IRRI identifies the first case of rice yellowing syndrome in the Philippines

STA. CRUZ, LAGUNA (21 May 2025) – Scientists from the International Rice Research Institute (IRRI) have confirmed the first documented case of yellowing syndrome in the Philippines caused by two different viruses.

The IRRI team, led by Dr. Van Schepler-Luu, investigated reports from the Department of Agriculture- Regional Crop Protection Center (RCPC) and the Stanta Cruz Municipal Agriculture Office of unusual yellowing and stunting in the LAV666 rice variety, locally known as Jackpot 102. Initially, they suspected that the rice plants were infected with tungro or orange leaf disease as the leaves of the infected rice plants turned yellow-orange, one of the key symptoms of tungro.

However, the team confirmed, through RT-PCR and ELISA tests, a co-infection of Rice Grassy Stunt Virus (RGSV) and Rice Ragged Stunt Virus (RRSV) also known as “yellowing syndrome.”

RGSV and RRSV are both common in rice, particularly in South and Southeast Asia. For one, RGSV typically causes pale yellow, narrow leaves, excessive tillering, and stunted growth. In contrast, RRSV causes darker green leaves with serrated, twisted, or curled edges, along with stunted growth. RGSV-infected plants fail to produce panicles, while RRSV shows partial panicle exertion and unfilled grains. However, both viruses could affect panicle exertion in severe cases.

In the area of Sta. Cruz where yellow syndrome has been confirmed, the impact is severe, with very low or nearly no harvest obtained. According to the farm caretaker, the infected field affected by yellowing syndrome yielded only 16 cavans, compared to the expected yield of 200 cavans.

Yellowing syndrome first appeared in rice fields in the Mekong Delta, Vietnam, in 1989. Rice plants affected by the disease exhibited a spreading growth pattern, stunted growth, and yellowing leaves. By…