An epigenetic breeding system in soybean for increased yield and stability

Abstract

ABSTRACTEpigenetic variation has been associated with a wide range of adaptive phenotypes in plants, but there exist few direct means for exploiting this variation. RNAi suppression of the plant-specific gene,MutS HOMOLOG1(MSH1), in multiple plant species produces a range of developmental changes accompanied by modulation of defense, phytohormone, and abiotic stress response pathways. Thismsh1-conditioneddevelopmental reprogramming is retained independent of transgene segregation, giving rise to transgene-null ‘memory’ effects. An isogenic memory line crossed to wild type produces progeny families displaying increased variation in adaptive traits that respond to selection. This study investigates amenability of theMSH1system for inducing epigenetic variation in soybean that may be of value agronomically. We developed epi-line populations by crossing withmsh1-acquired soybean memory lines. Derived soybean epi-lines showed increase in variance for multiple yield-related traits including pods per plant, seed weight, and maturity time in both greenhouse and field trials. Selected epi-F2:4and epi-F2:5lines showed an increase in seed yield over wild type. By epi-F2:6, we observed a return of MSH1-derived enhanced growth back to wild type levels. Epi-populations also showed evidence of reduced epitype-by-environment (e × E) interaction, indicating higher yield stability. Transcript profiling of the soybean epi-lines identified putative signatures of enhanced growth behavior across generations. Genes related to cell cycle, abscisic acid biosynthesis, and auxin-response, particularly SMALL AUXIN UP RNAs (SAURs), were differentially expressed in epi-F2:4lines that showed increased yield when compared to epi-F2:6. These data support the potential ofmsh1-derived epigenetic variation in plant breeding for enhanced yield and yield stability.