An easy way to assess photoperiod sensitivity in sorghum: Relationships of the vegetative-phase duration and photoperiod sensitivity

Abstract

Sorghum (Sorghum bicolor) landrace varieties show very
\nlarge variation for the duration of their vegetative phase,
\nranging from 50 to 300 days depending on the sowing
\ndate (Miller et al. 1968). This variation is linked with the
\nduration of the rainy season in their place of origin
\n(Curtis 1968). Late sorghum varieties are known to be
\nhighly photoperiod-sensitive and, for a given variety, the
\nflowering date remains more or less constant independent
\nof sowing dates, which in the tropical areas of the
\nnorthern hemisphere occur anytime between May and
\nJuly. Even though the importance of matching sorghum
\nflowering date to the end of the rainy season has long
\nbeen known, relatively little has been done to improve
\nthese photoperiod-sensitive varieties until the past
\ndecade. The lack of new, improved sorghum varieties
\nable to respond to the increased soil fertility in cotton
\n(Gossypium spp) systems of Burkina Faso and Mali has
\nmost recently raised the need for this type of research,
\nand breeding programs are currently addressing this
\nobjective (Bazile et al. 2003).