compared with indica inbreds and NPTs. Laza et al. (2003)
studied hybrids, indica inbreds, and NPTs and found that
harvest index had a much closer relationship with grain yield
than with biomass production. Peng et al. (1999), however,
attributed the 9% advantage in yield potential of hybrids to
greater biomass production rather than harvest index. Song
et al. (1990) and Yamauchi (1994) also reported that hybrids
had a higher yield than indica inbreds mainly due to an
increase in total biomass production. The contribution of
biomass production and harvest index to genetic gains in
grain yield varied among different studies, probably due to
different genotypes used and different growing conditions
in these studies (Laza et al., 2003).