The effect of sterols on phytoalexin, steroid glycoalkaloid, and sterol accumulation in potato tuber discs inoculated with Phytophthora infestans or treated with arachidonic acid

Mucharromah, H.R.B.rton; Kuc, J.

Physiological and Molecular Plant Pathology 47(1): 13-27

1995


ISSN/ISBN: 0885-5765
DOI: 10.1006/pmpp.1995.1039
Accession: 002713178

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Abstract
Potato tuber discs contain low levels of steroid glycoalkaloids (SGA) and free sterols at 0 h after slicing. Aging the discs increased SGA and free sterol levels in the outer 3 mm of disc surface. Inoculating the discs with incompatible races of Phytophthora infestans or treatment with arachidonic acid (AA) caused a hypersensitive reaction (HR), which included the accumulation of sesquiterpenoid phytoalexins and a marked reduction in the accumulation of steroid glycoalkaloids (SGA) and free sterols, largely beta-sitosterol and stigmasterol. Inoculation with a compatible race elicited little and delayed phytoalexin accumulation, modest reductions in SGA and little or no reduction of free sterol accumulation. Treatment of tuber discs with 1 or 2 mu-g/disc stigmasterol or beta-sitosterol before inoculation with an incompatible race allowed colonization by the fungus, markedly decreased phytoalexin accumulation and decreased the suppression of SGA and free sterol accumulation. Treatment with AA did not prevent colonization by either compatible or incompatible races of P. infestans in the sterol-treated discs. Neither sterol elicited phytoalexin accumulation, nor significantly affected SGA and free sterol accumulation in the absence of the fungus. The sterols also did not affect AA-elicited phytoalexin accumulation the suppression of SGA nor free sterol accumulation in the absence of the fungus.

The effect of sterols on phytoalexin, steroid glycoalkaloid, and sterol accumulation in potato tuber discs inoculated with Phytophthora infestans or treated with arachidonic acid