A vast majority of fungi are composed of microscopic multicellular hyphae (with a
few unicellular species) and show cryptic lifestyles in soil and dead matter and
become noticeable only when developed fruiting bodies spores in as mushrooms or
molds. Fungi are the principal decomposers of organic matter and perform
important role in nutrient cycling in ecosystems (Cooke 2009 ). They establish
parasitic relationships with both plants and animals and are known to cause
widespread damage, to certain agricultural crops (Fisher et al. 2012 ). Endophytic
fungi on the other hand, are symbionts that spend all or part of their life cycle inter
and/or intracellularly colonizing the healthy tissues of a plant without causing any
visible manifestation of symptoms (Tan and Zou 2001 ). The word“endophyte”
originates from Greek,“endo”denoting within, and‘phyte’meaning plant and was
first proposed in 1866 (Jalgaonwala et al. 2011 ; de Bary 1866 ). In addition to fungi,
bacteria including actinobacteria are reported as the major endophytes of plants
(Bandara et al. 2006 ).
9.2 Distribution of Endophytic Fungi
The existence of fungi inside the organs of the asymptomatic plants has been known
since nineteenth century (Guerin 1898 ). Thefirst description of endophytic fungi
was made as far as back in the year 1904, from the seeds ofLolium temulentum
(Freeman 1904 ). Since then fungi have been found from almost every plant species
examined to date (Guo et al. 2008 ). Endophytic fungi have a long life history and
their diversity among plants has been found to be one of the largest (Jalgaonwala
et al. 2011 ).
It is noteworthy that each of the nearly 300,000 existing plant species on Earth is
assumed to host at least one or even several hundred strains of endophytes (Strobel
and Daisy 2003 ). Fungal endophytes are found in a range of host plants growing in
tropical, temperate, boreal forests to extreme arctic, alphine, and xeric environments
(Zhang et al. 2006 ). There are as many as 1.5 million different fungal species on our
planet and about 1 million of them are endophytic fungal species (Strobel and Daisy
2003 ; Radic and Strukelj 2012 ; Hawksworth 2001 ). Among them, only about 0.1
million fungal species including endophytic fungi have been described in the past
century (Radic and Strukelj 2012 ; Ganley et al. 2004 ). Accordingly, fungal endo-
phytes are a group of mainly undescribed organisms that potentially is a rich and
reliable source of genetic diversity.
Endophytic fungi are known to thrive asymptomatically in the tissues of plants
above ground as well as below ground, includingflowers, seeds and ovules, fruits,
stems, leaves, xylem, rachis, bark, tubers, and/or roots (Zhang et al. 2006 ; Kusari
192 P.B. Ratnaweera and E.D. de Silva