Nanodiagonastic methods in plant pathology are used for enhancing detection and identification of different plant pathogens and toxigenic fungi. Improvement of the specificity and efficiency of the polymerase chain reaction (PCR) by using some nanoparticles is emerging as a new area of research. In the current research, silver, zinc, and gold nanoparticles were used to increase the yield of DNA for two plant pathogenic fungi including soil-borne fungus Rhizoctonia solani and toxigenic fungus Alternaria alternata. Gold nanoparticles combined with zinc and silver nanoparticles enhanced both DNA yield and PCR products compared to DNA extraction methods with ALB buffer, sodium dodecyl sulfate, ALBfree from protinase K, ZnNPs and AgNPs. Also, by using ZnNPs and AgNPs the DNA yield was enhanced and the sensitivity of random amplified polymorphic DNA (RAPD) PCR products was increased. Application of nanomaterials in the PCR reaction could increase or decrease the PCR product according to the type of applied nanometal and the type of DNA template. Additions of AuNPs to PCR mix increased both sensitivity and specificity for PCR products of the tested fungi. Thus, the use of these highly stable, commercially available and inexpensive inorganic nano reagents open new opportunities for improving the specificity and sensitivity of PCR amplicon, which is the most important standard method in molecular plant pathology and mycotoxicology.

Black mold and green mold caused by Alternaria alternata and Penicillium digitatum, respectively, are the most important decay pathogens of tomato fruits during storage. Our research was aimed to control tomato phytopathogenic fungi A. alternata and P. digitatum in vitro and in vivo by using natural nanomaterials rosmarinic acid (RA-NPs) at concentrations of 0.3 and 0.6 mM, glycyrrhizic acid (GA-NPs) and glycyrrhizic acid ammounium salt (GAS-NPs) (0.1–0.2 mM). Characterizations of the tested nanoparticles were carried out by using dynamic light scattering which revealed that synthesized nanoparticles had particle sizes of less than 100 nm. In vitro studies revealed that the three tested nanoparticles reduced the growth of A. alternata and P. digitatum. Glycyrrhizic acid nanoparticles were the most effective in reducing the growth of the two tested pathogens followed by RA-NPs at 0.6 mM. Observations of A. alternata and P. digitatum by scanning electron microscopy (SEM) showed severe damage in the hyphae and deformities in the conidia due to the effect of the tested nanoparticles. In vivo results showed that, dipping tomato fruits as a post-harvest treatment in all of the tested nanoparticles at different concentrations, then stored at 10 ± 1°C and 90–95% relative humidity (RH) for 20 days greatly reduced the disease severity of infected fruits with the two tested pathogens. GA-NPs at 0.2 mM significantly reduced the development of black mold rot on tomato fruits. RA-NPs at 0.6 mM had the best effect in controlling P. digitatum of all naturally and artificially inoculated tomato fruits. Also, individual treatments of tomato fruits with RA-NPs, GA-NPs and GAS-NPs significantly reduced postharvest losses of fruit since they delayed decay and maintained fruit quality characteristics such as fruit firmness, titratable acidity and total soluble solids during cold storage.

Mycoherbicides are special biotechnology products which contain fungi or fungal metabolites as nonchemical alternatives thereby reducing the input of harmful chemicals to control noxious weeds. The present communication emphasizes on the potential of an indigenous isolate of Alternaria alternata ITCC 4896 as a mycoherbicide for the global weed – Parthenium hysterophorus. Of the various spore concentrations tested by in vitro Detached Leaf Bioassay, 1x10⁶ spores/ml was the most effective inducing 89.2% leaf area damage on the 7th day and was further tested by Whole Plant Bioassay. Both in vitro Detached Leaf Bioassay and Whole Plant Bioassay exhibited a similar trend in disease development showing 50% damage at 96 hours post treatment. However, 100% mortality was observed in the Whole Plant Bioassay on the 7th day. This is the very first report on the bioweedicidal potential of A. alternata ITCC 4896 (LC#508) for use as a mycoherbicide for P. hysterophorus.

Genetically modified Bt cotton (Gossypium hirsutum) leaves with typical symptoms of Alternaria early blight disease resembling that of tomato and potato were observed in the main cotton growing schemes in Sudan. Symptoms on leaves appeared as either brown 2leaf spot with gray centers or leaf blight with concentric rings. Pathogenicity tests using isolates with both symptoms showed that the isolated fungi were highly pathogenic to both G. hirsutum and G. barbadense cotton varieties. Alternaria alternata isolated from infected tomato and potato leaves with early blight symptoms was included for comparison. Microscopic examination showed that the mean length of conidia from cotton, tomato and potato isolates ranged from 26.25 to 45.45 μm, while the width ranged from 9.56 to 13.64 μm. The mean number of transverse septa among all isolates was 3.4 to 5.7 and the peak length ranged from 3.75 to 7.8 μm. Based on morphological characteristics the two isolates from cotton were identified as A. alternata. Genomic DNA was extracted directly from fungal cultures grown on potato dextrose agar (PDA) plates using a Zymo Research Quick DNA kit. A species-specific primer using the internal transcribed spacer ribosomal DNA (ITS rDNA) PCR scoring indicated the presence of A. alternata using primer pair ITS4/ITS5. Amplifications of the internal transcribed spacer region of 600 bp revealed 100% identity of the isolated fungus from cotton with A. alternata from tomato and potato. These data oblige us to reconsider the presence of A. alternata in the four main cotton growing schemes in Sudan while these symptoms have always been described for tomato and potato early blight disease.