Suiqi Zhang

Moderate Drought Stress Affected Root Growth and Grain Yield in Old, Modern and Newly Released Cultivars of Winter Wheat

To determine root growth and grain yield of winter wheat (Triticum aestivum L) under moderate drought stress, a nursery experiment and a field trial were conducted with or without water stress using three representative cultivars released in different years: CW134 (old landrace), CH58 (modern cultivar) and CH1 (new release). In the nursery experiment, plants were grown in soil-filled rhizoboxes under moderate drought (MD, 55% of field capacity) or well-watered (WW, 85% of field capacity) conditions. In the field trial, plots were either rainfed (moderate drought stress) or irrigated with 30 mm of water at each of stem elongation, booting and anthesis stages (irrigated). Compared to drought stress, grain yields increased under sufficient water supply in all cultivars, particular the newly released cultivar CH1 with 70% increase in the nursery and 23% in the field. When well-watered (nursery) or irrigated (field), CH1 had the highest grain yields compared to the other two cultivars, but produced similar yield to the modern cultivar (CH58) under water-stressed (nursery) or rainfed (field) conditions. When exposed to drought stress, CW134 had the highest topsoil root dry mass in topsoil but lowest in subsoil among the cultivars at stem elongation, anthesis, and maturity, respectively; while CH1 had the lowest topsoil and highest subsoil root dry mass at respective sampling times. Topsoil root mass and root length density were negatively correlated with grain yield for the two water treatments in nursery experiment. When water was limited, subsoil root mass was positively correlated with thousand kernel weight (TKW). In the field trial, CH1 and CH58 used less water during vegetative growth than CW134, but after anthesis stage, CH1 used more water than the other two cultivars, especially in the soil profile below 100 cm, which was associated with the increased TKW. This study demonstrated that greater root mass and root length density in subsoil layers, with enhanced access to subsoil water after anthesis, contribute to high grain yield when soil water is scarce.

Biomass partition, leaf gas exchange and water relations of alfalfa and milkvetch seedlings in response to soil drying

This study compared physiological and growth responses to water stress of two legume species during the seedling stage. Potted alfalfa (Medicago sativa L. cv. Algonquin) and milkvetch (Astragalus adsurgens Pall. cv. Pengyang earlymaturing vetch) seedlings were grown under well-watered [soil water content (SWC) maintained at 14.92% daily] or water-stressed conditions (drying) for 15 days. Net photosynthetic rate (PN), transpiration rate (E) and stomatal conductance (gs) of both species decreased parabolically. When SWC decreased to 7.2% and 10.3%, gs values for alfalfa and milkvetch were significantly different from those of the respective well-watered plants (p<0.05). When SWC decreased to 6.6% for alfalfa and 6.8% for milkvetch, leaf water potentials (ψL) were significantly different from those of the well-watered plants (p<0.05). Thus the difference between the SWC thresholds for a nonhydraulic root signal (nHRS) and a hydraulic root signal (HRS) were 0.6% and 3.5% for alfalfa and milkvetch, respectively. Milkvetch had a lower gs than alfalfa for a given SWC (p<0.05). Although alfalfa seedlings had a higher dry mass (DM) and root:shoot ratio (R/S) than milkvetch in both treatments (p<0.05), we concluded that milkvetch seedlings had greater drought tolerance than alfalfa.

Photosynthetic response of tetraploid and hexaploid wheat to water stress

Photosynthetic characteristics of ear and flag leaves of wheat species, tetraploid Triticum dicoccoides Kom and hexaploid Bima1, were studied in plants grown under well-watered (WW) and water-stressed (WS) conditions. Compared to ears, flag leaves exhibited higher photosynthetic rate (PN) at the filling stage, but more severe decrease under WS. PN in the tetraploid wheat ear remained higher than that in the hexaploid wheat during the grain-filling stage. Water stress decreased PN in both the organs; this decline was caused by a reduction in Rubisco activity, not by drought-induced stomatal limitation. Tetraploid wheat ears exhibited higher relative water content and water-use efficiency than that of hexaploid wheat, under WS. The change in phosphoenolpyruvate carboxylase activity and carbon isotope composition indicated the absence of C4 metabolism in the ears of both species under both conditions. The improved performance of the tetraploid wheat ears under WS was associated with better water relations.

Dissecting root trait variability in maize genotypes using the semi-hydroponic phenotyping platform

Background and aimsThe production of maize (Zea mays L.) is restricted by various edaphic stresses, including drought and low-fertility soil. Searching for genotypes with optimal root traits is a promising practice when breeding for improved adaptation to abiotic stress and resource-use efficiency.MethodsUsing an established semi-hydroponic phenotyping technique, we assessed root trait variability across 174 maize genotypes including 113 cultivars and 11 breeding lines from northern China and 50 Serbian hybrids.ResultsLarge variation in root architecture traits was observed among the tested genotypes 28xa0days after transplanting. Sixteen of the characterized traits had coefficients of variation greater than 0.25, especially local root traits. Root traits including total root length, root length at various depths, total shoot mass and nodal root angle, should be considered in maize breeding programs. Genotype ranking data based on a composite score was used to assist in the selection of genotypes with contrasting root architecture traits for future studies.ConclusionThis study identified genotypic variation in root architecture traits in a diverse genotypes of maize. The outcomes of this study could form a basis for maize breeding programs aimed at producing maize cultivars for improved adaptation to target environments.

Wheat cultivars at different decades vary widely in grain-filling characteristics in Shaanxi Province, China

Eight cultivars of dry-land wheat (Triticum aestivum L.) historically planted in Shaanxi Province, China, were grown in plots with irrigation and drought treatments during the growing seasons of 2011–2014, so as to characterize the differences in the rate and duration of the grain-filling stage among cultivars. The experimental results showed no obvious change among cultivars with respect to the duration of the grain-filling stage and no significant correlation between duration and grain weight. The filling rates of all three phases (lag, linear, and mature periods) showed significant differences among cultivars and had a greater effect on the grain weight than the duration of the filling stage, even though drought decreased the filling rate in the linear and mature periods. A lower filling rate led to a lighter grain weight in inferior grains than in superior grains. For the superior and inferior grains in the central spikelets, modern cultivars possess faster filling rates, especially in the lag and linear periods, whereas for the whole spike, no significant trend with cultivar replacement was observed. Faster filling rates with stable filling durations will be beneficial in obtaining additional yield increases.

Yield and water use efficiency of dryland potato in response to plastic film mulching on the Loess Plateau

ABSTRACT Water shortage is a key factor limiting potato yield in dryland farming regions, and the practice of soil mulching with plastic film has proven to be effective for increasing crop yield and improving soil and water conservation. This study investigated the effects of plastic mulching on potato yield and water use efficiency (WUE) on the Loess Plateau of China based on a synthesis of 44 publications (1987–2016) from 17 sites. Our results indicated that relative to no mulching, plastic mulching significantly increased the yield and WUE by 29.2% and 31.7%, respectively. The effects on yield under different mulching methods were ranked as follows: ridge-furrow mulching (RFM) > flat mulching (FM), and the effects on yield with different mulching extents were ranked full-area mulching (FAM) > partial-area mulching (PAM). The effects of plastic mulching on the yield using different colors of film were ranked as white plastic mulching (WPM) > black plastic mulching (BPM) and under different rainfall levels as (precipitation < 400u2005mm) > (precipitation > 400u2005mm). The rankings of the effects of plastic mulching on WUE were the same as for potato yield. The yield-evapotranspiration (ET) relationship could be described using a quadratic polynomial, and the yield response curve to ET under plastic mulching fell above the no-mulching curve, indicating that plastic mulching can result in higher yields than no mulching when ET is equal. The yield-ET relationship indicated that potatoes required an ET of 334 and 360u2005mm to achieve the highest yield under plastic mulching and no mulching, respectively, and potato WUE increased linearly with yield under both plastic mulching and no mulching. This study indicated that RFM, FAM and WPM are better potato management measures and that there is potential to improve the yield and WUE on the Loess Plateau.