Table of Content

12 March 2018, Volume 44 Issue 03

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Accurate Identification of Varieties by Nucleotide Polymorphisms and Establishment of Scannable Variety IDs for Soybean Germplasm

Zhong-Yan WEI, Hui-Hui LI, Jun LI, A. Gamar Yasir, Yan-Song MA, Li-Juan QIU

Acta Agronomica Sinica. 2018, 44(03):  315-323.  doi:10.3724/SP.J.1006.2018.000315

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In order to strengthen the management of soybean germplasm and variety protection, SNP markers were developed to establish the identity of soybean varieties. A set of 23 SNP markers distributed in 13 genes were used to discriminate genotypes of 599 soybean varieties, grown in most of the soybean producing areas in China. Fourteen SNPs with high polymorphism selected from the 23 SNPs (GlySNP14) showed the improved variety identification capability, compared with any combination of 14 random SNPs. A simulated experiment confirmed that GlySNP14 could effectively distinguish of 750 soybean varieties, while the combination of random by selected from the 14 SNPs could distinguish only 361 varieties. The established ID of soybean varieties in this study contained a 38-digit serial code, which can be used for the accurate identification of soybean varieties and meet the requirements of genetic resources protection.

Development and Application of the Functional Marker for Imidazolinone Herbicides Resistant ALS Gene in Rice

Fang-Quan WANG, Jie YANG, Fang-Jun FAN, Wen-Qi LI, Jun WANG, Yang XU, Jin-Yan ZHU, Yun-Yan FEI, Wei-Gong ZHONG

Acta Agronomica Sinica. 2018, 44(03):  324-331.  doi:10.3724/SP.J.1006.2018.00324

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Breeding and utilization of herbicide resistant rice are significant to rice production. By screening the rice germplasm, we found the herbicide resistant material “Jinjing 818”. An SNP mutation G to A was present in Acetolactate synthase (ALS) gene at 1880 bp position, leading to the alteration from serine (S, AGT) to asparagine (N, AAT), which confers herbicide resistance. In this study, 11 allelic-specific PCR (AS-PCR) primers were designed based on the functional mutation. After optimized these primers, we obtained two primer combinations F1N (S1/S9) and F1M (S1/S10), named AS-ALS marker. Using this marker detected the genetic population, its parents, F₁ hybrid, F₂ and also rice collections, inbred lines, showing that the herbicide susceptibleness allelic ALS-G could be amplified by F1N, the herbicide resistance allelic ALS-A by F1M, and heterozygous genotype by F1N and F1M simultaneously. The genotype of those tested materials perfectly matched with the phenotype of herbicide resistance or susceptibleness. Aided by AS-ALS marker selection, the homozygous ALS-A pedigrees in multi-generation backcross or self-cross showed stable herbicide resistance. Therefore, the allelic-specific PCR functional marker AS-ALS can be used in herbicide breeding efficiently, also screening herbicide resistant rice germplasm. In conclusion, the AS-ALS marker developed in this research is inexpensive and effective in breeding practice.

Identification and Gene Mapping of a Lesion Mimic Mutant spl34 in Rice (Oryza sativa L.)

Bao-Yu LIU, Jun-Hua LIU, Dan DU, Meng YAN, Li-Yuan ZHENG, Xue WU, Xian-Chun SANG, Chang-Wei ZHANG

Acta Agronomica Sinica. 2018, 44(03):  332-342.  doi:10.3724/SP.J.1006.2018.00332

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A mutant spotted leaf 34 (spl34) was screened from the progeny of indica restorer line Jinhui 10 treated with ethyl methane sulfonate (EMS). Brown lesions in spl34 exhibit on the sheath of lower leaves at the late tillering stage, then spred from the midrib to entire leaf and finally throughout the whole plant at maturity stage. Compared with the wild type, the plant height, ear length, grain number per panicle, seed setting rate and thousand-grain weight as well as the activities of protective enzymes (CAT, POD, and T-SOD) were all significantly decreased while the content of reactive oxygen species (ROS) increased in spl34. The shading assay showed that the formation of lesions in spl34 was induced by light. Histochemical analysis showed that spl34 had excessive hydrogen peroxide (H₂O₂) deposition and programmed cell death in the position of lesions. In addition, the chlorophyll fluorescence was weaker in spl34 than in the wild type under the fluorescence microscopy. There was no significant difference in blast resistance between spl34 and the wild type. Genetic analysis suggested that the phenotype of spl34 was controlled by a single recessive nuclear gene, which was mapped between InDel markers LR49 and LR52 on chromosome 4 with an interval of 200 kb. Sequencing analysis revealed that a single base substitution (G to T) occurred at 3449 bp in the DNA sequence of LOC_Os04g56480, resulting in an amino acid change from tryptophane to cysteine. The qRT-PCR results showed that the transcriptional level of LOC_Os04g56480 was down-regulated in spl34, while that of some pathogenesis-related genes was highly up-regulated when compared with the wild type.

Cloning of the Key Gene ZmCYP90B1 in Brassinosteroids Biosynthesis from Zea mays and Its Response to Adversity Stresses

Fang-Meng DUAN, Qiu-Lan LUO, Xue-Li LU, Na-Wei QI, Xian-Shun LIU, Wen-Wen SONG

Acta Agronomica Sinica. 2018, 44(03):  343-356.  doi:10.3724/SP.J.1006.2018.00343

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Brassinosteroids (BRs) as an important phytohormone, play essential roles in plant growth, development and responses to adversity stresses. The key enzyme encoded by CYP90B1 is involved in the BRs biosynthesis. However, the characteristic of CYP90B1 gene response to stress has not been reported in maize. In this study, we cloned ZmCYP90B1 gene from Zea mays, GenBank accession number KY242373, via RT-PCR in combination of RACE technique. The full-length sequence of this gene is 2058 bp and the the complete open reading frame is 1518 bp, encoding 506 amino acid peptides. The predicted protein has the molecular weight of 57.66 kD and isoelectric point of 9.54, containing one transmembrane domain and one conserved domain of p450. Multiple sequences alignment analysis indicated the predicted protein shared high similarities with CYP90B1 from other plant species. The phylogenetic tree revealed a notable difference in the evolution of CYP90B1 between dicotyledons and monocotyledons. The qRT-PCR result showed that the expression of ZmCYP90B1 was induced by drought, high salt, low temperature, ABA, Spodoptera exigua attack, and methyl jasmonate (MeJA), suggesting that ZmCYP90B1 was involved in various abiotic stresses, insect resistance and response to MeJA. Overexpressing ZmCYP90B1 in tobacco seedlings could enhance drought resistance with less water loss rate and higher SPAD value in the transgenic lines. In addition, the activities of SOD, CAT, and POD and the content of proline increased significantly in all transgenic tobacco lines than in the wild type; both MDA and ABA contents were obviously lower in the transgenic lines than in the wild type. Through expression analysis of the down-stream stress-responsive genes, we demonstrated that drought tolerance enhancement by overexpressing ZmCYP90B1 might be involved in ABA-independent pathway and related to transcriptional regulation of antioxidant- related genes.

Adaptability and Phenotypic Variations of Agronomic Traits in Common Bean Germplasm Resources in Different Environments

Lan-Fen WANG, Jing WU, Zhao-Li WANG, Ji-Bao CHEN, Li YU, Qiang WANG, Shu-Min WANG

Acta Agronomica Sinica. 2018, 44(03):  357-368.  doi:10.3724/SP.J.1006.2018.00357

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This study aimed at evaluating the phenotypic variation and environmental adaptability of common bean (Phaseolus vulgaris L.) germplasm resources. Twelve traits of 686 accessions of common bean were assessed in Harbin of Heihongjiang province, Nanyang of Henan province, Bijie of Guizhou province and Ledong of Hainan province in 2014-2015. The results showed that Ledong was the best location for the reproduction of germplasm resources from South America and Bijie was the best location for the reproduction of Chinese germplasm resources. There were large variations in the 12 traits among the 686 common bean germplasm resources and the average (across locations) coefficients of variation ranged from 8.11% of growth duration to 70.83% of plant height. Hundred-seed weight showed the highest heritability of 0.73, whereas days from sowing to flowering showed the lowest one of 0.01. The correlation and path analysis revealed that number of pods per plant was the most important factor affecting the yield per plant. Two hundred and eighteen specific germplasm resources were identified with dwarf, large-seed, and early maturity and so on, among which nine had three favorable traits and 53 had two favorable traits simultaneously.

Genetic Analysis and Molecular Characterization of a New Allelic Mutant of Vp15 Gene in Maize

Rui WANG, Xiu-Yan ZHANG, Yang-Song CHEN, Yi-Cong DU, Ji-Hua TANG, Guo-Ying WANG, Jun ZHENG

Acta Agronomica Sinica. 2018, 44(03):  369-375.  doi:10.3724/SP.J.1006.2018.00369

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We identified a new maize viviparous mutant during seed reproduction, designated as vp-like4.This mutant phenotype was steadily inherited and genetically regulated by a single recessive gene. Using an F₂ segregation population derived from vp-like4 and inbred line Mo17, we mapped the target gene in an interval from 173.8 to 175.6 Mb on chromosome 5 by the BSR-Seq strategy. Using genomic sequence database, we found that viviparous gene Vp15 is located in this mapping region. The maize Vp15 gene encodes the molybdopterin synthase small subunit, which is required in the process of catalyzing the reaction from carotenoid to ABA. The heterozygous plants from two independent vp15 mutants, vp15-umu1 and vp15-DR1126, were used to cross with vp-like4 heterozygous plants, showing a 3:1 segregation ratio for normal and viviparous kernels. The genomic sequence analysis revealed that vp-like4 mutant had a 60-bp deletion in the second exon and 3’-untranslated region of Vp15 gene, which is different from vp15-umu1 and vp15-DR1126 both mutated from a Mutator transponson inserting in the second exon of Vp15 gene. Further RT-PCR analysis revealed that the expression level of vp15 was significantly lower in vp-like4. Taken together, these evidences suggest that vp-like4 is a new allele mutant from vp15.

Cloning and Imprinting Characterization Analyses of Paternally Expressed Gene ZmVIL1 in Maize Endosperm

Chao-Xian LIU, Jiu-Guang WANG, Xiu-Peng MEI, Ting-Ting YU, Guo-Qiang WANG, Lian ZHOU, Yi-Lin CAI

Acta Agronomica Sinica. 2018, 44(03):  376-384.  doi:10.3724/SP.J.1006.2018.00376

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Imprint genes play important roles in maize seed development. ZmVIL1 is a paternal-preferentially expressed gene. In this study, the full length of ZmVIL1 cDNA was cloned by RACE, which is about 2.2 kb and encodes a protein consisting of 598 amino acids. The analyses of allele expression of ZmVIL1 in endosperm and embryo at 14 days after pollination (DAP) of hybrids from reciprocal crosses between B73 and Mo17 indicated that ZmVIL1 was maternally imprinted in endosperm, while not in embryo. The allele expression was extensively evaluated in 14 DAP endosperm of hybrids form reciprocal crosses of Zheng 58 and Chang 7-2, Huang C and 178, PH6WC and PH4CV, and in 10-28 DAP endosperm of hybrids form reciprocal crosses of B73 and Mo17, suggesting that ZmVIL1 was gene-specific and binary imprinting and consistently imprinted in endosperm from 12 to 28 DAP. Expression pattern analyses demonstrated ZmVIL1 was constitutively expressed from vegetative to reproductive stages. ZmVIL1 was strongly expressed in seed at 10 DAP, immature tassels, immature ears and silk, and secondly expressed in ovule, embryo at 25 DAP and root, suggesting that ZmVIL1 plays important roles in maize seed and flower development.

QTL Mapping of Yield Traits Using Drought Tolerance Selected Backcrossing Introgression Lines in Sunflower

Pin LYU, Hai-Feng YU, Jian-Hua HOU

Acta Agronomica Sinica. 2018, 44(03):  385-396.  doi:10.3724/SP.J.1006.2018.00385

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Drought is one of the most important factors to decrease the yield of sunflower. The BC₃F₂ selected backcrossing introgression lines of oil sunflower population including 45 lines were developed by drought-tolerance screening for yield using Helianthus annuus K55 with excellent comprehensive characters and drought sensitivity as recurrent parent and K58 with drought-tolerance as donor parent. The genotypes of selected backcrossing introgression lines were obtained with the whole genome SSR and SNP markers. QTLs affecting five yield traits were detected under both drought stress and well watered conditions in Hohhot and Wuchuan respectively by one-way ANOVA and Chi-square test based on the Genetic Hitchhiking Effect. The QTLs detected by one-way ANOVA were grouped into three types based on their behaviors: type I was the QTLs detected in both watered conditions, including four QTLs affecting hundred-seed weight (HSW) in Wuchuan and two QTLs affecting seed yield (SY) and three QTLs affecting filled seeds per plant (FSP) in Hohhot, which were considered to be able to directly contribute to drought tolerance; type II was the QTLs detected only under drought stress, including 30 QTLs in Hohhot and 27 QTLs in Wuchuan; type III was the QTLs detected only in well watered condition, including 38 QTLs in Hohhot and 64 QTLs in Wuchuan. There 274 loci were detected by chi-square test, among them 14 loci could be detected by ANOVA and chi-square test simultaneously, which might be the key loci for drought tolerance of sunflower. The results lay a foundation of efficient drought tolerance molecular breeding and provide useful drought tolerance materials for sunflower.

Cloning of BoLH27 Gene from Cabbage and Phenotype Analysis of Transgenic Cabbage

Yun-Fei LIANG, Lin-Cheng ZHANG, Quan-Ming PU, Zhen-Ze LEI, Song-Mei SHI, Yu-Peng JIANG, Xue-Song REN, Qi-Guo GAO

Acta Agronomica Sinica. 2018, 44(03):  397-404.  doi:10.3724/SP.J.1006.2018.00397

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bHLH transcription factor plays an important role in plant growth, development and morphological control. In order to explore BoLH27 gene regulatory function for leaf development and morphologic formation, the BoLH27 gene was cloned from cabbage (Brassica oleracea L.) variety 519. Sequence analysis indicated that the length of BoLH27 gene was 795 bp, which encoded 264 amino acids. The BoLH27 protein contained conservative structure domains of the bHLH family. The sense BoLH27 gene was transformed into cabbage variety 519 by Agrobacterium mediated method, PCR analysis exhibited that BoLH27 was genetically transformed into nine individual plants, qRT-PCR analysis revealed that BoLH27 had higher expression level in T₂ transgenic cabbage than in wild type. The phenotype at rosette stage of transgenic cabbage grown in the test base was obvious, showing elongated the stems and leaves, elongated petiole, purple stems and petiole, and flat leaves without upward inward curling trend. It suggested that BoLH27 may play important roles in the control of leaves development.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Comparison in Nitrogen Metabolism and Photosynthetic Characteristics between Japonica Rice Varieties Differing in Nitrogen Sensitivity

Cheng-Xin JU, Zhu-Biao ZHOU, Bu-Hong ZHAO, Zhi-Qin WANG, Jian-Chang YANG

Acta Agronomica Sinica. 2018, 44(03):  405-413.  doi:10.3724/SP.J.1006.2018.00405

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Understanding the physiological characters associated with nitrogen (N) use efficiency (NUE) is very important in selecting and breeding N-efficient varieties. However, the information on such characters is very limited. Four japonica rice varieties, i.e., two nitrogen sensitive varieties, Huaidao 5 (HD-5) and Lianjing 7 (LJ-7), two nitrogen insensitive varieties, Ningjing 1 (NJ-1) and Yangjing 4038 (YJ-4), were grown in the field, and two N rates, 0 and 200 kg ha^-1, were applied during the growing season. The yield components, NUE and aboveground physiological characters were investigated. The nitrogen sensitive varieties produced higher grain yield, exhibited higher NUE than nitrogen insensitive varieties at N rates of 0 and 200 kg ha^-1. When compared with the nitrogen insensitive varieties, the nitrogen sensitive varieties had a higher photosynthetic rate and N accumulation, stronger activity of the enzymes involved in N metabolism, higher photosynthetic NUE, more accumulation of soluble sugars and starch in stems and sheaths at heading time, and more remobilization of nonstructural carbohydrate from stems to grains during grain filling. These physiological traits resulting in higher grain yield and nitrogen use efficiency are important and can be used as physiological indexes to select and breed high-yielding and N-sensitive rice varieties.

Photosynthetic Characteristics, Dry Matter Accumulation and Translocation, Grain Filling Parameter of Three Main Maize Varieties in Production

Tian-Jun XU, Tian-Fang LYU, Jiu-Ran ZHAO, Rong-Huan WANG, Chuan-Yong CHEN, Yue-E LIU, Xiu-Zhi LIU, Yuan-Dong WANG, Chun-Ge LIU

Acta Agronomica Sinica. 2018, 44(03):  414-422.  doi:10.3724/SP.J.1006.2018.00414

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The objective of this study was to explore yield-forming characteristics of high yield maize varieties. Using three widely cultivated maize varieties Zhengdan 958 (ZD958), Xianyu 335 (XY335) and Jingke 968 (JK968), we tested grain yield, photosynthetic characteristics, dry matter accumulation and translocation, and grain filling characteristics. The yield of JK968 was the highest, and was 14.55% and 7.93% higher than that of ZD958 and XY335, respectively. The photosynthetic rate and canopy photosynthetic capacity showed JK968 > XY335 > ZD958 and silking stage > milk stage. The ear photosynthetic rate of JK968 at silking stage and milk stage was 7.84% and 16.78% higher than that of XY335, as well as 22.23% and 24.44% higher than that of ZD958, respectively. The photosynthetic capacity of JK968 at silking stage and milk stage was 38.77% and 58.41% higher than that of XY335, as well as 50.83% and 56.49% higher than that of ZD958, respectively. Dry matter accumulation after silking stage, the transfer amount of dry matter, translocation efficiency of dry matter and contribution to grain dry matter for JK968 were the highest, with 13.72%, 21.20%, 6.32%, and 4.77% higher than those of XY335, as well as 31.87%, 39.96%, 18.49%, and 10.42% higher than those of ZD958, respectively. There was a big difference in grain filling parameters among those different varieties, the average filling rate of JK968 (0.73 g 100-grain^-1 d^-1) and XY335 (0.75 g 100-grain^-1 d^-1) was higher than that of ZD958 (0.67 g 100-grain^-1 d^-1) and the active grain filling period of ZD958 (53.69 d) was longer than that of the JK968 (51.02 d) and XY335 (48.95 d). Maize yield was significantly correlated with net photosynthetic rate at P < 0.05, and with the dry matter accumulation after silking stage and the translocation rate at P < 0.01. Thus, JK968 had higher photosynthetic efficiency, dry matter accumulation after silking stage, translocation rate, grain filling rate and longer grain filling period, which is the main reason that JK968 had the higher yield than ZD958 and XY335.

Effects of Foliage Spray of Se on Absorption Characteristics of Se and Quality of Purple Sweet Potato

Song HOU, Xia TIAN, Qing LIU

Acta Agronomica Sinica. 2018, 44(03):  423-430.  doi:10.3724/SP.J.1006.2018.00423

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In order to clarify the absorption characteristics of selenium (Se), root yield, Se utilization, content of amino acids and mineral elements in purple sweet potato, a field experiment of foliage spraying with three treatments of 0, 30, and 60 g ha^-1 pure Se application were carried out in 2015 and 2016 respectively. The root yield of purple sweet potato received no significantly effect from Se foliage spray, the Se content, organic Se content and the Se accumulation in root were improved, with a root Se content of 311.3 µg kg^-1 (DW), 8.54 times as high as that of the control under 60 g ha^-1 Se application. Se content and accumulation amount in root increased and the utilization rate of Se decreased significantly with the increase of Se application, while the content of organic Se in root received no significantly effect from Se foliage spray. With increasing Se application, the content of crude protein in root of purple sweet potato was significantly increased, which was 11.67% and 29.71% higher than that of CK under Se treatment of 30 g ha^-1 and 60 g ha^-1 respectively. Under 60 g ha^-1 Se application treatment, seven essential amino acids for human body contained in roots increased significantly except Threonine, and the other six nonessential amino acids in roots also increased significantly such as Asparagine, Serine, Glutamic acid, but the content of Cysteine decreased. Se application treatments increased the contents of K, Na, Mg, Fe, Cu and decreased the contents of Ca, Mn in roots of purple sweet potato, but had no effect on content of Zn. The results of this study are of significance guiding production of Se-enriched purple sweet potato.

Influences of Rape Intercropping with Chinese Milk Vetch and Straw Mulching on Productive Benefits in Dryland of Southwest China

Quan ZHOU, Long-Chang WANG, Shu-Min MA, Xiao-Duan ZHANG, Yi XING, Sai ZHANG

Acta Agronomica Sinica. 2018, 44(03):  431-441.  doi:10.3724/SP.J.1006.2018.00431

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In dryland of the southwest of China, the eco-environment of farmland is extremely fragile, and the application of green manure is not enough. The seasonal drought is a key factor limiting the rape production. In order to improve rape yield and explore the application method of green manure, we compared the effects of intercropping and straw mulching on photosynthetic characteristics, agronomic traits, biomass, root morphology, rapeseed quality and yield. Intercropping Chinese milk vetch and straw mulching substantially improved the agronomic traits (diameter of root crown, leaf number, effective branch number and number of pods per plant), the root morphology (total root length, total root volume, total root surfarea and average root diameter), and the biomass of root, stem and leaf at stem elongation, flowering and podding stages of rape. At the same time, it also increased the photosynthetic rate at seeding stage. Water use efficiency in intercropping treatment and straw mulching treatment was increased by 31.12% and 39.89% as compared with rape monoculture. In addition, treatments of intercropping, straw mulching and intercropping with straw mulching significantly increased rape yield by 10.30%, 13.20%, and 40.16% as compared with rape monoculture. Our findings revealed that intercropping Chinese milk vetch and straw mulching are helpful to improve the agronomic trait, biomass and root morphology, resulting in yield increase in rape.

Response of Maize (Zea mays L.) Yield to Climatic Ecological Condition on the South Yellow-Huaihe-Haihe Rivers Plain

Pan-Pan AN, Bo MING, Peng-Fei DONG, Miao ZHANG, Da-Zhao HUANG, Ya-Li ZHAO, Chao-Hai LI

Acta Agronomica Sinica. 2018, 44(03):  442-453.  doi:10.3724/SP.J.1006.2018.00442

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In view of the changes of climatic condition and farming system in recent years, a field experiment during growing season 2015-2016 was conducted to study the responses of maize yield to ecological condition, and discuss the effects of climatic factors on maize yield under condition of different sowing dates on the south Yellow-Huaihe-Haihe Rivers plain. A main maize cultivar Zhengdan 958 was sown at seven sowing dates (S1: 15 April; S2: 30 April; S3: 15 May; S4: 30 May; S5: 14 June; S6: 29 June; S7: 14 July). There was significant difference in maize yield because of the different climatic conditions between years and between conditions of sowing dates. The yield of spring-sowing maize was significantly higher than that of summer-sowing maize, which deceased significantly with postponing sowing date. With postponing maize sowing date, the average daily temperature during seeding stage increased, the average daily temperature from anthesis to maturity and growing degree-days during whole growth period decreased, and the growth period of maize shortened gradually. At the density of 67 500 plants ha^-1,100-grain weight made more contribution to yield than grain number per ear. The main climatic factors affecting 100-grain weight and grain number per ear were growing degree-days during whole growth period, especially from anthesis to maturity stage. The main climatic factors affecting maize yield were the average daily temperature range (r = 0.696^**) and average daily temperature (r= -0.638^*) at seedling stage, the growing degree-days (r = 0.822^**) and average daily temperature (r = 0.723^**) from anthesis to maturity stage, and the growing degree-days during whole growth period (r = 0.843^**). Therefore, the sowing date of the spring-sowing maize can be postponed from the midmonth of April to May 1st, which can achieve high and stable grain yield because of decreasing the harmful effects of cloudy and rainy at flowering and high temperature heat damage. For summer maize, the suitable sowing date should be as early as possible after wheat harvest. The early sowing date of summer maize not only increase growing degree-days, but create suitable temperature condition that the average daily temperature is low during seedling stage and high from anthesis to maturity stage, and provide suitable condition for delaying harvest and facilitating mechanical grain-harvest.

RESEARCH NOTES

Effects of Straw Incorporation with Reducing Chemical Fertilizers on Nutrient Absorption and Utilization and Grain Yield of Double-cropping Late Rice under Mechanical Harvest

Yan-Hua ZENG, Jian-Fu WU, Yong-Jun ZENG, Cheng-Gen FAN, Xue-Ming TAN, Xiao-Hua PAN, Qing-Hua SHI

Acta Agronomica Sinica. 2018, 44(03):  454-462.  doi:10.3724/SP.J.1006.2018.00454

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Replacing chemical fertilizer with straw incorporation is an important way to reduce fertilizer application and improve fertilizer efficiency. The objective of six year field location experiments under the same N, P, and K inputs, was to systematically explore the effects of straw incorporation and reducing chemical fertilizers on plant nutrient absorption and utilization under mechanical harvest, so as to provide a basic support for the reasonable utilization of straw resource, rice high yield and its nutrient management measure in the southern rice zone. The experiments were conducted being in the cultivated land quality monitoring station of Wenzhen town, Jiangxi province, Wufengyou T025, super hybrid late rice cultivar. Four treatments were included: total straw incorporation and reducing chemical fertilizers (SI+NPK), straw burning and reducing chemical fertilizers (SB+NPK), chemical fertilizers (NPK), and no chemical fertilizers (CK). The three fertilization treatments were with equal quantity of fertilizers (N 195 kg ha^-1, P₂O₅ 87.8 kg ha^-1, and K₂O 175.5 kg ha^-1) whatever chemical and organic ones. The variation of rice yield and nitrogen, phosphorus, potassium uptake and their utilization efficiency were determined. SI+NPK of early rice in continuous six years was avail able to balance the panicle and spikelet, and hold steady grain yield of late rice, with the same level compared with SB+NPK and NPK. Compared with NPK treatment, SI+NPK treatment had lower N, P, K contents and accumulation at the vegetative growth stage including tillering stage and panicle initiation, but higher those at the reproductive stage such as heading stage and maturity stage. Moreover, the P, K accumulation was significantly increased in SI+NPK treatment. Compared with NPK treatment, SI+NPK treatment enhanced N, P, K fertilizer harvest index, agronomy efficiency (AE), recovery efficiency (RE) and partial factor productivity (PFP) significantly, but SB+NPK treatment only enhanced K fertilizer harvest index, AE, RE, and PFP significantly. Meanwhile, compared with SB+NPK treatment, SI+NPK treatment increased N, P, K fertilizer harvest index, AE, RE and PFP. Overall, straw incorporation replacing partial chemical fertilizer of early rice, in contrast to straw burning and chemical fertilizers application, is proved to be a feasible way to stabilize grain yield of late rice, enhance nutrient utilization efficiency, and realize the efficient utilization of soil nutrient resource in the southern rice zone.

Protoplast Isolation and Fusion Induced by PEG with Leaves and Roots of Tea Plant (Camellia sinensis L. O. Kuntze)

Zhang PENG, Hua-Rong TONG, Guo-Lu LIANG, Yi-Qi SHI, Lian-Yu YUAN

Acta Agronomica Sinica. 2018, 44(03):  463-470.  doi:10.3724/SP.J.1006.2018.00463

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Plant protoplasts are important materials for studies on plant cell culture, somatic cell fusion, genetics and breeding. This work established a stable and efficient method for getting a large amount of vital and intact protoplasts from young leaves and young roots of Fudingdabai tea plant. For protoplast isolation, the young leaves of tea seedlings grown in the condition of constant temperature (23°C) and dark or shading were the best materials, and the young radicle of tea plant was also the better, While the healthy young leaves of tea plants grown in tea plantation were used as materials, only a small quantity of viable protoplasts mixed with a large number of cell fragments were obtained. The optimal enzyme solution for protoplasts isolation from young leaves of tea seedlings contained 1.5% cellulase + 0.1% macerozyme + 0.5% pectolyase + 0.4 mol L^-1 mannitol + 20 mmol L^-1 MES, and that from radicle of tea seedlings contained 1.5% cellulase + 0.3% macerozyme + 0.5% pectolyase + 0.4 mol L^-1 mannitol + 20 mmol L^-1 MES. Protoplasts with high yield and viability were purified when incubated in a shaker with low speed (55 r min^-1 and 50 r min^-1 respectively) under constant temperature (23°C) for 7 h and 8 h, and then centrifuged at 15×g for 4 min. PEG-6000 was used to induce the fusion of protoplasts from young leaves and radicle of tea plants. The fusion time, the concentration of fusion agent PEG-6000 were discussed. The optimal protoplast infusion conditions were induction with 40% PEG-6000 for 20 min, and the fusion rate was about 10%.