Floral and foliar application of Plant Growth Promoting Rhizobacteria (PGPR) to apples increases yield, growth, and nutrient element contents of leaves

During 2003 and 2005, plant growth promoting effects of Pseudomonas BA-8 and Bacillus OSU-142 were tested alone or in combination on apple (Malus domestica L.) cvs. 'Starkrimson' and 'Granny Smith' in terms of yield, growth, and nutrient composition of leaves in the province of Karaman, Turkey. The presence of Pseudomonas BA-8, Bacillus OSU-142 and BA-8+OSU-142 stimulated plant growth and resulted in significant yield increases in both cultivars. Floral and foliar applications of PGPR strains significantly increased yield per trunk cross-section area (13.3-118.5%), fruit weight (4.2-7.5%), shoot length (20.8-30.1%), and shoot diameter (9.0-19.8%) in 'Starkrimson' and yield per Trunk Cross Sectional Area (TCSA; 14.9%) and fruit weight (6.5-8.7%) in 'Granny Smith' compared with the control. In addition, all nutrient elements' contents (N, P, K, Mg, Ca, Fe, Mn, and Zn) investigated in both cultivars, except Mg in 'Starkrimson', were significantly affected by bacterial applications when compared with the control. The highest N content was obtained from BA-8+OSU-142 application in cvs. 'Starkrimson' (2.29%) and 'Granny Smith' (2.33%). Phosphorus contents of leaves of 'Starkrimson' and 'Granny Smith' increased from 0.21 and 0.20% in the control to 0.26 and 0.24% by BA-8 application, to 0.28 and 0.24% by OSU-142 application and to 0.25 and 0.26% by BA-8+ OSU-142 application, respectively. BA-8 application in 'Starkrimson' (1.90%) and OSU-142 applications in 'Granny Smith' (2.90%) significantly increased Ca content of leaves. The results of this study suggest that Pseudomonas BA-8 and Bacillus OSU-142 alone or in combination have the potential to increase the yield, growth, and nutrition of apple trees. © Copyright (c) by The Haworth Press, Inc. All rights reserved.