Scientists discover how crops use the length of the day to decide when to flower

Scientists at the John Innes Centre (JIC) [1] in Norwich, UK, report today a breakthrough in understanding how crop plants use daylength to ensure they flower at the right time of year. In an article published in the international journal Science, they describe a gene that controls how barley reacts to the length of the day and thus controls when it flowers.

Most plants flower at a particular time of the year and researchers have known for a long time that plants use cues from their environment to control when they flower. Many crops, including barley, react to the length of the day (daylength) and use this to determine their flowering time.

“Different varieties of barley (and other crops) respond to daylength in different ways and this has been used to breed varieties adapted to grow in different farming environments” said Dr David Laurie (Project Leader at JIC). “Our result is exciting because for the first time we have identified the gene (called Ppd-H1) [2] that controls this very important response and now understand how plants monitor daylength. This should help breeders who are breeding new varieties for new environments and changing agricultural conditions – caused by global climate change.”

Some barley varieties respond very quickly to the lengthening days in spring and so flower early in the summer. Others respond much more slowly and flower later. Early flowering is an advantage in places where the summers are hot and dry, such as the Mediterranean, because the plants can complete their life cycle before they are exposed to the stresses of high summer. In places like England, where the summers are cool and wet, late flowering is an advantage because the longer growing period allows the crops to deliver higher yields.

“Now we have identified the gene we will be able to find out how many versions of this gene there are in barley and which environments they match”, said Dr Laurie. “This will give us a better picture of the history of our crops and help us understand how crops have been bred for different environments around the world. Our studies suggest that the same gene may be important in wheat and rice. If this is true, then it will prove to be a gene that has been very influential in the process of domesticating wild plants to bring them into agriculture.

[1] The John Innes Centre

The John Innes Centre (JIC), Norwich, UK is an independent, world-leading research centre in plant and microbial sciences. The JIC has over 800 staff and students. JIC carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council.

[2] Ppd-H1 (Photoperiod H-1)

The Ppd-H1 gene is part of a genetic pathway that controls barley’s response to daylength.

Plants, like humans and many other organisms, have an internal clock. In barley this clock regulates the daily activity of a gene called CO (constans) so that CO activity increases to a peak and then decreases on a daily cycle. Peak CO activity only coincides with the plant being exposed to daylight if the length of the day is long enough. When this happens CO activates a gene called FT (flowering locus T) which stimulates flower formation.

The Ppd-H1 gene affects the timing of CO expression during the day. A variant of the gene found in late flowering barley causes the peak of CO expression to be shifted to later in the day. This requires a longer day length to enable the FT gene to be expressed and so delays flowering until longer days.