Superior Grains Research Articles

The Effect of Plastic-Covered Ridge and Furrow Planting on the Grain Filling and Hormonal Changes of Winter Wheat

Although plastic-covered ridge and furrow planting (RF) has been reported to produce substantial increases in the grain weight of winter wheat, the underlying mechanism is not yet understood. The present study used two cultivars, Xinong 538 and Zhoumai 18, and RF and traditional flatten planting (TF, control) with the objective of investigating the effect of RF on wheat grain filling and the possible relationship of hormonal changes in the wheat grains under RF to grain filling. The results indicated that RF significantly increased the grain weight, although the effects on grain filling were different: RF significantly increased the grain-filling rate and grain weight of inferior grains, whereas RF had no significant effect on grain-filling rate and grain weight of superior grains. The final grain weight of inferior grains under RF was 39.1 and 50.7 mg for Xinong 538 and Zhoumai 18, respectively, 3.6 and 3.4 mg higher than the values under TF. However, the final grain weight of superior grains under RF was only 0.6 and 0.8 mg higher than under TF for Xinong 538 and Zhoumai 18, respectively. RF significantly decreased the ethylene and gibberellic acid content in the inferior grains and increased the indole-3-acetic acid, abscisic acid and zeatin + zeatin riboside content in the inferior grains; however, no significant difference between RF and TF was observed for the hormonal content in the superior grains. Based on these results, we concluded that RF significantly modulated hormonal changes in the inferior grains and, thus, affected the grain filling and grain weight of the inferior grains; in contrast, RF had no significant effect on grain filling, grain weight and hormonal changes in the superior wheat grains.

Differences of Starch Granules in Grains from Different Spikelet Positions and Their Correlation with Grain Weight in Winter Wheat

The purpose of this study was to reveal the differences in development and size-distribution of starch granules in endosperm of wheat grains in different grain positions and spikelet positions. The endosperm cell size, and the number, volume and surface area distribution of starch granules in mature caryopsis, as well as the changes of starch granule number during endosperm development, were studied using wheat cultivar Jimai 20 grown in the field. The results showed that the development of starch granule was closely related with grain position and spikelet position. In the same spikelet position, starch grains formed 4–5 d earlier in superior grains (the first and the second grains) than in inferior grains (the third and the fourth grains).At the same grain position, starch granules developed first in the grains of the middle spikelets, and then in grains of upper and lower spikelets. The amount of starch granules was the highest in the middle spikelet grains all the time. The lower spikelet grains had the least starch granules at the beginning of grain filling, however, the number of starch granules increased gradually and surpassed that of the upper spikelet grains as caryopsis matured. Correlation coefficients between grain weight and starch granule amount became more significant with grain filling, which reached 0.88 ** (large starch granule) and 0.78 ** (small starch granule) at mature stage. Correlation coefficients between grain weight and large starch granule amount were higher than 0.96 ** , and had no difference among different spikelet positions. Correlation coefficients between grain weight and small starch granule amount were higher than 0.93 ** , and had a trend of upperlowermiddle in different spikelet positions. The trend of size distribution was BL-typeBS-typeA-type. There were more BS-type granules in superior grains than in inferior grains. The number of BS-type granules increased with the spikelet position rising, whereas the number of BL-type granules showed a reverse trend. The size distribution of starch granules had similar changes to volume and surface area. The formation and size distribution of starch granules were affectedsignificantly by grain position and spikelet position, and inferior grains had the potential of increasing grain weight through increasing the quantity of starch granules.

Genome-Wide Analysis of 24-nt siRNAs Dynamic Variations during Rice Superior and Inferior Grain Filling

24 nt-siRNAs are the most abundant small interfering RNAs in rice grains aside from microRNAs. To investigate the roles that 24 nt-siRNAs played in the poor grain filling of rice inferior grains, dynamic variations of 24 nt-siRNAs in inferior grains were compared with those of superior grains by using small RNA deep sequencing technology. The results showed that 24 nt-siRNAs derived from multiple regions of rice genome, and the maintenance of the two strands of 24 nt-siRNA duplex was a non-random process. The amounts of 24 nt-siRNAs declined with the process of grain filling in both superior and inferior grains, but 24 nt-siRNAs in inferior grains was much higher than that of superior grains in each period we sampled. Bioinformatics prediction indicated that 24 nt-siRNAs targeted on more genes involved in most of the known KEGG rice pathways, such as the starch and sucrose biosynthesis pathway. Combined with digital gene expression profiling of target genes, 24 nt-siRNAs mapped on the antisense strands of exons were specifically investigated, but the abundance of 24 nt-siRNAs did not show negative correlations with their corresponding target genes. The results indicated that 24 nt-siRNAs were not involved in down-regulation of target genes. The potential biological meanings for this inconsistency were probably the results of methylation directed gene expression activation, or competition for small RNA stability methylation.

Effects of conservation tillage on grain filling and hormonal changes in wheat under simulated rainfall conditions

The objective of this study was to investigate the effect of conservation tillage (CT) on wheat grain filling under different precipitation levels and the relationship with endogenous hormonal changes. In the present study, CT was compared to traditional bare soil tillage (BT) under different precipitation conditions simulated during the wheat growth stage, and the resulting hormonal changes in the grains were measured. The results indicated that the effect of CT on wheat grain filling is significantly related to precipitation. At the 220-mm rainfall level, CT significantly promoted grain filling of the superior and inferior grains. CT also significantly promoted the grain filling of inferior grains at 260-mm rainfall yet had no significant effect on filling of the superior grains. In contrast, CT had no significant effect on the grain-filling rates and grain weight of superior and inferior grains at the 300-mm rainfall level. At 220- and 260-mm rainfall, CT significantly increased the indole-3-acetic acid (IAA) and zeatin (Z)+zeatin riboside (ZR) contents and decreased the abscisic acid (ABA), ethylene (ETH), and gibberellic acid (GA) contents in the inferior grains, whereas CT only had these effects in the superior grains at the 220-mm rainfall level. The IAA, ABA, and Z+ZR contents in the grains were positively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates; the ETH concentration was negatively and significantly correlated with the maximum grain weight and the maximum and mean grain-filling rates. In addition, both precipitation and CT significantly increased the soil moisture during the grain-filling stage. Based on these results, we conclude that the CT treatment significantly increased the soil moisture, thus regulating the grain filling of wheat, and that this process was significantly related to the balance of hormones in the grains.

Influence of Planting Methods on Grain-filling Properties of Super Rice

To explore grain-filling properties of high-yielding rice under different planting methods,we studied the grain-filling processes of superior and inferior grains of two super rice cultivars(Huaidao 9 and III you 98) with Richards equation W=A/(1+Be-Kt)1/N and three planting methods,i.e.precision artificial transplanting with dry nursery middle and strong seedlings(ATR),mechanical transplanting with small seedlings(MTR) and direct seeding(DSR).The results were as follows:(1) The super rice yields under different planting methods were significantly different,ATR was the highest,followed by the MTR,and the lowest was the DSR.Compared with ATR and MTR,the 1000-grain weight and seed-setting rate of DSR were significantly lower,but the changes between ATR and MTR were different due to different types of cultivar.(2) The grain-filling processes of superior and inferior grains of super rice under different planting methods were obviously asynchronous type.The time reaching the maximum grain-filling rate(Tmax) of superior grains was early,maximum grain-filling rate(GRmax),mean grain-filling rate(GRmean),the final weight of a kernel(A) and initial grain-filling potential(R0) were significantly greater than those of inferior grains.However,the active grain-filling period(D) and effective grain-filling time(T99) of the superior grains were significantly less than those of inferior grains.(3) Compared with ATR and MTR,the GRmax and GRmean of superior grains of DSR were significantly lower,Tmax was obviously delayed,D and T99 significantly increased.The GRmax and GRmean of inferior grains of MTR were the highest,and ATR was slightly lower than DSR.For Tmax,DSR was the earliest,MTR was the second,and the latest was ATR.D and T99 reduced in order for ATR,MTR,and DSR.(4) For grain-filling characteristics of different stages,the maximum of mean grain-filling rate and contribution rate was present at the middle stage,and the contribution rates of superior and inferior grains were up to 60.53% and 50.78%,respectively.The grain-filling days,mean grain-filling rate and contribution rate of the early,middle and late stages among different planting methods were different due to grain positions.(5) 1000-grain weight was positively correlated with maximum grain-filling rate,mean grain-filling rate and active grain-filling period of superior and inferior grains,and the correlations with maximum grain-filling rate and mean grain-filling rate of inferior grains were significant.Seed-setting rate had in a degree of positive or negative correlations with the grain-filling parameters of the superior and inferior grains,however,except the active grain-filling period of superior grains,all of the correlations were not significant.The results suggested that planting methods have significant influence on grain-filling properties of super rice.Although the grain-filling processes are all asynchronous types,the grain-filling parameters such as maximum grain-filling rate and the time reaching the maximum grain-filling rate of superior and inferior grains have great difference among different planting methods.It would play an important role in improving 1000-grain weight and grain-filling rate,especially the grain-filling rate of inferior grains under the conditions maintaining the final weight of a kernel and seed-setting rate stable.

Effects of Asymmetric Warming on Key Enzyme Activities of Starch Synthesis in Superior and Inferior Grains of Winter Wheat under FATI Facility

Using Yangmai 11 as the material,we investigated the impacts of asymmetric warming on the key enzyme activities in starch synthesis in winter-wheat superior and inferior grains based on field study with FATI (Free Air Temperature Increased) facility.The results showed that the activities of sucrose synthase (SS),ADP-glucose pyrophosphorylase (AGPase),and starch branching enzyme(SBE) were higher in superior grains than in inferior grains,and also higher in the daytime than at night.In the control during the grain filling stage,the average activities of SS,AGPase,and SBE were 72.9%,111.4%,and 7.8% higher in superior grains than in inferior grains.In superior grains,the SS activities in all-day warming,daytime warming and nighttime warming treatments were 8.4-31.2% higher than those in the ambient control in the daytime,and 11.1-20.3% higher than those in the control at night.In inferior grains,the increased percentages were 9.7-20.3% in the daytime and 6.1-32.0% at night.In inferior grains,the AGPase activities were elevated significantly compared to the control with 54.2-124.4% in the daytime and 20.7-99.3% at night.The SBE activities were also higher in the warming treatments than in the control with the increase of 3.9-12.1% in the daytime and 1.0-7.6% at night.Besides,the correlations existed between the activities of AGPase and SBE and the 1000-grain weight were positive and significant.This result indicated that elevation of AGPase and SBE activities plays an important role in the enhancement of 1000-grain weight.

Effects of ADP-Glucose Pyrophosphorylase Activity on Sterility and Develop-ment of Grain in K, V, and T-Cytoplasmic Male

Cytoplasmic male-sterile (CMS) lines, especially K (Aegilops kotchyi), V (Aegilops ventricosa), and T (Triticum timopheevi) types of cytoplasms, are of high value in heterosis utilization in wheat (Triticum aestivum L.). The sterile mechanisms of these CMS types have been focused in hybrid wheat research. As a key and rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGPase) is considered to play an important role in the sterility of CMS lines. For gaining an insight into the physiological basis of the sterility in CMS lines of wheat, the activities of AGPase in leaves, young spikes, and grains were measured in K, V, and T types of isogenic CMS lines (Ji 5418 background) at different growth stages, and compared with those of their maintainer line. The dynamic accumulations of starch, amylose, and amylopectin were also investigated in both superior (the first and the second grains in a spikelet) and inferior (grains except for the first and the second grains in a spikelet) grains. In young spikes, the AGPase activities of the three CMS lines were significantly higher (F=133.81, P＜0.0001) with the differences of 9.33-27.94 μmol g^(-1) FW h^(-1) at floret primordium stage, and significantly lower (F=13.97-75.20, P＜0.0001) by 4.27-7.44 μmol g^(-1) FW h^(-1) at tetrad stage as compared with the maintainer line. From floret primordium to tetrad stage, the CMS lines had continuously higher level of AGPase activities in leaves than the maintainer line, with the differences ranged from 7.39 to 80.77 μmol g^(-1) FW h^(-1) (F=135.76-5454.28, P＜0.0001). Compared with the maintainer line, the three CMS lines all presented lower accumulations (P＜0.05) of starch, amylose and amylopectin in grain. The starch content and AGPase activity in superior grains were significantly higher than those in inferior grains for CMS lines. The dynamic accumulations of starch in superior and inferior grains fitted Logistic equations, and positively correlated with the starch accumulation rate (r=0.4460-0.7150, P=0.0004-0.0487). The AGPase activity in leaves had an insignificantly negative correlation with net photosynthetic rate. In conclusion, the male sterility is probably in relation to the insufficiency of energy in leaves and young pikes at floret primordium stage resulting from the high AGPase activity, and the low accumulation of starch in pollens at tetrad stage caused by low AGPase activity in young spikes. The sterile cytoplasm has a negative effect on AGPase activity, resulting in decreases of ADPG level and starch accumulation in grains. Besides, the negative effect of AGPase activity on net photosynthetic rate in flag leaves may result in unfilled grains in CMS lines.

Sink strength in relation to growth of superior and inferior grains within a wheat spike

SUMMARYStarch is a major component of wheat grain and, to a great extent, determines the grain weight. Starch accumulation in wheat (Triticum aestivum L.) is closely associated with sink strength. Four winter wheat cultivars, Lumai 21 and Jimai 20 (compact-spike cultivars) and Shannong 1391 and Shannong 12 (loose-spike cultivars) were grown to evaluate the amylose and amylopectin accumulation in both superior and inferior grains (higher and lower individual grain weight, respectively) and the relationship between starch accumulation and sink strength. In general, superior grains showed a higher starch accumulation rate, endosperm cell number and activity of enzymes including sucrose synthase (SS), uridine diphosphorate glucose pyrophosphorylase (UGPP), adenosine diphosphorate glucose pyrophosphorylase (AGPP), soluble starch synthase (SSS) and granule-bound starch synthase (GBSS), and subsequently produced higher starch accumulation and grain weight than inferior grains. Greater differences in starch accumulation and grain weight were found between the two classes of grains for compact-spike cultivars than between those for loose-spike cultivars. These results suggest that the grain sink strength, determined by endosperm cell number and the activity of synthesis-related enzymes, is closely associated with starch accumulation in superior and inferior grains on a wheat spike.

Starch granules size distribution in superior and inferior grains of wheat is related to enzyme activities and their gene expressions during grain filling

Mature wheat endosperm contains A-, B-, C-type starch granules, and each class has unique physiochemical properties which determine the quality of starch. The dynamics of the starch granule size distribution, activities of starch synthases and expression of starch synthase encoding genes were studied in superior and inferior grains during grain filling. Compared with inferior grains, superior grains showed higher grain weight, contents of starch, amylose and amylopectin. The formation of A-, B-, C-type starch granules initiated at 4, 8, 20 DAF, respectively, and was well consistent with the temporally change patterns of starch synthase activities and relative gene expression levels. For instance, activities of soluble and granule-bound starch synthases (designated SSS and GBSS) peaked at 20 and 24 DAF. Genes encoding isoforms of starch synthases expressed at different grain filling periods. In addition, SS I was generally expressed over the grain filling stage; the SS II and SS III were expressed over the early and mid grain filling stage, and the GBSS I was expressed during the mid to late grain filling stage. In addition, the time-course changes in activities of starch synthases and expression of starch synthase encoding genes explained well the dynamics of the starch granule size distribution.

The effect of sucrose and abscisic acid interaction on sucrose synthase and its relationship to grain filling of rice (Oryza sativa L.)

Rice grain filling is a process of conversion of sucrose into starch catalysed by a series of enzymes. Sucrose synthase (SUS) is considered as a key enzyme regulating this process. This study investigated the possible roles of sucrose and abscisic acid (ABA) in mediating the activity and expression of SUS protein of grains during grain filling in rice (Oryza sativa). Field-grown rice plants and detached cultured panicles were used as experimental materials. Several treatments, including spikelet thinning, leaf cutting, and applications of different concentrations of exogenous sucrose and ABA, were imposed during grain filling. A higher SUS activity was found in superior grains than in inferior grains in the earlier stage of grain filling, which was significantly and closely related to a higher grain filling rate and starch accumulation. An increase in sucrose concentration in grains as a result of different treatments increased both SUS activity and SUS protein expression in grains. An increase in ABA concentration gave similar results. Furthermore, effects of interactions between sucrose and ABA on the activity and expression of SUS protein in grains were also found. It was suggested that sucrose- and ABA-mediated rice grain filling is largely due to an increase in SUS activity and SUS protein expression.

Causes of Poor Grain Plumpness of Two-Line Hybrids and Their Relationships to the Contents of Hormones in the Rice Grain

Abstract This study was designed to elucidate the grain filling characteristics and the causes of poor grain plumpness of some two-line hybrid rice combinations and their hormonal mechanism. Six varieties, including three two-line hybrid rice combinations, that show differences in seed-setting and grain filling, were used. And the contents of starch, sucrose, zeatin (Z) + zeatin riboside (ZR), indole-3-acetic acid (IAA), and abscisic acid (ABA), the ethylene evolution rate, activities of sucrose synthase (SuSase) and starch synthase (StSase) in grains, the seed-setting and grain filling rate were investigated. The correlations amongst these were analyzed. The results showed that the poor grain filling of two-line hybrids was mainly attributed to the higher unfilled grain rate and the lower filling degree of inferior grains. During the early and mid grain filling periods, the sucrose content in inferior grains was greater than that in superior grains for the combinations with poor grain filling, indicating that the substrate concentration was not the principal factor for their slow grain filling and poor grain plumpness of the inferior grains of two-line hybrids. Z + ZR, IAA, and ABA in superior grains were obviously greater than those in inferior grains at early grain filling stage. The maximum and mean contents of Z + ZR, IAA, and ABA were positively very significantly correlated with the maximum and mean grain-filling rate, filling degree, and grain weight. The evolution rate of ethylene was greater in inferior grains than in superior grains and greater for the combinations with poor grain plumpness than those with good grain plumpness at the early or mid filling stages. The evolution rate of ethylene was negatively and significantly correlated with the grain filling rate, the grain filling degree, and the grain weight. Spraying ethephon (ethylene-releasing agent) at the early grain filling stage increased the evolution rate of ethylene, reduced the ABA content and activities of SuSase and StSase, and decreased the grain filling degree and the grain weight. The results were reversed when cobatous nitrate (an inhibitor of ethylene synthesis) was applied. The results suggested that the hormones and their balance play a role in the regulation of grain filling and enzymatic activities, and the poor grain filling is attributed to the low contents of Z + ZR, IAA, and ABA, and the high evolution rate of ethylene in the inferior grains of some two-line hybrid rice combinations. The results suggested that hormones play important roles in the grain filling of some two-line hybrid rice combinations, and their filling degree can be improved by regulating the hormonal contents.

The Differences in Grain Weight and Quality Within a Rice (Oryza sativa L.) Panicle as Affected by Panicle Type and Source‐sink Relation

AbstractThe effects of panicle type and source‐sink relation on the variation in grain weight (GW) and quality within a panicle were investigated using four japonica (Oryza sativa L.) varieties differing in grain density and two source‐sink adjusting treatments. There were significant differences in GW and filling grain percentage (FGP) among superior and inferior grains for compact‐panicle varieties (Xiushui 994 and Xiushui 63), while not for loose‐panicle ones (Xiushui 11 and Chunjiang 15). The floret‐removal treatment significantly improved the development of inferior florets and reduced the differences in FGP and GW between superior and inferior grains for the compact‐panicle variety, while leaf‐deleting treatment reduced FGP and GW of both superior and inferior grains. For the loose‐panicle varieties, the two treatments had little effect. The difference in chalky grain percentage (CGP) and amylose content (AC) between the two kinds of florets was larger in compact‐panicle varieties than in loose‐panicle ones. Both floret‐removal and leaf‐deleting treatments caused the changes in CGP and AC of superior or inferior grains for compact‐panicle varieties, but not for loose‐panicle ones. The difference in starch content (SC) between superior and inferior grains was much larger for Xiushui 994 than for Xiushui 11, and the two varieties differed in the response of SC to the change of source‐sink relation. The differences in AGP‐glucose pyrophosphorylase (ADPG‐Ppase), starch branching enzyme (SBE) and soluble starch synthase (SSS) activities between the two kinds of grains were basically same for the two varieties, with superior being higher than inferior ones at early filling stage and smaller at later stage. In floret‐removal treatment, the activities of ADPG‐PPase, SSS, and SBE in superior grains of Xiushui 994 decreased at early filling stage and increased at middle or later stages. Meanwhile, the activities of SSS and SBE in both kinds of grains at early filling stage, and of ADPG‐PPase and granule‐bound starch synthase (GBSS) in inferior grains over the whole stage were increased. In leaf‐deleting treatment, the activities of ADPG‐PPase and SBE at early filling stage and GBSS at later filling stage were reduced in superior grains, while SSS activity at middle filling stage and SBE activity at later stage were increased.

Hormonal changes are related to the poor grain filling in the inferior spikelets of rice cultivated under non-flooded and mulched condition

Non-flooded plastic mulching cultivation (PM) of rice can save much irrigation but usually exhibits a poor grain filling and low grain weight when compared to traditional flooding cultivation (TF). This study measured the variations of plant hormones during grain filling and investigated whether they were related to the grain-filling problem under mulching in a field experiment. Hormonal levels in the grains and the grain development of both superior (early flowered) and inferior spikelets (later flowered) were monitored continuously during the grain filling period. The contents of indole-3-acetic acid (IAA), zeatin riboside (ZR) and abscisic acid (ABA) were higher in superior grains than in inferior ones at early grain-filling stage. For individual spikelets, the peaks of IAA and ZR contents appeared just before the peak grain-filling rate but the peak ABA content matched it. The earlier flowered superior spikelets did not show much difference in grain filling characteristics and hormonal changes under the two cultivation treatments. Distinctively with the inferior spikelets in a panicle, PM led to lower grain weight, higher grain-filling rate at early stage and shorter active grain-filling period than the TF. PM also resulted in less IAA and ZR but more ABA contents in the grains than TF at early and middle grain filling stages in these inferior spikelets. Peaks of these hormone contents in the PM inferior grains usually appeared earlier and also disappeared more quickly than those in TF inferior grains. When exogenous IAA was applied to plants at the initial grain-filling stage, IAA and ZR were increased and ABA was reduced in the inferior grains. The treatment prolonged the active grain-filing period and reduced the peak grain-filling rate of inferior grains, similarly as the case with TF. As a result, IAA spraying enhanced the weight of PM inferior grains but reduced that of TF ones. Exogenous ABA spraying led to the opposite effects to those of IAA. The results suggest that the shortened grain-filling period in the inferior grains under PM is related to the increased ABA and reduced IAA and ZR in the grains. Regulation of the ratio of ABA to IAA in grains could potentially increase the weight of inferior grains under the water-saving cultivation with film mulching.

Abscisic acid and ethylene interact in wheat grains in response to soil drying during grain filling

Grain filling is an intensive transportation process regulated by soil drying and plant hormones. This study investigated how the interaction between abscisic acid (ABA) and ethylene is involved in mediating the effects of soil drying on grain filling in wheat (Triticum aestivum). Two wheat cultivars, cv. Yangmai 6 and cv. Yangmai 11, were field-grown, and three irrigation treatments, well-watered, moderately soil-dried (MD) and severely soil-dried (SD), were imposed from 9 d post anthesis until maturity. A higher ABA concentration and lower concentrations of ethylene and 1-aminocylopropane-1-carboxylic acid (ACC) were found in superior grains (within a spike, those grains that were filled earlier and reached a greater size) than in inferior grains (within a spike, those grains that were filled later and were smaller), and were associated with a higher filling rate in the superior grains. An increase in ABA concentration and reductions in ethylene and ACC concentrations in grains under MD conditions increased the grain-filling rate, whereas much higher ethylene, ACC and ABA concentrations under SD conditions reduced the grain-filling rate. Application of chemical regulators gave similar results. The results did not differ between the two cultivars. The grain-filling rate in wheat is mediated by the balance between ABA and ethylene in the grains, and an increase in the ratio of ABA to ethylene increases the grain-filling rate.

Changes in the uptake function of the rice root to nitrogen, phosphorus and potassium under brown planthopper, Nilaparvata lugens (Stål) (Homoptera: Delphacidae) and pesticide stresses, and effect of pesticides on rice-grain filling in field

Effects of different BPH densities and pesticide applications on the uptake of nitrogen (N), phosphorus (P) and potassium (K), by the root system were investigated using a hydroponics culture. Infestations of 30 BPH had a significant effect on the uptake function of the rice root. A high dose (225 g.a.i. ha −1) of jingganmycin reduced the uptake of P and K significantly, but there was little effect on the uptake of N. At a low dose (15 g.a.i. ha −1) of imidacloprid the uptake of P and K was promoted significantly. There was also a significant interaction effect between BPH density and pesticide treatments. Field experiment during rice-grain filling showed that both low and high doses of imidacloprid reduced active growth stage (Δ t) and maximum (K) of grain growth of superior grains significantly and a high dose reduced K and growth rate of inferior grains significantly. All doses of imidacloprid and jingganmycin significantly reduced accumulative grain weight during Δ t. A high dose of imidacloprid reduced the growth rate of inferior grains significantly.

Activities of key enzymes for starch synthesis in relation to growth of superior and inferior grains on winter wheat (Triticum aestivum L.) spike

Weight of individual grains is a major yield component in wheat. The non-uniform distribution of single grain weight on a wheat spike is assumed to be closely associated with starch synthesis in grains. The present study was undertaken to determine if the enzymes involved in starch synthesis cause the differences in single grain weight between superior and inferior grains on a wheat spike. Using two high-yield winter wheat (Triticum aestivum L.) varieties differing in grain weight and three nitrogen rates for one variety, the contents of amylose and amylopectin, and activities of enzymes involved in starch synthesis in both superior and inferior grains were investigated during the entire period of grain filling. Superior grains showed generally higher starch accumulation rates and activities of enzymes including SS (sucrose synthase), UDPGPPase (UDP-glucose pyrophosphorylase), ADPGPPase (ADP-glucose pyrophosphorylase), SSS (soluble starch synthase) and GBSS (starch granule bound starch synthase) and subsequently produced much higher single grain weight than inferior grains. Nitrogen increased enzyme activities and starch accumulation rates, and thus improved individual grain weight, especially for inferior grains. The SS, ADPGPPase and SSS were significantly correlated to amylopectin accumulation, while SS, ADPGPPase, SSS and GBSS were significantly correlated to amylose accumulation. This infers that SS, ADPGPPase and starch synthase play key roles in regulating starch accumulation and grain weight in superior and inferior grains on a wheat spike.

Effect of irradiance on the partitioning of assimilated carbon during the early phase of grain filling in rice.

Low irradiance in the early phase of grain filling in rice often results in a low grain yield, but its effects on the partitioning of previously or recently assimilated carbon within the plant or panicle have not been seriously examined. The objective of this study was to demonstrate the effect of shading during the different stages in the early phase of grain filling on the partitioning of previously or recently assimilated carbon among constituent organs and into superior and inferior spikelets of the panicle in rice (Oryza sativa L. 'Sasanishiki') plants using 13C as a tracer. Plants were grown either under low (shading) or moderate (non-shading) irradiance (120 and 800 micromol quantum m(-2) s(-1)) for 3 or 4 d before or after the 13CO2 feeding at heading, full-heading or milky stages during the early phase of grain filling. Four days after the 13CO2 feeding, the proportion of labelled (previously assimilated) carbon partitioned into the panicle was 17% higher in plants grown under low irradiance compared with plants grown under moderate irradiance at the full-heading stage (7-11 d after heading), while the proportion partitioned into the culm was 13% lower. The light treatments for 3 d were conducted before the 13CO2 feeding and partitioning of the labelled (recently-assimilated) carbon into spikelets was examined 6 h after feeding. The amount of labelled carbon partitioned into the spikelets of the secondary branch (inferior grains) in the plants grown under low irradiance was only 31% when compared with plants grown under moderate irradiance at the full-heading stage, although the partitioning of labelled carbon into the apical spikelets of the primary branch (superior grains) was not affected by the light treatments. These results clearly indicate that preferential partitioning of assimilated carbon into the panicle occurs under low irradiance at around 7-11 d after heading and that the priority of superior spikelets for assimilated carbon intensifies. This phenomenon is thought to be an important strategy for such rice cultivars as used in this study to achieve a certain proportion of ripened grains even under light limited conditions.

Introgression of diverse genes for resistance to rusts into an improved wheat variety, Kalyansona

Breeding for resistance to the three rusts of wheat usually requires incorporation of genetically independent factors conferring resistance to each rust. Linked resistance genes in some alien translocation stocks permit concurrent transference of resistance for more than one rust. Alien derived resistances, however, are often reported to be associated with reduced yield and other undesirable characters. In our experience, backcross breeding when given a limited number of backcrosses (3–6) and with suitable selection procedures has resulted in lines giving yields higher or comparable to the recurrent wheat parent Kalyansona and resistance to one, two or all three rusts without any adverse effects. Some of the rust resistant derivatives also show resistance to Neovossia indica (Karnal bunt). The derivatives thus developed when used as parents in a breeding programme have produced several improved cultivars with high yields, superior grains and diversity for resistance to rust pathogens. One of the cultivars, named ‘Vaishali’ (DL784-3), has been officially released for cultivation in the country.

Influence of Dietary Fibers on Performance and Fermentation Characteristics of Gut Contents from Growing Chicks

Four experiments were conducted to evaluate the inclusion of fiber from various sources and of various particle sizes in both semipurified and corn-soybean meal diets fed to chicks. Growth rate and feed efficiency were the performance measurements tested. In Experiment 1, 8-day-old New Hampshire × Columbian female chicks were fed polyethylene (PE) and alfalfa cell walls (ACW) of varying particle sizes (<300 μm, 300 to 600 μm, and 600 to 1200 μm), incorporated into diets at the 8% level. A 0% fiber and an 8% solka floc treatment were used as controls. Consumption of ACW resulted in higher (P<.05) growth rates (6.5 vs. 5.4 g/day) and better (P<.05) feed efficiencies (.46 vs. .41) compared with chicks fed PE, regardless of particle size. In Experiment 2, two levels (4 and 8%) of pectin, lignin and xylose:gum arabic (50:50 mix), were tested using 8-day-old chicks of the same strain. Both levels of lignin and xylose:gum arabic (50:50 mix) resulted in superior grains compared to chicks fed control diets, while 8% pectin resulted in lower (P<.05) growth rates (3.3 g/day) than controls (5.2 g/day). Feed efficiencies followed the same pattern as growth rate. In Experiments 3 and 4, 1-day-old chicks (Experiment 3) and 8-day-old chicks (Experiment 4) of the Hubbard strain were fed two levels (5 and 10%) of gum arabic, xylose, and lignin substituted for corn in practical-type diets. Controls included 0% fiber and 5% arenaceous flour treatments. In Experiment 3, chicks fed both levels of xylose and lignin gained better (P<.05) than controls, whereas those fed 5% gum arabic performed poorer (12.3 g/day for controls; 9.6 g/day for gum arabic). Feed efficiency results showed similar trends. Growth rates of 8-day-old chicks fed 10% gum arabic and 10% xylose were lower (P<.05) than controls (28.4 and 30.7 vs. 31.6 g/day, respectively). Only chicks fed 10% gum arabic had lower feed efficiencies than controls. Cecal and large intestinal contents from chicks fed 10% xylose contained the highest concentration of volatile fatty acids (VFA) (83.5 and 79.9 μmoles/ml). Chicks fed lignin had the least cecal VFA (60.8 μmoles/ml) while chicks fed lignin and those fed the control diet had the least large intestinal VFA. Acetate was the predominan t VFA while propionate was present in the lowest molar concentration.

Observations on Damages to Rice Crops Caused by Wind Storm

1) Crop damages were investigated in two varieties of rice plant "Tozan No. 59" and "Chukyo-Asahi" by comparing two plots, one caught in the storm and one guarded by a wind break. No injury due to the storm was found in the latter plot. 2) In "Tozan No. 59", the plants attacked lodged entirely and the nutrient translocation into kernels was checked remarkably for a few days, resulting the inferior grains remaining on panicles as blasted or chalky kernels, while the superior grains continuing their deverlopment barely into deformed or milk-white kernels, with the exception of some vigorous grains among them maturing into ordinary kernels. The yield of rice was 70 percent of that in the guarded plot. 3) In "Chukyo-Asahi", the leaves were splitted into two or three parts and the hulls were slightly chafed in the plot caught in storm. Accordingly, the kernel development was somewhat checked, and chalky, deformed, milk-white and brown kernels increased. The yield of rice was about 10 percent lower than that in the guarded plot.