Prunus mume is the only fragrant flowering species of Prunus. According to the previous studies, benzyl acetate and eugenol dominate its floral scent. However, the diversity of its floral scents remains to be elucidated. In this work, the floral volatiles emitted from eight intraspecific cultivars of P. mume with white, pink and red flowers, were collected and analyzed using headspace solid-phase microextraction combined with gas chromatograms-mass spectrometry (HS-SPME-GC-MS). In total, 31 volatile compounds were identified, in which phenylpropanoids/benzenoids accounted for over 95% of the total emission amounts. Surprisingly, except for benzyl acetate and eugenol, several novel components, such as benzyl alcohol, cinnamyl acohol, cinnamy acetate, and benzyl benzoate were found in some cultivars. The composition of floral volatiles in cultivars with white flowers was similar, in which benzyl acetate was dominant, while within pink flowers, there were differences of floral volatile compositions. Principal component analysis (PCA) showed that the emissions of benzyl alcohol, cinnamyl alcohol, benzyl acetate, eugenol, cinnamyl acetate, and benzyl benzoate could make these intraspecific cultivars distinguishable from each other. Further, hierarchical cluster analysis indicated that cultivars with similar a category and amount of floral compounds were grouped together. Our findings lay a theoretical basis for fragrant plant breeding in P. mume.

Low temperature is a primary factor limiting the distribution of Prunus mume. In order to produce a variety that has both cold tolerance and the characteristic fragrance of true mume, previous researchers crossbred a strong-tolerance variety apricot mei, P. mume ‘DF’ (‘Dan Fenghou’) and the weak-tolerance variety of true mume, P. mume ‘BY’ (‘Beijing Yudie’). They gained an offspring variety named P. mume ‘XR’ (‘Xiang Ruibai’), but its cold tolerance is unknown at this point. Here, three varieties (XR, BY, and DF) were selected as the materials, and different low-temperature treatments were used, with temperature as the only variable. Conventional biological methods, such as ion leakage rate, different tissues, and plant viability statistics, were used, as well as an innovative use of infrared engineering and moisture monitoring for dynamic observation of the water-to-ice process in tissues. The results were as follows: DF cold tolerance was the highest, followed by XR and then BY. The LT₅₀ of XR was increased by 6 °C after five days of cold priming at 4 °C, which indicated a stronger cold acclimation ability than the parent varieties. The XR variety enhanced the antioxidant capacity by increasing SOD and POD enzyme activities during low temperature treatment, thus enhancing the cold tolerance. The antioxidant enzyme genes PmSOD3, PmPOD2, PmPOD19, and PmPOD22 had important regulatory roles in XR’s cold acclimation process.

Prunus mume, a famous perennial ornamental plant and fruit tree in Asia, blooms in winter or early spring in the Yangtze River area. The flowering time directly determines its ornamental and economic value, so it is of great significance to study the molecular mechanism of flowering time. SQUAMOSA PROMOTER BINDING PROTEIN (SBP), often regulated by miR156, is an important flowering regulator, although its function is unknown in P. mume. Here, 11 miR156 precursors were analyzed and located in five chromosomes of the P. mume genome. The expression pattern showed that PmSBP1/6 was negatively correlated with miR156. The promoters of PmSBP1/6 were specifically expressed in the apical meristem. Overexpression of PmSBP1/6 in tobacco promoted flowering and changed the length ratio of pistil and stamen. Moreover, PmSBP1 also affected the number and vitality of pollen and reduced the fertility of transgenic tobacco. Furthermore, ectopic expression of PmSBP1/6 caused up-regulated expression of endogenous SUPPRESSOR OF OVEREXPRESSION OF CO1 (NtSOC1). The yeast-one hybrid assay showed that PmSBP1 was bonded to the promoters of PmSOC1s. In conclusion, a miR156-PmSBP1-PmSOC1s pathway was formed to participate in the regulation of flowering time in P. mume, which provided references for the molecular mechanism of flowering time regulation and molecular breeding of P. mume.