Water salinity is one of the major abiotic stresses, and the use of saline water for the agricultural sector will incur greater demand in the coming decades. Recently, nanoparticles (NPs) have been used for developing numerous plant fertilizers as a smart and powerful form of material with dual action that can alleviate the adverse effects of salinity and provide the plant with more efficient nutrient forms. This study evaluated the influence of calcium phosphate NPs (CaP-NPs) as a soil fertilizer application on the production and bioactive compounds of broad bean plants under salinity stress. Results showed that salinity had deleterious effects on plant yield with 55.9% reduction compared to control. On the other hand, CaP-NPs dramatically improved plant yield by 30% compared to conventional fertilizer under salinity stress. This improvement could be attributed to significantly higher enhancement in total soluble sugars, antioxidant enzymes, proline content, and total phenolics recorded use of nano-fertilizer compared to conventional use under salt stress. Additionally, nano-fertilizer reflected better mitigatory effects on plant growth parameters, photosynthetic pigments, and oxidative stress indicators (MDA and H2O2). Therefore, our results support the replacement of traditional fertilizers comprising Ca2+ or P with CaP-nano-fertilizers for higher plant productivity and sustainability under salt stress.

The tomato pathotype of Alternaria alternata (A. arborescens) produces the dark brown to black pigment melanin, which accumulates in the cell walls of hyphae and conidia. Melanin has been implicated as a pathogenicity factor in some phytopathogenic fungi. Here, two genes of the tomato pathotype for melanin biosynthesis, ALM1 and BRM2-1, which encode a polyketide synthetase and a 1,3,8-trihydroxynaphthalene (THN) reductase, respectively, have been cloned and disrupted in the pathogen. The gene-disrupted mutants, alm1 and brm2-1, had albino and brown phenotypes, respectively. The wild-type and the mutants caused the same necrotic lesions on the leaves after inoculation with spores. These results suggest that melanin is unlikely to play a direct role in pathogenicity in the tomato pathotype A. alternata. Scanning electron microscopy revealed that the conidia of both mutants have much smoother surfaces in comparison to the wild-type. The conidia of those mutants were more sensitive to UV light than those of the wild-type, demonstrating that melanin confers UV tolerance.

No abstract

Phytoplasmas are obligate cell-wall-less plant pathogenic bacteria that infect many economically important crops, causing considerable yield losses worldwide. Very little information is known about phytoplasma–host plant interaction mechanisms and their influence on sesame yield and oil quality. Therefore, our aim was to explore the ultrastructural and agro-physio-biochemical responses of sesame plants and their effects on sesame productivity and oil quality in response to phytoplasma infection. Sesame leaf samples exhibiting phyllody symptoms were collected from three experimental fields during the 2021 growing season. Phytoplasma was successfully detected by nested- polymerase chain reaction (PCR) assays using the universal primer pairs P1/P7 and R16F2n/R16R2, and the product of approximately 1200 bp was amplified. The amplified product of 16S rRNA was sequenced and compared with other available phytoplasma’s 16S rRNA in the GenBank database. Phylogenetic analysis revealed that our Egyptian isolate under accession number MW945416 is closely related to the 16SrII group and showed close (99.7%) identity with MH011394 and L33765.1, which were isolated from Egypt and the USA, respectively. The microscopic examination of phytoplasma-infected plants revealed an observable deterioration in tissue and cell ultrastructure. The primary and secondary metabolites considerably increased in infected plants compared with healthy ones. Moreover, phytoplasma-infected plants showed drastically reduced water content, chlorophyll content, growth, and yield components, resulting in 37.9% and 42.5% reductions in seed and oil yield, respectively. The peroxide value of the infected plant’s oil was 43.2% higher than that of healthy ones, suggesting a short shelf-life. Our findings will provide a better understanding of the phyllody disease pathosystem, helping us to develop effective strategies for overcoming such diseases.

The tomato pathotype of Alternaria alternata causes Alternaria stem canker of tomato (Solanum lycopersicum L.) by producing a host-specific AAL-toxin. The chemical structure and biological activities of AAL-toxin are analogous to those of the mycotoxin fumonisin. Determination of pathogen development and toxin production in infected tomato plants is of prime importance for pathological evaluation and risk assessment of AAL-toxin. On a resistant cultivar, AAL-toxin and the pathogen were restricted to a small region surrounding only the initial inoculation site. On the other hand, widespread distribution of the toxin and the pathogen were detected in a susceptible cultivar. The pathological signifi cance and contamination risk from the toxin were supported by the results of in planta production of the toxin in diseased tomato plants.

he effects of essential oils of clove and fennel seeds and their major components as foliar spray were screened for inducing resistance against Potato Virus Y in vivo in both systemic and local lesion hosts at different concentrations. Clove oil at conc. of 15% gave the highest inhibitory effect against PVY infection than fennel oil. The inhibition percentages were 85, 80 % in pepper as a systemic host and up to 90, 87 %, respectively in Chenopodium amaranticolor as a local lesion host when applied 48 hrs before virus inoculation. Whereas, the inhibitory effect was less pronounced when essential oils were sprayed on the tested plants 24 hrs before virus inoculation. However, the severity of symptoms was assessed by visual inspection. ELISA test was used to confirm the results in all cases. When the major components of essential oils were applied individually, Eugenol gave the highest inhibitory effect (90%) on PVY-systemically infected pepper plants and 91.8% on Ch. amaranticolor as local infected plants when applied 48 hrs before virus inoculation followed by Anethol. While, Limonene was less effective in reduce PVY infection. Considerable increase in total protein content in pepper plants sprayed with essential oils and their major components before virus inoculation was recorded compared with healthy and infected control plants. Moreover, SDS-PAGE revealed a new protein band 20 KDa which was found only in pepper plants sprayed with clove oil at conc. of 15%. Also new proteins 19, 20 KDa and 25 KDa were found only in pepper plants sprayed with Eugenol. It has been suggested that, the induced proteins may help to limit virus spread or multiplication.

No abstract

Zucchini yellow mosaic virus (ZYMV) is one of the most important viruses and is responsible for significant losses in cucurbit crops worldwide. In Egypt, it causes serious economic losses in squash especially in spring season. During 2014-2015, samples were collected from squash fields in different Provinces, Fayoum Governorate. In Fayoum, ZYMV-naturally infected squash plants exhibited severe mosaic and blisters, leaves deformation, blisters on the fruits and discoloration hardening of flesh, as well as external fruit cracks. Percentages of infection in squash cv. Eskandrani, ranged between 20-35% and 70-78% in mid-March and May, respectively. Meanwhile, it ranged between 15-25% in September and 62% in the end of November. The virus was isolated from naturally-infected squash plants serologically depending on enzyme-linked immunosorbant assay (ELISA), and biologically by mechanical inoculation to different species belonging four families i.e., Amarnthaceae, Chenopodiaceae, Cucurbitaceae, Solanacea. In virus vector relationship, transmission rates recorded 84.6, 86.6, 93.3, 90, and 91.6%, respectively for squash cvs. Alia, Asma, Eskandrani, Mabrouka and Safa. In this context, one insect vector (Myzus persicae) proved its ability to transmit ZYMV. Electron microscopy (EM) of partially purified preparation method revealed flexuous particles approximately 750X15 nm. Serologically, TBIA proved to be effective in detecting ZYMV in the infected samples and reliable technique for the virus detection in squash leaf midrib and petioles. Electrophoresis analysis of the reverse transcription polymerase chain reaction (RT-PCR) amplification revealed that the primers amplified a product size of 458bp for the RNA extracted from ZYMVinfected tissues.