The end-use quality of wheat can be enhanced by optimal water management without incurring yield loss

Abstract

In China, water-saving irrigation is playing important roles in ensuring food security, and improving wheat quality. A barrel experiment was conducted with three winter wheat (Triticum aestivum L.) genotypes and two irrigation pattens to examine the effects of regulated deficit irrigation (RDI) on wheat grain yield, water-use efficiency (WUE), and grain quality. In order to accurately control the soil water content, wheat was planted in the iron barrels set under a rainproof shelter, and the soil water content in the iron barrel was controlled by gravity method. The mechanisms whereby water management influences the end-use functional properties of wheat grain were also investigated. The results revealed that RDI improved the end-use functional properties of wheat and WUE, without significant yield loss (less than 3%). Moderate water deficit (60% to 65% field capacity) before jointing and during the late grain-filling stage combined with a slight water deficit (65% to 70% field capacity) from jointing to booting increased grain quality and WUE. The observed non-significant reduction in wheat yield associated with RDI may be attributed to higher rate of photosynthesis during the early stage of grain development and higher rate of transfer of carbohydrates from vegetative organs to grains during the later stage. By triggering an earlier rapid transfer of nitrogen deposited in vegetative organs, RDI enhances grain nitrogen content, which in turn could enhance dough elasticity, given the positive correlation between grain nitrogen content and dough midline peak value. Our results also indicate that the effects of RDI on grain quality are genotype dependent. Therefore, the grain end-use quality of some specific wheat genotypes may be enhanced without incurring yield loss by an optimal water management.

Keywords: grain growth; grain nitrogen content; regulated deficit irrigation; water deficit; wheat quality.

Figure 1

Photos of the experiment at ripening.

Figure 2

The lower limit of soil water content for water treatments. Red and blue lines indicate high-and low-water treatments, respectively. RWC, relative soil water content, percentage of field water capacity; H, high-water treatments; L, low-water treatments; ZCK, Zadoks-Chang-Konzak wheat developmental scale; T, tillering; J, jointing; HD, heading; KW, watery-ripe kernel; KH, hard kernel.

Figure 3

Correlation diagnosis of grain yield, evapotranspiration, and quality parameters. Blue color represents a positive correlation between the two variables that meet at that cell. Conversely, red color represents a negative correlation. The darker and more saturated the color, the greater is the magnitude of the correlation. GY, grain yield (g/barrel); NGB, number of grains per barrel; ET, evapotranspiration (L/barrel); MPT, midline peak time (minute); GI, gluten index (%); MRS, right of midline peak slope (% torque/minute); GPC, grain protein concentration (%); MPV, midline peak value (% torque); GN, grain nitrogen content (mg/grain); TGW, thousand-grain weight (g).

Figure 4

Dynamics of the grain weight (GW) of different genotypes of winter wheat under different levels of irrigation. Red lines indicate high-water treatment, blue lines indicate low-water treatment, red stars represent high-water treatment observations, and blue circles represent low-water treatment observations. DAA, days after anthesis; XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18.

Figure 5

Parameters of the grain filling of different winter wheat genotypes under different irrigation levels. Error bars indicate the confidence interval of the mean. Rm, maximum rate of grain filling; Km, final grain weight; tm95, duration of grain filling. XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18; H, high-water treatment; L, low-water treatment.

Figure 6

Dynamics of grain nitrogen content (GN) of different winter wheat genotypes under different irrigation levels. Red lines indicate high-water treatment, blue lines indicate low-water treatment, red stars represent high-water treatment observations, and blue circles represent low-water treatment observations. DAA, days after anthesis; XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18.

Figure 7

Parameters of grain nitrogen accumulation of different winter wheat genotypes subjected to different irrigation treatments. Error bars indicate the confidence interval of themean. Rn, maximum rate of grain nitrogen accumulation; Kn, final grain nitrogen weight; tn95, duration of grain nitrogen accumulation. XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18; H, high-water treatment; L, low-water treatment.

Figure 8

Dynamics of grain nitrogen concentration (GNC) of different winter wheat genotypes subjected to two different irrigation treatments. Lines represent values fitted using the “loess” method and the points denote observations. DAA, days after anthesis; H, high-water treatment; L, low-water treatment; XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18.

Figure 9

The dynamics of leaf nitrogen concentration (LNC) and rachis nitrogen concentration (RNC) of different winter wheat genotypes grown under different levels of irrigation. Lines represent values fitted using the “loess” method and the points denote observations. DAA, days after anthesis; H, high-water treatment; L, low-water treatment; XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18.

Figure 10

The dynamics of leaf sucrose concentration (LSC) and rachis sucrose concentration (RSC) in different winter wheat genotypes under different levels of irrigation. Lines represent values fitted using the “loess” method and points denote observations. DAA, days after anthesis; H, high-water treatment; L, low-water treatment; XM26, Xinmai-26; XM49, Xinmai-49; ZM18, Zhoumai-18.