Effects of Increasing Temperatures on Spikelet Fertility in Different Rice Cultivars based on Temperature Gradient Chamber Experiments

Abstract

Spikelet sterility in rice (Oryza sativa L.) induced by high temperatures is a major concern given global warming predictions. We studied differences among eight rice cultivars in spikelet fertility at five different temperature levels in temperature gradient chamber (TGC) experiments. Six japonica and two indica cultivars were exposed to high-temperature gradients in TGCs during the 2005 flowering season. Spikelet sterility increased with temperature in TGCs and differed among cultivars because of both variations in temperature tolerance and timing of heading. The correlation between spikelet fertility of individual panicles and both air temperature and panicle temperature during flowering was analyzed to compare tolerances among cultivars. The temperature (T 75 ) at which spikelet fertility was 75 % of maximum ranged from 34 to 39°C air temperature and differed significantly among cultivars. Indica varieties had higher T 75 values than japonica varieties. The T 75 values based on panicle temperature also differed among cultivars, but the difference between indica and japonica varieties were less significant. We concluded that the higher temperature tolerances of indica cultivars in our experiments could be attributed to lower spikelet temperatures, and cultivars with similar spikelet temperatures still had different heat tolerances due to differences in pollination ability.

Temperature Difference between Meteorological Station and Nearby Farmland –Case Study for Kumagaya City in Japan–

“…Accurate temperature data are essential for these purposes (Fukuoka and Yoshimoto 2012), since crop productivity and quality are sensitive to temperature (e.g. Morita 2008;Maruyama et al 2013 for paddy rice).…”

Breeding efforts to mitigate damage by heat stress to spikelet sterility and grain quality

“…In the Japonica cultivars, Akita-komachi and nipponbare (Maruyama et al, 2013;Matsui et al, 2001), Hitomebore (Maruyama et al, 2013), and Todorokiwase (Tenorio et al, 2013) are classified as considerably heat-tolerant genotypes. In Indica cultivars, IR24 and IR36 (Maruyama et al, 2013), Ciherang, AdT36, increase when panicles are exposed to high temperatures during grain filling. Chalky grains induced by heat stress are associated with reduction in head rice yield and market values.…”

“…Rice is most susceptible to heat stress at flowering, and previous chamber experiments showed that temperatures above 32-36 °C cause high spikelet sterility (Jagadish et al, 2008;Matsui et al, 1997aMatsui et al, , 1997bMatsui et al, , 2001Maruyama et al, 2013;Prasad et al, 2006;Satake & Yoshida, 1978;Weerakoon et al, 2008). Heat-induced spikelet sterility (HISS) at flowering is associated with reduction in grain yield.…”

Panicle emergence pattern and grain yield of rice plants in response to high temperature stress

“…The experiment was conducted using TGCs, as reported in our previous studies (Hamasaki et al, 2010;Maruyama et al, 2013), to expose rice plants to different temperatures. The TGCs at KO-ARC are pipe-framed greenhouses (3.6 m width × 3.0 m height × 30 m length) covered with 0.1-mm-thick polyolefin film (TokanAce-N; Tokan Kosan, Tokyo, Japan).…”

“…The timing of panicle emergence in rice plants is a key trait in an agronomic sense, as it determines the flowering season and the beginning of the ripening phase, and consequently affects grain filling and yield formation based on climatic conditions after flowering. Therefore, the timing of panicle emergence, or flowering, in rice has been studied extensively from diverse viewpoints, such as breeding and genetics (Yano et al, 1997;Nakagawa et al, 2005), anthesis and fertilization (Prasad et al, 2006;Mohammed et al, 2011;Tanaka et al, 2014), and climatic responses and phenology (Yin and Kropff, 1996;Tao et al, 2006;Wakiyama et al, 2013).…”