A PhilRice-led study titled Quantitative Trait Loci (QTL) for high-temperature tolerance in rice (Oryza sativa L.) won the Outstanding Scientific Paper Award during the 39th National Academy of Science and Technology (NAST Phils) Annual Scientific Meeting held at Manila Hotel, July 12-13.

Researchers of the study Dr. Norvie L. Manigbas and Jupiter L. Grospe from PhilRice, and Evaristo A. Abella of the Central Luzon State University identified nine QTLs containing the genes that can counter the ill-effects of high temperature. QTLs are sections of DNA containing the genes that control the trait.

These QTLs were found through the backcrossing of Dular and NSIC Rc150 (Tubigan 9). Dular is an Indian heat-tolerant rice variety that has low yield potential. Tubigan 9, on the other hand, is a Philippine rice variety with an average yield of 8.5 t/ha but not resistant to high temperature.

Six major QTLs, namely qHTfert1, qHTfert3, qHTfert4, qHTtof10, qHTdht3, and qHThd3, and three minor QTLs namely qHTdht4, qHTdht10, and qHTdht5 were identified.

According to PhilRice breeder Manigbas, these QTLs will be used in mapping genes using molecular markers and incorporating the genes into high-yielding cultivars through marker-assisted breeding. Through this process, breeding new cultivars becomes faster.

“As of now, we do not have any heat-tolerant rice varieties released in the country. Through this study, we’ve learned that the heat-tolerant trait is associated to the plants’ heading days, time of flowering, fertility, and dehiscent temperature – most of which are found in the nine QTLs,” Manigbas explained.

Earlier studies have confirmed that high temperature affects all growth stages of rice. However, it is from the booting to flowering stage that rice is most sensitive to high temperature. Moreover, temperature exceeding 35oC at flowering stage can cause high pollen and grain sterility in rice. This leads to serious yield loss, low grain quality, and low harvest index.

At present, six advanced promising lines are currently being tested for multi-location trials in the National Cooperative Test under high temperature environments.

NAST, under the Department of Science and Technology, is the highest recognition and advisory body in matters related to science and technology in the Philippines.