Effect of Cyanobacteria on Reducing Damping-off and Root Rot Incidence in Lupine Plants, New Valley Governorate, Egypt

This study was conducted to investigate the suppression effect of four cyanobacteria species viz. Nostoc muscorum, Oscillatoria agardhii, Spirulina platensis and Anabaena sphaerica, against Rhizoctonia solani, Fusarium solani and Macrophomina phaseolina as the causal agent of lupine damping-off and root rot diseases under greenhouse and field conditions. Cyanobacterial secondary metabolites have a diverse antagonistic activity that lead to disintegration of microbial growth. All cyanobacteria were significantly suppressed of the tested pathogenic fungi in vitro. The reduction in the linear growth of the tested fungi was differed depending of type of solvent extract. Acetone extract of O. agardhii was recorded the highest growth reduction of all tested pathogenic fungi.

Contents of indole actetic acid (IAA), total phenol and flavonoid compounds and protease enzyme activity showed an increase in the extracts of N. muscorum, O. agardhii than the extracts of S. platensis and A. sphaerica. Also, acetone extract of all tested cyanobacteria was recorded the highly secondary metabolites than methanol and water extracts. Treated lupine seeds (cv. Giza 1) with any of the cyanobacteria extracts before sowing results significantly reduction of damping-off and root rot incidence compared with untreated seeds under pot and field conditions. On the other hand, treating lupine seeds with cyanobacteria extracts increased plant growth and yield parameters during both growing seasons (2014-2015 and 2015-2016). In general, O. agardhii followed by N. muscorum highly reduced damping-off and root rot incidence both in pot and field experiments as well as increase of growth (pant height and No. of branches plant-1) and yield parameters (No. of pods plant-1, No. of seed plant-1, seed index (gm) and total yield fed.-1 (Kg) in field. Also, acetone extract more effective in this respect than methanol or water extracts.