Rice research turns focus on Asia’s chronic droughts

After decoding the rice genome, keeping one of the world’s most important cereals productive despite chronic droughts is now a key focus of global research, the International Rice Research Institute (IRRI) says.

The Philippines-based IRRI said a study this year concluded that dry spells, more than floods or typhoons, is the primary recurring threat in Asia, where around a fifth of all the rice-growing areas are drought-prone.

"Coping with recurrent drought is part of life for millions of Asia’s rural poor," IRRI said in the latest edition of its journal Rice Today.

In 2004, widespread severe drought in much of Asia led not only to agricultural production losses of hundreds of millions of dollars, but also pushed millions of people into poverty, it added.

Since then, IRRI research has identified many rice varieties that not only produce high yields in good conditions but alsotwo to three tons per hectare under conditions that are so dry many popular varieties return less than a ton per hectare, it said.

Cross-breeding varieties has produced the first generation of so-called "aerobic rice" that grows on dry soil like maize, instead of on flooded paddies, it added. This rice was produced by crossing modern high-yielding varieties that respond well to fertilizer with traditional but low-yield ones that grow in dry soils.

Some lines are now being field-tested in drought-prone areas of South and South Asia, IRRI said.

Following the breakthrough sequencing of the rice genome, IRRI scientists have also created more than 40,000 varieties where chemicals or radiation were used to knock out random segments of the rice chromosome.

The resulting plants, which IRRI calls "deletion mutants," are screened under drought stress in the field, or with the application of drought-related hormones in the laboratory, to identify drought-tolerant or drought-susceptible mutants.

Work is also under way to identify which deleted genes are responsible for this effect, it added.

The rice plant traditionally requires lots of water during its reproductive stage. If conditions are dry, it reduces production of gibberellin, the hormone that stimulates the panicle, or the flower, to fully emerge from the leaf sheath, as well as pollen release. This results in reduced yields.

The impact of dry spells is often felt throughout the local Asian region, effecting the local economy, the paper quoted IRRI senior agricultural economist Sushil Pandey as saying. — AFP