Although enhancement of sink capacity with heavypanicle
is an important approach to the improvement of
yield potential in super rice (
Oryza sativa
L.) breeding,
environmental fluctuations may greatly affect fertilization
and grain filling of heavy-panicle rice. Here, we
investigated the response of heavy-panicle rice varieties
to high temperature at flowering and grain filling stages
under field conditions, with a focus on spikelets positions
on the panicle. Six varieties each with four staggered
sowings were grown under various climatic conditions,
and thus their flowering stages and grain filling stages
experienced high or normal temperature weather scenarios.
When rice varieties grown under high temperature,
spikelet fertilities increased in all tested varieties. Grain
weights of varieties CW2221, K106 and R-2 under high
temperature stress showed an average of 10.81% increase
compared with normal temperature, whereas ‘C418’,
‘J1307’ and ‘Xianghui210’ decreased by 15.21%. Head
milled rice rates significantly decreased, but chalky
grain rates and chalkiness degrees significantly increased
under high temperature. We further demonstrated that
the effects of high temperature on spikelet fertility, grain
weight and grain qualities were correlated with grain
positions. These results indicate that understanding
effects of high temperature on grain weight and quality
in heavy-panicle rice varieties is a key factor for super
rice breeding in the future.
