Effects of exogenous ABA application on post-anthesis dry matter redistribution and grain starch accumulation of winter wheat with different staygreen characteristics

The objective of this study was to investigate whether and how exogenous abscisic acid(ABA)is involved in mediating starch accumulation in the grain and redistribution of carbohydrates during grain filling of two wheat cultivars with different staygreen characteristics.At blooming stage,plants of Wennong 6(a staygreen cultivar)and Jimai 20(control)were sprayed with10 mg L-1abscisic acid(ABA)for 3 days.The application of ABA significantly(P<0.05)increased grain filling rate,starch accumulation rate and content,remobilization of dry matters to kernels,and 1000-grain weight of the two cultivars.Exogenous ABA markedly(P<0.05)increased grain yield at maturity,and Wennong 6 and Jiami 20 showed 14.14%and 4.86%higher compared yield than the control.Dry matter accumulation after anthesis of Wennong 6 was also significantly(P<0.05)influenced by exogenous ABA,whereas that of Jimai 20 was unchanged.Application of ABA increased endogenous zeatin riboside(ZR)content 7 days after anthesis(DAA),and spraying ABA significantly increased endogenous indole-3-acetic acid(IAA)and ABA contents from 7 to 21 DAA and decreased gibberellin(GA3)content at 14 DAA,but increased GA3content from 21 to 35 DAA.The results suggested that increased yield of staygreen was due to greater starch assimilation owing to a higher filling rate and longer grain-filling duration.

Starch Digestibility and Physicochemical and Cooking Properties of Irradiated Rice Grains

This study evaluated the starch digestibility, physicochemical properties and cooking characteristics of polished rice（varieties IRGA417 and IAC202） subjected to the doses of 0（as the control）, 1, 2 and 5 k Gy of gamma radiation. The highest dose decreased the apparent amylose content, peak viscosity, water absorption and volume expansion. Irradiation increased the solid loss by 119% and 187% for IAC202 and IRGA417, respectively, when comparing the higher dose with the control. For IAC202, irradiation decreased the rapidly digestible starch and increased the slowly digestible starch（SDS） and resistant starch（RS）. IRGA417 showed an elevation of SDS and a reduction in RS. And 1 k Gy dose of gamma radiation generated the highest level of RS for both the two varieties and presented the smallest changes in other physicochemical and cooking properties.

Relationship Between Variation in Activities of Key Enzymes Related to Starch Synthesis During Grain Filling Period and Quality of Eating and Cooking in Rice

Four japonica rice varieties with significant differences in quality of eating and cooking were used in the experiment. The varieties showed differences in amylose and amylopectin contents at different grain filling stages, which were attributed to the accumulative speed of starch at different grain filling stages. During grain filling period, the varieties had no difference in the time when the activities of ADPglocose pyrophosphorylase （AGPP） and soluble starch synthesis （SSS） reached a maximum, but had difference in the time when the activity of starch branching enzyme （SBE） reached a maximum, in which the inferior quality varieties were earlier than the high quality ones, and high quality varieties still kept high enzyme activities at the late stage of grain filling. The correlation and correlative degree between AGPP, SSS, SBE and amylose content, amylopectin content, taste meter value, and RVA properties varied with the different stages of grain filling. The correlation between SSS activity and taste meter value was not significant during the whole period of grain filling, but the activities of AGPP and SBE had significant or highly significant correlation with taste meter value. It was helpful for improving quality of eating and cooking of japonica rice to use the materials with low enzyme activity at the early stage of grain filling or high enzyme activity at the late stage as parents.

Effect of Temperature at Grain Filling Stage on Activities of Key Enzymes Related to Starch Synthesis and Grain Quality of Rice

Three japonica rice varieties with different cooking and eating quality were grown at high temperature in the greenhouse and natural field. Effects of temperature at the grain filling stage on these varieties were investigated in terms of the activities of key enzymes related to starch synthesis and cooking and eating quality of rice grain. The high temperature at the grain filling stage increased protein content, and decreased amylose content and taste meter value of rice; inferior grain quality varieties showed a greater magnitude of the increase or decrease than the superior ones. Reaction of rapid visco analyser profiles to the temperature varied with rice varieties. The activities of adenosine diphosphoglucose pyrophosphoryiase （AGPP）, soluble starch synthase （SSS） and starch branching enzyme （SBE） gradually increased to a peak value, and thereafter declined as grain filling progressed. Enzyme activities in different varieties differed in a same filling stage, and also in the time when the enzyme activity reached a maximum. AGPP and SSS were insensitive to the environmental temperature, but SBE was comparatively sensitive to the temperature, and its activity declined when temperature was too high or too low.

Changes in Activities of the Key Enzymes Related to Starch Synthesis in Rice Grains During Grain Filling and Their Relationships with the Filling Rate and Cooking Quality

With 10 rice cultivars (lines) as materials, the changes in activities of adenosine diphosphoglucose pyrophosphorylase(ADPGPase), starch synthase (SSase) and starch branching enzyme (Q-enzyme) in the grains during grain filling, and theirrelationships with the filling rate, gel consistency (GC), alkali spreading value (ASV) and amylose content (AC) werestudied. The results showed that changes in activities of ADPGPase, SSase and Q-enzyme exhibited a single peak duringgrain filling, and the time of the activity peaks for the former two enzymes was earlier than that of the maximum grain-fillingrate (Tmax), and the time reaching the peak for Q-enzyme was synchronous with Tmax. The activities at early grain fillingstage, and the mean and maximum activities of each enzyme during grain filling period were positively and significantly orvery significantly correlated with the mean and maximum grain filling rate and starch content (mg grain-1) in the grains.Activities of ADPGPase at all grain filling stages and those of Q-enzyme at the early and mid filling stages were notsignificantly correlated the cooking quality (GC, ASV and AC). SSase activities at the early filling stage were significantlyand negatively correlated with GC and ASV, and positively correlated with AC. Activities of SSase at mid and late grainfilling stages and Q-enzyme at the late filling stage were significantly and positively correlated with GC and ASV, andnegatively correlated with AC. Spraying zeatin or abscisic acid at early grain filling stage could obviously regulate theactivities of ADPGPase, SSase and Q-enzyme in the grains.

The Effect of Maize Grain Size on the Physicochemical Properties of Isolated Starch, Crude Maize Flour and Nixtamalized Maize Flours

Usually, the maize cob is formed by grains of medium size. However, the extremes have larger or smaller size grains. The objective of this study was to investigate the influence of grain size from the same hybrid on the physicochemical properties of isolated starch, crude maize flours and nixtamalized maize flours. Two hybrids, one from CIMMyT-Mexico called IMIC-254 and one commercial sample from Monsanto (Puma) were studied. The isolated starch granules from small, medium, and large grains exhibit the same size and distribution. The grain size has influence in the determination of cooking and steeping times;small grains reach these parameters faster than medium and large ones. The hardness of the grain size for both hybrids does not showed statistical differences between them. The starch from small, medium and large grains is mainly composed of amylopectin;this result is confirmed by X-ray diffraction and Megazine analysis. The apparent viscosity of the isolated starches of small grains showed statistically significant higher peak values. According to these results, it is possible to use small, medium, and large grains to obtain products with the same physicochemical properties, by adjusting the cooking and steeping times and Ca2+ content.

Methodological impact of starch determination on starch content and ileal digestibility of starch in grain legumes for growing pigs

Background： Grain legumes represent a valuable energy source in pig diets due to their high starch content. The present study was conducted to determine the content and apparent ileal digestibility（AID） of starch in different grain legume cultivars for pigs by means of both a polarimetric and enzymatic method for starch determination.Methods： Three experiments were conducted with six barrows each which were fitted with ileal T-cannulas. In total, 18 diets including six different cultivars of faba beans（Vicia faba L.） and peas（Pisum sativum L.）, five different cultivars of lupins（Lupinus luteus L., Lupinus angustifolius L.）, and one diet with a soybean meal（SBM） were fed.Results： The starch content of faba beans and peas was greater（P ＆lt; 0.05） when determined polarimetrically than enzymatically（438 vs. 345 g/kg dry matter（DM） in faba beans and 509 vs. 390 g/kg DM in peas, respectively）.Considerable lower starch contents were obtained in lupins and SBM, with 82 and 48 g/kg DM（analyzed polarimetrically） and ＆lt;1.1 and 3 g/kg DM（analyzed enzymatically）, respectively. Mean values for contents of neutral detergent fiber（NDF） and acid detergent fiber（ADF） in grain legumes ranged from 111 and 79 g/kg DM in peas to248 and 207 g/kg DM in lupins, respectively. Contents of condensed tannins in the colored flowered faba bean cultivars ranged from 2.1 to 7.4 g/kg DM. The AID of starch was greater（P ＆lt; 0.05） in pea than in faba bean cultivars,and using the polarimetric starch determination method resulted in greater（P ＆lt; 0.05） digestibility values than using enzymatic starch analysis（84 vs. 80% in faba beans and 86 vs. 83% in peas）. Moreover, AID of starch differed（P ＆lt; 0.05）within pea cultivars and starch digestibility in faba beans decreased linearly（P ＆lt; 0.05） as the content of condensed tannins increased. However, there was no relationship between contents of NDF and ADF and AID of starch in pea and faba bean cultivars.Conclusion： Both contents and AID of starch in grain legumes can vary as influenced by the analytical method used for starch determination. Generally, starch digestibility is greater when measured by polarimetric rather than enzymatic methods.

糯小麦“山农糯麦1号”籽粒及淀粉品质分析

为更好地了解糯小麦的品种特性,以山东省第一个审定的高产糯小麦“山农糯麦1号”为材料,研究其籽粒和淀粉特性。结果发现:该品种几乎不含直链淀粉(仅0.1%),较普通小麦具有较高的蛋白质含量(16.4%)和面粉白度(81.2%)。扫描电镜观察淀粉粒度分布不均匀,A型淀粉颗粒较多。快速粘度分析(RVA)测定表明淀粉具有较低的糊化温度,较短的糊化时间,较低的峰值黏度、最终粘度和回生值。加工时面团吸水率明显较高,形成时间大于稳定时间。这些结果将为山农糯麦1号适于用作配粉和加工食品提供参考依据。

淀粉及其改性产品对东鞍山细粒赤铁矿聚团——磁选的影响

针对东鞍山强磁选抛尾存在粒度小于20μm的微细粒铁矿物流失的问题,研究了不同种类淀粉及其改性产品对微细粒赤铁矿的选择性聚团效果,通过团聚—磁选试验确定了适宜的团聚药剂和用量,借助偏光显微镜和红外光谱等手段检测了药剂与赤铁矿和石英作用前后的形貌特征,最后通过研究高分子药剂的作用机理,论述了药剂的选择性和团聚效果。结果表明:在药剂用量为200 g/t时,交联玉米淀粉的选矿指标优于其他几种药剂,团聚药剂的加入能实现微细粒赤铁矿的选择性聚团,使铁精矿回收率提高2.13~3.94个百分点,选矿效率提高2.77~3.46个百分点,但由于赤铁矿被团聚后呈不规则絮状,在较大的聚团中会夹杂少量石英,导致磁选精矿铁品位略微降低。

氮素穗肥对杂交籼稻籽粒灌浆影响及其与淀粉合成关键酶活性间关系

【目的】为明确氮素穗肥对杂交稻籽粒灌浆和淀粉合成关键酶活性的影响。【方法】选用两个直链淀粉含量差异较大的杂交稻品种锦优1319(高直链淀粉)和蓉优702(低直链淀粉),在不同的氮素穗肥处理下(设0、60、90和120 kg/hm^(2)4个纯氮水平,分别用CK、N1、N2、N3表示)研究氮素穗肥水平对籽粒灌浆和淀粉合成关键酶活性的影响。【结果】不同穗肥处理下杂交稻籽粒灌浆特性差异显著,且不同类型品种表现各异,其中氮素穗肥的施用显著降低了稻米的直链淀粉含量。锦优1319的Gmax和Gmean随氮素穗肥水平的变化均表现为N2>CK>N1>N3,而蓉优702则表现为N3>N2>CK>N1;施用氮素穗肥显著增加了花后5~25 d籽粒腺苷二磷酸焦磷酸化酶(ADPG)和淀粉分支酶(DBE)的活性,降低了花后5~15 d籽粒GBSS活性,降低了花后5~25 d籽粒淀粉合成酶(SSS)和SBE活性。【结论】高直链淀粉品种锦优1319籽粒灌浆的最佳氮素穗肥施用量低于低直链淀粉品种蓉优702:其中锦优1319的最佳氮素穗肥施用量为90 kg/hm^(2),蓉优702为120 kg/hm^(2)。施用氮素穗肥显著降低了GBSS、SSS的活性,加之SBE活性下降,DBE活性提高,最终降低稻米直链淀粉含量。本研究条件下,籽粒ADPG活性未对稻米直链淀粉含量产生显著影响。

施磷量对不同耐低磷型水稻品质及淀粉合成酶活性的影响

适宜磷肥用量对水稻品质具有一定影响。为明确施磷量对不同耐低磷型水稻品质及其强、弱势粒淀粉合成相关酶活性的影响,以‘连粳7号’(弱耐低磷)和‘甬优2640’(强耐低磷)为供试水稻品种进行盆栽试验,设置4个磷肥施用量(按P_(2)O_(5)计):0 kg·hm^(-2)(P0)、60 kg·hm^(-2)(P60)、120 kg·hm^(-2)(P120)、180 kg·hm^(-2)(P180),分析不同施磷量下稻米品质与淀粉合成酶活性之间的关系,为高品质稻米栽培提供参考。结果表明:1)与P0相比,增施磷肥改善了稻米品质。随着施磷量增加,糙米率、精米率、整精米率呈先增加后降低趋势,垩白粒率、垩白面积、垩白度、碱消值、直链淀粉含量先降低后增加。‘连粳7号’与‘甬优2640’分别在P120、P60时稻米品质最优,糙米率、精米率和整精米率分别比P0增加19.6%、25.3%、79.7%(‘连粳7号’)与17.8%、23.5%、38.4%(‘甬优2640’);‘甬优2640’稻米品质优于‘连粳7号’。2)与P0相比,增施磷肥提高了水稻籽粒淀粉合成相关酶活性。腺苷二磷酸葡萄糖焦磷酸化酶(AGPase)、可溶性淀粉合成酶(StSase)、蔗糖合成酶(SuSase)、淀粉分支酶(Q-酶)、三磷酸腺苷酶(ATPase)活性随施磷量增加先增加后降低。总体来看,‘连粳7号’与‘甬优2640’分别在P120、P60时淀粉合成相关酶活性最高,灌浆中期强势粒AGPase、StSase活性分别比P0增加18.4%、51.1%(‘连粳7号’)与20.0%、51.5%(‘甬优2640’);‘甬优2640’籽粒酶活性高于‘连粳7号’。3)不同耐低磷型品种淀粉合成相关酶活性与蛋白质含量、直链淀粉含量相关性不同。淀粉合成相关酶显著或极显著影响‘连粳7号’蛋白质含量,对直链淀粉含量影响较小;淀粉合成相关酶活性显著或极显著影响‘甬优2640’直链淀粉含量,对蛋白质含量影响较小。‘连粳7号’与‘甬优2640’分别在P120、P60处理下能够提高强弱势粒中淀粉合成相关酶活性,促进籽粒中淀粉的合成与积累,有利于水稻品质改善。

大小粒型藜麦籽粒表型、灌浆特性及淀粉合成酶活性的差异分析

【目的】籽粒大小是影响藜麦产量、商品性和加工特性的重要因素,考察灌浆期大小粒型藜麦籽粒表型、灌浆特性和淀粉合成酶活性的差异,可为大粒型藜麦品种的选育提供理论指导。【方法】选择千粒重大于5.0 g和小于3.0 g的藜麦材料各2份,在青海省农林科学院种质资源创新试验基地进行田间试验,比较自灌浆期始7 d、14 d、21 d和28 d籽粒表型、灌浆特性和淀粉合成酶活性等在大小粒型藜麦间的差异。【结果】(1)大小粒型藜麦籽粒面积、周长、直径、粒长、粒宽表型性状随着生育时期均极显著增大,且粒型间存在显著差异,并以籽粒面积和周长差异最大,大粒型藜麦分别显著高于小粒型藜麦9.12%~11.54%和21.49~23.92%。(2)灌浆期间大粒型藜麦百粒干质量始终显著高于同期小粒型藜麦,平均增幅在21.23%~31.04%;大小粒型藜麦灌浆速率随生育期均先上升后下降,均符合“慢—快—慢”的变化规律,但达到峰值时间和峰高明显不同,大粒型峰值出现早而高,小粒型则低而迟。(3)淀粉分支酶(SBE)、蔗糖合成酶(SS)、可溶性淀粉合成酶(SSS)和ADPG焦磷酸化酶(AGP)在大小粒型藜麦籽粒灌浆期呈现不同的变化趋势,SBE和SS活性表现为小粒型藜麦强于大粒型藜麦,而SSS和AGP活性则表现为大粒型藜麦强于小粒型藜麦。【结论】藜麦籽粒灌浆期间4种淀粉合成酶活性的差异,致使淀粉合成积累量和灌浆速率峰值的不同,进而形成籽粒表型性状的差异,而SSS和AGPase是影响藜麦籽粒大小形成的关键酶。

水稻糯性突变体r162的鉴定与基因定位

直链淀粉是影响稻米食味品质和外观品质的重要因素,主要由Waxy(Wx)基因编码的颗粒结合淀粉合酶Ⅰ(granule-bound starch synthaseⅠ, GBSSⅠ)介导合成。本研究从宁粳2号的甲基磺酸乙酯(ethyl methanesulfonate,EMS)诱变材料中筛选到了一个糯性突变体r162,与野生型相比,其籽粒外观呈不透明的云雾状,种子和糙米的粒长、粒宽以及千粒重显著下降。通过扫描电镜对淀粉形态进行观察,发现突变体的淀粉颗粒上存在孔洞。半薄切片碘染结果表明,突变体r162发育时期胚乳的造粉体排列结构与野生型相似,但碘染后颜色更浅。理化性质分析发现,突变体r162的总淀粉、总蛋白质和总脂肪含量与野生型相比无显著差异,但是表观直链淀粉含量极显著下降、胶稠度极显著增加,糊化特性发生明显改变,并且淀粉的崩解值、回生值、回复值以及米粉在尿素中的膨胀体积均小于野生型。通过基因定位和测序发现,突变基因Wx位于第6号染色体短臂上,Wx基因第7个内含子的第1个碱基(Int7-1)由鸟嘌呤(G)替换为腺嘌呤(A),造成Wx基因的编码区存在10个碱基的缺失,导致其编码的GBSSⅠ蛋白自第256位氨基酸起出现错误翻译,使蛋白质翻译提前终止,因此将该等位变异命名为Wx-r162。进一步通过蛋白质印迹法检测发现,突变体中的GBSSⅠ蛋白水平极显著下降。酶活性测定也证实,突变体r162中GBSSⅠ活性明显降低。综上所述,Wx-r162基因被视为一个新的等位变异,这种突变导致GBSSⅠ活性下降,进而造成突变体r162表观直链淀粉含量降低和籽粒表现出不透明的表型。

Effect of steam-flaking on chemical compositions,starch gelatinization,in vitro fermentability,and energetic values of maize,wheat and rice

Intact and steam-flaked grains of maize,wheat and rice（with whole hulls） were analyzed for chemical composition,starch gelatinization degree（SGD） and in vitro fermentation characteristics to investigate the influence of cereal type and steam-flaking（SF） processing on their nutritive values.The treatments were arranged in a 3×2 factorial design.Obvious differences（P〈0.001） in chemical composition and energetic values were observed among the different cereal types.SGD and gas production（GP） rate was significantly increased（P〈0.001） by SF processing.SF processing also increased（P〈0.01） the proportion of propionic acid and decreased the acetic：propionic acid ratio in vitro.Steam-flaking also increased organic matter digestibility and the energetic value of the cereal grains,especially rice.Based on these results,rice probably is more amendable to SF processing than maize and wheat.In conclusion,it is feasible to partially substitute maize grain with wheat or rice in ruminant diets,and steam-flaking can significantly improve the nutritional value of wheat and rice grains.

Changes in Starch Accumulation and Activity of Enzymes Associated with Starch Synthesis of Rice at Different N Supplying Dates

The changes in grain-filling, starch accumulation and activity of enzymes associated with starch synthesis in two different hybrid rice varieties were analyzed at different N supplying dates (earlier-date-emphasized, mean-date-emphasized and later-date- emphasized). The results showed that the N application of later-date-emphasized could promote grain-filling rate, increase grain weight and amylopectin content. The peak of activity in three enzymes of ADPglusoce pyriphosphorylase (ADPG), starch synthesis enzyme (SSS) and starch branching enzyme (SBE) in grains of two different rice varieties was not changed obviously, but the mean and maximum activity of these three enzymes changed, and the changes of SSS and ADPG were bigger than that of SBE as N supplying date changed. The N application of earlier-date-emphasized increased SSS activity and the N application of later-date-emphasized increased ADPG and SBE activities. The mean SSS activity during whole grain-filling period, and ADPG and SBE activities at middle and late period of grain-filling were significantly or very significantly correlated with grain-filling rate and accumulating rate of amylose and amylopectin. Both of ADPG and SBE played an equal important role in the changes of amylose and amylopectin content. The N application of later-date-emphasized increased amylose and amylopectin accumulating rate.

Genotypic Variation for High Temperature Tolerance in Relation to Carbon Partitioning and Grain Sink Activity in Wheat

Effect of high temperature tolerance in relation to carbon partitioning and grain sink activity was studied in ten genotypes of wheat (viz C 306, PBW 343, PBW 502, PBW 509, PBW 521, PBW 522, PBW 550, Inqalab, WL 711 and Sonalika) under normal (November, 25.6°C during grain filling) and late planting conditions (December, 29.4°C). Contents of reducing sugars first increased till actively metabolizing stage i.e. 14 days after anthesis (DAA) in parallel with the activity of acid invertase and thereafter declined. Significant reduction in total free sugars and sucrose content was observed during grain development. Acid invertase activity got induced especially in PBW 343 and C 306 under late sown conditions, whereas sucrose synthase, total amylase activities got repressed. Sucrose synthase was significantly high at all stages and it predominated over invertases. Neutral invertase and total amylase showed peak activity of one week earlier in the late sown crop as compared to normal sown crop. A premature cessation of starch deposition occurred in cvs PBW 521, PBW 522 under late sown conditions due to shortening of grain filling period. Our results suggest that decline in sugar content in spite of high sucrolytic enzymes may be correlated to more utilization of assimilates over production/translocation for grain sink activity under high temperature influences. Knowledge of the mechanisms that underlie carbohydrate partitioning in diverse genotypes could be exploited for generating germplasm that can tolerate high temperature.

Association Mapping and Marker Development of Genes forStarch Lysophospholipid Synthesis in Rice

Phospholipids are a major kind of lipids in rice grains and have fundamental nutritional andfunctional benefits to the plant. Their lyso forms （lysophospholipids, LPLs） often form inclusion complexeswith amylose or independently influence the physicochemical and functional properties of rice starch.However, the genetic basis for LPL synthesis in rice endosperm is largely unknown. Here, we performeda preliminary association test of 13 LPL compositions among 20 rice accessions, and identified 22putative main-effect quantitative trait loci responsible for all LPLs except for LPC14：0 and LPE14：0. Fivederived cleaved amplified polymorphic sequences and one insertion/deletion marker for threeLPL-synthesis-related candidate genes were developed. Association analysis revealed two markerssignificantly associated with starch LPL traits. These results provide an insight into the genetic basis ofphospholipid biosynthesis in rice and may contribute to the rice quality breeding programs usingfunctional markers.

Suppression of starch synthase I(SSI) by RNA interference alters starch biosynthesis and amylopectin chain distribution in rice plants subjected to high temperature

Based on known cDNAs of rice starch synthase isoforms,we constructed dsRNA interference vectors for starch synthase I(SSI)to produce transgenic plants containing starch with a moderately high amylose content.We investigated the effect of SSI suppression on grain quality traits,starch biosynthesis,and amylopectin chain distribution in rice plants exposed to two different temperature regimes.The activities and transcripts of BEs,DBEs,and other SS isoforms were further investigated to clarify the effect of SSI suppression on these key enzymes and their specific isoforms under different temperature treatments.Suppression of SSI by RNAi altered grain starch component and amylopectin chain distribution,but it exerted only a slight effect on total starch content(%)and accumulation amount(mg kernel?1)and on starch granule morphology and particle size distribution.Under normal temperature(NT),insignificant differences in kernel weight,chalky kernel proportion,chalky degree,and starch granule morphology between SSI-RNAi line and its wild type(WT)were observed.However,amylose content(AC)level and granule-bound starch synthase(GBSS)activity in rice endosperms were markedly increased by SSI-RNAi suppression.The chalky kernel proportion and chalky degree of SSIRNAi lines were significantly higher than those of WT under high temperature(HT)exposure at filling stage.Inhibition of SSI by RNAi affected amylopectin chain distribution and raised starch gelatinization temperature(GT)in two ways:directly from the SSI deficiency itself and indirectly by reducing BEIIb amounts in an SSI-deficient background.The deficiency of SSI expression led to an alteration in the susceptibility of grain chalkiness occurrence and starch gelatinization temperature to HT exposure,owing to a pleiotropic effect of SSI deficiency on the expression of other genes associated with starch biosynthesis.

施氮量对高粱籽粒灌浆及淀粉累积的影响

本试验于2019-2020年以汾酒粱1号为材料,在0、75、150、225、300和450 kg N hm^(-2)6个施氮水平下,于花后每隔7 d采集不同穗位籽粒分析其灌浆特性及淀粉形成过程,探究不同氮素用量对高粱籽粒灌浆及单粒淀粉累积的影响。结果表明,与不施氮相比施氮75 kg hm^(-2)显著提高了穗粒数和产量,但随施氮量的增加产量没有显著变化;氮素对优势粒(始花日开始2 d内开花的籽粒)和劣势粒(始花日开始5~6 d间开花的籽粒)的单粒重及单粒体积、灌浆特性和单粒淀粉累积的影响趋势基本一致,施氮条件下单粒重、单粒体积和灌浆速率随施氮量增加而增加,但不施氮处理的单粒重和单粒体积仍高于各施氮处理,且缺氮显著延长了灌浆活跃期。籽粒淀粉累积速率与参与籽粒淀粉合成的关键酶ADP-葡萄糖焦磷酸化酶(AGPase)和可溶性淀粉合酶(SSS)活性显著相关;过量施氮(450 kg N hm^(-2))灌浆前期籽粒中AGPase和SSS的活性最高,促进了灌浆前期籽粒淀粉累积;施氮75 kg hm^(-2)灌浆前期籽粒中AGPase和SSS的活性和淀粉累积速率次之;虽然缺氮降低了灌浆前期籽粒中AGPase和SSS的活性,但在灌浆后期维持较高活性而延长了灌浆活跃期,因而后期具有较高的单粒淀粉累积速率,提升了单粒淀粉累积量和单粒重。