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India is located between 8^°- 38^° N and 68^°- 97^ºE and exhibits extreme variation in altitude — from sea level to heights above vegetational limits in the Himalayas (ca 4500 m), and climate — from monsoon- tropical in south to temperate and alpine in the north-western Himalayas and extremely arid to semi-arid in the north-western plains. It is floristically extremely rich with about 33 percent of its botanical wealth (over 15,000 species of higher plants) being endemic. There are about 141 endemic genera distributed over 47 families. Further, of the 4,900 endemic species, larger percentage is localised in the Himalayas (about 2,532 species) than in other regions, namely, the peninsular tract (1,788 species), and the Andaman and Nicobar Islands (185 species). It is also estimated that floristic richness is maximum in the north-eastern region, which holds about 50 percent of India’s total species diversity, i.e., more than 7,000 species, and is considered as the cradle of flowering plants. Of 990 species of orchids, 700 species occur in this region (Nayar, 1989). This, thus, makes the Indian region botanically unique and interesting (Arora, 1991).

Biodiversity is the foundation stone of human survival on the earth. Very appropriately, the theme of the World Food Day celebration, 16 October, 2004 was “Biodiversity for Food Security” Biological diversity is fundamental to agriculture and food production. Scientists have identified so far about 1.4 million of the plant and animal species that exist on earth. A rich variety of cultivated plants and animals serves as the foundation for agricultural biodiversity. Yet people depend on just 14 mammal and bird species for 90 % of their food supply from animals. Just four plant species, namely, wheat, maize, rice and potato provide half of our energy from plants (FAO, 2004).

The place of origin of the crop plant can be found out on the basis of genetic affinities. This would mean to find out the geographical distribution of the wild progenitors of the cultivated plants. If one can locate the distribution of a given progenitor, one can delimit the area in which domestication could have occurred. Vavilov based his judgment on variation patterns in cultivated plants. Information on wild plants in those days was much more fragmentary than what it is today. Even today, genetic and ecological information on wild relatives of several cultivated plants is incomplete and in such cases assessment of a place of origin is difficult to make. However, in most cases required information is available on genetic affinities between wild and tame, on distribution areas and on ecological affinities of the wild progenitors. On this basis it is possible to determine the initial place of origin.

IPGRI founded in 1974 is the world’s largest international institute dedicated solely to the conservation and use of plant genetic resources. It is located at Rome in Italy. The institute is funded by the Consultative Group on International Agricultural Research (CGIR) which is an informal association of 45 public and private sector donors. CGIAR supports a network of 16 International Agricultural Research Centres. The Group was established in 1971. It is cosponsored by the Food and Agriculture Organization (FAO), the World Bank, United Nations Development Programme (UNDP), and the United Nations Environment Programme (UNEP).

Historically, Indian scientists have recognized the importance of conserving plant biodiversity with particular reference to indigenous     and naturalized crops and their wild relatives. Indian scientists have recognized the importance of conserving plant biodiversity as early as 1935 by the ‘Crops and Soil Wing’ of the then Board of Agriculture and Animal Husbandry. Late Dr. B. P. Pal, in his classic paper ‘Search for New genes’ published in 1937 emphasized the importance of germplasm augmentation and utilization in crop improvement programmes. The need was reiterated in a meeting of the Indian Society of Genetics and Plant Breeding in 1941, which inter alia discussed the subject of economic crops. Dr. B. P. Pal, working at the then Imperial (now Indian) Agricultural Research Institute approached the then Imperial (now Indian) Council of Agricultural Research (ICAR) to set-up a unit for assembly of global germplasm under phytosanitary conditions in India. The ICAR scheme for plant introduction started functioning in 1946 under the leadership of late Dr. Harbhajan Singh as the first ‘Operational Scientist’. The scheme was further expanded and strengthened as ‘Plant Introduction and Exploration Organization’ in the Botany Division in 1956 and later established as a separate Division of Plant Introduction in IARI in 1961 headed by Dr. Harbhajan Singh.

Plants are vital part of the world’s biological diversity and essential resource for human well being. Besides meeting our basic food and fibre requirement, many thousands of wild plants have immense economical and cultural importance and potential for providing food, medicine, fuel, clothing and shelter for vast number of people at the global  level. Traditional Chinese medicines use around 5000 plant species and about 7000 different plants are used in traditional medicines in India. Plants play an important role in maintaining basic ecosystem functions essential for survival of animal life. Thus, it is of vital importance to collect and conserve the plant genetic resources on a global basis. It is all the more important as several cases of genetic vulnerability of plants that are grown for food and other uses have been recorded (National Research Council, 1972, Granett et al., 1991). Genetic diversity in the germplasm of crop plants is an effective defense against genetic vulnerability. The genetic diversity is strategically used as modern plant breeding intervention to help increase stability and sustainability of food production using modern cultivars.

The National Bureau of Plant Genetic Resources, commonly known as NBPGR was established by the Indian Council of Agricultural Research (ICAR) in 1976 with its main campus at New Delhi. Being the nodal organization in India it has been given the national mandate to plan, conduct, promote and coordinate all activities concerning plant exploration and collection and also for safe conservation and distribution of both indigenous and introduced genetic variability in crop plants and their wild relatives. The Bureau is also vested with the authority to issue Import Permit and Phytosanitary Certificate and conduct quarantine checks on all seed materials and plant propagules (including transgenic material) introduced from abroad or exported for research purposes.

Allard (1960) defines germplasm as “the sum total of the hereditary  materials in  species” The word germplasm in context of plants is now referred to as plant genetic resources i.e. PGR.PGR is a component of the world’s biological diversity. The term biological diversity is a vast and often undervalued resource. Biological diversity includes every form of life, from the smallest microbe to the largest beast. Biodiversity is the variety and variability of all plants, animals and microorganisms and the ecological complexes of which they are part. The earth’s biodiversity – its ecosystems, species and genes – are the product of over 3000 million years of evolution. Throughout this time, small changes have accumulated in populations, resulting in a multitude of living forms closely adapted to the physical conditions they face and to each other. They supply all our food, much of our raw materials and energy and many of our medicines. Intact eco-systems also play a central role in the functioning of biosphere. Plants are of crucial importance in stabilizing climate, protecting watersheds on soils and maintaining the chemical balance of the earth. When key species are lost, vital ecological services are disrupted (Zedan, 1995).

Current status of researches on VA mycorrhiza and their benefits to the plants carried out by the mycorrhizasts of the country has been described in detail in chapters II to X.

Prior to the establishment of any specific forum, the pace of research on VA mycorrhiza in the country was not of desired level. However, the activities related to research on VA mycorrhiza gained unexpected momemtum when Mycorrhiza network came into exixtence in the year 1989. The network provided not only assistance and guidance of various types to the scientists working on VA mycorrhiza in the country but also offered them periodical platforms to exchange their informations and thoughts on status of researches on VA mycorrhiza and to propose future strategies of research. During the National conferences held in different parts of the country the panel of experts made certain observations regarding future prospects and strategies for research on VA mycorrhiza. They have been mentioned in the present chapter.

The understanding of VAM symbiont and VAM symbiosis is of prime importance in manipulating VAM associations for the welfare of plants. Many contributions have been made worldover in the areas of taxonomy, morphology, anatomy, histology, cytology and genetics of VAM fungi and/or their associations with the plants. However, the share of Indian mycorrhizasts in such contributions is negligible. The following description gives an account of work done by the mycorrhizasts of the country in these areas.

Since a method to cultivate VAM fungi in pure culture is not available as yet, clean and high quality VAM inoculum production is not possible. However, VAM technology is gradually getting a place in agriculture as well as reclamation and afforestation programmes. The inoculum currently being used includes infested fields soils, sievings from such soils, soil and roots of greenhouse plants, or pot culture inoculum derived from surface disinfected spores of a single VAM fungus on a host plant grown in a sterilized growth medium. Attempts are being made to manipulate VAM fungi, rooting media, hosts and fertilizers in order to secure superior quality of inoculum by these methods on a large scale. In addition, other techniques like tissue culture, hydroponic system etc. are also being attempted to cultivate VAM fungi in pure culture. The Indian mycorrhizasts have also attempted to devise and develop improved methods for production and storage of commercial VAM inoculum. The following description gives an account of Indian work related to production and storage of consistently high quality disease free VAM inoculum.

During the last thirty years, there has been a growing appreciation of the impor tance of VAM fungi in improving the plant growth and yield. They have been extensively studied also in India. Considering the potential importance of these organisms in the recovery of disturbed sites and their possible use in land reclamation, researches regarding their relationship to ecosystem recovery have now been initiated also in India.

Large areas of land in the country called wastelands are degraded and lying unutilized due to various constraints. Part of it called culturable, has the potential for the development of vegetation cover. On the other hand, part of it called unculturable, has no potential for the development of vegetation cover. In addition to these natural wastelands, there are large tracts of wastelands created due to human activities such as mining, deforestation etc. Such wastelands are also culturable and a vegetation cover can be developed on them after removing the constraints with some efforts.

Extensive studies have been carried out to explore the possibility of using mycorrhizal model system in inducing suppressions of potential soil-borne pathogens. Its relevance becomes all the more important since most of the soil-borne diseases, by and large, are not easily controlled by conventional methods.

Diseases due to Fungal Pathogens

Most of the studies conducted on the interaction of VAM fungi and fungal pathogens suggest that mycorrhizae decrease the severity of disease, while a few studies suggest that there is either no effect or there is an increase in the severity of disease. It has been pointed out that in view of the fact that VAM fungi deter the severity of disease they may be used as biocontrol agents. Various mechanisms by which VAM could suppress the fungal pathogens have been suggested on the basis of experimental evidences.

Factors which influence the colonization and life cycle of VAM fungi have important bearing on the extent to which they may benefit their host. As we move closer to using mycorrhizal fungi to increase growth and productivity of different plant communities, a thorough understanding of the factors which influence their survival, germination, root colonization an d sporulation will be critical. Seasons, physico-chemical characters of the soil, agronomic practices, plant protection chemicals, pollutants and genotypic characters of the host may affect VAM fungi and their potentiality to colonize and provide benefit to the host. In view of this, the effect of such factors on the VA mycorrhizal symbiosis and its benefit to diverse plant communities has been extensively investigated worldover.

Of the various microorganisms present in and around roots, VAM fungi occupy unique ecological position as they are partly inside and partly outside the host. Their internal phase encounters competition and antagonism from other beneficial symbiotic microbes while their external phase faces competition and antagonism from beneficial non-symbiotic microbes present around the roots. Since they have an ensured source of nutrients from the host, they have comparatively better conditions for their growth and may exert greater effect on plants with other symbiotic and non-symbiotic microbes in and around their roots. It has been pointed out that investigations are needed on the interactions between VAM fungi and these beneficial microbes, and their effect on growth and productivity in plants. A bulk of information has been collected related to this aspect; however, authentic generalization has not been possible as yet. Following description gives an account of the work done by Indian mycorrhizasts on the interactions between VAM fungi and other beneficial symbiotic/non-symbiotic microbes in and around the roots.

Favourable effect of VAM association in plants has been attributed to an increased nutrient uptake by mycorrhizal roots. The transfer of ion from the soil to the roots by mass flow or by diffusion depends on the mobility of that particular ion in the soil. Ions such as NO₃^- ,SO ₄^— and Ca⁺⁺ may move rapidly through the soil to the roots by mass flow, and uptake would be limited by the absorbing capacity of the roots. On the other hand, ions such as H₂PO₄^-, NH₄⁺, Zn⁺⁺ and Cu⁺⁺ are poorly mobile and move to the roots by diffusion, the rate limiting steps is likely to be the movement to the root surface. Under such conditions, it is expected that uptake would be increased if ions could be moved rapidly through extramatrical hyphae of the VAM fungi rather than diffusing slowly through the soil. It is now well established that VA mycorrhizae enhance the uptake of phosphate by the roots but it is likely that they can also assist in the uptake of other ions. The following account provides an information on the findings of Indian mycorrhizasts on the effects of VA mycorrhizal association on nutrient uptake in the plants and its physiological implications.

In recent years the importance of VAM fungi for plant growth in most soils has been accepted and acknowledged by soil chemists, agronomists, horticulturists and farmers. Ever since it was shown that VAM could increase nutrient uptake and water uptake from soil in plants, researchers have been trying to extend and manipulate this effect of mycorrhiza in improving the growth and productivity in various groups of plants. Mycorrhizasts of the country have also explored the possibility of utilizing this tool for improving the performance of various crops including cereals, millets, pulses, vegetables, oilseeds and fruit crops. In addition, they have tried to explore the possibility of utilizing this biotool also for improving the growth of various types of trees including forest trees. Following account is related to the work done by the mycorrhizasts of the country on the effect of VA mycorrhiza on the growth and productivity of various groups of plants including cultivated crops.

VAM fungi are of worldwide distribution. They are present in the soil in form of chlamydospores, zygospores and azygospores and have been recovered from the soils of a variety of habitats e.g. agricultural fields, nutrient deficient soils, sand dunes and deserts, industrial wastes, sodic soils, polluted sites, sewage, eroded sites and others like forests, open woodlands, scrub, savana, heaths, grasslands, anthracite and bituminous coal wastes. There are several reports of VAM fungi from diverse habitats from India.

VA-mycorrhizal associations occur widely throughout the plant kingdom. They have  been reported to be present in Bryophytes, Pteridophytes, Gymnosperms and Angiosperms in nearly all the geographical regions of the world. Most of the agricultural and horticultural crops belonging to diverse families have been shown to form VA-mycorrhizae. Many species of plants of economically important families have been reported to be mycorrhizal. Likewise, many of the plantation crops like coffee, tea, citrus, timber trees, many of the fruit trees and medicinal plants have been shown to form VA-mycorrhiza.

Mycorrhiza research is relatively recent. Although, it was in 1885 that A.B. Frank made reference for the first time to the term “Mycorrhiza”, it took him nine more years to establish the symbiotic relationship between the fungus and its host plant. It took a much longer time to convince the rest of the scientific community of the validity of Frank’s theory. Researches carried out between 1917 to 1950 confirmed that “Mycorrhizal colonization is a beneficial symbiosis between tree and fungus”. It is an unique partnership in nature, where the higher plants share their photosynthates with their fungal partners and provide them shelter, the fungal partners in return provide protection to the root system and assist it in performing its functions especially anchorage and absorption of nutrients / water from soil more efficiently.

The ectomycorrhizal fungi have been in use as a biological tool in improving the performance of forest trees since long. Better performance of forest trees is ensured by making them mycorrhizal, employing efficient strains of ectomycorrhizal fungi.

Peer-reviewed academic journals publish a variety of article types, such as “research articles” that report original research, “reviews” of the literature, and “case reports” of a small number of interesting cases. Each article type has its own specific format, and it is important that you use the appropriate one.