Zinc Nutrition and Microbial Allelopathy for Improving the Productivity, Grain Biofortification and Tolerance against Abiotic Stresses in Chickpea

Abstract

Zinc (Zn) deficiency in sandy soils is one of the major reasons of low chickpea yield in Pakistan. Soil Zn deficiency is often associated with human Zn deficiency due to low Zn concentration in the edible plant parts. For this, a series of experiments were conducted to: (i) optimize the Zn application through seed treatment in desi and kabuli chickpea, (ii) charectrize desi and kabuli chickpea genotypes for genetic diversity and grain Zn bioavailability, (iii) evluate the role of plant growth promoting bacteria (PGPB, Enterobacter sp. MN17) in combination with Zn application in improving the productivity and grain biofortification of desi and kabuli chickpea, (iv) study the mechansim of Zn induced tolerance against heat and drought stresses in desi and kabuli chickpea. For optimization, Zn was applied through seed priming and seed coating. Among seed treatments, seed priming with 0.001 M Zn and seed coating with 5 mg Zn kg-1 seed significantly improved stand establishment and early seedling growth of both chickpea types. Zinc application, through either method, improved the stand establishment, grain yield, and grain biofortification. The use of PGPB together with Zn application was more effective in improving the stand establishment, grain yield and grain Zn biofortification. The response of chickpea types differed in Zn and Zn+ PGPB application. In kabuli chickpea, Zn application is more effective through seed coating + Enterobacter sp. MN17, while in desi, Zn application through soil application + Enterobacter sp. MN17 was the best in improving the productivity, profitability, bioavailable Zn and grain quality. The results of genetic diversity revealed low to moderate genetic diversity (0.1488 for desi and 0.1041 for kabuli) among the tested chickpea genotypes (n = 16) of Pakistani origin. However, there was significant variation for yield and grain quality. The highest grain yield, grain Zn concentration and bioavailable Zn was recorded in desi genotype NIAB-CH-2016 and in kabuli genotype Noor-2013. Abiotic stresses suppressed the growth of chickpea, and under Zn deficiency the suppressive impacts were more severe. However, adequate supply of Zn (1 µM) improved the tolerance against the drought stress (35% water holding capacity) and heat (35/30°Cday/night) stresses in chickpea owing to the improvement in the activities of enzymatic antioxidants, photosynthesis, and accumulation of free leaf proline. In conclusion, Zn fertilization and Zn + PGPB improved the stand establishment, productivity and grain biofortification of chickpea. The chickpea genotypes of Pakistani origin had low to moderate genetic diversity for grain yield and bioavailable Zn. Adequate supply of Zn improves the chickpea growth and performance under abiotic stresses.