Growth performance of the photoperiod-sensitive rice varieties released for the rainfed lowland in different soil types in Cambodia

概要

報告番号

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第

主

号

論

文

の

要

旨

Growth performance of the photoperiod-sensitive rice

論文題目

varieties released for the rainfed lowland in different soil
types in Cambodia
（カンボジアの土壌タイプが異なる条件における天水田向け
感光性イネ品種の生育および生産特性）

氏

名

UCH Chanthol

論 文 内 容 の 要 旨
The present study aimed to analyze the grain yield and stability among ten
popular varieties that were released for rainfed lowland ecosystems across the four
different soil types in Cambodia. For the study 1, two experimental fields in
Battambang province produced the highest grain yield, followed by the fields in
Pursat, Kampong Thom, and Siem Reap, respectively. The soil analysis showed that
soil from Battambang is relatively high in clay content. Moreover, the relationship
analysis showed that higher clay content is positively correlated with some soil
fertility parameters. Taken together, the results suggested that higher grain yield
achieved in Battambang was associated with good soil fertility. Based on the
analysis, Phka Rumduol was stable, and produced the highest grain yield across the
eight tests, followed by Phka Rumdeng, Phka Mealdei and CAR4, respectively.
While, Riang Chey was lowest yielder. The Pearson’s correlation analysis between
some important yield-related traits with grain yield revealed that percentage of
filled grain and number of panicles per hill are highly positive with grain yield.
These results were from the field experiment for only one year and the important
yield component determining the difference in grain yield was different depending
on soil environment in the year of 2019. Thus, as the following experiment, we
exam similar setting field experiment again to deepen our understanding of limiting

factors of varietal difference in yield components employing specific varieties and
more detail growth analytical procedures including nutrient analysis as the next
study theme.
In study 2, an experimental field in Battambang province produced the
highest grain yield, followed by the fields in Pursat, Kampong Thom, and Siem
Reap, respectively. From the field experiments in two cultivation seasons, Phka
Rumduol was stable, and produced the highest grain yield across the four tests,
followed by Phka Mealdei and CAR4, respectively. While, Riang Chey was lowest
yielder. The variety Phka Rumduol showed these preferable traits and produced
higher yields in fertile to poor natural soil fertility conditions with moderate
variation. This variety is considered to be more desirable and ideal due to its
stability and higher grain yield. The other varieties, namely, Phka Mealdei, Phka
Rumdeng, and CAR4, were identified as above-average yielders. Therefore, those
varieties potentially may be recommended for cultivation in rainfed lowland rice
ecosystems in Cambodia due to their high yields. CAR4 showed moderate variation
at the same level as Phka Rumduol. From the point of stability, Phka Rumduol and
CAR4 can be expected to excel.
In the pot experiment, the significance of soil groups and varieties, and its
interaction are the same as the field study 2. The tendency in panicle number per
hill, percentage of filled grains and 1000-grain weight positively correlate with
grain yield. T/R ratio showed negative relationship with leaf N concentration. In
conclusion, larger roots proportion to top part (shoot) will lead to higher leaf N
concentration especially poor soil condition such as SRP.
To sum up, from the three studies higher yielding varieties performed
preferable growth and production in any kind of soil condition. The varietal
difference in grain yield might attribute to the difference in panicle number per hill
or % of filled grains, and the main limiting factor will differently be depending on
soil condition. In addition, higher yielding varieties’ performance could be
attributed by preferable morphological traits such as wider leaf blade and/or larger
root proportion with their following positive influence for better panicle number
per hill, % of productive culms and % of filled grains based on higher nutrient
uptake ability.