Arbuscular Mycorrhizal Symbioses in a Cut-And
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Arbuscular mycorrhizal symbioses in a cut-and-carry forage production system of legume tree [i]Gliricidia sepium[/i] and fodder grass [i]Dichanthium aristatum[/i] Riina Jalonen, Sari Timonen, Jorge Sierra, Pekka Nygren To cite this version: Riina Jalonen, Sari Timonen, Jorge Sierra, Pekka Nygren. Arbuscular mycorrhizal symbioses in a cut-and-carry forage production system of legume tree [i]Gliricidia sepium[/i] and fodder grass [i]Dichanthium aristatum[/i]. Agroforestry Systems, Springer Verlag, 2013, 87 (2), pp.319-330. 10.1007/s10457-012-9553-1. hal-01133263 HAL Id: hal-01133263 https://hal.archives-ouvertes.fr/hal-01133263 Submitted on 31 Mar 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Copyright Agroforest Syst (2013) 87:319–330 DOI 10.1007/s10457-012-9553-1 Arbuscular mycorrhizal symbioses in a cut-and-carry forage production system of legume tree Gliricidia sepium and fodder grass Dichanthium aristatum Riina Jalonen • Sari Timonen • Jorge Sierra • Pekka Nygren Received: 17 July 2011 / Accepted: 19 July 2012 / Published online: 29 July 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Arbuscular mycorrhizal (AM) symbioses AM fungal species were identified by DNA sequenc- may alter the competitive abilities of plant species and ing. Colonisation and frequency of types of AM facilitate positive interactions such as nutrient transfer formations varied statistically significantly between between plants. They are therefore particularly inter- the species and sampling points. Arbuscular colonisa- esting components in agroforestry systems. We tion in G. sepium roots was higher under the tree studied spatial variation of AM colonisation on a canopies than on the adjacent grass plot. Soil nutrient cut-and-carry fodder production site (agroforestry content, particularly P and N, and interspecies com- plot) of the legume tree Gliricidia sepium and the petition are the most probable explanations for the fodder grass Dichanthium aristatum. Roots of the two observed variation in AM colonisation. Both arbus- plant species were sampled under the tree canopies cular colonisation and arbuscule:vesicle ratio in and on the adjacent grass plot at 1 and 3.5 m from the D. aristatum roots was lower on the D. aristatum first tree row where G. sepium roots also occur. Roots monocrop than on the agroforestry plot under or near of D. aristatum were also sampled on a nearby grass the tree canopies. Intercropping could stimulate AM monocrop. Colonisation of arbuscules, vesicles and symbiosis in D. aristatum. Both plant species formed hyphae in root samples was visually determined, and symbiosis with Rhizophagus intraradices, indicating potential for interplant N transfer via common myce- lial networks of AM-forming fungi. R. Jalonen (&) Á P. Nygren Department of Forest Sciences, University of Helsinki, P.O. Box 27, 00014 Helsinki, Finland Keywords Arbuscules Á Vesicles Á e-mail: riina.jalonen@helsinki.fi Root colonisation Á Rhizophagus intraradices Á Vertisol Á DNA sequencing Present Address: R. Jalonen Bioversity International, UPM Post Office, PO Box 236, Serdang 43400, Selangor Darul Ehsan, Malaysia Introduction S. Timonen Division of Microbiology, Department of Food and Communities of fungi which form arbuscular mycor- Environmental Sciences, University of Helsinki, P.O. Box rhizae (AM) are recognised as important components 56, 00014 Helsinki, Finland of material cycles in natural and agricultural ecosys- tems. An increasing number of studies indicate how J. Sierra INRA, UR1321 ASTRO, Agrosyste`mes Tropicaux, AM fungal species and communities interact not only 97170 Petit-Bourg, France with individual host plants but with entire plant 123 320 Agroforest Syst (2013) 87:319–330 communities, affecting their composition and struc- roots has been observed at N-limited sites, which ture in various ways. Nutrient acquisition by AM- could reflect higher investment of carbohydrates from forming fungi may increase when plants are grown in the plant to the fungus in order to maintain nutrient mixtures of species as compared to monoculture supply under sub-optimal conditions (Treseder and (Hodge 2003). Symbiosis with AM-forming fungi Allen 2002). Some studies have also compared ratio of may change competitive abilities of plant species, arbuscules to vesicles, suggesting it as an indicator of favouring either the already dominant or the less the relative cost or benefit of the fungus to the host competitive species depending on their mycorrhizal plant (Braunberger et al. 1991; Titus and Leps 2000). dependency (Scheublin et al. 2007). Nutrients may be In contrast, total AM colonisation is often dominated transferred between plant species via common myce- by hyphal colonisation and may be unaffected, e.g. by lial networks of AM-forming fungi (He et al. 2003), interspecific competition or nutrient limitation, even and potential for direct N transfer from legumes to when they result in increases in mycorrhizal depen- associated crops has received considerable interest in dency or vesicle colonisation (cf. Scheublin et al. intercropping systems as a means of improving crop 2007; Treseder and Allen 2002). nutrition and reducing competition for soil N. Trees in Common mycelial networks are formed between agroforestry systems may also act as reservoirs of AM- individual plants when the extraradical hyphae of their forming fungi between cropping seasons, and facili- AM fungal symbionts fuse, i.e. form anastomosis. tate AM colonisation and establishment of annual Anastomoses have empirically been demonstrated crops (Ingleby et al. 2007). Overall, AM symbioses are only between fungal isolates which are genetically capable of altering competitive relationships between identical or belong to the same population (Giovan- plants and mediating their coexistence, thereby con- netti et al. 2006; Croll et al. 2009; see also Mikkelsen tributing to diversity, productivity and stability of the et al. 2008). Shared mycorrhizal symbionts would, plant communities as a whole (Hart et al. 2003; van der thus, be a precondition for transfer of N between plant Heijden et al. 1998). species via common mycelial networks of AM-form- Variation in the occurrence of fungal structural ing fungi. formations arbuscules, vesicles or hyphae may reveal Because of the functional importance of AM functional differences in the AM symbiosis between symbiosis, its spatial variation is of interest in plant species or growth conditions. Arbuscules, highly intercropping systems where spacing and densities of branched structures which are formed when the AM plant species may be managed to optimise productiv- fungal hyphae penetrate individual cells in the root ity or sustainability of the system (Hamel 1996; cortex, are known as the sites where carbon and Boddington and Dodd 2000; Shukla et al. 2009). nutrients are transferred between the plant and the Analysis of changes in AM fungal communities and fungal symbiont (Smith and Read 2008). Highest N colonisation patterns can help to interpret observed and P concentrations in plant tissue coincided with changes in plant communities, and adjust management highest arbuscular colonisation in temperate grass- practices to facilitate favourable interactions between lands where P limited plant growth (Garcia and plant species. Mendoza 2008). Transfer of N from a legume tree to Strong evidence of direct N transfer between plant an associated grass via common mycelial networks of species has been obtained on a well-studied cut-and- AM-forming fungi correlated positively with the carry fodder production plot of the legume tree extent of arbuscular colonisation in the legume roots Gliricidia sepium (Jacq.) Kunth ex Walp and the (Jalonen et al. 2009). Two different types of arbus- fodder grass Dichanthium aristatum (Poir) C.E. Hub- cules, Arum-type and Paris-type, are recognised. bard in Guadeloupe, Lesser Antilles. Nitrogen isotopic Their occurrence has been associated with fitness of signatures of the N recipient D. aristatum correlated the fungal and plant symbionts, while the functional with isotopic signature of G. sepium roots but not with significance of the differences remains unclear (Dick- the surrounding soil (Sierra and Nygren 2006). The son et al. 2007). Vesicles occur in the intra- or inter- grass was observed to preferentially absorb N released cellular space and are assumed to be storage organs for from the tree as opposed to soil N sources (Daudin and energy reserves within the fungus (Smith and Read Sierra 2008). It was subsequently shown under semi- 2008). Increased vesicle colonisation within plant controlled conditions that at least part of the N transfer 123 Agroforest Syst (2013) 87:319–330 321 occurs via common mycelial networks of AM-forming North–South aligned rows at spacing of 0.3 9 2m. fungi (Jalonen et al. 2009). Each of these tree-grass plots were 20 9 13 m in size In this study we analysed spatial variation of AM and separated from the others by grass plots without colonisation on the G. sepium–D. aristatum plot trees, 15 m of width. At