Flowering under short days: juvenile period and inductive phase estimates in soybean genotypes.

Abstract

The success in adapting Brazilian soybean cultivars to low latitude regions was attained thanks to the incorporation of the late flowering trait into the germplasm used by breeders. The objective of the presente work was to establish a methodology to estimate the juvenile period and the inductive phase of soybean genotypes. A total of 11 cultivars representing the successful trajectory of the genetic progress of soybean breeding in Brazil were used. The experiments were done under greenhouse conditions in the city of Cambé, PR, Brazil. Seeds were germinated at 14 days intervals and, after emergence, the plants were subjected to continuous light for periods varying from 0 to 56 days. The number of days for flowering under the diferente light regimes and sowing times was evaluated. A decreasing exponential regression model was adjusted, through the differences between the maximum and minimum partial points of the function, in order to estimate the juvenile period. Results showed that, except for ‘Viçoja’, all the other cultivars fitted into the model. ‘Paraná’ had an almost linear behavior with the equilibrium point at the zero value. ‘Paranagoiana’ was the cultivar with the largest and most significant juvenile period while ‘Viçoja’ and ‘ÚFV-1’ showed the lowest juvenile period. The methodology developed appeared to be robust and was validated by the known behavior of such cultivars when sowed under short day conditions that occurs either in low latitudes or anticipated and delayed sowing seasons