Effects of PGPR Formulations, Chemical Fertilizers, and Their Combinations on Physiological Traits and Quality of Bracts of Poinsettia

This study was carried out to determine the effects of different PGPR formulations, chemical fertilizers, and their combinations on some color characteristics and nutrient content of bract leaf of two cultivars of Euphorbia pulcherrima Willd. ex Klotzsch in a research greenhouse between July 2015 and July 2017. The treatments included bacterial formulations: (1) BI: Paenibacillus polymyxa TV-12E+Pseudomonas putida TV-42A+Pantoea agglomerans RK-79, (2) BII: Bacillus megaterium TV-91C+Pantoea agglomerans RK-92+Bacillus subtilis TV-17C, (3) BIII: Bacillus megaterium TV-91C+Pantoea agglomerans RK-92+Kluyvera cryocrescens TV-113C, and (4) BIV: Bacillus megaterium TV-91C+Pantoea agglomerans RK-79+Bacillus megaterium TV-6D). Also, fertilizer treatments included the full amount of commonly used Chemical Fertilizer (CF= 150 g 100 L-1) and combination of the reduced amount of chemical fertilizer by 50% with each bacterial formulation, and control. The first red leaves, life of bracts, color properties (L, a* and b*), content of anthocyanin, chlorophyll content in green leaf, macro and micronutrient contents of bracts were evaluated in the experiment. CF and BII+50%CF applications encouraged the coloring of bract leaves early (4.01%). It was determined that CF (7.76%), BI+50%CF (6.03%) and BII+50%CF (5.27%) applications significantly increased chlorophyll content of poinsettia bract when compared to the control. Darker colored bracts were obtained from BI and BIV applications compared to the control. The highest total nitrogen amount (3.69%), soluble phosphorus (4,285.33 mg kg-1), potassium (28,132.45 mg kg-1) and calcium (8,299.03 mg kg-1) amount were found in the BII+50%CF application. It was determined that bacterial formulations BI, BIV, BIV+50%CF and BII+50%CF had positive effects on some plant aesthetic, quality characteristics, and nutrient content of bract of poinsettia and can be used in poinsettia production stage as one of the biological products. Thus, bacterial formulations may replace or reduce use of chemical fertilizers in poinsettia production.