During autumn 2014, in a commercial nursery in Liancheng, Fujian, China, 2 to 3-year-old plants of V. corymbosum showed symptoms of sudden collapse, leaf discoloration, and severe wilt associated with root and basal stem rot. Phytophthora isolates isolated from symptomatic roots and stem identified as Phytophthora cinnamomi on the basis of morphological characteristics and molecular analysis. To our knowledge, this is the first report of P.cinnamomi causing root and stem rot of V. corymbosum in China. Control methods such as fungicides application are needed to reduce this disease.
Streptomyces vinaceus strain SVFJ-07 is a biocontrol bacterium employed to control anthracnose disease caused by Colletotrichum gloeosporioides in Chinese orchids. This study investigated the mechanism of strain SVFJ-07-induced stomatal immunity-related closure in preventing the infection of anthracnose disease. After the foliar application of strain SVFJ-07, we analyzed the differential patterns of stomatal opening in Chinese orchids and measured the hormone levels of abscisic acid (ABA) and salicylic acid (SA). RNA sequencing (RNA-seq) was utilized to examine the differential expression of genes involved in SA and ABA signal transduction and disease resistance genes, which were induced by strain SVFJ-07. The results demonstrated that strain SVFJ-07 inhibited the infection of pathogens by inducing stomatal closure. Compared with the control group, the foliar application of strain SVFJ-07 significantly reduced stomatal length, width, and aperture. Furthermore, orchid plants treated with strain SVFJ-07 and infected with C. gloeosporioides exhibited elevated levels of endogenous ABA and SA, indicating that strain SVFJ-07 enhanced stomatal immunity and disease resistance in these plants. The transcriptome analysis revealed the upregulation of genes associated with stomatal immunity, particularly those involved in plant–pathogen interactions, peroxisome metabolism, plant hormone signaling, and mitogen-activated protein kinase (MAPK) signaling pathways. These findings confirmed that the induction of SVFJ-07 promoted stomatal closure to resist the infection of C. gloeosporioides and induced complex transcriptome-wide changes. Further investigation of the differentially expressed genes enhanced our understanding of the resistance mechanisms induced by S. vinaceus strain SVFJ-07.
The flower thrips, Frankliniella intonsa, is a major pest threatening citrus production. However, chemical control remains the primary management measure, which poses significant risks on ecosystems. Hence, it is urgent to prioritize more eco-friendly measures to efficiently control thrips. The ladybird, Cheilomenes sexmaculata, is a predominant natural enemy in the local citrus agroecosystem and could play a key role in suppressing thrips in agricultural landscapes. Although some ladybirds are known to be attracted to herbivore-induced plant volatiles (HIPVs), little is known about the specific attractive compounds and the effect of F. intonsa-infested lemon plants on the predatory response of C. sexmaculata. Here, we studied the chemical interaction between F. intonsa, C. sexmaculata, and lemon plants. In dual-choice behavioral assays, C. sexmaculata adults significantly preferred volatiles from F. intonsa-infested plants over those from healthy plants. Volatile collection and analysis identified six monoterpenes, five of which (α-pinene, β-pinene, sabinene, myrcene, and eucalyptol) individually attracted C. sexmaculata at specific concentrations. Moreover, a blend of these five compounds, formulated at their optimal attractive concentrations, elicited a stronger attraction in C. sexmaculata than individual compounds, indicating a synergistic interaction. This attractive blend can thus be used to develop a kairomone-based lure to enhance biological control and to complement existing integrated pest management approaches against thrips in lemon agroecosystems.
Maize (Zea mays L.) is a major economic crop highly susceptible to Colletotrichum graminicola, the causal agent of anthracnose leaf blight, which causes substantial annual yield losses. This fungal pathogen employs numerous effectors to manipulate plant immunity, yet the functions of many secreted proteins during biphasic infection remain poorly characterized. In this study, we identified CgMas2, a candidate secreted protein in C. graminicola and a homolog of Magnaporthe oryzae MoMas2. Deletion of CgMAS2 in the wild-type strain CgM2 did not affect fungal vegetative growth or conidial morphology but significantly impaired virulence on maize leaves. Leaf sheath infection assays revealed that CgMas2 is required for biotrophic invasive hyphal growth, as the mutant showed defective spreading of invasive hyphae to adjacent cells. Subcellular localization analysis indicated that CgMas2 localizes to the cytoplasm of conidia and to the primary infection hyphae. Furthermore, DAB staining demonstrated that disrupt of CgMAS2 leads to host reactive oxygen species (ROS) accumulation. Comparative transcriptome analysis of maize infected with ΔCgmas2 versus CgM2 revealed enrichment of GO terms related to peroxisome and defense response, along with up-regulation of benzoxazinoid biosynthesis genes (benzoxazinone biosynthesis 3, 4 and 5) at 60 h post-inoculation (hpi). Conversely, six ethylene-responsive transcription factors (ERF2, ERF3, ERF56, ERF112, ERF115 and ERF118) involved in ethylene signaling pathways were down-regulated at 96 hpi. These expression patterns were validated by RT-qPCR. Collectively, our results demonstrate that CgMas2 not only promotes invasive hyphal growth during the biotrophic stage but may also modulate phytohormone signaling and defense compound biosynthesis during the necrotrophic phase of infection.