Enhancing Genetic Diversity in Spring Restorer Germplasm for Hybrid Wheat Breeding Using Winter Wheat Genotypes

Hybrid breeding has the potential to overcome the yield barriers through hybrid vigor, improving yield instability and stress resilience. In wheat, a predominantly self-pollinating species, the cytoplasmic male sterility-restoration of fertility (CMS/Rf) system is a promising approach for reaping the benefits of hybrid vigor or heterosis. However, insufficient genetic diversity in the elite germplasm limits the exploitation of heterosis in wheat. This study aimed to expand the genetic diversity in locally adapted restorer germplasm by enriching the male parental gene pool carrying T. timopheevii cytoplasm. We used selected European winter wheat genotypes with desirable out-crossing characteristics to develop spring × winter wheat backcross derivatives. Phenotypic and genotypic assessments were conducted to evaluate genetic diversity and performance of new germplasm for key traits including anther extrusion (VAE), plant height (PH), spikelets per spike (SPS) and tiller number (TN) in the field trials. Significant phenotypic diversity was observed in the resultant germplasm for desirable floral and agronomic traits including anther extrusion, days to flowering, and plant height, along with sufficient molecular diversity as revealed by SSR markers. This diversified germplasm also exhibited enhanced performance for key out-crossing and agronomic traits (PH, VAE, SPS, TN) compared to original restorers, when evaluated over two field seasons. These findings indicate significant genetic improvement of the spring restorer germplasm through the winter-wheat facilitated diversity enhancement strategy. Therefore, this improved novel restorer germplasm has strong potential for CMS/Rf-based hybrid wheat breeding, paving way for the development of superior wheat hybrids with significant heterosis.