In the University of Copenhagen Program of Excellence in Evolutionary Agroecology we are applying ecological and evolutionary theories to address problems in agriculture, especially the need to reduce pesticide use. Our general evolutionary hypothesis is that plant breeding is unlikely to improve attributes already favoured by millions of years of natural selection, whereas there may be unutilized potential in selecting for attributes that increase total crop yield but reduce plants' individual fitness. Our general ecological hypothesis is that increased plant density in the field is the key to increased sustainability and reduced use of pesticides, while maintaining high yields. We describe these ideas in a recent article in Evolutionary Applications (see Weiner et al. 2010 under Publications)

Background

Darwinian evolution by natural selection is driven primarily if not solely by differential survival and reproduction among individuals within a population. It is a common popular scientific misunderstanding that natural selection inevitably works to increase the survival or performance of the population or species: over the past 30 years evolutionary biologists, using data from molecular biology to social behaviour, have shown clearly that evolutionary interest of the individual is often in conflict with the interests and even the survival of the population or species. When this occurs, genes that increase individual fitness at the cost of population performance will increase in frequency. Individual selection for selfish behaviour will overwhelm group selection for altruistic behaviour when they are in conflict. This has been referred to as a “Tragedy of the Commons”.

Over the past decade, we have shown that cereals can suppress weeds effectively if sown at high density in a uniform (grid-like) pattern, instead of standard rows. Since the attributes that are desirable in a "high density, uniformly-sown, herbicide-free" crop are probably not the same as those in a "low density, row-sown, herbicide-sprayed" crop, it is likely that the potential for suppressing weeds can be increased greatly if we identify the appropriate traits. Suppression of weeds by a crop is a "group" activity.  It will be most successful if the individual crop plants do not use resources competing with each other, but cooperate in suppressing weeds.  According to evolutionary theory, such a strategy would never evolve in nature, because it reduces individual fitness.  But it may be useful in agriculture, where ecosystems are directed to meet human needs.

Hypotheses

The project tests two specific hypotheses:

(1) There is large variation in cereal (specifically wheat, Triticum aestivum) germplasm for attributes that will promote weed suppression in our high-density / high-uniformity cropping system.  This variation can be used as a basis for developing "high-density, weed-suppressing" varieties.  We are testing this by investigating variation in weed suppression under these conditions in 140 varieties of spring wheat, including land races, traditional varieties, early modern varieties and current varieties.  This variation can be used to identify the relevant characteristics that can be used in breeding.

(2) When plants are shaded by other plants or receive an abundance of light reflected by neighbours, they have smaller and more upright leaves, and longer internodes (distance between leaves on a shoot) than when the incoming spectrum is not altered by neighbouring plants. This "shade avoidance response" of plants is a response to a signal of competition from neighbours. This defensive response increases the survival and reproduction of individuals in nature, but is disadvantageous for weed suppression and yield in our high-density, high-uniformity cropping system, in which we want to optimize population, not individual, performance through an offensive collective strategy based on better exploitation of the crop's initial size advantage over weeds. We are testing this by screening mutagenized wheat plants for individuals lacking or showing reduced shade avoidance response, and testing non- or reduced-shade avoiders for improved weed suppression.

Vision

The Program of Excellence in Evolutionary Agroecology is interdisciplinary in its vision:

A vision of applied ecology: high density production systems that have more biomass, more ecosystem, and therefore provide more ecosystem services

An evolutionary/genetic vision: "communal" plants that do not waste resources competing with each other but cooperate in suppressing weeds

An agronomic vision: reduced material inputs, increased biological inputs, more knowledge, more precision, greater sustainability

The Program of Excellence in Evolutionary Agroecology team

  Jacob Weiner, Professor, Plant Ecology, Principle Investigator

  Sven Bode Andersen, Professor, Plant Genetics and Breeding, Primary Collaborator

  Jannie M. Olsen, Post-doc

  Lars Pødenphant Kiær, Post-doc

  Wibke Wille, Ph.D. student

  Hans-Werner Griepentrog, Professor, Agricultural Engineering, University of Hohenheim,

        International Collaborator

  Mai-Britt Sauer, Mads Nielsen, Allan Hansen, Technicians

There are numerous opportunities for student participation, incuding Masters Theses (Speciale). Contact Jacob Weiner (jw@life.ku.dk) or Sven Bode Andersen (sba@life.ku.dk).