Soil Amendments and Water Moisture on the Control of Tomato Bacterial Wilt Caused by Ralstonia Solanacearum

Bacterial wilt is one of the most severe tomato diseases worldwide and Ralstonia solanacearum is determined to be the pathogen responsible for its spread. Soil amendments such as calcium cyanamide and herb residues have both been proved to be high potential for tomato bacterial wilt control. Disinfection effect and heat generated during the decomposition processes of calcium cyanamide and herb residues effectively controlled Ralstonia solanacearum while rare studies are conducted on their mechanisms. In this paper, calcium cyanamide was applied in combination with herb residues under solar greenhouse condition to evaluate their integrated control effects on tomato bacterial wilt. It promoted rapid temperature increases to above 40°C within 15 days. R. solanacearum was decreased to the lowest population (5.38 log cfu/g) at 20 d and no recovery was found after treatment. In addition, the optimal soil moisture content for pathogen control was also discussed. Under soil moisture of 85% field capacity, tomato treated with calcium cyanamide and herb residues had the most favorable growing performance with wilt of 3.6% and wilt control efficiency of 79.8%. Introduction Tomato has a large consumption in China as fruit and ingredient in dishes. Due to large nutrients input and vegetable production, continuous cropping obstacle caused by soil salinity, soil pathogens, soil acidification and nutrition accumulation becomes inevitable and more severe in tomato cultivation (Wang et al. 2010). Researches have shown that continuous cropping of tomato is harmful to soil ecological balance as well as microbial community diversity (Qu and Wang 2008, French 1994, Simujide et al. 2013). Ralstonia solanacearum (R. solanacearum), the causal organism of tomato bacterial wilt (TBW), is believed to be the main cause of the obstacle in tomato’s cultivation (Qu and Wang 2008). Chemical disinfection and bioremediation have been applied for the control of TBW (French 1994). Calcium cyanamide (CaCN2), as the most traditional chemical disinfectant, was reported to have suppressive ability of TBW due to its strong alkalinity. Soil noxious microbes and pest can also be eliminated by heat generated during the hydrolyzate of CaCN2 (Simujide et al. 2013). The combination of CaCN2 with organic fertilizer (OF) is an innovative approach for the control of TBW. Organic fertilizer is beneficial for heat disinfection through the effect of fermentation (Lian et al. 2014). In addition, as the food source and shelter for soil beneficial microorganisms (BMs), OF is helpful for the restoration of soil microbial communities after treated with CaCN2 (Gorissen et al. 2004). *Author for correspondence: . Nanjing Institute of Agricultural Science, Nanjing 210000 China