Background White mold disease, caused by Sclerotinia sclerotiorum the devastating pathogen, attacks green beans (Phaseolus vulgaris L.) and several crops worldwide. The present investigation was carried out to introduce some antagonistic microorganisms as novel antifungal substances to be an alternative and secure method to effectively control the disease. Results Three Streptomyces species, i.e., S. griseus (MT210913 “DG5”), S. rochei (MN700192 “DG4”), and S. sampsonii (MN700191 “DG1”) were isolated, biologically, molecularly characterized, and evaluated in vitro and in vivo. Molecularly, polymerase chain reaction (PCR) amplification and nucleotide sequencing were used to characterize the pathogen and bio-agents. PCR amplification of the pathogen and Streptomyces species (bioagents) exhibited amplicons of around 535 bp and 1300 bp, respectively. The nucleotide sequence analysis of the three Streptomyces spp. indicated that S. rochei was closely related to S. griseus, and both had a distance relationship with S. sampsonii. The evaluation of bioagents was carried out against S. sclerotiorum. Reduction percentages in the mycelial growth of the pathogen ranged between 60.17 and 52.30%, indicating that S. rochie gave the highest inhibition percent. Incorporations of Streptomyces spp. culture filtrate components into culture media proved that S. sampsonii was more efficient as a bioagent in reducing mycelial growth pathogen by 84.50%. The effectiveness of the bioagent volatile compounds inhibited the pathogen growth at a rate of 54.50-72.54%, respectively, revealing that S. rochei was the highest inhibitor followed by S. griseus. The parasitic activity of Streptomyces spp. upon S. sclerotiorum showed deformation, contraction, and collapse when observed by light and scanning electron microscopy. Molecular characterization of the 3 Streptomyces spp. revealed that S. griseus was closely related to S. sampsonii (96%), secondly ranked by S. rochei (93.1%). Viability and germination of pathogen sclerotia were reduced when they dipped into the Streptomyces spore suspensions for 10, 20, and 30 days. Application of the 3 Streptomyces spp. in the field proved a great potential to control the disease. Conclusions The results suggested that the 3 Streptomyces strains and their secondary metabolites can be potential biocontrol agents and biofertilizers for controlling S. sclerotiorum, the causative agent of bean white mold disease.

A filed experiment was carried out during the two successive seasons of 2016/2017 and 2017/2018 at the Experimental Farm of El-Kassasein, Hort. Res. Station, Ismailia Governorate, Egypt, to investigate the effect of foliar spray with amino acids, citric acid, some calcium compounds and mono-potassium phosphate (MKP) on vegetative growth, early and total yield, yield components, storability and gray mould disease reduction of strawberry Festival cultivar under sandy soil conditions. The obtained results showed that, spraying strawberry plants with CaCl 2 at 20 ml/l, amino acids at 10 ml/l, citric acid at 2 g/l, calcium amino acids chelate at 20 ml/l and calcium citric acid chelates at 20 ml/l and mono-potassium phosphate (MKP) at 20 ml/l increased yield, yield components and decreased incidence and severity of gray mould disease compared to control. Spraying with amino acids or calcium amino acids chelate increased plant height, number of leaves/ plant, shoot dry weight/ plant, average yield/plant, total yield/fad., and decreased weight loss (%) and decay (%) during cold storage periods. Spraying with MKP recorded minimum incidence (12.6 and 18.3 %) and severity (13.9 and 13.2%) of gray mould disease in fruits at the 1 st and 2 nd seasons, respectively, followed by spraying with calcium amino acids chelate. In addition, incidence and severity of gray mould disease decreased with increasing TSS and vitamin C in strawberry fruits.

Background Soil-borne plant pathogenic fungi with a wide host range of crops cause a significant limitation on the global production of agronomic crops. Applications of synthetic pesticides are an important tool for managing plant diseases, but have deleterious influences on the environment as well as its incompatibility with organic agriculture. Recently, Streptomyces spp. became one of the best bio-control agents as a promising environmentally eco-friendly method for effective management of plant diseases. Results In a previous research, three species of Streptomyces spp., i.e., S. griseus (MT210913 “DG5”), S. rochei (MN700192 “DG4”) and S. sampsonii (MN700191 “DG1” strains) were identified, as exhibiting potent antifungal activities against plant pathogenic fungus, Sclerotinia sclerotiorum in vitro and greenhouse. GC–Mass analysis revealed the presence of 44, 47 and 54 substances of S. sampsonii DG1, S. griseus DG5 and S. rochei DG4, respectively. GC–MS revealed substances, with bio-control activity, were categorized as volatile organic compounds (VOCs), fatty acids and plant growth regulators, etc. GC–MS analysis exhibited the presence of 7, 13 and 20 volatile compounds produced by S. sampsonii, S. rochei and S. griseus, respectively. These substances exhibited potent antifungal activity against various plant pathogenic fungi, i.e., Botrytis cinerea, Macrophomina phaseolina, Rhizoctonia solani and S. sclerotiorum in vitro, by dual-culture assay. The three strains inhibited all the pathogenic fungi in dual-culture assay in the range of 30–73.67%. Also, the produced substances were applied in vivo (in the field) and supported their potential biocontrol agent against S. sclerotiorum as well as possessed significant biological properties for plant health and growth. Applying Streptomyces spp. culture broth in the field enhanced physiological responses of phenols, sugar, chlorophyll, protein contents and parameters as well as the yield of bean plants. Conclusion In field experiments, foliar application of Streptomyces spp. and their metabolites proved to be a great potential, as promising biocontrol agents, for controlling S. sclerotiorum and enhanced plant growth and yield. S. rochei and S. griseus proved to be strong antifungal, plant growth promoters and environmentally eco-friendly fungicides.

he 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.

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.