The influence of bio-char on Common scab disease of potatoes

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. Keywords; Potato, potato common scab, bio-char INTRODUCTION Potato (Solanum tuberosum L.) crop is subject to numerous diseases of different microbial origins especially bacterial pathogens (Kirk, 2015). Potato common scab is one of the main concerns for farmers worldwide, since it decreases the marketing quality of tubers via in skin blemishes that render them unacceptable for seed potato production, fresh consumption and processing (Loria et al., 1997; Wanner and Kirk, 2015). The disease also can cause considerable economic loss to other root crops including radish, beet, sweet potato, turnip and carrot (Wanner 2004). Common scab of potato is caused by Gram-positive filamentous actinomycetes belonging to the genus Streptomyces (Thaxter, 1891), and the major common scab inducing organism was nominated Streptomyces scabies. Furthermore, Streptomyces scabies isolates causing symptoms with aggressiveness of strains varying from mild to moderately or severe ones (DSMZ, 2015). The disease induces a variety of symptoms such as raised lesions, deep pitted, or sunken lesions and superficially netted skin on tuber surface (Kers et al., 2005). The disease worldwide has been reported in many countries as China (Zhang, et al.2013), South Africa (Slabbert, 1994), Pakistan (Ahmad et al., 1995), Iran ( Zadeh et al., 2006), Russia (Lysenko et al., 2005), United States (Pasiecznik et al., 2005). Bio-char is resulting from the thermal-chemical change for the organic biomass that contains of carbon richness by pyrolysis process wherefore considered the black gold for agriculture (Masiello et al., 2015). The bio-char applications are used in augmenting both plant-available water, agriculture to improve soil properties, enhancing crop yield and avoiding short and long-term detrimental effects to the environment (Lehmann, 2007; Sohi et al., 2010; Cheng et al., 2008 Verheijen et al., 2010: Verheijen et al., 2019). One of the most important applications of bio-char is can be used as different quantities in soil amendment on the top, or mixed into deeper soil layers. It was noted that, mixing bio-char into deeper soil layers alters soil physical properties as a function of bio-char characteristics (particle size, shape and material) (Lim and Spokas, 2018 and Fischer et al., 2019). On the contrary added bio-char on the Surface has only a minor effect on the soil physical properties (Blanco-Canqui, 2017). Soil organic amendments and are an increasingly popular practice used to enhance soil health quality in managed agroecosystems (Gómez-Sagasti et.al., 2018). Green manures, crop residues and composts have been used broadly as means to increase soil organic matter content and carbon availability, and consequently, stimulate microbial biomass and activity in the soil (Larkin, 2015; Francioli et al., 2016). Addition of organic amendments to soil has been associated with natural suppression of soilborne plant pathogens (Larkin, 2015; Liu et al., 2015; Jaiswal et al., 2017). The Possible mechanisms of suppression include the increase in microbial antagonism, as well as plant growth promotion, activation of systemic induced resistance, and accumulation of plantderived biocidal compounds (Zhang et al., 1998; Wiggins and Kinkel, 2005; Bressan et al., 2009). 170 years ago (Allen 1847) attracted attention in the last decade appositive influence of bio-char on limiting plant diseases as rust and mildews in other crops. in addition, several pathosystems were studied by different groups worldwide. Omnia A. Abd El-Hafez and Mariam A. Amer 374 (Elad et al., 2010; Elmer, Pignatello 2011; Jaiswal et al., 2014; Copley et al., 2015; Jaiswal et al., 2015). Whereas, Pathosystems included both foliar pathogens and soil borne pathogens (Elad et al., 2011; Graber et al., 2014). Newly, Bonanomi et al., (2015) focused on the tested the effect of bio-char on the 13 pathosystems on plant disease. They reported that a positive influence of bio-char in reducing plant disease severity were very high compared to no effect on plant disease severity. while, they reported only 3% from biochar additions were conducive to plant disease. Moreover, several studies on bio-char in detached growing media reported that while relatively low concentrations (≤1%) of biochar suppressed the diseases (Jaiswal et al. 2014, 2015; Huang et al. 2015), higher concentrations (3%) were mostly ineffective or even accelerated plant disease (Jaiswal et al., 2014, 2015; Copley et al., 2015; Huang et al., 2015 and Frenkel et al., 2017. Overall, the application of bio-char to the clayey nutrient rich paddy soil may be sustain an increase in soil organic carbon (SOC), soil aggregation and soil health functioning with positive changes in microbial community over years. Thus, carbon increase as required could be a mechanistic driver to enhance soil fertility and improve soil(plant) health for ensuring food production in rice agriculture facing land degradation and climate change impacts, which could be assisted by bio-char from crop residue in an approach of circular economy (Lua et al., 2020). In addition, bio-char application in soils caused a significant increase microbial activity, functional diversity and microbial taxonomicas well as an overall shift in carbonsource utilization. All of these bio-char amendments in soils in the rhizosphere related with suppression of diseases that occur because plant growth promotion or soilborne pathogens. And therefore, these give an explanation of improvement in plant performance and reduction of disease in the presence of biochar through changing soil chemical properties and microbial composition. (Jaiswal et al., 2017). The influence of bio-char on soil properties, incidence of bacterial wilt and microbial community were characterized. In general, bio-char application efficaciously monitored through also moving specific beneficial bacteria, sequestering more nitrogen and carbon as well as decreasing pathogen abundance. The potential of bio-char in control of bacterial wilt bio-char still seems to be an attractive filler for removing pathogens considering that it can be produced economically and easily using locally available biowastes and can be recycled as a soil amendment (Chen et al., 2020 and Deng et al., 2021). Therefore, the purpose of this study is to determine the possible use of bio-char application at different levels of the soil to overcome common scab disease in potatoes. MATERIALS AND METHODS 1Potato tubers Potato seed tubers (CV. Spunta) were kindly obtained from the potato brown rot project (“PBRP”), Agricultural Research Center (ARC), Egypt. 2Soils Sandy and clayey soils are used in this experiment. The chemical properties of the soils are shown in the table (1). Chemical soil analysis was conducted by the standard methods described by (Tan, 1996). Table 1. The chemical properties of the soils Organic C (%) Total N (%) Bulk density (g/cm) Sandy soil 0.107 0.036 1.920 Clayey soil 0.829 0.035 1.225 3Bio-char Bio-char is produced by isolated furnace (El-Raie et al., 2016) from different agricultural wastes at 200 C for 2 hours using the stable gas of nitrogen which is pumped with a flow rate of 100 cm/h. The chemical properties of the biochar are shown in table (2). The bio-char particle size distribution was determined using sieves of < 1 mm using sieve shaking machine, model number 62,020. Table 2. physical and chemical properties of the bio-char