Germination test for the evaluation of plant-growth promoting microorganisms

There is an increased interest for finding strains able to contribute to plant nutrition and health, since these are desirable for the formulation of agricultural bioinoculants. Obtaining a safe and efficient product requires exhaustive evaluations from which most methods used for this purpose involve the use of substrates or are established under uncontrolled conditions, so that various factors can mask the results of the plant-microorganism interaction. In vitro methods mostly involve the use of Petri Dishes (PD) but limit the results to seed germination. Other methods of germination involve the use of acrylic boxes (GB) allowing for better plant development, but are little known. Methods such as ISTA are widely used to evaluate the physiological quality of seeds in productive terms. Despite their efficiency, these methods have not been previously used to evaluate the effect of plant-microorganism interaction on crops. In the present study, modifications were made to the germination between paper of ISTA (BP) method, and were compared to the PD anf GB methods to evaluate the impact of the bacterium Serratia liquefaciens 385 and the yeast Clavispora lusitaniae Y35 on maize, bean and squash. Through the evaluation of physiological parameters in seed and seedling, the results clearly showed the superiority of the BP method to evaluate the effect of microorganisms since it allows observing a better development in the seedlings in terms of growth of the plumule, a better architecture of the radical system in which the emergence of adventitious secondary roots and differentiated radical hairs is observed in comparison with seedlings obtained under the other methods. Similarly, it was possible to observe the different effects on each of the three crops with respect to the inoculation of the bacteria and yeast. These results were significantly better in seedlings obtained in the BP method independently of the type of crop evaluated, considering the BP method suitable to be applied in large-scale bioprospecting plant-growth-promoting microorganism studies.