An Assessment of Application Methods of Plant Growth Promoting Rhizobacteria (PGRRs) for Their Growth Promoting Attributes in Sugarcane (Saccharum spp. hybrid)

Abstract

Extensive literature has documented the impact of plant growth promoting rhizobacteria (PGPR) on various crops but stud- ies are scant on PGPR application methods. In this study, we tested three different application methods, viz., biopriming,

foliar and rhizospheric application on the growth of two sugarcane lines (CPSG-2525 and CPSG-2730). Pseudomonas

aurantiaca (PB-St2) and Bacillus spp. strains (SB-1 and CRN8) were selected and their synergistic interaction was evalu- ated by competitive growth assay. Subsequently, sugarcane plants were inoculated with PGPRs, either individually or their

consortia in pot experiment. The survival analysis of inoculated strains was carried out at various time intervals, whereas plant’s morpho-chemical data were noted after 90 days of sowing. Biopriming notably enhanced the above-ground sugarcane growth, with maximum shoot length (156.1 cm) with SB-1+CRN8 in CPSG-2525, followed by 146.4 cm in CPSG-2730 with PB-St2, compared with 113.7 and 114.13 cm respectively in control plants. Moreover, a substantial increase in shoot dry matter (11.4 g) was noted with PB-St2 in CPSG-2730 and 12.1 g in CPSG-2525 with PB-St2+CRN8 in contrast to non-inoculated plants (5 g). Rhizospheric application of PB-St2 led to a significant increase in root length (79 cm) and dry weight (2 g) in both sugarcane lines. In terms of biochemical attributes, significantly (p<0.05) higher chlorophyll content (2.98 and 3.78 mg/g), total soluble sugars (7.54 and 5.72 mg/g) and sucrose content (52.21 and 24 mg/g) were observed in biopriming in CPSG-2525 and CPSG-2730, respectively. Our findings suggest that biopriming is more convenient and effective method of applying PGPRs to sugarcane, while Pseudomonas aurantiaca (PB-St2) enhanced sugarcane growth, both individually and in combination with Bacillus results in improved plant growth and biochemical attributes.