Abstract:
More than 50% of the world's population consumes rice as the staple food while Australia
produces 1.2 million tons of rice annually and feeding about 40 million people daily. Future
climate change predicts increase temperature and reduced rainfall patterns which could
severely affect rice production. As rice yield heavily relies on spikelet fertility factor, this study
predicted the spikelet fertility factor with response to different rice varieties in different future
climatic scenarios (related to increasing temperature, elevated atmospheric CO2 concentration
and rainfall) using APSIM–Oryza model at two different sites, Griffith in New South Wales and
Kununurra in Western Australia. Varieties used at Griffith were Quest, Amaroo, and Langi
representing early, mid and late maturity types, respectively. Only single variety (IR72) was
used for Kununurra region. Five incremental changes of temperature were 0 (base), +1, +2, +3,
+4oC with amalgamation of five rainfall changes (+10, 0, -10, -20, and -30%) used in the
simulation to characterize the variety of projected climatic changes predicted for Australia over
the following 60 years. The corresponding CO2 concentrations connected with the above
temperature levels were 380, 435, 535, 640 and 750 ppm. In all varieties of Griffith (Amaroo,
Langi, and Quest),spikelet fertility factor showed an increasing trend up to 1-2 oC temperature
increase which could be due to CO2 fertilization effect. Further increase in temperature caused
a steady decline in spikelet fertility factor, with short-season variety ‘Quest' affected least. In
contrast to the Griffith Riverina region, in Kununurra, spikelet fertility factor changed
negatively with the temperature increase, decreasing from 0.55 to 0.25.These results specify
that warmer temperatures are likely to increase spikelet sterility. Adaptations may comprise
using shorter season varieties and changing planting dates. Therefore future rice breeding
strategies should focus on developing short season varieties with higher spikelet fertility to
cope up with higher temperature effects in the future.
