Assessment of compost for suppression of <i>Fusarium oxysporum</i> and improving<i> Zea mays</i> and <i>Hibiscus sabdarriffa</i> resistance to wilt diseases

Abstract

The present research was conducted to evaluate the compost effectiveness on Zea mays and Hibiscus sabdarriffa under Fusarium wilt disease. Compost physical, chemical and biological characters were monitored weekly during the ripening process. Both coliform and nematode were tested. Finally, the effect of compost on pathogenic Fusarium was examined within Z. mays and H. sabdarriffa in soil amended with 10% compost. Biochemical tests and antioxidant enzyme activities were determined for all the treated plants. The values of organic carbon recorded a percentage of 3.8%, while nitrogen (N), phosphorus (P) and potassium (K) values recorded 1.7, 4.6 and 5.6% higher than the commercial compost. The concentrations of nickel (Ni), copper (Cu), zinc (Zn), manganese (Mn), cobalt (Co), cadmium (Cd) and lead (Pb) in compost were below the threshold standard values. The compost is free of nematodes and coliform bacteria at maturity stage. Microbial population densities were usually high for Bacillus sp. compared to other microorganisms. In infected Z mays with compost, shoot height, fresh and dry weight increased significantly (62, 248 and 130%) and H. sabdarriffa also recorded increase in the same plant criteria. In infected Z. mays, a significant increase in catalase (CAT) and ascorbate peroxidase (APX) activities was recorded (162 and 150%). For H. sabdarriffa there was a significant decrease in APX activity (35%) with compost, while no significant differences in peroxidases (PODs) activity for both plants. In case of infection, a significant decrease was observed for both Z. mays and H. sabdarriffa compared to infected plants without compost. The observed disease suppression in compost-amended soil was associated with the reduction in soil pathogen population and increase in microbial activity of composts. Moreover, diversification of different organic materials in compost enhanced the activation of the microbial population in soil that eventually increases disease suppressiveness and effectively controlling Fusarium wilt.

Key words: Antioxidant enzymes, compost, Hibiscus sabdarriffa, Zea mays.