Jiabao Wang

Musa dulongjiangensis (Musaceae), a new species of the genus Musa endemic to Yunnan, southwestern China, is described and illustrated in this study. This new species is morphologically similar to M. puspanjaliae , but can be clearly distinguished by a combination of morphological characters. Its female bud bracts are dark purple externally and purple internally, with 6–7 basal female flowers arranged in two rows; the base of the compound tepal bears distinct and dense red stripes, the ovary is pale green and glabrous. The male bud bracts are consistent in color with female bracts, dark purple externally and purple internally, and are non-revolute before abscission. Each bract bears approximately twenty male flowers arranged in two rows, with pinkish-purple anther lobes. The fruit bunch is lax, consisting of upward-curving fruits. Typically, each bunch possesses eight hands, with 6–7 fruits per hand, and the pedicels are obviously developed.

While mutagenesis breeding has been widely applied in major crops, its implementation in tropical horticultural species remains limited. In this study, we established a pingyangmycin-induced mutagenesis system using in vitro –cultured embryogenic callus of litchi. Treatment with gradient concentrations of pingyangmycin (0–40 mg/L) revealed an inverse relationship between chemical dosage and cell viability, with somatic embryogenesis completely inhibited at 40 mg/L. Whole-genome resequencing of treated callus identified 307,629 high quality somatic mutations (255,721 SNVs and 51,908 indels), with the 20 mg/L treatment group exhibiting the highest number of mutations. Further resequencing of 40 regenerated mutant lines from the cultivars ‘Feizixiao’ and ‘Lingnan15’ revealed 1,703,663 and 1,281,489 somatic variants, respectively, corresponding to mutation frequencies of 1.8×10 ^-4 per site and 1.4×10 ^-4 per site, both markedly exceeding typical EMS-induced rates in crops. Transition mutations predominated, accounting for 77% of total single-nucleotide substitutions. Short indels (<3 bp) comprised over 70% of all insertion–deletion events, indicating pingyangmycin’s propensity to induce base substitutions and small indels via oxidative and double-strand break repair pathways. The regenerated mutant plants exhibited substantial leaf morphological variation, confirming effective mutagenic diversification. Collectively, this study provides the first evidence of pingyangmycin’s mutagenic efficacy in litchi, establishes a reliable system for mutant library construction, and delivers valuable genetic resources for functional genomics and molecular breeding applications.

Litchi chinensis var. fulvosus is an important wild litchi resource in Yunnan, China, valued for favorable agronomic traits such as early flowering, early ripening, multiple flowering cycles, and high fruit-setting ability. However, its genetic diversity and population structure remain poorly understood. In this study, 192 accessions were collected from ten counties in Yunnan Province to evaluate their geographic distribution, leaf phenotypic variation, molecular diversity, population structure, and core collection composition. Eight descriptive leaf traits, nine quantitative leaf traits, and ISSR genotyping data from seven primers were analyzed. The accessions were distributed across an altitudinal range of 169–1470 m, with clear habitat differentiation among trees of different ages. Morphological analysis revealed substantial leaf variation, with mean diversity indices of 1.19 for descriptive traits and 2.76 for quantitative traits. ISSR analysis generated 49 scorable bands, of which 34 were polymorphic, corresponding to a polymorphism rate of 68.45%. The mean Shannon–Wiener diversity index was 0.3101, indicating detectable but relatively limited molecular diversity. Integrated phenotypic and molecular analyses divided the germplasm into two subpopulations. A core collection comprising 30 accessions (about 15% of the initial population) showed the best balance between sampling efficiency and diversity retention. These results provide a practical basis for the conservation, evaluation, and efficient utilization of L. chinensis var. fulvosus genetic resources and will support breeding and genetic improvement of litchi.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a vital exogenous auxin for the induction and proliferation of litchi embryogenic callus. At present, its molecular regulation mechanism remains unclear. In this study, transcriptome sequencing samples were selected based on different cell growth phenotypes observed in ‘Feizixiao’ litchi embryogenic callus cultured in liquid medium with or without 2,4-D. By integrating transcriptome profiling with weighted gene co-expression network analysis (WGCNA), we identified key genes and signaling pathways dynamically responsive to 2,4-D concentration changes. We identified 558 commonly differentially expressed genes (DEGs), of which 117 were up-regulated and 387 were down-regulated; functional enrichment analysis revealed significant enrichment in the “plant hormone signal transduction” and “phenylpropanoid biosynthesis” pathways. In the former pathway, genes such as AUX28, GH3.17, GH3.6, and ARR5 were up-regulated; in the latter, by comparison, β-glucosidase 47 and Peroxidase 61 exhibited increased expression levels induced by 2,4-D. Furthermore, among these DEGs, 57 transcription factors belonged to 24 families. Notably, VRN1, FEZ, and DOF5.4 were significantly and rapidly induced by 2,4-D. WGCNA results demonstrated a significant positive correlation between the yellow module and 2,4-D treatment. Small heat shock protein (sHSP) genes constituted the core hub genes in the yellow module. Through Venn analysis of DEGs and key modules, 38 cross-genes were identified, of which non-specific lipid-transfer protein-like genes (nsLTP) were found to be specifically up-regulated without 2,4-D. The transcription factors and genes identified work in synergy to ensure the formation and sustained proliferation of embryogenic callus by precisely regulating the dynamic balance of auxin and cytokinin within cells and maintaining the stability of cell structure. Our findings provide a crucial theoretical foundation for understanding the molecular mechanism of 2,4-D in regulating litchi embryogenic callus proliferation.

The online version contains supplementary material available at 10.1186/s12870-026-08499-6.

Durian (Durio zibethinus) is an economically important tropical fruit endemic to Southeast Asia. Hainan is a new region for durian cultivation. Foliar diseases of durian were common at all durian orchards during field surveys carried out from October 2023 to October 2024 in Hainan, China. In this study, Fusarium species associated with durian foliar disease in Hainan (China) were studied based on multilocus phylogenetic analyses using translation elongation factor 1-α (tef1), partial RNA polymerase second largest subunit (RPB2), and calmodulin (CaM). Six Fusarium species including F. pernambucanum, F. sulawesiense, F. hainanense, F. irregulare, F. mangiferae and F. concentricum were identified. Pathogenicity tests showed that all six species were pathogenic to detached wounded and unwounded durian leaves except F. irregulare, which only induced visible symptoms on wounded durian leaves. The findings from this study expand the pathogenic fungal species on durian as this is the first report of these Fusarium spp. causing durian leaf disease worldwide.

Pericarp browning of postharvest litchi is a significant obstacle to the industry’s high-quality development. Water loss from the pericarp is a key factor triggering browning, but the regulatory mechanism of water metabolism and its relationship with browning remain unclear. In this study, we found that aquaporin activity inhibitors (HgCl2) can delay both water loss and browning in litchi. LcPIP2;4, a plasma membrane intrinsic protein (PIP) family member exhibiting high expression in the litchi pericarp and the greatest water transport activity, is significantly downregulated during water loss and browning. Further analysis revealed that HgCl₂ suppresses both the expression and water transport activity of LcPIP2;4, indicating a close association with the observed browning phenotype. By constructing transient overexpression fruits and transgenic callus tissues of LcPIP2;4 and measuring the water loss rate and browning index, we confirmed that LcPIP2;4 positively regulates water loss and browning in litchi. Through weighted gene co-expression network, LcPIP2;4 promoter sequence, and Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) analysis, we identified 10 potential interacting transcription factors. Yeast one-hybrid, dual-luciferase reporter assay, chromatin immunoprecipitation analysis, and electrophoretic mobility shift assay confirmed that LcMYB306 specifically binds to the LcPIP2;4 promoter. In LcMYB306 overexpressing fruits and embryogenic callus, LcPIP2;4 expression was suppressed, resulting in delayed water loss and browning. In contrast, in CRISPR/Cas9-edited LcMYB306 callus, LcPIP2;4 expression was upregulated, and water loss and browning were accelerated, confirming that LcMYB306 negatively regulates this process. This study demonstrates that LcMYB306 delays postharvest water loss and browning in litchi by repressing LcPIP2;4 transcriptionally expression. It provides a theoretical foundation and key target gene for developing litchi varieties resistant to browning.