SURVEY FOR CERATOCYSTIS FIMBRIATA ON SYNGONIUM SPECIES, HOST RANGE TEST AND MOLECULAR CHARACTERIZATION OF THE ISOLATES COLLECTED

Date
2018-12
Authors
Dhakal, Upasana
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Uchida, Janice
Department
Tropical Plant Pathology
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Abstract
Rapid Ohia Death (ROD) caused by Ceratocystis lukuohia and C. huliohia is killing several thousand hectares of ohia forests in the Island of Hawaii. Ceratocystis lukuohia is closely related to C. fimbriata from Syngonium in Hawaii based on phylogenetic analysis. However, the distribution and diversity of the C. fimbriata from Syngonium is not known. Surveys were conducted on the Islands of Oahu, Hawaii, Maui, and Kauai to determine the distribution of C. fimbriata in Syngonium. Ceratocystis fimbriata was recovered from the samples collected from two commercial nurseries in Hilo, Hawaii. Ceratocystis fimbriata was not isolated from the samples collected from Oahu and no Syngonium plants having typical ¬¬¬symptoms of C. fimbriata were obtained from Maui and Kauai. Koch’s postulate was established on Syngonium with the C. fimbriata isolates collected from Syngonium. However, Ohia plants inoculated with C. fimbriata from Syngonium showed no symptoms after three months post inoculation even when the optimal conditions necessary for infections were provided. Ceratocystis fimbriata isolates 3401, 3459 and 3466 were not different to each other in terms of radial growth at 15°C, 20°C, 25°C and 30°C as revealed by analysis of variance at 0.05 level of significance but statistical analysis of the dimensions of perithecia, asexual and sexual spores at the same level of significance showed that C. fimbriata isolates 3401, 3421, 3459 and 3466 were significantly different . Fifteen C. fimbriata isolates collected from Hilo, Hawaii during the survey were clonal. They showed no sequence diversity for Internal Transcribed Spacer (ITS) rDNA region, Beta-tubulin 1(Bt1), Transcription elongation factor-1 alpha (tef1), Guanine Nucleotide binding protein subunit beta-like protein (ms204) and second largest subunits of RNA polymerase II (rpb2). Ceratocystis fimbriata collected from Syngonium in this study was identical for all five genes to C. fimbriata collected from Syngonium in the 1980s and these isolates grouped together in the phylogenetic tree with strong branch support.
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Plant pathology, Ceratocystis fimbriata, Rapid Ohia Death, Syngonium
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86 pages
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