| dc.description.abstract | This study focused on characterizing and determining the inheritance pattern of
very high tillering and dwarf traits of a rice mutant. To characterize the new mutant,
field phenotyping studies, and response of two mutant lines (M-13662 & M-13684) to
three levels of nitrogen (179, 202, 224 kg ha-1) and five planting densities (1, 2, 3, 4, 5
plants hill-1) in greenhouse conditions were conducted. A separate study was carried out
to determine the response of the two mutant lines to gibberellic acid (GA) application.
The mutants were 50-55 cm tall and produced 89-121 tillers plant-1 at harvest.
Dwarfness of the mutants was due to average shortening of the top four internodes as
well as compression of 2-3 basal internodes. The first tiller emerged at the 4th leaf stage
whereas no tiller was observed in semi-dwarf rice cultivar, Cocodrie. Results showed
that the production of high tiller numbers was the result of the release of axillary buds
from a dormant stage rather than the initiation of additional axillary buds. The mutants
were late maturing than controls (Cocodrie & Zhe733). The panicles were very short
(10-12 cm) and had 25-30 small grains. The majority of tillers of the mutants followed
the dn-type dwarf pattern based on Takeda’s classification, but a few plants had a different dwarfing pattern not included in the classification. Both mutant lines were
found to have similar agronomic traits but were significantly different from controls. The
tillering ability of the mutants was affected by the five different planting densities as
well as the three nitrogen levels. Mutants produced more tillers, both productive and
non-productive, at the lowest plant density. The longest and shortest panicles were
observed at 202 kg ha-1 and 179 kg ha-1, respectively. Variations in other agronomic
traits were found not significant. The response of the mutant to GA application was
similar to Cocodrie, and thus was considered GA responsive. Preliminary DNA data
using SSR markers supported the presumed origin of the mutants and the genetic
analysis indicated that one recessive gene controlled both the dwarfing and very high
tillering traits. | en |
