Antifungal Activity of Copper Oxide Nanoparticles against Root Rot Disease in Cucumber.

Metal oxide nanoparticles have recently garnered interest as potentially valuable substances for the management of plant diseases. Copper oxide nanoparticles (Cu2ONPs) were chemically fabricated to control root rot disease in cucumbers. A scanning electron microscope (SEM), X-ray diffraction (XRD) and photoluminescence (PL) were employed to characterize the produced nanoparticles. Moreover, the direct antifungal activity of Cu2ONPs against Fusarium solani under laboratory, greenhouse, and field conditions were also evaluated. In addition, the induction of host-plant resistance by Cu2ONPs was confirmed by the results of enzyme activities (catalase, peroxidase, and polyphenoloxidase) and gene expression (PR-1 and LOX-1). Finally, the effect of Cu2ONPs on the growth and productivity characteristics of the treated cucumber plants was investigated. The average particle size from all the peaks was found to be around 25.54 and 25.83 nm for 0.30 and 0.35 Cu2O, respectively. Under laboratory conditions, the study found that Cu2ONPs had a greater inhibitory effect on the growth of Fusarium solani than the untreated control. Cu2ONP treatment considerably reduced the disease incidence of the root rot pathogen in cucumber plants in both greenhouse and field environments. Defense enzyme activity and defense genes (PR1 and LOX1) transcription levels were higher in cucumber plants treated with Cu2ONPs and fungicide than in the untreated control. SEM analysis revealed irregularities, changes, twisting, and plasmolysis in the mycelia, as well as spore shrinking and collapsing in F. solani treated with Cu2ONPs, compared to the untreated control. The anatomical analysis revealed that cucumber plants treated with Cu2ONPs had thicker cell walls, root cortex, and mesophyll tissue (MT) than untreated plants. Cucumber growth and yield characteristics were greatly improved after treatment with Cu2ONPs and fungicide. To the best of our knowledge, employing Cu2ONPs to treat cucumber rot root disease is a novel strategy that has not yet been reported.

Leaf Extracts from Resistant Wild Tomato Can Be Used to Control Late Blight (Phytophthora infestans) in the Cultivated Tomato.

Late blight disease, caused by Phytophthora infestans (Mont.) de Bary, is one of the most challenging diseases threatening tomato production and other Solanaceae crops. Resistance to late blight is found in certain wild species, but the mechanism behind the resistance is not fully understood. The aim of this study was to examine the metabolic profiles in the leaf tissue of late blight-resistant wild tomato and to investigate if leaf extracts from such genotypes could be used to control late blight in tomato production. We included three recognized late blight-resistant wild tomato accessions of Solanum habrochaites (LA1777, LA2855, and LA1352) and two recognized highly susceptible genotypes, S. lycopersicum ('Super Strain B') and S. pimpinellifolium (LA0375). The metabolic profiles were obtained in both inoculated and non-inoculated plants by analyzing leaf extracts using high-resolution gas chromatography-mass spectrometry (GC-MS) with three replicate analyses of each genotype. We focused on volatile organic compounds (VOCs) and identified 31 such compounds from the five genotypes with a retention time ranging from 6.6 to 22.8 min. The resistant genotype LA 1777 produced the highest number of VOCs (22 and 21 in the inoculated and control plants, respectively), whereas the susceptible genotype 'Super Strain B' produced the lowest number of VOCs (11 and 13 in the respective plants). Among the VOCs, 14 were detected only in the resistant genotypes, while two were detected only in the susceptible ones. In vitro trials, with the use of a detached leaflet assay and whole-plant approach, were conducted. We revealed promising insights regarding late blight management and showed that metabolic profiling may contribute to a better understanding of the mechanisms behind P. infestans resistance in tomato and its wild relatives.

Analysis of the lineage of Phytophthora infestans isolates using mating type assay, traditional markers, and next generation sequencing technologies.

Phytophthora infestans (Mont.) de Bary, a hemibiotrophic oomycete, has caused severe epidemics of late blight in tomato and potato crops around the world since the Irish Potato Famine in the 1840s. Breeding of late blight resistant cultivars is one of the most effective strategies to overcome this disruptive disease. However, P. infestans is able to break down host resistance and acquire resistance to various fungicides, possibly because of the existence of high genetic variability among P. infestans isolates via sexual and asexual reproduction. Therefore, to manage this disease, it is important to understand the genetic divergence of P. infestans isolates. In this study, we analyzed the genomes of P. infestans isolates collected from Egypt and Japan using various molecular approaches including the mating type assay and genotyping simple sequence repeats, mitochondria DNA, and effector genes. We also analyzed genome-wide single nucleotide polymorphisms using double-digest restriction-site associated DNA sequencing and whole genome resequencing (WGRS). The isolates were classified adequately using high-resolution genome-wide approaches. Moreover, these analyses revealed new clusters of P. infestans isolates in the Egyptian population. Monitoring the genetic divergence of P. infestans isolates as well as breeding of resistant cultivars would facilitate the elimination of the late blight disease.

Rapid identification of candidate genes for resistance to tomato late blight disease using next-generation sequencing technologies.

Tomato late blight caused by Phytophthora infestans (Mont.) de Bary, also known as the Irish famine pathogen, is one of the most destructive plant diseases. Wild relatives of tomato possess useful resistance genes against this disease, and could therefore be used in breeding to improve cultivated varieties. In the genome of a wild relative of tomato, Solanum habrochaites accession LA1777, we identified a new quantitative trait locus for resistance against blight caused by an aggressive Egyptian isolate of P. infestans. Using double-digest restriction site-associated DNA sequencing (ddRAD-Seq) technology, we determined 6,514 genome-wide SNP genotypes of an F2 population derived from an interspecific cross. Subsequent association analysis of genotypes and phenotypes of the mapping population revealed that a 6.8 Mb genome region on chromosome 6 was a candidate locus for disease resistance. Whole-genome resequencing analysis revealed that 298 genes in this region potentially had functional differences between the parental lines. Among of them, two genes with missense mutations, Solyc06g071810.1 and Solyc06g083640.3, were considered to be potential candidates for disease resistance. SNP and SSR markers linking to this region can be used in marker-assisted selection in future breeding programs for late blight disease, including introgression of new genetic loci from wild species. In addition, the approach developed in this study provides a model for identification of other genes for attractive agronomical traits.