Plant Pathology Journal最新文献

Colletotrichum gloeosporioides (Cg), Pestalotiopsis sp. (Ps), Fusarium oxysporum (Fo), and Fusarium proliferatum (Fp) are pathogens that cause various diseases of Cymbidium kanran. Species identification based on the morphological characteristics of pathogen-infected orchids is very complex and difficult; therefore, specific and reliable diagnostic methods are needed. Here, we developed a multiplex polymerase chain reaction (PCR) assay for simultaneous detection of Cg, Ps, Fo, and Fp. Four pairs of pathogen-specific primers were designed based on the internal transcribed spacer sequences of each pathogen, generating fragments of 480, 407, 321, and 279 bp, respectively. The multiplex PCR assay using these four pairs of mixed primers effectively detected the four pathogens simultaneously, with a sensitivity of 0.1 ng genomic DNA/pathogen. Application of the optimized multiplex PCR assay to symptomatic C. kanran leaf samples effectively detected single or multiple pathogens. These results indicate that the multiplex PCR developed in this study is not only a rapid and reliable method for detecting four problematic pathogens in C. kanran, but also serves as a very useful tool for early diagnosis.

In 2022, citrus fruits were the second most widely produced fruit globally, highlighting their significant role in the fruit industry. However, due to their clonal propagation, these fruits are highly susceptible to viral infections, posing challenges for growers. In response to the booming nursery market, the Korean plant quarantine station reported over 80 million sapling stocks, with 15% being discarded after rigorous inspection due to contamination or disease. As the global nursery trade continues to expand, there is an urgent need for a fast and accurate diagnostic tool to ensure the health of plant stocks. In this study, we developed a TaqMan-based real-time reverse transcription-quantitative PCR assay specifically designed to detect two critical citrus viruses: citrus psorosis virus and citrus leprosis virus C. Our assay demonstrated the capability to detect virus sequences with as few as 30 copies, maintaining high PCR efficiency with RNA extracted from both twig and leaf tissues. Additionally, we incorporated an artificial sequence into the positive controls, which effectively served as a marker for detecting potential sample contamination. This comprehensive diagnostic system promises to enhance plant quarantine measures and phytosanitation practices, providing a reliable and efficient solution to safeguard citrus crops from viral threats.

Endophytic bacteria residing within plant seeds are increasingly recognized for their potential to enhance plant growth and provide biocontrol against pathogens. Despite this, seed-borne endophytes remain underexplored in many crops, including tomato. In this study, we isolated and characterized bacterial endophytes from tomato seeds and evaluated their plant growth-promoting traits and antifungal activities. The taxonomic analysis of the Hawaii 7996 tomato seed endophyte collection revealed a diverse community, predominantly from the phylum Bacillota, with Paenibacillaceae and Bacillaceae as the most abundant families. Among the 35 unique strains identified, 19 produced indole-3-acetic acid, four exhibited siderophore production, and 12 could solubilize phosphate. These traits contribute to growth promotion and disease suppression in plants. In the plant growth promotion assay, several bacterial strains, notably Streptomyces olivaceus (BHM1), Streptomyces variegatus (BHM3), Bacillus stercoris (BHR2), and Moraxella osloensis (YHT4-1), demonstrated significant potential for tomato cultivation by positively affecting fresh weight, stem length, and root length. These strains consistently promoted growth across all three parameters evaluated in this study. Furthermore, several strains exhibited strong antifungal activity against major tomato pathogens, including Fusarium oxysporum race 1 and 2, and Botrytis cinerea. Notably, Bacillus subtilis (BHN1), Bacillus stercoris (BHR2), and Paenibacillus peoriae (YHR2-1) showed broad-spectrum antifungal efficacy. Our findings highlight the potential of seed-associated endophytic bacteria as growth promoters and biological control agents, offering promising avenues for sustainable agricultural practices.

Transcription factors (TFs) regulate gene expression by binding to DNA. The NAC gene family in plants consists of crucial TFs that influence plant development and stress responses. The whole genome of Capsicum annuum shows over 100 NAC genes (CaNAC). Functional characteristics of the most CaNAC TFs are unknown. In this study, we identified CaNAC4, a novel NAC TF in C. annuum. CaNAC4 expression increased after inoculation with the pathogens, Xanthomonas axonopodis pv. vesicatoria race 3 and X. axonopodis pv. glycines 8ra, and following treatment with the plant hormones, salicylic acid and abscisic acid. We investigated the functional characteristics of the CaNAC4 gene and its roles in salt tolerance and anti-pathogen defense in transgenic Nicotiana benthamiana. For salt stress analysis, the leaf discs of wild-type and CaNAC4-transgenic N. benthamiana plants were exposed to different concentrations of sodium chloride. Chlorophyll loss was more severe in salt stress-treated wild-type plants than in CaNAC4-transgenic plants. To analyze the role of CaNAC4 in anti-pathogen defense, a spore suspension of Botrytis cinerea was used to infect the leaves. The disease caused by B. cinerea gradually increased in severity, and the symptoms were clearer in the CaNAC4-transgenic lines. We also investigated hypersensitive response (HR) in CaNAC4-transgenic plants. The results showed a stronger HR in wild-type plants after infiltration with the apoptosis regulator, BAX. In conclusion, our results suggest that CaNAC4 may enhance salt tolerance and act as a negative regulator of biotic stress in plants.

Bacterial wilt caused by Ralstonia solanacearum is a destructive disease that affects potato production, leading to severe yield losses. Currently, little is known about the changes in the assembly and functional adaptation of potato rhizosphere microbial communities during different stages of R. solanacearum infection. In this study, using amplicon and metagenomic sequencing approaches, we analyzed the changes in the composition and functions of bacterial and fungal communities in the potato rhizosphere across four stages of R. solanacearum infection. The results showed that R. solanacearum infection led to significant changes in the composition and functions of bacterial and fungal communities in the potato rhizosphere, with various microbial properties (including α,β-diversity, species composition, and community ecological functions) all being driven by R. solanacearum infection. The relative abundance of some beneficial microorganisms in the potato rhizosphere, including Firmicutes, Bacillus, Pseudomonas, and Mortierella, decreased as the duration of infection increased. Moreover, the related microbial communities played a significant role in basic metabolism and signal transduction; however, the functions involved in soil C, N, and P transformation weakened. This study provides new insights into the dynamic changes in the composition and functions of potato rhizosphere microbial communities at different stages of R. solanacearum infection to adapt to the growth promotion or disease suppression strategies of host plants, which may provide guidance for formulating future strategies to regulate microbial communities for the integrated control of soil-borne plant diseases.

Lots of progress have been made about pathogen system of Hibiscus rosa-sinensis and hibiscus chlorotic ringspot virus (HCRSV), however, interactions between H. rosa-sinensis and HCRSV remain largely unknown. Hereon, firstly, HCRSV infection in H. rosa-sinensis from Zhangzhou city of China was confirmed by traditional electron microscopy, modern reverse transcription polymerase chain reaction and RNA-seq methods. Secondly, sequence feature analysis showed the full-length sequence of HCRSV-ZZ was 3,909 nucleotides (nt) in length and had a similar genomic structure with other carmovirus. It contains a 5' untranslated region (UTR), followed by seven open reading frames encoding for P28, P23, P81, P8, P9, P38, and P25, and the last a 3-terminal UTR. Thirdly, HCRSV- ZZ-derived vsiRNAs were identified and characterized for the first time from disease H. rosa-sinensis through sRNA-seq to reveal interactions between pathogen ant plant host. It was shown that the majority of HCRSV-ZZ-derived vsiRNAs were 21 nt, 22 nt, and 20 nt, with 21 nt being most abundant. The 5'-terminal nucleotide of HCRSV-ZZ vsiRNAs preferred U and C. HCRSV-ZZ vsiRNAs derived predominantly (72%) from the viral genome positive-strand RNA. The distribution of HCRSV-ZZ vsiRNAs along the viral genome is generally even, with some hot spots and cold spots forming in local regions. These hot spots and cold spots could be corresponded to the regions of stem loop secondary structures forming in HCRSV-ZZ genome by nucleotide paring. Taken together, our findings certify HCRSV infection in H. rosa-sinensis and provide an insight into interaction between HCRSV and H. rosa-sinensis and contribute to the prevention and treatment of this virus.

Chili pepper anthracnose, caused by Colletotrichum spp., is a significant biotic stress affecting chili fruits globally. While fungicide application is commonly used for disease management due to its efficiency and costeffectiveness, excessive use poses risks to human health and the environment. Botanical fungicides offer advantages such as rapid degradation and low toxicity to mammals, making them increasingly popular for sustainable plant disease control. This study investigated the antifungal properties of Cestrum tomentosum L.f. crude extracts (CTCE) against Colletotrichum scovillei. The results demonstrated that CTCE effectively inhibited conidia germination and germ tube elongation at 40 µg/ml concentrations. Moreover, CTCE exhibited strong antifungal activity against C. scovillei mycelial growth, with an EC50 value of 18.81 µg/ml. In vivo experiments confirmed the protective and curative effects of CTCE on chili pepper fruits infected with C. scovillei. XTT analysis showed that the CTCE could significantly inhibit the cell viability of C. scovillei. Mechanistic studies revealed that CTCE disrupted the plasma membrane integrity of C. scovillei and induced the accumulation of reactive oxygen species in hyphal cells. These findings highlight CTCE as a promising eco-friendly botanical fungicide for managing C. scovillei infections in chili peppers.

A large number of species in the genus Colletotrichum have been reported as causal agents of anthracnose on crops and wild plants in Korea. Many Colletotrichum isolates from the country preserved in the Korean Agricultural Culture Collection (KACC) were previously identified based on host plants and morphological characteristics, and it may lead to species misidentification. Thus, accurate fungal species identification using multilocus sequence analyses is essential for understanding disease epidemiology and disease management strategies. In this study, combined DNA sequence analyses of internal transcribed spacer, gapdh, chs-1, his3, act, tub2, and gs were applied to re-identify 27 Colletotrichum isolates in KACC. The phylogenetic analyses showed that the isolates resulted in 11 known species, they belong to the C. dematium species complex (C. hemerocallidis, C. jinshuiense, and C. spinaciae), the C. magnum complex (C. kaifengense and C. cf. ovatense), the C. orchidearum complex (C. cattleyicola, C. plurivorum, C. reniforme, and C. sojae) and the C. orbiculare complex (C. malvarum and C. orbiculare). Of them, C. cattleyicola, C. hemerocallidis, C. kaifengense, and C. reniforme were unrecorded species in Korea. In the view of host-fungus combinations, 10 combinations are newly reported in the world and 12 are new reports in Korea, although their pathogenicity on the host was not confirmed.

Arabidopsis MORC1 (Microrchidia) is required for multiple levels of immunity. We identified 14 MORC1-interacting proteins (MIPs) via yeast two-hybrid screening, eight of which have confirmed or putative nuclear-associated functions. While a few MIP mutants displayed altered bacterial resistance, MIP13 was unusual. The MIP13 mutant was susceptible to Pseudomonas syringae, but when combined with morc1/2, it regained wild-type resistance; notably, morc1/2 is susceptible to the same pathogen. MIP13 encodes MED9, a mediator complex component that interfaces with RNA polymerase II and transcription factors. Expression analysis of defense genes PR1, PR2, and PR5 in response to avirulent P. syringae revealed that morc1/2 med9 expressed these genes in a slow but sustained manner, unlike its lower-order mutants. This expression pattern may explain the restored resistance and suggests that the interplay of MORC1/2 and MED9 might be important in curbing defense responses to maintain fitness. Indeed, repeated challenges with avirulent P. syringae triggered significant growth inhibition in morc1/2 med9, indicating that MED9 and MORC1 may play an important role in balancing defense and growth. Furthermore, the in planta interaction of MED9 and MORC1 occurred 24 h, not 6 h, postinfection, suggesting that the interaction functions late in the defense signaling. Our study reveals a complex interplay between MORC1 and MED9 in maintaining an optimal balance between defense and growth in Arabidopsis.

Pectobacterium is a major bacterial causal agent leading to soft rot disease in host plants. With the Arabidopsis-Pectobacterium pathosystem, we investigated the function of an Arabidopsis thaliana WRKY55 during defense responses to Pectobacterium carotovorum ssp. carotovorum (Pcc). Pcc-infection specifically induced WRKY55 gene expression. The overexpression of WRKY55 was resistant to the Pcc infection, while wrky55 knockout plants compromised the defense responses against Pcc. WRKY55 expression was mediated via Arabidopsis COI1-dependent signaling pathway showing that WRKY55 can contribute to the gene expression of jasmonic acid-mediated defense marker genes such as PDF1.2 and LOX2. WRKY55 physically interacts with Arabidopsis ORA59 facilitating the expression of PDF1.2</i. Our results suggest that WRKY55 can function as a positive regulator for resistance against Pcc in Arabidopsis.