title: 3-Methylthiopropionic Acid of Rhizoctonia solani AG-3 and Its Role in the Pathogenicity of the Fungus.
abstract: Studies were conducted to determine the role of 3-methylthioproprionic acid (MTPA) in the pathogenicity of potato stem canker, Rhizoctonia solani, and the concentrations required to inhibit growth of R. solani under laboratory and plant house-based conditions. The experiments were laid out in a completely randomized design with five treatments and five replications. The treatments were 0, 1, 2, 4, and 8 mM concentrations of MTPA. The purified toxin exhibited maximal activity at pH 2.5 and 30°C. MTPA at 1, 2, 4, and 8 mM levels reduced plant height, chlorophyll content, haulm fresh weight, number of stolons, canopy development, and tuber weight of potato plants, as compared to the control. MTPA significantly affected mycelial growth with 8 mM causing the highest infection. The potato seedlings treated with MTPA concentrations of 1.0-8.0 mM induced necrosis of up to 80% of root system area. Cankers were resulted from the injection of potato seedling stems with 8.0 mM MTPA. The results showed the disappearance of cell membrane, rough mitochondrial and cell walls, change of the shape of chloroplasts, and swollen endoplasmic reticulum. Seventy-six (76) hours after toxin treatment, cell contents were completely broken, cytoplasm dissolved, and more chromatin were seen in the nucleus. The results suggested that high levels of the toxin concentration caused cell membrane and cytoplasm fracture. The integrity of cellular structure was destroyed by the phytotoxin. The concentrations of the phytotoxin were significantly correlated with pathogenicity and caused damage to the cell membrane of potato stem base tissue.
authors.affiliation: College of Resources and Environmental Sciences/Gansu Provincial Key Lab of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China; University for Development Studies, Faculty of Agriculture, Tamale, Ghana.
authors.forename: Frederick
authors.initials: F
authors.lastname: Kankam
authors.affiliation: College of Sciences, Gansu Agricultural University Lanzhou 730070, China.
authors.forename: Hai-Tao
authors.initials: HT
authors.lastname: Long
authors.affiliation: College of Sciences, Gansu Agricultural University Lanzhou 730070, China.
authors.forename: Jing
authors.initials: J
authors.lastname: He
authors.affiliation: College of Resources and Environmental Sciences/Gansu Provincial Key Lab of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China.
authors.forename: Chun-Hong
authors.initials: CH
authors.lastname: Zhang
authors.affiliation: College of Sciences, Gansu Agricultural University Lanzhou 730070, China.
authors.forename: Hui-Xiu
authors.initials: HX
authors.lastname: Zhang
authors.affiliation: College of Sciences, Gansu Agricultural University Lanzhou 730070, China.
authors.forename: Lumei
authors.initials: L
authors.lastname: Pu
authors.affiliation: College of Resources and Environmental Sciences/Gansu Provincial Key Lab of Aridland Crop Science, Gansu Agricultural University, Lanzhou 730070, China.
authors.forename: Huizhen
authors.initials: H
authors.lastname: Qiu
keywords: 3-methylthiopropionic acid; Rhizoctonia solani; cell membrane; phytotoxin; stem canker