Cross incompatibility restricting genome exchange and diversification of primary gene pool in plants: challenges and opportunities

KEY MESSAGE: Crop wild relatives provide essential genetic diversity for improving crop resilience; however, pre- and post-zygotic barriers often restrict interspecific hybridization. Recent approaches enable their effective use in crop improvement programs. Crop wild relatives (CWR), closely related wild taxa of cultivated crops, offer a wealth of genetic diversity essential for developing traits to help crops adapt to the challenges of biotic and abiotic stresses. This diversity is critical to meet the increasing global demand for food, especially under the looming threat of climate change. However, crossing between individuals from different species often results in maladapted or inviable offspring due to pre- and post-zygotic barriers. Pre-zygotic barriers prevent successful pollen-stigma interactions and pollen tube growth, while post-zygotic barriers include hybrid embryo or endosperm failure and chromosome pairing issues, contributing to cross incompatibility (CI). These barriers restrict genome exchange and hinder the diversification of the primary gene pool in plants. Overcoming these barriers is a significant challenge. This review explores the diverse pre- and post-zygotic barriers in interspecific hybridization, emphasizing genetic factors related to CI. Additionally, this review highlights biotechnological approaches such as somatic hybridization and embryo rescue techniques, which are used to overcome these barriers. Through continued research and innovation, these barriers can be overcome, unlocking the full potential of CWR to address the evolving demands of global agriculture. Recent advances in synthetic biology now offer the possibility to reprogram reproductive barriers, turning CI into a controllable trait for hybrid development.