Abstract
Pythium group F is a minor pathogen which induces symptomless infections that occur frequently and results in yield losses in tomato soilless cultures. To elucidate the mode of action of this microorganism, the influence of culture filtrates of Pythium group F on tomato growth was investigated and compared to that of the pathogen Pythium ultimum. Depending on metabolite production by the fungus, marked differences were observed in plant response. Pythium group F crude culture filtrates or low molecular weight fractions (< 500) caused swelling behind the root tip and reduced root growth; the cohesion and adherence of cells within the cortical area were also affected. These symptoms were similar to those observed on plants treated with indole-3-acetic acid. By contrast, P. ultimum filtrates caused a marked distortion of cell shape accompanied with folding of host cell walls, particularly in the cortical area. These symptoms were characteristic of the activity of toxic compound(s) on host cells. Chemical analysis of the filtrates demonstrated that indole-3-acetic acid and tryptophol were produced by Pythium group F and P. ultimum. However, Pythium group F took up and metabolized more indole-3-acetic acid precursors, especially tryptophan, a key amino acid in the pathways leading to indole-3-acetic acid synthesis. The fact that Pythium group F and P. ultimum transformed tryptamine and indole-3-acetaldehyde into indole-3-acetic acid and tryptophol confirms the existence of a tryptamine pathway within both fungi. These results support the hypothesis that auxins facilitate Pythium group F infections. On the other hand, toxin(s) and hydrolytic enzymes are likely involved in P. ultimum pathogenesis.
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Blancard D, Rafin C, Chamont S, Tirilly Y and Jailloux F (1992) Phénomène de perte de racines en culture hors-sol. Rôle des Pythium spp. Pépiniéristes, Horticulteurs, Maraîchers-Revue Horticole 329: 35–45
Chagnon MC and Bélanger RR (1991) Tolerance in greenhouse geraniums to Pythium ultimum. Plant Disease 75: 820–823
Chérif M, Benhamou N and Bélanger RR (1991) Ultrastructural and cytochemical studies of fungal development and host reactions in cucumber plants infected by Pythium ultimum. Physiological and Molecular Plant Pathology 39: 353–375
Désilets H and Bélanger RR (1991) An in vitro system for studying the effects of Pythium ultimum metabolites on Pelargonium × hortorum. Phytopathology 81: 202–206
Désilets H, Benhamou N and Bélanger RR (1994) A comparative study of histological and ultrastructural alterations induced by Pythium ultimum or its metabolites on geranium (Pelargonium) roots. Physiological and Molecular Plant Pathology 45: 21–36
Désilets H (1995) Les métabolites toxiques du Pythium ultimum: mise en évidence de leur implication dans la pathogenése et isolation d'une fraction active. Ph.D. Universit´e Laval, Canada, 109 pp.
Favrin RJ, Rahe JE and Mauza B (1988) Pythium spp. associated with crown rot of cucumbers in British Columbia greenhouses. Plant Disease 72: 683–687
Frankenberger WT and Arshad M(1995) Phytohormones in Soil: Microbial Production and Function. Dekker, New York
Furukawa T, Koga J, Adachi T, Kishi K and Syono K (1996) Efficient conversion of L-tryptophan to indole-3-acetic acid and/or tryptophol by some species of Rhizoctonia. Plant and Cell Physiology 37: 899–905
Gay G, Rouillon R, Bernillon J and Favre-Bonvin J (1989) IAA biosynthesis by the ectomycorrhizal fungus Hebeloma hiemale as affected by different precursors. Canadian Journal of Botany 67: 2235–2239
Hejnowicz Z (1961) The response of the different parts of the cell elongation zone in root to external β-indolylacetic acid. Acta Societatis Botanicorum Poloniae 30: 25–42
Hodges CF and Coleman LW (1985) Pythium-induced root dysfunction of secondary roots of Agrostis palustris. Plant Disease 69: 336–340
Ichihara A, Hashimoto M and Sakamura S (1985) (3R,5Z)-(-)-3-hydroxy-5-dodecenoic acid, a phytotoxic metabolite of Pythium ultimum. Agricultural and Biochemical Chemistry 49: 2207–2209
Jenkins SF and Averre CW (1983) Root diseases of vegetables in hydroponic culture systems in North Carolina greenhouses. Plant Disease 67: 968–970
Kraft JM, Endo RM and Erwin DC (1967) Infection of primary roots of bentgrass by zoospores of Pythium aphanidermatum. Phytopathology 57: 86–90
Linde C, Kemp GH and Wingfield MJ (1994) Pythium irregulare associated with Pinus seedling death on previously cultivated lands. Plant Disease 78: 1002–1005
Martin FN (1995) Pythium. In: Singh US, Kohmoto K and Singh RP (eds) Eukaryotes, Vol 2 (pp 17—36) Pergamon Press, Oxford
Mojdehi H, Singleton LL, Melouk HA and Waller GR (1990) Reproduction of symptoms of a root disease of wheat by toxic metabolites produced by two Pythium species and their partial characterization. Journal of Phytopathology 128: 246–256
Normanly J, Slovin JP and Cohen JD (1995) Rethinking auxin biosynthesis and metabolism. Plant Physiology 107: 323–329
Pitts JR, Cernac A and Estelle M (1998) Auxin and ethylene promote root hair elongation in Arabidopsis. Plant Journal 16: 553–560
Posthumus AC (1973) Extraction, purification and identification of 3-indolacetic acid (IAA) from culture filtrates of Pythium salvaticum. Netherland Journal of Plant Pathology 79: 282–284
Rey P, Benhamou N and Tirilly Y(1996) Ultrastructural and cytochemical studies of cucumber root infected by two Pythium species with different modes of pathogenicity. Physiological and Molecular Plant Pathology 44: 213–231
Rey P, Nodet P and Tirilly Y (1997) Pythium F induce a minor but ubiquitous disease in tomato soilless cultures. Journal of Plant Pathology 79: 173–180
Rey P, Benhamou N and Tirilly Y(1998) Ultrastructural and cytochemical investigation of asymptomatic infection by Pythium spp. Phytopathology 88: 234–244.
Rybicka H (1981) Tryptophan in root exudate of mock orange and tomato. Acta Physiologiae Plantarum 3: 95–98
Sadik EA, Mehta SS, Payak MM and Srinivasan (1982) Isolation and partial characterization of an extracellular phytotoxin produced by Pythium aphanidermatum, a stalk rot pathogen of maize. Journal of Plant Diseases and Protection 89: 266–275
Sadik EA, Payak MM and Mehta SL (1983) Some biochemical aspects of host-pathogen interactions in Pythium stalk rot of maize: I. role of toxin, pectolytic and cellulolytic enzymes in pathogenesis. Acta Phytopathologica Academiae Scientarum Hungaricae 18: 261–269
Salt GA (1979) The increasing interest in 'minor pathogens'. In: Schippers B and Gams W (eds) Soilborne Plant Pathogens (pp 289—312) Academic Press, New York
Shimada A, Takeuchi S, Nakajima A, Tanaka S, Kawano T and Kimura Y (1999) Phytotoxicity of indole-3-acetic acid produced by the fungus, Pythium apahanidermatum. Bioscience, Biotechnology and Biochemistry 63: 87–189
Stanghellini ME and Kronland WC (1986) Yield loss in hydroponically grown lettuce attributed to subclinal infection of feeder rootlets by Pythium dissotocum. Plant Disease 70: 1053–1056
Stanghellini ME and Rasmussen SL (1994) Hydroponics, a solution for zoosporic pathogens. Plant Disease 78: 1129–1138
Yoshii K and Hagedorn DJ (1971) Production of tryptophol and indolacetic acid in culture by Pythium debaryanum. Phytopathology 61: 918–919
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Rey, P., Leucart, S., Désilets, H. et al. Production of Indole-3-acetic Acid and Tryptophol by Pythium ultimum and Pythium Group F: Possible Role in Pathogenesis. European Journal of Plant Pathology 107, 895–904 (2001). https://doi.org/10.1023/A:1013187922191
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DOI: https://doi.org/10.1023/A:1013187922191