The first-generation NPT lines based on tropi-cal japonicas were developed in 1993.
As intended, the NPT lines had large panicles, few unproductive tillers, and lodging resistance. They did not yield well, however, because of limited biomass production and poor grain filling (Peng and Khush, 2003).
It was speculated that the excessive reduction in tillering capacity resulted in low biomass production of the first-generation NPT lines.
The first-generation NPT lines were susceptible to diseases and insects, and had poor grain quality, thus the lines could not be released as cultivars but were valuable genetic materials for rice breeding programs.