Transcriptome analysis reveals the promotive effect of potassium by hormones and sugar signaling pathways during adventitious roots formation in the apple rootstock.

Apples are economically valuable and widely consumed fruits. The adventitious roots (ARs) formation is gridlock for apple trees mass propagation. The possible function of multiple hormones and sugar signaling pathways regulating ARs formation has not been completely understood in apple. In this study, B9 stem cuttings were treated with KCl treatment, where the highest root numbers (220) and maximum root length of 731.2 cm were noticed in KCl-treated cuttings, which were 98.2% and 215% higher than control cuttings. The content of endogenous hormones: IAA, ZR, JA, GA, and ABA were detected higher in response to KCl at most time-points. To figure out the molecular mechanisms underlying this effect, we investigated transcriptome analysis. In total, 4631 DEGs were determined, from which about 202 DEGs were considerably enriched in pathways associated with hormone signaling, sugar metabolism, root development, and cell cycle-related and were thereupon picked out on their potential involvements in ARs formation. Though, IAA accumulation and up-regulation of various genes contribute to induce AR formation. These results suggest that AR formation is a complex biological process in apple rootstocks, influenced mainly by the auxin signaling pathway and sugar metabolism.