Rice Yellow Mottle Virus (RYMV) is responsible for high crop losses in Africa, particularly among small-scale farmers. A research team from Heinrich Heine University Düsseldorf (HHU) and the French National Research Institute for Sustainable Development (IRD) has now developed rice lines that are resistant to the disease using genome editing.

RYMV is an RNA virus spread by beetles and direct leaf-to-leaf contact. There is no known effective protection against the virus and the only real protection is to develop rice varieties that possess a resistance gene against RYMV. Three resistance genes are currently known, and mutations in just one of the genes, called RYMV1, 2, and 3, are sufficient to achieve resistance. The resistant form rymv2 occurs in poor-yielding African rice (Oryza glaberrima) varieties. Also known as CPR5.1, it encodes an important protein from the pores of the cell nucleus. In Arabidopsis, the loss of the only gene copy of CPR5 results in a broad spectrum of resistance not only to viruses but also to bacteria and fungi. However, this loss severely restricts growth, the plants exhibit spontaneous lesions and produce low yields. So it was important to test whether rymv2 resistance could be transferred to other rice varieties without negative consequences.

Using the CRISPR-Cas genome editing method, the research group has now shown that mutations of the RYMV2 gene can be produced in an Asian rice variety that makes it resistant to the virus in a similar way to the African form. The team found that neither switching off the closely related CPR5.2 gene nor the two genes RYMV2 and CPR5.2 under greenhouse conditions leads to impairments. It is also noteworthy that the loss of CPR5.2 does not lead to RYMV resistance. Everything indicates that editing the RYMV2 gene is a promising approach to combating the rice disease in Africa.

For more details, read the news article on the HHU website.

See https://www.isaaa.org/kc/cropbiotechupdate/ged/article/default.asp?ID=20597