By pedigree analysis, 99 varieties released before 1988
were bred by using germplam introduced largely from
Japan, and 10 major parental varieties, except one Taiwan
landrace Oloan-chu, were from Japan (Lin, 1991a). Improving grain quality has been a high priority; therefore,
elite Japanese cultivars with good grain appearance and
eating quality have been used in modern rice-breeding
programs. Because 85% of Taiwan varieties descended
from Japanese varieties, the genetic diversity of modern
cultivars was expected to be very narrow (Wu and Lin,
2008). Nevertheless, germplasm introduced from IRRI the
Philippines and other countries has been incorporated into
rice breeding programs to increase the gene pool of cultivars and to breed new varieties with resistance to biotic
and abiotic stresses later on.