Amylose and Lipid Contents,Amylopectin Structure,and Gelatinisation Properties of Waxy Wheat (Triticum aestivum) Starch

Starch was isolated from the endosperm of three recently developed waxy wheat lines and their parents. Their amylose and lipid contents, amylopectin structures and gelatinisation properties were evaluated. The endosperm starch from waxy wheat lines is composed essentially of amylopectin. The apparent amylose (1·2–2·0 g/100 g) and lipid contents (0·12–0·29 g/100 g) are much lower than the apparent amylose (26·0–28·4 g/100 g) and lipid contents (1·05–1·17 g/100 g) of their non-waxy parents. The amylopectin of waxy wheat lines is structurally identical to that of the parents. The peak gelatinisation temperature and gelatinisation enthalpy for waxy starch are significantly higher than for non-waxy starch, but the gelatinisation enthalpy for the amylopectin fraction of waxy starch is nearly identical to that of non-waxy starch.     

糯小麦快速选育及糯性亚基纯合速度对选择的响应

为创建糯小麦快速育种程序,进而培育出优质糯小麦新品种,选用4份糯性亲本材料和6份非糯性亲本材料进行杂交,并对分离后代进行早代籽粒碘染、乳熟期田间单株籽粒碘染选择、农艺性状选择、多重PCR分子标记检测和淀粉糊化特性测定。结果显示,糯性亲本作母本或父本,F₀代杂交籽粒均为非糯;大部分杂交组合F₁代自交籽粒中糯性籽粒的出现频率符合1/64的分离比例;非糯性材料作父本的三交组合F₁代自交分离后,糯性籽粒的出现频率符合1/512的分离比例。13个组合中,5个组合的糯粒比例达到100%,7个组合的糯粒比例超过98%,而没有经过籽粒碘染筛选的3个组合的糯粒比例仅为0.79%～6.10%,说明糯性亚基纯合速度对选择可做出快速响应,经过1代籽粒糯性筛选,糯性遗传即可稳定。中选单株均具有糯性小麦典型的RVA图谱,糯小麦面粉的低谷黏度、最终黏度、回生值和峰值时间较非糯小麦面粉显著降低,而峰值黏度、稀懈值和糊化温度在糯小麦和非糯小麦之间差异不显著。对经过2代籽粒糯性筛选的13个杂交组合共410份单株材料进行多重PCR检测,发现全糯质小麦398株...     

Ecophysiological traits in maize hybrids and their parental inbred lines: Phenotyping of responses to contrasting nitrogen supply levels

Maize (Zea mays L.) breeding based primarily on final grain yield has been successful in improving this trait since the introduction of hybrids. Contrarily, understanding of the variation in ecophysiological processes responsible of this improvement is limited, especially between parental inbred lines and their hybrids. This limitation may hinder future progress in genetic gain, especially in environments where heritability estimation is reduced because grain yield is severely affected by abiotic stresses. The objective of this study was to analyze the genotypic variation between inbred lines and derived hybrids in the physiological determinants of maize grain yield at the crop level, and how differences among hybrids and parental inbreds may effect contrasting responses to N stress. Special emphasis was given to biomass production and partitioning during the critical period for kernel number determination. Phenotyping included the evaluation of 26 morpho-physiological attributes for 6 maize inbred lines and 12 derived hybrids, cropped in the field at contrasting N supply levels (N₀: no N added; N₄₀₀: 400 kg N ha⁻¹ applied as urea) during three growing seasons. Tested genotypes differed in the response to reduce N supply for most measured traits. Grain yield was always larger for hybrids than for inbreds, but N deficiency affected the former more than the latter (average reduction in grain yield of 40% for hybrids and of 24% for inbreds). We also found (i) a common pattern across genotypes and N levels for the response of kernel number per plant to plant growth rate during the critical period, (ii) a reduced apical ear reproductive capacity (i.e., kernel set per unit of ear growth rate) of inbreds as compared to hybrids, (iii) similar RUE during the critical period and N absorption at maturity at low N levels for both groups of genotypes, but enhanced RUE and N absorption of hybrids at high N supply levels, and (iv) an improved N utilization efficiency of hybrids across all levels of N supply. Results are indicative of a more efficient use of absorbed N by hybrids than by parental inbreds. Larger grain yield of hybrids than of inbreds at N₀ was associated to (i) enhanced dry matter accumulation due to improved light interception during the life cycle and (ii) enhanced biomass partitioning to the grain.     

Effect of wx genes on amylose content,physicochemical properties of wheat starch,and the suitability of waxy genotype for producing Chinese crisp sticks

The effect of wx genes on amylose content, physicochemical properties of wheat starches, and the quality of Chinese crisp stick were investigated using near-isogenic lines (NILs) with null wx alleles in Yangmai 17 and Yangmai 01-2 backgrounds. wx genes showed significant effects on amylose content and other traits. The triple-null genotype had the lowest amylose content among eight genotypes, followed by double-null, single-null, and wild-type genotypes. The triple-null also showed lower flour yield, higher percentage of type B-granules on a volume basis and higher crystallinity than non-waxy genotypes, and showed significant differences in all pasting and thermal transition parameters compared to non-waxy genotypes, except for degree of retrogradation at day 14. For the quality of Chinese crisp stick, the hardness, crispness, fracturability, and specific volume of waxy genotype were 3.91 kg, 11.0, 1.85 mm and 104.4 ml, whereas the corresponding ranges for non-waxy genotypes were 5.39–5.70 kg, 0.5–0.9, 0.69–0.86 mm and 49.5–57.6 ml, respectively, in Yangmai 17 background. This indicates that waxy genotypes showed significantly better crisp stick quality than non-waxy genotypes. A similar trend was also observed in Yangmai 01-2 background. This indicated the potential utilization of waxy wheat for producing traditional products.     

12个玉米自交系主要农艺性状的配合力分析

12个自选玉米自交系按griffing4双列杂交模式设计,组配66个单交组合,采用完全随机区组排列进行试验,分析了株高、穗位高、产量、穗长、穗粗、穗行数、行粒数等7个性状的配合力和遗传参数.结果表明,桂99、桂422、桂517、桂A200等4个自交系综合性状较优,系组配强优势杂交组合的优良自交系.桂340综合性状最差,需进一步改良方能利用.其它自交系也有各自突出某一性状的优势,在育种工作中应注意到有目的地选择利用.桂9804产量特殊配合力方差最大,其次是桂A200、桂422和桂517,它们均有可能选育出极端高产杂交组合。     

糯大麦与非糯大麦种子萌发和胚乳消亡的比较研究

为探明糯大麦与非糯大麦种子萌发和胚乳消亡的差异,以典型糯大麦品种白青稞和甘垦5号以及非糯大麦品种扬农啤10号和苏裸麦1号为材料,采用组织化学染色、树脂半薄切片和光学显微镜观察等方法,研究了糯大麦与非糯大麦胚乳的消亡和淀粉体形态变化。结果表明,在种子萌发过程中,糯大麦种子萌发较好,发芽率较高;糯大麦和非糯大麦颖果胚乳的消亡过程基本相同,呈现出一定的时序性,均是从近胚端的腹部开始消耗,逐渐延伸至背部,最后沿腹沟延伸至远胚端;在大麦种子萌发过程中,近糊粉层中淀粉体最先消亡,小淀粉体早于大淀粉体被消耗;与非糯大麦相比,糯大麦胚乳淀粉体的消亡时间较早、消亡速率较快。概言之,糯大麦与非糯大麦种子萌发过程中胚乳的消亡规律基本相同,但糯大麦种子萌发好,胚乳消亡快。     

糯质与非糯质爆裂玉米同型系杂交种的产量和品质比较

以沈爆3号为对照,对糯质型玉米沈爆3号的产量、产量构成因素、爆花品质及营养品质进行比较.结果表明,糯质与非糯质爆裂玉米同型系玉米产量、产量构成因素、子粒商品性、爆花品质等主要性状,两者之间没有明显差异,总淀粉含量没有差异,糯质型沈爆3号的蛋白质和脂肪含量分别提高2.1%和13.1%.     

Protein quality and endosperm modification of quality protein maize (Zea mays L.) under two contrasting soil nitrogen environments

Quality protein maize (QPM) breeding involves the combined use of the opaque-2 (o2) gene and the genetic modifiers of the o2 locus to develop cultivars with modified kernel endosperm, and increased concentrations of lysine and tryptophan. This study was designed to assess grain yield performance, endosperm modification, and protein quality and quantity under two contrasting soil nitrogen environments. A 15-parent diallel cross was evaluated under one low nitrogen stress and one optimal nitrogen environment each at Harare (Zimbabwe) and Bako (Ethiopia). Most QPM hybrids showed higher protein quality levels than the best non-QPM check under both conditions. Protein concentration tended to vary across nitrogen levels, but not endosperm type. Significant differences were found for the test of main effect (nitrogen-level) for endosperm modification and tryptophan concentration. This indicated that QPM maintains quality even under low soil nitrogen, a widespread condition in Africa. General combining ability (GCA) mean squares were highly significant for most protein quality traits for each environment and across environments whereas specific combining ability (SCA) mean squares were not significant in most cases. This indicated that additive gene effects were primarily responsible for variation of most traits evaluated and hence progeny performance can adequately be predicted on the basis of parental performance. Inbred lines P2, P4 and P12 had desirable GCA effects for endosperm modification while P1 and P3 had the best GCA for tryptophan concentration in grain. The current study suggests that hybrids with desirable endosperm modification, protein quality and stable performance under low nitrogen stress and optimal conditions can be produced with careful selection.     

Combining ability analysis for Phaeosphaeria leaf spot resistance and grain yield in tropical advanced maize inbred lines

Phaeosphaeria leaf spot (PLS) disease (causal agent Phaeosphaeria maydis (Henn.) Rane, Payak & Renfro) of maize is increasing in importance in sub-Saharan Africa (SSA). However, there is still limited information on the combining ability for disease resistance of the germplasm that are adapted to African environments. Evaluating combining ability effects and their interactions with the environment would provide valuable information that can be used in the development of cultivars that are resistant to PLS. This study was therefore conducted to determine the combining ability, gene action and the relationship between grain yield and PLS disease severity among selected tropical advanced maize inbred lines. Forty five F₁ hybrids were generated by crossing 10 inbred lines in a half diallel mating scheme. The 45 hybrids along with the ten inbred parents were evaluated in four environments, with two replications each between 2007 and 2009. General and specific combining ability (GCA and SCA) effects were highly significant (P ≤ 0.001) for PLS, grain yield and days to anthesis. GCA effects accounted for 66–90% and SCA effects for 10–34% of the variation in the hybrids for PLS resistance, grain yield and days to anthesis. This indicated predominance of additive over non-additive gene action for the three traits in these inbred lines. The resistant inbred lines to PLS were A1220-4, N3-2-3-3, CML312, MP18 and CML488. These lines had good combining ability for PLS resistance and contributed towards resistance in their crosses. In general, resistant hybrids involved a susceptible and a resistant parent, where at least one of the parents had a negative GCA effect. In addition, lines A1220-4 and CML312 contributed towards high yield and were late maturing. Inbred line CZL00009 conferred genes for early maturity. Linear regression analysis indicated that grain yield of maize was suppressed by about 250 kg ha⁻¹ per each increase in PLS disease severity score, underscoring the need to control the disease. Significant (P < 0.01), negative correlations (r = −0.29 to −0.43) between grain yield and PLS severity were also detected. This showed the potential of PLS to reduce yield when favourable conditions for disease development are present. By and large, highly significant additive gene action implied that progress would be made through selection. Although non-additive effects were small (±10%), observation of dominance effects which were associated with reduced disease levels in some hybrids may be exploited in developing single cross maize hybrids among these inbreds when one parent is resistant.     

7个旅大红骨自交系的配合力分析及评价

本文采用NCII设计方法,按不完全双列杂交设计组配35个杂交组合,分析了株高、穗位、穗长、穗粗、子粒长、秃尖、百穗粒重、出籽率、穗粒重9个性状的GCA、SCA及TCA。结果表明： J344、J390、丹340、丹8415这4个自交系综合性状较优,是组配强优势杂交组合的优良自交系;JL1表现最差,需要改良应用;其它自交系的个别性状表现也较突出,在育种工作中应注意有目的的选择利用。     

Effects on Grain and Malting Quality of Genes Altering Barley Starch Composition

In this study inbred barley lines carrying waxy and/or high amylose genes were obtained from a cross between Waxy Hector and a breeders» line BE285 (high amylose Glacier×Midas) and assessed for malting quality. Inbred lines were assayed and classified as having none, one or both genes. After malting, waxy lines had a slightly lower hot water extract than normal starch lines. Large effects were demonstrated for both grain nitrogen content and hot water extract in high amylose lines and, particularly, in lines with both genes. Endosperm modification during malting was reduced by both starch mutations. Electron microscopy showed that the phenotype with both genes was characterised by a highly compacted endosperm. During malting, this structure was extremely resistant to modification.     

Comparing decentralized participatory breeding with on-station conventional sorghum breeding in Nicaragua: I. Agronomic performance

Few studies have assessed the effective gains achieved by collaborative decentralized participatory breeding, in terms of yield and other agronomic traits, in comparison with centralized conventional breeding using the same breeding schemes. Our study concerned an experience of participatory improvement of tortillero sorghum for low-input cropping systems in northern Nicaragua. It set out to compare the effect of two breeding schemes simultaneously managed on-station and on-farm. Two synthetic populations were used as sources of genetic variability. The study was designed to distinguish between three “selection modes”: farmers’ selection on-farm (FoF), breeder’ selection on-station (BoS) and breeder's selection on-farm (BoF). After two selection cycles, we found that FoF selection reduced phenotypic variability as much as BoS selection. In general, BoS selection produced higher-yielding lines under the target on-farm conditions. But FoF selection was more effective in promoting lines with higher values for an index of agronomic suitability (IAS), expressing a better balance between earliness, plant height, grain size and yield. Such genotypes might cope more easily with local environmental constraints and farmers’ preferences. BoF selection did not prove to be effective for either yield or IAS. This research shows the need for close collaboration between farmers and breeders as well as complementarities between the selection phases managed on-farm and on-station, to make breeding for difficult environments fully efficient.     

糯小麦籽粒淀粉粒度分布特征

为进一步加深对糯小麦淀粉特性的认识,选用2个糯小麦和2个普通非糯小麦品种为材料,利用激光粒度分析仪分析了糯小麦完熟籽粒中淀粉的粒度分布特征,及其与普通非糯小麦品种的差异。结果表明,糯小麦淀粉粒的粒径分布范围为1.0~43.7 μm,不同粒径淀粉粒的数目比例分布呈单峰曲线变化,体积和表面积分布均呈双峰曲线变化;糯小麦籽粒中存在2种类型淀粉粒,即A型大淀粉粒（直径≥10 μm）和B型小淀粉粒（直径<10 μm）,B型淀粉粒的数目、体积和表面积比例均高于A型淀粉粒。与普通非糯小麦相比,糯小麦籽粒中B型小淀粉粒的数目、体积和表面积比例较高,淀粉粒的平均粒径和中位粒径较大。糯小麦与普通非糯小麦不同粒径淀粉粒的数目、体积和表面积比例分布曲线存在差异。糯小麦B型淀粉粒处的峰高显著高于普通非糯小麦,A型淀粉粒处的峰值低于后者。糯小麦体积和表面积分布中B型淀粉的峰值粒径显著小于普通非糯小麦。     

旅大红骨种质的利用潜力评价及改良分析

以7个旅系与2个外杂选系组配的14个组合和对照种郑单958为材料,采用随机区组设计,3次重复试验,分析由旅系组配的组合产量、抗性、农艺性状和考种性状与对照间的差异。结果表明,旅系的产量一般配合力较高,抗性、穗粗和穗长等方面优于对照,但耐密性、抗倒性、封顶性、子粒深度、含水量和出籽率等方面与对照还有差距,且生育期长于对照。     

A comparison of inbred line and F1 testers for evaluating sorghum experimental lines in testcrosses

Selecting an effective tester for evaluating the hybrid performance and heterosis of new inbred lines is crucial to ensure their accurate evaluation. Most sorghum breeding programs use at least two elite inbred line testers when evaluating new inbred lines. These testcrosses provide valuable information, but the specificity of inbred line testers may incorrectly characterize experimental lines that would combine well with other genetic backgrounds. Reducing this risk by increasing the number of preliminary testcrosses is limited in breeding programs by resource availability. Efficiently diversifying testcrosses may be accomplished through the use of F₁ testers. Testcrosses made with F₁ testers simultaneously evaluate inbred lines against two genetic backgrounds. In preliminary testcrosses, this may reduce the probability of incorrectly discarding new lines or improve the efficiency of preliminary testcrossing. The objective of this research was to compare two sorghum inbred line testers to their respective F₁ as a tester for evaluating sorghum inbred lines (R-lines) in testcrosses for grain yield. The testers used were A.Tx623, A.Tx2752 and their F₁ hybrid, A.Tx623/B.Tx2752. Data from testcross hybrids from 33 different inbred lines grown in three environments indicated that the F₁ tester was comparable in accuracy and discriminatory efficiency to the inbred line testers. The results indicated that a single cross tester in sorghum can serve to effectively evaluate new germplasm.     

玉米育种目标浅议

本文根据近年来有种实践和杂交种种植状况，对自交系和杂交种的选育提出了自己的几点浅见，认为自交系的自身产量和种植习惯是育种中不可忽视的育种目标．     

Heritability and quantitative trait loci of composition and structural characteristics in sorghum grain

Breeding efforts in cereal crops directed toward developing or improving end-use products of grain require assessment of existing phenotypic variance and an understanding of the genetic control of grain quality traits. To this end, a grain sorghum [Sorghum bicolor (L.) Moench] mapping population consisting of 113 F_2:7 recombinant inbred lines (RILs) derived from a cross between Sureño and RTx430 was evaluated in multiple environments for grain composition (fat, fiber, protein, starch) using near-infrared reflectance spectroscopy (NIRS), and size estimates of grain parts (embryo, vitreous endosperm, floury endosperm, kernel area) using an image-based phenotyping software system. Estimates of broad-sense heritability of grain compositional traits ranged from 0.11 to 0.90, whereas those of grain size ranged from 0.16 to 0.72. Composite interval mapping (CIM) was applied to a single nucleotide polymorphism (SNP)-based linkage map to identify marker-trait associations, and through these efforts, a total of 37 quantitative trait loci (QTL) for grain quality were identified across environments. Each QTL explained between 7 and 23% of the phenotypic variation for a given grain trait. Three of the five QTL that colocalized were for traits with significant negative correlation, which included grain protein content that was negatively correlated with grain starch content. In addition, several traits that were positively correlated (e.g. fat and fiber content) also revealed colocalized QTL. Finally, we compared the present study with previous studies identifying grain composition trait loci in an effort to identify genomic regions controlling grain traits across a diversity of environments and sorghum genotypes.     

Selection before backcross during exotic germplasm introgression

Introgression of genes from exotic germplasm into breeding populations can broaden the genetic base of crop improvement. Only a very small percentage of genetic variability has been used in crop breeding programs. Traditionally, F₁ plants are used to backcross to the adapted lines or populations. An alternative approach is to backcross the F₂ individuals selected for agronomic acceptability. Our objective was to determine whether selection before backcross would lead to more progenies with both high yield and acceptable levels of agronomic performance than direct backcross without selection. To test the feasibility of the proposed approach, we conducted parallel experiments in which two exotic sorghum accessions were crossed to two adapted sorghum parents and further backcrossing was conducted with either F₁ or selected F₂ plants. Fifty random S₁ families were evaluated in three test environments. Although selection before backcross resulted in a higher frequency of families with maturity equal to or earlier than those of the adapted parents, no consistent changes in grain yield and plant height were observed between populations with and without selection. Similar results were found with either an inbred or a population as the recurrent parents. Given these findings and the extra generation required, we do not recommend selection before backcross in the process of introgression of exotic germplasm.     

玉米抗锈病自交系种质的发掘与评价

选用遗传育种上较为常用的184份玉米自交系(包括121份普通玉米和63份糯玉米),在两个环境下对锈病抗性进行鉴定,共筛选出K22、齐319、T2等18份高抗系和农大1145、中128、R-8等18份抗病系,普通玉米自交系中高抗和抗病的占26%,糯玉米自交系中只占6%。基于SNP标记基因频率的系统聚类将184份自交系划分为9个类群,从血缘类群上来看,普通玉米自交系中P类群最抗,塘四平头类群锈病抗性最差;糯玉米自交系中热带类群抗性稍好,所有类群间病情指数差异均达到极显著水平。     

我国糯玉米种质研究进展

通过对国审糯玉米品种亲本来源的分析,表明用普通玉米优良基因改良糯玉米杂交种、自交系、农家种是我国目前糯玉米育种的主要方法,是扩增糯玉米种质资源的有效途径。选育二环系有可能成为我国糯玉米育种的主要方法。从农家种中直接选育一环系亲本,育成优质、高产糯玉米新品种十分困难。