Emails: hanafi@ipk-gatersleben.de; reif@ipk-gatersleben.de

Unlike inbred crops, hybrids deliver more stable yields and benefit from the phenomenon of heterosis. Efficient hybrid seed production relies on the optimization of both female and male ideotypes with high cross pollination capability. However, due to wheat's domestication as a self-pollinating species and centuries of breeding for cleistogamy, its cross-pollination ability may have decreased in elite varieties.

Therefore, understanding the key aspects that enhance pollen receptivity and boost female hybrid seed set will help in developing and selecting optimal plant ideotypes. To fulfill this aim, we tested hybrid seed set of diverse elite material and a double haploid population, emasculated using a chemical hybridization agent (CHA), across several environments.

Large-scale field screenings demonstrated that high anther extrusion and maximum pollen shedding significantly enhanced the likelihood of successful pollination. Although high levels of these indirect traits already offer a good starting point, a more targeted approach was used to investigate whether factors beyond pollen traits may affect female receptivity. We focused on male lines with sufficient-to-high anther extrusion levels and we investigated the interactions of various traits to better understand their impact on seed set.

Flowering begin and duration showed the largest proportion of the variance in seed set. Therefore, employing a multivariate approach to examine the genetic covariances among these traits could elucidate how their combined expression influenced the overall seed set performance, providing then a strategic pathway for enhanced hybrid wheat breeding.

While genomic assisted breeding of favourable parental ideotypes identified several QTLs with minor to large effect, seed set showed a single major QTL on chromosome 1B, which accounted for 21% of the total phenotypic variation, emphasizing the complex polygenic architecture underlying this particular trait.