“A
little about me and my blog”
Welcome
to my blog. My name is Noor Sairafi and I am a grad student at the Biology
Department at Western Illinois University. My research is about plant-growth
promoting rhizobacteria. I am glad to present in this blog, my grad project in
Mycology class with Dr. Andrea Porras-Alfaro.
I will review PGPR (Plant-Growth Promoting Rhizobacteria), their nteractions
with fungi and plants. I hope you find this informative and useful.
Introduction
Plants do not usually live alone, they are associated with many
microorganisms in a symbiotic relationship (Southworth, 2012). Probably hundreds to millions organisms are
interacting with plants. They could be associated with roots or different parts
of the plant such as leaves and stems. Microorganisms (fungi or bacteria) have
a major impact on plants and the ecosystem. The interactions of fungi and
bacteria help promote the growth of plants and also help build resistance that
protects plants from soil borne diseases (Krings et al, 2012). In addition, some of the interactions between
organisms are deleterious, however, other have a superficial impact on the
overall fitness and growth.
Bacterial
interaction
Plants
growth promoting rhizobacteria (PGPR)
PGPR colonize plant roots and correspond to a complex group of microorganisms
in the soil (Persello-Cartieaux et al, 2003).
Bacteria (PGPR) have been effectively used in this application to
stimulate plant growth or to reduce the damage of the soil borne infections.
Plants-growth promoting rhizobacteria affect plants directly or indirectly. The
direct effects of PGPR include enhanced provision of nutrients and the
production of phytohormones. Indirect effects include aspects of biological
control such as the production of antibiotics and iron-chelating siderophores
and the induction of plant resistance mechanisms (Persello-Cartieaux et al,
2003).
PGPR or rhizobacterial agents
belonging to some bacteria are antagonistic controlled agents affecting plants
and microbes (Labuschage et al, 2010). Rhizobacterial normally trigger plant
systemic acquired resistance (ISR) to help provide protection against microbes
and bacterial inoculation. The ISR serves as a shield against plants diseases
specifically in the roots (Deverndra et al, 2009). PGPR provides ways to supply
nutrients and growth hormones to plants through the rhizosphere, the region of
the soil that directly affects root secretion (Labuschage et al, 2010). Some of the important reasons to use PGPR include the posibility
to improve crop losses related to soil
borne diseases, the reduction of high production costs due to fertilizer costs
and the new global phenomenon toward applying environmentally friendly
production methods (Labuschgen et al, 2010).
Fungal Interaction
Glomus,
Arbusclar mycorrhizal fungi
Description
Glomus
is a genus of arbuscular mycorrrhizal fungi that belong to the phylum Glomeromycota,
which consists of
about 230 species (Oehi et al, 2011). Arbuscular mycorrrhizal fungi are the most ancient and
widespread fungi that are associated with plants roots in symbiotic
relationships.
Arbuscular mycorrihzal fungi are represented in the following genera: Glomus, Acaulospora, Entrophosphora,Gigaspora and Scuterosora.
Traditional classification is based on thesize, shape and wall structure of
spores. Glomeromycota spores are spherical or ovoid, and they form in the end
of the hyphae in one or two layers (Sharma et al, 2008). The spores measure between 30 and 50
micrometers in size and they can germinate in the soil or inside the host
roots.
Glomus has very specificify biological interactions with
plant roots. The host (plants) provides carbon sources and energy in the form
of carbohydrates to the fungus, while the fungus supplies the host (plants)
with the fundamental minerals that it absorbs from the soil (Mohammed, 2010).
The obligated symbiotic relationship between Glomeromycota species and roots is very important and vital for
the fungus and plant survival.
Glomus
produces spores asexually. Spores bear from the tip of the hyphae. It could be
generated within the host root or outside the root in the rhizophere area. When
the spores germinate in the soil they make a special structure (tube)
penetrates the root epidermis allowing the fungi to colonize roots. They will
live inside root cell wall and produce vesicles that function as food storage (Colliton and Cooch, 2010).
Habitat
Arbuscular mycorhizal fungi such as Glomus
are soil fungi. They can be found in different terrestrial and aquatic
habitats. The can also grow in low land tropical rain forest or in high
altitudes (Raghuwanshi and Upadhyay, 2010). Arbuscular mycorrhizal fungi cannot survive without a plant
host in their life cycle. Therefore, it is impossible to grow fungus in
the lab without a host (plants)
(Boundless Microbilogy, 2014).
The Ecological importance of Glomus
and arbuscular mycorrhizal fungi
Arbuscular mycorrhizal fungi make up of mutualistic symbionts on the planet
(St-Arnaud and Vujanovic, 2007). Many reports showed that plants in
association with AMF have shown the significant improvement in growth rate, dry
weight and mineral content following infection, particularly of plants growing
on nutrient-deficient soils (Webster and Weber, 2007). Glomus can penetrate cell wall of the host roots; therefore,
the fungus helps with transferred materials and nutrients such as phosphorus
(P), zinc (ZC) and nitrogen (N) (Smith and Smith, 2011). These nutrients are
essential for plant health and growth. The fungus also benefits from the host
by getting carbon. In this respect, mycorrhizal fungi have a vital role in nutrient
cycling in the ecosystem. The estimation of host plant organic input to AMF
range from 1% to 20% (Colliton
and Cooch, 2010).
Moreover, Glomus have additional
positive relationships with plants such as protecting plants from chemical
products in the soil and pests in the environment. In addition, Glomus enhances and promotes plant
growth and increases their overall fitness. Another significant role of Glomus (AMF) species are their ability
to protect the plant host from soil borne diseases (Colliton and Cooch, 2010).
The
interactions between bacteria and AM fungi
(A) A root tip of Cedrela Odorata colonized
by arbuscular mycorrhizal fungi showing vesicles.
(B) A root of Terminalia Amazonia showing
vesicles and hyphae.
References
1. Peresello-Cartieaux, F., Nussaume, L. and Robaglia, C. (2003). Plant, cell & Environment. Volume 26, Issue 2, Pages 189-199.
2. Southworth, D. (2012). Biocomplexity of Plant-Fungal Interactions. Published by John Wiley& Sons, Inc.
3. Krings, M., Thomas, N. T., and Dotzler, N. (2012). Fungal Endophtes as a driving force in land plant evolution: Evidence from the Fossil Record.
4. Labuschage, N., Pretorius, T., and Idris, A.H. (2010). Plant Growth Promoting Rhizobacteria Agents soil- borneplant disease. Retrieved (Oct 19 2014) https://www.researchgate.net/publication/225358583_Plant_Growth_Promoting_Rhizobacteria_as_Biocontrol_Agents_Against_Soil-Borne_Plant_Diseases
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10. Colliton, R., and Cooch, A. (2010). Glomus. Retrieved (Oct 27 2014) from https://microbewiki.kenyon.edu/index.php/Glomus
11. Boundless Microbiology. (2014). Glomeryomycota Retrieved (Oct 27 2014) from https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/microbial-evolution-phylogeny-and-diversity-8/fungi-113/glomeromycetes-592-11816/
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17. Miransari, M. (2010). Arbuscular Mycorrhiza and soil Microbes. Retrieved (Dec 08 2014) from http://www.planta.cn/forum/files_planta/mycorrhizal_biotechnology_902.pdf
18. Devendra, K., Choudhary., Bhavdish,. N., and Johri. (2009). Interction of Bacillus spp. And plants- with special reference to induced systemic resistance (ISR). (Dec 08 2014) from http://www.sciencedirect.com/science/article/pii/S0944501308000566
19. Artursson, V., Roger, D. F., and Jansson, J.k. (2006). Interctions between arbuscular mycorrhizal fungi and bacteria and their potential for stimulating plant growth. (Dec 10 201 4) http://web.a.ebscohost.com/ehost/pdfviewer/pdfviewer?sid=be14e976-9227-4406-bd60-8765d88f0c43%40sessionmgr4005&vid=5&hid=4106
