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Abstract :

Flowering time is fundamental to the local adaptation and productivity of crop species. The timing of flowering is determined by rates of development and phase transitions, which are controlled by integrated networks of external (environment) and internal (plant) signals. Domesticated maize, originating from a tropical teosinte (Z. mays ssp. parviglumus), was spread globally by adapting its flowering time to novel environments. Tropical maize varieties require a short-day/long-night cycle for reproductive transition, while long-day conditions prolong this transition, giving rise to photoperiod sensitivity (PS). Elimination of PS enabled the adaptation of maize to long-day growing seasons in the temperate zone, such that temperature has become the main driver for flowering time in temperate varieties. Thus, historical selection has reshaped the phenotypic space for flowering time regulation in maize. In the context of global warming, where rising temperatures will hasten flowering times, maize yields are projected to decline. Reintroducing partial PS in temperate breeding pools could counteract these effects and expand the phenotypic space for adapting maize to climate change. To exploit the potential of PS, the ecophysiological response of flowering time across field environments has to be better understood. New knowledge is needed about variation in the physiological reaction norm for flowering time, the effects of PS alleles in temperate genetic backgrounds, and whether there is broad scale potential for PS as a novel climate adaptation.