Chapter 20 : Microbial Symbioses with Plants

Abstract:

Plant-microbe symbioses are common, ubiquitous, and very varied. The health and vigor of plants is dependent on the multifarious relationships they have with symbiotic microbes. Many of these symbioses are ancient and essential for plants to survive in natural ecosystems, where critical nutrients are often limiting or pathogen populations are highly active. Coevolution of plants and their associated microbial symbioses have been a key driver of the evolutionary process. Recently it has become acknowledged that many plants form such relationships and harbor beneficial microbes within both their root systems and their aerial tissues. As with mycorrhizal fungi, the coevolution of many plants and their associated endosymbionts has resulted in an interdependence that now means that neither partner can flourish alone. This chapter discusses diversity within prokaryotic and eukaryotic symbioses. Many soil fungi form joint organs with plants called mycorrhizas. The easiest to observe are ectomycorrhizas formed on the short roots of most temperate forest trees. A high proportion of these undescribed species will form loose or strong symbiotic relationships with plants. The shift in phylogenetic approaches emphasized in this book has opened a myriad of opportunities for new discoveries. Thus conservation strategies are significant for their retention of plant-microbial symbioses as well as for their intrinsic protection of the plants themselves.