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

Phenotypic variation of root-system architecture under high P and low P conditions in potato (Solanum tuberosum L.)

Abstract Background Phosphorus (P) is an essential macronutrient required for plant metabolism and growth. Its acquisition by plants depends on the availability of dissolved P in the rhizosphere and on the characteristics of P uptake mechanisms such as root-system architecture (RSA). Compared to other crops, potato (Solanum tuberosum L.) has a relatively poor P acquisition efficiency. This is mainly due to its shallow and sparsely branched root system, resulting in a rather limited exploitable soil volume. Information about potato genotypes with RSA traits suitable to improve adaptation to nutrient scarcity is quite rare. Aim of this study is to assess phenotypic variation of RSA in a potato diversity set and its reactions to P deficiency. Results Only one out of 22 RSA-traits showed a significant increase under low-P conditions. This indicates an overall negative effect of P scarcity on potato root growth. Differences among genotypes, however, were statistically significant for 21 traits, revealing a high variability in potato RSA. Using a principal component analysis (PCA), we were able to classify genotypes into three groups with regard to their root-system size. Genotypes with both small and large root systems reacted to low-P conditions by in- or decreasing their relative root-system size to medium, whereas genotypes with an intermediate root system size showed little to no changes. Conclusions We observed a huge variation in both the potato root system itself and its adaptation to P deficiency. This may enable the selection of potato genotypes with an improved root-zone exploitation. Eventually, these could be utilized to develop new cultivars adapted to low-P environments with better resource-use efficiencies