S. Khalil
Growing media in horticultural cropping systems inhabit a number of microorganisms including bacteria and fungi. This number is low at the beginning of the growing period and increase rapidly after the introduction of the plants. Analyses using viable count indicated stability of growing media at the bacterial amount of 1010 CFU/g of fresh root and at 106 CFU/ml for the nutrient solution. Microflora inhabiting growing media can be of beneficial or harmful character. Root pathogens such as Pythium, Phytophthora and Fusarium are common pathogens in these media. In reaction disease control has focused on beneficial microorganisms as a tool for disease management. The natural role of the resident microflora, manipulation of the growing media by addition of different biocontrol strains separately or in combination or nutritional amendments to enhance the antagonistic capacity of the microflora are aspects in focus. A reduction in disease incidence by 50-100% by the resident microflora was reported. In different investigations introduction of biocontrol strains has shown a positive effect on disease reduction. However, the type of growing medium has shown to have an impact on the performance of such strains. Moreover, nutritional amendments using organic material such as compost, other C or N sources in order to increase the size of the microbial community and activity have been reported. Special attention has also been directed towards the activity of microbial communities in growing media as well as in compost during processing. Measurements of microbial respiration, nitrification process and enzyme activity have been used as indicators for microbial activity. Further, assessments of microbial communities, during the cultiva¬tion period indicated dominance of bacteria in inorganic growing media such as rockwool and fungi in the organic ones like peat. Although the microflora in the growing media plays an important role in disease control, other factors such as water content, pH and nutrients are also of importance. To define sustainable horticultural production systems, mathematical models may help to combine widely differing data as mentioned above. This might result in early warning systems. Information on molecular basis as well as bioinformatics information about disease management in growing media and composts is needed.
Khalil, S. (2014). RESILIENCE OF GROWING MEDIA. Acta Hortic. 1034, 371-378
DOI: 10.17660/ActaHortic.2014.1034.46
resident microflora, root pathogens, suppressive effect, soilless culture, biocontrol strains, compost

Acta Horticulturae