Research Projects

Heterosis, or hybrid vigor, is a form of hybridization between different plant species or parents with varying ploidy levels that often results in beneficial and superior phenotypes in the F1 progeny. To develop elite crop varieties with improved growth, yield, and tolerance to both abiotic and biotic stresses, breeders have been harnessing heterosis for many years. Wild crop species are valuable germplasm resources for creating these elite varieties. However, strong pre-zygotic or post-zygotic reproductive barriers prevent heterosis or the rapid introgression of useful alleles from wild species into cultivated ones. Often, intra- and interspecific hybridizations encounter issues such as endosperm failure, resulting in seed collapse. This failure is caused by maternal and/or paternal genome dosage imbalances and changes in methylation levels (Figure 1). The main goal of this proposal is to overcome seed-based reproductive barriers mediated by small RNAs in crosses between wild tomato species Solanum peruvianum and the cultivated Solanum lycopersicum. This project aims to shed light on how paternal small RNAs and DNA methylation contribute to post-hybridization barriers. To achieve the objectives, two approaches will be employed. The first step involves creating epimutagenesis lines by applying the chemical inhibitor 5-Azacytidine to the seeds of S. peruvianum. These lines, with temporary loss of DNA methylation, will be used for interspecific hybridization. The second approach involves reducing small RNA production specifically in the pollen of S. peruvianum by expressing RNASE III LIKE 1 (RTL1) protein and generating SiNRPD1 mutant lines, a key protein in the small RNA biogenesis pathway. Transgenic pollen with depleted siRNAs will be used for hybridization with the cultivated tomato, S. lycopersicum. Overall, the findings from this project could significantly impact plant breeding and crop improvement, as there is strong interest in introducing genetic resources from wild species into domesticated crops.