Participatory maize breeding (PMB) was initiated in Portugal in 1984 by Dr. Silas Pêgo at Sousa Valley. The VASO project was intended to answer the problem facing small farmers, i.e. yield increasing without losing the parameters defined by farmers in polycropping systems maintaining the quality traits under a sustainable agriculture. This model is based on the Integrant Philosophy, which contrasts with the Productivist Philosophy. The Integrant Philosophy is intended to fit a multicrop agricultural system that corporate agriculture does not reach due to incipient market conditions. The present document intends to be a contribution to: 1) the study of 20 years of VASO; 2) methods used in PMB for Portuguese open-pollinated maize varieties and 3) present research.