Yield determination in winter wheat under different water regimes

Balanced below- and above-ground growth improved yield and water productivity by cultivar renewal for winter wheat

Breeding cultivars that can maintain high production and water productivity (WP) under various growing conditions would be important for mitigating freshwater shortage problems. Experiments were carried out to assess the changes in yield and WP of different cultivars by breeding and traits related to the changes using tubes with 1.05 m depth and 19.2 cm inner diameter buried in the field located in the North China Plain. Six winter wheat cultivars released from the 1970s to 2010s were assessed under three water levels for three seasons. The results indicated that yield was on average improved by 19.9% and WP by 21.5% under the three water levels for the three seasons for the cultivar released in the 2010s as compared with that released in the 1970s. The performance of the six cultivars was relatively stable across the experimental duration. The improvement in yield was mainly attributed to the maintenance of higher photosynthetic capacity during the reproductive growth stage and greater above-ground biomass accumulation. These improvements were larger under wet conditions than that under dry conditions, indicating that the yield potential was increased by cultivar renewal. Traits related to yield and WP improvements included the increased harvest index and reduced root: shoot ratio. New cultivars reduced the redundancy in root proliferation in the topsoil layer, which did not compromise the efficient utilization of soil moisture but reduced the metabolic input in root growth. Balanced above- and below-ground growth resulted in a significant improvement in root efficiency at grain yield level up to 40% from the cultivars released in the 1970s to those recently released. The results from this study indicated that the improved efficiency in both the above- and below-parts played important roles in enhancing crop production and resource use efficiency.

Soybean Crops Penalize Subsequent Wheat Yield During Drought in the North China Plain

Contemporary wisdom suggests that inclusion of legumes into crop rotations benefit subsequent cereal crop yields. To investigate whether this maxim was generically scalable, we contrast summer soybean-winter wheat (SW) with summer maize-winter wheat (MW) rotation systems in an extensive field campaign in the North China Plain (NCP). We identify heretofore unseen interactions between crop rotation, synthetic N fertilizer application, and stored soil water. In the year with typical rainfall, inclusion of soybean within rotation had no effect on wheat ear number and yield, while N fertilization penalized wheat yields by 6-8%, mainly due to lower dry matter accumulation after anthesis. In contrast, in dry years prior crops of soybean reduced the rate and number of effective ears in wheat by 5-27 and 14-17%, respectively, leading to 7-23% reduction in wheat yield. Although N fertilization increased the stem number before anthesis in dry years, there was no corresponding increase in ear number and yield of wheat in such years, indicating compensating reduction in yield components. We also showed that N fertilization increased wheat yield in MW rather than SW as the former better facilitated higher dry matter accumulation after flowering in dry years. Taken together, our results suggest that soybean inclusion reduced soil available water for subsequent wheat growth, causing yield penalty of subsequent wheat under drought conditions. We call for more research into factors influencing crop soil water, including initial state, crop water requirement, and seasonal climate forecasts, when considering legumes into rotation systems. Graphical AbstractResponse of wheat population and yield to soybean inclusion under limited-irrigation.

RNA-seq analysis reveals different drought tolerance mechanisms in two broadly adapted wheat cultivars 'TAM 111' and 'TAM 112'

Wheat cultivars 'TAM 111' and 'TAM 112' have been dominantly grown in the Southern U.S. Great Plains for many years due to their high yield and drought tolerance. To identify the molecular basis and genetic control of drought tolerance in these two landmark cultivars, RNA-seq analysis was conducted to compare gene expression difference in flag leaves under fully irrigated (wet) and water deficient (dry) conditions. A total of 2254 genes showed significantly altered expression patterns under dry and wet conditions in the two cultivars. TAM 111 had 593 and 1532 dry-wet differentially expressed genes (DEGs), and TAM 112 had 777 and 1670 at heading and grain-filling stages, respectively. The two cultivars have 1214 (53.9%) dry-wet DEGs in common, which agreed with their excellent adaption to drought, but 438 and 602 dry-wet DEGs were respectively shown only in TAM 111 and TAM 112 suggested that each has a specific mechanism to cope with drought. Annotations of all 2254 genes showed 1855 have functions related to biosynthesis, stress responses, defense responses, transcription factors and cellular components related to ion or protein transportation and signal transduction. Comparing hierarchical structure of biological processes, molecule functions and cellular components revealed the significant regulation differences between TAM 111 and TAM 112, particularly for genes of phosphorylation and adenyl ribonucleotide binding, and proteins located in nucleus and plasma membrane. TAM 112 showed more active than TAM 111 in response to drought and carried more specific genes with most of them were up-regulated in responses to stresses of water deprivation, heat and oxidative, ABA-induced signal pathway and transcription regulation. In addition, 258 genes encoding predicted uncharacterized proteins and 141 unannotated genes with no similar sequences identified in the databases may represent novel genes related to drought response in TAM 111 or TAM 112. This research thus revealed different drought-tolerance mechanisms in TAM 111 and TAM 112 and identified useful drought tolerance genes for wheat adaption. Data of gene sequence and expression regulation from this study also provided useful information of annotating novel genes associated with drought tolerance in the wheat genome.

Morphophysiological changes of wild Stachys multicaulis species under physical conditions during the cultivation process

Depending on the physical environmental conditions, cultivation process can have significant effects on the wild plants' morphophysiological characteristics. Stachys multicaulis is an Iranian wild endemic medicinal plant species and its cultivation preformed under different Soil Textures (ST) and Soil Moisture Regimes (SMRs). Controlled pot culture conditions performed with light, moderate, heavy STs and a set of SMRs at 100% Field Capacity (FC), 70%FC and 30% FC. Plant cultivated in heavy STs had higher performance in all measured treats. Height of plant (HP), Calibrated Greenness (CG), Leaf Ratio (LR) and Angle (LA), aerial Moisture Content (MC) did not show a regular trend in comparison to the wild. Unlike the Density of Trichome (DT), Length of leave's Trichome (LT) showed a significant change under cultivation conditions (p < 0.01). Also, as a physiological response, Essential Oils Components (EOC), especially thymol and bicyclogermacrene decreased with decreasing soil MC for light ST and the lowest change were observed in heavy ST and 30%FC. Generally, cultivation reduced EOCs, but improved plant's morphological characteristics.