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Restriction Fragment Length Polymorphisms and Molecular Analysis of Host Specificity in Fusarium Oxysporum

出版	Texas A & M University, 1991
URL	http://books.google.com.hk/books?id=KC9RNwAACAAJ&hl=&source=gbs_api

註釋Mitochondrial DNA (mtDNA) from Fusarium oxysporum f. sp. niveum was purified, cloned, and its molecular size was determined to be 45.1 [plus or minus] 2.2 kb. The restriction map of mtDNA using four enzymes was similar to the mtDNA map of F. o. f. sp. melonis. Six mtDNA restriction fragment length polymorphisms (RFLP) were detected using cloned Pstl fragments among 50 pathogenic isolates of F. o. f. sp. niveum. Among the mtDNA clones, pFON7 (1.5 kb) was unique in its ability to differentiate all six RFLP groups. Relatedness among five different formae speciales (F. o. f. sp. niveum, f. sp. melonis, f. sp. cucumerinum, f. sp. lagenaria, and f. sp. luffae) within the Cucurbitaceae plant family was also examined. A total of 14 RFLP groups were detected from over 100 isolates. F. o. f. sp. cucumerinum was the most diverse while F. o. f. sp. niveum was the most homogeneous. Phylogenetic analysis revealed that all five formae speciales seemed to share a common ancestor. Six different electrophoretic karyotypes were detected among seven F. o. f. sp. niveum isolates representing the six mtDNA RFLP groups. Chromosome number varied from five to ten and the size of the chromosomes ranged from approximately 900 kb to 4,600 kb. The total genome size of F. o. f. sp. niveum ranged from 13.9 Mb to 26.2 Mb. F. o. f. sp. niveum was transformed to hygromycin B resistance using two heterologous vectors, pDH25 and CosHyg1. All transformants contained multiple integrations and/or tandem repeats of the vector. A genomic library of isolate FL60-3A race 0 was constructed in CosHyg1 and pathogenicity of TX -X ID race 2 was altered using selected recombinant clones of F L -60 -3A . Three transformants were obtained: one was nonpathogeic on the three race-differential watermelon cultivars and two other transformants showed decreased pathogenicity on Charleston Gray and/or Calhoun Gray. One isolate of F. o. f. sp. niveum began to sector after the 18th successive weekly subculture on PDA. Changes in the pattern of 5-methylcytosine in nuclear DNA strands coincided with the sectoring and subsequent successive transfers.