What's happening at IRRI
Thursday, March 17, 2016, 01:15pm - 02:15pm
Moving rice out of the water: a huge evolution for the plants
by: Benoit Clerget
Senior Scientist - Crop Physiology
Crop and Environmental Sciences Division
Water is a limited resource in many areas in Asia areas where rice is grown as a staple. A crop of flooded rice consumes at least twice the water needed by any other cereal crop. Much-improved water efficiency while maintaining yield potential will be a high priority for future rice crops in many situations. However, IRRI’s improved indica rice varieties for tropical regions do not like this evolution, yielding less when grown without a water layer above the soil (flooded) even when soil is maintained close from water-saturation (aerobic conditions).
Since 2011, we have been comparing the behavior of rice plants under flooded and aerobic water management. We found that in direct-seeded aerobic crops, the rate of plant development decreased because a specific reaction to transplanting was lost and, very marginally, because of the effects of watering and sowing density. Stems were always smaller, and with smaller leaves and panicles. Tiller density in the direct-seeded crop was higher at maximum tillering but similar with the flooded crop at harvest time, thus, not compensating for the smaller panicles.
Possibly a key trait in plant adaptation to aerobic conditions, rate of plant development was studied more closely and its variability evaluated in a 300-variety core collection planted each in flooded and aerobic environments. Grain yields of 8–9 t/ha were regularly observed in the flooded crop against 6–7 t/ha in the aerobic crop. Yield under aerobic conditions came to 8 t/ha once, due to a high-quality seedbed that induced better plant growth from seedling stage to harvest.
At this stage of the work, questions about reduction in size of every organ and regulation of tillering appear crucial in improving the yield potential of future varieties for aerobic conditions. In addition, adapted practices in crop management, such as seedbed preparation or weed control, must be taken into account and applied.
Havener Auditorium, International Rice Research Institute, Los Baños, 4030 Laguna, Philippines