Background Soft rot disease caused by Pectobacterium carotovorum was observed in various crops which lead to yield shortages and economic losses. Main body Therefore, both in vitro and in vivo experiments, aim to assess the effect of nanoparticles and biological treatments to control soft rot disease in sugar beet plant. The treatments comprised three silver nanoparticles (Ag NPs) concentrations (50, 75, and 100 ppm), three Spirulina platensis extract concentrations (50, 75, and 100%), and Bacillus subtilis (1 × 109 CFU ml) 100%. Under in vitro condation, results of the antibacterial activity showed that the zones of inhibition recorded 4.33 cm for 100 ppm Ag NPs, 0.43 cm for 100% algal extract, and 0.2 cm for bacterial treatments. Also, disease incidence % of bacterial soft rot was significantly decreased in all treatments in pot and field experiments. For resistant enzymes activity, B. subtilis 100% showed the most effect (84 mg min−1), followed by S. platensis extract 75%, (57 mg min−1), and Ag NPs 75 ppm (44 mg min−1), for poly phenol oxidase (PPO) at 81 days after sowing (DAS), but at 102 DAS revealed opposite results. On the contrary, peroxidase (PO) at 81 DAS showed different effects where treatment with S. platensis extract 100% increased it significantly (0.546 mg min−1) compared to control (0.535 mg min−1). The same trend was observed at 102 DAS. These results were reflected on sugar quality where Ag NPs 100 ppm treatment recorded the highest significant value (20.5%) followed by S. platensis 75% (19 %); however, the differences among them were not statistically significant. Conclusion This study indicated that the potential benefits of using silver nanoparticles and two biological treatments to control soft rot disease in sugar beet (Beta vulgaris L).

ntimicrobial potential of Controller, Impose, Phostrol, Ridomil Gold plus, and Roxyl Plus was determined for Pectobacterium atrosepticum and Streptomyces scabies. The cidal effect against P. atrosepticum was only shown by the fungicide Controller. S. scabies was highly affected by Controller, Impose and Roxyl Plus compared to RidomilGold plus, and Phostrol that did not inhibit the growth. The MIC of Controller was found to be 4000 ppm for P. atrosepticum and S. scabies. On the other hand, the MICs of Impose and Roxyl Plus were found to be 4000 ppm and 3000 ppm respectively for S. scabies. Application of Controller against blackleg significantly decreased the incidence of the disease in potted potato plants. Application of Controller, Impose and Roxyl Plus at 3.0g/l to control common scab significantly decreased the disease. Conclusive results were obtained by the 4.0 g/l application. Residues of ingredients of these fungicides in potato tuber 60 day after application were below the approved maximum residue level (MRL).

he potato common scab disease became a major threat for potato raised in light soil(s) in Egypt. In the present work, eight out of twenty-five isolates of Streptomyces recovered from four locations and rhizosphere soil of three different crops showed antagonistic potential against Streptomyces scabies. The partial 16S rRNA gene sequences of five of these eight isolates showed 99.13 to 99.67 % similarity with Streptomyces rochei strain NRRL B-1559.The other three isolates showed 99.73, 99.60, and100 % similarity with Streptomyces geysiriensis strain NRRL_B-12102, Streptomyces tunisiensis strain CN-207, and Streptomyces djakartensis strain NBRC 15409, respectively. The partial 16S rRNA gene sequences of the eight antagonistic isolates have been deposited in the GenBank of the National Center for Biotechnology Information (NCBI) under the accession numbers MT878417, MT878546, MT878545, MT878152, MT878547, MT878450, MT878478, and MT878497. The inhibition zones of the growth of Streptomyces scabies by the eight selected antagonistic isolates of Streptomyces were variably from 32.7 to 66.7 mm. Application of Streptomyces geysiriensis 7AS_GP8, Streptomyces tunisiensis 8AS_BNM2, Streptomyces djakartensis 4AS_MO2, and Streptomyces rochei 5AS_MO3 in pots experiment significantly decreased scab index from 68.6 % in control treatment to 39.1, 47.7, 25.3, and 31.7 %, respectively. Streptomyces djakartensis 4AS_MO2 gave the pronounced decrease (63.1%) in disease followed by Streptomyces rochei 5AS_MO3 (53.8 %), Streptomyces geysiriensis 7AS_GP8 (42.9 %), and Streptomyces tunisiensis 8AS_BNM2 (30.4%), respectively. Streptomyces djakartensis 4AS_MO2 and Streptomyces rochei 5AS_MO3 provided promising results as potential biocontrol agents against Streptomyces scabies. Further field studies may be advised.

The study was carried out in a greenhouse at Plant Pathology Research Institute, "Agricultural Research Center, Giza, Egypt" to evaluate bio-char applications of potato scab controlling caused by Streptomyces scabies in sandy and clayey textured soil. Water dressing of potting soils was discussed with the influence of bio-char application to both kinds of infested and non-infested soils. The results showed that the application of bio-char for potato seed bed and the regular irrigation (every 3 days) caused an increase in organic carbon in both sterilized soils. While, the bio-char application in state under seedbed for infested sandy soil caused low nitrogen content at both watering treatments. In this preliminary study similar results were shown in clayey infested soil. Which soil porosity that is being inversely related to disease and it is positively correlated to soil bulk density (bd). Also, the results showed that bio-char application decreased the interspaces between particles consequentially minimizing soil bulk density for watering treatments in concern. The soil reaction (pH) was increased with the application of bio-char to infested soil under both watering system. Biochar amended sandy and clayey soils expressed decreased incidence of scabby tubers especially at higher dose regular watering. This preliminary study reveals that the necessity of bio-char field treatments, to explain in depth the physiological, histological and changes in soil edaphic factors as related to Streptomyces scabies infections.