Nonspecific responses in plant growth, yield, and root colonization of noncereal crop plants to inoculation with Azospirillum brasilense Cd

Abstract

Inoculation of seven different crop plant species by Azospirillum brasilense Cd resulted in an increase in plant yield, as well as in changes in several other plant parameters, in tomato, eggplant, pepper, and cotton plants. Analysis of 56 different experiments revealed that the rate of success (positive plant response) ranged from 71 to 75 %. The dry weight of plants and yield responses ranged from significantly high yield increases to negligible or no response in similarly performed experiments. The average increases in yield in the positive response experiments were 30, 23, 18, and 16% for tomato, eggplant, pepper, and cotton, respectively. Significant earlier maturation was also detected in the four responding plant species. The response of other plant growth parameters varied between plant species. The level of root colonization by A. brasilense Cd was similar in all four plant species, i.e. root population size of 5 × 105 cfu/g fresh weight root. It is suggested that inoculation of noncereal crop plants by the cereal-root originate A. brasilense Cd is nonspecific with inconsistency in plant response to inoculation.