Isolation, characterization, and formulation of antagonistic bacteria for the management of seedlings damping-off and root rot disease of cucumber

Abstract

Antagonistic bacteria are common soil inhabitants with potential to be developed into biofungicides for the management of seedling damping-off, root rot, and other soil-borne diseases of various crops. In this study, antagonistic bacteria were isolated from a commercial potato field and screened for their growth inhibition of fungal and oomycete pathogens in laboratory tests. The biocontrol potential of the 3 most effective antagonistic bacteria from the in vitro tests was evaluated against seedling damping-off and root rot of cucumber caused by Pythium ultimum. Based on phenotypic characteristics, biochemical tests, and sequence analysis of 16S-23S rDNA gene, the 3 antagonistic bacteria were identified as Pseudomonas fluorescens (isolate 9A-14), Pseudomonas sp. (isolate 8D-45), and Bacillus subtilis (isolate 8B-1). All 3 bacteria promoted plant growth and suppressed Pythium damping-off and root rot of cucumber seedlings in growth-room assays. Both pre- and post-planting application of these bacteria to an infested peat mix significantly increased plant fresh masses by 113%-184% and percentage of healthy seedlings by 100%-290%, and decreased damping-off and root rot severity by 27%-50%. The peat and talc formulations of these antagonistic bacteria applied as seed or amendment treatments to the infested peat mix effectively controlled Pythium damping-off and root rot of cucumber seedlings and enhanced plant growth. The survival of all 3 antagonistic bacteria in peat and talc formulations decreased over time at room temperature, but the populations remained above 10(8) CFU/g during the 180-day storage period. The peat formulation of a mixture of 3 bacteria was the best seed treatment, significantly increasing the plant fresh masses by 245% as compared with the Pythium control, and by 61.4% as compared with the noninfested control. This study suggests that the indigenous bacteria from agricultural soils can be developed and formulated as biofungicides for minimizing the early crop losses caused by seedling damping-off and root rot diseases.

Genetic, physiological and biochemical characterization of Bacillus sp . strain RMB7 exhibiting plant growth promoting and broad spectrum antifungal activities

“…A recent study have shown 27%-50% suppression of Pythium damping-off and root rot of cucumber seedlings along-with 113%-184% increase in plant fresh weight by combined application of two Pseudomonas spp. and B. subtilis [41]. But the inoculation of B. subtilis RMB7 alone resulted in 400-600 folds increase in plant biomass and >85% disease suppression in Arugula plants showing extensively high potential for disease control as well as plant growth promotion.…”

EVALUASI EFIKASI FORMULA Pseudomonas fluorescens UNTUK PENGENDALIAN PENYAKIT LAYU BAKTERI (Ralstonia solanacearum) NILAM

“…Pada benih kacang tanah P. fluorescens memerlukan waktu untuk menunjukkan peningkatan populasi P. fluorescens di rizosfer kacang tanah, seiring dengan meningkatnya umur tanaman (Meena, 2011). Begitu pula aplikasi formula P. fluorescens pada benih tanaman kapas efektif mengendalikan penyakit rebah kecambah pada bibit kapas (62,5%) (Ardakani et al, 2010), dan aplikasi P. fluorescens 9A-14 dan Pseudomonas sp 8D-45 dalam formula bentuk talk pada benih tanaman ketimun efektif mengendalikan penyakit rebah kecambah dan busuk akar bibit (Pythium sp) ketimun dengan tingkat pengendalian 61,04% (Khabbaz and Abbasi, 2014). Berarti efektifitas kombinasi P. fluorescens Pf19 dan Pf101 untuk menekan patogen juga ditentukan oleh umur tanaman.…”

“…P. fluorescens dapat berperan sebagai Plant Growth Promoting Rhizobacteria (PGPR) yang berasosiasi dengan akar tanaman, menghasilkan senyawa auksin, giberalin dan sitokinin (Landa et al, 2002), senyawa pelarut fosfat dan IAA (Ramyasmruti et al, 2012), efektif memacu pertumbuhan tanaman (Van Loon, 2007dalam Khaeruni et al, 2013. Aplikasi formula talk P. fluorescens 9A-14, Pseudomonas sp 8D-45 dan Bacillus subtilis B-1 (antagonistik) pada benih ketimun efektif meningkatkan pertumbuhan tanaman (Khabbaz and Abbasi, 2014). Formula P. fluorecsens dan B. subtilis pada benih kapas efektif meningkatkan perkecambahan benih dan pertumbuhan bibit (Ardakani et al, 2010).…”

“…Aplikasi rizobakteria indigenus pada benih tomat efektif mengendalikan layu fusarium (61,14%) dan meningkatkan hasil tanaman (Khaeruni et al, 2013). Aplikasi formula talk P. fluorescens 9A-14, Pseudomonas sp 8D-45 pada benih ketimun efektif mengendalikan penyakit rebah kecambah dan busuk akar (Pythium spp) serta meningkatkan produksi berat basah tanaman ketimun dengan peningkatan 245% (Khabbaz and Abbasi, 2014). Formula P. fluorescens Pf1 disimpan sampai 180 hari masih efektif untuk menekan perkembangan penyakit layu fusarium dan meningkatkan hasil buah tomat (Manikandan et al, 2010).…”

Isolation and characterization of antagonistic bacteria with the potential for biocontrol of soil-borne wheat diseases

“…are important based on its ability to aggressive colonizers of the rhizosphere of various crops and synthesize several metabolites that are inhibitors of some enzymes or membrane proteins and exert an antagonistic effect (Schippers et al 1987). In addition, nonpathogenic bacteria, fungi, and Actinomycetes belonging to the genera Trichoderma, Fusarium, Streptomyces, and Serratia have been used as potential biocontrol agents against damping-off and root rot pathogens, and other soil-borne pathogens (Someya et al 2003;Minerdi et al 2009;Khabbaz and Abbasi 2014).…”