Dancing spikes and fascinating anthers A short time travel through the wheat florets
Hybrid wheat production
The growing world population makes it
necessary to increase the yield of important crops in order to be able to feed
people in the future. Plant breeders and scientists are working on different
approaches to solve this problem. One possibility is to take advantage of the
hybrid effect.
Hybrids are the progenies after crossing
two different plant genotypes. These hybrids are characterized by having a
higher yield and better yield stability compared to their parents. But not only
that: they are more robust in the face of extreme weather conditions, which
could become more frequent as a result of climate change. In many crops such as
corn and barley, commercial success has already been achieved with hybrids.
Wheat has also been in the focus of scientific interest for decades. However,
it has not yet been possible to develop an efficient system for hybrid wheat
production. For this reason, the IPK Leibniz Institute is working closely
with plant breeders in the HyFlor project. The aim is to study the flowering
biology of wheat in more detail. A fundamental understanding of the flowering
traits of wheat, could have the potential to revolutionize the hybrid system in
wheat.
Plant Architecture
In this context, wheat flowering is being intensively studied
in Thorsten Schnurbusch's "Plant Architecture" research group. His PhD student Constanze Schmidt has already observed the
flowering process in more detail using targeted close-up images and videos.
Constanze has completed her Bachelor's and Master's degrees in biology, and is
now writing her PhD thesis in agricultural sciences.
First of all, we should clarify the most important terms.
Wheat spike
A wheat spike consists of up to 40
spikelets. Each spikelet has two glumes that cover the two to five florets.
Spikelet
Each spikelet has two glumes that enclose the two to five florets.
Floret
In each floret, the ovary is located
between the lemma and the glume. Directly attached to it are the lodicules
which are responsible for opening the floret. Attached to the ovary are the two
feathery stigmas where the pollen must be deposited. The pollen itself is
located inside the anthers, which are attached to the base of the floret by
thin filaments. In wheat, each individual floret has three anthers.
Fascinating anthers
In time-lapse videos, the flowering process
could be observed in detail. First, the three anthers open and release the
mature pollen inside the flower. This directly pollinates the own stigma.
Second, the filaments elongate rapidly - this can even be observed visually. In
a third step, the lodicules swell. This pushes the lemma and palea apart and
creates a small gap at the tip of the floret. The anthers pass through this gap
until they hang from the filaments and dangle out of the floret.
Dancing spikes
After a short time (about 30 minutes), the
lodicules collapse and the floret closes again. The anthers remain outside, and
empty completely by (wind) movement. If other wheat stigmas are nearby at this
time and are receptive, they can be pollinated by the free pollen. Wheat
pollen, however, is very heavy compared to other crops, and cannot be
transferred very far by the wind.
Crossing
For the crossing of two plant lines, the
pollen from a male plant must be transferred to the stigma of the female plant.
Wheat is mainly a self-pollinator. This means that in a floret there are
usually both the male and female organs, and a plant fertilizes itself. In this
case, the anthers correspond to the male organs, and the ovary corresponds to
the female organs. For a successful hybrid production this means that pollen
production must be prevented in the female plant. This can be done by
mechanical removal of the anthers, or by so-called gametocides. These are
sprayed on the plants, and prevent further pollen development. Sterilization of
male flowering organs can also be done by mutations.
Hybrid production of wheat requires two things: the availability of mature pollen and receptive female lines. In the absence of their own pollen, the females need pollen from other plants in order to be fertilized and thus form grains. If successful pollination does not occur, the plant's own reproduction fails.
Hybrid production of wheat requires two things: the availability of mature pollen and receptive female lines. In the absence of their own pollen, the females need pollen from other plants in order to be fertilized and thus form grains. If successful pollination does not occur, the plant's own reproduction fails.
State of research
The biggest challenge in hybrid wheat
production is to establish the wheat as a self-pollinator to also pollinate
other wheat plants or to be pollinated by other plants. Therefore, we are
currently looking for traits that represent an excellent male or female. In
other words, which characteristics are crucial for maximum cross-pollination to
take place? On the male side, we need optimal pollen availability outside the
floret. On the female side, we are looking for a good combination between a
large opening angle (so that as much pollen as possible can be taken up) as well
as a long duration of receptivity (so that pollen can be taken up for as long
as possible). In the future, we ultimately want to describe in more detail
which traits are most important and which lines are suitable for hybrid
production.
A production of the
IPK Leibniz Institute
Text
Constanze Schmidt
Christian Schafmeister
Time-lapse photography
Constanze Schmidt
Videos | Photos | Grafic
Andreas Bähring
Constanze Schmidt
© 2022
IPK Leibniz Institute
Text
Constanze Schmidt
Christian Schafmeister
Time-lapse photography
Constanze Schmidt
Videos | Photos | Grafic
Andreas Bähring
Constanze Schmidt
© 2022
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Dancing spikes and fascinating anthers
Hybrid wheat production
Plant Architecture
First of all, we should clarify the most important terms.
Wheat spike
Spikelet
Floret
Fascinating anthers
Dancing spikes
Crossing
State of research
