甘肃省玉米地方种质资源遗传多样性分析

对来源于甘肃省不同地州的148份玉米地方种质资源的22个主要性状进行了遗传多样性分析。结果表明:①甘肃省玉米地方种质资源的多样性在地州间存在明显差异,多样性以陇南、天水、平凉、庆阳、定西富集地,多样性指数范围在1.5941～1.2126;而河西地区的武威、张掖、酒泉、金昌,陇中地区的兰州、临夏、白银多样性相对较低,多样性指数范围在0.9627～0.5679。②甘肃省玉米地方种质资源各地区间主要性状的多样性差异也十分明显,22种性状在各地区的多样性有不同差异,多样性指数范围在0～2.1093。③22个主要性状的多样性则以开花日数、穗轴粗、行粒数、主茎叶片数、黑粉病、抽丝日数、穗粗、穗位高、穗长、抽雄日数、雄穗分枝数等11个数量性状的多样性指数较大,多样性指数范围在2.0996～2.0056,粒型(0.5465)、小斑病病级(0.5499)、轴色(0.5829)和穗型(0.8701)等质量性状的多样性指数较小。研究表明甘肃省玉米地方种质资源的变异较大,遗传较丰富。     

Phenotypic assessment of genetic gain from selection for improved drought tolerance in semi-tropical maize populations

Most maize production across the globe is rain-fed, and production is set to be negatively impacted as duration and occurrence of droughts increases due to climate change. Development of water-deficit tolerant maize germplasm has been a major focus for most breeding programmes. Here, we sought to assess the genetic gain for grain yield in two maize populations developed for drought tolerance at CIMMYT by evaluating their cycle progeny through hybrid performance. Inbreds derived from different cycles of the Drought Tolerant Population (DTP) and La Posta Sequia (LPS) were mated to a tester (CML550), and resulting hybrids were evaluated under managed water-deficit stress and well-watered conditions. The difference in yield between water-deficit and well-watered treatments was 27% and 36% for the DTP and LPS, respectively. Genetic gain for grain yield across cycles for the two populations was confirmed in the study. Genetic gain was observed for both treatments indicating that selection for water-deficit stress tolerance simultaneously improves grain yield in well-watered conditions. The DTP population had a genetic gain of 0.07 t ha⁻¹ cycle⁻¹, while the LPS had 0.16 t ha⁻¹ cycle⁻¹ under water-deficit conditions. Significant genetic gain was also observed in the well-watered treatments for both populations. Anthesis to silking interval was significantly reduced under water-deficit stress conditions in both populations. Plant and ear height were reduced in the LPS population in both treatments, while no reductions were observed for the trait in the DTP population. Potential water-deficit stress tolerance donor lines with yields comparable to commercial check varieties were identified.     

Assessing the genetic diversity of Portuguese maize germplasm using microsatellite markers

A collection of Portuguese maize accessions representing a valuable source of genes for introduction into modern cultivars is stored at the Portuguese Plant Germplasm Bank (Banco Português de Germoplasma Vegetal—BPGV). To assess genetic diversity among inbreds, microsatellite analysis was carried out for 54 inbred lines representing the diversity of Portuguese dent and flint maize germplasm. Fifty American and other European elite inbreds were also analysed for comparison. Fifteen microsatellite loci distributed throughout the maize genome were chosen based on their repeat unit and base composition. A total of 80 alleles were detected with an average allele number of 5.33 per locus. Polymorphism information content (PIC) values and observed genetic distances showed the existence of large variability among inbreds. Cluster analysis indicated that almost all of the inbreds could be distinguished from each other and Portuguese inbreds were present in all clusters formed. These associations were consistent with the known pedigree records of the inbreds, confirming a mixed origin of Portuguese materials. Comparative analysis of microsatellite diversity among groups was established according to important traits for both breeding and line identification. This revealed that, although most of the genetic diversity (>95%) was attributable to differences among inbreds of different groups, the existence of phenotypic differentiation in endosperm colour, kernel type and cob colour could be suggested for grouping. These findings support the joint use of molecular and morphological traits in management of the germplasm collection. In this study, SSR markers proved to be effective to characterise and identify maize inbred lines, and demonstrate associations among them. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ex-situ conservation of maize germplasm from different latitudes

Germplasm collections often include open-pollinated varieties from diverse latitudes and climatic areas that cannot be correctly conserved in a single environment. The objective of this research was to investigate if open-pollinated maize varieties from diverse latitudinal and climatic conditions could be conserved in a single location. Twelve varieties from the humid Spain, the dry Spain, and the Canary Island were multiplied in three locations from the humid Spain, one from the dry Spain, and one from the Canary Islands. Hand pollinations were made in 100-plant plots following a randomized complete block design with two replications in five locations during two years. Differences between origins and between varieties were significant for most traits, including those related to growth cycle (male and female flowering and grain moisture). The varieties from each latitudinal and climatic origin did not behave as a consistent germplasm block; contrarily, the location × variety interaction was significant for most traits. The varieties from the humid Spain maintained their ranks of growth cycle across locations and differences between varieties were more important in the dry Spain. The growth cycle of the Canarian varieties was completely different in the dry Spain. We can maintain the varieties from any Spanish environment and latitude at any location, but most varieties could be modified by natural selection for adaptation.     

Diversity among melon landraces (Cucumis melo L.) from Greece and their genetic relationships with other melon germplasm of diverse origins

Diversity among 17 melon landraces and inbred lines of Group Cantalupensis, Inodorus, and Flexuosus germplasm from Greece was assessed using 24 RAPD primers, 11 morphological traits of fruit, two yield-related characteristics, and resistance to powdery mildew. Accessions were genetically diverse and the greatest variation was detected in Group Flexuosus. Comparative analysis of Greek germplasm and an array of previously characterized reference accessions [RA; 68 from Africa (15), United States (U.S.; 5), Central Europe (14), Japan (19), and Spain (15)], spanning major market classes employing 19 RAPD primers (standard marker array), indicates that all but one of the accessions from Greece showed genetic affinities among themselves and with 23 RA of various origin (i.e., Japan, U.S., Central Europe, Spain and Israel) and market class. Accessions from Greece were, however, distinct from the African landraces and most Spanish melons. Greek accessions also showed little genetic affinity with the Casabas (Blanco and Crenshaw), Ogen, and U.S. Eastern Market accessions. Group Flexuosus and Inodorus accessions from Greece possessed genetic affinities with Western Asian (Group Conomon) and Mediterranean (Group Inodorus) market classes, respectively. The uniqueness of Greek melon landraces portends their potential usefulness for the enhancement of U.S., European, and Asian melon market classes. This revised version was published online in July 2006 with corrections to the Cover Date.     

转基因技术在玉米种质改良中的应用

简述了玉米转基因工程中遗传转化的受体系统、目的基因和转基因技术的研究进展.分析了转基因技术在改良玉米品质、抗虫、抗病、抗除草剂、耐盐、抗旱、抗寒性、雄性不育、抗真菌和抗病毒病基因等方面取得的成效.     

QTL mapping of improving forage maize starch degradability in European elite maize germplasm

Improving maize starch content is of great importance for both forage and grain yield. In this study, 13 starch degradability traits were analysed including percentage of the seedling area, floury endosperm, hard endosperm of total grain area, percentage of the floury endosperm surface and vitreousness ratio surface hard: floury endosperm surface, etc. We mapped quantitative trait loci (QTL) in a biparental population of 309 doubled haploid lines based on field phenotyping at two locations. A genetic linkage map was constructed using 168 SSR (simple sequence repeat) markers, which covered 1508 cM of the maize genome, with an average distance of 9.0 cM. Close phenotypic and genotypic correlations were found for all traits, and were all statistically significant (p = 0.01) at two locations. Major QTL for more than two traits were detected, especially in two regions in bins 4.05–4.06 and 7.04–7.05, associated with 13 and 9 traits, respectively. This study contributes to marker‐assisted breeding and also to fine mapping candidate genes associated with maize starch degradability.     

玉米耐低温种质资源的初步鉴定和筛选

摘要：本试验对654份玉米自交系的耐低温特性进行了鉴定,在常温（25℃）和低温（10℃）胁迫下分别测定种子的发芽率以及低温胁迫下的发芽时间。以相对发芽率和平均发芽时间作为耐低温特性评价指标,通过聚类分析筛选到30份强耐低温自交系和43份对低温胁迫强敏感自交系,为培育耐低温玉米新品种和挖掘耐低温相关基因提供种质资源。     

热带亚热带玉米种质的研究与利用进展

丰富优异的种质资源是玉米育种工作的基础,而种质基础的宽窄和遗传多样性的丰歉,则是玉米育种取得突破性进展的关键.半个多世纪以来,科技的发展在推动农业生产发展的同时,还趋向于缩小农作物的遗传基础.据统计,目前世界上收集到的玉米品种资源约有 8万多份,其中美国和墨西哥国际玉米小麦改良中心( CIMMYT)各保存 2万多份,我国 15990份 [1].     

玉米种质苗期耐冷性状的遗传分析

摘要：早春低温冷害是黑龙江省主要的自然灾害之一,已成为影响本区域玉米产量水平提高的重要因素。本研究选择不同耐冷玉米种质8份,按Griffing Ⅱ的设计组配,分析低温逆境下玉米出苗及幼苗期性状的遗传规律。相关分析表明,相对出苗指数、相对出苗率、相对苗干重、相对根干重两两相关,相对出苗率与相对根总长相关,上述性状适合作为玉米幼苗耐冷性鉴定的指标。不同亲本的GCA方差、不同组合的SCA方差在相对出苗率、相对发芽指数、相对苗干重、相对根干重、相对根总长等性状上的差异显著。非加性基因效应在相对出苗率、相对发芽指数、相对苗干重、相对根干重、相对根总长中起到重要作用,且狭义遗传力普遍较低,各性状均低于50%,高低次序为相对发芽指数>相对出苗率>相对根干重>相对苗干重>相对根总长,上述性状选择适宜在中晚代进行选择。     

我国玉米资源研究现状及发展展望

从玉米种质资源扩增、外来玉米种质资源改良和利用等方面综述了我国玉米种质资源研究现状,指出玉米种质资源狭窄的危害及扩增种质资源的重要意义,并对未来玉米种质资源研究的发展提出建议。     

Diallel analysis of Fusarium head blight resistance in genetically diverse winter wheat germplasm

New sources of partial resistance to Fusarium head blight (FHB) in wheat have been identified over the past decade; however, little is known of their breeding value. A 20 parent partial diallel that included resistant genotypes from the U.S., Europe, China and South America was used to evaluate the potential of these sources of resistance as parents in wheat breeding programs. Eight plants replication⁻¹ of each of 190 crosses and 20 parents were point-inoculated with Fusarium graminearum under greenhouse conditions in two replicated experiments. Both general (GCA) and specific combining ability (SCA) were significant. Most of the variance for FHB severity was associated with additive genes; however, estimates for SCA ranged from highly negative to highly positive in both resistant × resistant and resistant × susceptible crosses which suggest that improving FHB resistance through gene pyramiding strategies based on additive genetic variation may be complicated by interaction effects that condition FHB resistance.     

Testcross performance and diversity analysis of white maize lines derived from backcrosses containing exotic germplasm

Introgression from exotic maize (Zea mays L.) into adapted breeding pools can broaden and diversify the genetic base of adapted germplasm. The first objective of this study was to determine the agronomic performance of white maize lines derived from adapted × exotic backcrosses in tropical environments. Six exotic white maize inbred lines were crossed to an adapted white line (1368) and the F₁s were backcrossed to 1368. Forty-one BC₁F₄ lines derived from these backcrosses and the recurrent parent were crossed with a common inbred tester (9071) and the progeny were evaluated at eight environments in Nigeria. The testcrosses × environment interaction mean square was not significant for all agronomic traits. The BC-derived lines containing exotic germplasm contributed significantly to the variation in testcross mean grain yields and other agronomic traits. Among the 41 testcrosses, only 5 yielded significantly less than 1368 × 9071, with the 7 best testcrosses producing between 304 and 867 kg ha⁻¹ more grain than 1368 × 9071. The second objective of this study was to assess the genetic divergence of the BC-derived white lines from their adapted recurrent parent. Thirty-nine BC-derived white lines along with 1368 and 9071 were genotyped with ten AFLP primer pairs that generated 506 polymorphic fragments. The average allelic diversity of the lines was 31 ± 0.07. The genetic distance (GD) estimates of each BC-derived line from 1368 varied from 0.76 to 0.84, with a mean of 0.80 ± 0.003. The average GD for all pairs of the BC-derived lines was 0.63 ± 0.005, varying from 0.31 to 0.89. The observed significant amount of variation among the BC-derived white lines suggests that they can contribute new alleles for expanding the genetic base of tropical maize and for developing high-yielding hybrids.     

Testcross performance of maize lines from backcross populations containing highland Mexican or highland Peruvian germplasm

Summary Backcross populations of maize (Zea mays L.) were produced by crossing the early maturing inbred line W153R with the highland Mexican race Cónico then backcrossing to W153R (Q1 population) and by crossing W153R with the highland Peruvian race San Gerónimo then backcrossing to W153R (Q3 population). The populations were recombined by one generation of random mating. Testcrosses were produced from S₀ plants in the original and recombined versions and these were evaluated in New Zealand for grain yield, grain moisture and other traits.Unexpected changes occurred during recombination for increased grain yield in the Q1 population and for decreased grain moisture in the Q3 population. This indicates strong, unplanned selection. Many testcrosses were higher yielding than check hybrids of W153R, but most were later maturing.S₁ lines selected for high grain yield and acceptable grain moisture in testcrosses were advanced to the S₂ generation and re-tested. All produced testcrosses with lower grain moisture than late maturing hybrid checks. Testcross grain yields of one Q1 line were equivalent to those of late maturing checks and its testcross had a lower grain moisture. The high yield potential of hybrids of this line was confirmed in the S₄ generation.     

Identification,characterization and geographic distribution of male-sterility restorer and maintainer lines from diverse pearl millet germplasm

Summary To determine the distribution and geographic specificity of sterility maintainers in pearl millet, Pennisetum americanum (L.) Leeke, 428 diverse pearl millet germplasm accessions representing variation from 12 countries were crossed with a male-sterile line 5141A. The F₁ hybrids were classified as male-fertile or male-sterile based on the seed set on bagged ear heads and an other morphology. Among these, 87 (20.3%) were classified as male-fertile, 32 (7.5%) as male-sterile, 282 (65.9%) as segregating for male-fertile/male-sterile and 27 (6.3%) behaved as male-fertile in the rainy and male-sterile in the postrainy season. Restorer lines were distributed in all the countries studied except Cameroon and USSR. Maintainer lines were observed from six countries but were concentrated in India. These maintainer lines differ from one another in several morphological and agronomic characters such as flowering, plant height, spike length and grain size. They may prove to be useful sources of material for generating new male-sterile lines. The restorers can be used to produce commercial hybrids.Submitted as J.A. No. 719 by the International Crops Research Institute for the Semi-Arid Topics (ICRISAT).     

Dissection of identical-by-descent segments during the formation of foundation parents derived from Suwan germplasm of maize

Suwan germplasm plays important roles in maize breeding in tropical/subtropical regions, especially in southern China. To analyze the genetic characteristics of Suwan maize germplasm, one panel of 73 lines derived from the Suwan population and temperate resources were collected and genotyped using 56,110 single-nucleotide polymorphism (SNP) markers. The results revealed four subgroups, namely, QR273, Ki32, HCL645, and PH4CV, with an average genetic distance of 0.304, varying from 0.001 to 0.370. In addition, many identical-by-descent (IBD) segments were found among Suwan germplasms and their descendants, of which 78 segments were detected only in the QR273 subgroup, 18 segments were detected only in the Ki32 subgroup, 53 and 11 segments were detected only in the PH4CV and the HCL645 subgroup, respectively. Pairwise comparisons showed that 13 segments were common between the QR273 and Ki32 subgroups, 5 segments were common between the QR273 and HCL645 subgroups, 26 segments were common between the QR273 and PH4CV subgroups. Five and 14 segments were common between the Ki32 versus HCL645 subgroups and Ki32 versus PH4CV subgroups. Three segments were commonly detected in the Ki32, QR273, and HCL645 subgroups. Candidate gene analysis showed that 132 genes were located in these segments, wherein seven new candidate genes were associated with flower time (FT)-related traits, which were located in the IBD segments of QR273 or HCL645. Zm00001d033130_T005 and Zm00001d013768_T001 were located in the IBD segments specific to the QR273 subgroup. These two genes function in cell differentiation and flower development and would be very important for the phenotypic variations of the given FP subgroups. These results provide new insights and scientific proof for dissecting the genetic basis of complex traits and the utilization of Suwan germplasm in future maize breeding.     

Performance stability of maize genotypes across diverse hill environments in Nepal

The national maize improvement program in Nepal regularly receives elite maize (Zea mays L.) genotypes from CIMMYT and other countries and tests them for their performance stability in highly diverse environments. Studies were conducted on research stations and farmers’ fields at five sites in three years to determine performance stability of exotic maize genotypes. Replicated on-station and on-farm studies were conducted using 25 and 10 genotypes, respectively, including a local check and an improved check (Manakamana-3), in 2004–2006. We analyzed grain yield, days to flowering, plant and ear height, plant population, husk cover, and plant and ear aspect. Stability and genotype superiority for grain yield was determined using genotype and genotype × environment (GGE) biplot analysis that compares among a set of genotypes with a reference ‘ideal’ genotype, which has the highest average value of all genotypes and is absolutely stable. Several genotypes produced significantly higher grain yield than the local check. Four genotypes (‘Across9942 × Across9944’, ‘Open Ended White Hill Population’, ‘Population 44C10’ and ‘ZM621’), that produced significantly higher grain yield than the improved check, also had other agronomic traits (days to flowering, plant and ear height, number of ears, resistance to leaf blight, plant and ear aspect and husk cover tightness) equal to or better than the improved check. GGE-biplot analysis showed that Across9942 × Across9944 and ZM621 were the most superior genotypes in the on-station and on-farm trials, respectively. The findings from this study provide new information on the stability of the maize genotypes that are also adapted to other regions of the world. Such information could be useful for maize improvement program for the highlands in Nepal and other similar environments.