A consensus map of QTLs controlling the root length of maize

Traits related to the root length of maize (Zea mays L.), reported by 15 QTL studies of nine mapping populations, were subjected to a QTL meta-analysis. Traits were grouped according to ontology, and we propose a system of abbreviations to unambiguously identify the different root types and branching orders. The nine maps were merged into a consensus map, and the number and positions of putative QTL clusters (MQTLs) were determined. A total of 161 QTLs was grouped into 24 MQTLs and 16 individual QTLs. Seven MQTLs harbored root traits, which had been reported to be collocated with QTLs for grain yield or other drought-responsive traits in the field. The most consistent collocations were observed for the number and weight of the seminal roots (five loci). Based on our analysis at least six loci are good candidates for further evaluation (bins 1.07, 2.04, 2.08, 3.06, 6.05 and 7.04). For example, the MQTL in bin 2.04 harbored ten different single QTLs; the MQTLs in bins 1.07 and 3.06 combined 11 and 7 QTLs, respectively, that were detected in more than three populations. The presented database is a first step for a comprehensive overview of the genetic architecture of root system architecture and its ecophysiological functio

QTL involved in the partial restoration of male fertility of C-type cytoplasmic male sterility in maize

Partial restoration of male fertility limits the use of C-type cytoplasmic male sterility (C-CMS) for the production of hybrid seeds in maize. Nevertheless, the genetic basis of the trait is still unknown. Therefore, the aim to this study was to identify genomic regions that govern partial restoration by means of a QTL analysis carried out in an F2 population (n=180). This population was derived from the Corn Belt inbred lines B37C and K55. F2BC1 progenies were phenotyped at three locations in Switzerland. Male fertility was rated according to the quality and number of anthers as well as the anthesis-silking interval. A weak effect of environment on the expression of partial restoration was reflected by high heritabilities of all fertility-related traits. Partial restoration was inherited like an oligogenic trait. Three major QTL regions were found consistently across environments in the chromosomal bins 2.09, 3.06 and 7.03. Therefore, a marker-assisted counter-selection of partial restoration is promising. Minor QTL regions were found on chromosomes 3, 4, 5, 6 and 8. A combination of partial restorer alleles at different QTL can lead to full restoration of fertility. The maternal parent was clearly involved in the partial restoration, because the restorer alleles at QTL in bins 2.09, 6.04 and 7.03 originated from B37. The three major QTL regions collocated with other restorer genes of maize, a phenomenon, which seems to be typical for restorer genes. Therefore, a study of the clusters of restorer genes in maize could lead to a better understanding of their evolution and function. In this respect, the long arm of chromosome 2 is particularly interesting, because it harbors restorer genes for the three major CMS systems (C, T and S) of maiz

Mapping of QTLs for lateral and axile root growth of tropical maize

Maize genotypes may adapt to dry environments by avoiding desiccation by means of a deeper root system or by maintaining growth and water extraction at low water potentials. The aim of this study was to determine the quantitative genetic control of root growth and root morphology in a population of 236 recombinant inbred lines (RILs) from the cross between CML444 (high-yielding)×SC-Malawi (low-yielding), which segregates for the response to drought stress at flowering. The RILs and the parental lines were grown on blotting paper in growth pouches until the two-leaf stage under non-stressed conditions; the parents were additionally exposed to desiccation stress induced by polyethylene glycol with a molecular weight of 8000 Dalton (PEG-8000). The lengths of axile and lateral roots were measured non-destructively at 2, 5, 7 and 9days after germination, by scanning with an A4 scanner followed by digital image analysis. CML444 had a lower rate constant of lateral root elongation (kLat) than SC-Malawi, but the two genotypes did not differ in their response to desiccation. QTLs affecting root vigor, as depicted by increments in kLat, the elongation rate of axile roots (ERAx) and the number of axile roots (NoAx) were identified in bins 2.04 and 2.05. QTLs for NoAx and ERAx collocated with QTLs for yield parameters in bins 1.03-1.04 and 7.03-04. The correspondence of QTLs for axile root traits in bins 1.02-1.03 and 1.08 and QTLs for lateral roots traits in bins 2.04-2.07 in several mapping populations suggests the presence of genes controlling root growth in a wide range of genetic background

Yield of tropical Asian maize (Zea mays L) at alternating row irrigation and at severe drought

Drought is a major reason for inconsistent grain yield of maize in lowland tropical and subtropical areas. In bimodal rainy seasons with unequal amounts of rainfall, the shorter season requires germplasm with sufficient residual yields at various situations of low water availability. Thus farmers will avoid the risk of cultivation failure. The respective adaptation of eight Thai hybrids was tested in two dry seasons from late November 2003 to April 2005. Furrow irrigation of 40 mm was applied at seven days intervals from planting to physiological maturity (control, W1); 50% less water supply than W1 from the sixth week onwards by alternating irrigation of one of two rows (W2); withholding water from 5 weeks after planting to the beginning of anthesis (W3). At W3, three hybrids excelled with yields above 350 g m-2, i.e. residual yields of more than two of them performed very well at W2 too, with more than 650 g m-2, a residual yield of about 80%. This genetic range is encouraging to breed for earlier hybrids that can be cultivated in the minor rainy season with a reduced risk of failure

Temporal dynamics of kernel set of tropical sweet maize (Zea mays L.) as influenced by genotype and mild drought

Maize grain yield is often affected by drought stress at flowering. Fast and synchronous emergence of silks probably is the key to high kernel set but non-destructive methods to follow the temporal grain set were missing. We solved this problem by marking flint kernels on the ears of sweet maize to reflect daily kernel set, as modern sweet maize is quite similar in vigor to field maize in Thailand. The effects of mild pre-anthesis drought stress and of the genotype were examined in two experiments (over two years both). The highest number of kernels resulted from pollination on the first or second day of silking. More than 90% of the kernels per ear were usually set by day four or five. Mild drought stress reduced the number of kernel-bearing positions along the ear as well as the number of kernels per position on each day of pollination in 2007 but there was no significant deviation in the principal grain set curve. As a consequence of mild drought stress, the differences in daily kernel set between the two water regimes were rather small compared to the differences among genotypes, for which genotype-specific deviations from the general pattern of daily kernel set were observed. Most important, a new tool exists now to reliably study variable stress situations, using normal grains on sweet maize ears or yellow grains on white grain ears as visual marker systems

Swiss maize (Zea mays L) landraces. Their genetic diversity and distinctiveness in a global comparison

Swiss maize landraces are expected to be genetically diverse, as they have been cultivated in different climatic regions of Switzerland for almost 500 years. A core collection of 35 Swiss maize landraces was recently defined. This core collection was analyzed in the present study, with the objectives (i) to resolve genetic diversity and phylogeny of the core collection, (ii) to relate these results to those obtained in a worldwide collection of maize landraces, thereby (iii) analyzing separation and admixture and (iv) to identify unique alleles that were detected only in Swiss maize landraces (Swiss alleles). A high diversity (HT = 0.61) in an international comparison and many Swiss alleles pointed at the value of this core collection as a plant genetic resource. The genetic differentiation within the core collection was in very good accordance with the geographic separation caused by the Swiss Alps. The accessions grouped into three major clusters, two northern and a southern one. Additionally, landraces from Valais built an intermediate cluster, which is probably the result of hybridization between different European germplasm. Continuous maize cultivation in remote areas may have favored genetic drift and intentional selection by farmers and may have led to this particular cluster. In the international comparison, northern Swiss accessions were related to European and American Northern Flints, whereas southern Swiss accessions were closely related to southern European Flints (e.g. Italian Orange Flints). Some northern Swiss accession combined high diversity with many Swiss alleles, which may be valuable for broadening the European Flint pool

Drought stress and tropical maize: QTL-by-environment interactions and stability of QTLs across environments for yield components and secondary traits

A recombinant inbred line (RIL) population was evaluated in seven field experiments representing four environments: water stress at flowering (WS) and well-watered (WW) conditions in Mexico and Zimbabwe. The QTLs were identified for each trait in each individual experiment (single-experiment analysis) as well as per environment, per water regime across locations and across all experiments (joint analyses). For the six target traits (male flowering, anthesis-to-silking interval, grain yield, kernel number, 100-kernel fresh weight and plant height) 81, 57, 51 and 34 QTLs were identified in the four step-wise analyses, respectively. Despite high values of heritability, the phenotypic variance explained by QTLs was reduced, indicating epistatic interactions. About 80, 60 and 6% of the QTLs did not present significant QTL-by-environment interactions (QTL×E) in the joint analyses per environment, per water regime and across all experiments. The expression of QTLs was quite stable across years at a given location and across locations under the same water regime. However, the stability of QTLs decreased drastically when data were combined across water regimes, reflecting a different genetic basis of the target traits in the drought and well-watered trials. Several clusters of QTLs for different traits were identified by the joint analyses of the WW (chromosomes 1 and 8) and WS (chromosomes 1, 3 and 5) treatments and across water regimes (chromosome 1). Those regions are clear targets for future marker-assisted breeding, and our results confirm that the best approach to breeding for drought tolerance includes selection under water stres

Primary tumor–derived systemic nANGPTL4 inhibits metastasis

Primary tumors and distant site metastases form a bidirectionally communicating system. Yet, the molecular mechanisms of this crosstalk are poorly understood. Here, we identified the proteolytically cleaved fragments of angiopoietin-like 4 (ANGPTL4) as contextually active protumorigenic and antitumorigenic contributors in this communication ecosystem. Preclinical studies in multiple tumor models revealed that the C-terminal fragment (cANGPTL4) promoted tumor growth and metastasis. In contrast, the N-terminal fragment of ANGPTL4 (nANGPTL4) inhibited metastasis and enhanced overall survival in a postsurgical metastasis model by inhibiting WNT signaling and reducing vascularity at the metastatic site. Tracing ANGPTL4 and its fragments in tumor patients detected full-length ANGPTL4 primarily in tumor tissues, whereas nANGPTL4 predominated in systemic circulation and correlated inversely with disease progression. The study highlights the spatial context of the proteolytic cleavage-dependent pro- and antitumorigenic functions of ANGPTL4 and identifies and validates nANGPTL4 as a novel biomarker of tumor progression and antimetastatic therapeutic agent

Ausweitung des Sojaanbaus in Deutschland durch züchterische Anpassung sowie pflanzenbauliche und verarbeitungstechnische Optimierung

Die Arbeiten im Sojaforschungsprojekt waren erfolgreich und konnten wichtige Impulse für die Ausweitung des Sojaanbaus in Deutschland geben. So sind die entwickelten Stämme und Kreuzungsnachkommen eine Basis für den Aufbau einer eigenständigen deutschen Sojazüchtung. Die Sorten Korus und Protibus erwiesen sich als besonders geeignet für die Tofuherstellung. Die im Projekt entwickelte Labortofurei ist ein Züchtungsinstrument zur Identifikation vielversprechender Genotypen, mit dem auch die weitere Entwicklung frühreifer Tofusojasorten unterstützt werden kann. In Gefäßversuchen konnte gezeigt werden, dass die Reaktion auf Kühlestress während der Hülsenansatzphase zwischen den Sorten variiert und es tolerante, kompensierende und sensitive Sorten gibt. Die praktische Selektion auf Kältetoleranz war erfolgreich und für die Selektion auf Unkrauttoleranz konnte ein System etabliert werden. Bis auf das Präparat Radicin können die vorhandenen kommerziellen Bradyrhizobienpräparate für den Praxiseinsatz empfohlen werden. Die Hypothese, dass die Selektion des Symbiosepartners auf Kühletoleranz lohnenswert ist, wurde bestätigt. Bei der Sortenprüfung in ganz Deutschland zeigte sich, dass die Anbauwürdigkeit von Soja gut und nur an wenigen der geprüften Standorte nicht gegeben war. Die 00-Sorte ES-Mentor lieferte insgesamt die höchsten Relativerträge sowie den höchsten Rohproteinertrag, bei den 000-Sorten schnitt Sultana besonders gut ab. Eine Variation der Saatzeit sowie verschiedene Verfrühungstechniken erweisen sich nicht als ertragsrelevant. Beim Erfolg der Unkrautregulierung mit Torsionshacke, Fingerhacke und Flachhäufler gab es keine Unterschiede. Im Dammanbau lassen sich Sojabohnen mit gutem Unkrautregulierungserfolg kultivieren. Bei der Sojaaufbereitung sollte eine unnötig hohe Erhitzung der Bohnen bei der Aufbereitung vermieden werden, da durch die Erhitzung neben der Trypsininhibitoraktivität auch Eiweißverdaulichkeit reduziert werden. Mit ausschließlich indirekter, länger einwirkender, trockener Wärme (z. B. Biogasabwärme), ist es schwierig, gute Aufbereitungsqualitäten zu erzielen. Der Wissenstransfer mit Feldtagen und Website www.sojainfo.de war wichtig und erfolgreich zur Steigerung des Interesses am heimischen Sojaanbau