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Effects of corn steep liquor on productivity, microbial dynamics and pathogen regulation of tomatoes (Solanum lycopersicum L.) grown under hydroponic systems. Essay Example

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Saad Abdelrahman – PhD Proposal – (add date here)6

Proposed PhD Title: Effects of corn steep liquor on productivity, microbial dynamics and pathogen regulation in tomatoes (Solanum lycopersicum L.) grown under hydroponic system.



21.0 Introduction

42.0 Research Objectives

53.0 Materials and Methods


5Growing Conditions

6Part 1: Investigating the effect of CSL on tomato productivity

6Part 2: Investigating the effect of CSL on pathogen regulation

7Statistical Analysis


1.0 Introduction

The production of vegetables in hydroponic cropping systems is a resource efficient and innovative technology of producing crops of high quality with increased yield per unit area to meet the ever increasing world food demand (Takushi, 2014). According to Fontana, Nicola, & Tibaldi, 2008, the use of water by crops grown in greenhouse hydroponic systems can be saved by up to 70-90% compared to the same crops grown under field conditions. The potential spread of root pathogens are, however, one of the main constraints regarding hydroponic systems. In the recirculation of nutrient solutions, a single diseased plant could potentially be the source of infection for the entire crop (Maheshwar, 2011). Oomycetous pathogens, such as Pythium and Phytophthora, are particularly destructive diseases due to their production of motile zoospores that flourish in aquatic environments (Jensen & Lumsden, 1999). It is thought that 98% of organic material is released in hydroponic culture is derived from the apex of the crop root (Jankauskienė, Brazaitytė, & Viškelis, 2015). Control of root pathogen outbreaks could be through sustenance of a stable and high level of general microbiota (Rosberg, 2014). In recent studies, it has been found that organic fertilizers can have suppressive effects on pathogens of plants growing in soilless mediums (Chinta et al., 2014). Microorganisms have also been observed to exhibit antagonistic activity to diseases in organic soilless systems (Fujiwara, et al., 2013). Therefore, it is of great importance to understand how biotic and abiotic factors affect the indigenous, root associated microbiota.

Hydroponic culture systems are cultivation techniques are increasingly taking up the place of traditional agricultural practices (Maheshwar, 2011). These systems have been developed in order to manage soil-borne pathogens. For example, hydroponic systems are currently used for growing lettuce crops (Rosberg, 2014). These systems have several key advantages, such as preventing soil-borne diseases, inhibiting pests and weeds, and decreased use of herbicides and pesticides (Liggett & Koffler, 1948). While Chinta, Eguchi, Widiastuti, Shinohara, & Sato, 2015, report that hydroponic system were originally developed to control soil borne diseases, recent studies have found that hydroponic systems are not free of the risk of disease (Chinta et all., 2014). This calls for the need for further research to address the propagation of crop diseases in hydroponic systems.

One system for potential control of disease in hydroponic systems is corn steep liquor (Takushi, 2014). This PhD research project proposes to assess the use of corn steep liquor to control root rot disease in tomatoes grown in a soilless system, and associated microbial dynamics that underpin potential resistance to the root rot disease.

2.0 Research Objectives

The main objective of this thesis is to find out the effects of CSL on productivity, microbial dynamics and pathogens regulation on tomatoes (Lycopersicum esculentum L.) grown under hydroponic culture. The specific objective will be:

  1. To investigate the effect of CSL on the development of root rot disease caused by Fusarium oxysporum f.sp. lactucae (FOL) in hydroponic cultures of tomatoes.

  2. To study the microbial dynamics and control of pathogens in tomatoes grown in hydroponic systems.

3.0 Materials and Methods


Cultivation will be done on an organic cultivation system. Treatments of Solanum lycopersicum
L. will then be performed using CSL on one category of the plants. The second category of seeds will be untreated with CSL. The treated seeds will be grown on 23(L) x 23(D) x 28(H) mm CSL cubes as the growing substrate (soilless media), while the untreated seeds will be grown on organic soil media. After five weeks, the tomato seedlings will be transplanted in to greenhouses; the treated seedlings will be planted on a CSL hydroponic system, while the untreated category will be planted on organic soil.

Growing Conditions

The entire study will be done in a greenhouse. The density of the transplanted plants in the greenhouse will be maintained at 2.5 plants per square meter. Drip irrigation will be used to provide water for the plants and fertilized using “Nutrifol”, ammonium and calcium nitrate, and magnesium sulphate, considering the stage of growth. They will also be sprayed with a nutrient solution. The tomato vegetation will take a period of eight months after transplantation after transplantation.

Before transplantation, the seedlings will be sub-divided into four groups; two groups from treated category and two other groups from the treated category. This will give two groups of plants from each category. One plant group from each category will be investigated for effect of CSL on productivity and another group for pathogen regulation as indicated below.


(with CSL)


(without CSL)





Part 1: Investigating the effect of CSL on tomato productivity

Biometric Measurements

During the study, the heights of the plants in the two categories (CSL treated and untreated category) will be measured three times during the period of vegetative growth after 10 days of transplantation in the greenhouse. The number of leaves on each plant will also be counted. This will assess the rate of plant growth (Jankauskienė, Brazaitytė, & Viškelis, 2015).

Plant yield

At every harvest, the tomato yield from each category will be recorded. Harvesting will be done three times a week and the fruits separated into marketable ones and non-marketable fruits. Aggregation of each harvest will give the total yield in each category.

Part 2: Investigating the effect of CSL on pathogen regulation

Preparation and inoculation of fungal agent

Botrytis cinerea (gray mould) will be cultured using potato dextrose agar medium for a period of one week in an incubator at 25oC. The inoculum will then be prepared to 4 mm mycelia discs.

Host plant preparation

One group of treated seedling leaf samples and another group of untreated seedling leaf samples will then be introduced to B. cinerea by attaching the mycelial discs to the lower parts of the plant leaves (Chinta, Eguchi, Widiastuti, Shinohara, & Sato, 2015). The leaf samples will be left to incubate at a temperature of 25oC for up to 5 days. The diameter of B. cinerea lesions will be measured at the end of the incubation period.

Statistical Analysis

The tomato data will be analyzed by a 2-tailed unpaired t-test. All the analysis will be performed using excel software. Significant of the effect of CSL will be defined as P < 0.05.


Chinta, Y. D., Eguchi, Y., Widiastuti, A., Shinohara, M., & Sato, T. (2015). Organic hydroponics induces systemic resistance against the air-borne pathogen, Botrytis cinerea (gray mould). Journal of Plant Interactions, 243-246.

Chinta, Y., Kano, K. Widiastuti, A. Fukahori, M. Kawasaki, S. Eguchi, Sato, T. (2014). Effect of corn steep liquor on lettuce root rot (Fusarium oxysporum f.sp. lactucae) in hydroponic cultures. Journal of the science of food and agriculture, 2317-23.

Fontana, E., Nicola, S., & Tibaldi, G. (2008). Tomato production systems and their application to the tropics. International Symposium on Tomato in the Tropics, 27-34.

Fujiwara, K., Iida, Y., Iwai, T., Aoyama, C., Inukai, R., Ando, Shinohara, M. (2013). The rhizosphere microbial community in a multiple parallel mineralization system suppresses the pathogenic fungus Fusarium oxysporum. Microbiology Open, 997–1009.

Jankauskienė, J., Brazaitytė, A., & Viškelis, P. (2015). Effect of Different Growing Substrates on Physiological Processes, Productivity and Quality of Tomato in Soilless Culture. Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Lithuania, 99-117.

Jensen, F. D., & Lumsden, R. D. (1999). Integrated Pest and Disease Management in Greenhouse Crops. New York: Springer Science.

Liggett, R. W., & Koffler, H. (1948). Corn steep liquor in microbiology. Bacteriological reviews, 297–311.

Maheshwar, D. K. (2011). Bacteria in Agrobiology: Crop Ecosystems. New York: Springer .

Rosberg, A. K. (2014). Dynamics of root microorganisms in closed hydroponic cropping systems. Faculty of Landscape Architecture, Horticulture and Crop Production Science, Department of Biosystems and Technology, Alnarp, 29-36.

Takushi, S. (2014, March 2). Food Grown Hydroponically Protected From Root Rot. Retrieved from Guardian Liberty Voice: http://guardianlv.com/2014/03/food-grown-hydroponically-protected-from-root-rot/