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Gene helps rice grow in phosphorus-poor soils

This post has been corrected. See note at the bottom for details.

Rice, like all plants, needs phosphorus to grow. But there’s a problem for this crop, the most important calorie source in Asia. Much of the soil it’s grown on is low in phosphorus, and yields suffer as a result.

What’s more, world supplies of phosphorus -- it comes from phosphate rock -- are expensive for poor farmers and won’t last forever.

So it would be very helpful if rice plants could be altered to tolerate low phosphorus levels. Scientists in the the Philippines, Japan and Italy have now reported doing just that.

The trick was to go back to rice varieties from east India that are known to grow better than most in poor soils.

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Scientists had identified a strain called Kasalath that they knew could tolerate phosphorus deficiency, but they didn’t know what was behind it. They had narrowed down the effect to a particular part of the genome, though -- and DNA-sequencing later revealed that there was a gene in this region that didn’t exist in the previously sequenced rice genome (a Japanese variety called Nipponbare) and other varieties that did poorly in phosphorus-deficient soils.

In their study published in Nature, Rico Gamuyao, of the International Rice Research Institute in the Philippines, and colleagues:

a) found that the gene, which they call PSTOL1, sprang into overdrive when rice was grown in phosphorus-poor conditions;

b) showed that Nipponbare and another strain of rice plants genetically engineered to contain the gene in a highly active form had more than 60% grain yield under phosphorus-poor conditions;

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c) found that the efffect of the gene was to greatly enhance the growth of roots, presumably making them more efficient at absorbing what little phosphorus the soil contained.

The scientists repeated the experiment, this time introducing the gene into the rice strains through crossing them with Kasalath and then breeding them back repeatedly to conventional rice strains so that only small chunks of Kasalath -- including PSTOL1 -- remained. They found they got similarly vigorous root growth.

“In light of the need to increase rice production for a growing population despite potentially negative impacts of climate change and increasing scarcity of natural resources, it will be critically important to systematically explore traditional rice varieties in which high-value genes such as PSTOL1 are preserved, and to enable breeders to efficiently use these genes in breeding programs,” the authors write.

About half the world’s agricultural lands are poor in phosphorus, notes Leon V. Kochian of the USDA and Cornell University in an accompanying commentary. Many of these regions are in developing countries, he says -- and rock phosphate could run out in 50 to 100 years. There’s lots of work still to do, but perhaps this same gene could improve uptake of other minerals from soil, he added.

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[For the record, 1.37 p.m. Aug 24: An earlier version of this post misspelled the last name of study author Rico Gamuyao.]

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