Maize kernel color depends on the interaction between hardness and carotenoid concentration

Maize kernel color and carotenoid concentration are traits valued by the food industry to ensure the quality of their products. Correlations between color and carotenoid concentration have been extensively reported. Based on the concept that chromaticity is modified differently by opaque and translucent materials, we tested the hypothesis that maize kernel color is not only the result of total carotenoid concentration but also a consequence of kernel hardness. Kernel hardness (test weight, vitreousness, and floaters percentage), carotenoid concentration, and color (HunterLab) were measured in thirteen commercial hybrids. Genotypes showed significant differences in all analyzed kernel hardness traits, carotenoid concentration (24.7–39.4 mg kg⁻¹), and HunterLab color dimensions. Kernel color values and kernel hardness were correlated. Genotype differences in b (yellowness) were observed in kernels with similar total carotenoid concentration but contrasting hardness. For a similar carotenoid concentration harder genotypes always showed lower b values. When whole kernels were milled and color was measured on the resulting flour, genotype differences in yellowness disappeared, further supporting that the kernel vitreous structure affects kernel color. Our results sustain the notion that the genotype capacity to form larger proportions of vitreous endosperm impacts color regardless of total carotenoid concentration.     

Genetic and environmental factors affecting grain texture in common wheat

Thirteen wheat cultivars grown in six locations were compared for kernel weight, protein content and grain texture, as determined by the Single Kernel Characterization System (SKCS). Moreover, puroindolines a (Pin-A) and b (Pin-B) bound to starch were quantified by densitometric scanning of A-PAGE fractionations. All cultivars shared allele Pina-D1a coding for wild-type Pin-A, and differed from each other in allele composition at Pinb-D1 coding for Pin-B. Cultivars with Pinb-D1a exhibited soft grain and high amounts of Pin-A and Pin-B compared to cultivars with Pinb-D1b or Pinb-D1d. Significant genetic variation for grain hardness and Pin-A level was detected in soft cultivars. The ratio between Pin-A and Pin-B levels in soft cultivars was approximately 6:5, whereas it varied between 9:5 and 10:1 in hard cultivars. Protein content was significantly correlated with Pin-B content (r=0.34) and SKCS value (r=0.36) in soft wheats. Significant correlations (0.68 and 0.73 for soft and hard wheats, respectively) were observed between Pin-A and Pin-B levels. Grain hardness was not correlated with puroindoline levels and Pin-A/Pin-B ratio in both textural classes. By contrast, kernel weight was found to act as a major environmental factor affecting grain texture in both soft and hard wheats.     

正常生长条件下推迟授粉对玉米子粒生长的影响

通过对先后吐出苞叶的花丝进行特定时间的授粉,研究正常生长条件下推迟授粉对玉米子粒生长的影响。结果表明,推迟授粉对先授粉子粒的生长影响较小,先授粉子粒粒重无显著差异,但显著减低了后授粉子粒的粒重,先玉335及登海605两个品种表现一致。进一步研究发现,后授粉子粒的生长动态即干物质积累动态与正常授粉子粒并不存在显著差异,先玉335、登海605、郑单958和大成168这4个品种表现一致,说明无胁迫条件下,推迟授粉仅仅相对推迟了后授粉子粒的生长发育时期,生长时间缩短,从而影响了子粒粒重形成。因此,正常生长条件下推迟授粉事件并未影响子粒生长,胁迫条件下的其他因素可能是造成子粒败育的根本原因。     

玉米脱粒破碎率关键影响因子及其最优预测模型研究

子粒破碎率高是当前中国玉米机械收获子粒的重要限制因素,解析破碎率变化原因,建立其简便预测模型是需要解决的重要问题。本文采集7个玉米品种在3个种植密度下组合的果穗,在不同子粒含水率梯度条件下开展单穗脱粒试验。种植密度在6万～9万株/hm2范围内对子粒破碎率没有影响,品种、子粒的含水率、抗侧压碎力和穿刺强度等的影响均达到统计显著水平。品种对破碎率变化的偏贡献率为12.7%,且品种的偏贡献率子粒含水率的偏贡献率抗侧压碎力的偏贡献率穿刺强度的偏贡献率,种植密度的偏贡献率接近于零。破碎率的最优预测因子是穿刺强度,预测模型:破碎率=10.25×0.990穿刺强度,满足破碎率不高于5%约束的穿刺强度值不得低于60 MPa。研究结果可为玉米破碎率预测、宜机收玉米新品种培育与鉴定、脱粒机具设计与制造提供数据支撑和技术参考。     

玉米自交系子粒大小和形状分类及其与营养成分相关分析

使用包含丰富遗传变异的508份玉米自交系对玉米子粒大小和形状等8个性状进行考察,分析其在不同遗传材料间的分布差异,基于该群体建立子粒大小的分类指标,研究子粒大小和形状与子粒营养间的相关性。结果表明,子粒大小和形状等8个性状的平均变异系数(CV)为10.8%,其中,粒长变异大于粒厚和粒宽;粒厚和粒宽呈高度正相关,粒厚和粒长呈较强负相关,同时粒长和粒宽相关不显著;子粒整体大小在不同类群中的变异较小,粒长、粒厚、粒宽长比等形状性状在不同类群中差异显著,其中,坚秆综合群材料的子粒偏长、偏薄,热带/亚热带及非坚秆综合群材料的子粒偏宽、偏厚。508份自交系被分为特大粒、大粒、中粒、小粒和特小粒5个类别,子粒大小和形状等8个性状和子粒营养的相关性都较弱,且大部分为负相关,表明子粒大小和形状不是决定子粒营养的主要因素。     

适宜机械粒收玉米品种脱水特性及相关性状研究

以5个不同熟期玉米杂交种为试验材料,通过玉米子粒含水率、脱水速率及相关性状测定,比较不同玉米品种脱水等性状。试验结果表明,适合粒收品种华美1号与其他品种相比,具有生育期短、含水率低、生理成熟后脱水速率快和果皮薄等特点,2016年生理成熟和收获时含水率分别为32.25%和20.20%,2017年分别为35.28%和17.47%。相关分析结果表明,子粒脱水速率与果皮厚度呈极显著负相关,相关系数为-0.975;与苞叶脱水速率和含水率呈显著相关,相关系数分别为0.935和-0.950;与其他性状相关性不显著。     

不同类型玉米子粒灌浆特性分析

以普通玉米、糯玉米、爆裂玉米和甜玉米为材料,用Logistic方程拟合子粒灌浆过程,分析一系列次级灌浆参数。结果表明:不同类型玉米粒重表现为普通玉米>糯玉米>甜玉米>爆裂玉米,不同部位粒重表现为下部>中部>上部。相关分析表明,玉米子粒最终粒重的高低主要取决于灌浆速率的大小,而不是灌浆持续时间的长短。     

利用研磨法测试玉米子粒耐破碎性方法及参数优化研究

采用二次通用旋转组合设计优化玉米子粒耐破碎性测定方法与参数,提高测定准确率和辨识度。实验选定碾磨时间(X_1)、旋转速度(X_2)、测定子粒质量(X_3)为考察因素,以子粒破碎率为考察指标,采用二次通用旋转组合设计优化子粒耐破碎性测定方法与参数。实验优化所得玉米子粒耐破碎性测定的最佳参数为碾磨时间80 s,转速1 200 r/min,测定子粒质量30 g,在此条件下,玉米品种郑单958和新引M751子粒破碎率差值为4.07。优化所得的测定子粒破碎率的方法及参数稳定可行。     

小麦粒形QTL元分析及候选基因预测

粒形是影响小麦籽粒产量和品质的重要参数,是由多基因控制的复杂数量性状。为发掘控制小麦粒形相关的真实主效数量性状位点(quantitative trait loci, QTL),本研究利用BioMercator 4.2软件,以小麦高密度分子标记遗传图谱为参考图谱,对来自不同遗传作图群体的113个控制小麦粒长的QTL和86个控制粒宽的QTL进行图谱整合、映射以及QTL元分析。通过建立QTL一致性图谱,获得18个控制小麦粒长和8个控制粒宽的一致性QTL(meta quantitative trait loci, MQTL)位点,置信区间最小可达到0.57 cM,主要分布在2B、2D、3A、3B、4B、5A、5B和7D染色体上。在5A染色体Xgwm293～Xgwm304和Xgpw2120～Xgpw2273a标记区间内,预测到7个与小麦粒长和粒宽相关的候选基因。本研究为小麦粒形QTL精细定位以及分子标记辅助选择育种提供理论依据。     

玉米子粒败育过程的早期特征及物质动态

通过对不同类型玉米子粒发育动态比较研究发现,败育粒在授粉前期其子房长度及重量就明显低于正常子粒。随授粉后天数的增加,其差距日渐扩大,约在授粉后8～12d(8－12DAA)停止发育转向衰退。子粒败育过程可区分为两个阶段：0－8DAA为败育诱导期,8－16DAA为表观衰败期。在子粒败育诱导期,糖分及蛋白质浓度并不低。研究认为,顶端子粒的败育可能与其库活性较低有关。     

玉米自交系生理成熟后子粒自然脱水速率分析

玉米生理成熟后子粒自然脱水速率是影响收获时子粒含水量的重要因素之一。以179份玉米自交系为试验材料,分别在生理成熟期和收获期测定子粒含水量,分析生理成熟后子粒脱水速率。通过聚类分析,179份玉米自交系按子粒脱水速率快慢可分为4类,属于子粒脱水速率快的自交系有13份,平均脱水速率为1.29%/d。利用2 824个SNP标记,将13份快速脱水的玉米自交系划分为5个杂种优势群,可为选育收获期子粒含水量低、适宜机收子粒的玉米品种提供参考。     

春小麦种子脱水蛋白的检测及其积累动态

植物种子对细胞脱水具有高度的耐受性,研究种子的细胞脱水保护机制对植物的抗旱性改良具有重要参考价值。为了给种子脱水保护机制的研究提供信息,以8个春小麦品种为试材,利用免疫印迹方法对种子中的脱水蛋白成分进行了检测和初步的比较,结果发现,在不同春小麦品种间,种子脱水蛋白成分存在差异,即具有多态性。春小麦种子脱水成熟过程中,脱水蛋白从乳熟期开始积累,到蜡熟期以后脱水蛋白条带数不再增加,而只表现为量的增加。     

玉米子粒败育机理研究进展

本文综述了玉米子粒败育的生理生态研究进展，并讨论了玉米子粒败育机理的研究方向。     

Sorghum starch properties as affected by growing season,hybrid, and kernel maturity

The objective of this study was to evaluate the physical and chemical changes that occur in sorghum starch during grain maturity. Two sorghum hybrids were grown in irrigated plots in 2008 and 2009; upon reaching the mid-bloom stage in maturity approximately 200 heads were tagged in each plot. Samples were collected beginning ten days after anthesis (DAA) until harvest. The samples were then decorticated and the starch isolated. The starch granule size distribution was greatly affected by the collection date as well as the growing season and hybrid. The samples ranged from 16.3% amylose in 10 DAA to 23.3% amylose in 35 DAA. The crystallinity of the starch decreased as the DAA approached physiological maturity (35 DAA). Starch thermal properties were also altered due to DAA, most notably the ΔH was 16.1 J/g at 14 DAA, 11.95 J/g at 35 DAA, and 9.45 J/g at 56 DAA. The unique chemical and thermal properties of the starches could allow for utilization of the starch in differing applications.     

Plasticity of sorghum kernel weight to increased assimilate availability

Understanding source or sink limitations on crop yield is critical for the rational design of agricultural practices as well as breeding strategies. In the present article, we studied sorghum [Sorghum bicolor (L.) Moench] source–sink yield limitations during grain filling, and tested the hypothesis that the time in which kernel maximum water content is reached during grain filling defines a temporal limit for the crop to profit from source increases. Earlier studies have never tested increasing assimilate availability per kernel in different developmental stages. We conducted a field experiment increasing assimilate availability per kernel at anthesis and 15 days after anthesis in commercial hybrids. The anthesis treatment was aimed to increase assimilates per kernel from early grain filling, and the 15 days after anthesis treatment from the stage kernel maximum water content was achieved. Both treatments removed 50% of the kernels from one side of the panicle. Kernel dry weight (KW), kernel water content and kernel volume were measured in apical and basal positions of the panicle throughout grain filling. Increased assimilate availability always yielded a higher KW (34% increase). This KW increase was consistent across the two kernel developmental stages when the treatment was imposed, the panicle position and hybrid. Achieving maximum water content did not prevent kernels from increasing their weight when assimilates were subsequently increased. Final KW was closely related to maximum kernel volume (r² = 0.72; n = 42; p < 0.0001). Increased assimilate availability per kernel promoted changes in both kernel growth rate and duration of grain filling.

We applied a quantitative approach for determining the magnitude of sorghum KW changes in response to assimilate availability changes during grain filling. This allowed us to compare our data to previously published articles, and to determine any general response pattern across environments. The analysis supported our observation that sorghum KW is highly responsive to increased assimilates, and indicated that increased assimilate availability during filling always increased sorghum KW. As such, growth of sorghum kernels is predominately source limited; breeding and management practices aimed to increase assimilate availability per kernel will be likely to enhance sorghum yield. Results show that the crop has the capacity to profit from source increases even after the initial grain-filling stages have occurred.     

Field emission scanning electron and atomic force microscopy,and Raman and X-ray photoelectron spectroscopy characterization of near-isogenic soft and hard wheat kernels and corresponding flours

Secondary field emission scanning electron microscopy (FE SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate native near-isogenic soft and hard wheat kernels and their roller milled flours. FE SEM images of flat-polished interior endosperm indicated distinct differences between soft and hard wheats with less internal continuity in the soft wheat, whereas individual starch granules were much less evident in the hard kernel due to a more continuous matrix. AFM images revealed two different microstructures. The interior of the hard kernel had a granular texture with distinct individual spheroid features of 10–50 nm while the images obtained for the soft kernel revealed less distinct small grains and more larger features, possibly micro-structural features of starch granules. Raman spectra resolved identical distinct frequencies for both kernel types with slightly different intensities between types. Finally, the chemical surface compositions of flour for these two types of kernels obtained by XPS provided subtle insight into the differences between soft and hard wheat kernels. These combined advanced microscopic and spectroscopic analyses provide additional insight into the differences between the soft and hard wheat kernels.     

Molecular characterization of the Puroindoline a-D1b allele and development of an STS marker in wheat (Triticum aestivum L.)

Kernel hardness is mainly controlled by one major genetic locus on the short arm of chromosome 5D in bread wheat. Twelve Chinese and CIMMYT wheat cultivars were characterized for the deletion region of Pina-D1b genotype and developing a novel STS marker for this allele. PCR and SDS-PAGE were used to confirm the Pina-D1b genotype, and then 20 pairs of primers were designed to amplify the fragment including deletion region in Pina-D1b genotype by primer walking strategy. An STS marker Pina-N spanning deletion region in Pina-D1b was developed and sequencing results showed that all of 10 Pina-D1b genotypes uniformly possessed a 15,380 bp deletion in comparison with that of Chinese Spring with wild type. This study provided an alternative method to exam Pina-D1b by molecular marker and will accelerate identification of puroindoline alleles in bread wheat.     

Modelling wheat breakage during roller milling using the Double Normalised Kumaraswamy Breakage Function: Effects of kernel shape and hardness

The effects of wheat properties on breakage during First Break roller milling, as described by the Double Normalised Kumaraswamy Breakage Function (DNKBF), were investigated. A set of 45 wheats from nine varieties representing the range of commercial varieties grown in the UK, and grown over three harvest years at several nitrogen fertiliser levels, were milled at five roll gaps under Sharp-to-Sharp and Dull-to-Dull dispositions. The resulting particle size distributions were fitted with a DNKBF in order to understand the physical significance of the DNKBF parameters and to relate them to shape and hardness. The DNKBF parameters related strongly to hardness as measured using either the Single Kernel Characterisation System or Particle Size Index, allowing the particle size distribution over the range 0–4000 μm to be predicted solely from wheat hardness. A residual analysis showed that the remaining variation was correlated with kernel mass, and that more elongated kernels break to give slightly larger particles than more spherical kernels of equivalent hardness. Two types of breakage are identified, one of which principally produces many small endosperm particles along with large bran particles, while the other tends to produce mid-sized particles. The former dominates under Dull-to-Dull milling and for soft wheats, while the latter becomes more prominent under Sharp-to-Sharp milling and for harder wheats.     

生态因素对玉米子粒发育影响及调控的研究

通过播期、覆膜调控，研究了不同生态条件下不同类型品种的生长发育，重点研究生态因素对玉米花后子粒发育的影响。试验主要结果如下：高温少光条件影响子粒灌浆，表现在灌浆期持续时间短、灌浆速率相对较低。晚熟品种灌浆期长而灌浆速率相对较低，早熟品种灌浆期短而灌浆速率相对较高，是正常年份两类品种都能取得高产的原因。子粒体积变化与干重变化趋势一致。适宜生态条件下，玉米穗粒性状变异系数小，果穗发育整齐一致。掖单13穗长较大，易于形成大果穗，高产潜力大，但高温少光条件下，穗粒性状变异系数大，果穗不整齐，产量低。高温少光条件下，子粒呼吸速率明显降低，高值持续时间短；同时CTK含量较低。ABA含量变化规律性不强，子粒生长受多种内源物质协调调控。