Changes in Floral Induction Genes During Photoperiod Induction in Flowering and Reluctant-to-Flowering Sugarcane Varieties

The production of fertile inflorescences is essential to make crosses for the development of new varieties of sugarcane. Within the Saccharum species and commercial hybrids of sugarcane, there is a wide range in flowering times and some varieties rarely flower; this can make it impossible to achieve some desired crosses. While photoperiod houses can assist with inducing some varieties to flower or synchronise flowering, understanding the expression of genes within the flowering pathway could provide an explanation for such variation. To this end experiments were designed to assess the photoperiod conditions within a controlled environment facility and measure changes in expression of 18 genes associated with flowering during the initial four weeks of the floral induction period at three time points across the day-light cycle. Two sugarcane varieties were selected for their differences in flowering propensity, Q208 and Q183, flowering and non-flowering, respectively. The 18 genes examined were associated with photoperiod perception, the circadian clock, the floral pathway, and floral meristem identity. Of these, 16 were detected and showed differences in expression during the light cycle and over the 4 weeks under photoperiod induction in Q208. The assessment of a subset of those genes in Q183 showed higher expression levels of ShLHY , ShCO and ShTFL1 in Q183 than Q208. One of the genes, TFL1 is a known flowering inhibitor of the penultimate step prior to floral induction. These gene profiles build on the proposed sugarcane flowering pathway and highlight key genes for manipulation to promote and synchronise flowering to assist sugarcane breeding programmes.