Endophytic Root Colonization by Fusarium Species: Histology, Plant Interactions, and Toxicity

Abstract

Fusarium species have adapted to a wide range of geographical sites, climatic conditions, ecological habitats, and host plants, and species of this polyphyletic genus have been documented to occur worldwide (Backhouse et al. 2001). In spite of the information available on the extremes in geographic distribution and climatic conditions, appropriate data to predict the center of origin(s) or the mode(s) of dispersion of this genus have not been obtained. Much of the information on distribution patterns has been determined from analyses of soil samples, a common habitat, in addition to colonization of many plant species. The diversity of plant species colonized by members of the genus Fusarium is amazing. A recent literature survey determined that Fusarium species have been isolated from plants belonging to the gymnosperms and the monocotyledonous and dicotyledonous angiosperms (Kuldau and Yates 2000). They are the primary incitants of root, stem, and ear rots in many agriculturally important crops. For example, F. verticillioides (= F. moniliforme) is capable of colonizing well over 1,000 plant species, including maize (Zea mays L.), one of the world’s most important food crops. Another species, F. oxysporum, is cosmopolitan; certain strains are usually host specific and pose a severe threat to most of the world’s supply of food crops. Furthermore, species such as F. graminearum, along with F. verticillioides and related species within the Liseola section, are notorious for the production of mycotoxins on wheat, maize, barley, rice and other cereal grains and foodstuffs (Marasas et al. 1984). Consequently, studies on the association of Fusarium species with plants are critical in order to develop control measures for this group of fungi that affects the quality and quantity of the world’s food supply.