In order to evaluate the effect of Glomus versiforme fungus on genes and metabolites related to the biosynthetic pathway of polyamines in pot marigold under drought stress, an experiment was conducted at three irrigation levels [100, 65, and 35% of field capacity (FC)] for 1, 2, 4, and 8 d in mycorrhizal (M) and non-mycorrhizal (NM) plants. At both 35 and 65% FC, putrescine (Put) accumulation peaked at 1 d. Accompanying the accumulation of Put at 1 d, there was an increase in the expression of ARG and ODC genes directly involved in the Put biosynthetic pathway, as well as the ADC, AIH, and CPA genes involved in the indirect Put biosynthetic pathway. At 1 d, M plants induced the accumulation of Put and increased the expression of ADC, AIH, and CPA, but had no significant effect on ODC expression. At both 35 and 65% FC, SAMDC gene expression increased from 1 to 8 d, and the expression of this gene was higher in M plants from 2 to 8 d. At both drought levels, highest Spd content and SPDS gene expression were observed at 2 d. Moreover, Spd accumulation from 2 to 8 d and SPDS gene expression from 4 to 8 d were higher in M plants than in NM plants. At both drought levels, Spm content and SPMS gene expression increased between 4 and 8 d, during which the accumulation and expression level of this gene in M plants was higher.
