Distribution of fungal endophyte genotypes in doubly infected host grasses

Abstract

SummaryFungal endophytes of the genus Epichloe È live intercellulary in above ground plant parts of many pooid grasses of the temperate regions. The associations are characterized by single genotype entities since a given host individual normally contains a single endophyte genotype. They can persist over the life span of the hosts. This study examines whether two fungal genotypes can co-exist within a host plant, and how fungal genotypes are distributed within a host in the case of double infections. We selected four Epichloe È bromicola strains that we identi®ed as unique genotypes through RAPD`analysis. Young Bromus erectus plants, derived from callus cultures, were arti®cially inoculated with all possible double-strain mixtures of these fungal genotypes. For identi®cation of fungal genotypes in planta, we designed genotype-speci®c primer pairs that anked size-variable loci in the fungal genomes. Diagnostic PCR revealed that only one fungal genotype was present in most inoculated plants, but double infections were also observed with a frequency of 8% of all infected plants. Subsequent analyses of individual tillers of doubly infected plants revealed that, in a given tiller, both the leaf-blade and the leaf-sheath were colonized with only one endophyte genotype. Tillers without any detectable fungal DNA were also observed. Thus, co-existence of multiple endophyte genotypes within a single host plant is governed by mutual exclusion at the tiller level.

Multiple Infections by the Anther Smut Pathogen Are Frequent and Involve Related Strains

“…Our understanding of parasite virulence evolution would therefore benefit from measures of the frequency of multiple infections and the relatedness among parasite genotypes within hosts in natural populations. Multiple infections have been reported for several plant parasites [9], including a few diseases causing systemic infections [10,11], for which the competition for resources should be stronger because they invade their whole host. Multiple infections have also been reported for a few animal and human parasites [7,12–14].…”

Current Understanding of Endophytes: Their Relevance, Importance, and Industrial Potentials

“…Class I: The balansiaceous fungi share an intimate relationship with their host. They are highly host specific, exhibiting extremely high among host diversity but very low within host diversity, to the extent that different isolates can be associated with individual host units [42,40,43] reported the fungi inhabit the intercellular spaces of aerial plant organs and the extent of fungal colonisation is dependent on the level of stress the host is experiencing. Some Class 1 endophytes have lost the ability to reproduce sexually and are transmitted via host seed [26] and horizontally through the production of epiphyllous conidia [44].…”

“…The isolation of Taxol-producing endophyte Taxomyces anderanae has provided a different approach to find a cheaper and additional product via microorganism fermentation [130]. Taxol has also been found in a amount of unusual genera of fungal endophytes either related or not to yews, such as Taxodium distichum [93] ;Wollemia nobilis [134]., Phyllosticta spinarum [94]; Bartalinia robillardoides [42] ;Pestalotiopsis terminaliae [42] ;Botryodiplodia theobromae [95].…”

Molecular Evidence for Host-Adapted Races of the Fungal Endophyte Epchloë Bromicola After Presumed Host Shifts

“…Although B. erectus and the woodland Bromus species grow in different habitats, they can exist in close proximity at the same location (Table 1), probably within the dispersal range of ascospores. Moreover, doubly infected plants have been observed in B. erectus after experimental inoculations, although coexistence of multiple endophyte genotypes within a single tiller appears to be transient (Wille et al 1999). Parasexual processes have also been suggested to be instrumental for the hybridization and diversification of Neotyphodium species .…”