Jonathan S. Mangmang

Response of lettuce seedlings fertilized with fish effluent to Azospirillum brasilense inoculation

The continuous use of agrochemical inputs in modern agriculture for better crop productivity has resulted in unexpected environmental impact. This issue has raised public interest in exploring environmental friendly sustainable practices. In this study, three strains of Azospirillum brasilense (Sp7, Sp7-S and Sp245) were evaluated for their impacts on the growth of lettuce seedlings grown with fish effluent (FE) as a source of nutrients. Lettuce seeds were inoculated with these strains before sowing and at transplanting, and grown under greenhouse condition with natural light. Despite the existing indigenous microflora and low level of nutrients in the FE, the A. brasilense strains survived at populations ranging from 5 to 6 cfu g− 1 of roots and altered important agronomic traits, which led to growth enhancement. In particular, inoculated seedlings showed significant increase in the number of leaves, seedling height and root length. Chlorophyll and protein content were also improved, but only with Sp7 strain. However, the expression of pathogenesis-related protein, i.e., peroxidase, and level of endogenous indole-3-acetic acid increased by more than 50% in response to inoculation with the strains. Azospirillum inoculation also showed little or no adverse impact on the FE bacterial community indicating that it can be incorporated into a system that uses FE as a nutrient source, e.g., aquaponics. Thus, A. brasilense could be a valuable agent to help maximize the usefulness of FE or wastewater from freshwater aquaculture to further support plant growth.

Germination Characteristics of Cucumber Influenced by Plant Growth–promoting Rhizobacteria

ABSTRACT Plant growth–promoting rhizobacteria (PGPR) represent a wide genera of rhizospheric bacteria that, when introduced in association with the host plant at optimum concentration, can enhance plant growth. Experiments were conducted to determine the germination response of cucumber (Cucumis sativus L.) to PGPR inoculation. Seed were inoculated with strains of Azospirillum brasilense Sp7, Sp7-S, and Sp245, Herbaspirillum seropedicea, and Burkholderia phytofirmans PsJNT. Germination was increased by up to 9% by strains of A. brasilense Sp7 and Sp245 and H. seropedicea. All PGPR strains consistently enhanced the germination vigor index; plants produced longer and heavier roots. These PGPR benefit cucumber germination.

Early Seedling Growth Response of Lettuce, Tomato and Cucumber to Azospirillum brasilense Inoculated by Soaking and Drenching

Mangmang J.S., Deaker R., Rogers G. (2015): Early seedling growth response of lettuce, tomato and cucumber to Azospirillum brasilense inoculated by soaking and drenching . Hort. Sci. (Prague), 42: 37–46. This study evaluated the effects of three A. brasilense strains (i.e. Sp7, Sp7-S and Sp245) on the early seedling growth of lettuce, tomato and cucumber. Seeds were inoculated by soaking and drenching before and after sowing, respectively. Results show that inoculation effect varied greatly with plant species, inoculation methods and PGPR strains which could be dependent on inoculum concentration and IAA (indole-3-acetic acid) production. Generally, the magnitude of inoculation impact on the early growth of vegetables was more pronounced with Sp7-S, followed by Sp245 and Sp7. In particular, Sp7-S and Sp245 strongly enhanced root and shoot growth, germination value and vigour of tomato when inoculated by soaking. Sp245 increased the level of endogenous plant IAA of cucumber and lettuce. Despite the diverse crop responses to inoculation methods, soaking appeared to be a better technique, and majority of the strains demonstrated more consistent beneficial effects on tomato.

Optimal plant growth-promoting concentration of Azospirillum brasilense inoculated to cucumber, lettuce and tomato seeds varies between bacterial strains

Azospirillum brasilense is a well-known plant growth-promoting rhizobacteria (PGPR) that can have positive impact on plant growth when present in sufficient density. The production of phytohormones by Azospirillum has been proposed as one of the major mechanisms responsible for the observed plant growth effects. In particular, this plant growth-promoting effect could be mediated by IAA (indole-3-acetic acid), a phytohormone produced by Azospirillum in substantial amount, because the effect of inoculation with higher inoculum density on root morphology mimicked the increasing concentration of exogenous IAA applied to the seed. This study evaluated the effect of inoculation with different bacterial concentrations of three A. brasilense strains (Sp7, Sp7-S and Sp245) on the early seedling growth and endogenous plant IAA of cucumber, lettuce and tomato. Seeds were inoculated with 8, 7 and 6 log cfu ml−1 of each strain before germinating in Petri dishes. The early seedling growth of vegetables was affected by ...

Response of Cucumber Seedlings Fertilized with Fish Effluent to Azospirillum brasilense

ABSTRACT An emphasis on reducing use of agrochemicals and recycling organic waste to alleviate pollution and nutrient discharge to the environment has prompted exploration of beneficial microbes and aquaculture wastewater in agriculture production. A study was conducted to investigate effects of strains Sp7, Sp7-S, and Sp245 of Azospirillum brasilense on cucumber (Cucumis sativus L.) seedlings fertilized with fish effluent. Cucumber seed were inoculated prior to germination and transplanting. Seedlings were grown in a greenhouse with natural light. Inoculated seedlings produced longer roots, greater root biomass, and higher total phosphorus, endogenous plant indole-3-acetic acid, and peroxidase activities. Inoculation caused small changes in the fish effluent bacterial community, indicating that these strains can be integrated into a production system utilizing fish effluent as a fertilizer. A. brasilense could be a valuable agent to help maximize the usefulness of aquaculture wastewater to support plant growth.