Introduction: Wilt is a soil-borne disease caused by Fusarium that has become a serious threat to wax gourd production. Disease-resistant graft wax gourds are an effective treatment for Fusarium wilt. However, there are few reports on the defense mechanism of graft wax gourd against wilt diseases.Methods: In the present study, disease and growth indices were compared between grafted and original wax gourds after infection with Fusarium. High level of disease resistance was observed in the grafted wax gourd, with a lower disease index and low impacts on growth after infection. RNA-seq was performed to identify the differentially expressed genes (DEGs) between the adjacent treatment time points in the grafted and original wax gourds, respectively. Then a comparative temporal analysis was performed and a total of 1,190 genes were identified to show different gene expression patterns between the two wax gourd groups during Fusarium infection.Result and discussion: Here, high level of disease resistance was observed in the grafted wax gourd, with a lower disease index and low impacts on growth after infection. The DEG number was higher in grafted group than original group, and the enriched functional categories and pathways of DEGs were largely inconsistent between the two groups. These genes were enriched in multiple pathways, of which the mitogen-activated protein kinase (MAPK) signaling pathway enhanced the early defense response, and cutin, suberin, and wax biosynthesis signaling pathways enhanced surface resistance in grafted wax gourd in comparison to original group. Our study provides insights into the gene regulatory mechanisms underlying the resistance of grafted wax gourds to Fusarium wilt infection, which will facilitate the breeding and production of wilt-resistant rootstocks.

Citrus microcarpa is a popular nutritious fruit that is widely cultivated in China. In recent years, many compounds with significant pharmacological activities have been isolated successfully from the pericarp of C. microcarpa . However, to date, there are no reports on the activity of C. microcarpa pericarp against root-knot nematodes. This study used the ethanolic extract from the pericarp of Hainan C. microcarpa and the impregnation method to determine its activity on J2 Meloidogyne enterolobii specimens and on single-egg hatching. The results showed that when J2 individuals were treated with 50 mg⋅mL ^–1 of the extract, the lethal concentration 50 values after 24 and 48 hours were 17.124 and 8.858 mg⋅mL ^–1 , respectively. The mortality rate of nematodes after 48 hours of treatment was 100%, and the inhibition rate of single-egg hatching after 24 hours was 89.29%. The ethanolic extract of C. microcarpa peels showed high inhibitory and lethal activity against the M. enterolobii . The analysis of the chemical composition of the extract revealed 28 substances with insecticidal and antibacterial effects, including lignans, flavonoids, fatty acids, organic acids, terpenoids, and imidazole. The formulas of the chemical structures and pharmacological effects of these potential insecticidal and antibacterial substances were elucidated to provide a scientific basis and a theoretical reference for the use of C. microcarpa pericarps as a raw material for the development of new, natural plant nematicides.

Alpinia oxyphylla Miq. is mainly distributed in Hainan, Guangdong and Guangxi provinces of China. Between July and August 2021, a leaf spot disease was observed in Ledong, Hainan Province, China (18°70′20.50″ N, 109°25′25.47″E) on A.oxyphylla. The incidence of infected leaves ranged from 8% to 10%, and the incidence rate of infected plants was about 50%. Symptoms appeared as primary yellow-brown withered spots on the diseased leaves, which further developed into irregular red-brown spots. The center of the lesions was gray-black, and the tissue was irregularly necrotic, ruptured or perforated, and there were yellow chlorotic halos around the edges of the lesions (Figure 1A). Tissues 5 mm in diameter were taken from the junction of diseased and healthy tissue for pathogen isolation, Successively, a total of 8 isolates were obtained from the affected leaves. Three single spore isolates (YZ-HN-001, YZ-HN-043 and YZ-HN-051) were obtained and confirmed to be identical based on morphological characteristics. Therefore, the representative isolate YZ-HN-001 was selected for morphological and molecular identification. On Potato Dextrose Agar(PDA), the colony was gray-white at first and gradually turned dark green to dark brown with lead gray on the back, growth was slow, and mycelium was short and dense (Figure 1B and Figure 1C). Pycnidia were epiphyllous, globose, brown (about 120-140 µm in diameter), and conidia were elliptical, colorless, single celled and smooth (8-12×4-7 µm) (Figure 1D). Molecular identification was performed by partially sequencing the internal transcribed spacer gene (ITS), 18S rRNA gene and the actin gene (ACT) by using the primers ITS1/ITS4 (White et al. 1990), EF4/Fungi5 (Khodaparase et al. 2005) and ACT-512F/ACT-783R (Carbone and Kohn. 1999). The sequences of the amplified fragments were deposited in GenBank, the ITS sequence (ON005130, 616 bp) showed 100% identity with Phyllosticta capitalensis strain CGMCC3.14345 (JN791605.1), the 18S rRNA sequence (ON005129, 541 bp) showed 99% identity with P. capitalensis isolate MUCC0029 (AB454185.1) and the ACT sequence (ON049348, 251 bp) showed 100% identity with P. capitalensis strain DZSN202005-2 (MW533248.1). A phylogenetic analysis was conducted in MEGA X using the neighbor-joining method and showed that isolate YZ-HN-001 clustered together with P. capitalensis (Figure 2). Based on the above morphological and molecular characteristics, the isolate was determined to be P. capitalensis. Pathogenicity tests were conducted in three replicates by inoculating surface-sterilized leaves of A. oxyphylla. The leaves were wounded and inoculated with colonized PDA plugs (5×5 mm) from 15-day-old cultures. Control leaves wounded in the same way and were inoculated with sterile PDA plugs (5×5 mm). Leaves were moisturized by spraying with sterile water every three days. After 20 days at room temperature (23 to 28℃), similar symptoms were observed in the inoculated leaves as in the field (Figure 1E), but no symptoms were observed on the control leaves (Figure 1F). The same P. capitalensis was reisolated in the inoculated leaves, confirming Koch’s postulates. Phyllosticta capitalensis has been reported to cause leaf spots or black spots on various host plants around the world (Wikee et al. 2013), including on oil palm (Nasehi et al. 2020), tea plant (Cheng et al. 2019 ), and castor (Tang et al. 2020). Nevertheless, to our knowledge, this is the first report of leaf spot caused by P. capitalensis on A. oxyphylla worldwide.

Eutrema japonicum is a perennial herb belonging to the Eutrema genus in the crucifer family. In recent years, numerous substances with notable pharmacological activities have been successfully isolated from E. japonicum. Despite significant advancements in related research, the efficacy of the rhizome extract of E. japonicum against root-knot nematodes remains unknown. In this study, the rhizome extract of E. japonicum was used as raw material to demonstrate the inhibitory and nematicidal effects of the extract on Meloidogyne enterolobii. The results showed that the LC₅₀ of the E. japonicum rhizome extract on second-stage juveniles (J2s) was 69.590 mg/mL and 22.336 mg/mL at 24 h and 48 h after treatment, respectively. The mortality rate of J2s reached 88.93% at 48 h post-treatment when the concentration was 200 mg/mL, and the inhibition rate of single-egg hatching reached 88.14%. This study analyzed the chemical composition of the ethanol extract of E. japonicum, and 10 organosulfur compounds and lipid compounds with insecticidal and antibacterial effects were preliminarily screened out. Among them, sec-butyl isothiocyanate and geraniol were further investigated for their nematicidal activity, demonstrating high efficacy against M. enterolobii. Moreover, we conducted network pharmacology analysis and RT-qPCR analysis to predict the potential inhibitory mechanisms of sec-butyl isothiocyanate and geraniol on M. enterolobii. These findings offer a scientific foundation and theoretical framework for utilizing E.japonicum as a potential raw material for developing novel natural plant nematicides.

Kenaf (Hibiscus cannabinus L.), a member of the Malvaceae family, has gained increasing research interest owing to its therapeutic attributes. Among pathogens affecting tropical kenaf cultivation, Meloidogyne enterolobii is the most economically destructive disease, causing severe yield loss and quality deterioration. Consequently, the identification of M. enterolobii-resistant kenaf germplasms and the elucidation of the underlying molecular pathways are primary objectives for plant breeders. In this study, the gene encoding a TGA-like protein associated with root-knot nematode resistance was cloned from kenaf via reverse transcription polymerase chain reaction (RT-PCR) and the rapid amplification of cDNA ends (RACE), and designated as HcTGA5 gene. The full-length cDNA is 798 bp, encoding a 230-amino acid protein (GenBank accession: PZ944973). The application of phytohormones (jasmonic acid, JA; salicylic acid, SA; ethylene, ET) profoundly affected HcTGA5 gene expression with specific temporal patterns: peak expression was observed at 6 h after ET treatment, followed by 48 h after SA, and 24 h after JA treatment. HcTGA5 gene demonstrated an ‘initial upregulation followed by decline’ trend in response to ET treatment, whereas SA and JA triggered a ‘rise–fall–rise’ fluctuation. The data demonstrate the temporal modulation of HcTGA5 gene expression by phytohormones, suggesting its function in hormone-mediated defense signaling. A comparative analysis revealed markedly elevated HcTGA5 gene expression in M. enterolobii-resistant germplasms compared to susceptible ones, indicating its possible association with nematode resistance. In conclusion, HcTGA5 gene may play an integral role in kenaf’s defense against M. enterolobii. The study establishes a basis for investigating the nematode resistance mechanisms of kenaf and gives a theoretical framework for the genetic enhancement and disease management of kenaf.