Abstract
Great progress has been made in japonica rice breeding.However,little is known about physiological and agronomical features responsible for the improvement.In this study,12 typical japonica rice cultivars (including super rice) applied in the production in Jiangsu province during the last 60 years were used,and classified into six types of 1950s,1960s,1970s,1980s,and 1990s in the 20th century and since 2000 according to their application times.All the tested cultivars were grown in the field and the evolution characteristics of grain yield and its components,source-sink relationships,morphology and physiology were investigated.Results showed that the grain yield was progressively increased with the evolution of the cultivars.Increase in grain yield was attributed mainly to the increase in total number of spikelets,which resulted mainly from large panicles.The percentage of filled grains was increased for cultivars from 1950s to 1980s in 20th century,whereas it was decreased for those at 1990s in 20th century and since 2000.There was no significant difference in 1000-grain weight among the six types of cultivars.With the improvement of rice cultivars,biomass,especially after heading,and harvest index were simultaneously increased.At main growth stages,with the improvement of rice cultivars,root dry weight,root-shoot ratio,root oxidation activity and leaf photosynthetic rate were increased significantly,but root oxidation activity and leaf photosynthetic rate during grain filling for super rice were declined rapidly.Improvement of rice cultivars significantly increased total,effective,high-effective leaf areas and grain-leaf ratio (the ratio of total spikelet number to leaf area) at heading,and increased panicle length,number of primary and secondary panicle branches greatly.From 1950s to 1990s in the 20th century,plant height was reduced,while it was increased significantly for super rice since 2000,with a plant height of about 120 cm.The leaf angle of the top three leaves on stems were significantly decreased with the improvement of rice cultivars.The results indicate that agronomical and physiological characteristics of japonica cultivars are improved during the evolution,and low percentage of filled grains limits grain yield potential in super rice cultivars.
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Claims 20
Claim · model-written summary
Grain yield progressively increased across cultivar eras.
- Taxon
- japonica rice
_by_Augustus_Binu.jpg?width=60)
Oryza sativa Japonica Groupt0 - Outcome
- grain yielde0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_by_Augustus_Binu.jpg?width=500)
Verbatim
e0“grain yield was progressively increased with the evolution of the cultivars”
t0“Japonica Rice”
Claim · model-written summary
Total spikelet number increased with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- total number of spikeletse0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Increase in grain yield was attributed mainly to the increase in total number of spikelets”
t0“Japonica Rice”
Claim · model-written summary
Panicles became larger across cultivar eras.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- large paniclese0
- Direction
- largee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which resulted mainly from large panicles”
t0“Japonica Rice”
Claim · model-written summary
Filled-grain percentage increased from the 1950s to the 1980s.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- percentage of filled grainse0
- Direction
- increasede0
- Qualifier
- from 1950s to 1980se0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“percentage of filled grains was increased for cultivars from 1950s to 1980s in 20th century”
t0“Japonica Rice”
Claim · model-written summary
Filled-grain percentage decreased in 1990s and post-2000 cultivars.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- percentage of filled grainse0
- Direction
- decreasede0
- Qualifier
- 1990s in 20th century and since 2000e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The percentage of filled grains was increased for cultivars from 1950s to 1980s in 20th century,whereas it was decreased for those at 1990s in 20th century and since 2000”
t0“Japonica Rice”
Claim · model-written summary
Thousand-grain weight did not differ significantly among cultivar eras.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- 1000-grain weighte0
- Direction
- no significant differencee0
- Comparator
- six types of cultivarse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no significant difference in 1000-grain weight among the six types of cultivars”
t0“Japonica Rice”
Claim · model-written summary
Biomass increased with cultivar improvement, particularly after heading.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- biomasse0
- Direction
- increasede0
- Qualifier
- especially after headinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“biomass,especially after heading,and harvest index were simultaneously increased”
t0“Japonica Rice”
Claim · model-written summary
Harvest index increased with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- harvest indexe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“biomass,especially after heading,and harvest index were simultaneously increased”
t0“Japonica Rice”
Claim · model-written summary
Root dry weight and root-shoot ratio increased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- root dry weight,root-shoot ratioe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root dry weight,root-shoot ratio,root oxidation activity and leaf photosynthetic rate were increased significantly”
t0“Japonica Rice”
Claim · model-written summary
Root oxidation activity increased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- root oxidation activitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root dry weight,root-shoot ratio,root oxidation activity and leaf photosynthetic rate were increased significantly”
t0“Japonica Rice”
Claim · model-written summary
Leaf photosynthetic rate increased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- leaf photosynthetic ratee0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root dry weight,root-shoot ratio,root oxidation activity and leaf photosynthetic rate were increased significantly”
t0“Japonica Rice”
Claim · model-written summary
Root oxidation activity and leaf photosynthetic rate declined rapidly during grain filling in super rice.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- root oxidation activity and leaf photosynthetic ratee0
- Direction
- declinede0
- Qualifier
- during grain filling for super ricee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root oxidation activity and leaf photosynthetic rate during grain filling for super rice were declined rapidly”
t0“Japonica Rice”
Claim · model-written summary
Total, effective and high-effective leaf areas increased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- total,effective,high-effective leaf arease0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significantly increased total,effective,high-effective leaf areas and grain-leaf ratio”
t0“Japonica Rice”
Claim · model-written summary
Grain-leaf ratio increased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- grain-leaf ratioe0
- Direction
- increasede0
- Qualifier
- at headinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significantly increased total,effective,high-effective leaf areas and grain-leaf ratio (the ratio of total spikelet number to leaf area) at heading”
t0“Japonica Rice”
Claim · model-written summary
Panicle length increased with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- panicle lengthe0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased panicle length,number of primary and secondary panicle branches greatly”
t0“Japonica Rice”
Claim · model-written summary
The number of primary and secondary panicle branches increased with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- number of primary and secondary panicle branchese0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased panicle length,number of primary and secondary panicle branches greatly”
t0“Japonica Rice”
Claim · model-written summary
Plant height declined between the 1950s and 1990s.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- plant heighte0
- Direction
- reducede0
- Qualifier
- From 1950s to 1990s in the 20th centurye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From 1950s to 1990s in the 20th century,plant height was reduced”
t0“Japonica Rice”
Claim · model-written summary
Super rice after 2000 was significantly taller, around 120 cm.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- plant heighte0
- Direction
- increasede0
- Value
- about 120 cme0
- Qualifier
- super rice since 2000e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was increased significantly for super rice since 2000,with a plant height of about 120 cm”
t0“Japonica Rice”
Claim · model-written summary
Angles of the top three leaves decreased significantly with cultivar improvement.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- leaf angle of the top three leaves on stemse0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf angle of the top three leaves on stems were significantly decreased with the improvement of rice cultivars”
t0“Japonica Rice”
Claim · model-written summary
Low filled-grain percentage limits yield potential in super rice, according to the authors.
- Taxon
- japonica riceOryza sativa Japonica Groupt0
- Outcome
- grain yield potentiale0
- Direction
- limitse0
- Qualifier
- low percentage of filled grainse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“low percentage of filled grains limits grain yield potential in super rice cultivars”
t0“Japonica Rice”