Abstract
The use of beneficial microorganisms in forage grasses is a potentially advantageous technique for a more sustainable pasture management by decreasing the need for chemical fertilization. Our aims were to determine the best method of microorganism inoculation on Brachiaria (Syn. Urochloa) brizantha cv. BRS Piata, compare the responses of inoculated plants of this forage grass with fertilized and unfertilized controls and examine its effect on some morphological, physiological and biochemical responses. On the first experiment, three inoculation methods were tested: in the seed, seed and soil, and soil, with Pseudomonas fluorescens (BRM-32111) and Burkholderia pyrrocinia (BRM-32113). In the second experiment, fertilized and unfertilized plants were either inoculated with BRM-32111, BRM-32113 and co-inoculated (BRM-32111 + BRM-32113). In a final experiment, B. brizantha was inoculated by soil drenching with BRM-32111, BRM-32113 and co-inoculated (BRM-32111 + BRM-32113), and compared to fertilized- and unfertilized-controls. The inoculation by soil drenching, at seedling stage, was more effective than inoculation only in the seed or both in the seed and by soil drenching. The fertilizer may have suppressed the beneficial bacterial effects on the growth of B. brizantha. P. fluorescens and B. pyrrocinia co-inoculated increased nitrate, protein, nitrogen concentration, Spad index (chlorophyll content), leaf area, number of tillers, net photosynthesis and total biomass production of B. brizantha plants. Our results point out to a potentially valuable source of practical information in the search of an eco-friendlier approach to increase pasture productivity.
Highlights
Increasing global population coupled with shifting dietary preferences in emerging economies is leading to a substantial increase in the consumption of livestock products, mainly beef
When inoculation was performed by soil drench P. fluorescens (BRM-32111) and B. pyrrocinia (BRM-32113) increased biomass production (F1,36 = 1989,23; P < 0.01) by 242% and 112%, respectively (Table 1)
No increase in biomass production could be observed when microorganisms were inoculated on fertilized plants (Table 2)
Summary
Increasing global population coupled with shifting dietary preferences in emerging economies is leading to a substantial increase in the consumption of livestock products, mainly beef. Plant growth-promoting microorganisms are beneficial endophytic or rhizospheric microorganisms, able to colonize roots and directly promote growth by regulating the pathway of plant hormones, increasing the biosynthesis of auxin, cytokinin, gibberellin, or minimizing the ACC synthesis, the ethylene precursor, delaying plant senescence [6] [7]. Another beneficial mechanism of growth-promoting microorganisms is to increase the availability of essential nutrients for plant growth, such as nitrogen and phosphorus, and to promote induced resistance of plant defenses against diseases, pests, and abiotic stressors [6] [7]. Growth promotion, resulting from the association of beneficial microorganisms, has been reported in wheat plants [8], forage grass [5], maize [9] and Sorghum bicolor [10]
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