Environmental influences on Bradyrhizobium sp. survival and nodulation potential on peanut

Abstract

Peanut (Arachis hypogaea) is an important legume crop currently grown in West Texas and obtains much of its nitrogen through a symbiotic relationship with compatible Bradyrhizobium strains. However, West Texas soils may not contain the specific bradyrhizobial strain required and, therefore, inoculation is essential. The success of inoculation is often limited by several factors, including high sandy soils, and high soil temperature commonly found in West Texas. The goal of this research was to determine if these environmental conditions have an effect on the survivability of bradyrhizobial inoculants and the ability of inoculants to infect peanut plants under these conditions. Three commercial bradyrhizobia inoculants were tested for their ability to survive at temperatures 30°, 37°, and 40°C and pHs 6, 7, and 8 in laboratory culture. The inoculants were differentially affected in their ability to survive the higher temperature regimes. Experiments were also conducted to determine the effect of high root temperature on nodulation of peanut. One peanut variety (Flavor Runner 458) was inoculated and exposed to diurnal temperatures of 25°C/10°C and 40°C/25°C. Nodulation was strongly affected by the high temperature regime, while pHs tested did not significantly influence inoculant effectiveness. Results have practical implications for West Texas peanut farmers who plant into hot, dry soil even if fields are irrigated within 24 hours.