Re: Plant breeding without the madness (5/2/2008)

1.Re GMW: Plant breeding without the madness
2.Marker Assisted Selection and the Future of Agricultural Biotechnology

NOTE: The articles this is responding to are available at


1.Subject: Re GMW: Plant breeding without the madness
From: Doug Gurian-Sherman

Although very encouraging, there are a few important cautions about MAB (or MAS is it is more commonly called) that need to be recognized. It is also important to understand the difference between marker assisted selection (MAS, or MAB) and conventional breeding, which was included in the following piece along with MAB.

MAS uses relatively new (about 20 year old) genetic technology that 'maps' the genes of a plant by identifying unique genetic 'fingerprints' (the markers of MAS)throughout the genome of the crop (the entire complement of DNA in the plant's cells). These fingerprints can be associated with particular genes or traits that are useful, such as drought tolerance. The advantage of MAS is that the many genetically complex traits in crops (such as drought tolerance or yield), are more likely to be successfully utilized than with conventional breeding. Also, more simple genetic traits can often be bred more quickly with MAS than conventional methods.

Conventional types of breeding, including making hybrids, select for the crop's visible (or otherwise measurable) characteristics to improve the crop, rather than using genetic markers. This can be very difficult for traits that are complex genetically (controlled by many genes), respond to environmental conditions (e.g. weather changes) or that are very rare in the crop. Despite these limitations, however, conventional breeding has been very successful, and will continue to be. Conventional breeding can also be done with a crop's wild relatives - this does not require MAS. So many potentially useful traits from wild species that can breed with a crop are not limited to the use of MAS. MAS, however, can often facilitate breeding with crop wild relatives or allow breeding for traits that conventional breeding is not good at using (like complex traits).

What are the potential concerns about MAS? First, in some (perhaps many) countries, patents may be given for MAS. Intellectual property protection is of course one of the big problems with genetic engineering technology, in that it gives the company undue control over seeds (such as not allowing farmers to save seed). In fact, the big genetic engineering companies are using MAS frequently now, and not just as an alternative to GE, but to facilitate moving GE traits into many new varieties of a crop, or combining MAS traits with GE. Second, similar to genetic engineering, this technology takes some sophisticated (and expensive) equipment and training to carry out, so it cannot be done by low-tech breeders or farmer-breeders. It also requires good genetic maps of the crops involved, something not available yet for some crops - especially many important to developing countries.

Finally, contrary to the statement [in the article posted - see NOTE above], MAS does have risks for food safety. Breeding crops with their wild relatives has led to instances of introducing toxic substances into crops. It must be done with caution. Plants produce many substances to protect themselves from insects, diseases, and herbivores, and some of these are toxic to us as well (some are also useful as medicines, etc.). Crops tend to have lost many of these, or they are removed by cooking or other processing. But wild crop relatives may produce others. This is also one reason why indigenous knowledge of wild plants can be so incredibly important. However, many scientists feel that GE goes considerably beyond these risks by introducing entirely new genes to food that could never have gotten there otherwise. By contrast, the risks from wild relatives comprises a much narrower span of possibilities, and are more likely to be similar to risks already recognized in the crop.

The main point is that although MAS can be very useful, and can be held up as an alternative to GE in many cases, we should be aware of its limitations as well, and not push it as a panacea.

- Doug
Doug Gurian-Sherman, Ph.D.
Senior Scientist
Food and Environment
Union of Concerned Scientists


2.Is Genetic Engineering Obsolete?
Marker Assisted Selection and the Future of Agricultural Biotechnology [originally published in the magazine Gene Watch in 2006 ]

Increasing attention has been recently focused on a technology for breeding plants and animals that employs rapidly accumulating data from genomic studies, but does not involve genetic engineering (GE). This has led to the hope that this sophisticated hybrid between molecular genetics and traditional breeding, called Marker Assisted Selection (MAS), may meet some of the unmet promises of genetic engineering, and perhaps even replace it. This hope is strengthened by the biotech industry's continuing failure to develop transgenic crops with substantial benefits, the increasing use of MAS by industry leaders such as Monsanto and Dupont, and the continuing rejection of gene-spliced crops by citizens in Europe, Japan, and elsewhere.

With so much at stake, it is a good time to ask: What is MAS? Will it succeed in those areas where genetic engineering has failed? If so, will it eliminate concerns about unintended consequences of our use of biotechnology, or is it merely another technological fix that looks promising at first glance, but that reveals serious drawbacks upon closer examination?


MAS uses information from the DNA sequence of an organism, such as rice or tomatoes, to improve the speed and efficiency of breeding. Certain unique DNA sequences from each crop or domestic animal can be used to track specific useful traits during the breeding process. The use of these genetic sequences, called markers, to breed for useful traits is in contrast to traditional breeding, which uses the expressed trait itself (or phenotype) to select desired progeny. MAS uses the same breeding 'material' as traditional breeding; the diversity of qualities exhibited by livestock, crops, and the related wild species that can breed with them.

By improving the availability and breadth of this diversity, MAS may expand the range of traits that can be bred into crops and animals without using genes from other species (transgenes), as is the case with GE. By improving efficiency, MAS can also greatly accelerate the breeding process.

The markers used in MAS are arranged along an organism's chromosomes, along with the genes as


Back to the Archive