Development of betacarotene-enriched and disease resistant rice disease

Locally-adapted rice varieties containing high amount of beta-carotene in the grains (Golden Rice) and resistant to tungro and bacterial leaf blight (BLB) are being developed to help combat the persistent problem of vitamin A deficiency (VAD) in the country. One strategy aims to develop Golden Rice Versions of popular varieties PSB Rc82 and Mabango 1 through DNA marker-aided backcrossing. The other strategy aims to develop new varieties with the Golden Rice trait and resistance to tungro and BLB using DNA markers and anther culture. Using the first strategy, 26 cross combinations were made using three Syngenta Golden Rice 1 events as donor of the beta-carotene biosynthetic genes. Morphological evaluation and PCR assay using transgene-specific primers confirmed the hybrid nature of the F1 plants. BC1F1 progenies were produced by crossing the F1 plants to their respective recurrent parents. Variations in grain color intensity, an indicator of beta-carotene content, were observed both in the BC1F1 and F2 grains suggesting gene dosage effect. With Mabango 1, so far 491 out of 1261 BC1F1 seeds produced were grown and evaluated resulting in the identification of 148 plants (30 percent) that possess the Golden Rice genes. Several BC1F1 plants were selected based on similarity to Mabango 1 and again backcrossed to the recurrent parent. A total of 7454 BC2F1 seeds have been produced. For PSB Rc82, 4515 BC1F1 seeds have been produced. These will be planted and evaluated for the selection of plants to be used in the production of BC2F1 seeds. For the second strategy, selected BC1F1 plants resistant to tungro and BLB were crossed to advanced lines with good phenotypic acceptability. Of the 52 BC2F1 plants evaluated so far, 11 exhibited intermediate to strong resistance to the two diseases. BC3F1 seeds are being produced using selected BC2F1 plants. Resistant progenies with good phenotypic acceptability will be subjected to anther culture.