Five isolates of Trichoderma spp. were investigated, in a preliminary study, for their efficiency in controlling Rhizoctonia root rot of pepper (Capsicum annuum L.). GC-MS analysis of most active Trichoderma spp. extracted secondary metabolites were studied. The major compounds identified by GC-MS analysis included hexadecanol, nonadecene, 1,2-benzenedicarboxylic acid, octadecenoic acid (z) and hexadecanol, 2-methyl. These compounds have been found to play an important role in controlling plant diseases. The results of antagonistic activity of three isolates proved higher efficiency in controlling R. solani. Browning of the R. solani mycelium was observed where mycoparasitism occurred. The parasitism of R. solani hyphal cells by Trichoderma harzianum was studied by light and scanning electron microscopy. Sequence data of R. solani isolates (R.1, R.2 and R.4) have been submitted to the GenBank under accession numbers (MZ267232, MZ267234 and MZ267689), respectively. The most effective isolates i.e., T. asperellum, T. hamatum and T. harzianum in addition to their mixture were formulated in different forms i.e., suspension and powder, then tested at different concentrations under the greenhouse and protected cultivation conditions. Results of greenhouse studies indicated that all isolates and their mixture were effective in controlling pepper root rot disease and increasing percentage of survived plants. Moreover, results showed that suspension was effective than powder in reducing the disease. Higher bio-control efficiency at protected cultivation was obtained when the mixture of isolates was used at high concentration. Most of the Trichoderma spp. studied in the present work have been able to reduce severity of R. solani.

Squash (Cucurbita pepo L.) is a globally important vegetable, the production of which is severely constrained by powdery mildew caused by Podosphaera xanthii. In this study, we examined the effects of Trichoderma asperellum (MW965676), Streptomyces rochei (MN700192), and a mixture of the two foliar sprays with or without shikimic acid seed priming treatment on powdery mildew severity, plant growth, and total yield during the 2020–2021 and 2021–2022 growing seasons. We also studied their immune eliciting properties by examining their enzymatic, phenolic, and hormonal functions. The combination of Trichoderma asperellum, Streptomyces rochei, and shikimic acid triggered plant defense responses, which elicited enzyme activities such as peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), phenolic compound accumulation, and increased salicylic acid (SA) and jasmonic acid (JA) content. This approach yielded high-quality results in the control of powdery mildew during the two growing seasons under greenhouse conditions. Additionally, relatively large statistical differences in plant growth, total yield, mineral components, and physiological traits were observed. A GC–MS analysis of Trichoderma asperellum (MW965676) showed hemin cation as a major component, while Streptomyces rochei (MN700192) contained 2,4-di-tert-butyl phenol and the hexadecenoic acid methyl ester. With respect to the morphological changes induced by powdery mildew and the treatments, plants treated with a mixture of Trichoderma asperellum, Streptomyces rochei and shikimic acid showed an improvement in the thickness of the midvein, increased dimensions of the main midvein bundle, a larger number of xylem rows in the main midvein bundle, greater mean diameters of vessels and of parenchyma cells in the ground tissues, as well as increased thickness of the upper and lower epidermis, lamina, palisade tissue and spongy tissue. This extensive, new study is the first step toward a more profound understanding of the use of Trichoderma asperellum and Streptomyces rochei with shikimic acid-primed seeds as a potential alternative technique for attenuating powdery mildew infection in squash.

The efficiency of foliar spray with potassium sulphate, potassium silicate, calcium chloride and calcium citrate gel formula was evaluated in controlling early blight disease (caused by Alternaria solani), improving growth and yield quality of potato (cv. Lady Rosetta). A field experiment was performed during two successive seasons, 2018/2019 and 2019/2020. Foliar applications of potassium and calcium compounds were compared to Copperal Max (8 % copper as a positive control) and water as a control treatment. All treatments were sprayed twice on the plants at 45 and 60 days post-planting. The results proved that all foliar spraying treatments significantly decreased the disease incidence and severity of early blight, improved vegetative growth parameters and nutrients content (N, P and K) of potato plants as well as increased yield and tuber quality of potato compared with untreated plants. In this respect, the lowest disease severity was achieved by Copperal Max (9 and 11.05%) followed by potassium silicate (9.95 and 12.77%) and calcium chloride (9.66 and 12.92%), finally, untreated control recorded the highest disease severity (22.07 and 26.71 %) respectively at both tested seasons. On the other hand, potassium silicate and calcium chloride in gel formula was superior to other treatments in increasing the total and marketable yield of potato tubers, also reducing the weight loss and decay of tubers stored on a shelf. These results suggest that one of the main alternatives to controlling potato early blight is using potassium silicate or calcium chloride.

Cucumber is one of the most popular and favorite vegetable crops cultivated under greenhouse in Egypt. A greenhouse experiment was carried out to reduce cucumber transplants root rot. Soaking cucumber seeds before sowing in different concentrations of micronutrients, antioxidants, and their combinations were evaluated for controlling Rhizoctonia solani root rot. The results indicated that the highest seedling stand 73.4% after 12 days was recorded after soaking cucumber seeds in sodium selenium solution at 1 ppm. In artificially infested pots with R. solani seed treated with potassium tartrate and boric acid had the highest seedling stands with a clear increase in total phenol contents. Potassium tartrate combined with boric acid showed the highest reduction in radial growth of R. solani by 88.9%. The highest reduction of oxalic acid produced by R. solani on PDA medium supplemented with boric acid were measured using high performance liquid chromatography. Our findings demonstrated an effective approach for inducing resistance in cucumber transplants to Rhizoctonia root rot utilizing micronutrients and free radical scavengers.