isolates of C. fimbriata from various host plants in Ecuador, a center of diversity for sweet potato. Ceratocystis fimbriata on sweet potato was first described in 1890 in eastern USA, where black rot has been known for 150 years. It is hypothesized that the fungus was introduced to Japan on sweet potato storage roots and introduced from there to China in the 1930s.