Formulation development of the deleterious rhizobacterium Pseudomonas trivialis X33d for biocontrol of brome (Bromus diandrus) in durum wheat

Aim To develop an appropriate formulation of the deleterious rhizobacterium Pseudomonas trivialis X33d and to evaluate its effectiveness to reduce brome growth. Methods and Results Two formulations of Ps. trivialis X33d, a semolina-kaolin granular formulation (Pesta) and talc-kaolin powder, were prepared and their effectiveness in reducing brome growth was evaluated. Both brome suppression and cell viability of X33d were higher in Pesta granular formulation than in talc-kaolin powder one. The impact of storage temperature and the addition of adjuvants (sucrose and oil) to the granular formulation of X33d were assessed in order to improve the shelf life of the formulation. The longest viability was found in formulated product supplemented with adjuvants and stored at 4 degrees C. The effect of Pesta granules supplemented with adjuvants and stored for 6 months at 4 degrees C on brome and wheat growth under controlled and greenhouse conditions was evaluated. The X33d formulation in Pesta increased the growth of wheat and reduced brome growth. Conclusion Our results indicate that Ps. trivialis X33d formulated in Pesta has potential as a bioherbicide to control brome. Significance and Impact of the Study Because of the impracticality of applying bacterial cell suspension on a large scale, the use of Pesta granules of X33d against brome could help in achieving a sustainable agriculture application of a bioherbicide.