Effects of Different Seasons on Cutting Propagation of Five Citrus Rootstocks

[Objectives] To explore the cutting propagation mode of citrus rootstock, improve the survival rooting rate of citrus rootstock, and provide theoretical guidance and technical reference for the rooting research of difficult-to-root plants such as citrus. [Methods] Five citrus rootstocks Citrus tangerina Tanaka ‘Hongju’, Citrus haniana Hort ‘Suanju’, Citrus limonia Osbeck ‘Hongningmeng’, Citrus sinensis×Poncirus trifoliata ‘Zhicheng’ and Poncirus trifoliate (L) Raf. ‘Zhike’ were used as experimental materials to select the suitable cutting substrate for citrus rootstocks by measuring the physical properties of the substrate. Cutting was carried out in spring, summer, autumn and winter respectively. After cutting, the morphological changes of cuttings were observed regularly, and the callus rate, germination rate and rooting rate of cuttings were recorded. [Results] The best substrate for citrus rootstock cutting was peat soil, vermiculite and fine river sand (2：1：1). The callus of citrus rootstock in different cutting seasons began to appear in 10-22 d, and the callus rate reached 55%-100%. In terms of budding, the budding time was the earliest in summer and autumn, and slightly later in spring and winter; the germination rate of C. limonia Osbeck ‘Hongningmeng’ was the highest, and the germination rate of C. sinensis×P. trifoliata ‘Zhicheng’ and P. trifoliate (L) Raf. ‘Zhike’ was lower; in terms of rooting, C. limonia Osbeck ‘Hongningmeng’ had the earliest rooting time and the highest rooting rate and could reach 100% in all seasons; the rooting rate of C. tangerina Tanaka ‘Hongju’ was 50%-80%; the rooting rate of C. haniana Hort ‘Suanju’ was 60%-80%; C. sinensis×P. trifoliata ‘Zhicheng’ and P. trifoliate (L) Raf. ‘Zhike’ showed the earliest rooting time and the highest rooting rate in summer, and the latest rooting time and the lowest rooting rate in winter, which were only 14.5%. Therefore, different citrus rootstock varieties should choose the appropriate cutting time according to their own characteristics. [Conclusions] The results of this study can provide a scientific basis for a large number of cutting propagation of different citrus rootstocks, and have practical guiding significance for large-scale planting.