Light is one of the most important environmental factors that affect many aspects of plant growth, including chlorophyll (Chl) synthesis and flowering time. Here, we identified a rice mutant, yellow leaf and early flowering (ye1), and characterized the gene YE1 by using a map-based cloning method. YE1 encodes a heme oxygenase, which is localized to the chloroplasts. YE1 is expressed in various green tissues, especially in leaves, with a diurnal-rhythmic expression pattern, and its transcripts is also induced by light during leaf-greening. The mutant displays decreased Chl contents with less and disorderly thylakoid lamellar layers in chloroplasts, which reduced the photosynthesis rate. The early flowering phenotype of ye1 was not photoperiod-sensitive. Furthermore, the expression levels of Chl biosynthetic genes were downregulated in ye1 seedlings during de-etiolation responses to light. We also found that rhythmic expression patterns of genes involved in photoperiodic flowering were altered in the mutant. Based on these results, we infer that YE1 plays an important role in light-dependent Chl biogenesis as well as photoperiodic flowering pathway in rice.

Introduction: The application of nitrogen and phosphorus fertilizers is an important factors affecting the quality of rice, and different nitrogen-efficient rice varieties show significant differences in their response to nitrogen and phosphorus application.Methods: In this experiment, a low-nitrogen-high efficiency variety (Deyou 4727) and a high-nitrogen-high efficiency variety (Jingyou 781) were selected, and the changes in rice quality and differences in starch structure under nitrogen–phosphorus interaction treatments were determined.Results: Appearance, flavor, starch content and thermodynamic properties, endosperm cell arrangement, and starch granule morphology and size were significantly influenced by variety, nitrogen-phosphorus interactions, and their interaction effects. The effect of nitrogen fertilizer on quality was greater than that of phosphorus fertilizer. The whiteness and chalkiness rates of Deyou 4727 first decreased and then increased with increasing nitrogen fertilizer application, wheras the appearance quality of Jingyou 781 increased with increasing nitrogen fertilizer application. Starch crystallinity in Deyou 4727 first increased and then decreased with increasing nitrogen fertilizer application, whereas starch crystallinity in Jingyou 781 increased continuously with increasing nitrogen fertilizer application. The application of phosphorus fertilizer led to an increase in starch crystallinity in both nitrogen-efficient rice varieties, consistent with the response of different rice varieties to nitrogen and phosphorus in terms of appearance and chalkiness. With the increasing application of nitrogen and phosphorus fertilizers, the differences in the physicochemical properties and structure of starch became more significant.Discussion: High-nitrogen-efficient rice varieties can significantly improve appearance quality under high nitrogen conditions, and the interactions of medium-high nitrogen and low-medium phosphorus can lead to a significant decrease in starch thermal parameters and retention rate, thus improving rice cooking quality. Low-nitrogen-efficient rice varieties can also improve the quality of rice under low-medium-nitrogen conditions with appropriate application of phosphorus fertilizer.

Panicle-type structure is an important factor affecting rice yield, and an excellent panicle type has become a key indicator in rice breeding. In this study, the indica rice variety R766, which has an open panicle type, was obtained through natural mutation and hybrid selection. Through analyzing differences in panicle structure, panicle yield, and chemical composition between open panicle rice R766 and conventional panicle rice R2928, we found that the angles of the middle and lower branches in R766 were 186.99% and 135.93% greater than those in R2928, respectively. By comparing the grain-filling characteristics of different panicle positions in the two rice varieties, we found that the grain filling at the middle and lower panicle positions of R2928 was significantly lower, accompanied by an increase in the percentage of empty spikelets. However, in R766, the grain-filling rates in the middle and lower panicle positions were consistent with those in the upper panicle position, with significantly higher rates of grain filling and grain plumpness in the middle and lower panicle positions than in R2928. The empty grain rate at the lower panicle position of R766 was 15.25% lower than that of R2928, and the grain filling was 24.75% higher than that of R2928. Additionally, the variation in the 1000-grain weight of grains at different panicle positions in R766 was relatively small, with decreases of 1.55% and 0.38% in the middle and lower panicle positions, respectively, compared with the upper position, whereas R2928 showed decreases of 5.99% and 7.12% in the 1000-grain weight of grains at the middle and lower panicle positions, respectively, compared with the upper position. The cellulose content in the stems of R766 was 7.51% higher than that of R2928, with no significant difference in the cellulose content in the panicle axis and primary branches compared to R2928. The lignin content of the panicle axis in R766 was 8.03% higher than that in R2928, whereas there was no significant difference between the lignin content of the stems and primary branches. This preliminary study revealed the open panicle characteristics of R766 and the reasons for its high basal grain setting rate. This study provides a reference for promoting this open panicle-type indica rice variety to improve yield and disease resistance in environments with high humidity and low sunlight levels.

Nitrogen (N) and phosphorus (P) are key factors affecting rice yield. To study the effects of single application of nitrogen, phosphorus and their combined application on dry matter accumulation and yield of rice, two types of indica rice with contenting amylose contents, low amylose content (LAC) and high amylose content (HAC) were used as the test materials. Four different levels of nitrogen and phosphorus were applied (N0: 0, N1: 90, N2: 150, N3: 270 kg/hm²) and (P0: 0, P1: 15, P2: 30, P3: 60 kg/hm²). The application of N fertilizer alone and in combination with P effectively promote dry matter accumulation, translocation and increase yield. Under the N3P0 and N3P1 treatments, LAC and HAC achieved their highest yield of 10.03 t/hm² and 11.24 t/hm², respectively. representing increased of 46.19% and 29.05% compared to N0P0 treatment. Phosphorus application influenced dry matter accumulation at maturity and stem and leaf dry matter translocation to the panicle, translocation rates, and their contribution to the panicle, there by increasing yield. Effective panicles, spikelets per panicle, grain filling, stem and leaf dry matter translocation, stem and leaf dry matter translocation rate were significantly or highly significantly positively correlated with yield, and 1000-grain weight was highly significantly negatively correlated with yield, which were mainly increased by increasing panicle dry matter accumulation at maturity, the increase in the amount of increase in dry matter of panicle, the contribution rate of stem and leaf dry matter translocation to the panicle, the amount of stem and leaf dry matter translocation, and the rate of stem and leaf dry matter translocation to increase spikelets per panicle and the grain filling, and then to improvement of yield.

Delayed harvest of the previous crops of the rice-based rotation systems in Sichuan often leads to late transplanting of rice, thus extending the seedling age and shortening the effective growth period after the recovery of machine-transplanted seedlings. To improve the seedling survival rate and root growth after mechanical transplantation, as well as to promote tillering and regreening, a two-factor split-plot experiment was conducted. The main plot factor was the application of tiller fertilizer, and the subplot factor was the rice variety. Two fertilizer treatments were established, namely compound fertilizer (CK) and formula-specific tiller fertilizer (T1), where CK was used as the control. Four hybrid rice varieties were Longliangyou 534 (V1), Yunliangyou 332 (V2), Taifengyou 208 (V3), and Nei 6 You 6368 (V4). This study investigated the effects of the formulaic tiller fertilizer on the tillering rate, growth, development, and yield of machine-transplanted hybrid rice. The results showed that the effective panicle rate of rice increased by 1.26% under the T1 treatment compared to that under CK. Ten days after tillering, the length and fresh weight of tiller buds were 53.65% and 67.06% notably higher in T1 than those in CK. Additionally, the bud length was peaked in V4. Compared with CK, T1 treatment significantly increased the content of auxin (IAA), endogenous zeatin + zeatin riboside (Z + ZR), and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in tiller buds, while reducing the content of abscisic acid (ABA). Additionally, the formula-based tiller fertilizer remarkably enhanced the activity of Ca² ⁺ -Mg² ⁺ -ATPase. Compared to CK, the yield contributions of the main stem, primary tillers, and secondary tillers under treatment T1 increased by 6.96%, 18.42%, and 8.86% in 2022, respectively. Among all treatments, the V3T1 treatment resulted in the highest yields of the main stem and primary tillers, with yield contribution rates of 9.79% and 56.63%, respectively. In 2023, the yields of the main stem, primary tillers, and secondary tillers under T1 were higher than those under CK. Specifically, T1 had the highest yield contribution rate from primary tillers, whereas the contribution rate of secondary tillers was lower than that of CK. For the V4 growth stage, T1 also produced the highest yields of the main stem, primary tillers, and secondary tillers, at 988.49 kg/hm², 5,432.55 kg/hm², and 5,050.10 kg/hm², respectively. Therefore, formula-specific tiller fertilizer(T1) exhibited a significant yield-increasing effect on hybrid rice, with greater yield potential observed in V3 and V4. These findings provide a technical reference for mechanized transplantation cultivation of rice in the hilly rice-growing areas of northwestern Sichuan.

Rice is an important food crop, acting as the staple food for more than 50% of the global population. We selected seedlings (two sterile male lines: WA803A and JW803A) that had different cytoplasmic but the same nuclear composition and were heterogeneous. The maintainer line 803B was also used. We aimed to study their nitrogen uptake rate in different concentrations of NH₄⁺ and NO₃⁻ and explore the differences in nitrogen uptake efficiency between different cytoplasmic genes. The results showed a significant difference in the nitrogen uptake rate for different seedlings. With ammonium nutrition, the nitrogen uptake efficiency of the JW cytoplasm was significantly higher than that of the WA cytoplasm. In low concentrations of ammonium nitrogen, the JW cytoplasm had an additive effect to the nuclear gene regulation of ammonium uptake. The JW cytoplasm’s ammonium nitrogen absorption effect on nuclear gene regulation was higher than that of the WA cytoplasm. The effect of the WA and JW cytoplasms on the nitrate uptake rate was not significant, and the nuclear gene regulation of both cytoplasms was reduced by absorbing nitrate. Under nitrogen deficiency conditions, the material output and conversion rate of the JW-type cytoplasmic hybrid rice combination was relatively high, significantly higher than those of other cytoplasmic combinations. Under medium nitrogen conditions, the material output and conversion rate of the (N2) W-type hybrid rice combination were significantly higher than those of the other cytoplasmic combinations. The yield of JW-type rice first increased and then decreased with the increase in the nitrogen application rate and was highest, 8195.55 kg/hm², under the N2 treatment.