Smith, H. K. | Search bioRxiv

bioRxiv2024

The ideotype for drought tolerance in bioenergy Populus nigra

Fast-growing perennial trees such as Populus nigra L. are important species for wood, plywood, pulp, and bioenergy feedstock production, yet tree vigor in a changing climate is poorly understood. This research aimed to identify breeding targets for yield in water-limited environments, alongside unraveling the relationship between drought, yield, and glucose release in P. nigra. A diversity panel of 20 P. nigra genotypes, selected from a wide natural association population, was grown at three divergent European sites. Through extensive phenotyping of physiological and morphological productivity and water-use traits, under irrigated conditions and when exposed to a progressive drought, we elucidated the adaptive and plastic drivers underlying tree productivity. We have identified the underpinning traits for drought tolerance, whereby high yields can be maintained under water deficit, in this key species. This highlighted the importance of examining the yield stress index (YSI) over the drought resistance index (DRI) to assess genotypes for performance under moderate drought. In this way, we found genotypes with high hydraulic capacity, and large leaves made up of many cells to be best suited to multiple European environments, with contrasting water availability. Moreover, we identified genotypes that combine yield and water use efficiency, with good glucose release potential, which will be important traits for the future of poplar as a bioenergy crop. Vigorous poplar genotypes, which are adapted to wet climates showed high environmental plasticity. However, in European drought scenarios, these trees outperform drought resistant genotypes, and some exhibit good glucose release. These trees are a valuable resource for the future.

plant biology↗

bioRxiv2021

Good and bad lettuce leaf microbes? Unravelling the genetic architecture of the microbiome to inform plant breeding for enhanced food safety and reduced food waste

Lettuce is a high value food crop, consumed raw around the world. Engineering of the leaf microbiome could provide significant benefits for enhanced crop yield and stress resistance and help to reduce food waste caused by microbial spoilage. Lettuce leaves also act as a vector for human pathogens, implicated in several high-profile food-borne disease outbreaks. Since host genotype helps determine microbiome composition, we hypothesize that leaf surface traits can be defined that associate with good bacterial microbiomes providing benefits to the crop and that bad microbiomes, where spoilage organisms and human pathogens are abundant, can also be associated to underlying leaf genetics, providing key targets for future crop breeding. Using a Recombinant Inbred Line (RIL) population, we show that cultivated and wild parental genotypes differ with reduced bacterial diversity, larger leaves and fewer, larger stomata, smaller epidermal cells and more hydrophilic leaf surfaces found in the cultivated compared to wild lettuce. Functional analysis of the associated microbiome revealed increased abundance of genes associated with disease virulence for the cultivated lettuce genotype, suggesting domestication has had broad impacts on leaf and associated bacterial microbiome traits. We defined the core lettuce bacterial microbiome from 171 RILs, comprised of 45 taxa in the phyla Proteobacteria, Actinobacteria, Firmicutes, Chloroflexi and Deinococcus-Thermus. Leaf surface characteristics important in influencing bacterial diversity and abundance were identified as stomatal size (length and width), epidermal cell area and number and leaf surface hydrophobicity of the abaxial leaf surface. Quantitative trait loci (QTL) for leaf surface traits, frequently mapped alongside those for the extended phenotype of bacterial taxa abundance, including for human pathogens Campylobacter spp., Escherichia-Shigella spp., Clostridium spp. (LG 4, 5 and 6) and spoilage bacteria, Pseudomonas spp. (LG 1, 3, 4, 6 and 9). Candidate genes underlying these QTL were enriched in GO terms for cell wall assembly and modification, defence response, hormone-mediated signalling and biosynthesis and anatomical structure development. This work provides the first insight into the genetic architecture of host surface traits in a leafy crop alongside the mapped genetic architecture of bacterial communities and has identified areas of the lettuce genome as important targets for future microbiome engineering.

plant biology↗