Cycle segregation in crossings of landrace corn populations

Studies aimed at elucidating the gene actions that control traits little investigated in the plant breeding area are important for the choice of the parents to be crossed. The present study aimed to evaluate the segregation and reciprocal effects, relating to genetic effects prevalent in demanding thermal sum of land racescorn populations contrasting for this trait. Thus, we used three contrasting populations for thermal sum, (1 - super-early, 2 early and 3 Late), totaling a set of six crossovers, with the following combinations of population: 1x2, 1x3, 2x1, 2x3, 3x1 and 3x2. The crosses were performed in complete diallel scheme. In the first year, artificial crosses were made and in the second year, sowing of hybrid populations together with its genitor populations was carried out to assess the requirement of thermal sum of the crosses. The findings showed that: selection of populations for thermal demand should be considered the reciprocal effects. Additive and nonadditive gene actions reveal importance to the thermal sum trait. To reduce the cycle, it is necessary that the population used as female progenitor presents late cycle and male progenitor early cycle. Crosses between early-cycle females and super-early cycle males, or super-early cycle females and early-cycle males, generate populations with higher thermal requirement.