Architecture and developmental dynamics of the external mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown under monoxenic conditions

The structural development of arbuscular mycorrhiza extraradical mycelium is difficult to fol- low in soil-based systems. The use of dual arbuscular mycorrhizal fungi/in vitro root organ cultures (mon- oxenic AM cultures) allowed the nondestructive study of hyphal development following establishment of the symbiosis. The present study shows that the extraradical spreading of the arbuscular mycorrhizal fungus Glomus intraradices grown monoxenically with tomato roots can be divided into three stages: (i) pro- liferation of runner hyphae acting as conducting channels, which divide dichotomously and extend the fungal colony radially; (ii) development of arbus- cule-like structures, which are formed at regular in- tervals along the runner hyphae and which might play a preferential role in nutrient uptake; and (iii) formation of spores in zones already colonized by runner hyphae and arbuscule-like structures. The de- velopment of the mycorrhiza is accompanied by changes in the pH of the medium. In particular, pH decreases in zones of the medium in which a high number of arbuscular mycorrhizal fungal spores are formed. The intricate architecture shown by the ex- traradical mycelium highlights the potential for en- hanced nutrient uptake by mycorrhizal roots, and their role in the maintainance and amelioration of soil structure.

[1]  B. Bago,et al.  Changes in the rhizospheric pH induced by arbuscular mycorrhiza formation in onion (Allium cepa L.) , 1997 .

[2]  S. Declerck,et al.  In vitro mass-production of the arbuscular mycorrhizal fungus, Glomus versiforme, associated with Ri T-DNA transformed carrot roots , 1996 .

[3]  R. D. Williams,et al.  Effects of N source on pH and nutrient exchange of extramatrical mycelium in a mycorrhizal Ri T-DNA transformed root system , 1996, Mycorrhiza.

[4]  B. Bago,et al.  Nitrate depletion and pH changes induced by the extraradical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices grown in monoxenic culture. , 1996, The New phytologist.

[5]  M. Giovannetti,et al.  Analysis of factors involved in fungal recognition responses to host-derived signals by arbuscular mycorrhizal fungi , 1996 .

[6]  M. St-Arnaud,et al.  Enhanced hyphal growth and spore production of the arbuscular mycorrhizal fungus Glomus intraradices in an in vitro system in the absence of host roots , 1996 .

[7]  I. Chet,et al.  Mycoparasitism of the extramatrical phase of Glomus intraradices by Trichoderma harzianum , 1996 .

[8]  T. Taylor,et al.  Fossil arbuscular mycorrhizae from the Early Devonian , 1995 .

[9]  H. Marschner,et al.  Role of Arbuscular Mycorrhizal Fungi in Uptake of Phosphorus and Nitrogen From Soil , 1995 .

[10]  D. H. Jennings.  The Physiology of Fungal Nutrition , 1995 .

[11]  S. Gianinazzi,et al.  Impact of Arbuscular Mycorrhizas on Sustainable Agriculture and Natural Ecosystems , 1994, ALS Advances in Life Sciences.

[12]  G. Bethlenfalvay,et al.  Arbuscular mycorrhizas and agrosystem stability , 1994 .

[13]  B. Bago,et al.  Physiological characteristics of the host plant promoting an undisturbed functioning of the mycorrhizal symbiosis , 1994 .

[14]  J. Dodd.  Approaches to the study of the extraradical mycelium of arbuscular mycorrhizal fungi , 1994 .

[15]  J. Bousquet,et al.  Origin and diversification of endomycorrhizal fungi and coincidence with vascular land plants , 1993, Nature.

[16]  G. Bécard,et al.  LIFE CYCLE OF GLOMUS INTRARADIX IN ROOT ORGAN CULTURE , 1992 .

[17]  D. Sylvia.  Quantification of external hyphae of vesicular-arbuscular mycorrhizal fungi , 1992 .

[18]  H. Marschner,et al.  Phosphorus depletion and pH decrease at the root–soil and hyphae–soil interfaces of VA mycorrhizal white clover fertilized with ammonium , 1991 .

[19]  Michael F. Allen,et al.  The Spread of Va Mycorrhizal Fungal Hyphae in the Soil: Inoculum Types and External Hyphal Architecture , 1991 .

[20]  G. Bécard,et al.  Fungal Growth Stimulation by CO2 and Root Exudates in Vesicular-Arbuscular Mycorrhizal Symbiosis , 1989, Applied and environmental microbiology.

[21]  G. Bécard,et al.  Early events of vesicular-arbuscular mycorrhiza formation on Ri T-DNA transformed roots. , 1988, The New phytologist.

[22]  D. Miller,et al.  A new technique for monitoring hyphal growth of vesicular-arbuscular mycorrhizal fungi through soil , 1987 .

[23]  J. Tisdall,et al.  Stabilization of Soil Aggregates by the Root Systems of Ryegrass , 1979 .

[24]  B. Marsh.  Measurement of Length in Random Arrangements of Lines , 1971 .

[25]  T. Nicolson.  Mycorrhiza in the Gramineae: I. Vesicular-arbuscular endophytes, with special reference to the external phase , 1959 .

[26]  B. Mosse.  Observations on the extra-matrical mycelium of a vesicular-arbuscular endophyte , 1959 .