Rhizosphere properties of maize genotypes with contrasting phosphorus efficiency

Abstract

SUMMARYAn experiment was conducted in a growth chamber to evaluate characteristics of the rhizosphere of maize genotypes contrasting in P-use efficiency, by determining length and density of root hairs, the rhizosphere pH and the functional diversity of rhizosphere bacteria. A sample of a Red Oxisol was limed and fertilized with N, K and micronutrients. In the treatment with the highest P level, 174 mg kg -1 P was added. Each experimental unit corresponded to a PVC rhizobox filled with 2.2 dm -3 soil. The experiment was completely randomized with three replications in a 5 x 2 factorial design, corresponding to five genotypes (H1, H2 and H3 = P-efficient hybrids, H4 and H5 = P-inefficient hybrids) and two P levels (low = 3 mg dm -3 , high = 29 mg dm -3 ). It was found that 18 days after transplanting, the nodal roots of the hybrids H3 and H2 had the longest root hairs. In general, the pH in the rhizosphere of the different genotypes was higher than in non-rhizosphere soil, irrespective of the P level. The pH was higher in the rhizosphere of lateral than of nodal roots. At low P levels, the pH variation of the hybrids H2, H4 and H5 was greater in rhizospheric than in non-rhizospheric soil. The functional microbial activity in the rhizosphere of the hybrids H3 and H5 was highest. At low soil P levels, the indices of microbial functional diversity were also higher. The microbial metabolic profile in the rhizosphere of hybrids H1, H2, H3, and H5 remained unaltered when the plants were grown at low P. The variations in the rhizosphere properties could not be related to patterns of P-use efficiency in the tested genotypes.Index terms: P-acquisition, mechanisms, rizobox.

Response of contrasting bread wheat genotypes for heat and drought stress tolerance for rhizospheric soil properties

“…The rhizosphere is intriguingly complex and dynamic (Philippot et al, 2013), and changes in it are continually renewed by root growth and exudates from the roots (Brasil et al, 2011). A good understanding of the processes undergoing in it, is vital for maintaining soil health and sustained crop production (Morrissey et al, 2004).…”

“…Abiotic factors, specially drought affects the concentration and accumulation patterns of Ca, Fe, Mg, Mo and S in the plants and soil (Sardans et al, 2008). Similarly, the microbial community structure of rhizosphere is affected by the genotypes, soil types, field management practices and developmental stage of the plant (Brasil et al, 2011;Philippot et al, 2013;Qiao et al, 2017;Berlanas et al, 2019). There are also some contradiction to this, and in one such study, the contrasting maize genotypes for P-use efficiency did not show variation in their rhizosphere properties (Brasil et al, 2011), while in another study with cotton cultivars, the community structure of the rhizosphere bacteria was found to be affected by the developmental stages of the plant (Qiao et al, 2017).…”