Photoperiod response and floral transition in sorghum

Abstract

Sorghum is a short day plant with strong photoperiod response and its cultivation for grain in temperate regions necessitated the development of photoperiod insensitive mutants that can flower rapidly in the long days of summer. Wild type genotypes grow vegetatively in summer accumulating significant biomass before floral transition ensues during the shorter days of fall. Thus, photoperiod insensitive mutants are grown for grain production while photoperiod sensitive wild type genotypes are grown for forage and biomass feedstock production in the United States. However, the molecular mechanism of photoperiod response and floral transition is poorly understood in sorghum. We have previously reported 3 FLOWERING LOCUS T homologues (SbFT1, SbFT8 and SbFT10) that serve as the ultimate mediators of photoperiod response and floral transition, but more work remains to be done to clearly define the molecular function of the upstream regulatory factors. One of the major QTL that accounts for 85% of the flowering time variation, which was reported to be encoding the PRR37 protein is now debated to be encoding the SbFT12 protein, raising further questions as to how SbFT12 may regulate sorghum florigens. Further molecular analyses will uncover the true nature of the day length sensors in sorghum and the mechanisms of their interactions with florigens to modulate photoperiod dependent vegetative growth and floral transition. KEYWORDSFlorigen; flowering time; long day; photoperiod; photoreceptor; SbFT; short day; sorghum Sorghum (Sorghum bicolor L. Moench) is a multipurpose crop grown for food, feed and fuel in tropical, subtropical, temperate, and semi-arid regions of the world. It is the fifth most important cereal worldwide after maize, wheat, rice, and barley. As a short day tropical species, sorghum exhibits substantial photoperiod sensitivity and this has important implication in its agronomy in temperate regions. Sorghum flowers rapidly in short day photoperiods 1 but the extended light period in temperate regions allows more photosynthesis and extensive vegetative growth during the warm months of summer. In the United States and other temperate regions, breeders have selected for mutants that flower rapidly independent of day length for grain production while keeping the photoperiod sensitivity trait in forage and biomass producing genotypes to allow more biomass accumulation in the long summer days. Thus, whether a given sorghum germplasm is grown for grain or biomass production in temperate regions depends on its photoperiod response behavior. However, the molecular mechanism of photoperiod response in sorghum and its relationship to developmental programs is poorly understood. Flowering time is obviously a key feature of photoperiod response. While photoperiod insensitive genotypes flower early irrespective of day length, photoperiod sensitive genotypes flower rapidly in short days (SDs) but flower very late in long days (LDs). But floral transition is not the only trait affected by photoperiod. Other devel...

Phenological and physiological evaluation of first and second cropping periods of sorghum and maize crops

“…In maize plants, the possible causes of plant height reductions may include the temperature factor, which is already well known for reducing growth, and consequently productivity, in these plants (Rymen et al, ). For sorghum, there is also sensitivity to the photoperiod, which leads to decreases in plant height (Wolabu & Tadege, ). Moreover, the final height of the plants is strongly correlated with the length and number of internodes, and these can be reduced by lower water availability, a situation that actually occurred in the second cropping (Fujii, Nakamura, & Goto, ; Yamamoto, Guo, & Ninomiya, ).…”

“…In maize plants, the possible causes of plant height reductions may include the temperature factor, which is already well known for reducing growth, and consequently productivity, in these plants (Rymen et al, 2007). For sorghum, there is also sensitivity to the photoperiod, which leads to decreases in plant height (Wolabu & Tadege, 2016 (Borrell et al, 2014). More limiting resource conditions promote the reduction in leaf area, as well as the genetic aspects of the plant itself (Fender, Mantilla-Contreras, & Leuschner, 2011).…”

Transcriptional Analysis of Flowering Time in Switchgrass

“…Some components of the photoperiod and autonomous pathways have been identified in switchgrass [33]; however, investigations in sorghum, another high biomass crop, have yielded more pieces of the flowering pathway in grasses. Three well-characterized maturity loci in sorghum, Ma1, Ma3, and Ma6, harbor floral repressors that confer photoperiod sensitivity [34]. Ma1 corresponds to SbPRR37, the ortholog of Arabidopsis PRR7 [35]; PHYB is the gene at the Ma3 locus [36]; and SbGhd7, the ortholog of rice Ghd7, was identified as Ma6 [37].…”

The Effect of Single and Combined Use of Gamma Radiation and Ethylmethane Sulfonate on Early Growth Parameters in Sorghum

“…The use of artificial mutagenesis emulates the natural process of spontaneous mutation by maintaining the genetic status quo and without introducing alien genes, unlike in genetically modified organisms [ 7 , 8 , 9 ]. Induced mutation increases the proportion of genetic variation multi-fold (1000 to a million times) [ 10 , 11 , 12 ]. Artificial mutagenesis coupled with innovative breeding approaches such as speed breeding techniques and use of single seed descent selection method can deliver desired cultivars with a relatively shorter breeding cycle [ 13 , 14 , 15 ].…”