# Genomic introgressions from wild relatives in the wheat genome alter meiotic dynamics in inter‐varietal hybrids

## TL;DR

Wild wheat relatives can alter meiosis in hybrids, affecting fertility and chromosome behavior, which is important for breeding resilient crops.

## Contribution

A novel oligo-FISH approach reveals how introgressed wild segments affect meiosis in wheat hybrids.

## Key findings

- Introgressions from Aegilops ventricosa reduce pollen viability and floret fertility in hybrids.
- CSRe hybrids show increased rod bivalents and univalents, leading to reduced chiasma numbers and chromosome fragmentation.
- 2AS/2NS segments are often on rod bivalents/univalents, while 7DL/7DvL segments form ring bivalents.

## Abstract

The use of wild relatives to introduce original diversity in the genome of bread wheat (Triticum aestivum L.) is an interesting approach to face the challenges of sustainable agriculture and the impact of climate change on wheat production. However, the influence of these wild‐species introgressions on meiosis in inter‐varietal wheat hybrids remains poorly understood. We analyzed the French wheat variety Renan (Re) carrying Aegilops ventricosa (Aev)‐derived 2AS/2NS and 7DL/7DvL introgressions, the reference cultivar Chinese Spring (CS), which lacks these introgressions, and their inter‐varietal hybrid Chinese Spring × Renan (CSRe). This analysis combined cytogenetic approaches with the assessment of reproductive performance. Furthermore, we generated a cytological atlas of meiosis in wild tetraploid Aev, quantifying bivalent configurations and chiasma frequency. We observed a reduced pollen viability and a slight decrease in floret fertility in the hybrid CSRe. Exploration of the meiotic behavior showed that CSRe exhibited increased numbers of rod bivalents and univalents, leading to a reduced average chiasma number and frequent chromosome bridges and fragmentations, whereas the parental lines maintained stable chromosome pairing. These rearrangements indicate that homologous chromosome pairing and recombination are affected in CSRe. We applied introgression‐specific oligo‐Fluorescent In Situ Hybridization to localize alien segments in CSRe, providing a novel strategy to investigate the meiotic behavior of introgressed regions. The 2AS/2NS introgressed segments in CSRe were frequently located on rod bivalents or univalents, while 7DL/7DvL segments consistently formed ring bivalents. Our results provide a foundation for guiding alien gene introgression and for understanding the behavior of chromosomes with introgressions in the wheat genome.

Introducing wild‐species segments into the wheat genome is a key strategy to revitalize the diversity and to face both challenges of sustainable agriculture and climate resilience. We evaluated the meiotic behavior of inter‐varietal hybrids derived from a cross between a line with wild introgressions (Renan) and a cultivar without introgressions (Chinese Spring). Our oligo‐Fluorescent In Situ Hybridization approach revealed how 2AS/2NS introgression affects meiosis and provides a framework to guide targeted alien gene introgression in wheat breeding.