In a recent Nature paper and a related media release, the source of an important gene (PSTOL1) that helps rice take up phosphorous was reported as a rice variety from India called Kasalath. The discovery of the PSTOL1 gene is very exciting news as it has such potential to improve the food security of rice farmers with the lowest value phosphorus-deficient land.
In August, the International Rice Research Institute (IRRI) held a training workshop for plant breeders across Asia to help them use molecular marker technology to breed the PSTOL1 gene into their rice varieties. This will mean that farmers will get access to new locally-adapted rice varieties with the PSTOL1 gene and the trait that helps the plants take up phosphorus that can boost yields by 20%.
Putting this important discovery and work aside, there’s an interesting side story here that relates to both understanding genetic diversity of rice and conserving it.
IRRI manages the International Rice Genebank where more than 115,000 types of rice are conserved. Conserving this rice genetic diversity is one of our most important roles. Even within one singular variety of rice, such as Kasalath, plants that grow in different regions will be genetically different from each other. For scientists studying and identifying genes in rice, it is important to know the exact heritage of the specific plant sample that they are investigating – because what they find for one individual plant sample may be different to another even if they are from the same variety of rice. The PSTOL1 gene was discovered in a specific plant sample (also known as an accession) of the rice variety Kasalath that was from India.
“The samples of Kasalath used for the published research trace back to a sample collected from Karimganj, Assam in 1925, in what is present-day India,” said Dr. Ruaraidh Sackville Hamilton in his response to questions about the source of the material. “It is not clear if the sample used by the Japanese traces back to exactly the same collected sample, but I’m informed it is also from a very old collection in Assam. So, based on the CBD’s [Convention on Biological Diversity] definition of country of origin, India is the country of origin of the material studied.”
However, according to Dr. Abed Chaudhury, a plant scientist from the Sylhet area of Bangladesh, the geographical range of the entire variety of Kasalath includes the Sylhet region, which encompasses Bangladesh’s Sylhet Division and neighboring parts of northeast India.
“Sylhet farmers knew it [Kasalath] hundreds of years ago calling is Kasa Lota or “young green shoot” rice,” said Dr. Chaudhury in his comment on a blog post.
Kasalath has been widely grown throughout Sylhet as a prized traditional variety since time immemorial. It has been recorded in Maulvi Bazar, Kamalganj, Rajnagar, Bishwanath, Chhatak, Gopalganj, Kulaura, and Karimganj. Now, Karimganj is in India, but most of the rest of the Sylhet region is in Bangladesh.
Kasalath is also part of a broader group of rice called the Aus variety group. This group of rice is famously known to tolerate difficult growing conditions and was also the source of another important gene (Sub1) that IRRI has used to develop submergence tolerant rice varieties. Other members of the Aus group of rice are known to carry genes for tolerance to drought, heat, salinity, and other stresses.
A figure used in the Nature paper illustrates that the Aus variety group was developed in India. It is an accurate depiction of the specific results for India however, the absence of evidence on the involvement of Bangladesh should not be misinterpreted as a denial of the role of Bangladesh in the development of Aus.
“Language plays an important role in determining origin,” said Dr. Chaudhury. “The Aus rice is actually pronounced Aoosh, which is derived from [the Bangla word] Ashoo meaning “early”; so earliness is the main character of these lines and lines of diverse provenance were selected on the basis of earliness.”
So while the Nature paper outlines specific evidence for domestication of Aus rice in India, it would be misleading to generalize this to conclude that Aus was not also domesticated in Bangladesh.
“What is clear is that Aus varieties, and Kasalath, have been grown in India as well as Bangladesh for many years,” concluded Dr Ruaraidh Sackville Hamilton.
Understanding the heritage of plant samples used in research and conserving the complex diversity of rice varieties is critical to rice research. Without it we would not have access to the immense genetic diversity of rice to develop new rice varieties that can help farmers face challenges like problem soils or harsh weather extremes. And of course there is intrinsic value in conserving the genetic diversity of rice too – which is done at the International Rice Genebank.
Thanks to everyone who provided information to help fully explain this: Dr. Abed Chaudhury (Food Security Development Center, Mauritius), Dr. Tanvir Hossain (formerly of BRRI),Prof. Zeba Seraj (University of Dhaka), Md. Sazzadur Rahman (University of Dhaka and BRRI), Dr. Sigrid Heuer (IRRI), Dr. Ruaraidh Sackville Hamilton (IRRI), Dr. Matthias Wissuwa (JIRCAS), Prof. Susan McCouch (Cornell University), Dr. Pat Gonzales (IRRI), Dr. Ken McNally (IRRI) and all the bloggers over at the Agricultural Biodiversity Weblog.