Soreng, R. J. | bioRxiv Science

bioRxiv2022

A happy accident: a novel turfgrass reference genome

Poa pratensis, commonly known as Kentucky bluegrass, is a popular cool-season grass species used as turf in lawns and recreation areas globally. Despite its substantial economic value, a reference genome had not previously been assembled due to the genomes relatively large size and biological complexity that includes apomixis, polyploidy, and interspecific hybridization. We report here a fortuitous de novo assembly and annotation of a P. pratensis genome. Instead of sequencing the genome of a C4 grass, we accidentally sampled and sequenced tissue from a weedy P. pratensis whose stolon was intertwined with that of the C4 grass. The draft assembly consists of 6.09 Gbp with an N50 scaffold length of 65.1 Mbp, and a total of 118 scaffolds, generated using PacBio long reads and Bionano optical map technology. We annotated 256K gene models and found 58% of the genome to be composed of transposable elements. To demonstrate the applicability of the reference genome, we evaluated population structure and estimated genetic diversity in P. pratensis collected from three North American prairies, two in Manitoba, Canada and one in Colorado, USA. Our results support previous studies that found high genetic diversity and population structure within the species. The reference genome and annotation will be an important resource for turfgrass breeding and study of bluegrasses.

plant biology↗

bioRxiv2021

Limits to resilience of Afroalpine vegetation to grazing and burning: a case study of grasses from the Drakensberg Mountain Centre, southern Africa

O_LIHigh-elevation Afroalpine ecosystems of the Drakensberg Mountain Centre (DMC) of Lesotho and South Africa, renowned for their high endemism and key ecosystem services, are socio-ecological systems that have seen human activity for millennia. However, their responses to land management practices are understudied. Controversy over their natural state has also led to conflicting policies and management emphases. C_LIO_LIFocusing on the crucial ecosystem-modulating component, grasses (Poaceae), we evaluate the response of DMC Afroalpine vegetation to human impact through grazing and burning. Grass species associations were recorded from grassland, shrubland and wetland-riparian-seep ecotypes across a range of grazing and fire regimes to document relationships between abiotic conditions, disturbance, and taxonomic diversity and composition. C_LIO_LICCA of grass community composition retrieved a large cluster of plots of mixed grazing and burning regimes with no particular environmental vector correlated with them. Other smaller groups of plots separated from these were associated to heavy grazing, bioclimatic variables, slope gradient, and aspect. Indicator species analyses found DMC endemic grasses were associated to low grazing, while alien grasses were associated to heavy grazing. GLMs found little difference between ecotype-disturbance categories with regards plant species richness, mean alpha hull=2 range-size of native and sub-Saharan endemic grasses, and site-level Sorensen beta diversity ({beta}sor). Some differences were noted, including the highest cover and proportion of DMC endemics being found in low-grazed grassland, and highest cover and proportion of alien grasses and highest plot-level {beta}sor being found in heavily grazed ecotypes. Relative importance analyses found grazing regime to be the main influence on cover and proportion of DMC endemic and alien grasses. Partial Mantel tests found mean annual temperature and grazing regime to be the main influence on plot-level {beta}sor. C_LIO_LISynthesis: Taxonomic diversity and composition of DMC Afroalpine grasslands was relatively unaffected by moderate grazing and intense burning, although heavy grazing had a largely detrimental impact, with its ubiquity across the DMC a major cause for concern. High levels of endemism, coupled with the above data emphasizing the robustness of DMC grasslands to disturbance, also supports Afroalpine grasslands as a natural component of the DMC. This research reinforces the natural grass-dominated nature of the DMC as a social-ecological system where sustainable management is possible thanks to its resilience to grazing and burning, although current widespread overgrazing requires urgent attention. C_LI

ecology↗