Substances of plant and fungal origins stimulatory to sexual reproduction in Phytophthora
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1995
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University of Hawaii at Manoa
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Abstract
Stimulatory effect of phospholipids, lecithin and cephalin on sexual reproduction of Phytophthora cactorum was increased by purification with column chromatography or thin layer chromatography (TLC). Gas chromatography (GC) and mass spectrometry analysis (MS) failed to detect sterols in the highly purified phospholipid samples. Trace amount of cholesterol added to the cephalin did not significantly changed the amount of oospores produced. Therefore, confirming the previous reports that sterols are not essential to sexual reproduction in pythiaceous fungi. Purification and identification of oospore stimulatory compounds from com oil and crude soybean lecithin were carried out by saponification, Florisil column chromatography, TLC, digitonin precipitation, high performance liquid chromatography and GC-MS analysis. Phytol, one of the compound identified from com oil, stimulated sexual reproduction of P. cactorum and P. parasitica. The minimum concentrations of phytol stimulatory to sexual reproduction of P. cactorum and P. parasitica were 0.002 ppm. Lauric, myristic, palmitic, stearic, oleic, linoleic and linolenic acids, and geraniol and squalene induced oospore formation of P. cactorum following purification on TLC. Purified palmitoleic acid was stimulatory to oospore formation of P. cactorum and P. parasitica. Retinol and its esters were also stimulatory to sexual reproduction of P. cactorum and P. parasitica. Nutrient deprivation or growth limitation induced sexual reproduction of P. cactorum cultured on basal medium. The fungus grown in solid or liquid basal medium formed oospores after being transferred to water agarose. Mycelial age, concentration of the basal medium and size of petri plate affected the number of oospores produced by P. cactorum. The non-saponifiables extracted from mycelia of P. cactorum cultured in liquid basal medium stimulated oospore formation of P. cactorum and P. parasitica, while the saponifiables were stimulatory to P. cactorum only. Over all results showed that many compounds commonly found in plants and fungi are stimulatory to sexual reproduction in pythiaceous fungi. The contention that this group of fungi has an absolute requirement of exogenous sterols is, therefore, refuted.
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Phytophthora cactorum--Reproduction
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Botanical Sciences (Plant Pathology); no. 3211
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