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(1) Background: Sheath blight is one of the most economically significant rice diseases worldwide. A study was conducted in order to find the relationship and impact of the amount of nitrogen (N) and phosphorus (P) application on the hybrid rice population microclimate and the severity of sheath blight. (2) Methods: Four N and four P application levels were used to determine their impact on plant type, temperature, and humidity variation in different positions of population and the severity of sheath blight in the later stage. (3) Results: We found that N and P application levels could affect the plant type and change the population temperature and humidity by increasing the leaf length and leaf angle. (4) Conclusions: N application had a more significant (p < 0.05) impact on the plant type. High N application caused decreased temperature (hybrid rice population), while increased humidity (especially the population base layer at grain filling stage) resulted in severe sheath blight. High P application had similar impacts; however, P application increased material and nitrogen transport in plants and reduced the severity of sheath blight. [ABSTRACT FROM AUTHOR]

The architecture of rice plant represents important and complex agronomic traits, such as panicles morphology, which directly influence the microclimate of rice population and consequently grain yield. To enhance yield, modification of plant architecture to create new hybrid cultivars is considered a sustainable approach. The current study includes an investigation of yield and microclimate response index under low to high plant density of two indica hybrid rice R498 (curved panicles) and R499 (erect panicles), from 2017 to 2018. The split-plot design included planting densities of 11.9–36.2 plant/m2. The results showed that compared with R498, R499 produced a higher grain yield of 8.02–8.83 t/ha at a higher planting density of 26.5–36.2 plant/m2. The response index of light intensity and relative humidity to the planting density of R499 was higher than that of R498 at the lower position of the rice population. However, the response index of temperature to the planting density of R499 was higher at the upper position (0.2–1.4%) than at the lower position. Compared with R498, R499 at a high planting density developed lower relative humidity (78–88%) and higher light intensity (9900–15,916 lx) at the lower position of the rice population. Our finding suggests that erect panicles are highly related to grain yield microclimatic contributors under a highly dense rice population, such as light intensity utilization, humidity, and temperature. The application of erect panicle rice type provides a potential strategy for yield improvement by increasing microclimatic conditions in rice. [ABSTRACT FROM AUTHOR]

Leaf pigment content is a complicated quantitative trait which results from the cooperation of multiple related genes or quantitative trait loci (QTL) in rice. So far, more than 600 QTL for leaf pigment content has been reported. However, most QTL positions could not be directly compared with each other. In this study, our goal was to analyze consistent QTL regions affecting leaf pigment content by applying a genome wide QTL meta-analysis approach. 20 QTL related to leaf pigment content were detected at 5 different growth periods in 134 recombinant inbred lines (RILs) from a typical Indica-Japonica cross derived from PA64s and 9311 (two parents of super hybrid rice Liangyoupei 9). There was a candidate gene GLTP in the region of 3 QTL (qFS_Chla4, qFS_Chla+b4, and qFS_Car4), which related to component of chloroplast thylakoid membranes. After sequencing and qRT-PCR analysis, the gene showed significant difference in parents of the RILs. Meta-analysis was performed on 618 QTL collected from 38 previous studies. Consequently, a total of 64 MQTL (Meta-QTL) were obtained, of which 58.95% confidence intervals (CI) were smaller than the average Cl of the original QTL. In addition, 64 MQTL covered 6 of 20 QTL detected. Among them, four main QTL were included in 3 MQTL, and phenotypic variation of 21 MQTL was greater than 20%. The traits with higher number of QTL had higher number of MQTL, and candidate genes in overlapping MQTL include multiple effects. 7 candidate genes related to leaf pigment content were found in 4 MQTL spanning physical intervals < 0.5 Mb. These findings are not only anticipated to help molecular marker-assisted selection and pyramiding, but also contribute to determine candidate genes that regulate pigment content. [ABSTRACT FROM AUTHOR]

Extreme weather and global warming are drastic agricultural issues causing water scarcity. Under these conditions, it is vital to select drought-tolerant hybrid super rice breeds to enhance the rice yield in dry areas. In the current study, a dry-shed experiment was carried out in 2019–2020 to analyze the root growth, gene expression, and enzyme activity of hybrid rice Deyou4727, its parent (Dexiang074B * Chenghui727), taking IR64 as a universal control. Results showed that Deyou4727 and its maintainer line Dexiang074B produced more roots (30–50 cm soil) and higher enzymatic activity than IR64 during the drought stress period, indicating a good drought-tolerant capacity for Deyou4727. The distribution and morphology of the root system in Deyou4727 were inherited by the maintainer line Dexiang074B, which was confirmed by the high upregulation of DRO1 and OsPIN1b gene expression and the sharing of the same ORF region in both the hybrid rice varieties. However, the DRO1 gene ORF study showed that, in the case of the control IR64, 'A' was missing at the 4th exon of the DRO1 gene, which may explain the shallow and weak root architecture system of IR64. The drought-tolerance capacity of Deyou4727 can be used in the future as a drought-resistant germplasm for breeding more drought-tolerant hybrid rice varieties. [ABSTRACT FROM AUTHOR]

Incorporating oilseed-rape straw in soil is one of the effective methods for enhancing the use efficiency of agricultural resources in the rape-rice rotation system. However, the impacts of oilseed-rape straw incorporation on root growth and dynamic changes in soil are still unclear. In order to provide a deeper understanding of the oilseed rape straw return on rice growth and productivity, the experiment was conducted in the field and in a specially-designed pots system from 2016 to 2017 by means of two straw returning methods and four straw returning amounts. In the early stage of rice growth (0–36 days after rice transplanting) the straw returning treatments decreased 1.0–8.6 mg/plant in bleeding density and 0.10–6.11, 0.06–0.31, and 0.52–0.84 μmol/(g h) in the activity of glutamine synthetase (GS), glutamic-oxalacetic transaminase (GOT), and glutamic-pyruvic transaminase (GPT), respectively. Oilseed rape straw returned by mulching induced negative impacts on new germinating roots in 0–10 cm of soil, while the negative impacts were observed on roots in 10–30 cm of soil for straw returned by plowing. In the later stage of rice growth (56–75 days after rice transplanting), oilseed rape straw returning produced some positive impacts on rice roots, which enhanced the yield of rice. Conclusively, our findings suggested that dynamic root growth and the activity of root enzymes are two major factors behind the slow reviving of rice after transplanting in the straw returning field. Plowing is a more appropriate method of straw returning than mulching in the rape-rice rotation system in the Sichuan basin area, with a straw incorporation rate of 3.0 t/hm2. [ABSTRACT FROM AUTHOR]

Drought is one of the major factors limiting rice yield worldwide. A total of 46 hybrid rice varieties were chosen to investigate their root distribution and their response to drought. A field experiment was carried out in a dry shed building to evaluate the drought tolerance capacity of hybrid rice varieties on the basis of CTIRDE (complex tolerance index of rice under drought environment) values. Next, the experiment was conducted in a specially designed pot system and seed bags to analyze the root distribution and activity of antioxidant enzymes in different rice varieties. Moreover, the DEEPER ROOTING 1 (DRO1) gene was sequenced to elucidate its role in the root distribution of typical rice varieties. On the basis of CTIRDE values, the 46 hybrid rice varieties were classified as tolerant (CTIRDE ≥ 0.75), semi-tolerant (0.75 > CTIRDE > 0.65), or sensitive (CTIRDE ≤ 0.65) to drought stress. The tolerant varieties (Chuanguyou208 and Deyou4727) displayed a significantly larger length, had higher number and weight of roots in the 30–50 cm soil layer, and exhibited a significantly higher activity of Superoxide dismutase (SOD) and Peroxidase (POD) enzymes in roots during the drought stress period. The DRO1 gene sequencing results revealed that the tolerant and sensitive varieties exhibited a single-nucleotide polymorphism (SNP) in the 3-exon region, and the tolerant varieties (Chuanguyou208 and Deyou4727) exhibited a larger root growth angle with the horizontal axis, hence developing a deeper root system as compared with the other two group varieties. A significant correlation was found not only between the DRO1 gene and root distribution but also between DRO1 and the activity of SOD and POD enzymes. Conclusively, as a key feature, a deep root system enabled tolerant rice varieties (Chuanguyou208 and Deyou4727) to avoid drought stress by absorbing more water stored in deep soil layers. The root distribution, activity of POD and SOD enzymes in roots, and DRO1 gene can be used to screen tolerant rice varieties that can survive better under drought stress during the seedling stage of rice growth. [ABSTRACT FROM AUTHOR]

Fertilizer with nitrogen and phosphorus is one of the key elements influencing rice quality. In this study, the impact of nitrogen (N) (0, 90, 150, 270 kg N ha−1) and phosphorus (P) fertilizer (0, 15, 30, 60 kg P ha−1) on the physicochemical characteristics of two indica rice types were examined. N fertilizer had a bigger impact on the hybrid rice's quality than P fertilizer. Different rice cultivars with more N and P fertilizer had lower amylose levels and higher protein levels. Adding N fertilizer increased the peak viscosity (PV), Breakdown (BD), consistency (CS), crystallinity, and hardness of rice variety with low amylose content (LAC), decreased setback (SB) and stickiness, made the taste quality worse; However, the decrease of gelatinization enthalpy (ΔHgel) of rice variety with high amylose content (HAC) to reduce the taste quality. Proper amount of P fertilizer can improve the taste quality by reducing PV, BD, hardness and increasing hold viscosity (HPV), SB and stickiness. • N and P fertilizer influenced amylose and protein content of rice varieties. • Excessive phosphorus fertilizer reduced the taste quality of rice. • Appropriate fertilizer should be used for planting rice of different amylose types. [ABSTRACT FROM AUTHOR]