Effect of plant growth promoting rhizobacteria (PGPR) on leaf area duration (LAD) dynamics of rice (Oryza sativa L.) plants under nitrogen and water limited conditions

The aim of the present research was to evaluate the effect of Azospirillum and Pseudomonas coinoculation on leaf area index and duration dynamics in an improved rice cultivar (Keshvari) which is commonly grown under northern Iran conditions. The experimental plots were arranged in a split-split plot in a randomized complete block design replicated three times. The three irrigation regimes (control, no irrigation at either panicle initiation or flowering stages) and nitrogen fertilizers (control or recommended dose as the rate of 100 kg/ha nitrogen, 50 and 25% of recommended dose) were assigned to the main-plots and sub-plots, respectively, and the four PGPR treatments [control, Azospirillum brasilense (AZP), Pseudomonas fluorescence (PSD) and AZP+PSD] were arranged in the sub-sub plots. Results of LAD showed that during the 35 to 110 days after transplanting period, AZP+PSD inoculated rice plants had higher LAD as compared to the non-inoculated plants. LAD at different growth stages, however, varied strongly among water deficit plots and control. Rice plants not irrigated at flowering stage had fewer LADs as compared to other treatments. Results of the present experiment demonstrated that dual inoculation of A. brasilense and P. fluorescence rhizobacteria in lowland rice cultivation might enable to improve the leaf area index (LAI) and hence improve leaf area duration (LAD) under low irrigation and nitrogen conditions.