Arachidin-2 suppresses Peronophythora litchii and postharvest decay of litchi fruit.

Co-culture supernatant improves postharvest litchi fruit quality and reduces downy blight incidence through regulation of phenylpropanoid metabolism and ROS homeostasis

Melatonin promotes anthocyanin biosynthesis in postharvest litchi fruit via regulation of the transcription factor LcWRKY17

Litchi is the fruit of warm climates and has a very short shelf life as the fruit loses its red color within the span of 2-3 days. The current study was planned to evaluate the effect of hexanal fumigation on overall fruit quality and retention of aesthetic appeal of the fruit under low temperature storage conditions. Hence, litchi fruit harvested at the ripening stage was fumigated with 0%, 1%, 2%, 3%, and 4% hexanal concentration followed by cold storage at 5 ± 1°C for 28 days by maintaining 90% relative humidity. During cold storage, fruits were evaluated for physiological weight loss (PLW), browning severity, and anthocyanin depletion in pericarp. Physico-chemical quality characteristics were determined in litchi aril samples. Total phenolics and total antioxidants were also determined from aril samples, whereas antioxidative enzymes such as SOD, CAT, POD PPO were determined from pericarp tissues in litchi pericarp at 7 -day intervals. Postharvest hexanal application significantly controlled pericarp browning and resulted in higher anthocyanin content with reduced weight loss than control fruit. Hexanal preserved a steep rise in SSC and maintained relatively low SSC compared to control fruit throughout the cold storage period; however, titratable acidity, ascorbic acid contents, phenolic components and total antioxidants in litchi fruit aril were significantly augmented in all hexanal formulations, with significantly higher values recorded in 1% hexanal treatment. Likewise, antioxidative enzyme activities, such as SOD (74.54 mg-1 protein) and CAT (82.42 mg-1 protein), were significantly higher in hexanal-treated fruits, while POD (30.2 mg-1 protein) and PPO enzyme (34.42 U mg-1 protein) activities were significantly hindered in hexanal-treated litchi fruits which were significantly higher in control treatment. Overall, 1% hexanal formulation showed more promising results in terms of maintaining quality characteristics and color of the fruit during the extended storage period. Conclusively, hexanal application retained the pericarp red color and delayed browning by maintaining fruit quality of ‘Gola’ litchi longer than control fruits.

ABSTRACT Peronophythora litchii is an oomycete pathogen responsible for litchi downy blight, a significant threat to global litchi production. Autophagy, a conserved degradation pathway crucial for the growth, development, and pathogenicity of phytopathogenic organisms, remains an area of active investigation. In this study, we characterized the function of the Atg26 homolog PlAtg26b in P. litchii. Using the CRISPR/Cas9 genome editing system, we generated PlATG26b knockout mutants and determined that PlAtg26b localizes to mitochondria under stress conditions. Although deletion of PlATG26b did not impair selective autophagy, it markedly reduced Atg8-PE synthesis, vegetative hyphal growth, asexual and sexual reproduction, and zoospore release. Furthermore, PlATG26b-deficient mutants exhibited significantly reduced virulence on litchi fruits and leaves. Collectively, our findings demonstrate that PlAtg26b plays a pivotal role in the biological development and pathogenicity of P. litchii.

Metabolic dynamics of litchi pericarp and pulp during browning: Unraveling differential profiles through temporal clustering and untargeted metabolomics.

Regulation of α-bergamotene biosynthesis by the LcDOF5.8- LcTPSbms regulatory module in litchi fruit

Improved detection of soluble solid and anthocyanin in litchi fruits by normalized VNIR-SWIR transmittance hyperspectral imaging and SPF-SSF-GSF-NLF fusing method.

Litchi is an important subtropical fruit, highly valued by consumers for its vibrant color and distinctive flavor. B-box (BBX) proteins, which are zinc finger transcription factors, play a crucial role in regulating plant growth, development, and stress responses. Nevertheless, the specific function of BBX genes in the development and coloration of litchi fruit remains inadequately understood. In this study, 21 LcBBX genes (designated as LcBBX1-LcBBX21) were identified within the litchi genome. These genes were categorized into five sub-families based on phylogenetic analysis and were found to be unevenly distributed across 12 chromosomes. Promoter analysis revealed a rich presence of light-responsive elements, such as the G-box, and abscisic acid (ABA) responsive elements, including ABRE, within the promoter regions of LcBBX genes. Protein–protein interaction predictions indicated that the majority of LcBBX genes have the potential to interact with the light-responsive factor HY5. Transcriptome analysis and qRT-PCR results demonstrated that LcBBX genes exhibit tissue-specific expression patterns. Notably, most LcBBX genes were highly expressed prior to fruit coloration, whereas LcBBX4 and LcBBX10 were upregulated during the fruit coloration phase. Furthermore, LcBBX1/4/6/7/15/19 were upregulated in response to light following the removal of shading. The findings suggest that LcBBX4 may directly regulate anthocyanin biosynthesis in litchi pericarp. This study provides critical insights into the molecular mechanisms underlying litchi fruit development and coloration.

The storability of litchi fruits with different maturity is correlated to seed vigor

Litchi (Litchi chinensis Sonn.) is a non-climacteric fruit with a red pericarp that browns after harvest, reducing market value. Pericarp browning is linked to oxidative stress caused by reactive oxygen species (ROS). This study explored the combined effects of ultrasound (US; 37 ± 3 kHz for 10 min) and melatonin (1 and 2 mM) on litchi pericarp browning during ambient storage. On last day of storage, US combined with 1 and 2 mM melatonin exhibited lowest pericarp browning compared to their individual application with a score of 2.54 and 3.64. The results suggest that, combined treatment of ultrasound and melatonin effectively mitigates oxidative stress with lower ROS accumulation and polyphenol oxidase activity. Additionally, higher levels of anthocyanins, polyphenols, antioxidants, and phenylalanine ammonia lyase activity were maintained. It also preserved fruit quality, including weight, soluble solids, and titratable acidity, while reducing decay suggesting combined treatment of ultrasound and melatonin effectively enhances the postharvest quality of litchi fruit with reduced pericarp browning.

The use of UAVs to detect litchi in natural environments is imperative for rapid litchi yield estimation and automated harvesting systems. However, UAV-based lychee fruit detection bottlenecks arise from complex canopy architecture and leaf occlusion. This study proposed a collaborative optimization strategy integrating agronomic technique with deep learning. Three leaf thinning intensities (0, 6, and 12 compound leaves) were applied at the early stage of fruit to systematically evaluate their effects on fruit growth, canopy structure, and detection performance. Results indicated that moderate defoliation (six leaves) significantly enhanced canopy openness and light penetration without adversely impacting on yield and fruit quality. Subsequent UAV-based detection under moderate versus no defoliation treatment revealed that the YOLOv8-based model achieved significant performance gains: mean average precision (mAP) increased from 0.818 to 0.884, and the F1-score improved from 0.796 to 0.842. The study contributes a novel collaborative optimization strategy that effectively mitigates occlusion issues in fruit detection. This approach demonstrates that agronomic techniques can be strategically used to enhance AI perception, offering a significant step forward in the integration of agricultural machinery and agronomy for intelligent orchard systems.

Litchi (Litchi chinensis Sonn.), a native fruit of southern China valued for its flavor and nutrition, is widely cultivated in subtropical regions (Yao et al. 2021). In May 2024, a postharvest disease was observed on ripe litchi fruits (cv. Guiwei) in Nanning, Guangxi Province, with an incidence of approximately 50% across 200 samples in each of three inspected cartons. Brown circular lesions initially appeared on the exocarp, with corresponding lesions on the endocarp. Within two days, lesions spread across the entire pericarp, typically displaying sparse mycelium at lesion centers. In severe cases, the pericarp cracked and exuded liquid. To isolate the pathogen, tissue samples (5 × 5 mm) were excised from necrotic lesion margins on the pericarps of six symptomatic litchi fruits, surface-disinfected in 1% sodium hypochlorite for 2 minutes, rinsed three times in sterile water, and plated on potato dextrose agar (PDA), and incubated at 28°C for 3 days (12-hour photoperiod). Hyphal tips were transferred to fresh PDA for purification. Ten morphologically similar isolates were obtained, with an 83% isolation frequency. On PDA plates, fungal mycelia were initially grayish-white, turning gray to dark gray, with dense, fluffy aerial hyphae. Conidiogenous cells were smooth, hyaline, cylindrical, and holoblastic. Conidia were ellipsoidal with rounded ends and thick walls; immature conidia were colorless, hyaline, and aseptate, while mature conidia were dark brown, one-septate, measuring 24.2-34.6 × 12.1-17.1 μm (n = 29). The genomic DNA from two randomly selected isolates (LC141 and LC142) was extracted using the cetyltrimethylammonium bromide (CTAB) method (Guo et al. 2000). The internal transcribed spacer (ITS) region of ribosomal DNA (rDNA), and partial translation elongation factor-1 alpha (TEF-1α), and β-tubulin (TUB) genes were amplified and sequenced using primer pairs ITS1/4 (White et al. 1990), TEF-Las-F/R (AGA CGA TCG AGA AAT TTG AGA AG/GCG AGG TAC CAG TGA TCA TGT TC), and TUB-Las-F/R (TGC CAA AAC ACA CCT GCT CCT GC/TGT AGT GAC CCT TGG CCC AGT TG), respectively. The resulting sequences (ITS: PQ835290-91; TEF-1α: PQ862852-53; TUB: PQ862854-55) showed 99-100% similarity (487/487, 512/516 bp for ITS; 293/300, 303/306 bp for TEF-1α; 416/421, 417/420 bp for TUB) to Lasiodiplodia pseudotheobromae ex-type CBS116459 sequences (EF622077, EF622057, EU673111) (Alves et al. 2008). Phylogenetic analysis of concatenated ITS, TEF-1α, and TUB sequences grouped LC141 and LC142 with L. pseudotheobromae. Based on morphological and molecular characteristics, the isolates were identified as L. pseudotheobromae (Alves et al. 2008).To verify pathogenicity, six healthy litchi fruits (cv. Guiwei) were stab-wounded and inoculated with mycelial fragments of L. pseudotheobromae isolates LC141 and LC142, with three fruits per isolate. Three control fruits were treated with sterile water. Fruits were incubated in transparent plastic boxes at 28°C. Three days post-inoculation, symptoms appeared on inoculated fruits, while controls remained asymptomatic. Experiments were repeated thrice with consistent results. To fulfill Koch's postulates, L. pseudotheobromae was re-isolated from symptomatic tissues and identified by morphology and sequencing; no fungi were isolated from controls. This is the first report of L. pseudotheobromae causing postharvest fruit rot in litchi in China, providing a foundation for developing targeted disease management strategies.

Sugars function as essential signaling molecules and metabolic substrates in plant growth, development, yield formation, and fruit quality. The aril of litchi (Litchi chinensis Sonn.) accumulates high levels of hexoses, primarily glucose and fructose; however, the molecular mechanisms underlying this process remain poorly characterized. This study aimed to systematically identify the monosaccharide transporter (MST) gene family in litchi and elucidate its role in aril sugar accumulation. Through a comprehensive analysis of the litchi genome, we identified a total of 45 LcMST genes, which were classified into seven distinct subfamilies: STP, ERD6L, PLT, INT, pGlcT, TMT, and VGT. Analysis of gene structure and conserved motifs revealed notable conservation among members within the same subfamily. Collinearity and gene duplication analyses suggested that the LcMST family expanded through both tandem and whole-genome duplication events, a process primarily governed by purifying selection. Expression profiling across diverse tissues demonstrated that LcMST genes exhibit distinct tissue-specific expression patterns. During fruit development in the hexose-dominant cultivar ‘Tianshuili’, the expression of the tonoplast monosaccharide transporter gene LcTMT1 exhibited a significant positive correlation with the accumulation of fructose, glucose, and total sugars. Heterologous functional complementation assays in yeast confirmed the ability of LcTMT1 to transport both glucose and fructose. In conclusion, this study presents the first genome-wide identification and characterization of the MST gene family in litchi, and identifies LcTMT1 as a key contributor of hexose accumulation in the aril. These findings establish a foundation for elucidating the molecular mechanisms of sugar accumulation in litchi fruit and for guiding future genetic improvement of fruit quality.

Litchi downy blight, caused by Peronophythora litchii, is a major postharvest disease that leads to severe pericarp browning and fruit decay, significantly reducing market quality. Strengthening the fruit’s innate defense systems represents a promising strategy for minimizing these losses. This study investigated the efficacy and underlying mechanisms of ethephon treatment in controlling postharvest litchi downy blight. The results showed that treatment with 400 mg·L−1 ethephon solution via a 2-min immersion significantly suppressed P. litchii infection, reduced the disease index and pericarp browning index, and enhanced the rate of ethylene production. Ethephon application notably increased 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, and the activities of key antioxidant and defense-related enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), chitinase (CHI), β-1,3-glucanase (GLU), and phenylalanine ammonia lyase (PAL). Concurrently, it up-regulated the expression of corresponding genes LcCAT, LcAPX, LcCHI, LcGLU, LcPAL. In contrast, ethephon treatment reduced the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA). In summary, ethephon treatment suppresses postharvest litchi downy blight likely through the enhancement of both antioxidant and pathogen defense capacities. These findings provide valuable insights into the potential application of ethephon for maintaining postharvest quality in litchi fruit.

Climate variability has increasingly disrupted the natural vegetative dormancy of litchi (Litchi chinensis), negatively impacting flowering, fruit set, and quality. This study evaluates the combined effect of paclobutrazol (PBZ) and micronutrients (Zinc Sulphate and Boric Acid) on the physical and biochemical quality of litchi fruits in a subtropical agro-climatic region. A factorial randomized block design was employed on 20-year-old litchi trees (cv. Dehradun) with 27 treatment combinations. Results revealed that PBZ @ 50 ppm followed by ZnSO4 @ 1.0% significantly improved fruit length, weight, pulp percentage, and juice content. The same treatment also enhanced reducing sugars, total soluble solids (TSS), and ascorbic acid content, while optimizing the TSS: acid ratio. Zinc’s role as a cofactor in carbohydrate metabolism and antioxidant enzyme activity, along with PBZ’s vegetative growth suppression, synergistically improved nutrient allocation and fruit quality. Use of 50 ppm PBZ in month of October with 1% zinc sulphate at time of panicle emergence is an integrated approach for mitigating climate-related disruptions and improving litchi productivity and nutritional value.

Development of scale-up isochoric freezing equipment for better preserving litchi fruit: Basic characteristics, aroma quality, and water status.

Enhanced litchi fruit detection and segmentation method integrating hyperspectral reconstruction and YOLOv8

The role of amino acids in delaying the pulp breakdown of litchi fruit during postharvest storage.

Physicochemical and functional properties of polysaccharides from fresh litchi fruit pulp by magnetically induced electric field.