Microalgae produce many secondary metabolites that are biologically active, including compounds with antifungal activity. These could potentially function as biofungicides. Selection criteria for potential strains include having good antifungal activity against speci c phytopathogenic fungi and high biomass productivity rates to ensure su cient biomass can be generated. Water extracts were prepared from 280 strains comprising of 33 Cyanophyceae strains (13 genera), 157 Chlorophyceae strains (29 genera), 80 Trebouxiophyceae strains (19 genera), 5 Klebsormidiophyceae strains (1 genus) and 1 Zygnematophyceae strain. These were tested against 9 phytopathogenic fungi. In total, 45% of the species had antifungal activity against at least one fungal pathogen. Cyanobacteria had the highest "hit-rate" (64%), followed by the Chlorophyceae (49%) and Trebouxiophyceae (30%). Water extracts of 19 strains had fungicidal activity -these were predominantly Cyanobacteria. The Cyanobacteria displayed a wider spectrum of activity with ve strains being active (either fungicidal or fungistatic) against three or more fungal strains -Trichormis variabilis MACC-304 and Tolypothrix tennis MACC-205 had antifungal activity against 6 phytopathogens and Nostoc linckia MACC-612 inhibited 4 fungi. Each Chlorophyta strain was only active against 1-2 fungal strains. However, the daily productivity rates of Cyanobacteria were signi cantly lower than Chlorophyta strains. Further investigation of 15 Nostocales species (Families Nostocaceae, Tolypothrichaceae and Calotrichaceae) showed the Nostoc species generally had signi cantly lower biomass generation compared to other Nostocacaeae strains. The most promising strain was Tolypothrix tenuis MACC-205 which had the most potent, broad spectrum antifungal activity as well as signi cantly higher daily biomass productivity rates. Some microalgae strains (8%) had a stimulatory effect, suggesting the potential to screen strains especially from the Klebsormidiophyceae, for stimulating activity of bene cial plant growth promoting fungi. Thus, Cyanobacteria can potentially be developed as effective agricultural tools for environmentally-friendly disease management.

Microalgae produce many secondary metabolites that are biologically active, including compounds with antifungal activity. These could potentially function as biofungicides. Selection criteria for potential strains include having good antifungal activity against specific phytopathogenic fungi and high biomass productivity rates to ensure sufficient biomass can be generated. Water extracts were prepared from 280 strains comprising of 33 Cyanophyceae strains (13 genera), 157 Chlorophyceae strains (29 genera), 80 Trebouxiophyceae strains (19 genera), 5 Klebsormidiophyceae strains (1 genus) and 1 Zygnematophyceae strain. These were tested against 9 phytopathogenic fungi. In total, 45% of the species had antifungal activity against at least one fungal pathogen. Cyanobacteria had the highest “hit-rate” (64%), followed by the Chlorophyceae (49%) and Trebouxiophyceae (30%). Water extracts of 19 strains had fungicidal activity – these were predominantly Cyanobacteria. The Cyanobacteria displayed a wider spectrum of activity with five strains being active (either fungicidal or fungistatic) against three or more fungal strains - Trichormis variabilis MACC-304 and Tolypothrix tennis MACC-205 had antifungal activity against 6 phytopathogens and Nostoc linckia MACC-612 inhibited 4 fungi. Each Chlorophyta strain was only active against 1–2 fungal strains. However, the daily productivity rates of Cyanobacteria were significantly lower than Chlorophyta strains. Further investigation of 15 Nostocales species (Families Nostocaceae, Tolypothrichaceae and Calotrichaceae) showed the Nostoc species generally had significantly lower biomass generation compared to other Nostocacaeae strains. The most promising strain was Tolypothrix tenuis MACC-205 which had the most potent, broad spectrum antifungal activity as well as significantly higher daily biomass productivity rates. Some microalgae strains (8%) had a stimulatory effect, suggesting the potential to screen strains especially from the Klebsormidiophyceae, for stimulating activity of beneficial plant growth promoting fungi. Thus, Cyanobacteria can potentially be developed as effective agricultural tools for environmentally-friendly disease management.