Prunus serrulata is an important landscape tree species whose flower color has high ornamental value. However, the molecular mechanisms regulating flower color in P. serrulata remain unclear. By studying the metabolomics and transcriptomics of three different color varieties under the species lineage of P. serrulata, ‘Eigeng’ (EG, white), ‘Albo-rosea’ (AR, pink), and ‘Grandiflora’ (GF, green), the biosynthetic mechanisms of different flower colors in P. serrulata were revealed. The results showed that the different colors of the petals were related to the content of chlorophyll and anthocyanins. Among these, cyanidin-3-O-glucoside and cyanidin-3-O-(6-O-malonyl-β-D-glucoside) were highly expressed in AR. A combined transcriptomic analysis revealed that five flavonoid structural genes, including two DFR genes and three UFGT genes, were specifically expressed. In addition, three key transcription factors, PsMYB77, PsMYB17, and PsMYB105, were identified as regulators of the structural genes DFR and UFGT and participants in the forward synthesis of anthocyanin. This study provides convincing evidence elucidating the regulatory mechanisms of anthocyanin synthesis of P. serrulata and provides a theoretical basis for the breeding and development of new varieties and germplasm resource innovation for cherry blossom.

Sweet viburnum (Viburnum odoratissimum Ker-Gawl.) is a widely used ornamental plant, which has dense branches and leaves, and fast spreading and evergreen habit. In October 2022, leaf spot symptoms were observed in a hedge of sweet viburnum in Yuanshi Garden, Ningbo, China. Fungi were isolated from symptomatic leaves, and were identified using morphological characteristics and phylogenetic analyses of partial sequences of internal transcribed spacer (ITS), actin (act), and translation elongation factor 1-alpha (tef1-α), and were evaluated in pathogenicity tests. The causal agent of sweet viburnum leaf spot was identified to be Phyllosticta capitalensis. Effects of seven fungicides on P. capitalensis were assessed in vitro. Fungicide EC50s (mg L-1) against P. capitalensis were: 270.77 for 75% chlorothalonil (WP); 0.02 for 250 g L-1 azoxystrobin SC; 0.27 for 10% difenconazole WDG; 0.02 for 75% trifloxystrobin + tebuconazole WDG, 9.03 for 35% fluopyram + tebuconazole SC, 5.90 for 500 g L-1 fluazinam SC, and 89.11 for 10% prothioconazole SC. Among these, azoxystrobin SC and trifloxystrobin + tebuconazole WDG could be used for control of viburnum leaf spot. This is the first report of P. capitalensis causing leaf spot of sweet viburnum, and this study provides guidance for chemical management sweet viburnum leaf spot, and on other host plants.

Prunus rufoides is a deciduous wild tree, native to China, which is also used as an ornamental. From late March to December in the years 2018 to 2023, P. rufoides plants growing in Siming Mountain (29°71’08”N, 121°15’12”E), Ningbo, Zhejiang Province, were severely affected by powdery mildew. The disease initially emerged in late March each year, and was characterized as white, irregular mycelial patches on the adaxial surfaces of young leaves. Between July and August, the powdery mildew colonies on affected parts of leaves disappeared, leaving only irregular yellow-brown spots. The disease recurred in September and persisted until late December. Chasmothecia containing asci and ascospores were observed on the leaves in December. Morphological analyses of the chasmothecia indicated a Podosphaera sp. as the causative agent. Molecular identification, based on the internal transcribed spacer (ITS) region (primers ITS4/ITS5) confirmed the identity of the pathogen as Podosphaera prunigena. Koch’s postulates were fulfilled by inoculation tests in which the same pathogen was identified from the inoculated leaf tissue. This study represents the first report confirming the powdery mildew disease on P. rufoides in China to be caused by P. prunigena.