Cadmium (Cd) is a kind of heavy metal. Cadmium pollution in paddy fields will accumulate a large amount of cadmium in rice, which will affect the growth and development of rice. In addition, long-term consumption of rice contaminated with Cd can harm human health. In this study, four rice varieties with high Cd accumulation (S4699, TLY619, JHY1586, QLY155) and four varieties with low Cd accumulation (YY4949, CYJ-7, G8YXSM, MXZ-2) were screened through field experiments for two consecutive years (2021 and 2022) and differences in antioxidant enzyme systems and expression of genes in their organs were analyzed. The total Cd content showed as follows: indica rice > japonica rice, high-Cd-accumulation variety > low-Cd-accumulation variety, and the total Cd content of each organ of rice showed root > stem > leaf > grain. The results of the antioxidant enzyme system showed that the contents of malondialdehyde (MAD), reduced glutathione (GSH), oxidized glutathione (GSSH), and peroxidase (POD) were positively correlated with the total Cd content in rice, and superoxide dismutase (SOD) showed the opposite performance in the leaves. There was no correlation between catalase (CAT) and Cd content, but CAT content decreased in leaves and grains and increased in roots and stems with increasing fertility. Based on this study, RT-qPCR was used to further validate the expression of Cd-uptake-related genes in different rice varieties. It was found that high expression of OsHMA3, OsCCX2, OsNRAMP5, and OsHMA9 genes promoted Cd uptake and translocation in rice, especially in rice varieties with high Cd accumulation. The high expression of OslRT1, OsPCR1, and OsMTP1 genes hindered Cd uptake by rice plants, which was especially evident in low-accumulating Cd rice varieties. These results provide an important theoretical reference and scientific basis for our in-depth study and understanding of the mechanism of cadmium stress tolerance in rice.

Rice growth is constantly challenged by severe environmental conditions, especially high-temperature stress, brought about by global warming. How to increase rice yields is a current issue in many countries. By analyzing the meteorological data from Anhui Province over the past 60 years, the frequency and level of high-temperature damage were comprehensively analyzed. On this basis, five indica rice varieties with strong high-temperature tolerance, relatively high yield and stable yield were selected by laboratory-simulated high-temperature and field high-temperature experiments: Longliangyou Huazan (LLYHZ), 9you-6 (9Y-6), Longliangyou-1988 (LLY-1988), Fengliangyou-4 (FLY-4) and Huanghuazan (HHZ). These are suitable for planting in the middle and lower reaches of the Yangtze River. This study provides a theoretical reference and scientific basis for the study of rice tolerance to high-temperature stress.