By Tsutomu Ishimaru
Senior Scientist-Plant Breeder
IRRI-Japan Collaborative Research Project
Plant Breeding, Genetics, and Biotechnology (PBGB)
6 August 2015
The recent trend in temperature increase is predicted to have negative effects on crop productivity. Climate is expected to become more variable with frequent episodes of stressful temperatures coinciding with critical crop developmental stages such as flowering. Rice (Oryza sativa L.) is very susceptible to heat stress at the flowering stage, thus, heat-induced spikelet sterility (HISS) at flowering would be one of the serious threats to rice production in the near future.
The early-morning flowering (EMF) trait is effective against heat stress at flowering as it shifts flower opening time (FOT) to the early morning when it’s cooler. There is a very small variation in FOT among current varieties, whereas there is a wide variation among wild rice species. By using the wide variation in FOT among wild rice, an attempt was made to exploit the EMF locus from wild rice, Oryza officinalis (CC genome). Genetic studies and breeding efforts have been connected with the development of near-isogenic lines (NILs) carrying a QTL for EMF. Furthermore, the EMF study is currently being extended to the combined stress of heat and drought. The hotspots for HISS at flowering were identified through a field survey in the potential vulnerable regions of Laos and southern India. The comprehensive challenges, genetics, breeding, agronomy, and physiology in EMF to mitigate HISS at flowering will be presented.