“Comeback” for Old Barley Varieties

A display board from Berlin bears witness to the rise of mutation research in the 1950s, which was also intensively pursued in Halle (Saale) and Gatersleben. It has recently been handed over to the institute and has inspired Nils Stein to take a closer look at the mutants using the latest methods.

Freshly framed, they can now be admired in the corridor on the way to the IPK director’s office: 15 particularly striking barley mutants, each represented with two or three ears. A short-awned mutant can be found there, as well as a six-rowed one and another with deformed ears. The starting plant was the spring barley Heines Heisa.

The “Barley Mutation Collection” display board, which was used for teaching purposes, was produced at the end of the 1950s / beginning of the 1960s in the workshop of the “Institute for Heredity and Breeding Research”. “The board compiles a dozen of the most striking mutations from that period,” explains Professor Dr Thomas Schmülling, head of the “Applied Genetics” research group at the Institute of Biology of the Free University of Berlin. “Today, the genes responsible for most of these mutants are known and have been described at the molecular level. A breakthrough that researchers at the time could only have dreamed of,” says Professor Dr Thorsten Schnurbusch, head of the “Plant Architecture” research group at the IPK.

His visit and lecture at the institute in Berlin gave Thorsten Schmülling the idea to hand over the board to the IPK. The institute houses an extensive collection of barley mutants in its genebank. This also includes the mutants shown on the board with strongly altered ear architecture. The commission to create the board was given by Professor Dr Walther Hoffmann. He led the institute –still part of the Technical University of Berlin – from 1955 to 1972. Walther Hoffmann is regarded as a key figure in German plant breeding of the 20th century and a pioneer of mutation breeding.

He received his doctorate in 1934 with a dissertation on “The Sprouting of Cereal Crops, Especially Barley” at the University of Heidelberg. Afterwards, he worked in the barley breeding department of the Kaiser Wilhelm Institute for Breeding Research in Müncheberg. He became head of the fibre crop breeding department in 1936 and head of the department for agriculture, breeding, and genetics in 1942. From 1946, Walther Hoffmann worked at the Hohenthurm experimental field of the Institute for Plant Breeding of the University of Halle. He became professor and director of the Institute for Plant Research of the University of Halle in 1949.

Since the 1930s, pioneering work on induced mutation in barley was carried out at the University of Halle. Rudolf Freisleben (later a colleague of Walther Hoffmann in Halle) succeeded in 1942 for the first time in producing a barley line resistant to powdery mildew – a widespread fungal disease – using X-rays. He irradiated the spring barley Heines Haisa and isolated the mutants that were resistant to powdery mildew. “That was one of the first experiments in mutation breeding,” says Thomas Schmülling.

In the following years, many more mutants were induced in barley accessions. It turned out that the resistance was usually based on mutations in a specific gene, later named Mlo. In 1951, Heines Haisa was officially approved as a variety. “It was certified to have medium performance but better yield stability than more demanding varieties,” explains Thomas Schmülling.

Together with other breeding researchers, Walther Hoffmann also analysed Erectoides mutants in the 1950s – barleys with upright ears and shortened culms. Such mutants are of breeding value, as they are more resistant to lodging and allow for higher yields under fertilisation. In any case, the 1950s marked the beginning of the upswing in mutation research – also at the institute in Gatersleben.

“The mutation experiments on spring and winter barley, which had been carried out in Gatersleben for more than ten years, enabled the development of an extensive range of X-ray-induced mutants. It currently comprises around 800 forms,” it says in the 1958 volume of the institute journal Die Kulturpflanze. “This mutant material is excellently suited to work in various fields.” In the early 1960s, hundreds of additional barley mutants were produced at the institute – the “Scholz Collection”, named after the researcher Fritz Scholz. Internationally, this development is closely associated with the name Udda Lundqvist, who produced and selected more than 10,000 mutants in Sweden.

At that time, however, there was no access to DNA sequences, and the mutated genes could not yet be isolated. This was only achieved by Paul Schulze-Lefert and his colleagues in 1997. They isolated the Mlo gene at the Sainsbury Laboratory of the John Innes Centre in Norwich, England. “The corresponding publication in Cell remains a real milestone to this day,” said Thomas Schmülling. More than 40 alleles of the gene are known to date, all of which lead to broad resistance to powdery mildew. From 1999 onwards, the Federal Ministry of Research in Germany also began funding genome research. Through the research programme known as GABI, it became possible to identify the decisive genes in the mutants. GABI stood for “Genome Analysis in the Biological System Plant” and was the sister programme of the HUGO research programme – the international “Human Genome Project”, which also involved German institutions.

Where the mutants shown on the display board originated is still unclear. Werner Odenbach, a former professor at the Institute for Applied Genetics who knew Walther Hoffmann personally, suspects their origin lies in Hoffmann’s time in Halle. “But I believe that some well-known mutants such as erectoides and mlo were independently isolated by several researchers,” explains Thomas Schmülling. “That would not be unusual.” In any case, many of the historical mutants are stored in the IPK genebank.

This collection of Gatersleben barley mutants – the “Scholz Collection” – still comprises around 700 samples maintained by the IPK genebank and offered for distribution via its electronic catalogue. So far, however, demand has been low, even though IPK researchers have used various mutants recently for gene isolation. The reason may lie in the language barrier. This treasure has remained largely unknown to international barley researchers, as the essential descriptive scientific literature on these mutants has only been published in German. Professor Dr. Nils Stein, head of the “Genebank” department, is working with his colleague Srijan Jhingan to overcome this hurdle.

In consultation with the specialist journal Genetic Resources and Crop Evolution (formerly Die Kulturpflanze), English translations of several fundamental papers are to be republished, together with a review article placing the older work in today’s context. This is to be accompanied – with the support of the “Experimental Taxonomy” group at the IPK – by providing digitised reference materials such as herbarium specimens and ear samples from the mutant collection.

The display board itself has now found a new place. “It had long been hanging in the Institute for Applied Genetics stairwell, and at the beginning of the year – because of upcoming restructuring – we handed it over to the IPK,” says Thomas Schmülling. Revised and newly framed, it now hangs in the Genetics Department building at the IPK. “I was familiar with the mutants but not with the board, and I’m glad that we now have it here. I find it fascinating with what enthusiasm research into mutants was already being conducted back then – work from which we still benefit today,” says Professor Dr Thorsten Schnurbusch, who, as head of the “Plant Architecture” group, has been intensively engaged for years with the barley inflorescence.

But one mystery remains unsolved. “Walther Hoffmann also commissioned a similar display board on wheat mutations, but that one is still missing to this day,” says Thomas Schmülling.