Duration Of Grain Research Articles

Designing high‐yielding wheat ideotypes for a changing climate

AbstractGlobal warming is characterized by shifts in weather patterns and increases in climatic variability and extreme events. New wheat cultivars will be required for a rapidly changing environment, putting severe pressure on breeders who must select for climate conditions which can only be predicted with a great degree of uncertainty. To assist breeders to identify key wheat traits for improvements under climate change, wheat ideotypes can be designed and tested in silico using a wheat simulation model for a wide range of future climate scenarios predicted by global climate models. A wheat ideotype is represented by a set of cultivar parameters in a model, which could be optimized for best wheat performance under projected climate change. As an example, high‐yielding wheat ideotypes were designed at two contrasting European sites for the 2050 (A1B) climate scenario. Simulations showed that wheat yield potential can be substantially increased for new ideotypes compared with current wheat varieties under climate change. The main factors contributing to yield increase were improvement in light conversion efficiency, extended duration of grain filling resulting in a higher harvest index, and optimal phenology.

Deep Roots are Pivotal for Regulating Post‐Anthesis Leaf Senescence in Wheat (Triticum aestivum L.)

AbstractRoot activity plays a dominant role in grain filling in cereal crops. However, the importance of deep roots for regulating post‐anthesis leaf senescence is not clearly understood in wheat (Triticum aestivum L.). In this study, we used 32P tracing to estimate the difference in wheat root activity at soil depths of 30 and 70 cm and the root restriction method to investigate the effects of vertical distribution of deep roots on leaf senescence, with non‐restricted plants as controls. Recovery of radioactive 32P indicated that deep roots had significantly higher activity than upper roots in wheat. Root restriction at a soil depth of 50 cm caused significant decreases in the activities of superoxide dismutase (EC 1.15.1.1), peroxidase (EC 1.11.1.7), catalase (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) at 16 days after anthesis and thereafter resulting in an increase in malondialdehyde. As a result, chlorophyll levels and net photosynthesis decreased. Ultimately, the root‐restricted wheat produced a significantly lower grain yield than the non‐restricted controls. These data suggest that deep roots are pivotal for regulating plant senescence, duration of grain filling, and yield formation.

Modelling fungal sink competitiveness with grains for assimilates in wheat infected by a biotrophic pathogen.

Experiments have shown that biotrophic fungi divert assimilates for their growth. However, no attempt has been made either to account for this additional sink or to predict to what extent it competes with both grain filling and plant reserve metabolism for carbon. Fungal sink competitiveness with grains was quantified by a mixed experimental-modelling approach based on winter wheat infected by Puccinia triticina. One week after anthesis, plants grown under controlled conditions were inoculated with varying loads. Sporulation was recorded while plants underwent varying degrees of shading, ensuring a range of both fungal sink and host source levels. Inoculation load significantly increased both sporulating area and rate. Shading significantly affected net assimilation, reserve mobilization and sporulating area, but not grain filling or sporulation rates. An existing carbon partitioning (source-sink) model for wheat during the grain filling period was then enhanced, in which two parameters characterize every sink: carriage capacity and substrate affinity. Fungal sink competitiveness with host sources and sinks was modelled by representing spore production as another sink in diseased wheat during grain filling. Data from the experiment were fitted to the model to provide the fungal sink parameters. Fungal carriage capacity was 0·56 ± 0·01 µg dry matter °Cd(-1) per lesion, much less than grain filling capacity, even in highly infected plants; however, fungal sporulation had a competitive priority for assimilates over grain filling. Simulation with virtual crops accounted for the importance of the relative contribution of photosynthesis loss, anticipated reserve depletion and spore production when light level and disease severity vary. The grain filling rate was less reduced than photosynthesis; however, over the long term, yield loss could double because the earlier reserve depletion observed here would shorten the duration of grain filling. Source-sink modelling holds the promise of accounting for plant-pathogen interactions over time under fluctuating climatic/lighting conditions in a robust way.

Effect of the complexity of sunflower growing regions on the genetic progress achieved by breeding programs

Sunflower (Helianthus annuus L.) breeding programs typically target heterogeneous regions, where large genotype × environment interactions (GEI) complicate genetic progress. Some understanding of the underlying factors, nature and repeatability of GEIs can help to accommodate their effects. This review summarizes the findings of a series of studies conducted in Argentina with the goals of understanding the effect of GEIs on sunflower yield progress and design breeding strategies aimed at impacting on future rates of genetic advance. Pattern analyses revealed that the central and northern subregions are different mega-environments (ME), which suggests that yield gains in the northern ME would have been reduced if selection had been done in central environments and vice versa. Photoperiod and minimum temperature during the reproductive phases are the main environmental factors underlying the observed GEIs. Genetic gain analyses indicated clear and continuous improvements in oil yield due to plant breeding during 25 years and confirmed the prediction about lack of yield gains under the northern ME from selection done in central environments. The central ME showed the highest and most consistent genetic progress, probably because it concentrates most breeding programs and shows the highest repeatability. Breeding progressed to merge the best combinations of two original hybrid groups, reducing the original maturity range within MEs and concentrating on different maturity types among MEs. The model of correlated response to selection indicated that dividing the central- north region of Argentina in central and northern MEs and exploiting specific adaptation would result in faster genetic progress. In the central ME, there is scope to replace years with locations at no costs in heritability. In the northern subregion, trials should be conducted over at least four years. Late planting dates in a central location associated positively with the northern environments in terms of genotypic discrimination; which constitutes an opportunity for indirect selection for the northern ME. Physiological models served to establish the importance of attributes and processes affecting crop performance in the post-anthesis phase in determining the observed genotypeby- planting time interaction. The diameter of the empty center and canopy stay green were found to be efficient secondary indicators related to seed set and duration of grain filling, respectively - indicators that can be used to improve the efficiency of selection for specific adaptation to late plantings and to the northern ME.

Spring barley performances in the Pannonian zone

Environmental conditions in the Pannonian zone can be characterized with moderate high temperature and partially water deficit during grain filling of spring barley, although low temperature and water deficit are possible also in period till anthesis. This study was conducted to evaluate the variation of the duration of the period from emergence to anthesis (VP), duration of grain filling period (GFP), plant height (PH), spikes number m-2 (SN), grains number spike-1 (GN), thousand grains weight (GW) and yield (YIL) in spring two-rowed barley in conditions of the Pannonian zone. All three factors; genotype, environment and the interaction GxY affected the studied traits. Average VP was 777 GDD, GFP 782 GDD, PH 78 cm, SN 523, GN 28.2, GW 43.2 g and YIL 6.26 t ha-1. Variation across varieties was higher than across growing seasons. Heritability varied from 0.66 for YIL to 0.94 for VP and GFP. This study confirmed that a sufficiently large genetic variability must be base for selecting appropriate varieties for the Pannonian zone conditions. In order to determine high yielding and quality barley extensive research in relation to breeding, variety choice for production and growing practice must be done.

Physicochemical control of durum wheat grain filling and glutenin polymer assembly under different temperature regimes

Durum wheat is grown in the Mediterranean area where drought and high temperature frequently prevail and impact grain texture, composition and yield. The purpose of this work was to examine the effect of high temperature on grain development and final composition according to the timing of exposure. High temperature (up to 27.5 °C) was applied either during the linear grain filling or drying phases or during whole grain development. The dynamics of grain dry mass, water, glutenin polymers, and protein bodies during grain development were determined. Irrespective of high temperature timing, the arrest of grain filling was observed at 45.9% grain moisture content. At that point, starch granules included in endosperm cells reached their physical packing limit, limiting further deposits. HT applied before physiological maturity shortened the duration of grain filling and resulted in a significant increase in grain protein concentration and in the proportion of vitreous grain. Late formation of sodium dodecyl sulfate (SDS)-insoluble glutenin polymers below 32% grain moisture content was also favored. The ability of wheat storage protein to form a viscoelastic matrix embedding starch granules at the beginning of grain desiccation is proposed to be mandatory for gaining vitreous grains and a high proportion of SDS-insoluble glutenin polymers.

Response of Ethiopian durum wheat genotypes to water deficit induced at various growth stages

Understanding the effect of water stress on yield and its components is the essential step in developing of high yielding and stable genotypes. Substantial reduction in grain yield can be caused by water deficit depending on the intensity, duration and the developmental stage at which water stress occurred. An experiment was conducted in the lathouse at Sinana Agricultural Research Center in 2006/2007 to evaluate the effect of water deficit on grain yield and yield components of eighteen durum wheat genotypes induced at different growth stages. Grain yield and other agronomic traits of all genotypes were significantly reduced and the reduction was much more pronounced under stress induced from tillering to crop maturity. Grain yield per plant was reduced by 72, 37 and 17.1% due to stress induced at tillering, flowering and grain-filling stages as compared to the well-watered treatment, respectively. Kilinto and Gerardo were found to be stable and drought tolerant genotypes whereas S17B and Boohai were highly susceptible. The most drought tolerant genotypes were found to maintain relatively high levels of kernel numbers per spike and hundred-kernel weight. Mean kernel weight was associated to the duration of grain filling and grain filling rates and these traits contributed to a greater yield under water stress conditions.

Effect of genotype, environment and agronomic management on β-glucan concentration of naked barley grain intended for health food use

(1,3:1,4)-β- d-Glucan is an important bioactive that contributes to the ability of barley foods to help prevent type-2 diabetes. Realisation of these benefits requires understanding of genotype and environment effects on β-glucan concentration and how this variation affects biological activity of barley foods. Field experiments showed genetic variation in β-glucan concentration (3.0–7.0 g/100 g DM), but also considerable variation between environments. β-Glucan concentrations were lower in the wet summer of 2007 than 2006 or 2009; and slightly less in the dry summer of 2006 than 2009. β-Glucan was not diluted by higher grain yields. The role of β-glucan as an assimilate buffer adds complexity to interpreting the effects of environment during grain filling. Autumn sowing and fungicide increased the duration of grain filling, decreased β-glucan concentration but increased environmental stability; possibly due to lower demand for assimilate buffering. Lodging and foliar disease decreased β-glucan concentration, by decreasing assimilate supply leading to remobilisation of carbohydrate from β-glucan, so that fungicide increased β-glucan in some disease-susceptible accessions. Sequential harvesting starting at GS 91 suggested an optimum harvest window for maximum β-glucan concentration. The variability in β-glucan reported here between genotypes and environments was sufficient to affect control of post-prandial blood glucose in healthy volunteers.

Evaluation of the STICS crop growth model with maize cultivar parameters calibrated for Eastern Canada

Crop growth models are great tools for studying and anticipating the future impacts of rising demands for agricultural production while satisfying constraints with respect to product safety, the landscape, and the environment. Before crop growth models can be applied, however, they need to be calibrated and evaluated for cultivars representative of a given ecozone. This study presents an evaluation of the STICS crop growth model using maize cultivar parameters calibrated for the Mixedwood Plains ecozone in Eastern Canada. In the study area, which extends from southwestern Quebec to southern Ontario, the available crop heat units (CHU, in CHU index) for plant growth vary between 2,500 and 3,500 CHU. One cultivar was first calibrated in the STICS model using leaf area index (LAI) and yield data from Ottawa, Ontario. The model gave good predictions of LAI, biomass, and yield for the cultivar CanMaisNE in the range of 2,500–2,900 CHU. The root mean square error of the predictions was 28.1% for LAI, 17.5% for biomass, and 10.1% for yield. A second cultivar, CanMaisSE, was defined for the higher CHU range (2,900–3,300 CHU). CanMaisSE had the same crop and cultivar parameters as CanMaisNE except for the duration of grain filling, which was increased by 6–7 days to account for the longer growing season in the area with 3,300 CHU. Good predictions of LAI, biomass, and yield were obtained for CanMaisSE, with root mean square error values of 30.6%, 25.2%, and 16.1%, respectively. Defining these two generic maize cultivars was sufficient to estimate biomass, yield, and LAI over the entire study area. This work is the first calibration and performance evaluation of the STICS crop model for maize in North America. Moreover, these new grain maize cultivars, adapted to a shorter growing season, open new opportunities for using STICS in northern countries.

Do barley and wheat (bread and durum) differ in grain weight stability through seasons and water–nitrogen treatments in a Mediterranean location?

Under Mediterranean environments, farmers usually prefer to sow barley rather than wheat as it is generally believed that barley yields more under stressful conditions. As terminal stresses such as high temperature and water are common constraints in Mediterranean regions, higher grain weight stability may confer a clear advantage in order to maintain higher yields. The objective of the present study was to compare the stability in terms of grain weight and its components for barley, bread wheat, and durum wheat, exploring a wide range of nitrogen and water availabilities in experiments conducted in a Mediterranean region. Grain weight ranged from 23.8 to 47.7 mg grain −1, being higher for durum wheat than barley and bread wheat. Durum wheat presented higher variability both in maximum grain filling rate and duration of grain filling period than bread wheat or barley. The three species responded similarly in terms of grain nitrogen content to changes in the environmental conditions explored. It is concluded that in terms of grain weight barley is as stable as bread wheat. However, durum wheat presented a lower stability than barley and bread wheat.

Genotypic diversity in sorghum inbred lines for grain-filling patterns and other related agronomic traits

Opportunities for genetic improvement on specific traits require information on available diversity, together with knowledge on heritability estimates and possible trade-off relations among traits. Sixty-five sorghum inbred lines were evaluated for grain filling and other agronomic traits during 2008 and 29 re-evaluated in 2009. Time to anthesis, final grain weight (GW), grain growth rate, duration of grain filling, maximum water content, grain desiccation rate, moisture concentration at physiological maturity, plant height, panicle length, grain number per plant and final yield per plant were measured both years. Results highlighted the available variability for grain-filling patterns in sorghum, and genotypic differences (P < 0.05) for all traits were evident. Final GW variation (16–44 mg grain–1 in 2008, and 20–40 mg grain–1 in 2009) was achieved through different combinations of rate (3.27–9.78 mg degree-days grain–1 10−2) and duration of grain filling (413–853 degree-days). Calculated heritability for grain-filling traits ranged from 0.43 to 0.95, showing GW and maximum water content had the highest values. Grain number showed consistent negative associations with grain growth rate but not with GW due to grain-filling duration variability. This suggests selecting longer grain filling can increase GW (and yield) without negative trade-off relations with grain number.

Rice root growth and physiological responses to SRI water management and implications for crop productivity

This paper reports on several research findings on rice root responses, in terms of growth and physiology, manifested when applying System of Rice Intensification water management principles under semi-field and field conditions, in conjunction with variations in plant density and microbial density in the soil. The research aimed to learn about causal relationships, if any, between rice root and shoot growth at different growth stages of the rice plant’s development and their cumulative effect on yield, which is affected by both biotic and abiotic influences. It was seen that greater root length density and a higher rate of root activity affected the yield-contributing parameters in all of the trials, whether conducted under semi-field or field conditions. At the same time, both root parameters were significantly affected by the water regime, soil microbial density, and planting pattern, the three main factors considered. The most important finding observed under semi-field conditions was that enhanced microbial density in the soil improved the sink capacity of the rice plants under all water regimes evaluated. Positive correlations were found between the chlorophyll content of the flag leaf and the duration of grain filling, between the chlorophyll content of plants’ lower leaves and their roots’ oxidizing activity rate, and the roots’ oxidizing activity rate at later growth stage and the available soil nitrogen. These relationships can significantly improve rice plants’ physiological efficiency and hence grain yield, provided that soil nutrients are not a limiting factor and when source–sink demand is maintained simultaneously. To realize the highest crop yield per hectare, both planting pattern and spacing are factors that need to be optimized. This paper in its conclusion considers the relevance of exploiting roots’ potential for plasticity to enhance crop productivity in the context of impending water constraints and climate-change effects.

Characterization of wheat-barley introgression lines for drought tolerance

The safety of wheat production in Hungary requires the propagation of droughttolerant cultivars because of the regular occurrence of water deficiency. Hybridization between related species makes it possible to transfer desirable traits from one species to another. Introgression lines developed from wheat/barley hybrids were investigated together with the parental wheat and barley cultivars to determine how the added barley chromosome (segment) influences drought tolerance in wheat. The plants were grown in the field at the UP Georgikon Faculty, Keszthely. Sowing and harvest were done by hand. Half the length of the 12 m rows was covered with a plastic rain shelter on 2 nd April (EC: 30–31) to protect the plants from rain, resulting in a 163 mm difference in water supplies between the control (not covered) and stressed (covered) treatments. Data were obtained for anthesis and maturity date, plant height, root/shoot ratio, leaf water potential, grain yield and grain yield components. The plants adapted to water deficiency by increasing the root/shoot ratio and decreasing the water potential and the duration of grain filling. The grain yield was reduced by 12%, averaged over the genotypes, mainly due to a decrease in the number of spikes per plant.

Trait dissection of maize kernel weight: Towards integrating hierarchical scales using a plant growth approach

Maize (Zea mays L.) yield is a function of the number harvested kernels per unit land area and the individual kernel weight (KW). Kernel weight and its development show a wide variability due to the genotype, the environment, the crop management, and all possible interactions. Commercial maize hybrids differ markedly in the patterns (rate and duration of kernel growth) behind differences in final KW. The same can be observed when public or elite proprietary maize inbred lines are analyzed. To progress in our understanding of KW variability, we reviewed and discussed current knowledge for analyzing kernel growth as an integrated system, modulated by processes linking different levels of organization (the different kernel tissues, the whole kernel, the plant, the canopy). Ideas on how to integrate this knowledge towards the development of a multi-hierarchical scale framework for predicting KW under different growth environments are currently needed, as they have high relevance for dissecting the genetic basis of kernel growth and maize yield definition at the canopy level. At the kernel and tissue level, we highlight the need of focusing and studying traits like assimilate movement into developing kernels, endosperm cell division, endosperm cell death, kernel internal homeostasis and kernel water relations. These specific processes need to be connected affecting the rate or duration of grain filling at the whole kernel level for studying kernel size variability. At the plant and canopy levels, the dynamic response of both kernel number and potential KW to plant growth around flowering appears critical for understanding KW variations, as maize final KW is highly associated with the potential KW determined during the first stages of grain filling. Focusing on the period around flowering in this species is important for yield improvement through both yield components, kernel number and size. At present it seems that maize potential yield can only be improved by modifying the sink capacity established at the end of the lag phase and increasing the source strength during grain filling so as to fulfill this potential.

The response of rate and duration of grain filling to long-term selection for yield in Italian durum wheats

Genetic advance in durum wheat (Triticum turgidum subsp. durum) grain yield in Italy has been achieved by bringing forward flowering time, achieving a larger number of grains per unit area, and altering the pattern of senescence. The performance, in the absence of any moisture stress, of a set of 6 Italian durum wheat cultivars released over the past 100 years was compared under 4 environments and 2 nitrogen rates, to ascertain whether the changes brought about by selection for yield have also indirectly affected the rate and duration of grain filling. Grain filling lasted 35–36 days in all cultivars except ‘Ichnusa’ (39 days), although modern cultivars flowered earlier than older ones. The lack of any breeding effect on grain-filling duration also meant that the later old cultivars were not negatively affected by the higher ambient temperatures during their grain filling. The maximum rate of grain filling ranged from 2.4 to 3.3 mg/day and showed a highly significant negative correlation with the year of cultivar release (r = –0.91*). The variation in grain weight, significant but not correlated with the year of release, was associated with the rate of grain filling, which was in turn related to the grain number per unit area. A compensating variability still exists among modern Italian cultivars in both grain number and grain-filling rate, which demonstrates that durum wheat grain yield can be increased while also preserving high grain weights.

Evaluation of Grain Filling Rate and Duration in Bread and Durum Wheat, under Heat Stress after Anthesis

AbstractBread and durum wheat genotypes were submitted to heat stress during the grain filling period, and relationships between grain weight and accumulated time from anthesis until maturity, using days after anthesis and growing degree days, were described by cubic polynomials. Maximum grain weight and the duration and rate of grain filling were estimated from the fitted curves. It was found that bread and durum wheat exposure to high temperatures significantly decreased grain weight and hastens physiological maturity (shortening the grain filling period). High temperatures significantly affected the rate (on a growing degree day basis) and duration (on Julian day units) of grain filling. The grain filling rate, on a thermal time basis, was positively associated with the final grain weight and the estimated maximum grain weight. The duration of grain filling does not appear to be a limiting factor for genotype grain weight stability, being mainly fixed by temperature. Grain weight of the controlled plants was positively correlated with the final and maximum grain weight of heat stressed plants. It was concluded that a high grain filling rate and a high potential grain weight are major traits that can be useful to improve heat tolerance of Triticum under Mediterranean environments.

Grain filling parameters in high-yielding ns wheat cultivars

Grain yield of wheat is dependent on grain weight, which is the result of grain filling duration and rate. The study was undertaken to examine the relation between grain weight and rate and duration of grain filling in five high-yielding NS wheat cultivars. Stepwise multivariate analysis of nonlinear regression estimated grain filling parameters was used to examine cultivar differences in grain filling. On the basis of three-year average, the highest grain dry weight had cultivar Renesansa, and the lightest grains were measured for cultivar Evropa 90. Stepwise multivariate analysis indicated that all three nonlinear regression estimated parameters (grain weight, rate and duration of grain filling) were equally important in characterizing the grain filling curves of the cultivars studied, although sequence of their significance varied in different years, which is probably caused by different environmental conditions in three years of experiment.

Post-anthesis dry matter and nitrogen dynamics in durum wheat as affected by nitrogen supply and soil water availability

Durum wheat ( Triticum durum Desf.) is commonly grown in dryland conditions, where environmental stress during grain filling can limit productivity and increase the dependency on stored assimilate. We investigated current assimilation and remobilization of dry matter and nitrogen during grain filling in N fertilized and unfertilized durum wheat subjected to different levels of water deficit during grain filling. Two durum wheat varieties, Appio and Creso, were grown in open-air containers with three rates of nitrogen fertilizer (not applied, N0; normal amount, NN; high amount, NH) and four water regimes during grain filling (fully irrigated treatment, FI; low, LWS, moderate, MWS and high water stress, HWS) across 2 years. Grain yield and dry matter and N accumulation and remobilization were positively affected by N availability and negatively by water stress during grain filling. The reduction of grain yield by severe post-anthesis water stress amounted to 27 and 37% for N0 and NN, respectively, and was associated with a decrease in kernel weight. There was also a small negative effect on the number of kernels per spike. Conversely, the duration of grain filling was not modified either by water stress or by nitrogen treatments. Severe water stress also reduced dry matter accumulation and remobilization by 36 and 14% in N0 plants and by 48 and 25% in NH plants. Similarly, N accumulation and N remobilization was reduced by 43% and by 16% in N0 plants and by 51% and by 15% in NH plants. Conversely, low and moderate water stress did not substantially modify the patterns of dry matter and nitrogen deposition in grain. Although remobilization of dry matter and N was less affected by water stress than accumulation, it was not able to counterbalance the reduction of assimilation and consequently it was not able to stabilize grain yield under drought.

Nutritive value of cereals grown in Apulian places

The new EU Common Agricultural Policy by the de-coupling measure provides the same subsidy for any crop which respects good economic and environmental conditions; hence the need to identify crop systems which give a better yield in relation to the soil fertility, climatic conditions and species adaptability. The aim of the study was to evaluate the chemical composition and the nutritive value of cereals such as spelt (cultivar Davide), durum wheat (cultivar Portobello), rye (cultivar Askari) and two cultivars of barley, Dasio and Otis. The cereals were grown in 3 Apulian places: Gravina di Puglia (BA), Monopoli (BA) and Monteroni (LE), very different among each other for the climatic conditions and pedological features of soil (fertility, texture and composition). In vitro gas production was assessed by the Menke and Steingass (1988) technique, checked until 72 h and expressed as ml/g DM. The metabolizable energy (ME; MJ/kg DM) was calculated as: 1.06 + 0.157GP + 0.084CP + 0.22CF - 0.081CA, where GP is 24 h net gas production (ml/g DM), CP, CF and CA are crude protein, fat and ash (% DM), respectively. Data were processed by ANOVA according to a 5 (cereals tested) x 3 (cultivation places) experimental model. Student’s t test was used to compare differences between means. The CP content of all the cereals tested was higher in crops grown in Gravina compared to Monopoli and Monteroni, with particular regards to durum wheat (13.60 vs 10.97 and 10.35, P<0.01), rye (14.27 vs 7.83 and 7.75, P<0.01) and spelt (13.25 vs 12.16, P<0.05; vs 11.87, P<0.01). The CP content of both the cultivars of barley was significantly lower in Monopoli (Dasio: 11.40 vs 13.16 and 12.75, respectively for Gravina and Monteroni, P<0.01; Otis: 8.20 vs 12.61 and 11.34, P<0.01).Temperatures above 30 ºC and dry winds during late Spring may have affected final kernel weight by reducing the duration of grain filling, due to the suppression of current photosynthesis and by inhibition of starch synthesis in the endosperm. Thus, kernels remain thin and show a lower hectolitre weight and a higher CP percentage as a consequence of the greater incidence of the pericarp on the total kernel weight. This is a typical situation that occurs in South Italy areas, due also to the features of the marginal lands. Indeed, the occurrence of a reduced production of starch may be hypothesised since a lower amount of GP was found, especially for barley (Dasio) and rye grown in Gravina, characterised by poor soils. The ME of durum wheat and rye did not differ among places, while barley cultivars displayed a different trend: the ME of the Dasio cultivar grown in Gravina was significantly lower compared to Monopoli and Monteroni (12.23 vs 13.33 and 13.22, P<0.01). On the other hand the ME of the Otis cultivar grown in Gravina (13.26) was similar to that of Monteroni (13.23) but significantly greater compared to Monopoli (12.54, P<0.05). For spelt the best ME was recorded in Gravina (12.36 vs 11.52, P<0.05), despite the hostile conditions of this place. Therefore, it may be assumed that the greater rusticity of this cereal allows a better adaptability to marginal areas and its use as a convenient ingredient for the ruminant diet.

Is barley yield in the UK sink limited?: II. Factors affecting potential grain size

In the absence of serious post-anthesis stress, the potential supply of assimilates for grain filling in barley appears to exceed the storage (sink) capacity of the grains. The sink capacity is a function of the number of grains per unit land area and their potential size. In order to investigate the contribution of pre and early post-anthesis factors in the control of potential grain weight, regression analysis has been used to analyse data from field experiments conducted on winter barley crops cv. Pearl grown at six sites across the UK between 2002 and 2004. Crops were grown under a comparable husbandry regime with a full crop protection, growth regulator and fertilizer programme. The mean grain weight (MGW) varied from 35 to 46 mg at 100% dry matter over 17 site/year combinations. The variation in MGW between site/years was associated with differences in the rate rather than the duration of grain filling. MGW did not relate well to any measure of above ground growth or crop structure at ear emergence (Zadoks GS59). There was a significant positive linear relationship between MGW and the amount of radiation (PAR) intercepted per unit grain number between ear emergence and the start of rapid grain filling ( r 2 = 0.32, P = 0.023), but not over the whole grain filling period. This is consistent with the view that MGW is determined by potential grain size. A multiple regression model comprising five explanatory variables accounted for a much larger proportion of the total variation in MGW ( r 2 = 0.72, P = 0.013) than PAR interception on its own. There were significant positive associations of MGW with post-anthesis radiation use efficiency and PAR intercepted from GS59 to the start of rapid grain growth (RGG), and significant negative associations with the shoot number per plant, mean air temperature from GS39–59 and mean daily rainfall from GS59-RGG. The results suggest that both pre and post-anthesis conditions operate in concert to determine the potential grain weight of barley in temperate climates. The dry weight and water content of grains and ears followed a common pattern during grain growth for all site/years when the percentage moisture content was used as an index to normalise different rates of development. Use of the above data for predicting potential grain weight of barley prior to harvest is discussed.