Imprinting Gene Analysis in Endosperm Abortion of Eggplant Distant Hybrids: A Genome-Wide Approach

Eggplant (Solanum melongena L.) has undergone significant domestication, improved yield and quality but reducing disease resistance. Solanum torvum, a related species, offers resistance genes that could enhance eggplant resilience through distant hybridization. However, reproductive barriers, notably endosperm abortion, complicate this process. Imprinted genes, vital for endosperm development, remain underexplored in distant hybrids. This study investigated the hybridization of eggplant lines 177 and SHF with S. torvum (St), focusing on pollen vigor, stigma receptivity, pollen tube behavior, seed fullness, and endosperm development via transcriptome analysis. Results showed that pollen from both species was viable and stigma receptivity facilitated successful pollination. Pollen tubes grew normally, indicating no pre-fertilization barriers. However, seeds from distant hybrids were less full, more deformed, and had significantly lower thousand-seed weights compared to self-bred seeds. Germination rates of hybrids were also significantly lower. Endosperm analysis revealed substantial gaps and reduced areas in hybrids, with shrinkage beginning around 35 days post-pollination. Transcriptome sequencing identified 124 and 27 imprinted genes in SHFxSt and 177xSt hybrids, respectively, with 18 genes co-expressed. These imprinted genes exhibited lower expression in hybrids, impacting starch and sucrose metabolism and other pathways. This research offers a theoretical framework for improving Solanum hybridization, crucial for germplasm innovation and enhancing eggplant resistance.