Submitted to: Temperate Rice Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 30, 2003
Publication Date: March 10, 2003
Citation: Rutger, J.N., Bryant, R.J., Yan, W. 2003. INDICA BASE-BROADENING FOR TEMPERATE RICE. Temperate Rice Conference Proceedings. March 10-13, 2003 Punta Del Este, Uruguay. Paper#141. Interpretive Summary: Proceedings - Interpretive summary not required.
Technical Abstract: For over 15 years high-yielding indicas have been available, but grain quality, especially amylose content, has not been suitable for U.S. markets. Traditional approaches of hybridizing tropical japonicas with indicas have been challenged by difficulty in recovering recombinants possessing both high yield and suitable grain quality. Therefore a base-broadening program, working only within indicas, was initiated to develop high yielding indicas with intermediate amylose content (21-22%). Two approaches, hybridization and induced mutation, are being used. In the hybridization approach, the very early, high yielding, high amylose (25%), indica cultivar Zhe733, was crossed with late maturing, intermediate amylose accessions from IRRI. The IRRI materials are close to U.S. long grain quality standards, but generally are too late in the U.S. Stepwise selection for early maturity and intermediate amylose level was done for several generations. In F7 yield tests in 2001, 59 early maturing lines which had intermediate amylose content yielded from 6550 to 9450 kg/ha, compared to 5020 and 5800 for two tropical japonica checks and 6690 for the Zhe733 parent. Severe lodging in 2002 precluded use of yield data in that season. In the induced mutation approach, IRRI accessions were irradiated. Over 50 selections were identified which were 10 to 14 days earlier than their respective parents. Mutagenesis studies for early maturing also have been initiated in additional high-yielding indicas which have amylose content similar to U.S. cultivars. Indica germplasm adapted to temperate regions is being produced in the combined hybridization and mutagenesis programs.