Table of Content

12 April 2018, Volume 44 Issue 04

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Characterization of Fusarium Head Blight Resistance Gene Fhb1 and Its Putative Ancestor in Chinese Wheat Germplasm

Zhan-Wang ZHU, Deng-An XU, Shun-He CHENG, Chun-Bao GAO, Xian-Chun XIA, Yuan-Feng HAO, Zhong-Hu HE

Acta Agronomica Sinica. 2018, 44(04):  473-482.  doi:10.3724/SP.J.1006.2018.00473

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Enhancing resistance to Fusarium head blight (FHB) has become one of important breeding objectives in the major wheat-growing regions in China. A prominent locus Fhb1 conferring stable FHB resistance with the largest effect is the major source of resistance in wheat breeding. Understanding the distribution and putative donor of Fhb1 in Chinese wheat cultivars will facilitate the application of this gene and thus benefit FHB resistance breeding in China. Haplotype analysis of PFT (pore-forming toxin-like), HC (HCBT-like defense response protein) and His (histidine-rich calcium-binding protein) genes in the Fhb1 region of 229 wheat cultivars and advanced lines indicated that PFT-I/His-I was a resistant haplotype. Both pedigree and marker (or sequence) information revealed that Fhb1 in Chinese wheat cultivars was mainly derived from Sumai 3 and Ningmai 9, in which Ningmai 9 was the major donor. The Fhb1 diagnostic markers PFT-CAPS and His-InDel developed in this study can be used effectively in marker-assisted selection for improving FHB resistance.

Enhanced Accumulation of BnA7HSP70 Molecular Chaperone Binding Protein Improves Tolerance to Drought Stress in Transgenic Brassica napus

Li-Li WAN, Zhuan-Rong WANG, Qiang XIN, Fa-Ming DONG, Deng-Feng HONG, Guang-Sheng YANG

Acta Agronomica Sinica. 2018, 44(04):  483-492.  doi:10.3724/SP.J.1006.2018.00483

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The molecular chaperone binding protein gene participates in the constitutive function of plant growth and protects plant cells against stresses. In this study, we found that BnA7HSP70 overexpressed transgenic lines did not wilt and showed only a small decrease in water potential. However, the wild type lines showed a large decrease in leaf water potential. The transgenic plants had higher relative water content, better osmotic adjustment and less lipid membrane peroxidation. In addition, the leaves from the elevated levels of BnA7HSP70 in transgenic lines conferred tolerance to the glycosylation inhibitor tunicamycin during germination. BnA7HSP70 overexpression-mediated attenuation of stress-induced cell death was confirmed by the decreased percentage of dead cell and the reduced induction of the senescence-associated marker gene BnCNX1. These phenotypes were accompanied by a delay in the induction of the cell death marker genes BnNRP, which are involved in transducing a cell death signal generated by ER stress and osmotic stress through the NRP (N-rich protein)-mediated signaling pathway. Enhanced expression of BnA7HSP70 delayed unfold protein response and NRP pathway mediated chlorosis and the appearance of senescence-associated markers BnLSC222 and BnLSC54 in Brassica napus. These results suggest that overexpression of BnA7HSP70 in Brassica napus alleviate ER stress and osmotic stress-integrating cell death response confronted with water stress.

Transcriptome Analysis on a Maize Photosynthetic Mutant hcf136 (high chlorophyll fluorescence 136)

Qing-Fei WU, Lei QIN, Lei DONG, Ze-Hong DING, Ping-Hua LI, Bai-Juan DU

Acta Agronomica Sinica. 2018, 44(04):  493-504.  doi:10.3724/SP.J.1006.2018.00493

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Maize (Zea mays) is a typical C₄ plant, which photosynthetic activities are partitioned by the cooperating of Kranz anatomy—mesophyll (M) cell and bundle sheath (BS) cell. The maize high chlorophyll fluorescence 136 (hcf136) mutant is an ideal material for C₄ photosynthesis study, due to it lacks PSII activity without normal thylakoid grana in M chloroplasts. However, the development of BS chloroplasts is not affected. In this study, we utilized RNA-Seq technology to monitor the transcriptome changes in different leaf sections between wild type and hcf136 mutant under different light intensities. The results indicated that the impairment of PSII is not caused by the transcription changes of PSII related genes. We also noticed that the starch biosynthesis was blocked in the mutant; and the sugar degradation, sugar transport and copper ion transport were triggered. In addition, the expression level of transcription factors was changed distinctly. These results provide valuable information for understanding a comprehensive function of HCF136 gene in future.

Improvement of Resistance of Wheat Cultivars to Fusarium Head Blight in the Yellow-Huai Rivers Valley Winter Wheat Zone with Functional Marker Selection of Fhb1 Gene

Hong-Jun ZHANG, Zhen-Qi SU, Gui-Hua BAI, Xu ZHANG, Hong-Xiang MA, Teng LI, Yun DENG, Chun-Yan MAI, Li-Qiang YU, Hong-Wei LIU, Li YANG, Hong-Jie LI, Yang ZHOU

Acta Agronomica Sinica. 2018, 44(04):  505-511.  doi:10.3724/SP.J.1006.2018.00505

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Fusarium head blight (FHB) becomes a major disease in the wheat production of the Yellow-Huai Rivers Valley Winter Wheat Zone of China. Improving FHB resistance is one of the major breeding targets in this region. The donors of Fhb1 gene, including Ningmai 9, Shengxuan 6, Jianyang 798, Jianyang 84, Sumai 3, and Ningmai 13, were moderately or highly resistant to FHB. Six backcrossing populations were developed by crossing these donors with a dwarfing and male-sterile wheat near isogenic line Zhoumai 16, and backcrossing with Zhoumai 16. The progenies were subjected to phenotypic evaluation of FHB by both the floret-inoculation method and natural infection in a field disease nursery. Fhb1 was detected by a functional Kompetitive Allele Specific PCR (KASP) marker. The backcrossing progenies with Fhb1 gene were moderately susceptible to FHB. Compared with the backcrossing progenies without Fhb1 gene, mean number of diseased spikelets and disease index reduced by 4.2 (P < 0.01) and 4.0 in the progenies with Fhb1 gene, respectively. The mean number of diseased spikelets and disease index for the backcrossing progenies with Fhb1 gene were 8.1 (P < 0.01) and 28.4 (P < 0.01) lower than those of the recurrent parent Zhoumai 16. There were significant differences in resistance among the backcrossing progenies from different donors. The progenies from Shengxuan 6 had better performance in number of diseased spikelets and disease index compared with those from any other donors. The results from this study indicate that Fhb1 gene can efficiently improve the FHB resistance of wheat cultivars grown in the Yellow-Huai Rivers Valley Winter Wheat Zone.

Effect of Silencing C-3 Oxidase Encoded Gene StCPD on Potato Drought Resistance by amiRNA Technology

Xiang-Yan ZHOU, Jiang-Wei YANG, Xun TANG, Yi-Kai WEN, Ning ZHANG, Huai-Jun SI

Acta Agronomica Sinica. 2018, 44(04):  512-521.  doi:10.3724/SP.J.1006.2018.00512

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The constitutive photomorphogenesis and dwarf (CPD) gene encodes C-3 oxidase as a key rate-limiting enzyme in the brassinosteroids (BRs) biosynthesis pathway, which plays a vital role in response to abiotic stress in plant. In this research, the potato CPD gene (StCPD) interference expression vector pCPB121-amiRcpd was constructed using the plant expression vector pRS-300 and amiRcpd skeleton precursor of Arabidopsis miR319a, and transferred into the potato genome mediated by Agrobactium tumefacienses L., so that transgenic plants (Ci1-Ci5) were obtained. The analysis of real time fluorescence quantitative polymerase chain reaction (qRT-PCR) showed that the interference degree of StCPD gene expression reached 78% and 90% in the transgenic lines Ci1 and Ci3 respectively. StCPD gene expressed in the roots, stems and leaves of the transgenic and non-transgenic (NT) plants, and expression level in the leaves was 3.05 and 1.65 fold higher than that in stems and roots. The malondialdehyde (MDA) content in transgenic plant leaves was significantly higher, whereas the proline content was significantly lower than those in NT under drought stress. The expression level of StCPD gene, MDA and proline contents in transgenic and NT plants under drought stress were significantly higher than those of control, and increased at different sampling times. These results indicated that StCPD gene interference expression could depress the effects of drought stress on potato. These results lay a foundation for further research on BRs regulation in potato development, which will help to reveal the molecular mechanisms of BRs regulation in potato.

QTL Analysis of Under-ear Internode Length Based on SSSL Population

Hai-Ping GUO, Gao-Yang SUN, Xiao-Xiang ZHANG, Peng-Shuai YAN, Kun LIU, Hui-Ling XIE, Ji-Hua TANG, Dong DING, Wei-Hua LI

Acta Agronomica Sinica. 2018, 44(04):  522-532.  doi:10.3724/SP.J.1006.2018.00522

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The under-ear internode length determines maize plant height and ear height, which are two agronomic traits associated with yield and lodging resistance. The lengths of the 7th, 8th, and 9th internode play a decisive role in ear height. Compared with other agronomic traits, there is little knowledge for genetic basis of under-ear internode length. Thus, exploring the genetic basis of internode length plays an important role in maize breeding. In this study, a set of 260 chromosome segment substitution lines (CSSLs), using Chang 7-2 as the donor parent and lx9801 as recipient parent, was constructed and used to map QTLs for the 7th, 8th, and 9th internode length and ear height at two-environments in two years. In total, 18, 23, and 17 QTLs were detected for the 7th, 8th, and 9th internode length, respectively. Among them, eight QTLs were simultaneously detected for the 7th, 8th, and 9th internode length. For ear height, 20 QTLs were detected, 12 (60%) of these 20 QTLs were found to co-localize to the 7th, 8th, and 9th internode length. The results indicated that length of the 7th, 8th, and 9th internode and ear height have same genetic basis. Furthermore, length of the 7th, 8th, and 9th internode are important components of ear height and also determining the plant height and ear height in maize.

Detection of QTLs for Plant Height Related Traits in Brassica napus L. Using DH and Immortalized F₂ Population

Ya-Jun HE, Dao-Ming WU, Ying FU, Wei QIAN

Acta Agronomica Sinica. 2018, 44(04):  533-541.  doi:10.3724/SP.J.1006.2018.00533

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Plant height is one of the important agronomic traits in rapeseed. In this study, QTLs for plant height and plant height related traits in Brassica napus were evaluated in two years environments by using a doubled haploid (DH) population lines derived from the cross between two rapeseed cultivars, Express and SWU07, and an immortalized F₂ population generated by randomly permuted intermating of these DH lines. A total of 41 putative QTLs were identified for plant height and plant height related traits and located on 13 linkage groups. Among them, nine QTLs were identified for plant height, located on A02, A09, C01, C02, and C06, respectively, with explained phenotypic variation ranging from 3.85% to 13.34%, 15 QTLs were identified for inflorescence length, located on A01, A02, A05, A08, A09, C01, C03, and C05, respectively, with explained phenotypic variation ranging from 3.82% to 9.52%, 11 QTLs were identified for the first branch height, located on A01, A03, A09, C01, and C03, respectively, with explained phenotypic variation ranging from 4.01% to 16.54%, four QTLs were identified for branch segment, located on A07, A09, C03, and C04, respectively, with explained phenotypic variation ranging from 4.79% to 8.10%, two QTLs were identified for average internode length, located on A07 and C05, respectively, with explained phenotypic variation ranging from 4.29% to 6.04%. Five of these QTLs were persistently expressed in different year environments or in different populations. These QTLs provide useful information for improving plant height in rapeseed breeding.

Genome-wide Association Analysis of Some Phytotoxicity Related Traits at Seedling Stage in Rapeseed under Glufosinate Stress

Dong-Liang CHEN, Cui CUI, Yi-Ying REN, Qian WANG, Jia-Na LI, Zhang-Lin TANG, Qing-Yuan ZHOU

Acta Agronomica Sinica. 2018, 44(04):  542-553.  doi:10.3724/SP.J.1006.2018.00542

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With planting rape in large area and weeds growing seriously in the field, glufosinate has been used in controlling field weeds tentatively. However glufosinate also produced phytotoxicity to the main cultivated rapeseed more or less, affecting the normal physiological and morphological activities, even yield. In this study, glufosinate of 200 mg L^-1 was used at stress concentration 506 representative Brassica napus varieties (lines) were genotyped using the Brassica 60k Illumina Infinium SNP array by genome-wide association studies of herbicide resistance coefficient of dry weight per unit leaf area (CLW), herbicide resistance coefficient of chlorophyll content (CCC) and comprehensive phytotoxicity coefficient (CPC). A total of 16 SNP sites related to the killing mechanism of glufosinate were detected. Six SNP sites associated with CLW were detected, with phenotypic contribution rate ranging from 6.53% to 10.04%, and 22 SNP sites associated with CCC, with the phenotypic from 4.97% to 6.20%, 98 SNP sites associated with CPC over A subgenome and C subgenome, with the rate range from 3.25% to 18.66%. After analysising the genes in the linkage disequilibrium (LD) interval of significant SNP, we found 18 glufosinate tolerance related candidate genes. Eleven candidate genes were found in the LD interval of SNPs related to CCC, among them nine were involved in acyltransferase activity, two were involved in acetyl-CoA transferase activity, seven candidate genes were found in the LD interval of SNPs related to CPC, one of them was associated with glutamine transferase activity, participating in glutamine metabolism, and other six genes were involved in acetyl CoA transferase activity. The physiological and biochemical process regulated by these genes related to the changes of leaf dry weight, chlorophyll content and the killing mechanism of glufosinate. Mining association sites and candidate genes provides a reference for the research of gene regulation mechanism in the physiological and morphological process under glufosinate stress.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effect of Alternate Wetting and Drying Irrigation on Post-anthesis Remobilization of Assimilates and Grain Filling of Rice

Yun-Ji XU, Yang-Dong XU, Yin-Yin LI, Xi-Yang QIAN, Zhi-Qin WANG, Jian-Chang YANG

Acta Agronomica Sinica. 2018, 44(04):  554-568.  doi:10.3724/SP.J.1006.2018.00554

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Alternate wetting and drying irrigation (AWD) has been widely adopted in rice production for saving water and increasing water use efficiency. However, there is limited information about how AWD affects post-anthesis remobilization of assimilates and grain filling. To elucidate this issue, we planted three rice cultivars, including Yangliangyou 6 (indica hybrid), Wuyunjing 24 (japonica) and Hanyou 8 (japonica) in the field. With treatments of conventional irrigation (CI), alternate wetting and moderate soil drying irrigation (WMD) and alternate wetting and severe soil drying irrigation (WSD) from 10 days after transplanting to maturity. Grain yield and its components, grain filling of superior and inferior spikelets, changes in activities of the key enzymes involved in the conversion from sucrose to starch in grains, photosynthetic traits of flag leaf, the remobilization of non-structural carbohydrates in stems (culms and sheaths) and changes in starch hydrolytic enzymes in stems were investigated and isotope ¹³C was applied to trace redistribution of stem reserves. WMD significantly increased number of spikelets per panicle, 1000-grain weight, percentage of filled grains and grain yield of all the tested cultivars as compared with CI. Increases in 1000-grain weight and percentage of filled grains under WMD were mainly due to the enhancement of grain filling in inferior spikelets. Both WMD and WSD significantly enhanced the activities of α-amylase and β-amylase in stems and promoted translocation and redistribution of stem reserves, and increased the contribution of reserved carbohydrates in stems to grain yield. Moreover, WMD strengthened photosynthetic efficiency of flag leaf and enhanced the activities of the key enzymes involved in the conversion from sucrose to starch in inferior spikelets, whereas WSD exhibited the opposite effects. The results suggest that better leaf performance and higher activities of starch hydrolytic enzymes in stems, more remobilization of assimilates from stems to grains, and stronger activities of the key enzymes involved in sugar metabolism in inferior spikelets under the WMD are important physiological reasons for the enhancement of grain-filling in inferior spikelets of rice.

Application of Random Forest Method in Maize-soybean Accurate Identification

Li-Min WANG, Jia LIU, Ling-Bo YANG, Fu-Gang YANG, Chang-Hong FU

Acta Agronomica Sinica. 2018, 44(04):  569-580.  doi:10.3724/SP.J.1006.2018.00569

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It is very important to obtain the crop identification information based on remote sensing image. Remote sensing images have the advantages of high efficiency, high accuracy, low costs, and wide monitoring scope. Applying remote sensing images in maize-soybean accurate identification and planting area evaluation can give full play to the advantages of remote sensing images. Random forest classification (RFC) is a new classification method, a type of machine learning. Currently, there are very few studies on crop classification based on RFC. In order to evaluate the potential of the method on maize-soybean crop accurate identification, the paper conducted classification of major crops of soybean, maize, and other ground objects. Utilizing Landsat-8 OLI satellite image data, and three methods including maximum likelihood classification (MLC), support vector machine (SVM), and random forest classification (RFC). The overall classification accuracies of MLC, SVM, and RFC were 91.68%, 91.49%, and 94.32%, with their kappa coefficients of 0.87, 0.87, and 0.91, respectively, showing that RFC is better. The principal component analysis (PCA) was made on original seven wave band images, and the first four wave bands of the major components were extracted. Meanwhile, the normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were calculated; six additional supporting characteristic wave bands were overlapped on original seven wave band images, and the classifications with MLC, SVM, and RFC were conducted again. After adding characteristic wave bands, crop identification accuracies by MLC and SVM methods were not improved. The accuracy of RFC method was increased slightly with overall accuracy of 95.81% increasing by 1.49 percent, and Kappa coefficient of 0.94 increasing by 0.03, showing accuracy slightly increased, and limited improvement effect. Near-infrared band and two short infrared wave bands were most important, while newly added wave band was not significant for soybean-maize identification, showing the limited improvement effect of supporting wave band. SVM had the longest time spent on classification, with about 11 000 s; MLC the least, only 145 s; and RFC about 1800 s. It indicates that SVM doesn’t have any advantages in both accuracy and time-consumed, however, MLC can quickly get the classification results, and RFC has the highest classification accuracy with moderate time consumed. In conclusion, RFC has greater advantage in soybean-maize accurate identification, and is suitable to be widely applied in the operation of regional agriculture remote sensing monitoring crop area extraction.

Physiological Mechanisms of Promoting Source, Sink, and Grain Filling by 24-Epibrassinolide (EBR) Applied at Panicle Initiation Stage of Rice

Zan-Tang LI, Shi-Yin WANG, Wen-Yu JIANG, Shuai ZHANG, Shao-Bin ZHANG, Jiang XU

Acta Agronomica Sinica. 2018, 44(04):  581-590.  doi:10.3724/SP.J.1006.2018.00581

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Grain weight and yield of rice are clearly related to grain filling ability, which is strongly affected by source and sink. Studies of Brassinosteroids’ effects on growth, development and yield of rice have been reported. In order to further set forth the relative physiological characteristics and relationship, we set up field experiments to study the impacts of 24-epibrassinolid (EBR) sprayed at the panicle initiation stage of Nipponbare on source capacity, sink size, sink activity and grain filling. Both T1 (0.2 µmol L^-1 EBR) and T2 (1 µmol L^-1 EBR) treatments increased the source capacity by improving the accumulation of photosynthate and its translocation during grain filling stage. Both EBR treatments increased the sink size through different manners: T1 treatment increased the grain weight markedly but had little influence on panicle and grain amounts; and T2 treatment significantly increased number of panicles and grains per panicle whereas had little influence on grain weight. Two EBR treatments enhanced the sucrose lyase activity in both superior and inferior grains, especially for the activity of Acid Invertase (AI) in inferior grains. AI accelerated the transportation of photosynthate and the synthesis of starch in inferior grains. T1 and T2 significantly increased rice yield by an average of 5.6% and 15.2%, respectively, with 9.1% more in T2 than in T1. Therefore, compared with grain weight enhancement in T1, the increase of panicle and grain numbers in T2 had greater impact on rice yield. In summary, two EBR treatments at panicle differentiation stage can increase the source capacity, sink size and sink activity of rice, and then promote photosynthates accumulation and distribution, which is beneficial to grain filling. On the basis of sufficient photosynthates and strong sink activity, sink size enlargement can significantly increase the rice yield.

Effects of High Temperature and Water Deficiency during Grain Filling on Activities of Key Starch Synthesis Enzymes and Starch Accumulation in Wheat

Yang-Yang HU, Hong-Fang LU, Wei-Xing LIU, Juan KANG, Geng MA, Sha-Sha LI, Ying-Ying CHU, Chen-Yang WANG

Acta Agronomica Sinica. 2018, 44(04):  591-600.  doi:10.3724/SP.J.1006.2018.00591

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High temperature and drought, the major abiotic stresses during grain filling of winter wheat, have great influence on photosynthate accumulation in grains. In this study, we evaluated the effects of high temperature, drought and the compound stress at grain-filling stage on the activities of key starch synthesis enzymes and the contents of starch and its components in grains of winter wheat cultivar ‘Zhengmai 366’. The pot-grown plants were moved from field to the climate chamber at 10 days after anthesis and exposed to the stresses until maturity. The climate chamber was desired with the normal growth condition (25°C/15°C, day/night) and high temperature (HT) stress (32°C/22°C, day/night) treatments. Under each temperature treatment, the soil moisture was adjusted to ~75% (normal) and ~50% (drought stress, DS), respectively. The normal temperature and soil moisture condition was taken as the control. Compared with the control, HT, DS, and HT+DS significantly increased activities of soluble starch synthase (SSS) and granule bound starch synthase (GBSS) at early period of stress and rapidly declined them subsequently. However, all stress treatments reduced the activities of starch branching enzymes (SBE), ADPG pyrophosphorylase (AGPase) and sucrose synthase (SS) during the whole grain-filling stage. The interaction between HT and DS was significant on all enzyme activities. Under HT, DS and HT+DS conditions, starch accumulation rate of grain, and the contents of amylose, amylopectin and total starch decreased and growth duration shortened, leading to reduced grain weight and yield at maturity. HT showed greater influence than DS, and the effect of compound stress was larger than that of each individual stress. Correlation analysis revealed that the activities of SSS and GBSS were positively correlated with the contents of amylose, amylopectin and total starch at most stages (P < 0.01), whereas, those of SBE, AGPase and SS at late grain-filling stage (22-26 days after anthesis) (P < 0.01). These results indicate that high temperature and drought stresses cause yield loss and degrade grain quality by affecting activities of key starch synthesis enzymes and starch accumulation in wheat grains.

Effects of Climatic Factors in the Southeast of Sichuan Basin on Grain Yield of Mid-season Hybrid Rice

Fu-Xian XU, Xing-Bing ZHOU, Lin ZHANG, Peng JIANG, Mao LIU, Yong-Chuan ZHU, Xiao-Yi GUO, Hong XIONG

Acta Agronomica Sinica. 2018, 44(04):  601-613.  doi:10.3724/SP.J.1006.2018.00601

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The aim of this study was to clarify the key climatic factors influencing rice yield, and propose the technical measures for rice yield increase in southeast Sichuan Basin. A field experiment with two hybrid rice cultivars, II you 602 and Jingyou 127, was conducted to study the effect of climatic factors on yield increasing in water-logged paddy field of this area in 2015 and 2016. In each year, the two cultivars were grown in two combinations (high nitrogen rate with low plant density, HNLD; low nitrogen rate with high plant density, LNHD), respectively, on five sowing dates. As the sowing date delayed, the mean whole growth duration of hybrid rice was shortened by 14.77%, from 148.13 d to 123.25 d. Vegetative period of hybrid rice, rather than the reproductive period, was mainly affected by climatic factors. Grain yield of hybrid rice was not significantly affected (differentiated) by year, cultural method and cultivar. Grain yield of hybrid rice dropped from 8507.76 kg ha^-1 on March 5 to 6251.01 kg ha^-1 on May 24. The average grain yield of hybrid rice across five sowing dates was reduced by 26.53%. Growth duration from sowing (SO) to transplanting (TR), TR to jointing stage (JS), number of days in vegetative period and whole growth duration, respectively, had a significantly positive correlation with spikelets per panicle and grain yield. The effects of climatic factors on grain yield of hybrid rice varied with years and cultivars. For good quality rice Jingyou 127, percentage of filled grain, thousand-grain weight and grain yield, respectively, were significantly and positively correlated with average diurnal temperature from full heading (HD) to maturity (MA), while significantly and negatively correlated with sunshine hours from JS to HD in 2015; spikelets per panicle and grain yield, respectively, had a significantly negative correlation with average maximum temperature from SO to TR and average diurnal temperature from TR to JS in 2016. For high-yielding cultivar II you 602, panicles per m², thousand-grain weight and grain yield, respectively, were significantly or extremely significantly and negatively correlated with precipitation from TR to JS in 2015; spikelets per panicle and grain yield, respectively, were significantly or extremely significantly and negatively correlated with daily maximum temperature from TR to JS, while percentage of filled grain, thousand-grain weight and grain yield, respectively, were significantly and positively correlated with average relative humidity from JS to HD in 2016. In conclusion, the optimum sowing dates in southeast Sichuan Basin are from March 5 to March 25 for single mid-season hybrid rice. Meanwhile, sowing as early as possible during the optimum sowing period will be more beneficial to the improvement of guarantee rate for safe full heading of ratoon rice in main crop-ratooning rice system.

RESEARCH NOTES

Exploration of Foreign Maize Inbred Lines with Broad Spectrum Resistance to Northern Corn Leaf Blight and Preliminary Identification of Resistance Genes

Ming-Gang XIAO, Feng-Jing SONG, Bing SUN, Xin ZUO, Guang-Shan ZHAO, Ai-Hua XIN, Zhu-Gang LI

Acta Agronomica Sinica. 2018, 44(04):  614-619.  doi:10.3724/SP.J.1006.2018.00614

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From 2014 to 2016, forty-three maize inbred lines introduced from the United States, France, Russia and Germany, were identified and evaluated for resistance to northern corn leaf blight (NCLB). The results showed that seven, one and six maize inbreds were highly resistant, resistant or moderately resistant to NCLB, accounting for 32.6%. Exserohilum turcicum was used to test the F₂ populations for analyzing the inheritance of NCLB resistance in the seven highly resistance maize inbred lines. Genetic analysis suggested that A04, F02, F05, and R01 of these inbred lines probably carried a single dominant gene conferring their resistance to NCLB. The reaction patterns to isolates 0, 1, 2, N, and 123N of E. turcicum showed that new genes resistance to NCLB were most likely present in A04, F02, F05, and R01. The results provided useful information on the introduction of maize germplasms and genetic improvement for resistance to NCLB.

Cloning and Regulation Function Analysis of TaSC Promoter from Salt Tolerant Wheat

Bo JIAO, Feng BAI, Yan-Yan LI, Jia LU, Xiao ZHANG, Yi-Ru CAO, Rong-Chao GE, Bao-Cun ZHAO

Acta Agronomica Sinica. 2018, 44(04):  620-626.  doi:10.3724/SP.J.1006.2018.00620

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High salinity is one of the major abiotic stress factors in wheat. Exploring stress related genes from salt-tolerant wheat varieties and analyzing their regulatory mechanism are helpful for elucidating the salt tolerance mechanism in wheat. In this study, the promoter sequence of a salt-tolerant related gene TaSC, designated ProTaSC, was cloned from salt-tolerant wheat mutant RH8706-49 by TAIL-PCR and silicon cloning method. A series of cis-acting elements including abscisic acid response element (ABRE), MYB protein binding site (MBS), TATA-box and CAAT-box were predicted in the promoter region. Among them ABRE and MBS are involved in abiotic stress responses. Beta-glucuronidase gene was used as reporter to study the expression characteristic of ProTaSC, showing that the full-length fragment and two 5'-progressive deletion fragments (681 bp and 1096 bp) were able to trigger GUS expression. However, GUS expression was undetectable when the fragment was less than 343 bp. These results suggest that the full-length promoter has promoting activity and the sequence between -681 to -343 nucleotides is the basic core region of ProTaSC. ProTaSC is a tissue-specific promoter because GUS gene driven by full-length ProTaSC was expressed in root, leaf, anther, sepals, and mature pods, but not in stem, petal, young fruit, and seed of Arabidopsis harboring ProTaSC:GUS. Quantification of GUS activity assay showed that ProTaSC was induced significantly by NaCl (200 mmol L^-1) and ABA (10 μmol L^-1) in the transgenic Arabidopsis seedlings, indicating ProTaSC is a functional sequence induced by NaCl or ABA treatment.