Biology subjects

Van Tassel, D. L.

Publications and source records attributed to Van Tassel, D. L..

4 recordsLinked to original sources

bioRxiv2024

Environment, plant genetics, and their interaction shape important aspects of sunflower rhizosphere microbial communities

Associations with soil microorganisms are crucial for plants overall health and functioning. While much work has been done to understand drivers of rhizosphere microbiome structure and function, the relative importance of geography, climate, soil properties, and plant genetics remains unclear, as results have been mixed and comprehensive studies across many sites and genotypes are limited. Rhizosphere microbiomes are crucial for crop resistance to pathogens, stress tolerance, nutrient availability, and ultimately yield. Here we quantify the relative roles of plant genotype, environment, and their interaction in shaping soil rhizosphere communities, using 16S and ITS gene sequencing of rhizosphere soils from 10 common sunflower (Helianthus annuus) genotypes from 15 sites across the Great Plains of the United States. While site generally outweighed genotype overall in terms of effects on archaeal, bacterial and fungal richness, community composition, and taxa relative abundances, there was also a significant interaction such that genotype exerted a significant influence on archaeal, bacterial and fungal microbiomes in certain sites. Site effects were attributed to a combination of spatial distance and differences in climate and soil properties. Microbial taxa that were previously associated with resistance to the fungal necrotrophic pathogen Sclerotinia were present in most sites but differed significantly in relative abundance across sites. Our results have implications for plant breeding and agronomic microbiome manipulations for agricultural improvement across different geographic regions. ImportanceDespite the importance of plant breeding in agriculture, we still have a limited understanding of how plant genetic variation shapes soil microbiome composition across broad geographic regions. Using 15 sites across the Great Plains of North America, we show that cultivated sunflower rhizosphere archaeal, bacterial and fungal communities are driven primarily by site soil and climatic differences, but that genotype can interact with site to influence composition, especially in warmer and drier sites with lower overall microbial richness. We also show that all taxa that were previously found to be associated with resistance to the fungal pathogen Sclerotinia sclerotiorum were widespread but significantly affected by site, while a subset were also significantly affected by genotype. Our results contribute to a broader understanding of rhizosphere archaeal, bacterial and fungal community assembly, and provide foundational knowledge for plant breeding efforts and potential future microbiome manipulations in agriculture.

ecology↗

bioRxiv2021

Development of first linkage map for Silphium integrifolium (Asteraceae) enables identification of sporophytic self-incompatibility locus

O_LISilphium integrifolium (Asteraceae) has been identified as a candidate for domestication as a perennial oilseed crop and has a sporophytic self-incompatibility system--the genetic basis of which is not well understood in the Asteraceae. To address this gap, we sought to map the genomic location of the self-recognition locus (S-locus) in this species. C_LIO_LIWe used a biparental population and genotyping-by-sequencing to create the first genetic linkage map for this species. Then we developed a novel crossing scheme and set of analysis methods in order to infer S-locus genotypes for a subset of these individuals, allowing us to map the trait. Finally, we identified potential gene candidates using synteny analysis with the annual sunflower (Helianthus annuus) genome. C_LIO_LIOur linkage map contains 198 SNP markers and resolved into the correct number of linkage groups. We were able to successfully map the S-locus and identify several potential gene candidates in the sunflower syntenic region. C_LIO_LIOur method is effective and efficient, allowed us to map the S. integrifolium S-locus using fewer resources than previous studies, and could be readily be applied to other species. Our best gene candidate appears to be worthy of future work in S. integrifolium and other Asteraceae species. C_LI

plant biology↗

bioRxiv2020

Patterns of genetic variation in a prairie wildflower, Silphium integrifolium, suggest a non-prairie origin and untapped variation available for improved breeding.

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSPremiseC_ST_ABSUnderstanding the relationship between genetic structure and geography provides information about a species evolutionary history and can be useful to breeders interested in de novo domestication. The North American prairie is especially interesting because of its relatively recent origin and subsequent dramatic fragmentation and degradation. Silphium integrifolium is an iconic perennial American prairie wildflower targeted for domestication as an oilseed crop. Germplasm in the existing breeding program is derived from accessions collected in restricted geographic regions. We present the first application of population genetic data in this species to address the following goals (1) improve breeding programs by characterizing genetic structure and (2) identify the species geographic origin and potential targets and drivers of selection during range expansion. MethodsWe developed a reference transcriptome as a genotyping reference for samples from throughout the species range. Population genetic analyses were used to describe the distribution of genetic variation and demographic modeling was used to characterize potential processes that shaped variation. Outlier scans for selection and associations with environmental variables were used to identify loci linked to putative targets and drivers of selection. Key resultsGenetic variation partitions samples into three geographic clusters. Patterns of variation and demographic modeling suggest that the species origin is in the American southeast. Breeding program accessions are from the region with lowest observed genetic variation. ConclusionsThis iconic prairie species did not originate within the modern prairie. Breeding programs can be improved by including accessions from outside of the germplasm founding region, which has relatively little variation. The geographic structuring coupled with the identified targets and drivers of adaptation can guide collecting efforts towards populations with beneficial agronomic traits.

evolutionary biology↗

bioRxiv2019

Comparative analysis of seed size, germination, and vegetative allocation in annual and herbaceous perennial crops and their wild relatives in Lupinus and Phaseolus (Fabaceae)

Herbaceous perennial species are receiving increased attention for their potential to provide both edible products and ecosystem services in agricultural systems. Many legumes (Fabaceae Lindl.) are of special interest due to nitrogen fixation carried out by bacteria in their roots and their production of protein-rich, edible seeds. However, herbaceous perennial legumes have yet to enter widespread use as pulse crops, and the response of wild, herbaceous, perennial species to artificial selection for increased seed yield remains under investigation. Here we compare cultivated and wild accessions of congeneric annual and herbaceous perennial legume species to investigate associations of lifespan and cultivation with seed size, germination, and first year vegetative growth patterns, and to characterize covariation among traits. We use \"cultivated\" to describe accessions with a history of human planting and use, which encompasses a continuum of domestication. Analyses focused on three annual and eight perennial Lupinus species, and three annual and four perennial Phaseolus species. We found a significant association of both lifespan and cultivation status with seed size (weight, area, length), germination proportion, node number, stem diameter, shoot dry mass, and root dry mass. Wild seed size was greater in annuals for Lupinus and greater for perennials in Phaseolus. Germination was lower in wild perennials than wild annuals in both genera, and vegetative allocation was roughly equivalent across lifespans in wild Phaseolus. Relative to wild forms, both cultivated annual and cultivated perennial accessions exhibited greater seed size, lower germination proportion, and larger overall plant size. Seed size traits were positively correlated with vegetative growth traits, and all biomass traits examined here were positively correlated. This study highlights some basic similarities and differences between annual and herbaceous perennial legumes, and provides insights into how perennial legumes might respond to artificial selection compared to annual species.

plant biology↗