Grain-filling Period Research Articles

Physiological Traits Determining Yield Tolerance of Wheat to Foliar Diseases.

Tolerance is defined as the ability of one cultivar to yield more than another cultivar under similar disease severity. If both cultivars suffer an equal loss in healthy (green) leaf area duration (HAD) over the grain filling period due to disease presence, then the yield loss per unit HAD loss is smaller for a more tolerant cultivar. Little is understood of what physiological and developmental traits of cultivars determine disease tolerance. In this study, we use a mathematical model of wheat to investigate the effect of a wide range of wheat phenotypes on tolerance. During the phase from stem extension to anthesis, the model calculates the assimilate source and sink potential, allowing for dynamic changes to the source-sink balance by partitioning assimilates between ear development and storage of water-soluble carbon (WSC) reserves, according to assimilate availability. To quantify tolerance, rates of epidemic progress were varied on each phenotype, leading to different levels of HAD loss during the postanthesis, grain-filling period. Model outputs show that the main determinant of tolerance is the total amount of assimilate produced per grain during the rapid grain-fill period, leading to a strong positive correlation between HAD per grain and tolerance. Reductions in traits that affect carbon assimilation rate and increases in traits that determine the amount of structural biomass in the plant increase disease tolerance through their associated reduction in number of grains per ear. Some of the most influential traits are the canopy green area index, carbon use efficiency, and leaf specific weight. Increased WSC accumulation can either increase or decrease tolerance. Furthermore, a cultivar is shown to be maximally tolerant when a crop is able to just fill its total sink size in the presence of disease. The model has identified influential functional traits and established that their associations with tolerance have a mechanistic basis.

Sink-source relationship during rice grain filling is associated with grain nitrogen concentration

High grain nitrogen (N) concentration in crops may require to translocate more N from the vegetative tissues, cause faster plant senescence, alter sink-source balance during grain filling, and ultimately lower grain yield. Previous studies have shown that indica hybrid rice (IH) have shorter grain-filling period, and lower biomass and grain yield, compared with japonica/indica hybrid rice (JIH) and japonica conventional inbred rice (JC) in China. We hypothesise that these are caused by early senescence and poor sink-source balance after heading in IH as a result of its high grain N concentration. In this study, two JIH, two JC, and two IH varieties were grown in 2013 and 2014 at Ningbo, and in 2015 and 2016 at Yangzhou, China, and the observed dynamics of grain and crop biomass were fitted to mathematical equations to quantify sink-source relationships during grain filling. Compared with JC and IH varieties, JIH varieties showed higher sink growth and source capacity and 7.5–21.6% higher grain yield across years and sites. In JIH and JC genotypes, total source during grain filling was higher than the total sink value, whereas opposite was observed for IH genotypes. Source-sink difference, source/sink ratio, and grain-filling duration all negatively (P<0.01) correlated with grain N concentration at maturity. Compared with JIH and JC, IH accumulated more N in grains and translocated more N from leaf during the period from heading to maturity. We conclude that early senescence and poor sink-source balance after heading of IH was linked to its high grain N concentration, and sink-source relationships during rice grain filling were associated with grain N concentration. Further breeding and cultivation programmes should aim at improving sink-related traits in JIH and JC genotypes, whereas for IH varieties, whether yield was set by sink size or by any limited availability of pre-heading reserves remains to be further examined.

Effect of phosphorus and potassium foliage application post-anthesis on grain filling and hormonal changes of wheat

Foliage application of fertilizer is an important supplement for soil application fertilizer. Phosphorus (P) and Potassium (K) are important nutrient elements that significantly affect the grain weight and grain yield of wheat, and foliage application of K and P is mainly used for wheat production in the northern dryland region of China. However, the mechanism underlying the regulation of grain filling by foliage application of K and P is not understood. In the present study, monopotassium phosphate (KH2PO4), monosodium orthophosphate (NaH2PO4) and potassium chloride (KCl) were used for foliage application at the anthesis of wheat, and the changes of IAA, ABA, Z+ZR, GAs and ETH in wheat grain were measured during the grain filling process. The objective of this study was to investigate the effect of P and K foliage application on the grain filling process of wheat and to determine how changes in the endogenous hormones of the developing grains of winter wheat under P and K foliage application are related to the grain filling process. The results indicate that the effect of P and K foliage application on the grain filling of wheat is the difference. The K foliage application significantly increased the Z+ZR and ABA contents and decreased the ETH evolution rate in inferior grains, which promoted sink strength and increased the grain filling rate and the grain weight. In comparison, the P foliage application significantly promoted the activities of SOD, POD, and CAT and decreased the MDA content in the flag leaves and relieved the premature senility of the plant, which increased the active grain-filling period and the grain weight. For the heavy panicle cultivar, foliage P had a reasonable effect on grain filling, and for the light panicle cultivar, foliage K had a reasonable effect on grain filling. The mixture of P and K had an additive effect and prevented P and K deficiencies. Foliage application of KH2PO4 is an effectual measure for promoting the grain weight of wheat.

Uptake, distribution, and remobilization of iron and zinc among various tissues of wheat–Aegilops substitution lines at different growth stages

Biofortification of wheat for higher grain iron and zinc is the most feasible and cost-effective approach for alleviating micronutrient deficiency. The non-progenitor donor Aegilops species had 2–3 times higher grain iron and zinc content than the wheat cultivars, whereas the wheat–Aegilops substitution lines mostly of group 2 and 7 chromosomes had intermediate levels of grain micronutrients. The non-progenitor Aegilops species also had the highest iron content and intermediate-to-highest zinc content in straw, lower leaves, and flag leaves at the pre-anthesis, grain-filling, and maturity growth stages. The micronutrients accumulation status is followed by wheat–Aegilops substitution lines and is the least in wheat cultivars indicating that the donor Aegilops species and their substituted chromosomes possess genes for higher iron and zinc uptake and mobilization. The grain iron content was highly positively correlated with iron content in the plant tissues. Most of the lines had much higher iron and zinc content in all tissues during grain-filling period indicating higher iron and zinc uptake from soil during this stage. Although iron and zinc contents are nearly similar in grains, there was much less zinc content in the plant tissues of all the lines suggesting that the Triticeae species take up less zinc which is mobilized to grains more effectively than iron.

Türkiye Kökenli Yulaf Genotiplerinin Bazı Tarımsal Özellikler Bakımından Değerlendirilmesi

Farklı gen bankalarından elde edilen Türkiye kökenli 384 yerel yulaf genotipi 2012-2013 ve 2013-2014 ürün yıllarında iki yıl süreyle bazı tarımsal özellikler bakımından değerlendirilmiştir. Araştırmada 384 yerel yulaf genotipi ve 4 standart çeşit (Checota, Sebat, Faikbey ve Seydişehir) kullanılmış olup çalışmanın ekimi Augmented deneme desenine göre yapılmıştır. Yerel yulaf genotipleri Kahramanmaraş koşullarında sap kalınlığı (SK), bitki boyu (BB), salkım uzunluğu (SU), vejetatif periyot (VP), tane dolum periyodu (TDP), ekim olgunlaşma süresi (EOS), arpa sarı cücelik virüsü (ASCV), yatma oranı (Y), salkımdaki tane sayısı (STS), salkımdaki tane ağırlığı (STA), bin tane ağırlığı (BinTA) ve tek sıra verimi (TSV) gibi özellikler bakımından değerlendirilmiştir. İki yıllık ortalama verilere göre; genotipler arasındaki farklılık; SK, BB, SU, VP, EOS, BinTA ve TSV bakımından önemli olurken, genotiplerin SK, SU, VP, TDP, EOS, STS, STA, BinTA ve TSV gibi özellikleri yıllara göre önemli ölçüde değişmiştir. Yıl x genotip interaksiyonu ise SU, VP, EOS, BinTA ve TSV bakımından önemli bulunmuştur. İncelenen birçok özellik bakımından seçilen yerel genotipler standart çeşitlerden daha iyi sonuçlar vermiştir. Tek sıra verimi 4,65 g (TL444) ile 202,1 g (TL614) arasında değişmiştir. Tek sıra verimi yüksek olan diğer genotipler ise TL708, TL714, TL734 ve TL703 genotipleri olup bunların TSV‘leri sırasıyla, 167,85, 160,25, 153,90 ve 149,7 g olarak belirlenmiştir.

Yield, growth and grain nitrogen response to elevated CO2 in six lentil (Lens culinaris) cultivars grown under Free Air CO2 Enrichment (FACE) in a semi-arid environment

Abstract Atmospheric CO 2 concentrations ([CO 2 ]) are predicted to increase from current levels of about 400 ppm to reach 550 ppm by 2050. The direct benefits of elevated [CO 2 ] (e[CO 2 ]) to plant growth appear to be greater under low rainfall conditions, but there are few field (Free Air CO 2 Enrichment or FACE) experimental set-ups that directly address semi-arid conditions. The objectives of this study were to investigate the following research questions: 1) What are the effects of e[CO 2 ] on the growth and grain yield of lentil ( Lens culinaris ) grown under semi-arid conditions under FACE? 2) Does e[CO 2 ] decrease grain nitrogen in lentil? and 3) Is there genotypic variability in the response to e[CO 2 ] in lentil cultivars? Elevated [CO 2 ] increased yields by approximately 0.5 t ha −1 (relative increase ranging from 18 to 138%) by increasing both biomass accumulation (by 32%) and the harvest index (by up to 60%). However, the relative response of grain yield to e[CO 2 ] was not consistently greater under dry conditions and might depend on water availability post-flowering. Grain nitrogen concentration was significantly reduced by e[CO 2 ] under the conditions of this experiment. No differences were found between the cultivars selected in the response to elevated [CO 2 ] for grain yield or any other parameters observed despite well expressed genotypic variability in many traits of interest. Biomass accumulation from flowering to maturity was considerably increased by elevated [CO 2 ] (a 50% increase) which suggests that the indeterminate growth habit of lentils provides vegetative sinks in addition to reproductive sinks during the grain-filling period.

Responses to Hypoxia and Endoplasmic Reticulum Stress Discriminate the Development of Vitreous and Floury Endosperms of Conventional Maize (Zea mays) Inbred Lines

Major nutritional and agronomical issues relating to maize (Zea mays) grains depend on the vitreousness/hardness of its endosperm. To identify the corresponding molecular and cellular mechanisms, most studies have been conducted on opaque/floury mutants, and recently on Quality Protein Maize, a reversion of an opaque2 mutation by modifier genes. These mutant lines are far from conventional maize crops. Therefore, a dent and a flint inbred line were chosen for analysis of the transcriptome, amino acid, and sugar metabolites of developing central and peripheral endosperm that is, the forthcoming floury and vitreous regions of mature seeds, respectively. The results suggested that the formation of endosperm vitreousness is clearly associated with significant differences in the responses of the endosperm to hypoxia and endoplasmic reticulum stress. This occurs through a coordinated regulation of energy metabolism and storage protein (i.e., zein) biosynthesis during the grain-filling period. Indeed, genes involved in the glycolysis and tricarboxylic acid cycle are up-regulated in the periphery, while genes involved in alanine, sorbitol, and fermentative metabolisms are up-regulated in the endosperm center. This spatial metabolic regulation allows the production of ATP needed for the significant zein synthesis that occurs at the endosperm periphery; this finding agrees with the zein-decreasing gradient previously observed from the sub-aleurone layer to the endosperm center. The massive synthesis of proteins transiting through endoplasmic reticulum elicits the unfolded protein responses, as indicated by the splicing of bZip60 transcription factor. This splicing is relatively higher at the center of the endosperm than at its periphery. The biological responses associated with this developmental stress, which control the starch/protein balance, leading ultimately to the formation of the vitreous and floury regions of mature endosperm, are discussed.

Photosynthetic and stomatal traits of spike and flag leaf of winter wheat (Triticum aestivum L.) under water deficit

Xerophytic stomatal traits may help plants maintain photosynthetic rates under water deficit; however, such adaptations are not well understood. A pot experiment was conducted with two winter wheat cultivars (Pubing 143, Zhengyin 1) during the grain-filling period. Net photosynthetic rate (PN) and chlorophyll (Chl) content were significantly less affected by water deficit in Pubing 143 than that in Zhengyin 1, and the variation in both PN and Chl content were more stable in spikes compared to flag leaves. At 18 days after anthesis, stomatal conductance of spikes in Pubing 143 were 28% lower than that of the control, while transpiration rate was 34% lower in Zhengyin 1 under water deficit. We provided the first evidence of amphistomatous stomata on the lemma of winter wheat spikes through scanning electron microscopic observations. The finding of the amphistomatous stomata is an important contribution to stomatal distribution and may help explain how wheat spikes can maintain high photosynthetic rates even under drought conditions.

Response of grain-filling properties and quality of winter wheat to drip irrigation in Xinjiang, China

To provide theoretical basis for the water-saving, high-yield and good quality cultivation techniques of drip-irrigated winter wheat, the wheat cultivar 'Xindong 22' was adopted as the test material, and five irrigation amounts including 3150 (W1), 3900 (W2), 4650 (W3), 5400 (W4) and 0 (CK) m3·hm-2 were adopted to investigate effects of drip irrigation amount on grain filling dynamics and quality traits in 2012-2013 and 2013-2014 wheat growing seasons in Xinjiang. Results indicated that the grain-filling dynamics of drip-irrigated winter wheat in different treatments presented the "S" shape curve, and accorded with the Logistic model with high fitting degree. The fast increase period of wheat grain-filling was measured at 12-20 days after anthesis. The maximum filling rate (Vm) increased at first and decreased later with the increase of drip irrigation amount, and was obtained in the treatment W3 in the two seasons, which was 2.16 g·d -1and 2.59 g·d -1, respectively. With the increase in drip irrigation amount, the bulk mass, protein content, flour extraction rate, wet gluten content, dough stability time, degree of softening, dough extension resis-tance and draw ratio of the drip-irrigated wheat firstly increased and decreased later, and the maxima of these indexes were measured in W3. However, the water absorption rate and extensibility of dough initially decreased and then increased, and the minimum was obtained in the treatment of W3. The sedimentation value increased gradually and the dough development time decreased progressively. Treatment W3 had the highest grain yield of 8913 kg·hm-2 in 2013 and 8602 kg·hm-2 in 2014, which was 25.0%, 14.8%, 4.4%, 35.6% and 12.4%, 2.8%, 1.1%, 33.0% higher than the treatments of W1, W2, W4 and CK in 2013 and 2014, respectively. In conclusion, drip irrigation of 4650 m3·hm-2 during the whole growing season of winter wheat could realize the target of high-yield and good quality in local natural condition.

Response to water deficit in glume of wheat: expression profiling by microarray analysis

To investigate the drought response in wheat spike, we evaluated variations in gene expression in the early grain-filling period at 6 days after anthesis by Affymetrix Wheat Genome Array. 566 differentially expressed probe sets were identified. 477 genes were upregulated (FC ≥ 2.0) and 89 (FC ≤ 0.5) were downregulated under water deficit. Most upregulated genes were involved in signal transduction, metabolism, and transcription. We identified signaling proteins, transcription factors, and abiotic stress-related genes among the upregulated genes. Three important genes were located at the center of the phenylalanine metabolism. This result indicates that phenylalanine metabolism and biosynthesis of flavonoids derived from carbohydrate metabolism play pivotal roles during drought-resistance response in wheat spike. Nine upregulated genes were selected for confirming gene chip results at 0, 3, 6, 10, 15, 20, and 25 DAA by real-time PCR. This study provided insights into the molecular mechanism underlying wheat spike responses against drought.

The relationships between carbon isotope discrimination and photosynthesis and rice yield under shading

The measurement of carbon isotope discrimination (∆) provides an integrated insight into theresponse of plants to environmental change. To investigate the potential use of ∆ for identifyingshade tolerance in rice, five rice varieties were selected and artificially shaded (53% lightreduction) during the grain-filling period in 2010 and 2011, in Sichuan, China. Shadingtreatment had a significant influence on the ∆ of rice organs, resulting in clear increases in the ∆of stems plus sheaths (∆Sm), rice grains (∆Gm) and rice flour (∆Fm) at maturity, but a reductionin the ∆ of leaves (∆Lg) at the grain-filling stage. The relationships between ∆ and leafphotosynthetic and chlorophyll fluorescence characteristics and grain yield showed a closedependence on plant organs and light regimes. Under shading treatment, photosynthetic ratewas negatively associated with ∆Gm and the ∆ of stems plus sheaths at the grain-filling stage(∆Sg), whereas ∆Sm was significantly (PPSII (PSII), photochemical quenching (qP) and non-photochemical quenching (NPQ).Moreover, grain filling and grain weight under shading treatment were positively correlatedwith ∆Sg, but negatively related to ∆Sm in 2011. In contrast, a significantly (Passociation between grain weight and ∆Lg was observed in 2010. It was found that lower valuesof ∆Lg, ∆Sm and ∆Gm in rice indicated better light-harvesting and light-use capability and alsohigher grain filling and grain weight of rice.

Maize kernel weight responses to sowing date-associated variation in weather conditions

Variation in weather conditions during grain filling has substantial effects on maize kernel weight (KW). The objective of this work was to characterize variation in KW with sowing date-associated weather conditions and examine the relationship between KW, grain filling parameters, and weather factors. Maize was sown on eight sowing dates (SD) at 15–20-day intervals from mid-March to mid-July during 2012 and 2013 in the North China Plain. With sowing date delay, KW increased initially and later declined, and the greatest KW was obtained at SD6 in both years. The increased KW at SD6 was attributed mainly to kernel growth rate (Gmean), and effective grain-filling period (P). Variations in temperature and radiation were the primary factors that influenced KW and grain-filling parameters. When the effective cumulative temperature (AT) and radiation (Ra) during grain filling were 950°C and 1005.4MJm−2, respectively, P and KW were greatest. High temperatures (daily maximum temperature [Tmax]>30.2°C) during grain filling under early sowing conditions, or low temperatures (daily minimum temperature [Tmin]<20.7°C) under late sowing conditions combined with high diurnal temperature range (Tmax-min>7.1°C) decreased kernel growth rate and ultimately final KW. When sowing was performed from May 25 through June 27, higher KW and yield of maize were obtained. We conclude that variations in environmental conditions (temperature and radiation) during grain filling markedly affect growth rate and duration of grain filling and eventually affect kernel weight and yield of maize.

The effects of nitrogen uptake before and after heading on grain protein content and the occurrence of basal- and back-white grains in rice (Oryza sativa L.)

Chalky rice (Oryza sativa L.) grains are induced by high temperature during the grain-filling period. Plant nitrogen status also affects the occurrence of basal- and back-white grains (BBWG). The objective of this study was to elucidate the relations between nitrogen availability per spikelet during the grain-filling period (NGF) and each of the percentage of BBWG and grain protein content (GPC). We further compared the effect of the components of NGF determined before heading (NBH) and after heading (NAH) on BBWG and GPC. We grew the rice cultivar ‘Koshihikari’ in pots in 2012 and 2013, and top-dressed nitrogen at the panicle formation and heading stages, under two (2012) or three (2013) temperature regimes during the grain-filling period. GPC was explained well by NGF, but BBWG was not. BBWG was best explained in a multiple-regression equation by mean air temperature after heading and by NBH and NAH. The partial correlation coefficients for NBH were 1.6 and 3.0 times those for NAH in 2012 and 2013, respectively. On the other hand, in a multiple-regression equation for GPC, the partial correlation coefficients for NBH were 0.91 and 0.71 times those for NAH in 2012 and 2013, respectively. These results suggest that rice grains are most sensitive to plant nitrogen status before heading for BBWG but after heading for GPC, and that there is an optimal timing for nitrogen top-dressing that would maximize the reduction in BBWG per unit increment of GPC.

Uncertainty in canola phenology modelling induced by cultivar parameterization and its impact on simulated yield

Accurate modelling of crop phenology is essential for evaluating how crops respond to future environmental and management changes. However, cultivar parameters are often estimated based on limited data and using a trial-and-error method, leading to uncertainties in simulated phenology and subsequent crop yield. In this paper we evaluated the ability of the APSIM-Canola model to simulate canola phenology and the impact of uncertainty in phenology modelling on simulated grain yield.We constrained the APSIM-Canola model to experimental data to derive the parameters controlling canola flowering and maturity dates using a Bayesian optimisation method, by minimising the RMSE between simulated and recorded pre- and post-flowering durations. The dataset covered observations for 10 cultivars, 35 site-years, with maximum of seven sowing dates each year from four canola growing regions in China.Our results demonstrated that multiple combinations of parameters could lead to the same simulation accuracy of canola phenology (equifinality) due to insufficient information/understanding to separate vernalisation and photoperiod sensitive phases. This could potentially lead to incorrect cultivar characterisation and wrong yield simulations. Our results further showed that the critical photoperiod below which canola phenological development slows down is likely to be 20h instead of the 16.3h currently used in the APSIM model. With this correction, the model was able to accurately simulate canola phenology across environments, and the impact of equifinality on simulated yield was small. Cultivar differences in terms of phenology could be accurately described by only three parameters in APSIM, i.e., vernalisation sensitivity, photoperiod sensitivity, and thermal time required for grain-filling period.

Modelling and genetic dissection of staygreen under heat stress.

Key message Staygreen traits are associated with heat tolerance in bread wheat. QTL for staygreen and related traits were identified across the genome co-located with agronomic and physiological traits associated to plant performance under heat stress. Plant chlorophyll retention—staygreen—is considered a valuable trait under heat stress. Five experiments with the Seri/Babax wheat mapping population were sown in Mexico under hot-irrigated environments. Normalized difference vegetation index (NDVI) during plant growth was measured regularly and modelled to capture the dynamics of plant greenness decay, including staygreen (Stg) at physiological maturity which was estimated by regression of NDVI during grainfilling. The rate of senescence, the percentage of plant greenness decay, and the area under the curve were also estimated based on NDVI measurements. While Stg and the best fitted curve were highly environment dependent, both traits showed strong (positive for Stg) correlations with yield, grainfilling rates, and extended grainfilling periods, while associations with kernel number and kernel weight were weak. Stg expression was largely dependent on rate of senescence which was related to the pattern of the greenness decay curve and the initial NDVI. QTL analyses revealed a total of 44 loci across environments linked to Stg and related traits, distributed across the genome, with the strongest and most repeatable effects detected on chromosomes 1B, 2A, 2B, 4A, 4B and 7D. Of these, some were common with regions controlling phenology but independent regions were also identified. The co-location of QTL for Stg and performance traits in this study confirms that the staygreen phenotype is a useful trait for productivity enhancement in hot-irrigated environments.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-016-2757-4) contains supplementary material, which is available to authorized users.

Effect of silicon on grain yield of rice under cadmium-stress

Many publications indicated various beneficial effects of the addition of silicon (Si) in soil on the physiology of rice plants. The gene responsible for the Si-uptake in rice, low Si-influx 1 (Lsi1), was identified and cloned for this study. The photosynthetic rate (Pn), grain yield, and resistance to Cadmium (Cd)-stress of the wild-type (WT) and Lsi1-transgenic Lemont rice lines under Cd-stress were examined in an attempt to better understand the mechanism associated with the Si-addition, Cd-stress, and rice physiology. Si-fertilization significantly reduced the Cd-content in rice under Cd-stress. The effect was most significant in the Lsi1-overexpression transgenic Lemont rice (Lsi1-OE line) under high Cd-stress. Conversely, Cd in soil lowered the Si-uptake of the plants indicating a significant interaction between the two elements. During the grain-filling period, Cd-stress greatly reduced the chlorophyll content and Pn of the rice resulting in a diminished grain output. However, Lsi1-OE line with a higher chlorophyll content and Pn than either WT or Lsi1-RNAi transgenic Lemont rice (Lsi1-RNAi line) maintained a high photo-assimilate transportation for high yield potential. At harvest, Lsi1-OE line contained more Si and less Cd than WT, whereas the Lsi1-RNAi line showed an opposite result. In general, Cd-stress reduced, while Si-fertilization significantly increased, the grain yield on rice. However, no significant difference on the grain yields existed between WT and Lsi1-RNAi line. This might be due to a compensation effect generated by Lsi1-RNAi line. It appeared that Si in the soil, as well as the enhancing or inhibiting Lsi1 expression and the resistance to Cd-toxicity of the plants, could significantly affect the rice yield making alternations on these factors a plausible approach for production improvement.

Characteristics of the grain-filling process and starch accumulation of high-yield common buckwheat ‘cv. Fengtian 1’ and tartary buckwheat ‘cv. Jingqiao 2’

High-yield common buckwheat ‘cv. Fengtian 1’ (FT1) and tartary buckwheat ‘cv. Jingqiao 2’ (JQ2) were selected to investigate the characteristics of the grain-filling process and starch accumulation of high-yield buckwheat. FT1 had an average yield that was 43.0% higher than that of the control ‘cv. Tongliaobendixiaoli’ (TLBDXL) in two growing seasons, while JQ2 had an average yield that was 27.3% higher than that of the control ‘cv. Chuanqiao 2’ (CQ2). The Richards equation was utilized to evaluate the grain-filling process of buckwheat. Both FT1 and JQ2 showed higher values of initial growth power and final grain weight and longer linear increase phase, compared with respective control. These values suggest that the higher initial increasing rate and the longer active growth period during grain filling play important roles to increase buckwheat yield. Similar patterns of starch, amylose and amylopectin accumulation were detected in common buckwheat, leading to similar concentration of each constituent at maturity in FT1 and TLBDXL. Tartary buckwheat showed an increasing accumulation pattern of amylose in developing seeds, which differed from that of starch and amylopectin. This pattern led to a significant difference of the concentrations of amylose and amylopectin at maturity between JQ2 and CQ2, the mechanisms of which remained unclear. Nevertheless, both FT1 and JQ2 showed increased starch, amylose, and amylopectin accumulation during the physiological maturity of grains. The results suggest that prolonging the active grain-filling period to increase carbohydrate partitioning from source to seed sink can be an effective strategy to improve buckwheat yield.

Respuestas correlacionadas para el rendimiento en la selección de híbridos de maices precoces subtropicales.

With the aim of designing selection criteria to identify the described genotypes with short vegetative period and longer grain-filling period without increasing the total growing cycle of the genotype. The information generated during 1995 at six locations in the subtropical region of Mexico was used. A serie of six experiments, integrated with a group of subtropical hybrids derived from a diallel between a group of elite tropical and subtropical inbred lines from CIMMYT, were evaluated in collaboration with INIFAP and the seed industry. In the combined analysis of six environments, early hybrids with a grain yield of 8.0 t/ha were identified; those hybrids were 14 days earlier to reach physiological maturity than the control check which yielded 7.4 t/ha. The genotypes with lower yields showed a short grain filling period compared to the vegetative period. Correlations among yield vs. days to physiological maturity, grain-filling period and the index calculated by dividing the between grain-filling /days to physiological maturity were 0.47, 0.53 and 0.41, respectively. This indicate an intermediate association between these traits; also, a high correlation values were observed between grain yield vs. plant and ear hight. The correlation between yield vs. days to silk and days to pollen shed were not significant. General combining ability (GCA) and specific combining ability (SCA) effects were significant for yield, days to silk and grain-filling period. Sufficient variation was observed to allow for the selection of genotypes with short vegetative periods and longer grain filling periods. The effects of GCA and SCA for grain-filling period suggest that this trait is an important criterion to select parents for producing short season hybrids.

RELATIONSHIP BETWEEN GRAIN YIELD AND YIELD COMPONENTS OF THE ETHIOPIAN DURUM WHEAT GENOTYPES AT VARIOUS GROWTH STAGES

&lt;p&gt;Water availability is the main constraint limiting durum wheat production in many parts of the world. Knowledge of the phenotypic and genotypic relationship between grain yield and its various components is an important step in developing selection criteria under water stress environment. To assess the usefulness of some of the agronomic traits as indicators of grain yield, eighteen durum wheat genotypes were evaluated under water stress treatments induced at three growth stage together with a well-watered control in plastic pots during 2006/07 growing season. The water stress treatments used were continuous stress from tillering to physiological maturity (M1), stress from anthesis to physiological maturity (M2) and stress from grain-filling stage to physiological maturity (M3). The water levels were maintained in the range of 35-50% field capacity in the stress treatments while above 75% in the control treatment. Harvest index and grain-filling rate were positively associated with grain yield under all water regimes while number of kernels per spike and aboveground biomass yield were correlated with grain yield under water stress conditions only. Path analysis revealed that grain-filling rate and grain-filling period had high positive direct effect on grain yield under continuous stress from tillering to crop maturity and well-watered conditions. Aboveground biomass and harvest index had positive direct effect on grain yield under stress treatment from flowering through crop maturity. Similarly, grain filling rate and harvest index had positive direct effect on yield while biomass yield and kernel number per spike had high indirect positive effect on grain yield through grain filling rate and harvest index under water stress from grain filling to crop maturity. Therefore, selection for higher grain filling rate and longer grain filling period under optimal moisture supply to severe stress environment whereas higher biomass yield, harvest index and kernels per spike are expected to improve the yield of durum wheat under moderate water stressed environments.&lt;/p&gt;

Cultivar differences in the grain protein accumulation ability in rice (Oryza sativa L.)

The demand for rice grain protein content (GPC) differs in different regions of the world. Despite large differences in GPC among cultivars, evaluation of the effects of genotype on GPC is difficult because GPC is influenced not only by cultivar traits (such as nitrogen uptake ability, sink size and heading date) but also by the environment. We hypothesized that grain protein accumulation ability (GPA) also affects GPC. The objective of this study was to clarify the differences in GPA among six lodging-tolerant, high-yielding Japanese cultivars: Bekoaoba, Habataki, Takanari, Hokuriku193, Momiroman, and Akenohoshi. To produce a wide variation in nitrogen availability per unit sink capacity (Nav), we used nitrogen topdressing at heading and spikelet-thinning treatment. In each cultivar, we found a logarithmic relation between GPC and Nav: GPC=A×Ln(Nav)+B, where A is the regression coefficient and B is a constant. A highly significant difference in regression coefficients among cultivars was found (P<0.01). The regression coefficient was considered to be a measure of GPA; it varied from 0.969 in Bekoaoba to 1.820 in Takanari. This relation suggests that GPC is determined by Nav and GPA and that the environment affects GPC through Nav. GPA is a good criterion for evaluation of the effects of genotype on GPC. Nitrogen harvest index was highly significantly explained by multiple regression with GPA and the ratio of sink capacity to total dry matter production as independent variables, suggesting the influence of GPA on plant nitrogen dynamics during the grain-filling period. Therefore, it would be useful to determine the cultivars’ GPA values for optimizing nitrogen management.