Ganesan Srinivasan

Is marker-assisted selection cost-effective compared with conventional plant breeding methods? The case of quality protein Maize.

This paper presents the findings of a case study designed to compare the cost of using conventional plant breeding methods with the cost of using a new DNA-based crop selection technique known as marker-assisted selection (MAS). The case study, which was carried out in Mexico at the International Maize and Wheat Improvement Center (CIMMYT), focused on a narrowly-defined breeding objective—transferring the Quality Protein Maize (QPM) phenotype, controlled in part by a mutant allele of a gene called opaque2, from one elite maize inbred line to another elite inbred line. Costs associated with use of conventional breeding methods and MAS for QPM line conversion were estimated using a spreadsheet-based budgeting approach. First, field and laboratory operations involved in conventional and MAS breeding were identified and costed out. Second, representative conventional and MAS breeding schemes were identified. Third, the unique laboratory and field parameters set forth in each breeding scheme were used to calculate the total cost of implementing that particular scheme. Dreher, K., M. Morris, M. Khairallah, J-M. Ribaut, S. Pandey, G. Srinivasan ii ABSTRACT (CONTINUED) Results of the budgeting exercise suggest that currently at CIMMYT, the relative costeffectiveness of conventional breeding methods as compared to MAS for QPM line conversion differs depending on the circumstances. In cases where it is possible to identify segregating materials by visually inspecting ears in the field, conventional breeding methods can be very cost-effective. But in cases where visual selection is not possible, use of molecular markers can lead to significant cost savings. CIMMYT’s experience with MAS parallels the experience of many other breeding programs. Even though MAS has come to play a prominent role in the field of plant breeding, for many practical applications the economics of MAS are still being worked out on a case-by-case basis. The continuing uncertainty concerning the utility of MAS in specific applications should not give rise to undue pessimism, however. Everything that made MAS attractive in the first place still holds true; the key to successfully integrating the technology into applied breeding programs will lie in identifying applications in which molecular markers offer real advantages over conventional breeding methods. MAS should be able to offer significant advantages in cases where phenotypic screening is particularly expensive or difficult, including breeding projects involving multiple genes, recessive genes, late expression of the trait of interest, seasonal considerations, or geographical considerations. In addition to reducing the cost of breeding, MAS also has the potential to generate time savings. Depending on the benefits that a breeding program realizes from earlier release of its breeding products (which typically differ between the private and public sectors), the value of these time savings can be enormous—often justifying the additional cost involved in using MAS. Continuing refinement of molecular marker technologies will make MAS cheaper and more effective in coming years, but at the same time it would be a mistake to assume that marker technologies represent a “silver bullet” solution to every breeding problem. As this case study has revealed, conventional breeding methods still provide a cost-effective option for many types of breeding project, and they will continue to be attractive in the future.