Genetic Elucidation for Response of Flowering Time to Ambient Temperatures in Asian Rice Cultivars.

Kiyosumi Hori,Yasunori Nonoue,Keiichi Mochida,Shuichi Fukuoka,Yukiko Uehara-Yamaguchi,Jun-Ichi Yonemaru,Kazufumi Nagata,Koka Shu,Daisuke Saisho,Asaka Kanatani,Takashi Hirayama

doi:10.3390/ijms22031024

Abstract

Climate resilience of crops is critical for global food security. Understanding the genetic basis of plant responses to ambient environmental changes is key to developing resilient crops. To detect genetic factors that set flowering time according to seasonal temperature conditions, we evaluated differences of flowering time over years by using chromosome segment substitution lines (CSSLs) derived from japonica rice cultivars “Koshihikari” × “Khao Nam Jen”, each with different robustness of flowering time to environmental fluctuations. The difference of flowering times in 9 years’ field tests was large in “Khao Nam Jen” (36.7 days) but small in “Koshihikari” (9.9 days). Part of this difference was explained by two QTLs. A CSSL with a “Khao Nam Jen” segment on chromosome 11 showed 28.0 days’ difference; this QTL would encode a novel flowering-time gene. Another CSSL with a segment from “Khao Nam Jen” in the region around Hd16 on chromosome 3 showed 23.4 days” difference. A near-isogenic line (NIL) for Hd16 showed 21.6 days’ difference, suggesting Hd16 as a candidate for this QTL. RNA-seq analysis showed differential expression of several flowering-time genes between early and late flowering seasons. Low-temperature treatment at panicle initiation stage significantly delayed flowering in the CSSL and NIL compared with “Koshihikari”. Our results unravel the molecular control of flowering time under ambient temperature fluctuations.

Highlights

Introduction iationsGlobal warming is likely to reach 1.5 ◦ C between 2030 and 2052 if it continues at the current rate [1]
We found wide variations in flowering time of 18 Asian rice cultivars during 2011 to 2019 (Figure 1A, Supplementary Table S1)
To identify genetic factors related to the flowering time fluctuation, we evaluated flowering time in a set of chromosome segment substitution lines (CSSLs) derived from crosses between “Koshihikari” and “Khao flowering time in a set of CSSLs derived from crosses between “Koshihikari” and “Khao

Summary

Introduction

Introduction iationsGlobal warming is likely to reach 1.5 ◦ C between 2030 and 2052 if it continues at the current rate [1]. Cultivated rice (Oryza sativa L.) originated from a wild rice species (Oryza rufipogon Griff.), which grows mainly in the tropics [2,3]. Rice is inherently adaptable to hot environments. Novel rice cultivars with resistance to very hot environments are required for regions where extreme warming is expected [1]. Climate change is causing large fluctuations in temperature, solar irradiation, precipitation and soil moisture, especially in the tropics [4]. At the high-latitude limits of rice cultivation; low temperatures at the seedling, panicle initiation and maturation stages severely decrease grain yield [5,6]. There is an increasing demand for new cultivars that are adaptable to both effects of climate change. To develop climate-change resilient crops, it is necessary to elucidate the genetic basis of plant response to ambient environmental changes

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Conclusion