The Effect of the Application of Stimulants on the Photosynthetic Apparatus and the Yield of Winter Wheat

The use of stimulation preparations seems to be a promising means for mitigating the effects of abiotic and biotic stressors. Their significance includes plant organism stimulation and metabolism optimisation, water regime, and nutrition during periods of stress. They help bridge it over and create conditions for rapid regeneration. In a field experiment, the effect of the application of stimulation preparations on cultivars Triticum aestivum L. with different genetic composition was evaluated (donor of blue aleurone colour KM-72-18; donor of a multi-row spike (MRS) KM-94-18). Our results show a predominantly positive effect of the application of stimulants on the yield and thousand-grain weight (TKW). The results obtained were influenced by the year, based on different temperatures and precipitation. Higher yields were achieved in 2020 with higher total precipitation during the grain filling period and with a higher maximum quantum yield of the photosystem II (Fv/Fm). In 2019, this period was significantly dry and warm, which was reflected in a lower yield and TKM, higher proline content in the leaves, and lower Fv/Fm values. In both experimental years, there was a higher yield of the cultivar with blue aleurone (KM-72-18). In the case of cultivars with coloured grains, the promising use of the content substances in cultivars as natural means of increasing resistance to abiotic and biotic stressors seems to be promising.

Effect of Magnesium Fertilization Systems on Grain Yield Formation by Winter Wheat (Triticum aestivum L.) during the Grain-Filling Period

The application of magnesium significantly affects the components of the wheat yield and the dry matter partitioning in the grain-filling period (GFP). This hypothesis was tested in 2013, 2014, and 2015. A two-factorial experiment with three rates of magnesium (0, 25, 50 kg ha−1) and four stages of Mg foliar fertilization (without, BBCH 30, 49/50, two-stage) was carried out. Plant material collected at BBCH: 58, 79, 89 was divided into leaves, stems, ears, chaff, and grain. The wheat yield increased by 0.5 and 0.7 t ha−1 in response to the soil and foliar Mg application. The interaction of both systems gave + 0.9 t ha−1. The Mg application affected the grain yield by increasing grain density (GD), wheat biomass at the onset of wheat flowering, durability of leaves in GFP, and share of remobilized dry matter (REQ) in the grain yield. The current photosynthesis accounted for 66% and the REQ for 34%. The soil-applied Mg increased the REQ share in the grain yield to over 50% in 2014 and 2015. The highest yield is possible, but provided a sufficiently high GD, and a balanced share of both assimilate sources in the grain yield during the maturation phase of wheat growth.

Relationship Between the Vascular Bundle Structure of Panicle Branches and the Filling of Inferior Spikelets in Large-Panicle Japonica Rice

The vascular bundles of rice panicles serve to connect the source and the sink, as well as serving as a channel for the transportation of materials. In this study, two homozygous japonica rice strains were used as materials. The vascular bundle structures of the branches in different positions within a rice panicle were observed, and their cross-sectional areas were calculated. In addition, the ultrastructure of the central large vascular bundle (LVB) phloem in the rachillae of superior spikelets (SS) and inferior spikelets (IS) was observed during the grain filling period. Moreover, the soluble sugar and protein contents of the SS and IS rachillae were also measured to study whether the differences in the structure of vascular bundles of the branches were related to the plumpness of grain at different positions. The results showed that vascular bundle cross-sectional areas of the basal primary branches were greater than those in the upper primary branches. Moreover, there was little difference in the areas of vascular bundles between the basal secondary branches and upper secondary branches. However, the vascular bundle areas of the IS rachillae were lower than those in the SS rachillae. Therefore, we believe that the poor vascular tissue channel of the IS rachillae could be the limiting factor in IS plumpness. The results also showed that a similar time course in the degradation pattern of some organelles of the sieve elements and companion cells in central LVB was observed in the SS rachillae and IS rachillae during the grain filling period. Compared with the IS rachillae, more abundant mitochondria and plasmodesmata were found in the companion cells of SS rachillae at the beginning of the filling stage, while no significant differences between SS and IS rachillae were identified at the middle and late filling stages, which implies that the SS rachillae were relatively more effective at transportation compared with the IS rachillae at the initial filling stage. Therefore, the undeveloped vascular bundles of the IS rachillae and their poor physiology and lack of ability to transport at the initial filling stages could be the limiting factor in IS plumpness.

Genetic Improvement of Post-Heading Root Morphology and Physiology Facilitating Yield Increase of japonica Inbred Rice

Since genetic improvement greatly promoted an increased yield japonica inbred rice in east China after the 1990s, better root characteristics were certainly expected. In 2018 and 2019, nine japonica inbred rice released in the 1990s, 2000s, and 2010s were investigated to evaluate the changes in root morpho-physiology and identify root traits that contributed to the positive yield trends during the genetic process. The 2010’s rice had 8.0 and 4.3% higher grain yield than the 1990’s and the 2000’s rice, respectively (p < 0.05). Genetic yield gain was mainly attributed to the increased spikelets per panicle. Compared with the 1990’s and the 2000’s rice, the 2010’s rice had higher shoot biomass at heading and maturity (p < 0.05), as well as root biomass (p < 0.05), especially for root biomass of 15–30 cm soil depth. Leaf area index (LAI), soil-plant analysis development (SPAD) values, and leaf photosynthetic rate at middle grain-filling period (MGP) and late grain-filling period (LGP) were all increased. The 2010’s rice had consistently higher root length and volume, root oxidation activity, and root bleeding rate at MGP and LGP than the 1990’s and the 2000’s rice (p < 0.05). Positive correlations were detected between root length and volume, root oxidation activity, and root bleeding rate at MGP, LGP, and SPAD values, leaf photosynthetic rate at MGP and LGP, and higher shoot biomass accumulation after heading and grain yield (p < 0.05 or p < 0.01). The present study implied that genetic improvement optimized post-heading root morphology and physiology, which maintained shoot stay-green and facilitated biomass accumulation and yield increase in japonica inbred rice during the genetic process since the 1990s.

BIPLOT ANALYSIS FOR IDENTIFICATION OF SUPERIOR GENOTYPES IN A RECOMBINANT INBRED POPULATION OF WHEAT UNDER RAINFED CONDITIONS

Physiological traits of wheat genotypes and their trait relation to drought conditions are important to identify the genotype in target environments. Thus, genotype selection should be based on multiple physiological traits in variable environments within the target region. This study was conducted at Punjab Agricultural University during rabi crop seasons 2012-13 and 2013-14 to study the recombinant inbred lines (RILs) of wheat genotypes derived from traditional landraces and modern cultivars (C518/2*PBW343) based on various morpho-physiological traits. A total of 175 RILs were selected for this study based on various tolerance indices. The genotype by trait (GT) biplot analysis was applied to data from seven high-yielding RILs grown under irrigated (E1) and rainfed environments (E2). The GGE biplot explained 100% of the total variation for chlorophyll content, grain filling period, peduncle length, water-soluble carbohydrates, grain number, grain yield, and 95.1% for canopy temperature, 94.9% for thousand-grain weight. GT-biplots indicated that the relationships among the studied traits were not consistent across environments, but they facilitated visual genotype comparisons and selection in each environment. RIL 84 and RIL108 were close to the average environment (ideal genotype) for all traits studied except chlorophyll content. A well-performing genotype with great environmental stability is called an "ideal genotype. Among all entries, these genotypes performed well. Therefore, among the traits studied, grain filling period, peduncle length, canopy temperature, water soluble carbohydrates, and 1000 grain weight contributed to grain yield under a stress environment. Furthermore, it may be used as a donor material in breeding programs and QTLs mapping.

Understanding Wheat Starch Metabolism in Properties, Environmental Stress Condition, and Molecular Approaches for Value-Added Utilization

Wheat starch is one of the most important components in wheat grain and is extensively used as the main source in bread, noodles, and cookies. The wheat endosperm is composed of about 70% starch, so differences in the quality and quantity of starch affect the flour processing characteristics. Investigations on starch composition, structure, morphology, molecular markers, and transformations are providing new and efficient techniques that can improve the quality of bread wheat. Additionally, wheat starch composition and quality are varied due to genetics and environmental factors. Starch is more sensitive to heat and drought stress compared to storage proteins. These stresses also have a great influence on the grain filling period and anthesis, and, consequently, a negative effect on starch synthesis. Sucrose metabolizing and starch synthesis enzymes are suppressed under heat and drought stress during the grain filling period. Therefore, it is important to illustrate starch and sucrose mechanisms during plant responses in the grain filling period. In recent years, most of these quality traits have been investigated through genetic modification studies. This is an attractive approach to improve functional properties in wheat starch. The new information collected from hybrid and transgenic plants is expected to help develop novel starch for understanding wheat starch biosynthesis and commercial use. Wheat transformation research using plant genetic engineering technology is the main purpose of continuously controlling and analyzing the properties of wheat starch. The aim of this paper is to review the structure, biosynthesis mechanism, quality, and response to heat and drought stress of wheat starch. Additionally, molecular markers and transformation studies are reviewed to elucidate starch quality in wheat.

Prediction of municipality-level winter wheat yield based on meteorological data using machine learning in Hokkaido, Japan

This study analyzed meteorological constraints on winter wheat yield in the northern Japanese island, Hokkaido, and developed a machine learning model to predict municipality-level yields from meteorological data. Compared to most wheat producing areas, this island is characterized by wet climate owing to greater annual precipitation and abundant snowmelt water supply in spring. Based on yield statistics collected from 119 municipalities for 14 years (N = 1,516) and high-resolution surface meteorological data, correlation analyses showed that precipitation, daily minimum air temperature, and irradiance during the grain-filling period had significant effects on the yield throughout the island while the effect of snow depth in early winter and spring was dependent on sites. Using 10-d mean meteorological data within a certain period between seeding and harvest as predictor variables and one-year-leave-out cross-validation procedure, performance of machine learning models based on neural network (NN), random forest (RF), support vector machine regression (SVR), partial least squares regression (PLS), and cubist regression (CB) were compared to a multiple linear regression model (MLR) and a null model that returns an average yield of the municipality. The root mean square errors of PLS, SVR, and RF were 872, 982, and 1,024 kg ha−1 and were smaller than those of MLR (1,068 kg ha−1) and null model (1,035 kg ha−1). These models outperformed the controls in other metrics including Pearson’s correlation coefficient and Nash-Sutcliffe efficiency. Variable importance analysis on PLS indicated that minimum air temperature and precipitation during the grain-filling period had major roles in the prediction and excluding predictors in this period (i.e. yield forecast with a longer lead-time) decreased forecast performance of the models. These results were consistent with our understanding of meteorological impacts on wheat yield, suggesting usefulness of explainable machine learning in meteorological crop yield prediction under wet climate.

Night-Warming Priming at the Vegetative Stage Alleviates Damage to the Flag Leaf Caused by Post-anthesis Warming in Winter Wheat (Triticum aestivum L.)

The asymmetric warming in diurnal and seasonal temperature patterns plays an important role in crop distribution and productivity. Asymmetric warming during the early growth periods of winter wheat profoundly affects its vegetative growth and post-anthesis grain productivity. Field experiments were conducted on winter wheat to explore the impact of night warming treatment in winter (Winter warming treatment, WT) or spring (Spring warming treatment, ST) on the senescence of flag leaves and yield of wheat plants later treated with night warming during grain filling (Warming treatment during grain filling, FT). The results showed that FT decreased wheat yield by reducing the number of grains per panicle and per 1,000-grain weight and that the yield of wheat plants treated with FT declined to a greater extent than that of wheat plants treated with WT + FT or ST + FT. The net photosynthetic rate, chlorophyll content, and chlorophyll fluorescence parameters of the flag leaves of wheat plants treated with WT + FT or ST + FT were higher than those under the control treatment from 0 to 7 days after anthesis (DAA) but were lower than those under the control treatment and higher than those of wheat plants treated with FT alone from 14 to 28 DAA. The soluble protein and Rubisco contents in the flag leaves of wheat plants treated with WT + FT or ST + FT were high in the early grain-filling period and then gradually decreased to below those of the control treatment. These contents were greater in wheat plants treated with WT + FT than in wheat plants treated with ST + FT from 0 to 14 DAA, whereas the opposite was true from 21 to 28 DAA. Furthermore, WT + FT and ST + FT inhibited membrane lipid peroxidation by increasing superoxide dismutase and peroxidase activities and lowering phospholipase D (PLD), phosphatidic acid (PA), lipoxygenase (LOX), and free fatty acid levels in the early grain-filling period, but their inhibitory effects on membrane lipid peroxidation gradually weakened during the late grain-filling period. Night-warming priming alleviated the adverse effect of post-anthesis warming on yield by delaying the post-anthesis senescence of flag leaves.

Performance and Stability of Different Monoecious Hemp Cultivars in a Multi-Environments Trial in North-Eastern Italy

The seed yield in hemp (Cannabis sativa L.) is strongly influenced, besides by genotype, by environment and the genotype x environment interaction, so establishing the fitness and stability of hemp cultivars in multiple environments is necessary. The purpose of this study was to investigate the performance and degree of stability and variance of seed yield, the main related traits, and the correlation among the traits in five hemp monoecious cultivars cultivated in six different environments. The environments resulted from the combination of four locations, two years, and two delayed sowings in a Mediterranean area of north-eastern Italy, and the stability index of the weighted average of absolute scores (WAAS) was used in order to identify the most productive and stable genotypes on the basis of their deviation from the average performance across environments. In this studied area, early varieties, such as Fedora and Felina, proved to be the best performing and stable for seed yield and both increased their yield in correspondence to delayed sowing times, opening up the possibility of cultivating hemp as a second crop. Among the climate parameters, high temperatures during the early grain filling period led to a progressive decrease in seed yield. For a dual-purpose crop, a good compromise could be a late monoecious cultivar (like Futura, in the present experiment), which, if sown early, could certainly provide notable biomass production and acceptable seed yield.