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Genetic analysis of tassel size and leaf senescence and their relationships with yield in two tropical Lowland maize populations Guei, R.G. & Wassom, C.E. Abstract Primary tassel branch number, tassel weight, and leaf senescence are among plant traits which affect maize plant yielding efficiency. Two random mating tropical maize populations were used to estimate genetic components of variance and heritability, and to quantify the amount of genetic variability. Full-sibs within half-sib groups were developed using the mating Design I, and were evaluated at two locations for 2 seasons in Mexico. Results showed that large amounts of genetic variability were present in both populations for all traits. Additive genetic variance was greater in magnitude than dominance variance. Negative phenotypic and genotypic correlations were found between tassel size, leaf senescence, and yield. Selection based on these traits may be appropriate for increased yield. Overall, the inheritance of the traits measured depended on the genetic background of the population and the environmental conditions. Keywords Additive variance, dominance variance, genetic variability, heritability, leaf senescence, tassel size

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Guei, R.G. & Wassom, C.E. Résumé Le nombre d'embranchements primaires de la fleur male, leur poids et la senescence des feuilles font parti des caracteristiques de la plante de mais qui affectent l'efficience du rendement. Deux populations de mais d'origine tropical croisees au hasard ont ete utilisees pour estimer les composantes de la variance genetique et de l'heritabilite, et pour quantifier l'ordre de grandeur de la variabilite genetique. Des groupes de vrais freres a l'interieur des demis freres ont ete developpes en utilisant le dispositif I de croisement, et ont ete evalues dans deux localites pendant deux saisons au Mexique. Les resultats demontrent que la variabilite genetique etait elevee dans les 2 populations pour toutes les caracteristiques mesurees. Mais la variance genetique additive etait plus elevee que la variance du type dominant. Les correlations phenotypiques et genotypiques etaient negatives entre les caracteristiques mesurees et le rendement. La selection basee sur ces caracteristiques pourrait ameliorer le rendement, et leur transmission serait fonction du determinisme genetique de la population et des conditions environnementales. Mots Clés Heritabilite, variabilite genetique, variance additive, variance dominante, senescence des feuilles

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