EFFECTS OF SOME PLANT GROWTH PROMOTING RHIZOBACTERIA (PGPR) STRAINS ON PLANT GROWTH AND LEAF NUTRIENT CONTENT OF APPLE

This investigation was conducted to evaluate the effects of four strains of plant growth promoting rhizobacteria (Agrobacterium rubi A-18, Bacillus subtilis OSU-142, Burkholderia gladioli OSU-7 and Pseudomonas putida BA-8) on growth and leaf nutrient content of ‘Starking Delicious’, ‘Granny Smith’, ‘Starkrimson Delicious’, ‘Starkspur Golden Delicious ’ and ‘Golden Delicious ’ apple cultivars grafted on semi-dwarf rootstock MM-106. The applications of bacterial strains increased the leaf number and area as well as number of annual shoots and their diameter, although OSU-7 application suppressed annual shoot length. BA-8 application resulted in the highest annual shoot number (52.4) and OSU-142 in the largest leaf area (16.12 cm2). The applications of A-18 bacteria decreased the concentration of N, K and Cu and increased the concentration of P and Zn in the leaves. OSU-142 application resulted in the highest Mg (0.13%) and Fe (32.7 ppm) contents and OSU-7 in the highest Mn content (40.3 ppm). None of the applications affected the concentration of Na and Ca in the leaves