Seaweed Amendments for Reduction of Damping off Caused by Pythium ultimum

Abstract

Pythium ultimum is an oomycete which causes serious economic losses in greenhouses by causing damping off disease. Ascophyllum nodosum is known to act as a nutrient supplement and its application has shown to reduce diseases caused by microbial pathogens in plants. However, its byproduct, one that is left after the extraction, has not been tested for the same. In vitro antimicrobial assay showed that higher concentration of Ascophyllum nodosum byproduct (ABP) significantly increased Pythium ultimum growth. Its PGPR (Plant Growth Promoting Rhizobacteria - Bacillus subtilis, Pseudomonas putida and Penicillium) digested growth media amendment even at higher concentrations (3% w/w) showed significantly improved growth of cucumber seedlings as compared to the undigested ABP of same concentration, in in vivo experiments although not significantly different from control. Digested and undigested ABP did not show significant reduction in damping off caused by Pythium ultimum, and hence there was no significant increase in biochemical compounds and defence enzymes in cucumber leaf tissues as compared to the control. Further research is needed to determine the compounds present in the ABP, which can lead to a more targeted approach in utilizing it as an elicitor.