Role of Plant Growth Promoting Rhizobacteria and chemical fertilizers on plant growth, oil content and quality of Safflower and Canola and their potential for biodiesel production

Abstract

Experiments were conducted to evaluate the role of plant growth promoting rhizobacteria (PGPR) alone and supplemented with chemical fertilizers to improve quantity and quality of safflower (Carthamus tinctorius L.) and canola (Brassica napus L.) with perspective to biodiesel production. First experiment of the series was conducted to evaluate the effect of PGPR viz. Azospirillum brasilense and Azotobacter vinelandii and chemical fertilizers (Urea and DAP) alone and in combination (under axenic conditions) on enzymes activities of rhizospheric soil in addition to general impact on growth of safflower cvv. Thori and Saif-32. The PGPR were applied as seed inoculation at the rate of 10 6 cells/mL prior to sowing. Chemical fertilizers were applied at full (Urea 60 Kg ha -1 and Diammonium phosphate (DAP) 30 Kg ha -1 ), half (Urea 30 Kg ha -1 and DAP 15 Kg ha -1 ) and quarter doses (Urea 15 Kg ha -1 and DAP 7.5 Kg ha -1 ) during sowing. The colony forming units (cfu) of Azospirillum and Azotobacter were higher in the presence of quarter dose of chemical fertilizers. Activities of soil enzymes viz. urease and phosphatase were enhanced by Azotobacter in combination with quarter doses of chemical fertilizers and Azospirillum in combination with half dose of chemical fertilizers respectively whereas; root proliferation was enhanced by Azotobacter and Azospirillum supplemented with half and quarter doses of chemical fertilizers. The 2 nd experiment was focused on the effect of PGPR and chemical fertilizers under field conditions on plant growth, seed yield, oil contents and quality of safflower with perspective to biodiesel production. The indole acetic acid, gibberellic acid, oil contents, oil/protein ratio and seed phenolics were improved by Azospirillum with half dose of chemical fertilizers. Azospirillum in combination with quarter dose of chemical fertilizers improved the fatty acid profile, oil quality and amino acids contents with parallel increase in biodiesel yield whereas; Azotobacter in combination with quarter dose of chemical fertilizers improved seed crude protein and induced protein of 130 KDa and 100 KDa. Seed nutrients viz. Ca +2 , K + were increased by Azotobacter and Azospirillum supplemented with half dose of chemical fertilizers. In the 3 rd experiment effects of chemical fertilizers, Azospirillum and Azotobacter were studied on plant growth, seed yield and oil quality of canola (Brassica napus L.) var. Pakola pertaining to biodiesel production. Significant improvements in seed yield ixand seed size were recorded in chemical fertilizer treatment while oleic acid (C18:1) was improved by Azospirillum treatment with parallel decrease in erucic acid contents. Azotobacter showed maximum increase in seed oil content with concomitant decrease in seed glucosinolate and moisture content. Chemical fertilizers and Azospirillum decreased the oil acid value and free fatty acid (%FFAs) contents with concomitant increase in seed protein and biodiesel yield (93 % and 92% respectively). Protocol for the production of safflower biodiesel was optimized using 1 H NMR, FT- IR, GC-MS and refractometer techniques. The biodiesel samples prepared by base catalyzed transesterification reaction showed maximum yield (97.84%) at 0.5% catalyst concentration with 6:1 methanol/oil ratio at 65°C as quantified by 1 H NMR technique with minimum (1.41) refractive index and improved physico-chemical properties. The GC/MS analysis showed the presence of five major faty acid methyl esters. Improvement in separation and quantification of fatty acid methyl esters in safflower oil was achieved using comprehensive two-dimensional GC (GC×GC). The GC×GC separation accomplished by the combination of SLB-IL111 with IL59 column phases provided excellent separation of FAME standard mixture and also safflower FAMEs were well separated and quantified in a short run of 16 min. It is inferred that PGPR can supplement the chemical fertilizers upto 50%–75% in order to obtain optimum growth and yield of safflower and use of advanced technologies improved biodiesel and fatty acid analyses being more rapid, precise and cost effective.