Survival of Bradyrhizobium in sterilized alternative inoculant carriers

Abstract

A determination was made of the survival of Bradyrhizobium sp. (Clitoria) in alternative substrates submitted to two forms of sterilization. Substrates composed of diatomaceous material, coconut powder fiber, vermiculite, vinasse and urban compost waste were compared with the conventional substrate (turf), using the strain UMKL 58 (Malaysia NIFTAL). The evaluation of the viable Bradyrhizobium sp. cells was made on the different materials utilized by means of the dilution in plates or plant infection method (cunhã-Clitoria ternatea L.). The effect of sterilization by autoclaving and gamma radiation (5Mrad) was evaluated at intervals of 0, 12, 30, 60 and 90 days. The irradiated turf showed a better growth and survival of the bacteria, with a consistent performance in relating the two evaluation methods. The survival of the bacteria in the diatomaceous substrate was comparable to that of turf as was its effect on nodulation and plant growth. The other carriers presented inferior results, although showing possibilities of being used as alternative substrates.