Boron Nutrition and Microbial Allelopathy for Improving the Productivity and Grain Biofortification of Bread Wheat

Abstract

Studies on boron (B) nutrition and microbial allelopathy for improving the productivity and grain biofortification of bread wheat were conducted in Allelopathy laboratory, glasshouse and Agronomic Research Area, Department of Agronomy, University of Agriculture, Faisalabad, Pakistan. In the lab and glasshouse studies, rates and sources of B for seed priming and coating were optimized using two wheat cvs. Faisalabad-2008 and Lasani-2008. In all four methods of B application, application of B improved yield as well as grain B concentration. Application of B as seed priming, coating, soil and foliar application at 0.01 M B solution (as borax), 0.25 g B (as borax) kg-1 seed, 1.0 kg B ha-1 and 0.01 M B solution, respectively were the best among the tested treatments. In experiment I, conducted under field conditions, wheat genotypes were characterized for B biofortification potential. Experiment was conducted in randomized complete block design in factorial arrangement during 2012-2013 and 2013-2014. Boron was soil applied at 1.0 kg B ha-1. Wheat genotypes Chenab-2000, Uqaab-2000, Pasban-90 and MH-97 had more grain B contents than rest of the genotypes during both years. In experiment II, conducted under field as well as glasshouse conditions, application of B and plant growth promoting rhizobacteria (PGPR) were investigated for potential effect on wheat producticity and enhancement in grain B concentration. Experimental treatments comprised of pre-otimized level of B from each application methods as well as application of PGPR i.e. (1) hydropriming (control), (2) seed priming with 0.01 M B solution, (3) seed coating with 0.25 g B kg-1 seed, (4) soil application with 1.00 kg B ha-1, (5) foliar application with 0.01 M B solution, (6) seed priming with 0.01 M B solution + Bacillus, (7) seed coating with 0.25 g B kg-1 seed + Bacillus, (8) soil application with 1.00 kg B ha-1 + Bacillus, and (9) foliar application with 0.01 M B solution + Bacillus. Seed priming with B reduced time to 50% emergence and mean emergence time. Crop growth rate, leaf growth rate, plant height, tillers per plant, leaf chlorophyll contents and plant water relation were also improved by the application of B. However, there was no effect of application of PGPR on these parameters. Nonetheless, application of PGPR also triggered the release of organic acid from plant roots of both cultivars, which improved the soil nutrient contents (nitrogen, phosphorous, potassium and B). While application of B and PGPR enhanced the yield and related traits of wheat cultivars. However, maximum yield was recorded with the application of B and PGPR as seed coating. Grain B concentration was also enhanced by PGPR while maximum grain B concentration was recorded in seed priming. Application of B and PGPR as seed coating was the most economical and cost-effective option as indicated by more cost to benefit ratio and marginal rate of return. In conclusion, although application of B improved the wheat performance whereas application of PGPR further improved to the beneficial affects of B nutrition. However, seed coating with combination of B and PGPR was the best treatment option, hence seeds of wheat may be coated with B and PGPR to improve the performance, yield, grain biofortification and net economic returns of wheat.