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.     

The co-operative interaction of puroindolines in wheat grain texture may involve the hydrophobic domain

The puroindoline genes are causatively associated with wheat grain hardness, a commercially significant property. The proteins puroindoline (PIN) A and B are both required in their wild-type (WT) to impart soft grain texture, and absence of/mutations in either/both PIN(s) results in hard wheat. However, there is no biochemical clarity yet that explains this interdependence. This work critically analyses the roles of the tryptophan-rich domain (TRD), the little-known hydrophobic domain (HD), and certain other residues, in the physical associations of PINs. Site-directed mutagenesis-PCR was used to delete the TRD or HD and introduce an Arg39Gly substitution in PINA. The PINB-D1c mutant (Leu60Pro) was also investigated. The yeast two-hybrid system was used to assess the protein–protein interactions (PPI) of proteins. The TRD deletion or Arg39Gly substitution in PINA did not adversely affect its PPI, while deletion of HD resulted in a significant reduction. No effect on PPI was observed for Leu60Pro PINB. The results of this expression system strongly suggest that the HD is essential (but not sufficient) in higher-order associations of PINs. We propose a two-event model that explains the co-operative action of the PINs and why mutations outside the TRD may alter grain texture.     

美国硬红冬和硬红春小麦籽粒品质比较及与中国强筋小麦标准对标分析

随着人们消费结构的改变,面包市场发展迅速,但中国优质强筋小麦生产供应不足,质量差异较大,而美国硬麦有良好的加工性能和稳定的品质,制粉和烘焙特性优异。研究美国硬红冬小麦和硬红春小麦籽粒品质年度间变化特点及品质指标间相关性,可为中国强筋小麦籽粒品质研究与发展提供参考。本文汇总了美国小麦协会1999—2021年间发布的硬红冬小麦、硬红春小麦品质相关性状数据,分析了两类小麦品质指标间相互关系,并探讨了美国硬麦品质对中国现有强筋小麦标准的适配度。结果表明,与硬红冬小麦相比,硬红春小麦蛋白含量高,筋力强,形成时间、稳定时间等面团品质更高,烘焙品质更优,且籽粒、面粉品质稳定性高。对标中国强筋小麦标准可以发现,硬红春小麦对标中国强筋小麦标准的达标率高于硬红冬小麦,蛋白含量、湿面筋达标率差距尤为明显。综合考虑中国强筋小麦生产现状,并结合美国硬麦对中国强筋小麦标准达标率,中国强筋小麦标准可将蛋白含量调整为>14.5%,湿面筋含量为>32.0%,稳定时间>10 min,容重、硬度分别大于760 g·L^-1和65。硬红春小麦品质指标的相关性分析显示,拉伸面积与面包烘焙吸水率显著负相关,与面包体积显著正相关,可用于预测强筋小麦面包品质;中国标准可设置拉伸面积为105 cm²。     

Starch isolation method impacts soft wheat (Triticum aestivum L. cv. Claire) starch puroindoline and lipid levels as well as its functional properties

Wheat (Triticum aestivum L.) kernel hardness is a major quality characteristic, which has been ascribed to the presence of puroindolines a and b. These proteins occur in higher levels at the surface of water-washed starch granules from soft wheat cultivars than at that of starch from hard wheat cultivars. In the present study, prime starch was isolated from flour from soft wheat (cultivar Claire) using a dough ball or batter based separation method. Starch isolated with the dough ball method contained lower levels of puroindolines, as well as of other starch granule associated proteins and lipids than that isolated with the batter method. Similar patterns of puroindoline and lipid levels after starch isolation can presumably be related to (polar) lipid binding by puroindolines. Both isolated starch fractions showed comparable differential scanning calorimetry thermograms, whereas higher levels of starch surface associated components restricted starch swelling. Necessary controls demonstrated that the observed differences did not arise from artefacts associated with hydration, fractionation or freeze-drying in the experimental protocols. Apparently, proteins and lipids at the starch granule surface impact water absorption and, as such, starch swelling, but they do not affect starch granule internal phenomena such as melting of the crystalline amylopectin chains.     

花生属种间杂种及其早期多倍体世代生理特性变化研究

为了研究花生属异源多倍体进化过程中的生理特性遗传变化规律,以花生区组栽野种间杂种F1、早期多倍体世代(S0~S3)及其亲本为材料,分析植株叶片中的脯氨酸、丙二醛、可溶性糖和叶绿素含量以及过氧化物酶活性等抗病抗逆相关生理生化指标的变化特征。结果表明,杂种F1代各项生理指标都高于亲本,表现出明显的杂种优势;染色体加倍后的S0~S1代植株叶片中的POD活性、脯氨酸含量和叶绿素含量均高于F1代,S1~S3代各项生理指标伴随着自交代数的增加而逐渐降低,但仍高于母本栽培种,说明染色体加倍后的多倍体植株可能具有更强的抗病、抗旱等抗逆和环境适应能力。     

Puroindolines,Pin alleles,hordoindolines and grain softness proteins are sources of bactericidal and fungicidal peptides

The puroindoline (PIN) proteins in the wheat grain are considered the primary genetic basis of texture. Their lipid-binding nature that enables an effect on texture is also likely related to their antimicrobial properties. A number of mutations leading to hard texture are reported, but their collateral effects on any antimicrobial activities are unknown. To evaluate whether antimicrobial activity is conserved at the tryptophan rich domain (TRD) and affected by point mutations, we designed a series of peptides based on the TRD of proteins encoded by the alleles Pina-D1a, Pina-D1m, Pinb-D1a, Pinb-D1b, Pinb-D1l and Pinb-D1q, as well as by the grain softness protein-1, hordoindoline-a and hordoindoline-b genes. PuroA, Pina-M (Pro-35 to Ser), Hina and GSP-1 peptides displayed measurable antibacterial activity, Pina-M higher than PuroA. Replacement of Arg-39 with Gly decreased the activity considerably, and the five Trp residues in PuroA could not be substituted with Phe without major loss of activity. Except for Pinb-L (Lys-45 to Glu) and Hinb1a, all displayed antifungal activity and none displayed haemolytic activity. The work demonstrates a potential role for this protein family in pathogen protection, stresses the importance of Trp and basic residues, and suggests potential applications in food and health industries.     

Wheat (Triticum aestivum L.) puroindoline functionality in bread making and its impact on bread quality

Wheat puroindolines (PINs) spontaneously adsorb at air/water interfaces and show excellent foaming properties. They can positively impact bread quality, in which the formation of stable foam is important for product quality. The impact of endogenous PINs on bread quality was studied by preparing gluten–starch blends from isolated gluten and starch fractions with different PIN levels, which allowed largely retaining the interaction between PINs and flour components. Our results indicate that blends with high PIN levels yielded more homogeneous crumb structures with fine gas cells than bread made with blends containing medium or low PIN levels. However, the mechanism by which PINs exert this crumb improving effect is not clear. Varying PIN levels impacted neither dough extensibility nor did it result in different PIN levels in dough liquor. Lipid removal yielded bread with a less homogeneous crumb gas cell distribution, indicating that lipids also are required to obtain good crumb structure.     

The Pinb-2 genes in wheat comprise a multigene family with great sequence diversity and important variants

The puroindoline genes Pina-D1 and Pinb-D1 located at the Ha locus on chromosome 5D of common wheat are considered the most important genetic determinants of grain hardness. The recent identification of Pinb-2 genes on group 7 chromosomes emphasises the need for detailed analysis of the genetics of this important trait. This study focussed on the analysis of Pinb-2 genes from accessions of hexaploid, tetraploid and diploid wheat, to address key questions related to their diversity and possible roles. Extensive DNA sequence heterogeneity was identified in the form of single nucleotide polymorphisms (SNPs), leading to seventeen reproducible haplotypes, of which thirteen are new. The results confirmed the known groups Pinb-2v1 to Pinb-2v5, identified a new group Pinb-2v6, and showed that the Pinb-2 genes comprised a small multigene family, at least in some genomes. The putative proteins exhibited changes at the important tryptophan-rich domain as well as basic and hydrophobic residues. A new Pina-D1 allele (at Ha locus) was also identified, designated Pina-D1t, with a premature stop codon at the TRD. Additionally, peptides designed on PINB-2 proteins displayed activity against bacteria and phytopathogenic fungi. The data strongly support the Pinb-2 genes being functionally relevant to roles including influencing grain texture.     

小麦籽粒发育时期Puroindolines蛋白与硬度的关系

为探讨Puroindolines蛋白的表达特点与籽粒硬度的关系,采用改进的SDS-PAGE凝胶分析了不同硬度小麦品种的籽粒在各个发育时期Puroindolines蛋白的表达.结果表明,不同硬度的小麦籽粒中总Puroindolines(PinA和PinB)蛋白的表达量差异不大,但与胚乳淀粉颗粒结合的Puroindolines蛋白量差异非常明显:在籽粒发育的不同时期,软质小麦籽粒淀粉粒表面结合的Puroindolines蛋白量显著高于硬质小麦;基因型同为野生型但硬度有差异的品种,籽粒较软的材料其淀粉粒表面结合的Puroindolines蛋白量也明显高于较硬的材料,说明该蛋白的结合特性是决定籽粒硬度的直接原因.结果还表明,胚乳中水溶性戊聚糖与籽粒硬度关系密切.     

Silencing of puroindoline a alters the kernel texture in transgenic bread wheat

Grain hardness is an important end-use quality parameter of bread wheat, and one of the most important characters for quality improvement. The objective of this study was to further understand the function of puroindolines and the underlying mechanism in the formation of kernel texture. The highly efficient expression vector pUBPa harboring puroindoline a (Pina) was introduced into the bread wheat cultivar Zhongyou 9507-60 via biolistic transformation and transgenic plants were obtained. The integration of the foreign Pina gene was confirmed by PCR and genomic DNA Southern blot analysis. The levels of friabilin on the surface of water-washed starch granules varied among the transgenic lines. SDS-PAGE analysis of Triton X-114 extracted protein showed that the PINA protein was absent in three transgenic lines, indicating that the endogenous Pina gene most likely had been co-suppressed by the over-expression of the Pina transgene. SKCS kernel hardness and scanning electron microscopy analysis further confirmed the changes of kernel texture in these lines.     

木薯干旱胁迫响应基因MeGSTU7自然变异分析

在2个木薯品种中检测MeGSTU7基因在不同干旱胁迫阶段的表达量变化,并克隆测序了60个木薯品种的基因区DNA序列,分析基因核苷酸多态性及其自然变异,并将核苷酸多态性与干旱胁迫表型关联分析,挖掘优等位变异。结果表明,干旱胁迫条件下,2个品种的MeGSTU7的表达量均上调。MeGSTU7基因区核苷酸变异丰富,共有23个SNP位点,A/G突变为主;外显子区总计10个同义突变,12个非同义突变;外显子区在品种资源群体中有4种主要单倍型,所有的单倍型分为两大类,分子进化分析表明,MeGSTU7的外显子区的两端受到很强的正选择作用;Q+K+MLM混合线性模型关联分析结果表明,1个Indel和2个SNP与干旱胁迫下地上部鲜重耐旱系数显著关联,并筛选得到了优等位变异。     

大豆硬实形成机制与破除技术的研究进展

硬实是种子休眠类型之一,在豆科作物中最为常见。种皮缺乏透性是硬实大豆形成的主要原因。种子硬实的影响因素包括遗传因素、大豆生长后期的环境条件以及贮藏条件等。硬实的处理方法机械划破种皮、温度处理、干湿交错处理和化学处理等。在种质保存过程中还可对种子硬实特性加以利用,发挥坚硬种皮的保水作用。     

Winter wheat genotypes under different levels of nitrogen and water stress: Changes in grain protein composition

Hard white winter wheat with superior and consistent quality is preferable for Asian markets. This study investigated the combined influences of moisture deficit during grain-fill and N management on protein quality, dough rheological properties, and protein molecular weight distributions in soft and hard winter wheats. Genotypes were grown under an irrigation gradient and two N-fertilization levels. Grain polyphenol oxidase (PPO) activity, SDS sedimentation, and Mixograph analyses were evaluated. Flour protein composition was characterized using SE-HPLC. Moisture stress during grain-fill increased flour protein content. N fertilization increased flour protein content. No significant correlation was found between flour protein and PPO. Changes in protein composition were related to general increases in protein content, regardless if the result of reduced irrigation or increased fertilization rate. The percentage of monomeric proteins increased more than the polymeric proteins as flour protein increased. Similarly, SDS sedimentation volume increased as a function of protein content. As expected, subunit GluD1 5+10 was associated with larger sedimentation volume and higher dough strength in genotypes as compared to those with subunit GluD1 2+12. Biplot analyses showed that genotypes of similar protein quality and composition responded similarly to N and irrigation treatments.     

野生大豆种皮形态结构和萌发特性的研究

通过种皮的透水性,种皮结构的电镜扫描和酸蚀种子萌发,对野生大豆种皮构造与种子休眠关系进行研究.结果表明:野生大豆种子属于典型硬实,栅栏层是引起种皮不透水的主要原因,种脐是水分进入种子的主要通道,酸蚀20～30 min能有效打破种皮的不透水性障碍.     

亚精胺处理对采后番木瓜果实质地及成熟衰老的影响

为探讨亚精胺处理对采后番木瓜果实质地变化及成熟衰老的影响,以‘日升’番木瓜为试材,采用质构仪质地多面分析（texture profile analysis, TPA）法,对亚精胺处理后番木瓜果实贮藏期间呼吸速率和色泽的变化、果实各项质地参数进行测定。结果表明：适当浓度的亚精胺处理可有效延缓番木瓜果实的软化。其中5 mmol/L的亚精胺处理效果最佳,其次是1 mmol/L亚精胺处理。果实的硬度、咀嚼性、胶着性、黏聚性、回复性较之蒸馏水处理组均有所提高,并显著降低果实的呼吸速率,延缓果实色泽的转变。而10 mmol/L的亚精胺处理加速了果实的软化及成熟衰老。相关性分析表明,果实硬度、咀嚼性、胶着性、黏聚性、回复性之间均呈现极显著的正相关性,弹性与其他质构参数间呈现较差的相关性（P<0.519）。综上所述,TPA测试可用于评价采后番木瓜果实质地的变化。     

不同贮藏时间和处理方式对野生大豆种子萌发的影响

采用刀片破皮、低温冷冻、60℃热水浴及干燥、碱液处理、浓硫酸加搅拌等方法处理野生大豆种子,研究其对野生大豆种子发芽和胚生长的影响。结果表明:经过刀片破皮和浓硫酸加搅拌处理的各项萌发指标远高于对照(P0.05);综合野生大豆幼苗的萌发指标和胚根长、胚芽及鲜重等指标,破皮和10 m in浓硫酸加搅拌处理最有利于野生大豆种子萌发;冷冻处理的各项萌发指标显著低于对照(P0.05),与常温保存相比,冷藏保存野生大豆种子的千粒重和发芽率有所增加。表明冷藏保存可以提高野生大豆种子的质量;常温下野生大豆休眠期为7个月,冷藏保存野生大豆的休眠期为8个月。     

顶空固相微萃取和气相色谱-质谱法测定菠萝蜜果肉中的香气成分

为使菠萝蜜香气成分的检测和鉴定更加快速有效,研究3种固相微萃取头对菠萝蜜果实挥发物的萃取效果,并利用气相色谱-质谱对干苞和湿苞类型菠萝蜜果实中的香气成分进行分析鉴定.结果表明,在3种萃取头中,以100 μm PDMS萃取效果最好.经100 μm PDMS萃取头萃取后,在菠萝蜜干、湿苞果实中共鉴定出66种香气物质,酯类53种,醛类6种,醇类3种,烯类2种,萜类和烷类各1种.干苞果实中主要的香气成分是戊酸-2-甲基丁酯(31.87％)、2-甲基-丁酸-己酯(23.594％)、异戊酸乙酯(10.923％)、乙酸丁酯(3.337％)、丁酸丁酯(3.164％)、己酸丁酯(3.135％);湿苞果实中主要的香气成分为2-甲基-丁酸-己酯(29.807％)、异戊酸乙酯(21.47％)、戊酸-2-甲基丁酯(21.405％)、乙酸丁酯(3.451％).顶空固相微萃取-气相色谱-质谱法可作为菠萝蜜果实香味检测的便捷方法.     

硬铺装榕树的复壮及养护研究

在分析硬铺装榕树衰败原因的基础上,阐述了地面硬铺装危害榕树的主要表现．并论述了其危害机理。通过断根法对硬铺装侧根系的榕树进行了复壮及加强养护。5年的观察和实践结果表明,断根法对侧根系的榕树复壮效果非常显著,值得推广。