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An early-morning flowering trait enhances heat-resilience at flowering
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  • Tsutomu Ishimaru,
  • Hlaing Thandar,
  • Ye Oo,
  • Tin Lwin,
  • Kazuhiro Sasaki,
  • Patrick Lumanglas,
  • Eliza-Vie Simon,
  • Tin Myint,
  • Aris Hairmansis,
  • Untung Susanto,
  • Bharathi Ayyenar,
  • Raveendran Muthurajan,
  • Hideyuki Hirabayashi,
  • Yoshimichi Fukuta,
  • Kazuhiro Kobayashi,
  • tsutomu matsui,
  • Mayumi Yoshimoto,
  • Than Htun
Tsutomu Ishimaru
NARO
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Hlaing Thandar
Yezin Agricultural University
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Ye Oo
Yezin Agricultural University
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Tin Lwin
Yezin Agricultural University
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Kazuhiro Sasaki
Japan International Research Center for Agricultural Sciences
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Patrick Lumanglas
International Rice Research Institute
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Eliza-Vie Simon
International Rice Research Institute
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Tin Myint
Department of Agricultural Research
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Aris Hairmansis
Indonesian Center for Rice Research
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Untung Susanto
Indonesian Center for Rice Research
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Bharathi Ayyenar
Tamil Nadu Agricultural University
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Raveendran Muthurajan
Tamil Nadu Agricultural University
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Hideyuki Hirabayashi
NARO Institute of Crop Science
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Yoshimichi Fukuta
Japan International Research Center for Agricultural Sciences
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Kazuhiro Kobayashi
Shimane University
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tsutomu matsui
Gifu University
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Mayumi Yoshimoto
National Institute for Agro-Environmental Sciences
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Than Htun
Yezin Agricultural University
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Abstract

An early-morning flowering (EMF) trait is supposed to be effective in enhancing grain yield due to mitigation of heat-induced spikelet sterility at flowering in rice. This study evaluated (i) phenotypic differences between a near-isogenic line carrying a QTL for EMF trait, designated as IR64+qEMF3, and a recurrent parent, IR64, under wide variation in climates and (ii) whether an EMF trait can enhance grain yield under heat stress at flowering. IR64+qEMF3 had significant earlier flower opening time (FOT) in diverse environmental conditions including temperate, subtropical, and tropical regions. Under normal temperatures at flowering, IR64+qEMF3 had similar grain yield to IR64 with some significant changes in agronomic traits and yield components. Field trials in heat-vulnerable regions of central Myanmar for seven crop seasons showed that higher percentage of filled grains contributed to the significantly higher grain yield in IR64+qEMF3 among yield components when plants were exposed to daily maximum air temperatures around 36.5 oC or higher. Lower spikelet sterility in IR64+qEMF3 was attributed to the earlier FOT during cooler early morning hours. This is the first field study that clearly demonstrates the enhancement of heat-resilience due to EMF trait at flowering.