The development and worldwide spread of wheat varieties carrying the Rht-B1b and Rht-D1b dwarfism alleles, starting from the 1950s ’Green Revolution’, resulted in an unprecedented increase in wheat yields. Height-reducing (Rht) and yield-increasing alleles are being widely used during the breeding of high-yielding wheat varieties. Their beneficial effects are essential for future breeders to maintain food security for the growing population.

It is therefore essential to understand how dwarfing alleles affect wheat fertility under the climatic conditions caused by global warming. While a temperature of around 20°C is optimal for the early generative development of wheat, the daily maximum temperature corresponding to the season may exceed the threshold value of 30°C by 2050.

The aim of the present research was to investigate the effect of short-term (24h) high temperature stress (30°C) on the early generative stage and fertility of wheat lines carrying the Rht-B1b or Rht-D1b alleles, with a focus on meiotic cell division, the process that leads to gamete formation.

Our results showed that the increased temperature caused a significant yield loss in the main ears of Rht-B1b and Rht-D1b wheats, greater than the tall wheats carrying the wild type alleles. Our results showed that fertility losses correlated with abnormal forms of meiotic cell division, including defective synaptonemal complex structure, a reduced frequency of homologous recombination and more frequent chromosome mis-segregation.

Additionally, Rht-B1b and Rht-D1b mutants showed meiotic defects at optimal temperature and were more sensitive to high temperature than their high counterparts. Our results show that the identification and introduction of alternative dwarfism alleles into modern breeding programs is essential for the production of high-yielding wheat varieties resistant to high temperatures.

The authors extend their sincere appreciation for AGENT Project (H2020-SFS-2019-2) from the Research and Innovation Action of the European Union (Grant agreement ID: 862613) and TKP2021-NK-TA-06 provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme. AC was supported by János Bolyai Research Scholarship of the Hungarian Academy of Sciences (BO/00416/23/4).