Establishment of an Efficient Softwood Cutting Propagation System for Prunus salicina Lindl. via Plant Growth Regulators and Agronomic Regulation

Plum is an economically important stone fruit crop worldwide, but its industrial production is limited by low propagation efficiency and disadvantages associated with conventional grafting. This study established a softwood cutting system for three elite Nai plum cultivars (‘Shibanwannai’, ‘Huangguanli’, and ‘Zaofurong’). Gradient concentrations of two plant growth regulators (PGRs), NAA and ABT, were tested in combination with integrated agronomic practices, including girdling pretreatment, a tested growing substrate formulation, and staged moisture management. The results showed that 100 mg·L−1 NAA and 150 mg·L−1 ABT yielded relatively high seedling survival rates (78% to 85%) and promoted the formation of well-developed mixed adventitious root systems. Distinct cultivar-specific differences in sensitivity to PGRs were detected among the three cultivars. This softwood cutting protocol shortens the nursery cycle to 3–4 months, compared with 18–24 months required by traditional grafting. The established high-efficiency cutting method supports standardized nursery production and may facilitate the sustainable development of the Nai plum industry.