Modulation of the phenylacetic acid metabolic complex by quinic acid alters the disease-causing activity of Rhizoctonia solani on tomato

Abstract

The metabolic control of plant growth regulator production by the plant pathogenic fungus Rhizoctonia solani Kühn (teleomorph=Thanatephorus cucumeris (A.B. Frank) Donk) and consequences associated with the parasitic and saprobic activity of the fungus were investigated. Fourteen genetically distinct isolates of the fungus belonging to anastomosis groups (AG) AG-3, AG-4, and AG-1-IA were grown on Vogel's minimal medium N with and without the addition of a 25 mM quinic acid (QA) source of carbon. The effect of QA on fungal biomass was determined by measuring the dry wt of mycelia produced under each growth condition. QA stimulated growth of 13 of 14 isolates of R. solani examined. The production of phenylacetic acid (PAA) and the chemically related derivatives 2-hydroxy-PAA, 3-hydroxy-PAA, 4-hydroxy-PAA, and 3-methoxy-PAA on the two different media was compared by gas chromatography coupled with mass spectrometry (GC-MS). The presence of QA in the growth medium of R. solani altered the PAA production profile, limiting the conversion of PAA to derivative forms. The effect of QA on the ability of R. solani to cause disease was examined by inoculating tomato (Solanum lycopersicum L.) plants with 11 isolates of R. solani AG-3 grown on media with and without the addition of 25 mM QA. Mean percent survival of tomato plants inoculated with R. solani was significantly higher when the fungal inoculum was generated on growth medium containing QA. The results of this study support the hypotheses that utilization of QA by R. solani leads to reduced production of the plant growth regulators belonging to the PAA metabolic complex which can suppress plant disease development.

Response of <i>Arabidopsis</i> Clones to Toxic Compounds Released by Various <i>Rhizoctonia</i> Species

“…The disease syndrome may evolve rapidly to a fatal consequence in formerly symptomless host (damping off and wilting). Our data support the assumption of crucial role of mycotoxins in evolution of disease syndrome [9,22]. Like to series of host plants [8,10,31] the strain dependent response of A. thaliana clones to Rhizoctonia was demonstrated in our experiments as well.…”

“…Their relationship may change from symbiosis (as in various orchids) to parasitism. The stunted growth can be most frequently observed, which might be related to the effect of Rhizoctonia toxins although few evident experimental proof has been demonstrated yet [9]. Presence of parasitic hyphae can also be commonly seen even in symptomless tissues, and in normal conditions does not cause visible disease symptoms either in phyllosphere or in roots.…”

“…The scoring of disease incidence and severity meet difficulties in the case of Rhizoctonias as some symptoms of disease syndrome can be induced by toxic metabolites of Rhizoctonia alone [9]. In agar cultures, the above two effects can be separated during first days of germination, however, later the damage caused by parasiting hyphae secondary infections of germlings caused by various microbes of spermosphere can mask the visual effect of Rhizoctonia toxins even in agar cultures.…”

Secondary metabolites in fungus-plant interactions

“…Previous research has shown that R. solani also produces phenyl acetic acid and its derivatives (Bartz et al, 2013 ), a phenolic compound, and a carbohydrate as phytotoxins that supported the broad host range and diversity within the R. solani species. Xu et al ( 2015 ) identified eight compounds from fermentation broth of R. solani , from which m -hydroxymethylphenyl pentanoate, (Z)-3-methylpent-2-en-1,5-dioic acid and 3-methoxyfuran-2-carboxylic acid showed phytotoxicity in vitro .…”

3-Methylthiopropionic Acid of Rhizoctonia solani AG-3 and Its Role in the Pathogenicity of the Fungus

“…Following the method of Bartz (2010), potato dextrose (PD) broth medium was balanced to pH 2.5 (that was helpful for pathogenesis), and autoclaved at 121°C and at approximately 16 psig for 45 min, and then amended with a filter-sterilized aqueous solution of MTPA standardized to pH 2.5. Amended media were adjusted to various concentrations of MTPA: 1.0, 2.0, 4.0 and 8.0 mM for use.…”