Climate warming worsens thermal resource utilization for practical rice cultivation in China.

Rice production is sensitive to climate change and significantly affected by warming in recent years. To what extent climate warming shifted rice phenology and varied thermal resource condition were explored across five agro-ecological zones in China, based on up-to-date observations of meteorology and rice cultivation in 1981-2020. It was clearly signaled that there was a general advance of 0.3-3.8 days in observed sowing date and a delay of 0.4-3.5 days in observed maturity date in 2001-2020 relative to 1981-2000 in major zones. A vacant time slice of 2.6-28.8 days between observed sowing date and potential sowing date, and a lag of 15.4-56.7 days in potential maturity date compared to observed maturity date were identified in 2001-2020. Within longer growing season, useful accumulated temperature increased by 76.7-117.6 °C·d in 2001-2020 relative to 1981-2000, while disactive accumulated temperature also increased. In Northeast China, actual rice cultivation was undergoing earlier sowing date than potential sowing date and longer growing duration than potential duration, yet leading to upward disactive accumulated temperature. The decrease in the thermal resource utilization in 2001-2020 relative to 1981-2000 was highlighted at 55.3-78.3% stations in major zones, with a decrement of 0.006-0.018 in average magnitude. The changes in thermal resource utilization unveiled that the shifts in actual rice cultivation still could not compensate for the suitability in thermal resource utilization benefited from climate warming.

Investigation of the antifungal activity of the dicarboximide fungicide iprodione against Bipolaris maydis.

Southern corn leaf blight (SCLB), mainly caused by Bipolaris maydis, is a destructive disease of maize worldwide. Iprodione is a widely used dicarboximide fungicide (DCF); however, its antifungal activity against B. maydis has not been well studied until now. In this study, the sensitivity of 103 B. maydis isolates to iprodione was determined, followed by biochemistry and physiology assays to ascertain the fungicide's effect on the morphology and other biological properties of B. maydis. The results indicated that iprodione exhibited strong inhibitory activity against B. maydis, and the EC50 values in inhibiting mycelial growth ranged from 0.088 to 1.712 µg/mL, with a mean value of 0.685 ± 0.687 µg/mL. After treatment with iprodione, conidial production of B. maydis was decreased significantly, and the mycelia branches increased with obvious shrinkage, distortion and fracture. Moreover, the expression levels of the osmotic pressure-related regulation genes histidine kinase (hk) and Ssk2-type mitogen-activated protein kinase (ssk2) were upregulated, the glycerin content of mycelia increased significantly, the relative conductivity of mycelia increased, and the cell wall membrane integrity was destroyed. The in vivo assay showed that iprodione at 200 µg/mL provided 79.16% protective efficacy and 90.92% curative efficacy, suggesting that the curative effect was better than the protective effect. All these results proved that iprodione exhibited strong inhibitory activity against B. maydis and provided excellent efficacy in controlling SCLB, indicating that iprodione could be an alternative candidate for the control of SCLB in China.

Assessing multi-risk characteristics of heat and cold stress for rice across the southern parts of China.

Rice (Oryza sativa) growth is always threatened by heat as well as cold stress, when it is exposed to natural environment. Heat growing degree hours (HGDH) and cold growing degree hours (CGDH1 and CGDH2) were firstly proposed to quantify heat and cold stress occurred during different growing stages. Information diffusion method was effectively used to fit the distribution and estimate probability of single stress at each station, with an advantage of no limitation in data series. In terms of single stress, highest probability was seen in HGDH, followed by CGDH1 and CGDH2. Seven copula functions, i.e., normal and t, Gumbel-Hougaard, Clayton, Frank, Joe, and Ali-Mikhail-Haq, were applied to fit the distribution of multi-stress with significant dependence, and simple calculation based on single stress was used to quantify the probability for multi-stress with independence. In these copulas, t was the most chosen one in the fitting of HGDH-CGDH1, HGDH-CGDH2, CGDH1-CGDH2, and HGDH-CGDH1-CGDH2, selected by the statistic of Akaike information criterion. Regarding bi-stress, higher joint probability was in HGDH-CGDH1, relative to HGDH-CGDH2 and CGDH1-CGDH2. As expected, the co-occurrence probability of tri-stress was lower than that of bi-stress in the magnitude and spatial extent, while joint probability of tri-stress was larger. Given the condition of occurrence of HGDH or CGDH1, the joint probability of HGDH-CGDH1 was higher than other pairs of bi-stress and tri-stress. It was special that higher joint probability of CGDH1-CGDH2 was detected under the condition of CGDH2 relative to CGDH1. Joint probability of tri-stress was lower under the condition of HGDH-CGDH1, in comparison with HGDH-CGDH2 and CGDH1-CGDH2. Hazards of single stress and multi-stress were expressed by the integration of intensity of stress index and corresponding probability. Most consistent conclusions agreed that central Fujian, Zhejiang, and northeastern Jiangxi were exposed to higher hazard, derived from not only single stress but also multi-stress. These results can be helpful in provision of information regarding prevention and adaptation strategies for rice cultivation as a response to extreme temperature stress.