Citri Reticulatae Pericarpium, especially the pericarp of Citrus reticulata Blanco cv. Chachiensis (PCRC), is an important edible and medicinal ingredient for health and pharmacological properties. Citrus Huanglongbing, a devastating disease that currently threatens the citrus industry worldwide, is caused by a phloem-limited alpha-proteobacterium, “Candidatus Liberibacter asiaticus” (CLas). The industry of cultivar Chachiensis has been suffering from HLB. Although HLB affected the quality of citrus fruit, whether the quality of PCRC was affected by HLB remains unclear. In this study, we compared the metabolite profiles between HLB-affected and healthy PCRC from three sources: fresh, 6-month-old, and 9-year-old PCRC, through the untargeted LC–MS method. Compared to healthy controls, various types of bioactive compounds, mainly flavonoids, terpenoids, alkaloids, coumarins, polysaccharides, and phenolic acids, accumulated in HLB-affected PCRC, especially in the HLB-affected 9-year PCRC. In particular, isorhamnetin, isoliquiritigenin, luteolin 7-O-beta-D-glucoside, limonin, geniposide, pyrimidodiazepine, scoparone, chitobiose, m-coumaric acid, malonate, and pantothenic acid, which contributed to the pharmacological activity and health care effects of PCRC, were highly accumulated in HLB-affected 9-year-old PCRC compared to the healthy control. Multibioassay analyses revealed that HLB-affected 9-year-old PCRC had a higher content of total flavonoids and total polyphenols and exhibited similar antioxidant capacity as compared to healthy controls. The results of this study provided detailed information on the quality of HLB-affected PCRC.

Citrus Huanglongbing (HLB) is caused by the phloem-limited α-proteobacterium ‘Candidatus Liberibacter spp.’, among which ‘Ca. L. africanus’ (CLaf) has posed a significant threat to citrus production in Africa for nearly a century. CLaf is closely related to the globally prevalent ‘Ca. L. asiaticus’ (CLas), whereas little is known about the virulence of CLaf, primarily because of limited genome resources. In this study, we completed the whole-genome assembly and annotation of the CLaf strain Zim (from Zimbabwe). Compared with CLas, a total of 102 CLaf unique genes were identified, including 14 potential Sec-dependent effector (SDE) genes, 29 phage-associated genes, and 59 genes with hypothetical function. Among 14 SDEs, V9J15_03810 was able to induce a significant hypersensitive response in Nicotiana benthamiana, indicating its potential as a virulence factor for CLaf. Genome analysis showed that the CLaf strain Zim genome harbored a complete prophage region (named P-Zim-1, 42,208 bp). P-Zim-1 retained two immunosuppressive peroxidase genes (V9J15_02125 and V9J15_02130) homologous to CLas prophage SC1/SC2, whereas the lysogen-associated genes encoding integrase (V9J15_01970) and repressor (V9J15_02080) were homologous to the prophage of ‘Ca. L. solanacearum’, the causal agent of potato zebra chip disease. In addition, P-Zim-1 carried a novel CRISPR/Cas system, including a CRISPR array (located within V9J15_02040, ranging from 443,643 to 443,897) and five CRISPR-related Cas proteins (V9J15_02005, V9J15_02010, V9J15_02015, V9J15_02025, and V9J15_02035). This study first characterized the unique genomic feature of CLaf related to virulence and prophage, which will facilitate future research on CLaf biology and African HLB management.

Among fruits and fruit products, oranges and orange juice are the most widely consumed worldwide. However, the effects of pest infestation of oranges on the quality of orange juice are not yet known. To evaluate the effect of the oriental fruit fly Bactrocera dorsalis on the antioxidant activity of orange juice, we measured changes in the vitamin C (Vc) concentration, total phenol content, and antioxidant activity of orange juice after the introduction of fruit fly eggs. Ten days after the eggs were introduced (larvae removed), the concentration of Vc in orange juice was 18.65 µg/mL, which was 9.16 µg/mL lower than that measured in healthy orange juice. In addition, the total phenol content decreased by 46.519 mg Gallic Acid Equivalents (GAE)/g to 9.748 mg GAE/g. Furthermore, the free-radical scavenging activity decreased from 22.297% to 5.393%. Correlation analysis indicated significant correlations between Vc concentration, total phenol content, and antioxidant activity of orange juice after B. dorsalis infestation. The decrease in Vc concentration, total phenol content and free-radical scavenging activity indicated that B. dorsalis changed the quality of orange juice by affecting the antioxidant activity of the juice after the oranges were infested.

Red rust disease, caused by the algal pathogen Cephaleuros spp., poses an increasingly significant threat to oolong tea (Camellia sinensis) cultivation. Currently, however, effective management is hindered by a lack of species-specific diagnostic methods and limited analysis of host-response physiological changes. In this study, the region-wide survey was conducted, species-specific molecular diagnostics, multi-scale microscopy, and host biochemical analysis (pigments and antioxidants) were utilized to investigate Cephaleuros diversity, invasion biology, and host responses in oolong tea. Across 785 composite leaf samples, the overall Cephaleuros positivity rate was 30.19%, with incidence significantly higher detection rate in Chaozhou, Guangdong (46.59%) than in Fujian (7.58%). Genotyping via psaA-targeted qPCR revealed strikingly distinct regional distributions: C. parasiticus was predominantly detected in Chaozhou (95.3%), whereas C. virescens was the only identified species in Fujian, with no mixed infections identified. Histological analysis of Chaozhou samples revealed subepidermal thalli beneath both leaf surfaces, accompanied by palisade/spongy necrosis, which suggested deeper tissue invasion by C. parasiticus. To characterize host responses, we quantified photosynthetic pigments and antioxidant enzymes in lesion centers and margins across representative cultivars. In green-leaf cultivars, infection was generally associated with decreases in chlorophyll a and b (with significance varying by cultivar), whereas carotenoid responses were modest and cultivar dependent. In contrast, two etiolated mutants exhibited significant increases in chlorophyll a (2.0–3.7-fold) and carotenoids (~1.5–1.6-fold), and anthocyanin increased by ~62% in the etiolated Juduozai mutant. Antioxidant enzyme activity was spatially structured, with peroxidase (POD) and catalase (CAT) strongly induced at lesion margins (POD increase 39–248%), while lesion centers exhibited reduced activity (5-41%). Superoxide dismutase (SOD) showed a modest increase at the lesion margins (increase 18–31%). A composite "reaction index" (POD+SOD at lesion margins) was used to classify cultivars into high and moderate response categories. These findings provide new insights into the ecological dynamics and host responses associated with Cephaleuros infection in oolong tea and highlight the potential for using these indicators in cultivar selection and disease management strategies.

Background: Mangrove plants are a core component of coastal ecosystems, directly influencing biodiversity and shoreline stability. However, in recent years, due to the combined pressures of human activities and climate change, nearly half of the mangrove species in China are endangered and require urgent conservation measures. This study analyzed the population dynamics and stress factors affecting four rare and endangered mangrove species—Lumnitzera racemosa, Ceriops tagal, Barringtonia racemosa, and Heritiera littoralis—on the Leizhou Peninsula, providing scientific evidence for their conservation. Methods: Field surveys and plot investigations were conducted, with population dynamics and structure quantified using static life tables, survival rates, mortality rates, and disappearance curves. Additionally, the MaxEnt species distribution model and GIS technology were applied to predict the potentially suitable distribution areas. Results: The findings revealed that the population of L. racemosa exhibits an atypical pyramid structure, with few seedlings and constraining population growth potential. The C. tagal population follows an irregular pyramid structure, with abundant seedlings but fewer mature individuals, suggesting a rapid decline followed by stability. The B. racemosa population also follows an irregular pyramid structure, with many seedlings and a greater proportion of middle-aged and older individuals, facing the risk of early mortality. The H. littoralis population is also in decline, with few seedlings and a severe risk of local extinction. MaxEnt model predictions indicated that temperature is the primary environmental factor, with Area Under the Curve (AUC) values for all species exceeding 0.8, indicating strong predictive ability. The predicted potential suitable areas showed an expanded distribution range compared to current distribution points, providing valuable references for species introduction and propagation. Conclusions: This study described the population structure of the four mangrove species on the Leizhou Peninsula and assessed their primary stress factors. The results provided a theoretical basis for the conservation and restoration of endangered mangrove species and offer important guidance for developing effective conservation strategies in southern China.