High bicarbonate (HCO3-) content and associated high pH of irrigation water is detrimental to plant growth. Sustain ableagricultural/horticultural production will increasingly have to rely on economically feasible and environmentally sound solutions to the problems associated with high levels of HCO3- in irrigation water. The ability of a mixed Glomus Tulasne & Tulasne species inoculum of arbuscular mycorrhizal fungi (AMF), Glomus ZAC-19 (containing Glomus albidum Walker & Rhodes, Glomus claroideum Schenck & Smith, and Glomus diaphanum Morton & Walker), to enhance plant tolerance to HCO3- was tested on the growth and nutrient uptake of Rosa multiflora Thunb. ex J. Murr. cv. Burr (rose). Arbuscular mycorrhizal colonized and non-inoculated (non-AMF) R. multiflora cv. Burr were treated with 0, 2.5, 5, and 10 mM HCO3-. Increasing HCO3- concentration and associated high pH reduced R. multiflora cv. Burr growth, nutrient uptake, and acid phosphatase activity (ACP), while increasing alkaline phosphatase activity (ALP). Inoculation with AMF enhanced plant tolerance to HCO3- as indicated by greater growth, nutrient uptake, leaf chlorophyll content, higher mycorrhizal inoculation effect (MIE), lower root iron reductase activity, and generally lower soluble and wall-bound ALP activity. While AMF colonization (arbuscules, vesicles, and hyphae formation) was reduced by increasing HCO3- concentration, colonization still occurred at high HCO3- concentration. At 2.5 mM HCO3-, AMF plant growth was comparable to plants at 0 mM HCO3-, further indicating the beneficial effect of AMF for alleviation of HCO3- plant stress.

Arbuscular mycorrhizal (AM) fungi are an important component of agricultural ecosystems, and can directly influence the productivity of these systems. Unfortunately, conventional agricultural practices have been shown to adversely affect AM fungi. The use of more ecologically sustainable agricultural practices such as tree-based intercropping (TBI) may have the potential to reduce the negative impact of agricultural practices on AM fungi. The objectives of this thesis were to determine (1) if trees influence the structuring of AM fungal communities, (2) if TBI systems support a more diverse AM fungal community compared to conventional monocropping (CM) systems, and (3) if differences in AM fungal richness and composition between the two cropping systems have a functional effect on the growth of crops. Molecular analysis of the AM fungal community in the TBI system revealed 17 phylotypes that all belonged to the family Glomeraceae. Differences in richness and composition among the treatments indicated that trees had an effect on the structuring of AM fungal communities. Intercropping alleys adjacent to white ash and poplar tree rows had a significantly (P < 0.05) richer and different AM fungal community compared to intercropping alleys adjacent to Norway spruce tree rows. When comparing TBI and CM systems, AM fungal abundance was not significantly (P > 0.05) different between the two cropping systems. However, differences in both richness and community composition of AM fungi were observed between the two cropping systems. The TBI system had a significantly higher AM fungal richness and contained several taxa not found in the CM system. Controlled greenhouse experiments revealed that differences in AM fungal richness and community composition between the TBI and CM systems had no functional effect on the growth of three crops (i.e. barley, canola, and soybean). The similar growth response of crops to AM fungi from the two cropping systems may be due to the lack of functional complementarity among the AM fungi. Overall, the TBI system had a more diverse AM fungal community compared to the CM system and trees appear to be a significant factor in the structuring of these communities.

Arbuscular mycorrhizal fungi (AMF) are widespread soil dwelling microorganisms that associate with plant hosts. AMF receive carbon from the host as a result of the mutualism, while the plant’s ability to acquire nutrients is enhanced by AMF. Additionally, AMF benefit their host in the form of pathogen protection. While it is known that increased AMF species richness positively correlates with aboveground plant productivity, the relationship between AMF diversity and pathogen protection is not well understood. In a growth chamber study, the plant host Leucanthemum vulgare, a non-native plant species in North America, was introduced to all combinations of three AMF species either in the presence or absence of the plant root pathogen Rhizoctonia solani. In the presence of the pathogen, the plant host increased its dependence on the AMF symbiosis. However, the richest AMF species assemblage did not provide the greatest pathogen protection. Understanding how diverse groups of AMF protect plants from pathogen attack provides insight into how plant communities are formed and structured. / NSERC

No description available.

It may be possible to tailor crop management to encourage diverse soil microbial communities and beneficial microorganisms, and produce high quality food products. Studies were carried out in 2005-2007 to evaluate the impact of spring wheat (Triticum aestivum L.) cultivar choice and crop polycultures on soil microbial communities in organic and conventional systems, and subsequent wheat quality. Five wheat cultivars were grown organically and conventionally to evaluate grain breadmaking quality and micronutrient content and their impact on the soil microbial community. Organic grain yields were roughly half of conventional yields, but quality levels were all acceptable for Canadian Western Hard Red Spring wheat. Measured soil (0-15 cm) microbial profiles (by phospholipid fatty acid analysis) differed between the two management systems, and amongst cultivars in the conventional system. The most recent cultivar in the study, AC Superb, exhibited the highest levels of fungi suggesting that breeding efforts in conventionally managed environments may have resulted in cultivating mycorrhizal dependence in that environment. In general, many of the studied grain micronutrients were greater in the organically grown wheat system, possibly due in part to decreased grain yield and smaller grain size. Maximizing grain micronutrient content through wheat cultivar choice was dependent on management system. The presence of fungi biomarkers appears to have improved uptake of Mn and Cu. Monocultures and polycultures of common annual crops were grown organically and conventionally in 2006-2007. Intercrops exhibited an ability to overyield in an organic system, largely through weed suppression, but intercrops also overyielded in a conventional system where weeds were controlled through herbicides. As intercrop complexity decreased, the instances of improved weed suppression declined. Management systems and wheat cultivars can alter the composition of the soil microbial community. Annual crop polycultures did not alter soil microbial communities in this study, but showed evidence of agronomic benefits in both organic and conventional systems. / Plant Science

Made available in DSpace on 2014-06-11T19:35:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-23Bitstream added on 2014-06-13T20:26:13Z : No. of bitstreams: 1 scabora_mh_dr_ilha.pdf: 1356809 bytes, checksum: 1945cc637998450974f2829ff790aafa (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Com a construção da barragem da Usina Hidrelétrica de Ilha Solteira (SP), ocorreu a degradação do solo, expondo o subsolo e dando origem às áreas de empréstimo. Com o objetivo de melhor compreender a associação entre fungos micorrízicos arbusculares (FMA) e espécies arbóreas na recuperação de áreas degradadas, foram avaliados a produção de esporos e a diversificação das comunidades de FMA nativos após inoculação em dez espécies arbóreas nativas do cerrado, implantadas em duas áreas, uma vegetada com pastagem e outra com subsolo exposto, bem como avaliar a ocupação destas por espécies herbáceas co-ocorrentes e as alterações da fertilidade do solo ao longo de quatro anos de revegetação. O experimento foi conduzido na Fazenda de Ensino, Pesquisa e Extensão da Universidade Estadual Paulista, Faculdade de Engenharia, Campus de Ilha Solteira, localizada no município de Selvíria-MS. O delineamento experimental foi o fatorial 2x4x10 em blocos, ou seja, duas áreas (pastagem e subsolo exposto), quatro anos e 10 espécies arbóreas, com quatro repetições, sendo cada repetição constituída por cinco plantas. Após a instalação do experimento, amostras do solo e do subsolo foram coletadas na profundidade de 0- 0,10 cm, no 1, 2, 3 e 4o ano e utilizadas para avaliação das características químicas e das comunidades de FMA. O número de esporos, a riqueza de espécies, a diversidade e a equabilidade foram comparados e relacionados com as propriedades químicas do solo e com a ocupação das espécies herbáceas co-ocorrentes. Houve incrementos nos teores de matéria orgânica ao longo do anos na área de subsolo. Na diversificação de FMA foram identificadas 52 espécies, das quais 19 pertencem ao gênero Glomus, 14 pertencem à Acaulospora, 10 à Scutellospora, seis à Gigaspora... / Due the construction of the Ilha Solteira Hydroelectric plant (SP), soil degradation has occurred, exposing the subsoil and giving rise to the “soil landing” areas. In order to better understand the association between arbuscular mycorrhizal fungi (AMF) and tree species in the recovery of degraded areas, were assessed the spores production and diversification of native communities of AMF by evaluating ten species of cerrado native tree after the inoculation, introduced in two areas, one vegetated with grass and the other with exposed subsoil, as well as, by evaluating the occupation by the co-occurring plant species and changes in soil fertility, over the four years of restoration. The experiment was conducted at the Education, Research and Extension Farm of the UNESP-Universidade Estadual Paulista, Engineering Faculty, Ilha Solteira Campus, located in the city of Selvíria-MS. The experimental design was a complete randomized block design in a 2 x 4 x 10 factorial, i.e., two areas (pasture and subsoil exposed), four years and 10 tree species, with four replicates, each replicate consisting of five plants. The soil and subsoil, sampled at the depth of 0 to 0.10 m, after 12, 24, 36 and 48 months after the experiment installation, were used to evaluate the soil chemical and AMF communities characteristics... (Complete abstract click electronic access below)

Resumo: Com a construção da barragem da Usina Hidrelétrica de Ilha Solteira (SP), ocorreu a degradação do solo, expondo o subsolo e dando origem às áreas de empréstimo. Com o objetivo de melhor compreender a associação entre fungos micorrízicos arbusculares (FMA) e espécies arbóreas na recuperação de áreas degradadas, foram avaliados a produção de esporos e a diversificação das comunidades de FMA nativos após inoculação em dez espécies arbóreas nativas do cerrado, implantadas em duas áreas, uma vegetada com pastagem e outra com subsolo exposto, bem como avaliar a ocupação destas por espécies herbáceas co-ocorrentes e as alterações da fertilidade do solo ao longo de quatro anos de revegetação. O experimento foi conduzido na Fazenda de Ensino, Pesquisa e Extensão da Universidade Estadual Paulista, Faculdade de Engenharia, Campus de Ilha Solteira, localizada no município de Selvíria-MS. O delineamento experimental foi o fatorial 2x4x10 em blocos, ou seja, duas áreas (pastagem e subsolo exposto), quatro anos e 10 espécies arbóreas, com quatro repetições, sendo cada repetição constituída por cinco plantas. Após a instalação do experimento, amostras do solo e do subsolo foram coletadas na profundidade de 0- 0,10 cm, no 1, 2, 3 e 4o ano e utilizadas para avaliação das características químicas e das comunidades de FMA. O número de esporos, a riqueza de espécies, a diversidade e a equabilidade foram comparados e relacionados com as propriedades químicas do solo e com a ocupação das espécies herbáceas co-ocorrentes. Houve incrementos nos teores de matéria orgânica ao longo do anos na área de subsolo. Na diversificação de FMA foram identificadas 52 espécies, das quais 19 pertencem ao gênero Glomus, 14 pertencem à Acaulospora, 10 à Scutellospora, seis à Gigaspora... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due the construction of the Ilha Solteira Hydroelectric plant (SP), soil degradation has occurred, exposing the subsoil and giving rise to the "soil landing" areas. In order to better understand the association between arbuscular mycorrhizal fungi (AMF) and tree species in the recovery of degraded areas, were assessed the spores production and diversification of native communities of AMF by evaluating ten species of cerrado native tree after the inoculation, introduced in two areas, one vegetated with grass and the other with exposed subsoil, as well as, by evaluating the occupation by the co-occurring plant species and changes in soil fertility, over the four years of restoration. The experiment was conducted at the Education, Research and Extension Farm of the UNESP-Universidade Estadual Paulista, Engineering Faculty, Ilha Solteira Campus, located in the city of Selvíria-MS. The experimental design was a complete randomized block design in a 2 x 4 x 10 factorial, i.e., two areas (pasture and subsoil exposed), four years and 10 tree species, with four replicates, each replicate consisting of five plants. The soil and subsoil, sampled at the depth of 0 to 0.10 m, after 12, 24, 36 and 48 months after the experiment installation, were used to evaluate the soil chemical and AMF communities characteristics... (Complete abstract click electronic access below) / Orientador: Ana Maria Rodrigues Cassiolato / Coorientador: Rosilaine Carrenho / Banca: Katia Luciene Maltoni / Banca: Franscisco Maximino Fernandes / Banca: Daniela Tiago da Silva Campos / banca: Waldeamar Zangaro Filho / Doutor

Existing evidence suggested that nursery inoculation with Trichoderma harzianum and arbuscular mycorrhizal fungi (AMF) could reduce deleterious effects of biotic and abiotic stresses and improve seedling quality, fruit yield and quality of tomato (Solanum lycopersicum L.). However, studies of their combined inoculation on seedling growth, fruit yield and quality of tomato plants are not well-documented. Experiments were carried out to investigate the combined effect of T. harzianum and AMF on tomato crop performance under various conditions. When combined with a T. harzianum and AMF mixture, seaweed extract from Ecklonia maxiama inhibited AMF root colonisation of tomato seedlings. Treating seedlings with a mixture of T. harzianum and AMF reduced the incidence of Verticillium wilt in tomato grown in a nethouse at early season, with negligible effect on fruit yield. Further investigations were initiated to find out whether T. harzianum and AMF were efficient when applied as a mixture or alone, at different inoculation times. Co-inoculation with T. harzianum and AMF (Glomus mosseae) improved seedling growth and development, except when both fungi were simultaneously applied two weeks after sowing. When the seedlings were allowed to grow up until full harvest in a greenhouse, both fungal inoculants increased total yield and marketable yield, but these increases were not significant. Furthermore, inoculation with AMF increased the percentage of extra-large fruit. Field experiments conducted under commercial tomato production confirmed greenhouse studies. Inoculation of tomato with T. harzianum and AMF, either alone or in combination increased early fruit yield (four first harvesting weeks). Throughout the studies, percentage AMF root colonisation in seedlings and plants remained low, despite nursery inoculation. Field experiments investigated the effects of AMF-inoculated transplants combined with biochar-amended soils on AMF root colonisation and their resultant effects on overall crop performance and microbial community structure. Biochar had no effect on AMF root colonisation, and also when combined with AMF, it had no influence on tomato productivity. Interestingly, biochar altered the fungal community while AMF might have influenced the bacterial community such as plant-growth promoting rhizobacteria, which are associated with improved plant growth, nutrient uptake and disease control in the rhizosphere. These benefits could contribute to improved yield and fruit quality. In conclusion, although the results were variable, there was a clear indication that T. harzianum and AMF can play an important role in tomato production. / Thesis (PhD)--University of Pretoria, 2012. / Plant Production and Soil Science / unrestricted

Arbuscular mycorrhizal (AM) fungi are obligate biotrophs that formsymbiosis with plants by colonizing their roots. The fungus supplies thehost plant with various nutrients, including phosphorus. Phosphorus iscrucial for the development of plants and is hard to acquire in soilsince it can be scarce and has a slow motility. The fungus utilizes itslong hyphal threads to contact more soil to obtain phosphorus andtransport it back to the plant. It does so with its use of differentphosphorus transporters (PTs) located in its membranes. Here we havedone a phylogenetic analysis of different PTs from a variety of fungifrom different phyla together with plants and new sequence data from AMfungi. In total, 955 genomes were screened, 26 of which belong to AMfungi. This work resulted in a database of 1351 PT sequences, 907 fromfungi (243 from AM) and 444 from plants, and two phylogenetic trees tovisualize the data. One phylogeny was made of the branch of the PT Pho87which was selected for building a Hidden Markov model, which canfacilitate future searches of PTs.

Arbuscular mycorrhizal fungi (AMF) are a group of root obligate symbionts that are part of the fungal sub-phylum Glomeromycotina, which provide water, nutrients, and pathogen protection to about 80% of land plants in exchange for their photosynthetic products. AMF thus act as “biofertilizers”, have a profound effect and influence on the biodiversity of plants, and play a major role in life on land. From an evolutionary point of view, AMF are a puzzling group of organisms, thought to have propagated for over 400 million years without sexual reproduction, a rarity among eukaryotes. However, this assumption is largely based on the absence of definitive observations of sexual reproduction through microscopic tools. One clue into the sexual activity of AMF is evidence of a dikaryotic-like genome organization in their multi-nucleated mycelium. The recent identification of multi-allelic mating-type loci (MAT locus) potentially places AMF among other heterothallic or bipolar species, who’s mating compatibility is determined by their MAT locus. The presence of a hidden sexual cycle in AMF is still a possibility, and recent findings on the meiotic gene content of AMF suggests an alternative narrative to how these fungi have escaped extinction for so long. Seven meiosis-specific genes (MSG) were found to exist in AMF, indicating that these fungi are likely undergoing a cryptic sexual cycle. The main goal of this research is to determine if/when MSG are expressed in an in-vitro model of AMF. To build onto this research, we established crossings between isolates with hypothetically compatible mating types, in order to determine if fusion of their hyphae can trigger the expression of MSG. Together, these experiments will assess expression at varying stages of the putative cycle of sexual reproduction and give further insight into the elusive sexual life of AMF.