Integrated effects of abiotic stresses on inoculant performance, legume growth and symbiotic dependence estimated by 15N dilution

Abstract

Temperature, water, salinity, sodicity, acidity and nutrient disorders are major abiotic stresses that can affect legume growth or the establishment and function of the legume-Rhizobium symbiosis. We have examined the literature where the application of the 15 N isotope dilution methodology permits the effect of individual abiotic stresses to be independently and quantitatively separated into plant growth-mediated and BNF (biological N 2 fixation)-mediated components. The response of the symbiosis to a particular stress depends on a host of factors, including legume genotype, cultivar, Rhizobium inoculant, climatic conditions, and the duration, timing and severity of the stress. Published data are analysed in terms of the above variables and their interactions. As a general rule, severe stress inhibits both legume dry matter (DM) and the proportional dependence of the legume on BNF as a source of N. The symbiosis is resilient to low to moderate stress, but there may still be a penalty on legume DM. Gaps in knowledge are identified, and general guidelines on the identification and amelioration of abiotic stresses are provided.

Adaptation of grain legumes to climate change: a review

“…Nitrogen nutrition is often sub-optimal and leads to unstable and low yields. Indeed, symbiotic N 2 fixation is highly sensitive to environmental stresses (Sprent et al 1988), especially to temperature, water, salinity, sodicity, acidity, and nutrient disorders (Chalk et al 2010;Hungria and Vargas 2000;Jayasundara et al 1998). As such, climate change may affect symbiotic fixation either directly by impairing Rhizobia survival, Rhizobia competitiveness, nodule formation, growth, or activity, or indirectly by modifying carbon supply to nodules.…”

Plant N Fluxes and Modulation by Nitrogen, Heat and Water Stresses: A Review Based on Comparison of Legumes and Non Legume Plants

“…The optimum temperatures for N 2 fixation vary widely between legumes species and reflect their environmental adaptation (Chalk et al, 2010). For temperate legumes the optimum temperature for N 2 fixation is between 15 and 25°C (Sprent et al, 1988), while for tropical legumes, upper limits for N 2 fixation range between 27 and 40°C (Hungria & Vargas, 2000).…”

“…For temperate legumes the optimum temperature for N 2 fixation is between 15 and 25°C (Sprent et al, 1988), while for tropical legumes, upper limits for N 2 fixation range between 27 and 40°C (Hungria & Vargas, 2000). High temperatures decrease significantly the survival of rhizobia (Chalk et al, 2010;Hungria & Vargas, 2000) and affect the competitive ability of Rhizobium strains (Bordeleau & Prévost, 1994;Chalk et al, 2010). Rhizobium is most vulnerable to stress when it is free-living outside the symbiotic relationship (Chalk et al, 2010).…”

“…High temperatures decrease significantly the survival of rhizobia (Chalk et al, 2010;Hungria & Vargas, 2000) and affect the competitive ability of Rhizobium strains (Bordeleau & Prévost, 1994;Chalk et al, 2010). Rhizobium is most vulnerable to stress when it is free-living outside the symbiotic relationship (Chalk et al, 2010). So, repeated inoculation and higher rates of inoculation of grain legumes may be needed to guaranty optimum N 2 fixation in tropical soils (even when the strain is already present in the soil) (Hungria & Vargas, 2000).…”

Dinâmica de rizóbios em solo do cerrado de Roraima durante o período de estiagem

“…De forma geral, o solo é considerado sob déficit hídrico quando os teores de umidade estão abaixo de 50% da capacidade de campo sendo comum nessa condição o aparecimento de efeitos negativos ao processo de FBN (Chalk et al 2010). Os longos períodos de estiagem, com potencial hídrico do solo abaixo de -0,5 MPa representam uma condição que tende a reduzir a densidade populacional de rizóbios no solo (Hungria e Vargas 2000;Sadowsky 2005); embora algumas estirpes sejam capazes de sobreviver mesmo em condições áridas (Waldon et al 1989).…”