Geneticists build new rice for poor soils

Scientists in a research Institute in India have identified a unique gene that enables rice plants to produce around 20 per cent more yield by increasing the uptake of phosphorus, a very important, but limited, plant nutrient, in a breakthrough that could equally aide Kenya'sm than 200,000 rice farmers currently grappling with both pests and soaring fertiliser prices.

The discovery unlocks the potential to grow rice on the lowest value phosphorus-deficient land prevalent across Africa.

The gene, called PSTOL1, which is an abbreviation for Phosphorus Starvation Tolerance, helps rice grow a larger, better root system and thereby access more phosphorus. In problem soils phosphorus is often locked into the soil and unavailable to plants. Farmers can apply phosphorus fertilizers to increase productivity but these are often unaffordable to poor farmers. Moreover, phosphorus is a non-renewable natural resource with fertiliser suppliers now arguing that rock phosphate reserves - the source of most phosphorus fertilizers - are running out, which has been blamed for the sharp rise in fertilizer prices.

In Kenya, fertilizer prices have risen by 120 per cent in the last two years creating shortages that have had a huge effect on rice yield, with the Ministry of Agriculture estimating the yield to have declined from 42 bags per hectare in 2009 to 29 bags in 2011.

This has seen the gap between rice production and consumption widen too, with consumption now standing at about 300,000 tonnes against an annual domestic production of between 45,000 to 80,000 tonnes. The gap is met through rice imports, worth Sh9bn in 2011.

The key to reversing this deterioriation may now have been found, with the new phosphorous efficeient rices.

"For many years we have searched for genes that improve phosphorus uptake," said Dr. Sigrid Heuer, senior scientist at the International Rice Research Institute (IRRI) and leader of the team that published the discovery.

"We've known for a long time that the traditional rice variety Kasalath from India has a set of genes that helps rice grow well in soils low in phosphorus," she said.

Kasalath was initially studied by Dr. Matthias Wissuwa from the Japan International Research Center for Agricultural Sciences, who then collaborated with IRRI and shared the DNA information of the novel rice variety. The current research into phosphorus uptake has been supported and facilitated by the CGIAR Generation Challenge Program.

"We have now hit the jackpot and found PSTOL1, the major gene responsible for improved phosphorus uptake and understand how it works," said Heuer.

According to Dr. Wricha Tyagi at the School of Crop Improvement at the Central Agricultural University in India, knowledge of the exact gene will be critical for future breeding programs, especially in Sub Saharan Africa where rice productivity is less than 40 per cent of the international average due to acidic soil and the poor availability of phosphorus.

The discovery of the PSTOL1 gene means that rice breeders will be able to breed new rice varieties faster and more easily, and with 100% certainty their new rice will have the gene.

The discovery also demonstrates the importance of conserving the genetic diversity of traditional crop varieties such as Kasalath. IRRI conserves more than 114,000 different types of rice in the International Rice Genebank.

The group of rice (the aus-type) that Kasalath is part of is also the source of the submergence tolerance gene, which IRRI has used to breed submergence-tolerant (Sub1) rice varieties that are being widely adopted across Asia and have been introduced in various SubSaharan countries including Kenya.

According to the researchers, new rice varieties with an enhanced capacity to take up phosphorus may also now be available within a few years to farmers in SubSaharan Africa.

Written by Bob Koigi for African Laughter