Meiotic recombination, pollen size variation, and allelic selection in rye (Secale cereale) under the effects of nutrient deficiency caused by 140-years of monoculture

• Applicant: Dr. Steven Dreissig
• Subject Area: Plant Breeding and Plant Pathology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 466716861

Plant breeding largely relies on the generation of novel allelic combinations through meiotic recombination and cross-pollination throughout sexual reproduction to achieve crop improvement. These processes are collectively referred to as genetic shuffling. At the same time, recombination rate variation and cross-pollination are major evolutionary forces in plant populations. Many crops essential to human nutrition, such as barley, wheat, and rye, comprise large heterochromatic genomes where approximately 30% of all genes are located in low-recombining heterochromatic regions, rendering these genes inaccessible to breeding efforts. These genomic regions tend to harbour genes involved in basic cellular processes such as photosynthesis, thereby holding promise for future crop improvement under changing climate conditions. Furthermore, cross-pollination in wind-pollinating species is affected by pollen size, i.e. how far pollen grains can be dispersed by wind.Genetic shuffling processes, both meiotic recombination and cross-pollination, are at their very core genetically determined developmental programmes governed by a multitude of more than 80 genes currently described in plants. However, both are also known to be affected by environmental conditions, shaping quantitative differences and mediating changes in patterns of diversity throughout evolution. This project aims to understand the genetic architecture underlying variation in recombination rates, pollen size, and patterns of selection in response to abiotic stress caused by long-term monoculture. The knowledge generated here holds promise to improve plant breeding methods and support crop improvement by increasing genetic shuffling through recombination and cross-pollination. Furthermore, it will improve our understanding of how recombination and cross-pollination directly impact on allele frequency changes through selection in plant populations.To achieve this, we will take advantage of a long-term field trial in which a genetically divergent rye population is subjected to the effects of abiotic stress caused by 140 years of monoculture. The project will focus on three objectives: (1) to reveal the genetic architecture underlying recombination rate variation in response to abiotic stress and based on genetic divergence, (2) to investigate pollen size variation caused by abiotic stress and genetic divergence and identify the underlying genes, and (3) to explore patterns of selection imposed by abiotic stress and how variation in recombination and pollen size directly affect allele frequency changes.This will further our understanding of how new allelic combinations are effectively generated through recombination and cross-pollination, and alleles identified will be available for plant breeders to be incorporated into breeding programmes.

• DFG Programme: Independent Junior Research Groups