| Summary: | 碩士 === 國立中興大學 === 植物病理學系 === 93 === Abstract
This study was aimed at determining and describing the Fusarium wilt and other diseases of basil in Taiwan. During 2003-2004, an undiagnosed wilt-type disease of basil was observed in central Taiwan. The first symptoms appeared as defoliation and stunting of the diseased plants, and then the buds and stems showed necrosis. Necrosis developed basipetally from the apex to the entire plant. Sometimes infected plants remained lateral wilt and stems and roots were rot. Vascular bundles showed discoloration. Infected seedlings died rapidly within a few days, and old plants might survive longer. Sometimes white mycelia and spore masses covered rotted stems and buds. A kind of fungus was consistently isolated from diseased tissue. The fungus produced 3 kinds of asexual spores. Microconidia produced abundantly from monophialides on potato dextrose agar (PDA); single-celled, hyaline, elliptic, or ovoid; 5.9-16.3×2.4-4.9μm. Macroconidia were the type “ Fusarium” spores. They were hyaline; 1-4 septates; 19.8-49.5×3.9-5.4μm. Chlamydospores were spherical to ovoid, smooth-surfaced, intercalary or terminal; 7.4-12.3×7.4-12.3μm. The fungus was determined as Fusarium oxysporum Schlechtend:Fr. It was pathogenic to basil ’White stem’ in greenhouse inoculation experiments and produced symptoms similar to those observed in the fields. Host range tests in greenhouse indicated that this fungus could not attack tested Labiatae or other family plants except some cultivars of basil. Moreover, six different forma specialis of F. oxysporum derived from other host plants showed no pathogenicity to basil. Therefore, the pathogen was indentifield as Fusarium oxysporum f. sp. basilici (Dzidzariya) Armst. & Armst. and this disease was be named Fusarium wilt and crown rot of basil. Tested basil ‘White stem’ also appeared symptoms by using suspension inoculation spraying method. The optimal temperature for the mycelial growth was at 28℃. Inoculation tests revealed that the optimal infection temperature for this disease were between 25-30℃. Another undiagnosed disease with leaf blight symptoms also occurred in basil fields during 2003-2004. The symptoms appeared black spot first on leaf margin, then leaf deformed. Finally, the symptoms extended from leaf to stem and plants showed leaf and stem blight. Conidia of the pathogen were brown, ellipsoidal, 21-56 × 7.2-16μm in size, short-beaked (2-6μm), with 2-5 transverse septa and 0-4 longitudinal septa, and catenulated at the apex of the conidiophores. The pathogen was identified as Alternaria alternata (Fries: Fries) von Keissler. Both of the optimal temperature for the mycelial growth and conidia germination were at 24℃. A stem rot of basil was also observed in fields. The infected plants appeared stem and root rot and they didn’t branch. Sometimes white mycelia covered stem and sclerotia were produced on diseased leaf or stem tissue of basil. The symptoms seemed to be the same with Sclerotinia rot of basil. However, the sclerotia never apothecium germinated on artifical medium in laboratory. The optimal temperature for the mycelial growth was at 20℃. Sclerotia could be produced on PDA at or below 28℃, and the pathogen could infected the basil ‘White stem’ at 16-24℃.
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