Effect of high root temperature on Bradyrhizobium-peanut symbiosis

Abstract

Three strains of Bradyrhizobium, 280A, 2209A and 32H1, that nodulated peanuts (Arachis hypogaea L.), were tested for their ability to grow and survive at elevated temperatures of up to 42°C in laboratory culture. Strain 32H1 was unable to grow at 37°C and was more sensitive to elevated temperatures than the other two strains. All three produced heat-shock proteins of molecular weights 17 kDa and 18 kDa. Two greenhouse experiments were conducted to determine the effect of high root temperature on nodulation, growth and nitrogen fixation of peanut. Two peanut varieties (Virginia cv NC7 and Spanish cv Pronto) were inoculated and exposed to root temperatures of 30 °, 37 ° and 40°C. Nodulation and nitrogen fixation were strongly affected by root temperature but there was no variety x temperature interaction. At a constant 40°C root temperature no nodules were formed. Nodules were formed when roots were exposed to this temperature with diurnal cycling but no nitrogen fixation occurred. Highest plant dry weight, shoot nitrogen content and total nitrogen were observed at a constant root temperature of 30°C. Increasing root temperature to 37°C reduced average nitrogen content by 37% and total nitrogen by 49% but did not reduce nodulation, The symbiotic performance of the strains corresponded to their abilities to grow and survive at high temperature in culture.

Rhizobia Indigenous to the Okavango Region in Sub-Saharan Africa: Diversity, Adaptations, and Host Specificity

“…On solid media, higher maximal growth temperatures were reached (Table 1), which was already observed elsewhere (48). Most type strains and all Angolan bradyrhizobia except for 45 1-4 did not grow in liquid medium at 35°C, which was also the case for two of the USDA strains.…”

Soil Biology of the Rhizobiaceae

“…Since biological systems respond to changes of temperature in predictable ways, it is not surprising that relatively high and low temperatures negatively impact rhizobia and the nodulation process. Relatively high root temperature has been shown to inhibit bacterial infection, Nz fixation ability and the general growth of legume plants (Arayankoon et al, 1990;Frings, 1976;Kishinevsky and Weaver 1992;Michiels et aI., 1994;Munevar and Wollum, 1982;Rainbird et al, 1983).…”

Selection of thermotolerant bradyrhizobial strains for nodulation of soybean (Glycine max L.) in semi-arid regions of Iran

“…Cultures were grown on a rotatory shaker at 38°C. Bacterial counts were made 5, 10 and 20 days after inoculation and isolates with a population density of more than 10 5 cells ml -1 at day 20 were considered to be thermotolerant and were used in a similar experiment at 41°C (Kishinevsky et al 1992). Similarly, rhizobia with population density of more than 10 5 cells ml -1 at day 20 at this temperature were selected as thermotolerant isolates.…”