The Bean Program used a three-stage progeny evaluation strategy (Figure 7). In the first stage, the Bean Team Nursery (VEF), was a uniform, multidisciplinary evaluation of materials for adaptation and resistance to priority diseases and insects. Approximately 1000 lines entered this nursery each year. The selected materials (approximately 300 lines per year) passed to the second stage of evaluation, the Preliminary Yield Trials (PD). In these, the lines underwent an almost complete evaluation, including resistance to diseases and minor pests, quality factors and Nitrogen fixation. The best materials selected from the PDs (approximately 100 lines per year) were included in the International Bean Yield and Adaptation Nursery (IBYAN).

This evaluation scheme for improved bean materials allowed the free flow of genetic materials from national programs to CIAT and vice versa. In the initial phases of this evaluation program (1976-77), the materials incorporated were germplasm bank selections and established varieties from Latin American countries. Since 1978, the representation of new genetic lines has steadily increased. For example, by 1981, more than 80 percent of the bush bean entries in IBYAN were improved lines from the Bean Program.

The Program supplied genetic materials to collaborating national programs for any stage of development at which they wished to use them. This stage varied according to the type of limiting factors faced by the national programs, as well as their human and physical resources. CIAT supplied some countries with genetic lines that could be used immediately as varieties (Cuadro 6). In other countries, the materials best suited to the needs of the national programs were early generations of segregating populations, often from crosses made specifically to meet the needs of those programs.