Isolation and pathogenicity of Phytophthora sp. from tobacco and its distribution in tobacco areas
1996
Truong, L.R. (National Tobacco Administration, Diliman, Quezon City (Philippines))
A fungus identified as Phytophthora sp. was isolated from wilted tobacco. The fungus grows slowly in potato dextrose agar and produces papillate, lemon-shaped sporangium. The colony was uniform to slightly radiate with irregular edges and moderate aerial hyphae. Aerial hyphae are coenocytic and granulated. Subterranean hyphae are nodose, swollen and irregularly shaped. Isolation of the fungus was facilitated by using water agar medium, careful washing and drying of samples and selection of tissue from the inner portion of the stem. Water agar reduced the growth of other microorganisms and enhanced the selection of Phytophthora colony. Abundant sporangia are produced in this medium 3-5 days after tissue planting. Virulence of the isolate was established through soil, stem and leaf petiole inoculation techniques. It enduced stem rot on inoculated plants as early as 4 days after inoculation. Variables symptoms on naturally infected seedlings, young transplants and older plants were described. Phytophthora sp. was present in tobacco growing areas of Ilocos Norte, Ilocos Sur, La Union, Abra, Misamis Oriental, Iloilo and Quirino [Philippines]
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