Molecular Microbiology Research 2024, Vol.14, No.2, 99-108 http://microbescipublisher.com/index.php/mmr 100 2 Overview of Endophytes 2.1 Definition and types of endophytes Endophytes are microorganisms, primarily fungi and bacteria, that live inside plant tissues without causing apparent harm to their host. They can be found in various plant parts, including leaves, stems, roots, and seeds. Endophytes are broadly categorized into two main types based on their phylogeny and life history traits: clavicipitaceous (C) and nonclavicipitaceous (NC) endophytes. Clavicipitaceous endophytes are typically found in grasses and are known for their mutualistic relationships, often producing alkaloids that protect the host plant from herbivores and pathogens. Nonclavicipitaceous endophytes, on the other hand, are more diverse and can be found in a wide range of plant species, contributing to plant health through various mechanisms such as stress tolerance and growth promotion (Rodriguez et al., 2009; Caradus and Johnson, 2020). 2.2 Endophyte-host relationships The relationship between endophytes and their host plants spans a continuum from mutualism to antagonism. Mutualistic endophytes can enhance the fitness of their host plants by improving stress tolerance, promoting growth, and providing protection against pests and pathogens. For instance, Epichloë endophytes in grasses produce alkaloids that deter herbivores and protect the plant from diseases, making them essential for resilient high-performing pastures. Conversely, some endophytes can become pathogenic under certain conditions, highlighting the complexity of these interactions (Khare et al., 2018; Grabka et al., 2022). The endophyte-host relationship is influenced by various factors, including the specific endophyte species, the host plant species, and environmental conditions. 2.3 Role of endophytes in plant health Endophytes play a crucial role in enhancing plant health by conferring tolerance to abiotic and biotic stresses, promoting growth, and protecting against pathogens. For example, endophytes from wild cereals have been shown to improve wheat performance under drought conditions by altering the plant's physiological responses to water stress, reducing stress damage markers, and modifying metabolite accumulation (Llorens et al., 2019). Additionally, endophytes can produce bioactive compounds that suppress pathogens, solubilize phosphate, and contribute assimilable nitrogen to plants, thereby enhancing plant growth and yield (Ek-Ramos et al., 2019). The diversity of endophytes in wild wheat ancestors, such as Triticum dicoccoides and Aegilops sharonensis, suggests that these plants harbor a wealth of beneficial endophytes that could be harnessed for agricultural improvement (Ofek-Lalzar et al., 2016). Understanding the multifaceted interactions between endophytes and their host plants is essential for developing sustainable agricultural practices that leverage these natural symbionts (Kaul et al., 2016). 3 Endophyte Diversity in Wild Wheat 3.1 Methods for assessing endophyte diversity The assessment of endophyte diversity in wild wheat involves a combination of cultivation-dependent and cultivation-independent methods. Cultivation-dependent methods include isolating endophytes from plant tissues and analyzing their genetic material. For instance, in the study of endophyte communities in Triticum dicoccoides and Aegilops sharonensis, both cultivation and cultivation-independent methods were used, resulting in the identification of 67 operational taxonomic units (OTUs) from single cultures. Similarly, the diversity of endophytic fungi in wheat and its wild relatives was characterized using next-generation sequencing, which identified a total of 1 666 taxa. Cultivation-independent methods, such as metabarcoding and next-generation sequencing, are crucial for capturing a broader spectrum of endophytes, including those that are difficult to culture. For example, ITS1 metabarcoding was employed to study the fungal wheat microbiome, revealing significant influences of host genotype, tissue type, and abiotic factors on fungal communities (Latz et al., 2020). Additionally, the use of
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