Journal of Plant Pathology最新文献

Basil Downy Mildew (BDM), caused by the oomycete Peronospora belbahrii, is a major issue for sweet basil (Ocimum basilicum L.) production worldwide. Currently, the disease is mainly controlled by chemical fungicides, but the development of populations of the pathogen which are resistant to the most widely used compounds is leading to the research of alternative crop protection strategies. Therefore, in this paper, some cropping variables were tested in a field trial conducted in two consecutive years (2021 and 2022) in Northern Italy in organic farming conditions, with the overall objective to optimize basil productivity and quality and limit BDM occurrence. These include two basil varieties, two sowing densities (dense, 30 kg/ha, and sparse, 15 kg/ha), and two irrigation systems (drip and sprinkler). A higher incidence and severity of BDM in 2022 compared to 2021 was observed, mainly due to the different climatic conditions that occurred in the two years. Year 2022 was characterized by high temperatures and repeated drought phenomena that led to basil stress and BDM severe outbreak. Moreover, variety 1 (considered resistant to P. belbahrii) was confirmed to be completely resistant in 2021 but it was found to be susceptible the following year, with disease incidence and severity comparable to variety 2 (medium susceptible). No differences were detected in terms of BDM occurrence and crop yield between the two sowing densities (mean of 58.4% and 26.6% of BDM incidence and severity, respectively; mean yield 1.4 kg/m²), while it emerged that drip irrigation can be useful in reducing BDM (−23.1% BDM severity). Therefore, this study suggests that the crop protection strategies tested, even if not definitive solutions, can significantly contribute to manage BDM more effectively, while preserving basil productivity and quality.

Plants face numerous challenges in their ongoing battle against pests and diseases. Traditional protection methods often involve synthetic pesticides, which have a detrimental impact on the environment and human health. However, the quest for eco-friendly and sustainable solutions has brought surfactin into the spotlight as a promising defender of plants. Surfactin, a biometabolite produced by Bacillus spp., has gained attention due to its multifaceted properties contributing to plant defense. This review highlights the eco-friendly nature of surfactin and explores its notable functions as an antimicrobial agent, the ability to modulate plant defense mechanisms, enhance colonization and biofilm formation of antagonists, and ultimately promote plant growth. Furthermore, the environmentally friendly characteristics of surfactin, such as its biodegradability and low toxicity, make it an ideal candidate for sustainable plant protection strategies. The potential applications and challenges in utilizing surfactin as an eco-friendly defender of plants are discussed, providing insights for future research and the development of innovative and sustainable agricultural practices.

An effective tool for discovering differentially expressed genes (DEGs) related to late blight (LB) resistance is the transcriptome sequencing of potatoes. The aim of this study was to compare transcriptome expression analysis in incompatible and compatible interactions via high-throughput sequencing. Furthermore, we performed a bioinformatics analysis to screen a large number of specific transcription factors (TFs) and DEGs linked to Phytophthora infestans infection. Two locally cultivated potato varieties were chosen from evaluation assays conducted in two consecutive seasons and based on the disease severity (DS) values. These varieties were the highly resistant Jelly (HR) to P. infestans and the moderately susceptible Annabelle (MS). Ribonucleic acid-sequencing (RNA-seq) was achieved for the two varieties with their controls through the BGISEQ-500 sequencing platform. The RNA-seq analysis identified P. infestans-responsive genes and their expression in potatoes. The mechanism of the response of these cultivars to the P. infestans pathogen by TFs and DEG genes, which play an important role in defense response, was investigated. The Gene Ontology (GO) analysis classified 46,248 unigenes in the HR and 26,921 unigenes in MS into the following three categories: biological process, cellular component, and molecular functions. More genes were responsible for the cellular component category, biological process, and molecular functions in HR compared to MS. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the significantly enriched DEGs were included in the plant–pathogen interaction, biosynthesis of secondary metabolites, and ribosome. In addition, 1874 transcription factor genes belonging to 85 families were indicated in the DEGs, of which MYB and AP2-EREBP genes were the most abundant. Besides, multiple genes related to LB resistance showed differential expression during infection. It also sheds light on the molecular mechanisms behind potato resistance to P. infestans infection.

The genetic diversity of 52 Erwinia amylovora isolates from pome fruit trees with fire blight in Central and Eastern Georgia from the years 2020–2022 was examined using specific PCR and genotyping of CRISPR repeat regions 1 and 2. The analysis identified three distinct genotypes: (A, a, α), matching historical Western European strains; (A, z, α), distinctive for Georgia and differing by a three-spacer deletion in CRR2 (2034–2036); as well as novel genotype (A, ä, α), which was not observed previously. Genotypes (A, a, α) and (A, z, α) were found to coexist geographically in all four regions investigated, whereas genotype (A, ä, α) was reported only in one case in the region of Kvemo Kartli. On separate instances, multiple genotypes were detected even within the same orchard or tree, illustrating the complex genetic landscape of E. amylovora in the country.

The connection between the traditional Chinese medicinal herb Bletilla striata and microorganisms is still not well understood. Our study aimed to uncover the structure and diversity of the fungal and bacterial communities associated with B. striata. Bioinformatics, biocontrol and biochemical experiments were carried out. In terms of relative abundance of the top 15 phyla of microbial species, tenericutes in stems (58.74%) and roots (39.36%) showed the highest relative abundance, while cyanobacteria in leaves presented the most (64.53%). At the genus level, there were 32 genera of bacteria detected in three tissues. Sphingomonas showed relative abundances in leaves (41.54%) and stems (22.68%), while Paraburkholderia showed the highest relative abundance in roots (20.87%). In contrast, the dominant genera of the fungi were Melampsora (28.55–43.61%) and Cryptococcus (6.1-25.56%) among the top 15 genera of fungi species. Twenty microorganisms were obtained from roots, stems, and leaves and isolated, which also confirmed the results of the bioinformatics analysis. The isolated Bacillus velezensis exhibits the capability to enhance both the growth and nutrient accumulation of B. striata. Additionally, B. velezensis, along with its fermentation products, contributes to the improvement of antioxidant enzyme activity. Notably, there are variations in the species and abundance of microflora present in the leaves, stems, and roots of B. striata at both the phylum and genus levels. The components of the microbial flora that were isolated and identified align with the results obtained from bioinformatic analyses. It is noteworthy that B. velezensis exerts a positive impact on the increase in yield of B. striata. This work provides important insights into B. striata-associated microorganisms that are essential for promoting growth and disease resistance by revealing the complex structure and variety of fungal and bacterial communities.

In this study, the chemical compositions of rosemary (Rosmarinus officinalis Spenn.) and sweet marjoram (Origanum majorana L.) essential oils, both individually and in various blend ratios, were investigated by using Gas Chromatography-Mass Spectrometry. Their antifungal activities were also determined against the potato rubbery rot disease agent, Geotrichum candidum, under in vitro and in vivo conditions. Camphor (20.69%) and terpinen-4-ol (35.13%) were determined as primary constituents in rosemary and sweet marjoram essential oils, respectively. Sweet marjoram and rosemary essential oils completely inhibited mycelial growth of G. candidum at 55.0 and 65.0 µL/Petri concentrations, respectively. Essential oils at these concentrations were found as fungicidal. Notably, a synergistic fungicidal antifungal effects were also observed in essential oil blends. Blend of sweet marjoram and rosemary essential oil in a 3:1 ratio (O₇₅R₂₅) significantly enhanced antifungal activity at the relatively lower concentration (45.0 µL/Petri). Microscopic observations revealed structural deformations in exposed hyphae, including cytoplasmic coagulation and vacuolization. Essential oil blend (O₇₅R₂₅), sweet marjoram and rosemary essential oils completely inhibited the disease lesion caused by G. candidum on potato tubers at concentrations of 100.0, 125.0, and 150.0 µL/L air, respectively. These findings emphasized that essential oil blends of rosemary and sweet marjoram have synergistic antifungal potential and can be used as effective biofungicides against plant fungal diseases.

Abies nebrodensis is a species of fir endemic to Sicily, represented by only 30 trees in the natural population and is currently classified as critically endangered by IUCN. In such context, monitoring its health status is essential for the proper management and preservation of this species. Phytosanitary surveys of trees of the natural population of A. nebrodensis and on potted plants raised in the local forest nursery were carried out, and the phyllosphere fungal community was investigated. The health condition of trees in the natural population were fairly good, with needle reddening and blight as the most frequently observed symptoms on the foliage, while in the nursery similar disorders were registered on about the 1.3% of potted plants. Results on fungal isolations highlighted the presence of species belonging to Valsa, Cytospora (which includes anamorphs of Valsa) and Rhizosphaera genera as the most represented on both reddened and green needles; these results suggest that these fungi likely live as endophytes, resuming their growth when needles are affected by environmental stressors such as wind, hail, mechanical wounds and do not represent a biotic constraint for A. nebrodensis. The disorders observed appear mostly as a consequence of the harsh site in which the relic species lives. Together with the fungal community observed on symptomatic and healthy needles, they indicate that A. nebrodensis adapted and tolerates its altered habitat.

The African fungus Ceratocystis albifundus does not cause disease symptoms on its wide range of native woody hosts. However, on non-native Acacia mearnsii and orchard-grown Protea cynaroides, it represents an economically significant pathogen. Because previous studies exploring the biological fitness of C. albifundus were constrained by small sample sizes, we aimed to determine how commonly used measures of fitness (growth in culture, pathogenicity and sexual fertility status) vary across natural populations. For this purpose, a collection of 58 isolates originating from diverse hosts and geographic locations in South Africa were subjected to growth studies on synthetic culture medium, pathogenicity tests on A. mearnsii saplings, and sequence-based assays of fertility status. We found that these traits were generally not correlated with one another, although isolates from the Summer rainfall region and from native hosts induced significantly shorter lesions on A. mearnsii than isolates from the Winter rainfall region and from diseased A. mearnsii and orchard-grown P. cynaroides tissues. In other words, aggressiveness of C. albifundus to A. mearnsii was significantly influenced by the isolates’ geographic origin and host species, irrespective of their fertility status or growth rates. Additionally, the broad lack of correlation among growth, pathogenicity and fertility suggested that these fitness components are likely underpinned by distinct genetic and molecular mechanisms. Our study thus provides a robust foundation for further exploration of the fitness landscape in this important tree pathogen.

This research investigated the inhibitory effects of essential oils (EOs) extracted from four Citrus sinensis cultivars (Thomson navel, Jaffa sweet, Sanguine blood, and Valencia) against Alternaria spp., a pathogen affecting oranges. Among the cultivars studied, the EO from the Sanguine blood cultivar exhibited the highest antifungal activity when added into the culture medium and it was selected for further investigations. Sanguine blood EO reduced melanin in the fungal hyphae and completely inhibited vegetative growth of Alternaria species at 550–750 μg mL⁻¹ concentrations and inhibited spore germination at 800–1000 μg mL⁻¹ concentrations, which were similar to the fungicide Mancozeb. Separation of cytoplasm from cell wall, hyphal emptying, destruction of cell wall, plasma membrane, organelles such as nucleus and mitochondria, hyphal lysis and cell death were observed in all three fungal species tested. Activities of cell wall degrading enzymes produced by the pathogens were significantly reduced in the fungi treated with the EO. Reduction of the disease index was observed in all four cultivars, similar to the effect of fungicide. Gas chromatography-mass spectrometry analysis revealed presence of D-limonene, β-myrcene, and β-linalool as the main components of the EO obtained from the Sanguine blood cultivar. In conclusion, the EOs as natural plant protectants could control Alternaria spp. on orange under both in vitro and in vivo conditions.