Arbuscular Mycorrhizal Fungi Population Research Articles

Arbuscular Mycorrhizal Inoculant Increases Yield of Spice Pepper and Affects the Indigenous Fungal Community in the Field

Although the majority of horticultural crops are mycorrhiza-dependent, the role of arbuscular mycorrhizal (AM) inoculation in plant production has been neglected in high-input agriculture. Field application of a commercial inoculum mix of Glomus spp. was tested in spice pepper (Capsicum annuum L. var. longum), cv. Szegedi, cultivation. With polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP), differences in small subunit ribosomal RNA genes were used to characterize groups of arbuscular mycorrhizal fungi (AMF) with respect to effects of mycorrhizal inoculation on an indigenous AMF population. The AMF inoculant was able to establish in the rhizosphere of pepper plants and mycorrhizal inoculation increased yield of spice pepper by more than 65% compared with the non-treated control plants. Having relatively high root colonization in the control, non-inoculated treatment indicated high presence of indigenous populations of AMF in the field soil. Although the inoculation affected structure of the resident AM fungal community, it did not influence the composition of AMF associated with pepper roots significantly.

Arbuscular mycorrhizal associations in different forest tree species of Hazarikhil forest of Chittagong, Bangladesh

Biodiversity of arbuscular mycorrhizal (AM) colonization and AM fungal spores were studied in the roots and rhizosphere soils of Acacia catechu (L.f). Wild., A. mangium Willd, Anthocephala cadamba Miq., Artocarpus chaplasha Roxb., Chickrassia tabularis A. Juss., Swietenia macrophylla King., Tectona grandis L. from plantations; Albizia procera (Roxb.) Benth., A. falcataria L., Alstonia scholaris (L.) R. Br., Aphanamixis polystachya (Wall.) Parker., Hydnocarpus kurzii (King.) Warb., Heynea trijuga Roxb., Lagerstroemia speciosa (L.) Pers., Messua ferrea Linn., Podocarpus nerifolia Don., Swintonia floribunda Griff., Syzygium fruticosum (Roxb.) DC., S. grandis (Wt.) Wal. from forest and nursery seedlings of A. polystachya, A. chaplasha, Gmelina arborea Roxb. and S. cuminii (L.) Skeels from Hazarikhil forest, Chittagong of Bangladesh. Roots were stained in aniline blue and rhizosphere soils were assessed by wet sieving and decanting methods. The range of AM colonization varied significantly from 10%–73% in the plantations samples. Maximum colonization was observed in A. mangium (73%) and minimum colonization was observed in C. tabularis (10%). Vesicular colonization was recorded 15%–67% in five plantation tree species. The highest was in A. cadamba (67%) and the lowest was in T. grandis; A. chaplasha and C. tabularis showed no vesicular colonization. Arbuscular colonization was recorded 12%–60% in four plantation tree species. The highest was in A. mangium (60%) and the lowest was in A. cadamba. Roots of Artocarpus chaplasha, C. tabularis and T. grandis showed no arbuscular colonization. Among 12 forest tree species, nine tree species showed AM colonization. The highest was in A. falcataria (62%) and the lowest was in S. fruticosum (10%). Significant variation in vesicular colonization was recorded in seven forest tree species. The highest was in H. trijuga (52%) and the lowest was in L. speciosa (18%). Hydnocarpus kurzii, M. ferrea, P. nerifolia S. fruticosum and S. grandis showed no vesicular colonization. Arbuscular colonization was recorded in seven forest tree species. The highest was in A. falcataria (60%) and the lowest was in A. procera (10%). All the nursery seedlings showed AM colonization and the range was 10%–73%. Vesicules were recorded in G. arborea (40%) and S. cumini (40%). Arbuscular colonization was recorded in G. arborea (100%) and S. cumini (100%). Spore population was recorded 77–432/100 g dry soils, 80–276/100 g dry soils, and 75–153/100g dry soils in plantation, forest and nursery, respectively. Glomus and Acaulospora were dominant genera among the six AM fungi recorded. Significantly positive correlation was observed between AM colonization and AM fungal spore population in Hazarikhil plantation tree species, forest tree species and nursery tree seedlings. The present study showed the biodiversity of root colonization and AM fungi are active in nutrient cycling, survivals and seedling establishment of the plants in the Hazarikhil forest, plantation and nursery.

Diversity and efficiency of arbuscular mycorrhizal fungi in soils from organic chili (<i>Capsicum frutescens</i>) farms

No previous studies have been conducted on the diversity and population of arbuscular mycorrhizal fungi (AMF) in relation to organically grown chili (Capsicum frutescens L.) in Thailand. This study was carried out to investigate the diversity and status of AMF populations at four organically managed farms in Ubon Ratchathani and Sisaket provinces. The effects of each AMF species on the growth and nutrient uptake of chili grown in sterile, organically managed soil were determined. Fourteen AM fungal taxa belonging to the genera Acaulospora (4 spp.), Entrophospora (1 sp.), Glomus (7 spp.) and Scutellospora (2 spp.) were found. Among these, Glomus was the dominant genus found at all sites, followed by Acaulospora. The spore density and root colonization of AMF on chili did not vary significantly among the sites. The effects of ten selected AMF species on the growth of chili showed that Gl. clarum RA0305 increased the growth, flowering, and fruit production of chili, and also increased the P uptake significantly, compared to non-mycorrhizal plants. This fungus showed the highest potential as a promoter of growth, flowering and yield in organically managed chili production.

Diversity and efficiency of arbuscular mycorrhizal fungi in soils from organic chili (Capsicum frutescens) farms

No previous studies have been conducted on the diversity and population of arbuscular mycorrhizal fungi (AMF) in relation to organically grown chili (Capsicum frutescens L.) in Thailand. This study was carried out to investigate the diversity and status of AMF populations at four organically managed farms in Ubon Ratchathani and Sisaket provinces. The effects of each AMF species on the growth and nutrient uptake of chili grown in sterile, organically managed soil were determined. Fourteen AM fungal taxa belonging to the genera Acaulospora (4 spp.), Entrophospora (1 sp.), Glomus (7 spp.) and Scutellospora (2 spp.) were found. Among these, Glomus was the dominant genus found at all sites, followed by Acaulospora. The spore density and root colonization of AMF on chili did not vary significantly among the sites. The effects of ten selected AMF species on the growth of chili showed that Gl. clarum RA0305 increased the growth, flowering, and fruit production of chili, and also increased the P uptake significantly, compared to non-mycorrhizal plants. This fungus showed the highest potential as a promoter of growth, flowering and yield in organically managed chili production.

Arbuscular mycorrhizal fungi (Glomeromycota) of soils of the Lubuskie province

In the year 2003, the occurrence of arbuscular mycorrhizal fungi (AMF) of the phylum <i>Glomeromycota</i> in cultivated and uncultivated soils of the Lubuskie province was investigated. The occurrence of AMF was examined based on 56 root and rhizosphere soils collected under 7 species of cultivated and uncultivated plants growing in 28 localities. Spores of AMF were isolated from both field-collected samples and trap cultures. They were revealed in 100% of field soils and 93.8% of trap cultures and represented 7 of the 8 recognized genera of the <i>Glomeromycota</i>. The arbuscular fungi occurring distinctly more frequently in the soil and root samples examined were members of the genus <i>Glomus</i>. The species of AMF most frequently occurring in cultivated soils of the Lubuskie province were <i>G. claroideum</i>, <i>G. constrictum</i>, <i>G. deserticola</i> and <i>G. mosseae</i>, whereas <i>G. claroideum</i>, <i>G. constrictum</i>, <i>G. deserticola</i>, <i>G. mosseae</i>, and <i>S. dipurpurescens</i> were more frequently found in uncultivated sites. The analysis of similarity of the species composition of AMF populations in sites of the Lubuskie province and the Western Pomeranian province earlier examined showed that (1) the occurrence in Poland of most taxa of these fungi detected in the study presented here is even and does not change with time, (2) the communities of AMF area are stable, despite the arduousness resulting from the agricultural and chemical practices conducted, and (3) the species diversity of the plants cultivated in a long period of time has no influence on the species composition of populations of AMF.

Temporal or spatial arrangements of cover crops to promote arbuscular mycorrhizal colonization and P uptake of upland crops grown after nonmycorrhizal crops

A field experiment was conducted where maintenance of indigenous arbuscular mycorrhizal (AM) fungal populations was attempted using AM host cover crops arranged temporally or spatially during growth of nonmycorrhizal crops. To arrange AM hosts temporally, sunflower or oat was grown as a cover crop after non-host cropping (cabbage) or fallowing. In order to arrange AM hosts spatially, red clover, white clover or vetch was intercropped during growth of non-host cabbage. The AM colonization and growth of maize with previously introduced sunflower or oat were much greater than those without introduction of cover crops or those with introduction of non-host cover crops. The AM colonization and yield of winter wheat grown after cabbage with AM host intercropping were greater than those after cabbage only cropping, suggesting that arrangement of AM hosts between cabbage rows is effective for maintaining the AM fungal population in soil during non-host cropping. Mycorrhizal hosts cropped after or during non-host cropping is an effective means to increase indigenous AM fungal populations. The results show that AM colonization, P uptake and productivity of crops after cultivation of nonmycorrhizal crops can be improved by arranging AM hosts temporally or spatially as cover crops.

Frequent cultivation prior to planting to prevent weed competition results in an opportunity for the use of arbuscular mycorrhizal fungus inoculum

AbstractInoculation with arbuscular mycorrhizal (AM) fungi is a potentially useful tool in agricultural systems with limited options regarding use of synthetic chemicals for fertility and pest control. We tested the response ofAllium porrumcv. Lancelot to inoculation with AM fungi in a field high in available P (169 μg g−1soil) that had been repeatedly cultivated to control weeds. Seedlings were inoculated during the greenhouse production period with a mixed species inoculum produced on-farm in a compost and vermiculite medium withPaspalum notatumFlugge as a nurse host. Inoculated and uninoculated seedlings were the same size at outplanting. Inoculated seedlings were over 2.5-fold greater in shoot weight and shoot P content than uninoculated seedlings at harvest. These results demonstrate the potential yield benefits from inoculation with AM fungi in situations where farm management practices may negatively impact on indigenous populations of AM fungi.

Influence of Summer Cover Crops and Mycorrhizal Fungi on Strawberry Production in the Southeastern United States

The effects of eight summer cover crop treatments combined with two arbuscular mycorrhizal (AM) fungal inoculants on strawberry growth and yields were examined in a 2-year field experiment. Cover crop treatments included 1) sudangrass [Sorghum bicolor (L.) Moench cv. Piper]; 2) pearl millet [Pennisetum glaucum (L.) R.Br. cv. 102 M Hybrid]; 3) soybean [Glycine max (L.) Merrill cv. Laredo]; 4) velvetbean [Mucuna deeringiana (Bort) Merr. cv. Georgia Bush]; 5) sudangrass/velvetbean combination; 6) pearl millet/soybean combination; 7) a non-mycorrhizal host consisting of rape (Brassica napus L. var. napus cv. Dwarf Essex) and buckwheat (Fagopyrum esculentum Moench) in Year 1 and Year 2, respectively; and 8) no cover crop control. Strawberry tips were inoculated with either a native mixture of several AM fungal species or a single species sold commercially, Glomus intraradices. Cover crop treatments were assessed for their aboveground biomass and nutrient uptake as well as their impacts on weed abundance and diversity, soil nutrients, and parasitic nematode populations. Cover crop and AM treatments were assessed for their impact on strawberry growth, yields, AM root colonization, and nutrient uptake. Grass-based cover crop treatments, particularly pearl millet, produced the most aboveground biomass. In both years, all cover crop treatments reduced summer weed biomass compared with the control. Neither cover crop nor AM treatments had an effect on overall strawberry plant growth or yields in either year, although some differences existed at specific growth periods. The results suggest that cover crops are a viable strategy for reducing summertime weeds and that background, native populations of AM fungi in the soil may be just as effective as a commercially available species. It is likely that no overall yield benefit was found among treatments for two reasons: 1) nutrients, especially nitrogen, were not limiting; and 2) the cover crop growth window may have been too short for a significant impact on strawberries over two seasons.

Response of Theobroma cacao and Inga edulis seedlings to cross-inoculated populations of arbuscular mycorrhizal fungi

Response of Theobroma cacao L. (cacao) and the shade tree Inga edulis Mart. (inga) seedlings from an organically-grown cacao plantation to inoculation with native arbuscular mycorrhizae forming fungi (AMF) was studied in a cross-inoculation assay under greenhouse conditions. Seedlings of inga and cacao were grown in pots filled with heat-treated soil from the plantation. Control was heat-treated soil without inoculum and roots of cacao and inga from the plantation were applied as AMF inocula. Undisturbed soil blocks were used as a “positive control” of the inoculation potential of untreated soil and roots combined. No AMF structures were observed in the roots of either species in the heat-treated control. All inocula were infective in both hosts and the differences in the total AMF colonization percentage between the hosts were not significant but inga had significantly higher colonization by hyphal coils and arbuscules. Cacao roots but neither inga roots nor soil block inocula stimulated cacao growth. All inocula significantly increased growth of inga, which had higher relative mycorrhizal responsiveness than cacao. Thus, in spite of the strong infectivity of the inocula in both hosts, cacao and inga responded differently to the same AMF populations. The strong conspecific preference of cacao suggests that attention must be paid to the AMF inoculum used for this species. However, the strong response of inga to cacao root inoculum indicates that the two species may share same AMF symbionts, thus enabling positive interactions between them, including formation of common mycelial networks.

The application of an organic amendment modifies the arbuscular mycorrhizal fungal communities colonizing native seedlings grown in a heavy-metal-polluted soil

A mesocosm experiment was conducted to investigate whether communities of arbuscular mycorrhizal (AM) fungi associated with roots of native (Piptatherum miliaceum, Retama sphaerocarpa, Psoralea bituminosa, Coronilla juncea, and Anthyllis cytisoides) and for comparison (Lolium perenne) seedlings in a heavy-metal-contaminated, semiarid soil were affected by the application of composted sugar beet waste. We also investigated whether there were relation between AMF diversity and metal concentration (Al, Cd, Cu, Fe, Mn, Pb and Zn) and total P in shoot as well as some soil parameters (total organic carbon and total N) when the SB waste was added to the soil. We analyzed a portion of approximately 795 base pairs of the small-subunit (SSU) rRNA gene by nested PCR, cloning, sequencing, and phylogenetic analyses. Twelve different AMF sequence types were distinguished: seven of these belonged to Glomus group A, one to Glomus group B, one to Diversispora, one to Archaeospora, and two to Paraglomus. The AM fungal populations colonizing roots in a heavy-metal-polluted soil were quite dependent on the host plant, the highest diversity values being obtained in authochtonous plants recognized as metallophytes, such as P. bituminosa, and in an allochtonous, invasive species (L. perenne). No significant correlation was found between AMF diversity and plant metal concentration and soil parameters. Excepting P. bituminosa, when sugar beet waste was added to soil, the populations of AM fungi in roots increased and the shoot metal concentrations decreased in all host plant species studied. Therefore, the addition of sugar beet waste can be considered a good strategy for the remediation and/or phytostabilization of mine tailing sites.

Soil parameters and host plants associated with arbuscular mycorrhizae in the grazed Magellanic steppe of Tierra del Fuego

Association between soil properties and two host plants for arbuscular mycorrhizal fungi in a field study involving grasslands exhibiting a range of degradation as a result of long-term modes of sheep grazing in Tierra del Fuego (Argentina) was researched. Vegetation rich in prostrate shrubs ( Empetrum rubrum) of little forage value that grow in soils of low pH, high carbon, low N, and low Ca + Mg were associated with selective long-term grazing at high intensity. Vegetation with large proportions of mycorrhizal grasses such as Poa rigidifolia and Deschampsia flexuosa, which species grow in soil of less acidity, low carbon/nitrogen ratio, high NO 3 − and high exchangeable Ca + Mg, were associated with selective grazing at moderate intensities or nonselective grazing at high intensity in short term. These two grasses, representing more palatable and nutritious plants for sheep, were present at different degrees of coverage and AM-spore densities in their rhizospheric soils. Twenty-five species of AM-fungal spores belonging to the Acaulosporaceae (41.4%), Glomeraceae (36.2%), Ambisporaceae (13.6%), Pacisporaceae (8.4%), and Scutellosporaceae (0.4%) were identified. Ambisporaceae spores were associated with low fertility and light soils, Glomeraceae spores with more fertile soils and disturbed ecosystems, and Acaulosporacea spores with less disturbed ecosystems. Our results indicated that the sheep-grazing mode and intensity affected vegetation and soil fertility in grasslands. AM-fungal population in rhizopheric soils of palatable grasses would thus provide an indicator of grassland degradation and fertility.

Occurrence and distribution of arbuscular mycorrhizal fungi and microbial flora in the rhizosphere soils of mungbean [vigna radiata (L.) wilczek] and soybean [glycine max (L.) Merr.] from Adilabad, Nizamabad and Karimnagar districts of Andhra Pradesh state, India

Arbuscular Mycorrhizal (AM) fungi are key components of soil microbiota and obviously interact with other microorganisms in the rhizosphere which is the zone of influence of plant roots on microbial populations and other soil constituents. The microbial associates are more prone to general and annual fluctuations besides several abiotic factors such as environment and climatic factors which influence the whole process of AM - microbial interactions. Keeping in view, the importance of AM fungi the present study was undertaken for assessing the AM fungal spore population dynamics in the rhizosphere soil and its colonization, microbial (bacterial and fungal) population distribution in rhizosphere and nonrhizosphere soils as a function of seasonal variation in relation to soil physico-chemical factors associated with two legume crop plants collected from different districts of Andhra Pradesh state, India. AM fungal propagules and species were found to be well distributed varying in number from 12 to 89 spores per 10 gram soil in mungbean and 46 to 90 spores in soybean rhizosphere soils and percent root colonization in mungbean ranged from 36.74 to 90.68% however, in soybean it ranged from 23.58 to 76.92%. The 24 AM fungal species representing 4 genera were isolated, Glomus represented 12 spp. forming predominant genus. The Pearson Correlation coefficient data showed that the microbial population and AM fungal population and species, the degree of root colonization by native AM fungi varied significantly in two legume crop plants and influenced by soil edaphic factors. Significant negative correlation was recorded between root colonization and mean spore density of both the crops indicating that low levels of spore density are associated with high root colonization. The quantity and type of AM propagules also affected the dynamics of root colonization, which were also increased by increase in age of the crop plant.

Improving Activity of Native Arbuscular Mycorrhizal Fungi (AMF) for Mycorrhizal Benefits in Agriculture: Status and Prospect

Agricultural importance and ecological implications of arbuscular mycorrhizal (AM) symbiosis with land plants are well known. AM symbiosis facilitates plant growth through enhancing uptake of several macro- and micro-nutrients of low mobility in soil, like phosphorus, zinc, copper etc. Beside nutritional benefits to plant, AM also contributes to numerous ecological advantages like influencing microbial and chemical environment of the mycorrhizosphere, stabilizing soil aggregates, conferring tolerance (plant) to several abiotic and biotic stresses, bioremediation of soil and supplying protective (antioxidants) nutrient components to human being through agricultural products (food). There are two approaches to exploit arbuscular mycorrhiza for crops: (1) soil introduction of non-native inoculum and (2) exploitation of native AM fungal (AMF) population. The approach of soil introduction of non-native inoculum of selected AMF to field crops suffers from (i) cost intensiveness, (ii) inconsistent competitive performance of introduced inoculum due to lack of adaptability to new ecology and (iii) negative ecological consequences in terms of possible introduction of invasive species as unintended contaminants. Exploitation of native AM fungal (AMF) population of soils, keeping it undisturbed by avoiding faulty agricultural practices, is an alternative approach, now promoted for sound ecological management of crop production, particularly under stressful situations. The approach is based on twin attributes of AM symbiosis – ubiquitous nature and lack of host specificity of AMF. Several prospective avenues of enhancing native AM activities through agronomic manipulations of crop management practices and cropping systems for enhanced response to diverse native AMF population have been discussed in the present article

Status and diversity of arbuscular mycorrhizal fungi and its role in natural regeneration on limestone mined spoils

Singh AK, Jamaluddin (2011) Status and diversity of arbuscular mycorrhizal fungi and its role in natural regeneration on limestone mined spoils. Biodiversitas 12: 107-111. Limestone mined spoils are devoid of adequate population of beneficial microbial flora. Arbuscular mycorrhizal fungi (AMF) are very important constituent of plant- soil-microbe system. In mined spoils the population of AMF is greatly reduced and hence the spoils become very inhospitable for establishment of vegetation. In the present investigation, status of AMF population and its effect on natural regeneration process is studied. It is well known fact that the arbuscular mycorrhizalfungi play very important role in establishment of vegetation in degraded lands. Plantation of seedlings inoculated with arbuscular mycorrhizal fungi provide favorable soil conditions for naturally growing vegetation in the mined overburden spoils. Physico-chemical properties of soil are converted suitable for planted species and thus it allows other species to grow and also provide shade to protect the herbaceous vegetation. Introduction of plant species attracts immigration of other species and if they established, may result into a very distinctive floral cover on disturbed lands. Thus, invasion of native plant species along with planted species may play a significant role in increasing the plant diversity on mined spoils.

Organic management of tilled agricultural soils results in a rapid increase in colonisation potential and spore populations of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal fungi (AM fungi) are important members of the soil microbial community and can potentially offer benefits to low input and organic agricultural systems. While many agricultural practices can adversely affect AM fungi, organic agriculture prohibits some of the most detrimental practices and as a result AM fungal populations may be increased. We examined eleven sites to test the hypothesis that organic management increases AM fungal spore number and colonisation potential in tilled agricultural soils. Samples were taken from a conventional and an organically managed field at each site. AM spores were extracted and onions ( Allium cepa L.) grown on field soils in the glasshouse, with AM colonisation measured to assess colonisation potential. Numbers of AM spores varied from 2 g −1 of soil to 27 g −1. Overall, spore numbers were significantly higher in the organically managed soils, though the number of AM spores was very low in some organically managed soils. Root colonisation varied from 4% to more than 80% and was significantly greater on soils from the organically managed fields. This result was consistent across arable (cereal based), arable/horticultural and horticultural systems. There was no overall difference in soil physicochemical characteristics, except total nitrogen, which was higher in organically managed soils. There was no relationship between the time organic management had been practiced and spore numbers or root colonisation, both responded rapidly to conversion, suggesting that changes in soil physicochemical characteristics are not an important factor. We suggest that the 2-year organic ‘conversion’ period is important for increasing spore number and colonisation potential.

The potential role of arbuscular mycorrhizal fungi in protecting endangered plants and habitats

Ecosystems worldwide are threatened with the extinction of plants and, at the same time, invasion by new species. Plant invasiveness and loss of species can be caused by similar but opposing pressures on the community structures. Arbuscular mycorrhizal fungi (AMF) can have multiple positive effects on plant growth, productivity, health, and stress relief. Many endangered species live in symbiosis with AMF. However, the list of the International Union for Conservation of Nature and Natural Resources (IUCN Red List of Threatened Species) indicates that the mycorrhizal status of most of the threatened species has not been assessed. Rare plants often occur in specialized and also endangered habitats and might utilize specialized or unique AMF. The specificity of any endangered plant to its AMF population has not been investigated. Because most of the current AMF isolates that are available colonize a broad range of plant species, selected inocula could be used to promote growth of endangered plants before the proper and more effective indigenous AMF are characterized. Application of AMF in field sites to protect endangered plants is hardly feasible due to the complexity of plant community structures and the large amount of fungal inocula needed. Endangered plants could, however, be grown as greenhouse cultures together with appropriate fungi, and, at the relevant developmental stage, they could be re-planted into native sites to prevent extinction and to preserve plant community ecology.

Application of mycorrhizae to ornamental horticultural crops:lisianthus (Eustoma grandiflorum) as a test case

Ornamental crops are high-cash crops, grown under greenhouse conditions in semi-arid regions in Israel where a reduction in the native population of arbuscular mycorrhizal fungi (AMF) is expected due to routine soil disinfection. The application of AMF inoculum to the soil has been shown to be effective at improving plant growth and enhancing plant resilience to abiotic and biotic stresses. One of our aims is to introduce mycorrhizal application to ornamental crops, and a test case is presented here for two cultivars of lisianthus (Eustoma grandiflorum), one of the major ornamental crops grown in Israel. Several different methods of AMF application and their effects on growth, yield and vase life were examined in lisianthus grown in two different semi-arid locations in southern Israel. AMF enhanced lisianthus growth and yield, especially when introduced to the growth medium during seeding and to the pit hole during planting. Significantly enhanced growth and yield parameters included flowering stem length (58 ± 0.7 and 65.1 ± 0.7 cm for control and AMF treated, respectively) and number of flowering stems per square meter (73 ± 9 and 106 ± 6 for control and AMF treated, respectively); positive but non-significant effects were recorded on stem weight, number of flowers per stem and vase life of cut flowers. Yield enhancement was recorded under both low and regular phosphorus conditions. Although not significant, higher resilience against two pathogenic fungi was also recorded following AMF inoculation (23 ± 13 and 41 ± 10 surviving plants for control and AMF treated, respectively). Hence, AMF is suggested to be a useful growth amendment for promotion of lisianthus commercial production, and may potentially be applied to additional ornamental crops.

Comparison of organic and conventional stockless arable systems: A multidisciplinary approach to soil quality evaluation

Soil quality in Mediterranean conventional and organic stockless arable systems was assessed by a multidisciplinary approach. At the end of the first cycle of a 5-year crop rotation (2002–2006) in the Mediterranean Arable Systems Comparison Trial (MASCOT) long-term experiment, the effects of organic and conventional management systems were evaluated by using soil chemical, biochemical and biological parameters. Chemical and biochemical parameters linked to soil C cycle, arbuscular mycorrhizal fungi (AMF) and microarthropod communities were analysed according to a comparative approach. Results suggested a higher soil carbon sequestration in the organic respect to the conventional system, as shown by the values of total organic C (9.5 and 7.8 g kg −1, for organic and conventional system, respectively) and potentially mineralisable C (277 and 254 mg kg −1, for organic and conventional system, respectively). AMF population, AMF root colonisation and diversity of microarthropod population were slightly influenced by management system. On the other hand, mites/collembolans ratio was higher in conventionally than in organically managed soil (2.67 and 1.30, respectively), indicating as organic managed soils were more disturbed than conventional ones, probably as the consequence of the more frequent soil tillage performed for mechanical weeds control. The overall results demonstrated that, even in the short-term, the implementation of organically managed stockless systems in Mediterranean areas determined significant changes of some attributes for soil quality evaluation.

Molecular diversity of arbuscular mycorrhizal fungi and their distribution patterns related to host-plants and habitats in a hot and arid ecosystem, southwest China

The communities of arbuscular mycorrhizal fungi (AMF) colonizing the roots of Bothriochloa pertusa, Cajanus cajan and Heteropogon contortus in a fallow land (FL) and an undisturbed land (UL) were characterized. The large subunit rDNA genes of AMF from roots were amplified and cloned. A total of 2353 clones were screened by restriction fragment length polymorphism, and 428 clones were subsequently sequenced. A total of 393 AMF sequences, which were grouped into 100 operational taxonomic units, were obtained. Phylogenetic analysis revealed that the AMF sequences belonged to Glomus, Acaulospora and Scutellospora, and that Glomus was the dominant genus. Of the 393 AMF sequences, 81% were novel. The diversity of AMF colonizing the same plant species was higher in the UL than in the FL, which confirmed strongly from the molecular evidence that soil disturbance reduced AMF population and species richness. The results revealed that AMF communities were significantly different among host-plant species and between the two habitats. The similarity of AMF communities colonizing different plant species within a habitat was higher than that of the same plant species from different habitats. The molecular evidence supported our previous hypothesis based on morphological analyses that AMF communities were more influenced by habitats compared with host preference.

Changes in arbuscular mycorrhizal fungal phenotypes and genotypes in response to plant species identity and phosphorus concentration

* Arbuscular mycorrhizal fungi (AMF) are plant symbionts that improve floristic diversity and ecosystem productivity. Many AMF species are generalists with wide host ranges. Arbuscular mycorrhizal fungi individuals are heterokaryotic, and AMF populations are genetically diverse. Populations of AMF harbor two levels of genetic diversity on which selection can act, namely among individuals and within individuals. Whether environmental factors alter genetic diversity within populations is still unknown. * Here, we measured genetic changes and changes in fitness-related traits of genetically distinct AMF individuals from one field, grown with different concentrations of available phosphate or different host species. * We found significant genotype-by-environment interactions for AMF fitness traits in response to these treatments. Host identity had a strong effect on the fitness of different AMF, unearthing a specificity of response within Glomus intraradices. Arbuscular mycorrhizal fungi individuals grown in novel environments consistently showed a reduced presence of polymorphic genetic markers, providing some evidence for host or phosphate-induced genetic change in AMF. * Given that AMF individuals can form extensive hyphal networks colonizing different hosts simultaneously, contrasting habitats or soil properties may lead to evolution in the population. Local selection may alter the structure of AMF populations and maintain genetic diversity, potentially even within the hyphal network of one fungus.