2. Materials and methods
2.1. Plant material
Three elite lines were used as the recurrent parents: two
broadly adapted, high-yielding lowland indica cultivars
(IR64 and Teqing), and the tropical japonica new plant type
breeding line IR68552-55-3-2 (NPT; Khush, 1995). A total
of 163 varieties of diverse origins were used as donors,
including 72 modern varieties, 74 landraces, and 17 breeding
lines from 25 countries. These donors, according to an assay
based on 101 simple sequence repeat (SSR) markers (Yu
et al., 2003), included 53 japonicas, 109 indicas, and 1 deepwater
rice, Jalmagna, from India. A total of 322 crosses were
made between the recurrent parents and donors. These were
advanced to BC2F2 generation. This resulted in 124 IR64