Abstract
Predicted climate changes, in particular, the increased dimension and frequency of heat waves, are expected to affect crop growth in the future seriously. Hybrid rice relies on seed production from male sterile and restorer lines. Experiments were conducted over two consecutive years to compare the high temperature tolerance of parents of different hybrid rice combinations, in terms of fertility rate, flowering pattern, pollination and physiological parameters of the lodicule. Three male sterile lines and a broad compatibility restorer line (as pollen donor and conventional variety as well) were grown to heading stage and then treated with average daily temperatures of 26°C (range 23–30°C), 28°C (25–32°C), and 30°C (26–34°C), respectively, continued for 5–7 days each in a natural light phytotron which simulated the local typical high temperature weather in the field. The results indicated that male sterile lines were more sensitive to high temperature than the restorer line for fertility rate, and the sensitivity varied between varieties. The fertility rate of the restorer line was maintained at about 90% under the high temperature treatments, while it decreased in the male sterile lines by 23.3 and 48.1% at 28 and 30°C, respectively. The fertility rate of the most sensitive line declined by 70%, and the tolerant line declined by 34% at 30°C. Glume closure in the male sterile lines was a major reason for the reduced fertility rate under high temperature, which is closely correlated with carbohydrates content and the vascular bundle pattern in the lodicule. The present study identified a useful trait to select male sterile lines with high temperature tolerance for seed production.
Highlights
Rice is the staple food for more than half of the world’s population
The three male sterile lines have been widely used for commercial hybrid seed production; Guangzhan 63S and Y58S have been used in two-line hybrid seed production and II-32A has been used in three-line hybrid seed production
Our study showed significant reductions in the fertility rate of some male sterile lines when the average daily temperature reached above 28◦C or the highest daily temperature reached 32◦C compared with 33.7◦C observed for conventional rice varieties (Matsui et al, 2000; Jagadish et al, 2011)
Summary
Rice is the staple food for more than half of the world’s population. Rice production in East Asia, Southeast Asia and African countries is important for global food security (Seck et al, 2012). Based on the Intergovernmental Panel on Climate Change (IPCC ) Fifth Assessment Report (Stocker et al, 2013), the globally averaged temperature in 2012 was 0.85◦C higher than in 1880. It is expected that this temperature increment may increase to more than 1.5◦C by the end of the 21st century, and the air temperature in China is likely to be 0.3–0.7◦C higher in the two decades. In the last 117 years, the Yangtze River Basin has had the highest average air temperatures (Tu et al, 1999) and more frequent heat waves than ever before
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