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Sake, which is produced mainly from japonica rice (Oryza sativa subsp. japonica), is one of the most important alcohol products in Japan. In this study, we aimed to investigate a hypothesis that the early root endophytic bacterial communities in Japanese sake rice cultivars would be distinct from those in table rice cultivars, comparing four sake rice cultivars and two table rice cultivars. Rice roots in the vegetative stage were collected 0, 3, and 6 weeks after transplanting, and 16S rRNA gene amplicon sequencing revealed significant differences in bacterial community composition diversity between the sake and table rice cultivars. The root endophytic bacterial communities at the transplanting differed significantly between the rice cultivars, indicating differences in each seed-derived endophytic community. After an overall dominance of Pantoea and Methylobacterium-Methylorubrum at the transplanting, the endophytic community was gradually replaced by soil-derived bacteria that varied by the rice cultivars. Notably, PERMANOVA results showed that the rice endophytic bacterial community composition differed significantly between the sake and table rice cultivars (p < 0.001). These results highlight the distinct root endophytic bacterial composition in the sake rice cultivars compared to those in the table rice cultivars, supporting our hypothesis.

Rice is a major source of carbohydrates. Resistant starch (RS) is digested in the human small intestine but fermented in the large intestine. This study investigated the effect of consuming heat-treated and powdered brown rice cultivars ‘Dodamssal’ (HBD) and ‘Ilmi’ (HBI), with relatively high and less than 1% RS content, respectively, on the regulation of glucose metabolism in humans. Clinical trial meals were prepared by adding ~80% HBI or HBD powder to HBI and HBD meals, respectively. There was no statistical difference for protein, dietary fiber, and carbohydrate content, but the median particle diameter was significantly lower in HBI meals than in HBD meals. The RS content of HBD meals was 11.4 ± 0.1%, and the HBD meals also exhibited a low expected glycemic index. In a human clinical trial enrolling 36 obese participants, the homeostasis model assessment for insulin resistance decreased by 0.05 ± 0.14% and 1.5 ± 1.40% after 2 weeks (p = 0.021) in participants in the HBI and HBD groups, respectively. The advanced glycation end-product increased by 0.14 ± 0.18% in the HBI group and decreased by 0.06 ± 0.14% in the HBD group (p = 0.003). In conclusion, RS supplementation for 2 weeks appears to have a beneficial effect on glycemic control in obese participants.

The current work is designed to search for suitable rice (Oryza sativa L.) cultivars capable of growing on Cr(VI), hexavalent chromium contaminated soils. The study of tolerance and phenotypical changes of three selected rice cultivars like Bina Dhan 11, Kalachampa, and Pratikshya, at the seedling stages, was done under soil Cr(VI) concentrations up to 300 mg.kg-1 of soil. The 7-day seedlings of these rice cultivars growing on Cr(VI) treated soils were found to exhibit a significant reduction in shoot and root growth at p ≤ 0.05. The experimental results support that 7-day seedlings of Bina Dhan 11 were found to be the best among the three cultivars under soil Cr(VI) stress conditions. The present work may help in selecting suitable rice cultivar for paddy cultivation on Cr(VI) contaminated crop lands present in mining and industrial belts. Further work on this aspect may be useful in increasing rice productivity, catering to the increase in demand for food.

Raman spectroscopy was applied to characterize at the molecular scale the nutritional quality of the Japanese Koshihikari rice cultivar in comparison with other renowned rice cultivars including Carnaroli from Italy, Calrose from the USA, Jasmine rice from Thailand, and Basmati from both India and Pakistan. For comparison, two glutinous (mochigome) cultivars were also investigated. Calibrated and validated Raman analytical algorithms allowed quantitative determinations of: (i) amylopectin and amylose concentrations, (ii) fractions of aromatic amino acids, and (iii) protein content and secondary structure. The Raman assessments non-destructively linked the molecular composition of grains to key nutritional parameters and revealed a complex intertwine of chemical properties. The Koshihikari cultivar was rich in proteins (but with low statistical relevance as compared to other investigated cultivars) and aromatic amino acids. However, it also induced a clearly higher glycemic impact as compared to long-grain cultivars from Asian countries. Complementary to genomics and wet-chemistry analyses, Raman spectroscopy makes non-destructively available factual and data-driven information on rice nutritional characteristics, thus providing customers, dietitian nutritionists, and producers with a solid science-consolidated platform.

Root-associated microbial communities have been widely studied in the model plant Arabidopsis thaliana, but have been much less explored in agronomically important crops. Here, we used deep pyrosequencing of bacterial 16S rRNA to identify and characterize the root-associated microbial community of three traditional rice cultivars (representing indica and japonica subspecies and a hybrid) cultivated in typical paddy soils from China. We separated the root microbiota into endosphere and rhizosphere compartments, which were found to be the major determinant of variation in the total root microbial community. The microbial communities in each rhizocompartment were strongly influenced by soil type, while rice genotype exhibited a small but significant influence on both endosphere and rhizosphere microbiota. Pairwise comparisons showed that the endophytic bacterial community of indica rice differed significantly from that of japonica rice, while no remarkable differences were noted when comparing the community of indica vs. hybrid or japonica vs. hybrid. A core functional rice endophytic microbiota was identified, which accounted for relative abundances of up to 72.5% of the total microbial community. The 88 core root operational taxonomic units (OTUs) mainly belonged to the phylum Proteobacteria specifically Alphaproteobacteria, Betaproteobacteria, and Deltaproteobacteria. These results clarify the rice root-associated microbial community assemblage and facilitate the construction of an artificial core root microbiota to promote plant growth and resistance.

Rice blast, caused by the Magnaporthe oryzae fungus, is one of the most devastating rice diseases worldwide. Developing resistant varieties by pyramiding different blast resistance (R) genes is an effective approach to control the disease. However, due to complex interactions among R genes and crop genetic backgrounds, different R-gene combinations may have varying effects on resistance. Here, we report the identification of two core R-gene combinations that will benefit the improvement of Geng (Japonica) rice blast resistance. We first evaluated 68 Geng rice cultivars at seedling stage by challenging with 58 M. oryzae isolates. To evaluate panicle blast resistance, we inoculated 190 Geng rice cultivars at boosting stage with five groups of mixed conidial suspensions (MCSs), with each containing 5–6 isolates. More than 60% cultivars displayed moderate or lower levels of susceptibility to panicle blast against the five MCSs. Most cultivars contained two to six R genes detected by the functional markers corresponding to 18 known R genes. Through multinomial logistics regression analysis, we found that Pi-zt, Pita, Pi3/5/I, and Pikh loci contributed significantly to seedling blast resistance, and Pita, Pi3/5/i, Pia, and Pit contributed significantly to panicle blast resistance. For gene combinations, Pita+Pi3/5/i and Pita+Pia yielded more stable pyramiding effects on panicle blast resistance against all five MCSs and were designated as core R-gene combinations. Up to 51.6% Geng cultivars in the Jiangsu area contained Pita, but less than 30% harbored either Pia or Pi3/5/i, leading to less cultivars containing Pita+Pia (15.8%) or Pita+Pi3/5/i (5.8%). Only a few varieties simultaneously contained Pia and Pi3/5/i, implying the opportunity to use hybrid breeding procedures to efficiently generate varieties with either Pita+Pia or Pita+Pi3/5/i. This study provides valuable information for breeders to develop Geng rice cultivars with high resistance to blast, especially panicle blast.

Rice production affects the food security and socioeconomic status of over half the world’s population. Rice-producing countries, however, are facing population growth, reduction in rice planting area, and global change. Understanding the trends of rice production and major determinants is key to regulating rice production. We thus analyzed the trends of rice production and related determinants in China from 2001 to 2021, revealing that the annual rice production (TRP) has risen steadily (r = 0.929, p < 0.0001) in recent 20 years. TRP in 2021 was 19.9% higher than that in 2001, which was primarily achieved by the increment of middle rice production (MRP). MRP increased by 46.2% from 2000 to 2018, and grain yield per unit area (GPA) was the largest in middle rice. The enhancement of GPAs is significantly correlated with the consumption of agricultural resources and the number of released rice cultivars, but variations exist. TRP and GPA vary in different provinces; Hunan (25 ± 2 megatons) and Xinjiang (8364 ± 806 kg/hectare) show the largest values, respectively. TRP could be further increased by 13.8% by improving MRP. The results suggest that rice production in China has a large potential to be further improved through regulations.

In order to explore the influence of stored cereal volatiles on the behavior of Sitophilus oryzae, the olfactory responses of adult rice weevils to the volatiles of different rice cultivars [Red brown rice (RBR), Daohuaxiangmi (DHXM), Baishuigongmi (BSGM), Yashuixinmi (YSXM), and white glutinous rice (WGR)] were studied using electroantennography (EAG) and behavioural bioassays in different types of olfactometers. S. oryzae showed significantly different preferences for these rice cultivars, in the order RBR > DHXM = YSXM ≥ BSGM > WGR. Furthermore, 26 components were identified in the volatile profile of RBR. Nonanal (29.37%), hexanal (16.08%), and 1-octen-3-ol (8.83%) were the most abundant compounds. EAG recordings showed that the antennae of S. oryzae were able to perceive these three compounds in a dose-dependent manner. The compounds elicited significant EAG responses at various concentrations, with the strongest responses at 100 μg μL −1 . S. oryzae had a significant positive behavioural response to nonanal, hexanal, and 1-octen-3-ol at various concentrations, with the most attractive being 50, 100, and 100 µg µL −1 , respectively. The olfactory preferences of S. oryzae , based on a comparison of these compounds at their optimal concentrations, were nonanal > 1-octen-3-ol = hexanal. These results indicated that the volatiles of the preferred rice cultivar (RBR) were perceived by the peripheral olfactory system of S. oryzae adults and individually elicited positive chemotaxis. These findings offer new insights into the mechanism of host preferences of stored-grain pests. Nonanal showed the greatest potential for use as a novel monitoring and control tool against this storage-beetle pest.

AimsAtmospheric CO2 and O3 concentrations have been increasing, with important consequences on the biogeochemical cycle in agroecosystems. However, little is known about the interactive effect of elevated CO2 and O3 on soil nitrogen cycling processes mediated by soil microbes.MethodsWe conducted open-top chamber facilities to assess the impacts of short-term elevated CO2 and O3 on soil nitrification and denitrification rates, and the abundances of soil N cycling-related genes for two rice cultivars (Nanjing 5055 vs. Wuyujing 3) in paddy soil.ResultsElevated CO2 potentially increased the abundance of nitrification-related genes (AOA amoA + 40.9%, AOB amoA + 23.4%, nxrB + 8.6%). Elevated O3 potentially reduced the abundances of AOA and AOB amoA, nxrA, and nxrB by 3.1–23.8%. Combined treatment showed detrimental effects on the abundances of AOA and AOB amoA, and nxrA by 17.6–36.0%, indicating that short-term elevated O3 exerted stronger effects on soil nitrification than CO2. Similarly, both individual and combined treatments decreased the abundance of comammox amoA. Additionally, the individual and combined treatments stimulated the abundance of denitrification-related genes by 4.2–11.9%, except narG. Accordingly, the denitrification rates were significantly increased by 77.2–89.1% under all treatments, particularly for Nanjing 5055. Furthermore, the abundance of nifH mediating N fixation was reduced by elevated CO2 and combined treatments.ConclusionsElevated CO2 and O3 may promote soil N losses by increasing the abundances of denitrification-related genes, restraining N fixation-related genes, and potentially threatening food production, highlighting the detrimental impacts of ongoing elevated CO2 and O3 on soil N retention capacity in the future.

While biochar use in agriculture is widely advocated, how the effect of biochar on plant growth varies with biochar forms and crop genotypes is poorly addressed. The role of dissolvable organic matter (DOM) in plant growth has been increasingly addressed for crop production with biochar. In this study, a hydroponic culture of rice seedling growth of two cultivars was treated with bulk mass (DOM-containing), water extract (DOM only), and extracted residue (DOM-free) of maize residue biochar, at a volumetric dosage of 0.01, 0.05, and 0.1%, respectively. On seedling root growth of the two cultivars, bulk biochar exerted a generally negative effect, while the biochar extract had a consistently positive effect across the application dosages. Differently, the extracted biochar showed a contrasting effect between genotypes. In another hydroponic culture with Wuyunjing 7 treated with biochar extract at sequential dosages, seedling growth was promoted by 95% at 0.01% dosage but by 26% at 0.1% dosage, explained with the great promotion of secondary roots rather than of primary roots. Such effects were likely explained by low molecular weight organic acids and nanoparticles contained in the biochar DOM. This study highlights the importance of biochar DOM and crop genotype when evaluating the effect of biochar on plants. The use of low dosage of biochar DOM could help farmers to adopt biochar technology as a solution for agricultural sustainability.