Scientists have pinpointed a gene that enables rice plants to produce around
20% more grain by increasing uptake of phosphorus, an important, but limited,
plant nutrient.
The discovery unlocks the potential to improve the food security of rice
farmers with the lowest value phosphorus-deficient land allowing them to grow
more rice to add to global production, and earn more.
The gene -- called PSTOL1 which stands for Phosphorus Starvation Tolerance
-- helps rice grow a larger, better root system and thereby access more
phosphorus. Farmers can apply phosphorus fertilizers to increase productivity
but on problem soils phosphorus is often locked in the soil and unavailable to
plants.
Also, phosphorus fertilizer is often unaffordable to poor farmers. Adding to
the problem is that phosphorus is a non-renewable natural resource and rock
phosphate reserves -- the source of most phosphorus fertilizers -- are running
out.
"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
in Nature.
"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 added.
Kasalath's superior performance under phosphorus deficiency was initially
discovered by Dr. Matthias Wissuwa from the Japan International Research Center
for Agricultural Sciences. He then started collaborating with IRRI and shared
the DNA information of Kasalath. The current research was 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,"
Heuer said.
According to Dr. Wricha Tyagi at the School of Crop Improvement at the
Central Agricultural University in the Indian state of Meghalaya, knowledge of
the exact gene will be critical for future breeding programs suited to Eastern
and North-Eastern -- parts of India where rice productivity is less than 40% of
the national average due to acidic soil and 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.
Dr. Joko Prasetiyono, of the Institute for Agricultural Biotechnology and
Genetic Resources Research and Development in Indonesia, is breeding rice
plants with the PSTOL1 gene. The plants are not genetically modified just bred
using smart modern breeding techniques.
"In field tests in Indonesia and the Philippines, rice with the PSTOL1
gene produced about 20% more grain than rice without the gene," said
Heuer.
"In our pot experiments," she added, "when we use soil that
is really low in phosphorus, we see yield increases of 60% and more, suggesting
it will be very effective in soils low in phosphorus such as in upland rice
fields that are not irrigated and where farmers are often very poor."
The PSTOL1 gene is also being tested in rice varieties for the more
productive irrigated rice-growing areas and initial results show that the
plants grow a better root system and have higher production too. This means it
could help farmers in these areas reduce their fertilizer use and expenditure
without compromising productivity.
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.
New rice varieties with the enhanced capacity to take up phosphorus may be
available within a few years to farmers.
Source: Science Daily
