Red walnuts have been widely studied because of their strong antioxidant activity and ornamental value. However, research on the mechanism of anthocyanin biosynthesis in walnuts remains in the initial stage. The regulatory mechanism of TT2-type R2R3-MYB transcription factors in anthocyanin biosynthesis in walnuts is also unclear. Therefore, this study used ‘D2-1’ and ‘Jinghong 1’ walnuts as plant materials. The testa of ‘Jinghong 1’ was red, and its anthocyanin content was significantly higher than that of ‘D2-1’, mainly composed of cyanidin-3-O-arabinoside, cyanidin-3-O-galactoside, and cyanidin-3-O-glucoside. Differentially expressed genes between ‘D2-1’ and ‘Jinghong 1’ testa were enriched in phenylpropanoid biosynthesis and flavonoid biosynthesis. Next, this study identified a TT2-type R2R3-MYB transcription factor JrMYB1L, which was involved in regulating the anthocyanin biosynthesis in the testa of ‘Jinghong 1’. The overexpression of JrMYB1L could promote anthocyanin accumulation in walnut leaves and activate the expression of JrCHS, JrCHI, JrF3H, JrDFR, JrANS, JrUFGT, JrLAR, and JrANR. In addition, yeast two-hybrid results proved that JrMYB1L, JrbHLH42, and JrWD40 proteins could interact with each other. The results of yeast one-hybrid and dual-luciferase assays indicated that JrMYB1L could activate the expression of JrCHS and JrUFGT by binding to their promoters. Based on the above results, this study proposed a possible regulatory mechanism. JrMYB1L activated the expression of JrCHS and JrUFGT in the form of JrMYB1L-JrbHLH42-JrWD40 complex, thereby promoting anthocyanin accumulation in the testa of ‘Jinghong 1’. In summary, this study lays a theoretical foundation for revealing the regulatory mechanism of anthocyanin biosynthesis in red walnut and contributes to the breeding of new varieties of red walnuts with more edible and ornamental value.

Sweet potato (Ipomoea batatas (L.) Lam.) is served as an important root crop worldwide due to its high yield, strong adaptability and nutrient richness. Sweet potato has played a significant role in ensuring food security and family income opportunities for local populations in China for years of experience. The storage roots, which provide abundant nutrition and health benefits to people, are the mainly harvested and consumed parts of sweet potato. However, after harvest, physiological disorders, such as sprouting, mechanical injury and infectious postharvest diseases, increase the magnitude of sweet potato root quality decline and nutritional compound losses. Ethylene and 1-methylcyclopropene (1-MCP) were considered to be effective commercial treatments in sweet potato postharvest. Exogenous ethylene and 1-MCP treatment could successfully inhibit root sprouts and reduce rot decay without affecting the storage quality of sweet potato. This review aims to summarize the latest available information on the effects of ethylene and 1-MCP with respect to enhancing or impairing sweet potato root quality. A better understanding of the influence of ethylene and 1-MCP on root quality parameters will be useful to further explore the role and mechanisms of action of ethylene in regulating the postharvest storage of sweet potato roots and contributions to technological development and innovation.

Rambutan is a tropical tree and its fruit has several favorable characteristics. To understand how the color of the rambutan fruit peel develops, the transcriptome, flavonoid metabolome, and carotenoid metabolome data of two rambutan cultivars, ‘BY2’ and ‘BY7’, which show yellow and red peels at maturity, respectively, were comprehensively analyzed at three developmental stages. We identified 26 carotenoid components and 53 flavonoid components in these cultivars. Anthocyanins were the main component contributing to the red color of ‘BY7’ after reaching ripeness. The carotenoid content decreased sharply as the fruit matured. Hence, we speculated that flavonols were the main contributors to the yellow color of the ‘BY2’ peel. In total, 6805 differentially expressed genes were screened by transcriptome analysis; the majority of them were enriched in metabolic pathways and the biosynthesis of secondary metabolites. Weighted gene co-expression network analysis results revealed that in addition to MYB and bHLH, ERF, WRKY, MYB-related, and C3H were the main potential transcription factors regulating the color of the rambutan peel. In addition, we also identified 12 structural genes associated with flavonoid biosynthesis. The research findings shed light on the molecular mechanisms of color acquisition in rambutan fruit peels, laying the foundation for the quality control of rambutan and the cultivation of differently colored cultivars of rambutan.

Ornamental pepper (Capsicum annuum L.) is an economically important plant with extensive genetic diversity (Zhang et al. 2020). In September 2022, symptoms of wilt and fruit rot were identified in approximately 0.02 hectares of an ornamental pepper plantation in Haikou, Hainan Province, China (110°32' E, 20°06' N). Disease severity reached 85%, with an incidence rate of 90%. Symptoms started as black foliar spots that expanded into large lesions, spreading to fruits and stems, causing wilting (Fig. S1). Samples from symptomatic leaves, fruits, and stems of 27 plants were surface-sterilized with 75% ethanol for 30 s, rinsed five times with sterile water, air-dried, plated on potato dextrose agar (PDA), and incubated at 28°C for 5 to 6 days. To obtain pure fungal cultures, initial isolates were subcultured onto fresh PDA. Among the 27 fungal cultures, 11 isolates from leaves and fruits consistently formed gray to olivaceous colonies. Isolate LJY224 initially produced grayish-white, fluffy mycelia with radiating aerial hyphae. Over time, the colony became grayish-black and produced black, nearly spherical pycnidia. The conidia were oval, initially transparent, and single-celled. Mature conidia were dark brown, septate, with longitudinal striations, averaging 11.55 ± 0.75 µm in width and 24.93 ± 1.50 µm in length (n=35) (Fig. S2), indicating Lasiodiplodia spp. Genomic DNA was extracted using a fungal DNA extraction kit (OMEGA BIO-TEK, GZ Feiyang Biotech Co., Ltd., Guangzhou, China). Molecular identification involved sequencing the rRNA internal transcribed spacer (ITS) region and genes encoding β-tubulin (TUB) and translation elongation factor 1-α (TEF1) with primers ITS1/ITS4, Bt2a/Bt2b, and EF1-983F/EF1-2218R, respectively (White et al. 1990; Rosado et al. 2016; Rehner and Buckley 2005). BLASTn searches with the obtained ITS, TUB, and TEF1 sequences (GenBank accessions OQ612711, OR039814, OR039813) revealed 98% to 100% identity with Lasiodiplodia theobromae reference sequences from the NCBI database (OR018404, KR260830, MN461169), matching 541/548, 446/446, and 947/955 base pairs, respectively. A phylogenetic tree was constructed using concatenated multi-locus sequence analysis (MLSA) of ITS, TUB, and TEF1 (Fig. S3). To fulfill Koch's postulates, healthy 3-month-old ornamental pepper plants were inoculated by spraying the entire plant with a conidial suspension (50 ml, 107 conidia/L) of LJY224, using sterile water as a negative control. Each treatment included three replicates. Plants were maintained at 25°C, 75% humidity, under a 12-h light/dark cycle, and monitored daily. After 14 days, inoculated plants developed black foliar spots that expanded into large lesions, spreading to fruits and stems, and causing wilting, consistent with initial symptoms, while control plants remained healthy (Fig. S4). The re-isolated pathogen showed identical morphology to the original strain. In contrast, no fungi were isolated or recovered from the plants inoculated with water. Results from disease symptoms, colony and spore morphology, pathogenicity tests, and multi-locus DNA sequence analysis suggest that L. theobromae was the pathogen responsible for the disease symptoms on ornamental peppers. L. theobromae is closely related to Botryosphaeria dothidea, both of which cause fruit rot in peppers (Rui et al. 2023). To our knowledge, this is the first report of L. theobromae causing leaf wilt and fruit rot in ornamental pepper in Hainan Province, China, offering insights to mitigate crop losses.

This paper first identified the cold resistance of 38 varieties of avocado by determining the semi-lethal low temperature (LT ₅₀ ) of the leaves using an electrical conductivity method in combination with a logistic function, and then analyzed the correlation between the LT ₅₀ of 27 varieties and the capacitance measured 9 different parts of the leaves in vivo, to explore the relationship between the cold resistance of various avocado varieties and the capacitance of different parts of avocado leaves, so as to develop a new method for highly effective identification of cold resistance of living avocado varieties. The results showed that various avocado varieties’ LT ₅₀ was significantly positively correlated with the capacitance of some parts of leaves, showing that the cold resistance of various avocado varieties was negatively correlated with the capacitance of various leaf parts. The results of mango variety trials conducted for comparison is coincident with the theoretical conclusion reached in the identification of the cold resistance of the avocado. So as to the study of the cold resistance of avocado and mango varieties, the capacitance of live mature leaves measured in the field can be used as a new method for the judgment of cold resistance. Highlight: A new method for identification of avocado cold resistance through measuring the capacitance of different parts of leaves was developed. This method are simple, quick and efficient.