Plant Materials and Field Experiments
The field trial of wild-type rice (Oryza sativa L. cv Taichung 65) and the
d61-7 mutant derived from Taichung 65 was performed at the experimental
farm of Nagoya University (Togo town, Aichi, Japan; latitude 35?06# north;
longitude 137?05# east). Thirty-eight-day-old seedlings were transplanted into
a paddy field at one plant per hill with a spacing of 30 3 15 cm (22.2 plants
m 22 ), 15 3 15 cm (44.4 plants m 22 ), or 15 3 10 cm (66.7 plants m 22 ). Each
treatment had two replications in randomized blocks, and each plot size was
2.1 3 2.5 m. Each plot was divided into two parts, one for measurement of the
aerial biomass, the other for yield assessment. Field management followed
normal agricultural practices. A total of 80 kg ha 21 of nitrogenous fertilizer
was applied in three splits (40 kg ha 21 before transplanting, 20 kg ha 21 at
3 weeks before heading, and 20 kg ha 21 at 2 weeks after heading). To monitor
dry weight accumulation, we destructively sampled five representative plants
from each plot. Plant samples were air dried for 2 months. The aerial parts
were separated from the roots and divided into vegetative organs (culm, leaf
sheath, and leaf blade) and reproductive organs (panicle) to determine the dry
weight. For statistical analyses, plants showing maximal and minimal dry
weight of total aerial parts in each plot were excluded. To measure the yield
components, 10 representative individuals, excluding marginal plants, were
harvested from each plot. Grain number and fertility of all panicles were
measured. Grain weight was estimated from the grain number in 5 g of grain.
Statistical analysis was performed with a commercially available statistical
package, JMP version 5.1 (SAS Institute Japan).