Cfiaptm-1. Introduction

Transcription

1 Cfiaptm-1

2 "Life in Earth is crucial for life on Earth". Soil is a dynamic living matrix that is an essential part of the terrestrial ecosystem. The word 'soil' is derived from of Latin word "Solum" meaning earthy material in which plants grow. The study of soil is called as "Soil Science", "Pedology" or "Edaphology" (Shukla and Chandel, 2001). Soil is the outer covering of the earth, which consists of loosely arranged layers of material composed of inorganic and organic constituents in different stages of organization (Rao, 2003). It is a unique habitat, which includes numbers of plant, animals and microorganisms. Every handful of soil is likely to contain billions of microorganisms (microflora and microfauna). The number and kind of microorganisms present in soil depend on many environmental factors, such as ph, temperature, moisture, aeration, organic matter and nutrients available. They give mechanical and nutritional support to higher plants by formation of soil, fixing atmospheric nitrogen and degrading complex organic matter into simple compounds (Kelmani, 1998). Microbial diversity is a significant component of overall biological diversity and has a major role in maintaining human health and sustaining healthy environment. Biological processes in the environment either directly or indirectly involve microorganisms but the potential benefits of regulating, optimizing exploiting microbial activity have not explored (Kumar, 1999).

3 The microbes are distributed in the plant parts such as leaves, stem, flower, buds, fruit and roots (enodophytes). These microbes are also found on the surface of roots (rhizoplane), as well as in soil around roots (rhizosphere). 'Rhizosphere' is narrow zone surrounding living plant roots, which is characterized by the presence of root exudates and supports greater microbial activity than the soil away from the plant root. About 5 to 6 inches distance away from the roots is the 'non-rhizosphere'. Microorganisms growing under the influence of root are quantitatively and qualitatively different from those inhabiting remote from this influence in the soil environment. The products of microbial metabolism that are released into the soil influence the growth of the plant. The microbial populations are more in rhizosphere soil and differ from plant to plant (Pelczar et ah, 2006). The microorganism that inhabits the soil and exhibit different types of interactions. Soil microorganisms are broadly classified into bacteria, actinomycetes, fungi, algae, nematodes and protozoa. Different microbial population per gram of soil in bacteria is 10 8 to cells, fungi is 2 x 10 4 to lxlo 6 organisms, actinomycetes is 10 to 10 organisms, cyanobacteria and other algae is 100 to 10,000 organisms, protozoans is 10 3 organisms (Dubey and Maheshwari, 2004). The habitats of fungi are quite diverse some are aquatic and some other marine, but thousands of different species of fungi harbour the soil and on dead plant matter. They dominate the microbial population of most forest soil because other organisms decline in number in acidic soils (Frederick and Louis, 1993). 2

4 Fungi is a "nucleated spore bearing achlorophyllus organisms which generally reproduce sexually and asexually, and whose filamentous, branched, somatic structure are typically surrounded by cell walls containing cellulose or chitin or both" (Alexopoulos and Mims, 1952). The fungi in the soil are significant for the following reasons : They are very active in decomposing the complex organic constituents of plant tissue such as cellulose, lignin and pectin. The accumulation of mold mycelia improves the physical nature of soil by increasing porous crumbling structure. The mycelium penetrates through the soil forming a network that entangles the small particles and this improves the soil aeration and water movements in the soil. They are also significant in forming humus soil fertility. Economically fungi are very important because of their both harmful as well as beneficial effects. Fungi are not only beautiful but play a significant role. These fungi are beneficial to agricultural and industrial fields. They have long been exploited as food, in processing food, and brewing and fermentation. They have yielded an increasing range of valuable products, including antibiotics, vitamins and enzymes. Recently, with the advent of genetic manipulated fungi are being produced hormone and proteins (Gupta and Mukerji, 2001). 3

5 In agricultural fields some fungi are used as biocontrol to control the diseases of crops and as biofertilizer to enhance growth of plant. The harmful activities OF microorganisms as saprotrophs include damage to timber, fuel, wood and manufactured foods. As parasites they cause heavy crop losses and diseases of man and animals (Gupta and Mukerji, 2001). Diversity of fungal species supported by the forest soil, due to the decomposition of plant species litter with varied type and proportions of complex polymeric components, such as cellulose, hemicelluloses and lignin contributing the major requirements (Banakar, 2012). Yet only limited information was currently available on most of fungal species. Current estimate of species number for fungi vary significantly between the authors (Table 1). The hypothesis by Hawksworth (1991, 2001) that there may be 1.5 million fungal species, of which only about 80,000 described, implies that a large number still remains to be described. Less than 5% of the fungi have been described. Rossman (1994) invited a number of mycologists to develop a putative estimate of diversity for major taxonomic group of fungi. This exercise resulted in a total estimated of over 1 million species of true fungi, with current knowledge of individual groups ranging from less than 1% hyphomycetes to 67% for lichenized fungi (Table 2). 4

6 Table 1. Current estimate of fungal species diversity (Hawksworth, 2001; Mueller and Schmit, 2007) SI. No. Author Year In millions 1. Pascoe Hawksworth Hammond Smith and Wallor 1992 l(on tropical plants alone) 5. Hywel-Jones (insect fungi awaiting discovery only) 6. Rossman Dreyfuss and chapel (endophytes alone) 8. Hammond Shivas and Hyde (plants pathogens alone) 10. Aptroot (world ascomycetes alone) 11. Cannon Guzman (for Mexico only) 13. Frolich and Hyde (very conservative) 14. May Arnold et al Crous et al (for South Africa only) This lack of basic information on fungal taxonomic diversity has implication in understanding of many aspects of evolutionary biology, e.g., phylogenetic analysis. The role that biodiversity plays in providing resilience to perturbations, co-evolutionary relationships and processes, interpretations of biogeographic patterns, natural products screening programs (Mueller et al., 2004; Hawksworth and Mueller, 2005). A stable and an accepted estimate of taxonomic 5

7 diversity for fungi is necessary to have them included in considerations of biodiversity conservation, planning and management, and related subjects. Table 2. Major groups of fungi and estimated world species number as compiled by Rossman (1994) compared to number reported in Hawksworth et al (1995) Group Estimated species Dictionary of fungi (2005) Percent known Aphyllophorales s lat. 3, Macrolichens 13, Agaricales s lat. 80,000 6, Dematiaceous and aquatic hypomycetes 80, Uredinales 50,000 7, Hypocreales xylariales 50,000 1, Ustilaginales 15, Gasteromycetes 10, Erysiphales 10, Jelly fish s lat. 5, Pezizales 3,000 1, Myxomycetes 15, Endomycetes (true yeasts) 1, Non dematiaceous hypomycetes 2,00,000 11, Coelomycetes 2,00,000 9, Other perithecioid ascomycetes 1,00,000 7, Helotiales 70,000 2,036 3 Insect specific fungi 50, Crustose lichens Mucorales Oomycetes Chytridiomycetes Endogonales 1, Total 1,028,500 68,

8 Researchers have point out that the biodiversity depends on two assumptions and if either of these assumption turns false, then the ratio estimate will be unreliable, (i) The ratio of fungal to plant species does not change when examined at broader spatial scales, (ii) The ratio of fungal to plant species is constant regardless of the diversity of the plant community. For these two assumptions to turn true, the following are necessary: (a) Fungal species diversity and plant species diversity must be positively correlated over a wide range of scales, (b) Fungal and plant species must have similar average range sizes (Mueller and Schmit, 2007). That is, data on biogeographic distribution, levels of endemism, and host specificity must be taken into account when developing estimates of global fungal diversity. The number of fungal genera reported from around the world and from India between 1905 and 1995, are shown in (Table 3) '(Manoharachary et al, 2005). About 205 new genera have been described from India in the last 50 years of which 32% were by Suramanian, University of Madras. Approximately 27,000 fungal species were reported to colonized diversified in the last 70 years (Manoharachary, 2001) added 12 new genera, 60 new species and 500 new additions to fungi of India (Manoharachary et al., 2005). The recognition that many new taxa are yet to be found is of fundamental importance to plant pathologists, agronomists and plant regulatory officials, all of whom continue to encounter disease caused by previously unknown or 7

9 understudied fungi. Unexplored habitats with their arsenal of known are also of interest to these searching for novel organisms for use in biological control or for their pharmaceutical attributes (Hawksworth and Rossman, 1997). Table 3. Number of fungal genera reported on globe and India, Phyla Myxomycotina Mastigomycotina Zygomycitina Ascomycotina Basidiomycotina Deuteromycotina Total World fungi , ,100 7,270 Indian fungi Fungi are among the most important organisms in the globe, only limited and incomplete information is currently available for most species and current estimates of species numbers for fungi differ significantly. This lack of basic information on taxonomic diversity has significant implications for many aspects of evolutionary biology. While 1.5 million estimated fungal species is commonly used, researchers have questioned the validity of this estimate. Data on biogeographic distributions, levels of endemism, and host specificity must be taken into account when developing estimates of global fungal diversity. 8

10 Plant growth promoting fungi Plant growth promoting fungi which are nonpathogenic soil inhibiting saprophytes have been reported to be beneficial to several crop plants not only by promoting their growth but also by protecting them from diseases. Although several studies have been conducted on plant growth promoting rhizobacteria. Only few worker have dealt with plant growth promoting fungi enhance the growth of variety of crop plants (Koike et al, 2001). The Plant growth promoting fungi belong to the genera Fusarium, Penicillium, Phoma, Trichodema, Mucor and sterial fungi (Hyakumachi, 1994). Thichodera and Rhizoctonia have been found to promote plant growth and as to suppress plant pathogen (Sneh et al, 1986; Baker, 1991). Rhizobacteria species, Trichoderma and Gliocladium and certain sterial fungal isolates have been shown to promote plant growth (Chang et al, 1986; Shivanna, 1996). Plant growth promoting fungi isolated from the rhizospheric region of plants enhance the growth of crop plants and suppress diseases effectively but also induce systemic resistance (Meera et al, 1995; Jain and Gupta, 2002; Dewan and Sivasithamparam, 1989; Meera et al, 1994; Yadav et al, 2001). Endophytes are also promoting the growth of crop plants (Shankar, 2008). Arbuscular mycorrhizal fungi (AMF), are integral part of the living plant system in a great majority of terrestrial these fungi play pivotal and indispensable role in upgrading plant growth, vigour and providing a natural defense against invaders (Singh et al, 2000). 9

11 References Windham et al. (1986) Windham et al. (1986) Change^/. (1986) Changed/. (1986) Hyakumachi (1994) Windham et al. (1986) Hyakumachi (1994) Windham et al. (1986) Hyakumachi (1994) Windham et al. (1986) Dewan and Sivasithamparam (1989) Dewan and Sivasithamparam (1989) Speakman and Kruger (1984) Speakman and Kruger (1984) Narita and Suzui (1991) Dewan and Sivasithamparam (1989) Sneh etal. (1986) Sneh etal. (1986) Sneh et al. (1986) Sneh et al. (1986) Sneh et al. (1986) Sneh et al. (1986) Lindsey and Baker (1967) Lindsey and Baker (1967) Shivannaefa/. (1994) Shivannaetal. (1994) Shivannae/a/. (1994) Table 4. Growth promotion on plants treated with plant growth-promoting fungi (PGPF) Fungus Crop Growth promoting effect 71 harzianum times 7.9 times T. koningii T. ciride Sterile red fungus Sterile black fungus Sterile dark fungus R. solani AG4 R. nigricans F. roseum Phoma sp. Tobacco Red pepper Periwinkle Bentgrass Tobacco Reygrass Wheat Rye Wheat Rye Wheat Ryegrass Radish Carrot Lettuce Cotton Wheat Bean 9.1 times times 5.1 times 2.7 times 4.4 times 10-60% 10-60% 40% 40% 30% % % % % 58.4% 28.7% 42% 54% 46-77% 23-25% 11-52% Increased dry weight, enhanced germination Increased dry weight, enhanced germination Enhanced germination Enhanced germination Increased dry weight and plant height Increased dry weight, enhanced germination Increased dry weight Increased dry weight, enhanced germination Increased dry weight and plant height Increased plant height Increased shoot fresh weight Increased shoot fresh weight % Increased shoot fresh weight Increased shoot fresh weight Increased shoot fresh weight Increased shoot fresh weight Increased yield Number of grain Increased yield (Green house) Increased yield (Field) 10