Magnolia wufengensis, a rare ornamental tree species, is now in a huge gap between market demand and actual supply of seedlings. As cutting propagation is one of the most important means to solve the shortage of seedling supply, this study developed an efficient cutting propagation procedure of M. wufengensis, revealed the morphological and histological changes of adventitious root formation, and explored the rhythm correlation between rooting process and physiological and biochemical changes. Cuttings pre-treated with NAA:IBA (2:1) exhibited the best rooting performance. Anatomical analysis demonstrated that adventitious root primordia of M. wufengensis were initiated from cambial and parenchyma cells of xylem, with no relationship to the callus formed on the epidermis. The rooting process of M. wufengenis can be divided into four periods: induction phase (0–8 dap) (dap means days after planting), initiation phase (8–13 dap), expression phase (13–18 dap), and extension phase (18–28 dap). NAA:IBA (2:1) induced the accumulations of 3-indoleacetic-acid and increased the contents of peroxidase and polyphenol-oxidase near the wounding at induction phase. The initiation phase, with the first histological modifications to the formation of meristemoids, correspond to the increase of peroxidase, polyphenol-oxidase, and soluble protein contents. The synergistic reaction of low 3-indoleacetic-acid and high levels of gibberellins and zeatin also stimulates the initiation phase. In the expression and extension phase, high activities of polyphenol-oxidase, IAA-oxidase, and increased contents of soluble protein co-stimulate the emergence and outgrowth of adventitious roots. The present study not only provides optimized protocol by application of auxin combination but also presents insights in the histological, morpho-physiological, and biochemical changes in stem cuttings of M. wufengensis.

Magnolia biondii Pamp is an important ornamental tree species widely grown and used as a rootstock in the propagation of different Magnolia varieties. In the current studies, anatomical, physiological and endogenous hormones were studied to check the effect of IBA 750 mg/L on the adventitious rooting and to provide theoretical and technical support for the propagation of Magnolia biondii Pamp through stem cuttings. Two thousand stem cuttings were prepared and divided into two groups i.e., IBA treated cuttings and water control. For the evaluation of antioxidant enzyme activities, and endogenous hormones levels, samples were collected on the day of planting and each 5^th day and further steps were carried out in the laboratory according to the protocols and proper precautions. For the anatomical observations, samples were collected on the 13^th, 15^th, and 17^th day for IBA treated cuttings while 21^st, 23^rd, and 25^th day for control. Collected samples were preserved in the FAA solution and further observations were carried out in the laboratory. Anatomical observations showed that it took 13 days for the differentiation of root primordia to the appearance of young adventitious roots in IBA treated cuttings, while it took 21 days to develop primordia in the control. Antioxidant enzyme activities involved in ROS were significantly higher in the IBA treated cuttings compared to control. POD showed a peak on the 13^th day before the emergence of roots in IBA treated cuttings while it showed a peak on the 21^st day in the control. PPO showed a peak on the 21^st day in the IBA treated cuttings while it showed a peak on the 29^th day in the control. SOD showed a peak on the 17^th day in IBA treated cuttings, while it showed a peak on the 25^th day in the control. Exogenous application of IBA enhanced the endogenous IAA and GA₃ levels compared to CK, while it reduced the levels of ABA continuously at the time of rooting and then increased gradually. Inclusively, our study suggests that IBA 750 mg/L is efficient for the rooting of Magnolia biondii Pamp cuttings, as it enhanced the process of antioxidant enzyme activities, endogenous hormones levels and reduced the time of root formation which is evident from the anatomical observations.

Magnolia wufengensis belongs to the Magnoliaceae family. Its variation-rich flowers (tepal number from 9 to 46, tepal color from pink to bright red) and excellent wood characteristics (strong, straight, texture) have important ornamental and economic value (Duan et al. 2019; Luyi et al. 2006). M. wufengensis is popularly cultivated in parks, courtyards, mountains, and along roadsides. In May 2020, leaf spot symptoms were observed on over 85% of M. wufengensis in Yuyangguan Township, Wufeng County, Hubei Province (110.60°E, 30.21°N). The damaged area was over 18.7 hectares. Early symptoms began as small brown spots with a light-yellow halo. Gradual lesions expanded, and the center was withered, gray, and necrotic with a dark brown border. Eventually, several spots combined with larger irregular lesions, turning the leaves yellow and causing them to fall off. The border of lesions and healthy tissues were cut into small pieces (5×5 mm), and surface sterilized with 1% sodium hypochlorite solution for three minutes, rinsed three times with sterile water, and plated on potato dextrose agar (PDA) medium at 25±2 °C with a 12h photoperiod under fluorescent lighting. Pure isolates (MCS1228.1, MCS1228.4, MCS1228.9) were gray to pale grayish, and their average growth rate was 10.5±1.23 mm/day. Conidiophores were hyaline, aseptate, branched. Conidia were hyaline, aseptate, cylindrical, and 14.00 to 25.17 × 4.74 to 6.56 μm in size (average 17.48 × 5.58 μm) (n=50). Appressoria were brown and showed multivariate shape. The morphological characteristics of the isolates corresponded to the description given for Colletotrichum fructicola (Liu et al. 2015). Molecular identification was accomplished through amplification of the internal transcribed spacer (IST), actin (ACT), calmodulin (CAL), chitin synthase (CHS-1) glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and beta-tubulin (TUB2) genes (Fu et al. 2018). The ITS (OL800580.1, OL800581.1, OL800582.1), ACT (GenBank accession No. OL873155- OL873157), CAL (GenBank accession No. OL873158- OL873160), CHS-1 (GenBank accession No. OL873161- OL873163), GAPDH (GenBank accession No. OL873164- OL873166) and TUB2 (GenBank accession No. OL873167- OL873169) sequences were deposited in GenBank. A Bayesian inference phylogenetic tree based on multilocus sequences was constructed, and the sequences of the 3 isolations showed the same homology with C. fructicola (Fu et al. 2018). To fulfill Koch's postulates, 30 potted seedlings were inoculated with 1×10^6 conidia/ml suspension of each isolate by spraying the leaves, and 30 potted seedlings were sprayed with sterile distilled water as control. Inoculated and control plants were kept in a greenhouse with 25/15°C (day/night) temperature and 80% relative humidity. In addition, 30 healthy detached leaves free of pests and diseases were washed three times with sterile distilled water, air-dried, and artificially inoculated using a 6 mm (diameter) PDA medium (5 days incubation) with mycelium. 30 leaves were inoculated with sterile PDA medium as control. All leaves were sprayed with sterile water every 24 hours, covered with plastic wrap, and incubated at 25±2 °C, 100% humidity. The experiment was repeated three times. Similar symptoms to those found initially were both observed on all the inoculated potted seedlings and detached leaves after 14 days and 5 days post inoculation (dpi), respectively. Whereas the controls remained symptomless. The reisolated pathogens from symptomatic tissues were identical to the original isolates. In this study, isolated fungi associated with M. wufengensis leaf spot were identified as C. fructicola based on morphological and multiloci phylogenetic analyses, and Koch's postulates. Colletotrichum species are important plant pathogens and cause diseases in a wide variety of woody and herbaceous plants (Cannon et al. 2012). C. fructicola has been identified as a responsible pathogen for apple (Casanova et al. 2016), Fatsia japonica (Shi et al. 2017), and Rubus corchorifolius (Wu et al. 2021) leaf spot. To our knowledge, this is the first report of C. fructicola causing leaf spot in M. wufengensis in China. This research may contribute to the development of management strategies for this disease.

Magnolia denudata (Lilytree or Yulan magnolia) is an important ornamental species of the genus Magnolia. It has considerable economical value because of its beautiful fragrant flowers and excellent...