Barley genotypes with long root hairs sustain high grain yields in low-P field

Superior root traits, like long root hairs, enhance phosphorus (P) uptake and hence the selection for root hair trait offers the possibility to sustain yields in low-P soils. It is yet unknown whether root hair promoted P uptake of barley genotypes is related to the grain yield in low -P field soil. To investigate this, a set of barley genotypes was pre-screened using hydroponics for long (about 1 mm, cvs. Pongo, Linus Barke, Tofta, Henni) and short root hairs (about 0.5 mm, cvs. AC91/5606/17, Meltan, Scarlett, Century, Otira, and Cecilia). The selected genotypes were cultivated in low-P field plots (no P in 35 years, 3 µM P in soil solution) and in plots amended by moderate (10 kg P ha⁻¹, 6 µM P in soil solution) and high (20 kg P ha⁻¹, 10 µM P in soil solution) P fertilisation. The ranking of the genotypes root hairs in laboratory remained consistence in the field, except for cv. Barke (1.05 mm). The genotypes varied in specific root length (SRL, mg⁻¹) and root hair length (RHL), but the estimated volume of soil explored by root system clearly depended on RHL. The correlations of RHL (R² = 0.60***), volume of soil explored by root system (R² = 0.57***) and SRL (R² = 0.40**) with the P uptake in the field were highly significant. The correlation of root-shoot ratio with the P uptake was non-significant (R² = 0.11). The genotypes with long root hairs preserved economical stable grain yield in low, moderate and high P plots. In contrast, the genotypes with short root hairs produced lower grain yield in low P soil, but they responded to moderate and high P fertilisation by significant increase in their grain yields. From the results of this field-based case study, it is concluded that barley genotypes with long root hairs are better adapted in low P soils and they express high yield potentials both in low and high P soils.