COMBINING ABILITY IN MAIZE RACES BRED BY LIMITED BACKCROSS. I: AGRONOMIC TRAITS

Abstract

Among maize races (Zea mays L.) there are agronomic differences that were developed though evolution in different geographic sites. when races are crossed differences in combining ability appear. Most races used in this study are tall, a trait associated with root and stalk lodging. In this research we estimated the general and specific combining ability (GCA and SCA), of ten maize population regarding eight agronomics traits. The diallelic crosses were made among ten maize landrace populations bred by the limited backcross method (RC₁-F₇), and then evaluated under irrigation in three locations; data were analysed according to Griffing’s Model 2. The combining ability was reduced, most particularly the SCA. We detected convergence towards the commercial plant type. So that yield was similar among the 45 crosses and among parents. Therefore, we suggest to restore the genetic diversity both in the general and specific combining ability effects, and to substitute the fraternal crosses by self pollination.