Understanding the power of corn hybrids

<ic:message key='Bild vergrößern' />

Various types of corn hybrids from wild and domesticated lines. It is not left to chance whether the crossing is fruitful – or not. Source: Keith Weller, USDA / Wikimedia Commons

08.05.2013  - 

Cutting as much as two years off the breeding process of new corn varieties – this is the objective of plant scientists in Hohenheim in Germany. Using statistical predictions compiled on the basis of genetic data, the scientists want to identify the most appropriate sets of parent crops, cross these together and thereby shorten the breeding process from five to three years. In the process, it is hoped that an age-old mystery of plant breeding will be unravelled, namely the heterosis effect. This is the term given to the offspring of specific intersections that are particularly strong and thriving. The project, which is funded by the Federal Ministry of Education and Research (BMBF) with a total of €2.6 million, is one component of the OPTIMAL consortium, which comprises several research institutes and breeding companies in Germany and France.

The intersection of two corn lines characterised over a matter of generations by inbreeding and low yields can sometimes produce extremely strong, productive and healthy offspring. “To this day, nobody can explain how this so-called heterosis effect works,” says Albrecht Melchinger from the department of Applied Genetics and Plant Breeding at the University of Hohenheim. Nevertheless, the effect has already become an important factor for the breeding of high-yielding varieties. 

Joint project for corn breeding

For the past six years, researchers have been trying to track down the molecular basis of this heterosis effect and its role in biomass production. This work is taking place as part of the joint project GABI-ENERGY. The BMBF has contributed around €2.7 million up to the end of 2012. The project as well as funding is now being continued under the name OPTIMAL (‘Genetic and Biomarker-based Predictive Breeding of Corn Cultivars’). Also involved are plant scientists from the Leibniz Institute in Gatersleben and the Max Planck Institute for Molecular Plant Physiology in Potsdam-Golm. Breeding companies from France and Germany are contributing practical knowledge and experience of research approaches and their evaluation. The OPTIMAL project is supported by the BMBF over three years with €2.7 million.

Hybrid corn is of major importance for the food supply. Here, the agriculture sector owes a debt of gratitude to the heterosis effect – without this, the breeding of new hybrids would be unthinkable. This is not least because corn is a hermaphroditic plant, meaning that the possible combinations for crossing are almost endless. Geneticists are now hoping to use statistical predictions to limit these possibilities to a reasonable extent. This approach helps to highlight more prominent and clearly identifiable locations in the genome of the parent plants. Because it is possible to keep track of these markers, more accurate predictions can be made about the inheritance of certain genes if the DNA of the parent plant is precise known. Today, ever more of these genetic markers are being identified in genome research. On the other hand, so many genes are responsible for controlling the heterosis effect that it is extremely difficult for researchers to gain a clear understanding of the processes at work.

Measuring metabolic products

Melchinger and his researcher team in Hohenheim are focusing on the genetic information that regulates the metabolism in the corn plant. In turn, this can be divided into hundreds of individual factors known as metabolites. These comprise various sugars, amino acids and organic acids. Christian Riedel Heimer, a PhD student in the working group, expects that the sugar concentration in the leaves of descendents would be more detectable in as much as the heterosis effect also takes place at the level of the plant metabolism. Plant hormones control the growth of plants, the ripening of fruit, and leaf shedding.

The researchers hope that this approach will make the mystery a little more tangible, as far fewer genes are involved in the heterosis effect at the metabolic level. “If this is the case, we can draw conclusions that make the heterosis effect more understandable in the entire corn species,” explains Riedelsheimer.

 The data that is produced by the genetic analyses could be modelled in advance, and specific scenarios evaluated using statistical methods. “Today, it is no longer necessary to grow anything in field trials in order to see if the descendant crops have the desired properties. We can make a statistical preselection from our desks,” says Melchinger. In the future, this approach could shorten the breeding process of new corn hybrid varieties from five years to as little as three.

© biotechnologie.de/bs