Logrank test and Interval Overlap Test for Bactericera cockerelli (Hemiptera: Triozidae) under different fertilization treatments for 7705 tomato hybrid.

It is known that some nutrients can have both negative and positive effects on some populations of insects. To test this, the Logrank test and the Interval Overlap Test were evaluated for two crop cycles (February-May and May-August) of the 7705 tomato hybrid, and the effect on the psyllid, Bactericera cockerelli (Sulc.) (Hemiptera: Triozidae), was examined under greenhouse conditions. Tomato plants were in polythene bags and irrigated with the following solutions: T1-Steiner solution, T2-Steiner solution with nitrogen reduced to 25%, T3-Steiner solution with potassium reduced to 25%, and T4-Steiner solution with calcium reduced to 25%. In the Logrank test, a significant difference was found when comparing the survival parameters of B. cockerelli generated from the treatment cohorts: T1-T2; T1-T3; T1-T4; T2-T3; and T3-T4, while no significant differences were found in the T2-T4 comparison in the February-May cycle. In the May-August cycle, significant differences were found when comparing the survival parameters generated from the treatment cohorts: T1-T2; T1-T3; and T1-T4, while no significant differences were found in the T2-T3; T2-T4; and T3-T4 comparisons of survival parameters of B. cockerelli fed with the 7705 tomato hybrid. Also, the Interval Overlap Test was done on the treatment cohorts (T1, T2, T3, and T4) in the February-May and May-August cycles. T1 and T2 compare similarly in both cycles when feeding on the treatments up to 36 d. Similarly, in T1 and T3, the behavior of the insect is similar when feeding on the treatments up to 40 and 73 d, respectively. Comparisons T2-T3 and T2-T4 are similar when feeding on both treatments up to 42, 38 and 37, 63 d, respectively. Finally, the T3-T4 comparison was similar when feeding in both treatments up to 20 and 46 d, respectively.

Antifungal Effect of Copper Nanoparticles against Fusarium kuroshium, an Obligate Symbiont of Euwallacea kuroshio Ambrosia Beetle.

Copper nanoparticles (Cu-NPs) have shown great antifungal activity against phytopathogenic fungi, making them a promising and affordable alternative to conventional fungicides. In this study, we evaluated the antifungal activity of Cu-NPs against Fusarium kuroshium, the causal agent of Fusarium dieback, and this might be the first study to do so. The Cu-NPs (at different concentrations) inhibited more than 80% of F. kuroshium growth and were even more efficient than a commercial fungicide used as a positive control (cupric hydroxide). Electron microscopy studies revealed dramatic damage caused by Cu-NPs, mainly in the hyphae surface and in the characteristic form of macroconidia. This damage was visible only 3 days post inoculation with used treatments. At a molecular level, the RNA-seq study suggested that this growth inhibition and colony morphology changes are a result of a reduced ergosterol biosynthesis caused by free cytosolic copper ions. Furthermore, transcriptional responses also revealed that the low- and high-affinity copper transporter modulation and the endosomal sorting complex required for transport (ESCRT) are only a few of the distinct detoxification mechanisms that, in its conjunction, F. kuroshium uses to counteract the toxicity caused by the reduced copper ion.

Characterization of the Exo-Metabolome of the Emergent Phytopathogen Fusarium kuroshium sp. nov., a Causal Agent of Fusarium Dieback.

Fusarium kuroshium is the fungal symbiont associated with the ambrosia beetle Euwallacea kuroshio, a plague complex that attacks avocado, among other hosts, causing a disease named Fusarium dieback (FD). However, the contribution of F. kuroshium to the establishment of this disease remains unknown. To advance the understanding of F. kuroshium pathogenicity, we profiled its exo-metabolome through metabolomics tools based on accurate mass spectrometry. We found that F. kuroshium can produce several key metabolites with phytotoxicity properties and other compounds with unknown functions. Among the metabolites identified in the fungal exo-metabolome, fusaric acid (FA) was further studied due to its phytotoxicity and relevance as a virulence factor. We tested both FA and organic extracts from F. kuroshium at various dilutions in avocado foliar tissue and found that they caused necrosis and chlorosis, resembling symptoms similar to those observed in FD. This study reports for first-time insights regarding F. kuroshium associated with its virulence, which could lead to the potential development of diagnostic and management tools of FD disease and provides a basis for understanding the interaction of F. kuroshium with its host plants.

Molecular evidence of the avocado defense response to Fusarium kuroshium infection: a deep transcriptome analysis using RNA-Seq.

Fusarium kuroshium is a novel member of the Ambrosia Fusarium Clade (AFC) that has been recognized as one of the symbionts of the invasive Kuroshio shot hole borer, an Asian ambrosia beetle. This complex is considered the causal agent of Fusarium dieback, a disease that has severely threatened natural forests, landscape trees, and avocado orchards in the last 8 years. Despite the interest in this species, the molecular responses of both the host and F. kuroshium during the infection process and disease establishment remain unknown. In this work, we established an in vitro pathosystem using Hass avocado stems inoculated with F. kuroshium to investigate differential gene expression at 1, 4, 7 and 14 days post-inoculation. RNA-seq technology allowed us to obtain data from both the plant and the fungus, and the sequences obtained from both organisms were analyzed independently. The pathosystem established was able to mimic Fusarium dieback symptoms, such as carbohydrate exudation, necrosis, and vascular tissue discoloration. The results provide interesting evidence regarding the genes that may play roles in the avocado defense response to Fusarium dieback disease. The avocado data set comprised a coding sequence collection of 51,379 UniGenes, from which 2,403 (4.67%) were identified as differentially expressed. The global expression analysis showed that F. kuroshium responsive UniGenes can be clustered into six groups according to their expression profiles. The biologically relevant functional categories that were identified included photosynthesis as well as responses to stress, hormones, abscisic acid, and water deprivation. Additionally, processes such as oxidation-reduction, organization and biogenesis of the cell wall and polysaccharide metabolism were detected. Moreover, we identified orthologues of nucleotide-binding leucine-rich receptors, and their possible action mode was analyzed. In F. kuroshium, we identified 57 differentially expressed genes. Interestingly, the alcohol metabolic process biological category had the highest number of upregulated genes, and the enzyme group in this category may play an important role in the mechanisms of secondary metabolite detoxification. Hydrolytic enzymes, such as endoglucanases and a pectate lyase, were also identified, as well as some proteases. In conclusion, our research was conducted mainly to explain how the vascular tissue of a recognized host of the ambrosia complex responds during F. kuroshium infection since Fusarium dieback is an ambrosia beetle-vectored disease and many variables facilitate its establishment.

Design of a diagnostic system based on molecular markers derived from the ascomycetes pan-genome analysis: The case of Fusarium dieback disease.

A key factor to take actions against phytosanitary problems is the accurate and rapid detection of the causal agent. Here, we develop a molecular diagnostics system based on comparative genomics to easily identify fusariosis and specific pathogenic species as the Fusarium kuroshium, the symbiont of the ambrosia beetle Euwallaceae kuroshio Gomez and Hulcr which is responsible for Fusarium dieback disease in San Diego CA, USA. We performed a pan-genome analysis using sixty-three ascomycetes fungi species including phytopathogens and fungi associated with the ambrosia beetles. Pan-genome analysis revealed that 2,631 orthologue genes are only shared by Fusarium spp., and on average 3,941 (SD ± 1,418.6) are species-specific genes. These genes were used for PCR primer design and tested on DNA isolated from i) different strains of ascomycete species, ii) artificially infected avocado stems and iii) plant tissue of field-collected samples presumably infected. Our results let us propose a useful set of primers to either identify any species from Fusarium genus or, in a specific manner, species such as F. kuroshium, F. oxysporum, and F. graminearum. The results suggest that the molecular strategy employed in this study can be expanded to design primers against different types of pathogens responsible for provoking critical plant diseases.

Differential Susceptibility of Bagrada hilaris (Hemiptera: Pentatomidae) to Different Species of Fungal Pathogens.

Bagrada hilaris Burmeister (Hemiptera: Pentatomidae) is a pest of Palearctic origin. Its presence in the United States was first reported in 2008 and in Mexico in 2014; it affects brassica crops. There are practically no reports of natural enemies of B. hilaris in America. Entomopathogenic fungi are strong candidates for microbial control of this pest. Evaluating the susceptibility of this pest to fungi that are native to the region where they will be used is a sensible first step to finding candidate biological control agents. The aim of our research was to select potential microbial agents to control B. hilaris. Eleven isolates of Beauveria bassiana, Beauveria pseudobassiana, Metarhizium anisopliae, and Isaria fumosorosea were evaluated to determine the susceptibility of B. hilaris. Isolates of B. bassiana caused the highest mortality due to infection (100%) compared with the other isolates. The I. fumosorosea isolate caused the lowest percent mortality (56%). The two B. bassiana isolates Bb88 and AP3 were more virulent than M. anisopliae isolate Ma129. The sex of the insect had no effect on infection levels achieved by B. bassiana isolates Bb88 and AP3. The results of our study contribute valuable information for the development of fungal species with potential to manage B. hilaris populations. Field studies are the next step in order to develop these isolates as biological control agents of B. hilaris.

Impact of Rearing Conditions on the Ambrosia Beetle's Microbiome.

Ambrosia beetles, along with termites and leafcutter ants, are the only fungus-farming lineages within the tree of life. Bacteria harbored by ambrosia beetles may play an essential role in the nutritional symbiotic interactions with their associated fungi; however, little is known about the impact of rearing conditions on the microbiota of ambrosia beetles. We have used culture-independent methods to explore the effect of rearing conditions on the microbiome associated with Xyleborus affinis, Xyleborus bispinatus, and Xyleborus volvulus, evaluating different media in laboratory-controlled conditions and comparing wild and laboratory conditions. Our results revealed that rearing conditions affected the fungal and bacterial microbiome structure and had a strong influence on bacterial metabolic capacities. We propose that the rearing conditions influence the ambrosia-associated fungal and bacterial communities. Furthermore, bacterial microbiome flexibility may help beetles adapt to different substrates.

Draft Genome Sequence of the Phytopathogenic Fungus Fusarium euwallaceae, the Causal Agent of Fusarium Dieback.

Here, we report the genome of Fusarium euwallaceae strain HFEW-16-IV-019, an isolate obtained from Kuroshio shot hole borer (a Euwallacea sp.). These beetles were collected in Tijuana, Mexico, from elm trees showing typical symptoms of Fusarium dieback. The final assembly consists of 287 scaffolds spanning 48,274,071 bp and 13,777 genes.