Suppression of Rhizoctonia solani damping-off in Soybean (Glycine max L.) by plant growth promoting rhizobacteria strains

Abstract

Rhizobacteria (PGPR) for its antagonist activity and suppression of Rhizoctonia solani AG2-3 causal agent of damping-off disease in soybean plant. Strains of Bradyrhizobium japonicum 110, Bacillus megaterium var. phosphaticum B6, Methylobacterium aminovorans ML3, M. rhodinum ML12, and Trichoderma viride 1433 species were used in the present study. In vitro, all tested strains showed a notable ability to inhibit mycelial growth of R. solani on different growth media. While, T.viride and M. rhodinum showed the highest rate of antagonism against R. solani. In vivo, in generally, PGPR treatments notably decreased damping-off and increased healthy plants, as compared to the control (infested soil). As compared to the uninoculated NPK fertilized control, higher growth parameters for shoot and root dry weight (g plant-1), number of nodules and dry weight of nodules (mg plant-1), chlorophyll content and NPK % of shoot and root, were recorded for the T 11 (inoculation with B. japonicum 110 + M. aminovorans ML3 + B. megaterium var. phosphaticum B6 + T. viride) and T 12 (inoculation with B. japonicum 110 + M. rhodinum ML12 + B. megaterium var. phosphaticum B6 + T. viride) treatments. Seeds yield of soybean plants attained higher values with all tested treatments. The obtained results of PGPR bacterial effects on damping-off disease and growth parameters of soybean recommend their use as an alternative tool rather than chemical fungicides. Such biocontrol approach should be included in the integrated management programs.

Management of Charcoal Rot (Macrophomina phaseolina) Infection in Geranium (Pelargonium graveolens L) Using Biocontrol Agents and Essential Oils

“…Biological control introduces several advantages over other types of pathogen control such as: high specificity against targeted pathogens, low cost of production and application as well as ecofriendly. The antagonistic mechanisms through which biological control agent affect pathogens community are variable and not always clear, but generally may be related to one of the following: (1) direct parasitism leading to death of the pathogen; (2) competition on nutrients and space and (3) production of cytotoxic compounds such as antibiotics or toxic volatiles (Heydari and Pessarakli 2010;Omara et al 2018).…”

“…The suggested strategy used in this case may by the production of siderophores leading to iron starvation which affect pathogen growth. Previous studies have demonstrated that Trichoderma species can be used as a biocontrol agent in controlling a number of plant diseases with high efficacy (Kucuk and Kivanc 2003;Omara et al 2017Omara et al , 2018Elkhwaga et al 2018). Also, the light microscope image illustrates the possible mechanism used by the Trichoderma to inhibit fungal growth where the affected pathogen mycelia appeared empty from cytoplasm and its component in addition to loss of septation, so it is likely that the mechanism involved in this case is related to the hydrolytic enzymes.…”

“…There are several studies about improving growth dynamics and increased availability of nutrients in the rhizosphere (Patten and Glick 2002). It is clearly observed that B.subtilis and T. harzianum treatments and essential oils caused sharp increase in vegetative growth such as plant height, branches, leaves number, and oil yield (Lu et al 2017;Sadeghi et al 2017;Omara et al 2018).…”

“…On the other hand, biological control and essential oils provide an ecofriendly solution alternative to chemical control. For biological control, several microbes like Bacillus pumilus, B.subtilis and B.licheniformis as well as Trichoderma viride and Pseudomonas species have been considered as a biocontrol agents against pathogens through their ability to serve as a source of bioactive compounds and plant growth promoting such as antibiotic production, colonization site competition, production of hydrogen cyanide, hydrolytic enzymes, siderophores, ammonia, fluorescent pigments and/or antimicrobial volatiles (Keshavarz-Tohid et al 2017;Sadeghi et al 2017;Lu et al 2017;Omara et al 2018). For essential oils like Pelargonium roseum, Carum carvi, Pimenta dioica, Cymbopogon nardus and Thymus vulgaris have been considered antifungal activity which may be attributed to their major ingredients or a synergistic or antagonistic effect with various compounds.…”

Siderophore production by Bacillus subtilis MF497446 and Pseudomonas koreensis MG209738 and their efficacy in controlling Cephalosporium maydis in maize plant

“…To protect against soilborne diseases, it is better to use chemical pesticides in controlling these diseases but, these are expensive as well as not environmental friendly. So, many researchers have used plant growth-promoting rhizobacteria (PGPR) as biological control against late wilt disease associated with the maize rhizosphere which could improve plant health, reduce chemical pesticides, and develop efficient biological control strategies (El-Mehalowy et al 2004 and Ashour et al 2013 ; Omara et al 2017 , 2018 ). Therefore, recently, biological control by PGPR has been adopted on a commercial scale by using a number of experimental approaches.…”