Resistance to rust fungi in Lolium perenne depends on within-species variation and performance of the host species in grasslands of different plant diversity

Abstract

The hypothesis that plant species diversity and genetic variation of the host species decrease the severity of plant diseases is supported by studies of agricultural systems, but experimental evidence from more complex systems is scarce. In an experiment with grassland communities of varying species richness (1, 2, 4, 8, 16, and 60 species) and functional group richness (1, 2, 3, and 4 functional groups), we used different cultivars of Lolium perenne (perennial ryegrass) to study effects of biodiversity and cultivar identity on the occurrence and severity of foliar fungal diseases caused by Puccinia coronata (crown rust) and P. graminis (stem rust). Cultivar monocultures of perennial ryegrass revealed strong differences in pathogen susceptibility among these cultivars. Disease intensity caused by both rust fungi decreased significantly with growing species richness of species mixtures. The response to the diversity gradient was related to the decreased density and size of the host individuals with increasing species richness. The occurrence of other grass species known to be possible hosts of the pathogens in the experimental mixtures did not promote disease intensity in L. perenne, indicating that there was a high host specificity of pathogen strains. Differences in pathogen susceptibility among perennial ryegrass cultivars persisted independent of diversity treatment, host density and host individual size, but resulted in a cultivar-specific pattern of changes in pathogen infestation across the species-richness gradient. Our study provided evidence that within-species variation in pathogen susceptibility and competitive interactions of the host species with the environment, as caused by species diversity treatments, are key determinants of the occurrence and severity of fungal diseases.

Experimental Evidence for Reduced Rodent Diversity Causing Increased Hantavirus Prevalence

“…Strikingly similar results have been found in experimental studies in which fungal pathogen prevalence in herbaceous plants decreased with increasing plant species diversity [11], [13]. Experimental studies in other systems, combined with longer-term studies and models, will elucidate the degree to which this protective effect of high biological diversity is general.…”

“…In both cases, high diversity is correlated with low disease risk or prevalence. With the exception of fungal diseases of plants [11]–[13] experimental assessments of the role of species diversity in disease dynamics are lacking.…”

Relative importance of multiple scale factors to oak tree mortality due to Japanese oak wilt disease

“…3). The species diversity of a community can either reduce or intensify disease severity (Keesing et al, 2006), but empirical studies have shown that diversity generally reduces disease severity (Keesing et al, 2010), a relationship that has been observed in wild plant communities (Roscher et al, 2007;Haas et al, 2011). Therefore, heterogeneity of land-use might affect mortality by increasing the species diversity of the surrounding area.…”

“…The stand-level density of host trees is known to influence the occurrence of Japanese oak wilt (Yamasaki and Sakimoto, 2009;Yamasaki et al, 2014). In addition, the existence of non-host trees could potentially affect disease occurrence (Roscher et al, 2007;Haas et al, 2011). Therefore, the BAs and number of individuals were summed for each of three host species (Q. crispula, Q. serrata, and F. crenata), and each of the three groups of non-host species (C. japonica, other broad-leaved and coniferous species), then used in the analyses.…”

Effect of Weather on the Occurrence of Puccinia Graminis Subsp. Graminicola and Puccinia Coronata F. Sp. Lolii at Lolium Perenne L. and Deschampsia Caespitosa (L.) P. B.

“…During the hot Mediterranean summers, they are in dormancy and basidiospores germinate during the winter rainy season (Kolmer 2005). Roscher et al (2007) reports that both pathogens produce sporangia, which can be seen especially in late summer and autumn. In our monitoring, combined infections (Puccinia graminis + Puccinia coronata) were the most frequent at Deschampsia caespitosa (L.) P.B.…”