Mendel and the onset of modern genetics: too good to be true?

Im 18. und 19. Jahrhundert wurden sowohl in Europa als auch in den USA Kreuzungsexperimente an Mais und Zierpflanzen, aber auch an der Erbse durchgeführt. Mendel kannte zumindest einen Teil der Literatur, als er seine „Versuche über Pflanzenhybriden“ 1866 veröffentlichte. Im Gegensatz zu seinen Vorgängern fielen Mendel die konstanten Zahlenverhältnisse auf, die in den Nachkommen seiner Kreuzungsexperimente zu beobachten waren. Nachdem die Arbeiten Mendels über mehrere Jahrzehnte weitgehend unbeachtet blieben, wurden seine Theorien zur Vererbungslehre 1900 von de Vries, Correns und Tschermak wiederentdeckt und experimentell bestätigt. Kurz darauf kamen erste Zweifel auf, da die Ergebnisse Mendels fast durchweg sehr nahe an seinen Erwartungswerten lagen. Ronald A. Fisher publizierte 1936 einen Artikel, der schlussfolgerte, dass ein Großteil von Mendels Ergebnissen zugunsten der theoretischen Spaltungsverhältnisse gefälscht worden sein müsste. Damit war die Mendel-Fisher-Kontro­verse geboren. Zum Jubiläum der Veröffentlichung der Grundlagen der Vererbungslehre von Gregor Mendel brachten Stern & Sherwood 1966 ein Buch heraus, welches sowohl Mendels Texte auch die der Wiederentdeckung seiner Lehren sowie den kritischen Text von Fisher enthielten. Damit nahm die Mendel-Fisher-Kontroverse an Fahrt auf und sorgte für zahlreiche weitere Publikationen. Ob Mendel einfach Glück hatte, ob er wissentlich Pflanzen aussortierte, die nicht seinen Erwartungen entsprachen oder ob er einen Assistenten hatte, der zu gut wusste, was Mendel erwartete – wie Fisher vermutete – werden wir nicht mit letzter Sicherheit herausfinden können. Gesichert ist, dass die Mendelschen Vererbungsregeln bis heute ihre Gültigkeit haben und in Zukunft behalten werden.In the 18th and 19th century crossing experiments using maize, ornamentals and peas were carried out in Europe and in the USA. Mendel knew at least a part of the literature when he published his famous paper "Experiments on Plant Hybridisation" with the original German title "Versuche über Pflanzenhybriden" in 1866. In contrast to his predecessors, Mendel recognised the constant segregation ratios appearing in the progenies of the crossings. After being unnoticed for decades, his fundamental theory of heredity was rediscovered and experimentally verified by de Vries, Correns and Tschermak in 1900. Shortly after the English translation of Mendel's work became available in 1901, Raphael Weldon, one of the founders of biometry, published his doubts on Mendel's data since all observed segregation ratios were extremely close to the expected ones. Ronald A. Fisher concluded in a paper from 1936 that a large part of Mendel's results must have been falsified to agree closely with the postulated segregation ratios. The Mendel-Fisher controversy was born. In 1966, 100 years after Mendel's original paper was released, Stern & Sherwoodpublished a book comprising translations of Mendel's laws of inheritance, the rediscovery by de Vries and Correns and Fisher's paper. Subsequently, this led to the publication of numerous articles from different scientific disciplines on the Mendel-Fisher controversy. It may never be revealed, if it was simple luck, if Mendel sorted out plants, which did not represent the theory, or if he had an assistant "who knew too well what was expected", as Fisher speculated in 1936. Nonetheless, Mendel's work doubtlessly culminated in one of the most important breakthrough discoveries of the 19th century and is the starting point of modern genetics and plant breeding

Unraveling the genetic complexity underlying sorghum response to water availability

Understanding the adaptation mechanisms of sorghum to drought and the underlying genetic architecture may help to improve its production in a wide range of environments. By crossing a high yielding parent (HYP) and a drought tolerant parent (DTP), we obtained 140 recombinant inbred lines (RILs), which were genotyped with 120 DArT and SSR markers covering 14 linkage groups (LGs). A subset of 100 RILs was evaluated three times in control and drought treatments to genetically dissect their response to water availability. Plants with early heading date (HD) in the drought treatment maintained yield (YLD) level by reducing seed number SN and increasing hundred seed weight (HSW). In contrast, early HD in the control treatment increased SN, HSW and YLD. In total, 133 significant QTL associated with the measured traits were detected in ten hotspot regions. Antagonistic, pleiotropic effects of a QTL cluster mapped on LG-6 may explain the observed trade-offs between SN and HSW: Alleles from DTP reduced SN and the alleles from HYP increased HSW under drought stress, but not in the control treatment. Our results illustrate the importance of considering genetic and environmental factors in QTL mapping to better understand plant responses to drought and to improve breeding programs

Physiological and morphological responses of different spring barley genotypes to water deficit and associated QTLs

Water deficit is one of the major limitations to food production worldwide and most climate change scenarios predict an aggravation of the situation. To face the expected increase in drought stress in the coming years, breeders are working to elucidate the genetic control of barley growth and productivity traits under water deficit. Barley is known as a relatively drought tolerant crop and genetic variability was observed for drought tolerance traits. The objectives of the present study were the quantification of morphological and physiological responses in a collection of 209 spring barley genotypes to drought stress, and the genetic analysis by genome-wide association study to find quantitative trait loci (QTL) and the allele contributions for each of the investigated traits. In six pot experiments, 209 spring barley genotypes were grown under a well-watered and water-limited regime. Stress phases were initiated individually for each genotype at the beginning of tillering and spiking for the vegetative- and the generative stage experiments, respectively, and terminated when the transpiration rates of stress treatments reached 10% of the well-watered control. After the stress phase, a total of 42 productivity related traits such as the dry matter of plant organs, tiller number, leaf length, leaf area, amount of water soluble carbohydrates in the stems, proline content in leaves and osmotic adjustment of corresponding well-watered and stressed plants were analysed, and QTL analyses were performed to find marker-trait associations. Significant water deficit effects were observed for almost all traits and significant genotype x treatment interactions (GxT) were observed for 37 phenotypic traits. Genome-wide association studies (GWAS) revealed 77 significant loci associated with 16 phenotypic traits during the vegetative stage experiment and a total of 85 significant loci associated with 13 phenotypic traits during the generative stage experiment for traits such as leaf area, number of green leaves, grain yield, harvest index and stem length. For traits with significant GxT interactions, genotypic differences for relative values were analysed using one way ANOVA. More than 110 loci for GxT interaction were found for 17 phenotypic traits explaining in many cases more than 50% of the genetic variance

Composition, environmental stability and potential of genetic improvement of fatty acids of <i>Lupinus angustifolius<i/>

In the last decades procedures for obtaining protein isolates and concentrates derived from narrow-leafed lupins (L. angustifolius) for human nutrition have been developed. Since this processes starts with defatting of seeds, lupin oil is obtained in large quantities. Therefore, 50 genotypes of L. angustifolius were analysed regarding the fatty acid (FA) composition of seed oil and the environmental stability of fatty acid contents in order to get information on the application of lupin oil in the food industry. The results revealed an n-3/n-6 poly unsaturated fatty acid ratio of 0.13. Furthermore, the seed oil of L. angustifolius contains rather high amounts of saturated FAs (22%). Significant genotypic differences and a high heritability (h2>85%) for the content of all fatty acids are suggesting that the potential for genetic improvement of fatty acid composition by breeding is given. However, coefficients of variation below 10% for all considered traits point out that a rapid improvement in seed oil quality will be hindered by the narrow genetic base of the breeding material tested.

Scientia Agricola Phosphorus distribution and availability in untreated and mechanically separated

ABSTRACT: Biogas digestates contain valuable nutrients but also have high water contents. Digestates were sampled from two different biogas facilities before and after solid-liquid separation and were analyzed with regard to their composition and phosphorus (P) fractions. Additionally, to investigate the P fertilizer effects of these digestates in comparison with undigested slurry or TripleSuper-P (TSP), they were applied in a pot experiment (6 kg soil per pot) in an amount corresponding to 200 mg P per pot in combination with various crops (amaranth, maize, maize + beans mixed cropping, sorghum). A separation of digestates resulted in higher P concentrations of the solid fraction in comparison with the liquid fraction. The proportion of the readily soluble P fractions (H 2 O-P, NaHCO 3 -P) to the total P was higher than 70 % in all digestates. The digestates increased P uptake of the tested crops and concentrations of bioavailable P in the soil to the same extent as highly soluble TSP. Activities of soil enzymes were lower after application of the digestates in comparison to unfermented slurry. The fertilizer management of digestates can be improved by a solid-liquid separation since the solid fraction showed a relatively high concentration of P resulting in a reduction in application doses required to meet the P demands of crops

Phosphorus distribution and availability in untreated and mechanically separated biogas digestates

ABSTRACT Biogas digestates contain valuable nutrients but also have high water contents. Di-gestates were sampled from two different biogas facilities before and after solid-liquid separation and were analyzed with regard to their composition and phosphorus (P) fractions. Additionally, to investigate the P fertilizer effects of these digestates in comparison with undigested slurry or TripleSuper-P (TSP), they were applied in a pot experiment (6 kg soil per pot) in an amount corresponding to 200 mg P per pot in combination with various crops (amaranth, maize, maize + beans mixed cropping, sorghum). A separation of digestates resulted in higher P concentrations of the solid fraction in comparison with the liquid fraction. The proportion of the readily soluble P fractions (H2O-P, NaHCO3-P) to the total P was higher than 70 % in all digestates. The digestates increased P uptake of the tested crops and concentrations of bioavailable P in the soil to the same extent as highly soluble TSP. Activities of soil enzymes were lower after application of the digestates in comparison to unfermented slurry. The fertilizer management of digestates can be improved by a solid-liquid separation since the solid fraction showed a relatively high concentration of P resulting in a reduction in application doses required to meet the P demands of crops

Genome-Based Prediction of Time to Curd Induction in Cauliflower

The development of cauliflower (Brassica oleracea var. botrytis) is highly dependent on temperature due to vernalization requirements, which often causes delay and unevenness in maturity during months with warm temperatures. Integrating quantitative genetic analyses with phenology modeling was suggested to accelerate breeding strategies toward wide-adaptation cauliflower. The present study aims at establishing a genome-based model simulating the development of doubled haploid (DH) cauliflower lines to predict time to curd induction of DH lines not used for model parameterization and test hybrids derived from the bi-parental cross. Leaf appearance rate and the relation between temperature and thermal time to curd induction were examined in greenhouse trials on 180 DH lines at seven temperatures. Quantitative trait loci (QTL) analyses carried out on model parameters revealed ten QTL for leaf appearance rate (LAR), five for the slope and two for the intercept of linear temperature-response functions. Results of the QTL-based phenology model were compared to a genomic selection (GS) model. Model validation was carried out on data comprising four field trials with 72 independent DH lines, 160 hybrids derived from the parameterization set, and 34 hybrids derived from independent lines of the population. The QTL model resulted in a moderately accurate prediction of time to curd induction (R2 = 0.42–0.51) while the GS model generated slightly better results (R2 = 0.52–0.61). Predictions of time to curd induction of test hybrids from independent DH lines were less precise with R2 = 0.40 for the QTL and R2 = 0.48 for the GS model. Implementation of juvenile-to-adult phase transition is proposed for model improvement