The C4 Model Grass Setaria Is a Short Day Plant with Secondary Long Day Genetic Regulation

Abstract

The effect of photoperiod (day:night ratio) on flowering time was investigated in the wild species, Setaria viridis, and in a set of recombinant inbred lines (RILs) derived from a cross between foxtail millet (S. italica) and its wild ancestor green foxtail (S. viridis). Photoperiods totaled 24 h, with three trials of 8:16, 12:12 and 16:8 light:dark hour regimes for the RIL population, and these plus 10:14 and 14:10 for the experiments with S. viridis alone. The response of S. viridis to light intensity as well as photoperiod was assessed by duplicating photoperiods at two light intensities (300 and 600 μmol.m-2.s-1). In general, day lengths longer than 12 h delayed flowering time, although flowering time was also delayed in shorter day-lengths relative to the 12 h trial, even when daily flux in high intensity conditions exceeded that of the low intensity 12 h trial. Cluster analysis showed that the effect of photoperiod on flowering time differed between sets of RILs, with some being almost photoperiod insensitive and others being delayed with respect to the population as a whole in either short (8 or 12 h light) or long (16 h light) photoperiods. QTL results reveal a similar picture, with several major QTL colocalizing between the 8 and 12 h light trials, but with a partially different set of QTL identified in the 16 h trial. Major candidate genes for these QTL include several members of the PEBP protein family that includes Flowering Locus T (FT) homologs such as OsHd3a, OsRFT1, and ZCN8/12. Thus, Setaria is a short day plant (flowering quickest in short day conditions) whose flowering is delayed by long day lengths in a manner consistent with the responses of most other members of the grass family. However, the QTL results suggest that flowering time under long day conditions uses additional genetic pathways to those used under short day conditions.

Climate Warming Does Not Always Extend the Plant Growing Season in Inner Mongolian Grasslands: Evidence From a 30‐Year In Situ Observations at Eight Experimental Sites

“…chinensis as an example, the multiyear average AT over the growing season ranged from 2,206 at Ergun to 2,732 degree days at Xilinhot (Table ). Previous studies indicated that the day length affected the phenologies of certain grasses (Benedict, ; Cookson et al, ; Doust et al, ). The mean day length over the growing season at Ergun was 0.6 hr longer than at Xilinhot, suggesting that L .…”

Optimization of Phenotyping Assays for the Model Monocot Setaria viridis

“…Similarly, to study the effect of different stress conditions on adult plants, control plants should grow in conditions that result in optimal growth and development. It is known that Setaria growth and development is extremely sensitive to photoperiod and temperature ( Swanton et al, 1999 ; Doust et al, 2017 ). As expected, huge differences in overall plant architecture were observed between plants grown in controlled environment growth chambers versus controlled environment greenhouses.…”

Domestication and Improvement in the Model C4 Grass, Setaria

“…Thus selection on flowering time is unlikely to be a direct response to domestication but is best considered as a target for crop improvement. However, flowering time and photoperiod sensitivity also interact with other important traits, such as branching, height and biomass ( Doust, 2017 ; Doust et al, 2017 ), making it relevant to discuss here.…”

“…A recent multiplexed shotgun genotyping (MSG) resequencing analysis of 439 RILs (derived from a cross between foxtail millet accessions Zhanggu and A2) under short (<12 h light) and long photoperiods (>14 h light), uncovered a total of 59 QTLs for 14 agronomic traits which were influenced by different photoperiods ( Zhang K. et al, 2017 ). Doust et al (2017) examined flowering responses in short (8 or 12 h light) and long (16 h light) photoperiods in a QTL mapping population, and demonstrated differences between short and long day regulation, with the 8 and 12 h photoperiods sharing QTL on chromosomes 4 and 5, and the 12 and 16 h having a shared QTL on chromosome 8. In addition there were QTLs on chromosomes 2 and 3 that were unique to the 16 h photoperiod.…”