Effect of plant growth promoting rhizobacteria (PGPR) on phenology of late maturity maize (Zea mays L.) hybrids

To study the effect of application of plant growth promoting rhizobacteria (PGPR) including; Azotobacter chroococcum, Azospirillum lipoferum, Azospirillum brasilense and Pseudomonas fluorescens on phenology and grain yield of late maturity maize (Zea mays L.) hybrids (KSC700, KSC704 and a promising single cross, B73×K18), a field experiment was conducted in two successive cropping seasons. Exprimental treatments including seeds of maize hybrids inoculated with single (one by one bacteria) and co-inoculated by two and three bacterial combined inoculants and no inoculation as control. Duration from planting to seedling, fourth, eighth and tvelveth leaf, tassel,ing pollen and silk emergence, pollen shedding termination, silk desiccation and grain physiologic maturity as well as vegetative growth period, pollination, silking, coincidence of flowering and grain filling periods were detrmined using Growing Degree Days (GDDs). Grain yield per hectare was also determined. Results revealed that PGPRs affected phenology of maize hybrids as leaf, tassel, pollen and silk emergence was accelerated and duration of pollination, silking, coincidence of flowering and grain filling period was prolonged. Corrolation coefficients analysis revealed that GDD for developmental periods and phonological events were positively correlated. It was also revealed that application of inoculantion with combination of all bacteria inoculats had the highest promoting effect on phenology of maize hybrids,. Co-inoculation of seeds by Azotobacter chroococcum and Pseudomonas fluorescens and inoculation of seed by each of them had also high promoting effect, respectively. Maize hybrids had differed in their phonological response to application of PGPR and KSC704 responded more vigorously than other hybrids, followed by B73×K18 and KSC700, respectively. The highest grain yield obtained from KSC700 co-inoculated with all bacteria.