Duration Of Grain Research Articles

Effect of Nitrogen Management Practices on Photosynthetic Characteristics and Grain Yield of Wheat in High-Fertility Soil

The uneven soil fertility made it difficult to implement the recommended nitrogen (N) management practices in the North China Plain (NCP). In order to clarify the effect of N managements in high-fertility soil with a perennial wheat yield of 10,500 kg ha−1 on photosynthetic characteristics, grain yield, N agronomic efficiency (NAE), and water use efficiency (WUE), a trial was conducted from 2022 to 2024. Main plots were N rates of 0 (N1), 150 (N2), 210 (N3), and 270 (N4) kg N ha−1; The sub-plots adopted fertigation (F) and traditional fertilization method (T). The results showed that, compared with T, F increased the intercept rate of photosynthetic effective radiation of canopy, net photosynthetic rate, stomatal conductance, and transpiration rate of flag leaves, as well as the activity of phosphate sucrose synthase and sucrose content. It enhanced dry matter transport and contribution to grain. Under N2, the time required to reach the maximum grain filling rate, duration of grain filling and active grain-filling period of F were improved. Grain yield of N2 was increased by 27.81% and 6.75% compared to N1 and N3, respectively. NAE was improved by 48.63% and 51.47%, and WUE was improved by 20.71% and 9.85%. Therefore, the best effect was achieved by using fertigation and the N rate of 210 kg ha−1 in high-fertility soil.

Maize Responses to High Night Temperature During Postflowering and Early Grain Filling: Effects on Yield Components, Kernel Growth and Dry Matter Allocation

ABSTRACTWarm night frequency has increased steadily in the last years across maize production regions, but high night temperature (HNT) effects on growth, grain yield and maize dry matter allocation (DMA) to different plant organs remain poorly understood. In this study, we aimed to (i) analyse the DMA among reproductive and vegetative organs, (ii) evaluate the individual kernel weight through its determinants, rate and duration of grain filling and (iii) quantify changes in grain yield per plant and its components due to HNT during the postflowering and early grain‐filling period. Field‐grown maize was subjected to HNT induced by shelters during a 15‐ or 30‐day period after silking, encompassing the postflowering period (HNT15) and extending the heating into early grain filling (HNT30), respectively. The HNT was applied from 1900 to 0700 h while control plots remained at ambient night temperature (ANT). Kernel number per plant was decreased under both temperature regimes (i.e., HNT15 and HNT30); however, significant reductions in grain yield were only observed under HNT30. The DMA during the heating period was differentially affected by the duration of heating. While DMA to the stem was likewise reduced by both heating treatments, the partition to the uppermost ear was only reduced under HNT30. Related to the lack of response to HNT treatments of the rate and duration of grain filling, the individual kernel weight was not reduced. The source‐sink ratio was not affected by HNT, meanwhile, the apparent reserve use was significantly reduced under HNT30. Our results demonstrate that the magnitude of HNT effects is subjected to the duration of the heating period, but also depends on the intensity of heating explored across seasons, especially for kernel number and grain yield.

Winter wheat source‐sink relationships under various planting modes, complementary irrigation, and planting densities

AbstractVarious agronomic practices can affect the processes of aboveground dry matter accumulation (source) and grain filling (sink), resulting in yield differences. Improved source‐sink relationships can facilitate the production and accumulation of assimilates to increase the productivity of winter wheat (Triticum aestivum L.). A two‐season field experiment was undertaken on winter wheat during 2020–2021 and 2021–2022. In a split‐split‐plot design with three replicates (randomized blocks), we compared two planting modes (ridge‐furrow planting with plastic mulching [RFPM]; traditional flat planting [TF]), two complementary irrigation levels (I30+30: 30+30 mm; I0: no irrigation), and three planting densities (D1, D2, and D3: 240, 360, and 480 plants m−2). The results showed that RFPMI30+30 significantly increased maximum yield by 28.5% compared with TFI0. Although D3 increased the number of effective spikes per unit area and duration of grain filling compared to D2, it reduced the number of grains per spike, 1000‐grain weight, and average filling rate. Compared to TF and I0, RFPM and I30+30 improved the sink/source ratio by 5.3% and 6.5%, respectively. Grain yield peaked at D2 in the RFPM and at D3 in the TF. Medium planting density (D2) and complementary irrigation (I30+30) during the wintering and reviving periods under RFPM can achieve better source‐sink balance relationships and the maximum grain yield of winter wheat. Overall, we believe that in most cases, wheat yields are source‐limited and can be improved by ridge‐furrow planting with plastic mulching, complementary irrigation, and planting density regulation.

Optimal sowing time to adapt soybean production to global warming with different cultivars in the Huanghuaihai Farming Region of China

ContextThe Huanghuaihuai Farming Region (HFR) is one of China’s largest soybean production zones, with climatic conditions in the HFR being near ideal. In recent decades, however, global warming has increasingly inhibited soybean production in this region. ObjectiveOur aim was to determine whether planting time and/or genetics (heat-resilient and heat-sensitive cultivars) enable adaptation of soybean cropping systems to the changing climate. MethodsTwo-year split-plot design field experiments comprising five different sowing dates and three cultivars (namely heat-resilient, heat-sensitive and widely grown ones) were conducted in the HFR in 2020 and 2021. ResultsDelayed sowing dates significantly elevated the average minimum temperature in the vegetative growth stage, fostering soybean growth and consequently truncating the vegetative growth stage. Later sowing reduced the occurrence of heat stress and minimized negative influences of heat stress on yield. Higher heat stress in the first two sowing treatments (1 June and 10 June) negatively influenced yields of Hedou14 (heat-sensitive cultivar) and Zhonghuang13 in 2020, while the highest yield was obtained for the third sowing treatment (20 June) for these two cultivars. In general, Jidou21 (heat-resilient cultivar) showed greater tolerance to increasing temperature, with higher yield at earlier sowing. Delayed sowing decreased temperature exposure and growing degree days (GDD), reducing the duration of grain filling, leaf area index and photosynthesis, in turn decreasing grain number per plant and 100-grain weight. Taken together, such factors inhibited yield of all cultivars in the year without heat stress. In contrast, high precipitation (2021) prolonged grain filling and increased yield. ConclusionsWe contend that optimizing sowing time is crucial for mitigating heat stress in heat-sensitive cultivars. We suggest that high yield is more likely to be realized when crops are exposed to GDD > 500℃·d and precipitation > 250 mm during grain filling. ImplicationsFuture studies aiming to elicit optimal sowing times for soybean should consider cultivar heat sensitivity relative to long term climatic conditions of the target agro-ecological region.

Reproductive Development and Yield Components of Bario Sederhana Rice in Response to Photoperiod

A series of controlled environment treatments were conducted to quantify reproductive development and yield components of Bario Sederhana rice grown under five photoperiod regimes (8, 9, 10, 11, & 12 h). A ‘broken-stick’ linear regression of heading rate against photoperiod was used to determine the cardinal photoperiods for heading. The reproductive development towards photoperiod showed a delayed pattern in time to heading, anthesis, and maturity under lengthening photoperiod from 10 to 12 h. For example, under 10 h photoperiod the crops required 1680 °Cd (70.8 days) from emergence to heading but took an extended duration of 3147 °Cd (132.6 days) when they were sown at 12 h photoperiod. The prolonged time taken for reproductive development modified by photoperiod resulted in higher yield components. This is because the lengthening time from heading to maturity extended the duration of grain filling. The longest photoperiod of 12 h gave the highest percentage of filled spikelets (65.3%) thus consequently leading to the heaviest grain weight of 1.4 g per panicle. The base, optimum, and maximum photoperiod for heading were estimated to be 7.4 h, 10 h, and 14.8 h, respectively.

Booting heat stress alters leaf photosynthesis, growth rate, phenology and yield in rice

BackgroundThe phenomenon of global warming results in a significant rise in temperature which adversely affects the growth, physiology, and yield of rice. In order to gain insight into the impacts of booting heat stress (at 42 °C, 3 h for 7 days), we investigated its effect in three rice genotypes, namely, N22, KDML105 and IR64. ResultsBooting heat stress caused an extended phenology and a lower photosynthesis and plant growth rate but an increase in chalkiness. Although, the prolonged phenology from dough to physiological maturity resulted in a longer duration of grain filling, the adverse effects of this were a significantly lower yield component, yield and harvest index across all varieties of rice. Among cultivars, N22 demonstrated an adapted ability to maintain leaf gas exchange and compensated for the vegetative part by an increase in tiller numbers resulting in a less affected growth rate. It caused extended grain filling by prolonging the phenology. Consequence, N22 had the lowest reduction in number of seed panicle−1, number of filled seeds hill−1, yield, harvest index, and percentage chalkiness. KDML105 was adapted to booting heat stress by maintaining leaf gas exchange, increasing specific leaf area and prolonging phenology. The longest extended phenology and high photosynthesis during dough grain were associated with moderate yield reduction and chalkiness. Nonetheless, IR64 demonstrated significant reductions in photosynthesis, growth rate, and yield but the highest percentage of grain chalkiness. ConclusionTherefore, the response of N22, KDML105 and IR64 to booting heat stress could be indicated as being heat tolerant, moderately heat sensitive, and heat sensitive, respectively. This approach can be applied to crop modeling and rice heat tolerance in breeding programs.

THE INFLUENCE OF METEOROLOGICAL CONDITIONS ON THE DURATION OF THE GROWING SEASON IN THE LINES OF SPRING SOFT WHEAT ON CHERNOZEM SOILS OF NORTHERN KAZAKHSTAN

The relevance of the topic lies in the fact that the study of breeding lines of various ecological origins is of paramount importance for breeding. When selecting breeding material, it is necessary to take into account the peculiarities of soil and climatic conditions. For the sharply continental climate of Northern Kazakhstan, one of the most important characteristics of the variety for obtaining a high yield is the duration of the growing season and interphase periods.
 This article presents the results of a study of a line of spring soft wheat with a high adaptive ability: high productivity, early maturity, resistance to pathogens and endurance to environmental stress.
 The experiments were laid in the Kokshetau Experimental Production Farm LLP in 2021-2022. Agrotechnics adopted for the zone. The predecessor is pure steam. The sowing period is May 22-23, the seeding rate is 3.0 million. germinating seeds per 1 ha. 13 lines of spring soft wheat of medium-ripened and medium-early ripeness groups were studied.
 The yield, the elements of its structure and the duration of the growing season were determined according to the methodology of the state variety testing.
 The studied lines are valuable for practical breeding of spring soft wheat varieties. The growing season of the variety is not constant, but varies depending on both the climatic conditions of the zone and the year of cultivation. The duration of vegetation mainly depends on the temperature and water regime. At the same time, the duration of the growing season from sowing to earing closely depends on the sum of the average daily temperatures, the duration of grain filling, and also on the humidification conditions.
 According to our research, the lines were distinguished by an elongated tillering period, and «shoots-earing» (37-46 days), and shortened – «earing-ripening» (38-39 days).
 
 
 

Nutrient Cycling and Nitrogen Management Impact of Sowing Method and Soil Water Consumption on Yield Nitrogen Utilization in Dryland Wheat (Triticum aestivum L.)

The current study was designed to investigate the best sowing method that encourages dry matter accumulation to increase dryland wheat yield, grain quality, and protein content. Three different seeding methods were applied: (I) wide-space sowing (WSS), (II) furrow sowing, and (III) drill sowing. Two nitrogen levels, namely low nitrogen (N1) and high nitrogen (N2), were also applied, and the pure nitrogen was 150 kg ha−1 and 210 kg ha−1, respectively. Wide-space sowing significantly increased the ears and yield production, the maximum, and average grain-filling rate while furrow sowing delayed the disappearance of the population after anthesis, increased the duration of grain filling, and then significantly increased the number of spikes and the 1000-grain weight increased, respectively. Drill sowing compared to wide-space sowing significantly increased the content of nitrogen in the grain of the nitrogen harvest index, and it increased the content of protein and the yield of protein, respectively. In addition, the grain yield and protein yield of wide-precision sowing were significantly higher than that of trench sowing. Our findings suggest that wide-space sowing was beneficial for increasing water consumption during the growth period, increasing the tiller dynamics, improving the plant dry matter quality, and increasing the grain protein.

Effect of chemical regulators on the recovery of leaf physiology, dry matter accumulation and translocation, and yield-related characteristics in winter wheat following dry-hot wind

Dry-hot wind stress causes losses in wheat productivity in major growing regions worldwide, especially winter wheat in the Huang-Huai-Hai Plain of China, and both the occurrence and severity of such events are likely to increase with global climate change. To investigate the recovery of physiological functions and yield formation using a new non-commercial chemical regulator (NCR) following dry-hot wind stress, we conducted a three-year field experiment (2018–2021) with sprayed treatments of tap water (control), monopotassium phosphate (CKP), NCR at both the jointing and flowering stages (CFS), and NCR only at the jointing stage (FSJ) or flowering stage (FSF). The leaf physiology, biomass accumulation and translocation, grain-filling process, and yield components in winter wheat were assessed. Among the single spraying treatments, the FSJ treatment was beneficial for the accumulation of dry matter before anthesis, as well as larger increases in the maximum grain-filling rate and mean grain-filling rate. The FSF treatment performed better in maintaining a high relative chlorophyll content as indicated by the SPAD value, and a low rate of excised leaf water loss in flag leaves, promoting dry matter accumulation and the contribution to grain after anthesis, prolonging the duration of grain filling, and causing the period until the maximum grain-filling rate reached earlier. The CFS treatment was better than any other treatments in relieving the effects of dry-hot wind. The exogenous NCR treatments significantly increased grain yields by 12.45–18.20% in 2018–2019, 8.89–13.82% in 2019–2020, and 8.10–9.00% in 2020–2021. The conventional measure of the CKP treatment only increased grain yield by 6.69% in 2020–2021. The CFS treatment had the greatest mitigating effect on yield loss under dry-hot wind stress, followed by the FSF and FSJ treatments, and the CKP treatment only had a minimal effect. In summary, the CFS treatment could be used as the main chemical control measure for wheat stress resistance and yield stability in areas with a high incidence of dry-hot wind. This treatment can effectively regulate green retention and the water status of leaves, promote dry matter accumulation and efficient translocation, improve the grain-filling process, and ultimately reduce yield losses.

Design and Experiment of Real-Time Grain Yield Monitoring System for Corn Kernel Harvester

Real-time crop harvest data acquisition from harvesters during harvesting operations is an important way to understand the distribution of crop harvest in the field. Most real-time monitoring systems for grain yield using sensors are vulnerable to factors such as low accuracy and low real-time performance. To address this phenomenon, a real-time grain yield monitoring system was designed in this study. The real-time monitoring of yield was accomplished by adding three pairs of photoelectric sensors to the elevator of the corn kernel harvester. The system mainly consists of a signal acquisition and processing module, a positioning module and a visualization terminal; the signal acquisition frequency was set to 1 kHz and the response time was 2 ms. When the system operated, the signal acquisition and processing module detected the sensor signal duration of grain blocking the scrapers of the grain elevator in real-time and used the low-potential signal-based corn grain yield calculation model constructed in this study to complete the real-time yield measurement. The results of the bench tests, conducted under several different operating conditions with the simulated elevator test bench built, showed that the error of the system measurement was less than 5%. Field tests were conducted on a Zoomlion 4YZL-5BZH combined corn kernel harvester and the results showed that the average error of measured yield was 3.72%. Compared to the yield measurement method using the weighing method, the average error of the bench test yield measurement was 7.6% and the average error of yield measurement in field trials with a mass flow sensor yield measurement system was 16.38%. It was verified that the system designed in this study has high yield measurement accuracy and real-time yield measurement, and can provide reference for precision agriculture and high yield management.

Regulation of maize growth, nutrient accumulation and remobilization in relation to yield formation under strip-till system

ABSTRACT A two-year field experiment was conducted to elucidate the adaptive growth mechanism of maize under strip-till (ST) compared with conventional-till (CT). The biomass accumulation of ST plants was significantly lower than CT until V14 (14th leaf), but restored thereafter with one below-ear-node leaf reduced. At silking, the accumulation of nitrogen (N) was reduced by 8.3–10.7% compared to CT. During post-silking, vegetative-N remobilization was reduced by 20.4%, post-silking N uptake increased by 33.9% in ST compared to CT. Leaf senescence was delayed and more green leaf area at physiological maturity in ST. It is concluded that ST plants have the mechanism of ‘Recovery Growth Adaptation’ to get the similar yield as in CT plants: (1) facilitating growth rate at around V14 when the soil temperature was greatly improved to stabilize ear growth and grain number; (2) getting to silking the same time as in CT plants, so as to ensure the duration of grain filling; (3) increasing post-silking N uptake to fulfill the demand of grain development and reduce leaf N remobilization, so as to maintain leaf function and increase thousand-grain weight, which compensate for the loss of grain number per ear.

ОПТИМІЗАЦІЯ СТРОКІВ ЗБЕРІГАННЯЗЕРНОВИХ КУЛЬТУР НА ПОРТОВОМУ ЕЛЕВАТОРІ

The article presents an economic and mathematical model for optimizing the storage time of grain crops at the port elevator, taking into account price dynamics during the marketing year and the duration of grain storage in the port. The production of grain, its consumption and sale throughout the year, as well as the need for stocks of food, feed and seed funds, lead to the fact that some batches of grain are quickly spent on current needs or moved to places of consumption, while others are stored for a long time.Thus, grain storage can be short-term (from several days to one month) and long-term (more than one month).For the cargo owner, the issue of preserving the crop and the possibility of storing it until the most favorable prices are established on the grain market is important. Therefore, competent management of the duration of storage of the grain harvest is essential for the successful operation of the grain trader. The decision of the owner of the cargo when to sell his grain depends on the duration of the pre-sale storage of this grain (and therefore the costs associated with it), and its selling price on the market.Given the above, the cargo owner must develop a strategy for the sale of grain crops, taking into account the world market conditions, their own capabilities and tasks.The target function of the model for optimizing the shelf life of grain is the profit from the sale of these goods minus the costs of their storage and processing. In addition, the model takes into account the costs of processing and storing grain, a parameter that determines the acceleration of the growth of costs for grain storage with an increase in the duration of storage, the total duration of shipment/loading of grain, analysis, drying, processing, and the total duration of grain stay at the port elevator from the moment of its loading on the elevator until loading onto the vessel. Having a number of advantages, this model can be used by cargo owners, heads of stevedoring companies to make managerial decisions to determine the optimal period of stay at their own storage areas for reloaded grain.Keywords: optimization model, grain crops, storage time, price dynamics, port elevator.

Does temporary heat stress or low temperature stress similarly affect yield, starch, and protein of winter wheat grain during grain filling?

Temperature plays a critical role in wheat grain development. A controlled phytotron glasshouse study was done to investigate the effects of short-term low or high temperature stress on grain yield and the proportions of starch and protein in two wheat cultivars Ningmai 13 and Zhenmai 12. The duration of grain filling was longer under low temperature stress and was shorter under high temperature stress during various stages of grain filling. Grain filling rate, grain width, grain yield, contents of total starch and amylopectin of both cultivars were decreased by low or high temperature stress. However, the proportions of total protein, gliadin, and glutenin were increased dramatically after abnormal temperature stress. The significant increase in the proportion of protein was mainly caused by higher proportions of ω-gliadin and HMW-GS. For both cultivars, the formation of starch, protein, and grain yield was most sensitive to temperature stress during 15–17 days post anthesis (DPA), followed by 7–9 DPA for grain starch and yield formation, and 23–25 DPA for grain protein formation, respectively. Our study suggested that both high and low temperature stress after anthesis affected winter wheat grain yield, starch and protein accumulation, especially during the period of 15–17 DPA.

The Effects of Short-Term Exposure to Low Temperatures During the Booting Stage on Starch Synthesis and Yields in Wheat Grain.

Low temperatures (LT) in spring can have a major impact on the yields of wheat in winter. Wheat varieties with different cold sensitivities (the cold-tolerant Yannong 19 variety and the cold-sensitive Yangmai 18 variety) were used to study the responses of the wheat grain starch synthesis and dry material accumulation to short-term LT during the booting stage. The effects of short-term LT on the activities of key wheat grain starch synthesis enzymes, starch content and grain dry-matter accumulation were determined by exposing the wheat to simulated LT of from −2 to 2°C. Short-term LT stress caused a decrease in the fullness of the wheat grains along with decreased activities of adenosine diphosphate glucose pyrophosphorylase (AGPase, EC2.7.7.27), soluble starch synthase (SSS, EC2.4.1.21), granule-bound starch synthase (GBSS, EC2.4.1.21), and starch branching enzyme (SBE, EC2.4.1.18) at different spike positions during the filling stage. The rate of grain starch accumulation and starch content decreased with decreasing temperatures. Also, the duration of grain filling increased, the mean and the maximum filling rates were reduced and the quality of the grain dry-matter decreased. The number of grains per spike and the thousand-grain weight of the mature grains also decreased. Our data showed that short-term LT stress at the booting stage caused a decrease in the activities of key starch synthesis enzymes at the grain-filling stage. These changes reduced the accumulation of starch, decreased the filling rate, and lowered the accumulation of grain dry matter to ultimately decrease grain yields.

The Effect of Spike Row Type on the Grain Yield and Grain Filling Parameters in Barley (Hordeum vulgare L.) Genotypes under Semi-arid Conditions

Background: Barley (Hordeum vulgare L.) is one of the more important cultivated crops in the Mediterranean region, where drought and high temperatures during the grain filling stage are the main abiotic stresses limiting its production. The aim of this study is to evaluate the effects of the spike type on the grain yield, thousand kernels weight and some grain filling parameters.Methods: The present study was conducted on the experimental site of station ITGC in Setif, Algeria, eight Barley genotypes were tested during two cropping seasons (2017/2018 and 2018/2019) in a randomized block design with 3 replications.Result: The results proved significant effect of genotypes and spike types on the grain filling parameters, but no significant effect of spike type on the thousand kernels weight during the both cropping seasons. In addition, the spike type registered significant effect just during the second cropping season. Among the genotypes with 6 rows spike type the local genotype Fouarra have high grain yield (97.79 Q/ha) with a deviation of 37.57% from the total mean of the genotypes with 6 row spike type. Many studies proved that in 6-row barleys, the magnitude of contribution of grain number in grain yield was higher than contribution of grain weight. The grain growth of genotypes studied follows a sigmoid curve, during the first season (2017-2018) the duration of grain filling ranged between 24 days for Saida 183 and 28 days for Rihane 03, for the group of genotypes with 6 rows. In addition, the duration of grain filling for the 2 row genotypes varied from 24 days for G4 to 28 days for genotype G2. During the second season (2018-2019) and for the genotypes with 6 rows, the duration of the grain filling varied from 21 days for the Saida 183 and 26 days for the genotype Fouarra, for the genotypes with 2 rows the duration of grain filling ranged from 21 days for the genotype G2 to 26 days for the genotype G3. The correlation analysis between the grain filling parameters, GY and TKW demonstrate a significant and positive correlation between TKW and MGW and GFR (r = 0.82* and r = 0.84*, respectively). Overall, the genotype variation in grain filling velocity and duration was responsible for the difference in grain yield and the improvement in grain yield was achieved by the increasing in velocity or duration of grain filling.

Morpho-physiological characterization of two wheat genotypes with contrasting trait of heat tolerance

Various biotic and abiotic stresses adversely affect crop yield across the globe. Wheat is cool-season cereal crop and sensitive to rise in ambient growth temperature. Ninety genotypes were screened under heat stress and non-heat stress locations. Low heat susceptibility index of <0.5 for HD2189, N5643, Kenphad39, HD2501, NI179, NI5439, HS240, HD2428 and HD2687 indicated that they are heat tolerant and high susceptibility index of >1.5 for PBN142, NI9947, HD2320, GW190, HD2135, NI917 and Batavia indicated that they are heat susceptible. Based on grain yield and heat susceptibility index, two genotypes namely HD2189 and Batavia with contrasting response to heat stress were selected for the further studies. Their morphological and physiological characterization was carried out at seedling stage using 22°C as control and 33°C as heat stress. Under heat stress conditions, reduction for seedling growth traits, relative water content (RWC) and membrane thermostability (MTS) was less in HD2189 (25.3%, 10.2%, 13%) compared to Batavia (55.3%, 34.4%, 30%). HD2189 maintained lower canopy temperature with depression values in the range of 3.75 to 8°C compared to Batavia (2.82 to 5.10°C). The conversion of source to sink was better for HD2189 as displayed by translocated dry matter (TDM), translocation efficiency (TE), contribution of plant assimilates (CPA), longer duration of grain filling, grain yield and yield components under high temperature. Trend for electron transport rate of PSII (ETRII) and effective quantum yield (YII) for both the varieties at 22°C and 33°C was similar. However, Batavia plants were adjusting through non-regulated heat dissipation indicating damage to the photosynthetic apparatus whereas HD2189 showed higher regulated heat dissipation. Thus, genotype HD2189 showed heat tolerance at seedling and adult plant stages compared to Batavia.

Assimilate limitation compensating factors under environmental stresses in wheat

In recent years, considerable efforts have been made to understand the factors controlling grain weight in wheat. In addition to sink capacity, the supply of assimilates for developing grain determines the weight of the grain. The current photosynthesis of the flag leaf is the most important source of assimilation, and the onset and rate of senescence are important factors for determining grain yield. Hence stress induced leaf senescence can reduce the supply of assimilates for grains. Under such conditions, assimilate contributions of stored non structural carbohydrates in stem and photosynthesis of non foliar parts of the plant such as spike are crucial for grain development. Non structural carbohydrates in wheat stem have been estimated and efforts have been made to reveal the mechanisms of assimilate partitioning. The hormone levels and activities of enzymes involved in assimilate partitioning and carbohydrate metabolism in wheat stem and grains have been significantly correlated with grain filling in wheat. Remobilization efficiency of stem reserves is increased under heat or drought stress along with increase in the proteins associated with senescence and ROS handling in the tolerant cultivars. The heat and drought tolerant wheat cultivars have a higher WSC content in stem, higher mobilization efficiency, longer duration of grain filling and stronger sink activity. However, some of the key issues such as intra-spike assimilation distribution have not been sufficiently addressed. This review has been compiled for information related to assimilate supply to the developing wheat grain under stress conditions and also enlists opportunities to translate this knowledge into traits for improvement of climate resilience in wheat.

Effect of Irrigation Threshold on Crop Performances in Wet Seeded Rice

Decreasing availability and increasing costs of water and labour are driving researchers and farmers to find management strategies that increase input water productivity and reduce labour requirement in rice production. Wet seeding instead of transplanting greatly reduces the labour requirement for crop establishment, whereas use of alternate wetting and drying (AWD) instead of continuous flooding reduces irrigation input. However, the safe threshold for irrigating wet seeded rice (WSR), and how this varies with growth stage, has not been established. Therefore, a greenhouse experiment was conducted to determine the effects of different degrees of irrigation threshold during different crop growth stages on crop performance of WSR. This was done in greenhouse experiment in the 2011 wet season at the International Rice Research Institute, Los Baños, Philippines. In the experiments, water stresses were applied by withholding irrigation until soil water tension increased to 10, 20 or 40 kPa at 10 cm below the soil surface. Soil water tension was measured using 30 cm long gauge tensiometer installed with the center of the ceramic cup. The stresses were applied during three crop stages: 3-leaf (3L) to panicle initiation (PI), PI to flowering (FL), and FL to physiological maturity (PM). The experiment was also included a continuously flooded (CF) treatment. Stress during 3L to PI increased the time to PI (by 2 to 4 days) but reduced the duration of grain filling by 3 to 5 days, the larger values with 20 and 40 kPa thresholds. There was no effect of stress thresholds of 10 to 40 kPa during PI-FL on crop duration. Stress during grain filling reduced the duration of grain filling by 6 days for all thresholds. Stresses of 20 and 40 kPa during 3L to PI reduced green leaf and tiller density at PI, but this effect disappeared with the imposition of CF after PI. There were consistent trends for lower final biomass as the level of water deficit stress increased, and imposition of stresses of 20 and 40 kPa at any or all three stages significantly reduced biomass compared with CF. These results suggest that, for shortening the ripening period, water stress may be imposed as 10 to 20 kPa during FL to PM.
 Bangladesh Rice j. 2018, 22(1): 73-81

In sink-limited spring barley crops, light interception by green canopy does not need protection against foliar disease for the entire duration of grain filling

Disease management in cereals is heavily reliant on the use of fungicides, but development of anti-microbial resistance, effects on non-target organisms and persistence of active ingredients in the environment and food chain challenge the sustainability of this approach. Better targeting of fungicides according to crop need within an integrated pest management (IPM) programme could improve the sustainability of disease management. The objectives of the present study were to determine 1) the duration of protection of post-anthesis canopy light interception required to maximise the yield of spring barley and 2) to relate this to the response of crops to timing of fungicide applications. As the yield of spring barley is considered to be sink-limited (limited by the number and storage capacity of grains) rather than source-limited (limited by the amount of carbon assimilates available for grain filling) in many environments, we hypothesised that the canopy would not need to be protected for the entire grain filling period. Field experiments were conducted at two sites in the UK (Edinburgh and Herefordshire) over four years, providing contrasting climates and soil types. Shading was used to determine the response of grain filling to reductions in light interception over defined intervals, thereby mimicking effects of foliar disease on light interception, as shading is easier to control than the onset and duration of disease epidemics. Shades giving ˜67% reduction in photosynthetically active radiation (PAR) were erected over plots of disease-free crops at weekly intervals commencing at flowering and leaving them in place until harvest. The required duration of protection of light interception was estimated as the period from flowering to the time at which the onset of shading had no effect on yield. In a separate experiment the response to five fungicide timing treatments was determined on three relatively disease-susceptible varieties. Timings were the start of stem extension (referred to here as T1 only) and T1 followed by a second application at either flag leaf emergence (early T2), flowering (mid T2) or the start of rapid grain growth (late T2); untreated plots served as controls. Results showed that canopy PAR interception does not need to be protected for the entire grain filling period in order to maximise yield. The critical period determined from shading was 3–5 weeks after 50% ear emergence depending on the site year, or the first 72–90% of grain filling. There was a significant yield response to fungicide treatment in all site-years of 0.33−0.74 t ha−1 irrespective of the disease severity and yield potential of the site. Where disease severity was low to moderate a T1 application on its own gave sufficient protection during grain filling to maximise yield. Later applications increased healthy area PAR interception further, but effects occurred late during grain filling and did not increase yield. When disease was severe a T1 plus mid T2 application was required to protect PAR interception during the critical early to mid- grain filling period. These results provide the necessary physiological understanding to help target fungicide applications according to crop need.

Different grain-filling rates explain grain-weight differences along the wheat ear.

Thousand grain weight is one of the components determining wheat grain yield. It represents the average value of individual grain weights which depends on position within the ear and on positon within the spikelet. Our objective was to quantify the influences of individual floret anthesis date, of carpel weight at anthesis and of rate and duration of grain filling, on variation in individual final grain weight. Two bread wheat cultivars were grown in a greenhouse and their ears were sampled from anthesis through to harvest. Each ear was divided into three parts—basal, central and apical—where the two proximal grains were dissected from each of two spikelets. We analysed (i) the flowering time shift within the ear and within the spikelet; and (ii) the growth kinetics during grain filling in relation to position along the ear. For both cultivars, florets located in the central part of the ear were the first to reach anthesis followed by those in the apical part and then the basal part. Within a spikelet, the floret located nearest the rachis flowered first followed by the more distal ones. We found no significant systematic effect of flowering time-shift on final grain weight. Nevertheless, grains in the central part were heavier than the basal ones (9.75% smaller) and than the apical ones (18.25% smaller). These differences were explained mainly by differences in mean grain filling rates. Analysis of growth kinetics enabled an improved explanation of the variability of individual grain weight along the ear.