Asymmetric Differences in the Effects of Average Air Temperature and Solar Radiation on Early Rice and Late Rice Yield

China is the world’s largest rice producer. Thus, the stability of rice production plays a decisive role in food security. Among the types of rice, double rice (including early rice and late rice) accounts for the largest proportion of rice in China. Climate change is widely expected to affect rice yields. Studying the response of double rice yield to climate change will benefit strategic decisions related to future crop adaptation. In this paper, the relationship between climate factors and the yield of double rice during 1992–2013 in south China was analysed to determine the responses of double rice yield to climate change. The results showed that the daily average air temperature during the early rice and late rice growing seasons increased by 0.34 °C and 0.68 °C, 0.29 °C and 0.67 °C, and 0.11 °C and 0.31 °C per 10-year period in the northern subtropical zone (NST), middle subtropical zone (MST) and south subtropical zone (SST), respectively, in the last 20 years. The change trend in solar radiation was not obvious, but it fluctuated greatly. A 1 °C increase in average air temperatures decreased early rice yield by 5.36% and 2.16% in SST and MST, respectively; decreased late rice yield by 0.75% and 1.43% in MST and NST, respectively; and increased late rice yield by 3.93% in SST. A solar radiation increases of 100 MJ m−2 increased early rice yield by 1.02%, 1.54% and 1.71% in SST, MST and NST, respectively, and decreased late rice yield by 0.89% in SST. We found that annual average temperatures of 17.3 °C and 18.6 °C were the early rice and late rice yield variation thresholds, respectively; in addition, above the background temperature in south China, the early rice yield will decrease and the late rice yield will increase.

Simulation of the critical nitrogen dilution curve in Jiangxi double-cropped rice region based on leaf dry matter weight

In order to investigate the feasibility of using rice critical nitrogen concentration as a nitrogen nutrition diagnosis index, a two-year positioning field gradient experiment using four rice varieties and four nitrogen levels (0, 75, 150, 225 kg·ha–1 for early rice; 0, 90, 180, 270 kg·ha–1 for late rice) was conducted for early and late rice. The critical dilution curves (Nc%) of the double-cropped rice based on leaf dry matter (LDM) were constructed and verified using the field data. Two critical nitrogen dilution curves and nitrogen nutrition indexes (NNI) of rice LDM were constructed for early rice [Nc% = 2.66LDM−0.79, R2 = 0.88, NNI ranged between 0.29–1.74, and the average normalized root mean square error (n-RMSE = 19.35%)] and late rice [Nc% = 7.46LDM−1.42, R2 = 0.91, NNI was between 0.55–1.53, and the average (n-RMSE = 15.14%)]. The relationship between NNI and relative yield was a quadratic polynomial equation and suggested that the optimum nitrogen application rate for early rice was sightly smaller than 150 kg·ha–1, and that for late rice was about 180 kg·ha-1. The developed critical nitrogen concentration dilution curves, based on leaf dry matter, were able to diagnose nitrogen nutrition in the double-cropped rice region.

Localised expression of OsIAA29 suggests a key role for auxin in regulating development of the dorsal aleurone of early rice grains

Endosperm of rice and other cereals accumulates high concentrations of the predominant in planta auxin, indole-3-acetic acid (IAA) during early grain development. However, IAA signalling and function during endosperm development are poorly understood. Here, we report that OsYUC12 (an auxin biosynthesis gene) and OsIAA29 (encoding a non-canonical AUX/IAA) are both expressed exclusively in grains, reaching a maximum 5 to 6 days after pollination. OsYUC12 expression is localized in the aleurone, sub-aleurone and embryo, whereas OsIAA29 expression is restricted to a narrow strip in the dorsal aleurone, directly under the vascular bundle. Although rice has been reported to lack endosperm transfer cells (ETCs), this region of the aleurone is enriched with sugar transporters and is likely to play a key role in apoplastic nutrient transfer, analogous to ETCs in other cereals. OsIAA29 has orthologues only in grass species; expression of which is also specific to early grain development. OsYUC12 and OsIAA29 are temporally co-expressed with two genes (AL1 and OsPR602) previously linked to the development of dorsal aleurone or ETCs. Also up regulated at the same time are a cluster of MYB-related genes (designated OsMRPLs) homologous to ZmMRP-1, which regulates maize ETC development. Wheat homologues of ZmMRP-1 are also expressed in ETCs. Although previous work has suggested that other cereals do not have orthologues of ZmMRP-1, our work suggests OsIAA29 and OsMRPLs and their homologues in other grasses are part of an auxin-regulated, conserved signalling network involved in the differentiation of cells with ETC-like function in developing cereal grains.Main ConclusionNon-canonical AUX/IAA protein, OsIAA29, and ZmMPR-1 homologues, OsMRPLs, are part of an auxin-related signalling cascade operating in the dorsal aleurone during early rice grain development.

Research on correlation analysis and prediction model of agricultural climate factors based on machine learning

This article uses machine learning technology to analyze the correlation of climate factors that affect crop yields, and conduct prediction and comprehensive evaluation to guide agricultural production. This paper selects early rice crops in Guangxi as the research object. Based on the climatic data of early rice planting areas in Guangxi from 1990 to 2017, a cart decision tree is constructed to generate a random forest model to analyze the correlation between early rice yield and climatic factors in each growth period, and obtain the various growth periods The ranking of the importance of climatic factors on the yield, thus forming the basis for calculating the weights of the climatic factors in each growth period of early rice; based on the climatic data in Guilin, Guangxi from 2008 to April to July 2017, predicted by the long and short-term memory network Guilin's various climate data from April to July 2018.

Transcriptomic, proteomic, and physiological comparative analyses of flooding mitigating low temperature stress on direct-seeded early indica rice at seedling stage

Background Low temperature (LT) often occurs at seedling stage in early rice-growing season, especially for direct-seeded early-season indica rice seedlings, and adopting flooding irrigation could mitigate LT damage. However, it is not clear on the response mechanisms of a mitigating effect on LT stress at early rice seedling stage. Results In this study, LT stress with 10/6°C (day/night), LT accompanied by flooding (LTF) and CK (control) treatments were established for 3d to aim to determine the response mechanisms on physiological, transcriptomic, and proteomic of direct-seeded rice seedlings at seedling stage. The results showed that the chloroplasts was severely degraded, thylakoid lamellae were seriously damaged and osmiophilic body increased gradually in LT contrast to CK, but LTF could alleviate the damage of low temperature on chloroplast structure. Compared with LT, LTF significantly increased the contents of Rubisco, chlorophyll, PEPCK, ATP and GA3 of rice seedlings whereas significantly decreased soluble protein, MDA and ABA content, suggesting the higher photosynthetic traits, antioxidant ability and better growth characteristic, although it could also affect the physiological activity contrast to CK. The identified differentially expressed genes and differentially expressed proteins indicated that photosynthesis metabolism pathway, reactive oxygen species and metabolic regulation had significant differences between LT and LTF stress, which were the main reasons that reduced the LT damage of rice seedlings for LTF. Conclusions Our results could provide comprehensive interpretation of physiological characteristics, genes and proteins expression changes in low temperature and low temperature flooding.