Phosphorus Efficiency Mechanisms of Two Wheat Cultivars as Affected by a Range of Phosphorus Levels in the Field

Abstract

Phosphorus (P) efficiency includes both P acquisition efficiency (PAE) and internal P utilization efficiency (PUE). Despite substantial research, genotypic variation in PAE and PUE remains incompletely understood in the field. A 2-year field study was conducted to compare PAE and PUE and related morphological, physiological, and molecular root traits of two winter wheat cultivars (Triticum aestivum L. cv. SJZ8 and KN92) in response to six P application rates in a P-deficient calcareous soil. Both cultivars showed similar growth and yield potential at each P supply level, reaching optimal growth at the same P application rate of about 100 kg P ha-1. However, the two cultivars differed in how they achieved yield and P efficiency. As P supply increased for both cultivars, root dry weight (RDW), root length density, and expression of the phosphate transporter gene TaPHT1.2 in roots initially increased and then stabilized, but arbuscular mycorrhizal fungal colonization, rhizosphere acid phosphatase activity, expressions of the P-starvation marker gene TaIPS1.1 and the purple acid phosphatase gene TaPAP16 in roots initially decreased and then stabilized. To enhance P acquisition when the P supply was deficient, KN92 modified the morphology of its roots, while SJZ8 increased the physiological activities in its roots. With an adequate P supply, high expression of TaPHT1.2 in roots might account for efficient P uptake for both cultivars, especially for KN92. Although P uptake per RDW was similar for both cultivars at anthesis, PAE was higher for KN92 than SJZ8 in terms of total P uptake in aboveground parts, whereas shoot and grain PUE were higher in SJZ8 than in KN92, mainly during the reproductive growth stage. These results indicate that P efficiency is under genotypic control at all P supply levels tested in both wheat cultivars, and that the two cultivars depend on different root strategies for P acquisition and utilization in response to changes in the P supply.

Root developmental responses to phosphorus nutrition

“…The discrepancies among the three reports discussed in this paragraph (Sun and Zhang, 2000; Teng et al, 2013; Shen et al 2018) might be due to the differences in the growth medium (hydroponics vs. soil), levels of P applied, growth conditions (glasshouse vs. field, temperature, humidity, and planting density), harvest time, and genotypes. With respect to genotype, Deng et al (2018) found that two wheat cultivars responded to P deficiency quite differently in a 2‐year field experiment. Although both cultivars showed similar growth and yield potential at each P supply level and attained optimal growth at the same P application rate, they differed in how they achieved yield and P efficiency.…”

“…As described above, the root developmental responses of a given crop species reported by different research groups are not consistent. Apparently, there is significant genotypic variations within the same crop species: see Hajabbasi and Schumacher (1994), Gaume et al (2001), andLiu et al (2018) for maize; Li et al (2001), Shimizu et al (2004), andVejchasarn et al (2016) for rice; and Deng et al (2018) for wheat. The use of different genotypes may help explain why different research groups have reported inconsistent or even contradictory results regarding the root developmental response of the same crop to P deficiency.…”

Population structure and genome-wide association studies in bread wheat for phosphorus efficiency traits using 35 K Wheat Breeder’s Affymetrix array

“…At a molecular level, several Pi starvation-induced (PSI) genes and gene products provide tolerance to plants to cope with the P stress condition as shown by transcriptomic, proteomic and metabolomic studies 9 – 11 . Further, genotypic differences in P stress tolerance have been reported in many crops, for example, in soybean 7 , maize 11 , wheat 12 and rice 13 . To improve P use efficiency (PUE) through genetic approaches, identification of a few quantitative trait loci (QTLs) have been reported which are mainly based on the shoot P concentration and biomass production 14 – 16 .…”

Too much fertilizer? An observational association between inputs at planting and crop yield on a Saskatchewan farming operation

“…Phosphate fertilization can also increase yield, although there is concern that application made at planting may be underutilized (Grant et al 2002). For some wheat cultivars, excess residual phosphorus has been associated with decreased grain yield (Deng et al 2018). Potassium is associated with grain quality and yield (Mohr et al 2004).…”