A COMPARISON OF THE ECOVALENCE AND THE VARIANCE OF RELATIVE YIELD AS MEASURES OF STABILITY

Yield stability is an important trait of crop cultivars. There are dif ferent concepts and measures of stability, and new ones are constantly being proposed, leaving the practitioner with an ever growing collect ion of measures to chose from. In order to facilitate the choice it is useful to study the relationship between stability measures. This pap er compares the well known ecovalence to a new measure, the variance o f relative yields. It is argued that under rather restrictive conditio ns the new measure is essentially equivalent to the ecovalence, while in most cases it displays an undesirable dependence on genotypic mean yield. It is concluded that the ecovalence is generally preferable.