title: Inheritance of kernel row number, a multicategorical threshold trait of maize ears.
abstract: Information  about the inheritance of threshold traits is scarce, especially in plants. We  examined the genetic control of kernel row number in maize (Zea mays).  Knowledge of this inheritance is especially important because it is a primary  component of grain yield. This trait has a discontinuous distribution.  Characters like these are conceptualized as threshold traits. Crosses were made  between the inbred line Geneze 3 (G3) with many kernel rows and the inbreds  Argentino IV (A4) and Dente de Cravo (DC), with fewer kernel rows. The F(1) and F(2) generations  and the backcrosses BC(11) and BC(21) were  obtained for the combinations G3 x A4 and G3 x DC. These populations were  evaluated under field conditions, and the kernel row number was determined by  direct counting of approximately 14, 140 and 75 ears for the F(1), F(2) and  backcrosses, respectively. Genetic control was determined through estimates of  generation means and variance analysis and was also performed by Wright's  method for threshold traits. It was found that genetic control is predominantly  due to additive alleles. The component a, was greater than zero,  additive variance was positive and the variance of dominance did not differ  from zero. In the F(2) generation, the  range of the kernel row number was 10 to 28 in G3 x A4, while in G3 x DC it was  12 to 26. Inheritance of the number of kernel rows, estimated by the two  methods, gave similar results. This correspondence is due to adjusting of the  data to the normal distribution.
authors.affiliation: Programa de Pós-Graduação em Genética e Melhoramento de Plantas, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, Piracicaba, SP, Brasil. fernandohtoledo@gmail.com
authors.forename: F H R B
authors.initials: FH
authors.lastname: Toledo
authors.forename: M A P
authors.initials: MA
authors.lastname: Ramalho
authors.forename: G B
authors.initials: GB
authors.lastname: Abreu
authors.forename: J C
authors.initials: JC
authors.lastname: de Souza
mesh_terms: D000483:Alleles; D001947:Breeding; D003433:Crosses, Genetic; D010641:Phenotype; D019655:Quantitative Trait, Heritable; D012639:Seeds / Q000235:genetics*; D003313:Zea mays / Q000235:genetics*