A simple, rapid, and quantifiable system for studying adventitious root formation in grapevine

Woody cutting is customarily utilized as a material in research on grape adventitious root formation (ARF). However, phenotypic heterogeneity caused by the complex background influenced its use for molecular mechanism research of ARF of grape. The present study tested various types of explants from grape tissue culture plantlets and found that the whole leaf: blade with the petiole (LP) was the simplest unit that can easily form adventitious roots (ARs). LP explants which can be easily obtained, directly generate ARs via de novo organogenesis from the base of the petiole. Plantlet age, node position, blade size, the health condition of leaves, and light intensity have been demonstrated to affect the homogeneity of the ARF phenotype in LP. By controlling these parameters, selected LPs cultured on a medium with 6 g·L-1 agar and 10 g·L-1 sucrose under dark conditions started rooting at 6–7 days after culture (DAC) and reached 100% rooting rate within 13–14 DAC. Using this system, the core role of auxin on ARF was verified by exogenous application of indole butyric acid (IBA) and N-1-naphthylphthalamic acid (NPA). Strikingly, we found that light promoted ARF in the absence of sucrose, but inhibited ARF in the presence of sucrose (10 g·L-1), while a low concentration of 0.34 µM NPA partially relieved the inhibition. Finally, this study confirmed that exogenous plant growth regulators (PGRs), including 6-benzyl aminopurine (6-BA), gibberellic acid 3 (GA3), and 2,4-epibrassinolide (EBR), significantly inhibited ARF. This simple, rapid, quantifiable ARF research system provides a new approach to studying the factors influencing the formation and development of grape adventitious roots and establishes a framework for investigating the mechanism of grape adventitious root induction and initiation.