Archive

10 November 2023, Volume 37 Issue 6 Previous Issue    Next Issue
---
Review and Special Topic
Research Papers


For Selected:

Download Citations EndNote Ris BibTeX

Toggle Thumbnails

Review and Special Topic

Select

Research Progress on Correlation of Rice Leaf Senescence and Discoloration with Nitrogen Reuse and Volatilization TAO Yi, XU Yanan, YE Chang, ZHENG Guangjie, XU Chunmei, CHEN Song, CHU Guang, LIU Yuanhui, WANG Danying 2023, 37(6): 553-562.  DOI: 10.16819/j.1001-7216.2023.230605 Abstract ( )   HTML ( )   PDF (1050KB) ( )   Leaf senescence is a critical development stage in the plant lifecycle, and leaf discoloration is a typical marker. The investigation on N recycle and reuse during the leaf color changing process can provide insights into the influence factors of N remobilization efficiency. This review delivers a brief overview about the internal and external factors that influence rice leaf discoloration and the types of stay-green varieties. Moreover, we summarized the latest research progress on the association between nitrogen reutilization-volatilization and rice leaf discoloration. This review elucidated the reasons behind the increasing nitrogen volatilization during the late reproductive stage of rice, and made a strong case for the development of straightforward leaf discoloration monitoring technology to create a quantitative indicator system for leaf discoloration characteristics. Such a review would clarify the relationships and mechanisms between rice leaf senescence dynamics and nitrogen reutilization and volatilization, photosynthetic assimilate accumulation, and nitrogen activation reutilization in the maturation process.

Research Papers

Select

Identification and Functional Characterization of the Heat Shock Protein (HSP) 40 Encoding Gene, MoMHF6, in Magnaporthe oryzae TONG Qi, WANG Chunyan, QUE Yawei, XIAO Yu, WANG Zhengyi 2023, 37(6): 563-576.  DOI: 10.16819/j.1001-7216.2023.230301 Abstract ( )   HTML ( )   PDF (2497KB) ( )   【Objective】 To explore the roles of chaperone HSP40 (heat shock protein 40) in morphological differentiation and pathogenesis in Magnaporthe oryzae. 【Method】 The HSP40 encoding gene MoMHF6 of M. oryzae was knocked out by DNA homologous recombination, and a deletion mutant ΔMomhf6 was generated. Biological function of the gene was systematically characterized via phenotypic analysis, gene complementation and RNA-seq analysis. 【Result】 Phenotypic analysis of the mutant revealed severe impairments in aerial hypha growth, asexual sporulation, conidial germination, perithecium production and appressorium formation. However, compared to the wild-type strain, the deletion of MoMHF6 did not affect mycelium radial growth on CM medium and the development of asci and ascospores in perithecia. Incipient cytorrhysis assays revealed that the appressorium collapse rate of the ΔMomhf6 mutant under treatment with 1, 2 or 3 mol/L glycerol was significantly increased compared to the wild-type strain, indicating that MoMHF6 is required for appressorium turgor generation. Also, we found that the ΔMomhf6 mutant was unable to penetrate into onion epidermis and completely nonpathogenic to susceptible hosts. Even in wounded barley leaves, infectious growth of the mutant was severely impaired. Moreover, the deletion of MoMHF6 resulted in significantly increased sensitivity to oxidative stress and delayed glycogen transportation and degradation during appressorium development, indicating that MoMHF6 is involved in oxidative stress response and glycogen metabolism of appressorium. All phenotypic defects of the ΔMomhf6 mutant could be restored by reintroducing the full-length MoMHF6 gene into the mutant. In addition, RNA-seq analysis of the ΔMomhf6 mutant revealed that several known pathogenicity-related genes in differentially expressed genes (DEGs) might be regulated by MoMHF6, such as MoATG4, MoPL1, MoVPR, and GAS1. 【Conclusion】 The HSP40 gene MoMHF6 plays an important role in asexual sporulation, appressorium formation, host penetration, oxidative stress response and pathogenicity in M. oryzae. These results are of great significance for further understanding the gene networks and molecular mechanisms in regulating morphological differentiation and pathogenesis governed by MoMHF6 in M. oryzae.

Select

cDNA Cloning and Molecular Characterization of OsTAF12b Gene in Oryza sativa QI Panpan, GUO Liuming, LI Jing, LÜ Mingfang, YUAN Zhengjie, ZHANG Hengmu 2023, 37(6): 577-586.  DOI: 10.16819/j.1001-7216.2023.230108 Abstract ( )   HTML ( )   PDF (2246KB) ( )   【Objective】 In order to determine the alternative splicing forms of TATA-box binding protein (TBP) associated factor 12b (OsTAF12b), a component of the general transcription factor ⅡD (TFⅡD), in rice (Oryza sativa), characterize their subcellular localization and expression patterns, and provide basal information for further functional studies. 【Method】 The full-length cDNA of OsTAF12b was amplified and cloned by rapid amplification of cDNA 5’-/3’-ends (RACE). Multiple sequence alignment and a phylogenetic tree were conducted by bioinformatic analysis. The subcellular localization of OsTAF12b was observed with a laser confocal microscopy and its expression patterns under abiotic stresses were analyzed by qRT-PCR. 【Results】 Four alternative splicing forms of OsTAF12b were identified and there was only one lysine difference within their coding regions. OsTAF12b was highly homologous to those of other gramineous plants and they were grouped together in a clade in the phylogenetic tree. The GFP-fused OsTAF12b protein was colocalized with H2B, a marker labeling nuclear localization, in both cells of N. benthamiana leaves and rice protoplasts. Its transcript level was higher in leaves and significantly up-regulated when exposed to different abiotic stresses. 【Conclusion】 The OsTAF12b gene has four alternative splicing forms of transcripts and encodes two nuclear proteins with only a single lysine residue difference. Its expression patterns suggest that OsTAF12 could be involved in response to a variety of abiotic stresses.

Select

Development and Agronomic Traits Analysis of New Rice Resistance Lines to Xanthomonas oryzae pv. oryzicola FENG Aiqing, WANG Congying, SU Jing, FENG Jinqi, CHEN Kailing, LIN Xiaopeng, CHEN Bing, LIANG Meiling, YANG Jianyuan, ZHU Xiaoyuan, CHEN Shen 2023, 37(6): 587-596.  DOI: 10.16819/j.1001-7216.2023.230406 Abstract ( )   HTML ( )   PDF (1630KB) ( )   【Objective】 This study aims to develop new rice resistance lines to bacterial leaf streak (BLS) and provide core germplasm materials for BLS resistance breeding. 【Method】 BHADOIA303 harboring the Xo2 gene from Bangladesh was used as the BLS resistance donor, and an elite indica variety Wushansimiao was chosen as the recipient, to develop resistant lines by advanced backcrossing, molecular marker-assisted selection and GSR40K chip detection. The BLS resistance lines was evaluated by artificial inoculation with pathogen inoculum spraying and syringe infiltration in the field, and their agronomic traits were evaluated synchronously. 【Result】 Molecular markers and GSR40K microarray detection confirmed the presence of the target gene Xo2 in 10 new lines (BC4F5). Significant differences were observed in the BLS resistance between the introgression lines and Wushansimiao, no matter whether they were inoculated by spraying or infiltration. The average disease index ranged from 5.00 to 10.37, with an average lesion length of 0.70 to 0.99 cm. Lines 1-3 showed the best resistance. The agronomic and yield traits of the 3 lines with better resistance were comparable to those of Wushansimiao. The 1000-grain weight, grain length and width of line 1 were similar to those of Wushansimiao, and its seed setting rate was better than that of Wushansimiao. Number of total grains per panicle of Line 2 was similar to that of Wushansimiao with longer and wider grains, and a higher 1000-grain weight. The 1000-grain weight and seed setting rate of Line 3 were similar to those of Wushansimiao, and the number of panicles per plant was better than that of Wushansimiao. 【Conclusion】 Three Xo2 resistance lines with better agronomic traits and greatly enhanced resistance to BLS were obtained, which would provide resistance elite germplasm materials and accelerate the process of BLS resistance molecular breeding.

Select

Mapping Major QTLs for Panicle Traits Using CSSLs of Dongxiang Wild Rice (Oryza rufipogon Griff.) HU Jiaxiao, LIU Jin, CUI Di, LE Si, ZHOU Huiying, HAN Bing, MENG Bingxin, YU Liqin, HAN Longzhi, MA Xiaoding, LI Maomao 2023, 37(6): 597-608.  DOI: 10.16819/j.1001-7216.2023.221205 Abstract ( )   HTML ( )   PDF (1507KB) ( )   【Objective】 Panicles are the primary yield determinants in rice, making it essential to explore major QTL associated with panicle traits for subsequent fine mapping, cloning, and breeding purposes. 【Method】 We employed a population of Chromosome Segment Substitution Lines(CSSLs) generated by crossing Nipponbare (japonica) with C35 (Dongxiang wild rice) and conducted phenotypic evaluations and major QTL mapping across four distinct ecological environments. 【Result】 Significant variations in panicle traits were observed in the CSSL populations across different ecological environments. The introduction of Dongxiang wild rice chromosome segments brought about substantial changes in panicle traits, leading to a noticeable increase in production. A total of 64 QTLs controlling grain number per panicle and grain size were identified across early-season, mid-season, late-season in Jiangxi, and Hainan environments. Among these QTLs, qPL2, qSN1.2, qSN2, qFGN3, qTGW2, qTGW12.1, and qSL2 consistently expressed in three environments, and 21 QTLs were detected in two environments, while others were specific to a single environment. Major QTLs, including qSN1.1, qSN1.2, qSN2, qSN3, and qSN12, exhibited significant effects on grain number per panicle, suggesting that multiple QTL aggregations play a crucial role in regulating grain number. Major QTLs such as qSL2, qSL3.2, qSLW3.1, qSLW3.2, qTGW8.1, and qSLW10 had evident effects on grain size, influencing grain length, grain width, and the length-to-width ratio. Interactions between these loci jointly determined grain size. Additionally, we observed clusters of panicle trait QTLs on 10 chromosome segments. These major QTL clusters, qGNS1.1, qGNS1.3, qGNS2.1, qGNS3.1, qGNS9, qGNS10, and qGNS12, contained several QTLs that regulated grain number and grain size traits. These clusters exhibited stable expression across diverse environments, underscoring the regulatory role of alleles from Dongxiang wild rice in enhancing yield. 【Conclusion】 These findings not only serve as the foundation for uncovering valuable genes in Dongxiang wild rice but also provide new genetic resources for the rice molecular breeding.

Select

Identification and QTL Mapping of Rice Germplasm Resources with Low Amylose Content XIE Kaizhen, ZHANG Jianming, CHENG Can, ZHOU Jihua, NIU Fuan, SUN Bin, ZHANG Anpeng, WEN Weijun, DAI Yuting, HU Qiyan, QIU Yue, CAO Liming, CHU Huangwei 2023, 37(6): 609-616.  DOI: 10.16819/j.1001-7216.2023.221109 Abstract ( )   HTML ( )   PDF (777KB) ( )   【Objective】 Amylose content (AC) is one of the most critical factors that determine the eating and cooking quality (ECQ) of rice. Therefore, it holds great significance to screen rice germplasm resources with low amylose content and elucidate the genetic control mechanism for breeding new varieties with excellent ECQ. 【Method】 We determined AC in 22 restorer lines of three-line hybrid rice and analyzed the QTL locus controlling amylose content using a double haploid (DH) population derived from the cross between Fan 38 and Shenhui 26. 【Result】 Two rice germplasms with low AC, Fan 32 and Fan 38, were discovered among the 22 restorer lines. Their AC was found to be 11.39%±0.01% and 10.58%±0.13%, respectively. In contrast to other low AC varieties carrying Wxmp alleles, Fan 32 and Fan 38 carried Wxb alleles. A total of five QTLs, namely qAC1.1, qAC1.2, qAC5, qAC6.1, and qAC6.2, related to amylose content, were identified in the DH population. Among these, qAC6.1 and qAC6.2 were consistently detectable over two years. qAC6.2 emerged as a major QTL, contributing to over 30% of the phenotypic variation. 【Conclusion】 These findings suggest that the low AC in Fan 38 is likely primarily controlled by the qAC6.2 locus. This establishes a foundation for further research into the regulatory mechanism of amylose synthesis in rice and for the development of new rice varieties with low AC using marker-assisted selection technology.

Select

Morphological and Physiological Characteristics of Rice Roots Under Combined Salinity-Drought Stress and Their Relationships with Yield Formation ZHU Wang, ZHANG Xiang, GENG Xiaoyu, ZHANG Zhe, CHEN Yinglong, WEI Huanhe, DAI Qigen, XU Ke, ZHU Guanglong, ZHOU Guisheng, MENG Tianyao 2023, 37(6): 617-627.  DOI: 10.16819/j.1001-7216.2023.230504 Abstract ( )   HTML ( )   PDF (395KB) ( )   【Objective】 This study aims to elucidate the mechanisms by which combined salinity-drought stress affects rice root morphology, physiology, and yield formation. 【Method】 We used Nanjing 9108, a conventional japonica rice variety widely grown in the mudflats along the coast of Jiangsu Province, as the test material. The following treatments were applied: control (no stress, CK), single salinity stress (0.15s, salinity concentration 0.15%; 0.3s, salinity concentration 0.3%), single drought stress (DJ, drought at jointing stage; DH, drought at heading stage), and combined salinity-drought stress (0.15s+DJ, 0.15s+DH, 0.3s+DJ, 0.3s+DH). We conducted a comparative study to investigate changes in root morphology and physiology of rice under combined salinity-drought stress and their underlying relationships with crop production and yield formation. 【Results】 In comparison to the control, rice yield decreased by 25.8% and 65.0% under single salinity stress (0.15s and 0.3s, respectively). Under single drought stress (DJ and DH), the yield reduction was 4.3% and 22.3%, respectively. Under combined salinity-drought stress (0.15s+DJ, 0.3s+DJ, 0.15s+DH, and 0.3s+DH), the yield reduction was 33.3%, 67.3%, 48.3%, and 72.6%, respectively. The number of panicles, grain number per panicle, seed setting rate, and thousand grain weight were significantly lower under single salinity stress and combined salinity-drought stress treatments compared to the control. The yield components of rice under combined salinity-drought stress were also significantly lower than those under single salinity stress and drought stress. Aboveground dry matter weight and harvest index of rice during maturity were lower under single salinity stress, drought stress, and combined salinity-drought stress compared to the control. The aboveground and root dry matter weight, root to shoot ratio, and harvest index of plants under combined salinity-drought stress were lower than those under single salinity stress and drought stress. Root length, root surface area, root diameter, root oxidation activity, and bleeding intensity were significantly inhibited under single salinity stress and combined salinity-drought stress, with a stronger inhibitory effect under combined salinity-drought stress. Net photosynthetic rate and chlorophyll contents of rice leaves were reduced under single salinity stress, drought stress, and combined salinity-drought stress, with the greatest decrease observed under combined salinity-drought stress. 【Conclusion】Combined salinity-drought stress significantly inhibits rice root morphology and physiology, consequently impacting leaf photosynthesis, assimilate accumulation, and yield formation. This inhibitory effect is more pronounced than that of single salinity stress and drought stress, with a synergistic impact.

Select

Improvement of Yield and Quality of Rice by Combining Returning of Green Manure (Astragalus smicus L.) and Rice Straw with Reduced Application of Nitrogen Fertilizer in Southern Shaanxi Province WU Yuhong, LI Yanhua, WANG Lü, QIN Yuhang, LI Shanshan, HAO Xingshun, ZHANG Qinglu, CUI Yuezhen, XIAO Fei 2023, 37(6): 628-641.  DOI: 10.16819/j.1001-7216.2023.230403 Abstract ( )   HTML ( )   PDF (904KB) ( )   【Objective】This study aims to investigate the effects of incorporating green manure and rice straw, along with reduced nitrogen (N) fertilizer application, on rice population quality, grain yields, N absorption, and grain quality in a Chinese milk vetch (Astragalus sinicus L.)-rice (Oryza sativa L.) rotation system. The goal is to lay a theoretical foundation for reducing N input, enhancing efficiency, and improving grain quality in rice cultivation. 【Method】 A field experiment was conducted in Hanzhong City, Shaanxi Province, from 2019 to 2021, utilizing a randomized block design with four treatments: 1) Chinese milk vetch application with no straw returning and conventional nitrogen application (GN100); 2) Incorporating winter-planted milk vetch and rice straw into the field with conventional nitrogen application (GSN100); 3) Incorporating winter-planted milk vetch and rice straw into the field with a 20% reduction in nitrogen fertilizer (GSN80); 4) Incorporating winter-planted milk vetch and rice straw into the field with a 30% reduction in nitrogen fertilizer (GSN70). During the full heading and maturity stages, aboveground biomass and grain yield were measured, and N content and accumulation in aboveground biomass were analyzed. Additionally, the appearance quality, protein and amylose contents, and gel consistency were assessed. In 2021, an experiment was conducted to examine the nitrogen release characteristics of Chinese milk vetch (CMV) or the combined use of CMV and rice straw, with samples collected on various days to determine the total N content of decomposition residues. 【Results】 The field experiment results demonstrated that the incorporation of CMV and rice straw significantly promoted aboveground rice growth from the full heading stage to maturity, with a notable increase in the population growth rate of 39.83% compared to GN100. Over two years, the average annual yield of "Huanghuazhan" increased by 3.08%, 7.21%, and 3.92% under the GSN100, GSN80, and GSN70 treatments, respectively, when compared to GN100. Incorporating CMV and rice straw enhanced the dry matter of panicle during the full heading stage and maturity, facilitating dry matter transportation to the panicle after the full heading stage. Compared to GN100, the contribution rate of dry matter to the panicle after the full heading stage was 1.93%, 23.59%, and 14.43% under GSN100, GSN80, and GSN70 treatments, respectively. The incorporation of CMV and rice straw increased N accumulation in rice stems and panicles at the maturity stage, with GSN80 showing the highest improvement. In comparison to GN100, the average anaual N accumulation in rice stems and panicles at the maturity stage increased by 40.74% and 23.20%, respectively. Rice quality improved significantly with the increasing years of CMV and rice straw incorporation. When compared to GN100, the incorporation of CMV and rice straw reduced amylose and protein contents in rice while enhancing gel consistency. This resulted in a decrease in amylose content by 7.54% to 17.10% and protein content by 4.28% to 5.88%, along with an increase in gel consistency by 2.64% to 12.51%. Moreover, GSN80 and GSN70 had the most substantial positive effects, significantly reducing chalky grain percentage and chalkiness degree of rice. The nylon net bag decomposition experiment revealed that the incorporation of CMV and rice straw increased the nitrogen supply level in the later stages of rice growth, with a significant increase of 11.97% in cumulative nitrogen release during the 106 to 146 days of decomposition compared to CMV being returned to the field alone. 【Conclusions】 In a rotation system of CMV and rice, incorporating CMV and rice straw into the field improves soil N supply during the late stages of rice growth, promoting dry matter accumulation, N absorption, and N transport after the full heading stages. This leads to a reduction in protein and amylose content and an increase in gel consistency, appearance quality, processing quality, and taste quality of rice. However, a 20%-30% reduction in N fertilizer is more conducive to establishing a high-yield population and achieving the synergistic improvement of yield and rice quality. Therefore, the incorporation of CMV and rice straw into the field with a 20%-30% reduction in N fertilizer may be an environmentally friendly cultivation technique suitable for the synergistic enhancement of yield, reduced fertilizer use, and improved quality of indica rice.

Select

Response of Middle-season Hybrid Rice to Flooding Stress at the Booting Stage ZOU Yuao, WU Qixia, ZHOU Qianshun, ZHU Jianqiang, YAN Jun 2023, 37(6): 642-656.  DOI: 10.16819/j.1001-7216.2023.230304 Abstract ( )   HTML ( )   PDF (898KB) ( )   【Objective】 This study aims to investigate the response of rice and identify key indicators to flooding stress during the booting stage, with the goal of mitigating yield losses caused by such stress. 【Method】 Experiments involving different flooding durations (3 days, 6 days, and 9 days) and depths (1/4 flooding, 25% of the rice plant height before the experiment, 1/2 flooding, 3/4 flooding, and full flooding) were conducted during the booting stage of middle-season rice (Fengliangyouxiang 1) in 2017 and 2018. 【Results】 Following flooding stress during the booting stage, there was a significant increase in rice plant height, primarily attributed to a significant increase in the 4th internode, while the dry weight of individual panicle decreased notably. Chlorophyll a (Chl a) content, chlorophyll b (Chl b) content, soluble protein content, net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of rice leaves decreased with increasing flooding duration and depth. The concentration of inter-cellular CO2 (Ci) declined with greater flooding depth, yet exhibited a rebound under fully flooding conditions. Malondialdehyde (MDA) content and peroxidase (POD) activity in rice leaves increased with deeper flooding. The content of soluble sugars in leaves increased, then decreased, with greater flooding depth. At 3 days of flooding, superoxide dismutase (SOD) activity in rice leaves, root MDA content, and SOD activity increased with deeper flooding. With prolonged flooding, SOD activity in rice leaves, root MDA content, and SOD activity initially increased, then decreased, with increasing flooding depth. Root POD activity increased with increasing flooding depth at 3 days and 6 days, and increased, then decreased, at 9 days. The effective panicle number, filled grain number per panicle, seed setting rate, thousand grain weight, and actual rice yield all decreased with greater flooding depth. When the duration of flooding exceeded 6 days or the depth of flooding exceeded half the plant height, rice yield reduction exceeded 25%. Actual rice yield exhibited a highly significant binary correlation with both days of flooding and depth of flooding, with depth having a greater impact than duration. 【Conclusion】 Chlorophyll b (Chl b), chlorophyll a (Chl a), soluble protein, Pn, Gs, and Tr display the strongest correlation with actual rice yield, with gray correlation coefficients all exceeding 0.6. These can serve as indicators for evaluating flooding severity and predicting yield reduction during booting.