Table of Content

12 February 2018, Volume 44 Issue 02

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Genetic Contribution of Lumai 14 to Qingnong 2 Revealed by SSR and SNP Markers

Yu-Gang LI, Min REN, Lv SUN, Sheng-Jian WANG, Mei HAN, Zhen-Qing LI, Xiao-Ling ZHAI, Xiao-Yan DAI, Yuan-Jiang HOU, Hong-Mei GE

Acta Agronomica Sinica. 2018, 44(02):  159-168.  doi:10.3724/SP.J.1006.2018.00159

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Lumai 14, a widely planted wheat variety, is the parents of more than 40 bread wheat varieties, among which Qingnong 2 (Lumai 14/Yannong 15//Aiganmai) has been released in recent years. In this study, the inheritance from Lumai 14 to Qingnong 2 was evaluated using 350 SSR markers and 26 026 SNPs detected by iSelect 90k SNP array. Pedigrees show that Lumai 14 and Yannong 15 contain 1/4 and 1/2 blood of Youbaomai, respectively. Genomic marker screening confirmed that Lumai 14 and Yannong 15 shared 55.42% common SSR loci and 71.53% common SNP loci. Polymorphic markers between them were used to disclose that Qingnong 2 inherited more SSR and SNP loci from Lumai 14 (54.11% and 72.55%, respectively) than from Yannong 15 (36.30% and 26.98%, respectively). In Qingnong 2, chromosomes 2B, 3B, and 6A harbored more than 50% SNPs from Yannong 15, whereas, the remaining 18 chromosomes carried more than 50% SNPs from Lumai 14. The parental genetic compositions were present mainly in large chromosomal segments in Qingnong 2. Phenotyping investigation in multi-locations across years indicated that Qingnong 2 was similar to Lumai 14 in length and width of flag leaf, length of first internode, length from flag leaf pulvinus to spike base, earing degree, thousand-grain weight, and grain length, and similar to Yanong 15 in plant height and growth duration. This results provide valuable information for molecular marker-assisted selection in wheat breeding.

Orginal Article

Identification and Gene Mapping of a Floral Organ Number Mutant mf2 in Rice (Oryza sativa)

Xian-Cheng YAN, Li-Kai CHEN, Yu-Hua LUO, Wen-Long LUO, Hui WANG, Tao GUO, Zhi-Qiang CHEN

Acta Agronomica Sinica. 2018, 44(02):  169-176.  doi:10.3724/SP.J.1006.2018.00169

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A rice floral organ mutant mf2 (multi-floret 2) was identified from Hanghui 7, an indica restorer line in rice (Oryza sativa L.), which was treated with heavy ion irradiation. The glumes, lodicules, stamens, pistil of the mutant increased, and most of the spikelets had 2-3 flowers. The palea and lemma of mf2 mutant were dehiscent, the shape and number of vascular bundles were different from those of the wild-type. Scanning electron microscope analysis revealed that the flowers variation of mf2 had been formed in the differentiation of the primordium during the spike differentiation stage. The heading date of the mf2 mutant was delayed, the plant height was decreased, but the number of panicles was increased, showing that the vegetative growth of the mutant was also affected. Genetic analysis showed that the mf2 mutant phenotype was controlled by a recessive nuclear gene. There are 321 recessive individuals from the F₂ segregation population were used to fine map MF2. Finally, MF2 was located in a 102 kb physical interval between markers SSR39108 and InDel39210 on chromosome 1.

Cloning and Expression Analysis of BoSPI Induced by Self-pollination in Brassica oleracea L. var. capitata

Min PU, Shao-Lan LUO, Xiao-Ping LIAN, He-Cui ZHANG, Xiao-Jing BAI, Yu-Kui WANG, Tong-Hong ZUO, Qi-Guo GAO, Xue-Song REN, Li-Quan ZHU

Acta Agronomica Sinica. 2018, 44(02):  177-184.  doi:10.3724/SP.J.1006.2018.00177

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Self incompatibility is a complex and comprehensive genetic mechanism formed in the long-term evolution, which prevents inbreeding and promotes heterosis. Mining functional genes involving in self incompatibility has an important significance for the study of self incompatibility in Brassica oleracea L. var. capitata. In this study, we identified a gene named BoSPI which expression was up-regulated and induced by self-pollination based on the stigma transcriptome data in 0-60 min self-pollination and cross-pollination. BoSPI contains an open reading frame (ORF) with the length of 534 bp, encoding a protein of 177 amino acid residues without introns, which contains four conserved EF-hand domains without signal peptide and transmembrane domain, the theory isoelectric point of BoSPI is 4.21. In addition, diverse cis-acting promoter elements involved in fungal elicitor response, metabolic regulation and organ formation were discovered in the upstream 2000 bp of initial codon of BoSPI. BoSPI could be expressed as a 17 kD protein in E. coli BL21 (DE3). The expression level of BoSPI was the highest in stigmas and lower in petals, sepals, leaves and stamens of cabbage after self-pollination. Subcellular localization analysis revealed that BoSPI encoded a protein localized in the cell membrane and cytoplasm. The expression of BoSPI gene was significantly induced by self pollination after 30 minutes. These results suggest that BoSPI is involved in the molecular processes of the stigma response to self-pollen stimulation, which may be a new functional gene related to the self incompatibility of Brassica oleracea L. var. capitata.

An R2R3-MYB Transcription Factor GmMYB184 Regulates Soybean Isoflavone Synthesis

Ying ZHU, Shan-Shan CHU, Pei-Pei ZHANG, Hao CHENG, De-Yue YU, Jiao WANG

Acta Agronomica Sinica. 2018, 44(02):  185-196.  doi:10.3724/SP.J.1006.2018.00185

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Isoflavones comprise a group of secondary metabolites produced almost exclusively by plants in the legume family, including soybean [Glycine max (L.) Merr.]. They play vital roles in plant defense and have many beneficial effects on human health. Isoflavone content is controlled by multiple genes and complex metabolic networks. The modification of certain structural genes in the isoflavone pathway by genetic engineering has been unable to significantly improve isoflavone content. The identification and application of transcription factors specific to the isoflavone pathway may effectively resolve this problem. An R2R3-type transcription factor related to isoflavone content, GmMYB184, was cloned and its function was identified. Subcellular localization study confirmed the nuclear localization of GmMYB184. The expression profile of GmMYB184 was similar to that of IFS2 (isoflavone synthase 2), which was consistent with the isoflavone accumulation pattern. In addition, GmMYB184 and IFS2 mainly expressed in roots and mature seeds, and the expression level increased by seeds maturing. Glutathione (GSH) induction expression analysis showed that both GmMYB184 and IFS2 were induced by GSH, indicating they could be involved in similar biological processes. To examine whether GmMYB184 could regulate the expression of isoflavone biosynthesis-related genes, a dual luciferase reporter gene assay was performed, showing that GmMYB184 could increase the expression of IFS2 and CHS8 (chalcone synthase 8) to five and seven folds, respectively. Finally, to further verify the function of GmMYB184 during isoflavone biosynthesis, we constructed and then transformed overexpression vector and RNAi vector for GmMYB184 to soybean hairy roots respectively. RNAi silencing of GmMYB184 in hairy roots resulted in reduction of isoflavones. However, overexpression of GmMYB184 was not sufficient to increase isoflavone contents in hairy roots. Taken together, these results provide a theoretical foundation for the molecule mechanism explanation and genetic improvement of isoflavone content in soybean.

Genome-wide Analysis and Expression Profiling of SPS Gene Family in Brassica nupus L.

Li ZHANG, Hong-Ju JIAN, Bo YANG, Ao-Xiang ZHANG, Chao ZHANG, Hong YANG, Li-Yuan ZHANG, Lie-Zhao LIU, Xin-Fu XU, Kun LU, Jia-Na LI

Acta Agronomica Sinica. 2018, 44(02):  197-207.  doi:10.3724/SP.J.1006.2018.00197

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Sucrose phosphate synthase (SPS) is the rate-limiting enzyme that controls the sucrose biosynthesis in plants and has great influence on transportation and accumulation of photosynthate. In this study, we identified 11 members of the SPS gene family in the oilseed rape (Brassica nupus L.) genome. These SPS genes were classed into clusters A, B, and C according to gene structure and phylogenetic relationship. Gene structure prediction indicated that BnSPS genes were highly conserved, in which BnSPSC-1 consisted five exons and others consisted 11-15 exons. Promoter cis-element analysis indicated that BnSPS genes had not only essential responsive elements but also some types of elements potentially responsive to stresses or hormone responses. The qRT-PCR assay showed tissue-specific expressions of BnSPS genes with rich expressions of BnSPSA1 in flower, BnSPSB in leaf, bud and flower, BnSPSC in leaf, and BnSPSA2 in various tissues. The relative expression levels of BnSPSA1 and BnSPSC were higher in high-biomass rapeseed varieties than in low-biomass rapeseed varieties, whereas, that of BnSPSB was higher in low-biomass rapeseed varieties, suggesting that SPS genes are closely ralated to biological yield of rapeseed. This study provides basic information for functional study and utilization of BnSPS genes.

Regeneration Capacity Evaluation of Some Largely Popularized Wheat Varieties in China

Wei ZHANG, Mi-Qi YIN, Pei ZHAO, Ke WANG, Li-Pu DU, Xing-Guo YE

Acta Agronomica Sinica. 2018, 44(02):  208-217.  doi:10.3724/SP.J.1006.2018.00208

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Strong genotype dependence exists in wheat doubling haploid and genetic engineering breeding, in which high regeneration ability is a main restrain. In this study, we evaluated the regeneration abilities of various explants of 24 commercial popularized wheat varieties and a new breeding line (CB037) with high powdery mildew resistance. The explants used in the two-year experiment were anther, immature embryo, and mature embryo. The regeneration potential was assessed based on callus induction rate, callus differentiation rate, and shoot induction rate. The plantlet regeneration rates of the all genotypes tested were 0-41.75% for anther culture, 2.25%-531.92% for immature embryo culture, and 3.24%-84.34% for mature embryo culture, showing significant differences among genotypes. Generally, immature embryos had stronger regeneration ability (119.79%) than mature embryos (36.23%) and anthers (4.91%). Among all the used genotypes, CB037 showed the highest regeneration rates for the three explant types. Lunxuan 987, Yangmai 16, Neimai 836, Kenong 199, Xinchun 6, Zhengmai 366, Zhengmai 9023, Xindong 20, Yannong 19, and Chuanmai 42 exhibited ideal regeneration abilities in immature embryo culture; Xinchun 6, Jingdong 8, Shimai 4185, Kenong 199, and Luanxun 987 performed good in mature embryo culture; and Shimai 4185 and Han 6172 were characterized with high regeneration rate of green plantlet in anther culture. Plant regeneration efficiency of wheat was closely associated with genotype and explant type. The same explant type from different genotypes showed significantly different regeneration abilities, and different explants of the same genotype showed different regeneration abilities. However, there was no correlation among regeneration abilities of the three types of explants. The selected genotypes with high regeneration potential are recommended for application in genetic and cell engineering breeding of wheat.

Cloning and Expression Analysis of Galactosyltransferase Gene GhGalT1 Promoter in Cotton

Li-Xia QIN, Jing LI, Huan-Yang ZHANG, Sheng LI, Meng-Jie ZHU, Gai-Li JIAO, Shen-Jie WU

Acta Agronomica Sinica. 2018, 44(02):  218-226.  doi:10.3724/SP.J.1006.2018.00218

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Glycosytransferases (GTs) transfer an activated sugar donor to a specific acceptor to form glucosidic bond, which are regulated by various abiotic and biotic stresses, and may play a role in plant responses to changes in living conditions. In this study, a 539 bp fragment of GhGalT1 5′-flanking sequence was isolated from upland cotton Coker 312 by PCR, designated pGhGalT1. Analysis of pGhGalT1 sequence by PlantCARE revealed it contained not only putative CAAT box, TATA box sequence, but also MBS, HSE, TC-rich repeats, MYCCONSE and CGTCA-motif cis-acting element which involved in drought, heat, dehydration, defense and stress responsiveness. Thus, we constructed it into pBI101-GUS vector and formed pGhGalT1::GUS fusion expression vector (pBI101-pGhGalT1-GUS), then transferred the vector into Arabidopsis by the Agrobacterium-mediated floral dip method, and successfully obtained positive transgenic plants by screening test of resistance to kanamycin and PCR detection. Histochemical assay of T₃ generation of transgenic Arabidopsis revealed that GUS activities were mainly accumulated in root tips of primary and lateral roots in 5- to 15-day-old seedlings, and less strongly in cotyledons and rosette leaves. The histochemical staining results and the assay of quantitative GUS activity and GUS gene expression under abiotic stresses and hormone treatments revealed that the GhGalT1 promoter was salt-/osmotic-/6-BA-/MeJA-/BL-inducible. These findings contribute to the selection of a suitable promoter for crop molecular improvement.

Establishment of CRISPR/Cas9 Genome Editing System Based on GbU6 Promoters in Cotton (Gossypium barbadense L.)

Ji-Yang LI, Jian-Feng LEI, Pei-Hong DAI, Rui YAO, Yan-Ying QU, Quan-Jia CHEN, Yue LI, Xiao-Dong LIU

Acta Agronomica Sinica. 2018, 44(02):  227-235.  doi:10.3724/SP.J.1006.2018.00227

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CRISPR/Cas9 genome editing is a powerful tool for genes functional analyses, and the mutation of endogenous genes has been successfully implemented in many organisms using the tool. Two cloned U6 promoter from sea island cotton Xinhai 16 were used to construct CRISPR/Cas9 gene editing vectors with target (GbGGB and GBERA1) DNA fragments from Xinhai 16 respectively. Through PEG method, the core fragments (including GbU6::sgRNA and CAMV35S::Cas9) of the CRISPR/Cas9 gene editing vectors enriched by PCR method were transformed into the cotton protoplast prepared from the embryo callus of Xinhai 16. The mutation of endogenous target genes was successfully detected by a restriction enzyme PCR (RE-PCR) assay of protoplast genome. The cloning and sequencing of the PCR product, showed that the two Cas9-GbU6-sgRNA vectors could both induce targeted mutagenesis. Sequence analysis revealed that most of the mutations were nucleotide substitutions and the few were nucleotide deletion. The results indicate that the CRISPR/Cas9 gene editing vector system based on GbU6 promoter can realize targeted mutagenesis in sea island cotton, which provides an important technical basis for cotton functional genomics research.

Sequence Characteristics and Expression Analysis of Potassium Transporter Gene GhHAK5 in Upland Cotton (Gossypium hirsutum L.)

Mao-Ni CHAO, Qing-Yu WEN, Zhi-Yong ZHANG, Gen-Hai HU, Jin-Bao ZHANG, Guo WANG, Qing-Lian WANG

Acta Agronomica Sinica. 2018, 44(02):  236-244.  doi:10.3724/SP.J.1006.2018.00236

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KUP/HAK/KT potassium transporter gene family plays an important role in the absorption of K⁺ in plants. Identification and cloning of potassium transporter genes in cotton are helpful to improve potassium absorption, and facilitate the increase of yield and quality in cotton. Based on the genome sequence of upland cotton, we identified the potassium transporter gene GhHAK5 by homologous cloning, and amplified its CDS sequence from upland cotton variety Baimian 1. The CDS of GhHAK5 was 2451 bp, encoding a protein with 816 amino acids. The molecular weight and isoelectric point of this protein were 91.23 kD and 8.15, respectively. The GhHAK5 protein contained a conserved domain “K-trans” (Pfam02705) and a symbolic amino acid sequence GXXXGDXXXSPLY of KUP/HAK/KT family gene, and had 11 transmembrane domains. Phylogenetic tree analysis demonstrated that GhHAK5 had a close relationship with AtHAK5, followed by OsHAK5, and they all belong to Cluster I evolutionary cluster. The subcellular localization experiment indicated that GhHAK5 was located in plasma membrane, which is consistent with its function as a potassium transporter involved in K⁺ uptake. The expression of GhHAK5 was high in roots, but low in leaf, stem, petal, fiber and sepal, and induced by low potassium environment. These results provide a foundation for understanding the function of GhHAK5 and breeding varieties with high potassium efficiency in cotton.

Endosperm Structure of Grains at Different Positions of Rice Panicle and Regulation Effect of Irrigation Regimes on It during Grain Filling

Li-Min YUAN, Ming-Fei ZHAN, Xing-Chuan ZHANG, Zhi-Qin WANG, Jian-Chang YANG

Acta Agronomica Sinica. 2018, 44(02):  245-259.  doi:10.3724/SP.J.1006.2018.00245

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In this study, an indica cultivar Yangdao 6 and a japonica cultivar Wuyunjing 24 were used to observe the changes in endosperm structure of grains at different positions of panicle with scanning electron microscope. Three irrigation treatments, namely shallow water layer (CK), alternate wetting and moderate drying (WMD), and alternate wetting and severe drying (WSD), were designed to investigate the effect of irrigation regimes on grain yield and grain endosperm structure. The endosperm structure formation in grains was earlier at the upper part of panicle than at the mid part of panicle, and earlier than at the lower part of panicle; the formation was earlier on a primary branch than on a secondary branch, and earlier in superior grains than in inferior grains. Compared with CK, WMD significantly increased grain yield. The starch granule in endosperm of grains at the lower part of panicle showed more compact arrangement, and that in the back part of grains was more crowded and even more adhered each other under WMD than under CK. Under WSD, the endosperm structure in grains showed that the starch granule arrangement was looser, the granule volume was decreased, and the differences in granule size and the gap between granules were increased, relative to those under CK. The effect of irrigation regimes on endosperm structure varied with grain positions, which was the most significant on the belly of grains at the secondary branch located at the lower part of panicle. The results suggest that the formation of endosperm structure in the grains at different parts of panicle is closely related to days after anthesis. WMD may improve, whereas WSD deteriorate, the endosperm structure of grains at the lower part of rice panicle. Soil water potential -20 kPa can be used as the low limit of soil water potential index in the water-saving irrigation for improving endosperm structure in grains during the grain filling period of rice.

Relationship between Grain Filling Parameters and Grain Weight in Leading Wheat Cultivars in the Yellow and Huai Rivers Valley

Yong-Jie MIAO, Jun YAN, De-Hui ZHAO, Yu-Bing TIAN, Jun-Liang YAN, Xian-Chun XIA, Yong ZHANG, Zhong-Hu HE

Acta Agronomica Sinica. 2018, 44(02):  260-267.  doi:10.3724/SP.J.1006.2018.00260

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The knowledge on relationship between grain weight and grain-filling parameters is important for yield potential and stability improvement of common wheat. Logistic equation was used for fitting the grain-filling dataset from 14 leading cultivars and advanced lines, sown at Anyang, Henan province in three successive seasons from 2012 to 2015. The results showed that grain weight and all grain-filling rate (GFR) related parameters were mainly influenced by genotype, while grain-filling period related parameters were mainly influenced by environment. There was significant difference on all GFR parameters including the average and the highest GFR, and those in the three periods among cultivar groups based on grain weight, showing a trend of high-grain-weight cultivar > medium-grain-weight cultivar > low-grain-weight cultivar, whereas there was no significant difference for grain-filling period related parameters among the cultivar groups. GFR, especially in the fast increase period, was the major factor that made the significant difference of grain weight among cultivars. Positive correlations between grain weight and all GFR related parameters were observed (P < 0.001), with the coefficients of 0.97 for GFR in the fast increase period and 0.90 for average GFR, whereas no significant correlations were found between grain weight and grain-filling period related parameters. Therefore, average GFR was proposed to be used in quantitative trait loci mapping to improve grain weight of wheat in the Yellow and Huai Rivers Valley.

Superimposition Effect of Film-mulching and Furrow Ridging Culture on Maize Grain Yield and WUE in Loess Plateau

Jun-Hong XIE, Ling-Ling LI, Ren-Zhi ZHANG, Qiang CHAI

Acta Agronomica Sinica. 2018, 44(02):  268-277.  doi:10.3724/SP.J.1006.2018.00268

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A three-year continuous maize cropping study was conducted to compare the effect of different planting treatments on water use efficiency (WUE) and grain yield of maize in a semi-arid environment in the western Loess Plateau of China. The experiment was arranged in a randomized block design with three replicates. The treatments included flat-planting without mulching (NFM), flat-planting with half plastic film mulching (HFM), flat-planting with complete plastic film mulching (CFM) and furrow-planting with plastic film completely mulched narrow and wide alternative ridges (CFRM). CFRM treatment had a superimposition effect, increasing maize grain yield by 2282.9, 2460.2, and 2765.5 kg ha^-1, with the increasing ratio of 32.3%, 49.8%, and 46.5%, compared with HFM treatment in the three continuous cropping years. In addition, the contribution rate to grain yield complete film mulching was 59.3%, 90.3%, and 20.9%, and by furrow-ridging culture was 40.7%, 9.7%, and 79.1%, respectively. The complete film mulching had greater contribution to yield than ridging and furrowing culture in the first and second years, and vice versa in the third year. The water use efficiency was the highest in CFRM treatment throughout the three years, with an incremental from 10.6% to 25.2%, in comparison to HFM. Under the same precipitation conditions, CFRM and CFM treatments had higher soil water storage before maize sowing than NFM, increasing from 6.3% to 15.1% and from 3.5% to 11.5%, respectively. However, CFRM and CFM treatments had lower soil water storage than NFM after maize harvest, with a decrease from 6.0% to 12.9% and from 4.7% to 12.9% in the second and third years, respectively. The soil water storage declined with continuous cropping of maize at harvesting stage in the second and third years, showing decrease of 37.1% and 44.0% for Soil water storage of CFRM, 35.5% and 37.1% for CFM, respectively. In particular, the soil desiccation phenomenon was appeared in 50 to 200 cm soil layer of CFRM treatment in the second year, and other treatments in the third year. In conclusion, CFRM is the best option for efficient water use and increasing grain yield, which is attributed to higher water demand, that leads to soil desiccation.

Effects of Planting Density on the Mechanical Harvesting Characteristics of Semi-winter Rapeseed

Xiao-Yong LI, Min ZHOU, Tao WANG, Lan ZHANG, Guang-Sheng ZHOU, Jie KUAI

Acta Agronomica Sinica. 2018, 44(02):  278-287.  doi:10.3724/SP.J.1006.2018.00278

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Two canola varieties (Zhongshuang 11 and Huayouza 9) with four planting densities (15 × 10⁴, 30 × 10⁴, 45 × 10⁴, and 60 × 10⁴ plants ha^-1) were used to evaluate their effects on yield, lodging and pod shattering resistance index (PSRI). With the increase of plant density, effective pods per hectare increased, resulting in increasing yield. The highest yield was observed at density of 45 × 10⁴ plants ha^-1 for both of the two varieties. With the increase of plant density, the root crown diameter decreased which led lodging index to be increased. Under the densities of 15 × 10⁴ and 30 × 10⁴ plants ha^-1, the part of stem below canopy had the highest lodging index, while under the densities of 30 × 10⁴ and 45 × 10⁴ plants ha^-1, the central of stem and the upper part of middle stem had the highest lodging index, indicating that the lodging region was lower than under low plant density. The PSRI of branches was smaller than that of main stems, with a tendency of increasing firstly and then decreasing with decreasing branch height. The PSRI of main stem of the two varieties had different responses to increasing density, that was decreasing in Zhongshuang 11 while increasing firstly and then decreasing in Huayouza 9, with a highest PSRI under 300 000 plants ha^-1. The water declining rate of pod wall from early pod development to pod maturity had highly significant and negative correlation with pod shattering resistance, indicating that this index is most important for density effects on pod shattering.

Effect of Low Temperature in Spring on Yield and Photosynthetic Characteristics of Wheat

Rui-Xia WANG, Chang-Sheng YAN, Xiu-Ying ZHANG, Guo-Zhong SUN, Zhao-Guo QIAN, Xiao-Lei QI, Qiu-Huan MOU, Shi-He XIAO

Acta Agronomica Sinica. 2018, 44(02):  288-296.  doi:10.3724/SP.J.1006.2018.00288

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Low temperature (LT) stress in spring occurs frequently in the Huang-Huai Rivers Valley, resulting in yield loss of wheat. The objectives of this study were to understand the physiological responses of wheat cultivars to LT and determine suitable physiological indicator(s) for cold-tolerance selection. Three cultivars, Taishan 6426, Taishan 4033, and Jimai 22, were exposed to LT stress at standing, jointing and booting stages, and the yield-related traits, photosynthetic parameters as well as leaf cell structure were compared among different cultivars. The agronomic traits of different cultivars changed in similar trends after LT treatment with the consistent result across years. Plant height received small influence of LT, especially LT at standing stage. In contrast, spike number per plant decreased significantly compared with the control (normal temperature), but the reduced percentage varied across years. Grain number per spike and yield per plant showed significantly declined trends with delaying LT stress, and the maximum decrements were observed in the treatment of LT at booting stage. The grain number per spike was 90.5%-93.3% (2012-2013) and 91.9%-93.6% (2013-2014) lower, and the yield per plant was 87.9%-97.3% (2012-2013) and 91.5%-97.8% (2013-2014) lower in LT treatment at booting than in the control. Booting stage was secondly sensitive to LT in yield, whereas jointing stage was less influenced by LT. Grain yield loss under LT stress mainly resulted from the decrease of grain number per spike. Under LT at jointing or booting stage, the chlorophyll content decreased in the three cultivars, but the decrement varied across cultivars. Moreover, the photosynthetic rate, transpiration rate and stomata conductance decreased significantly and the intercellular CO₂ concentration increased greatly in the three cultivars, and those in Taishan 6426 had the minimum variations. LT also had inhibition in chlorophyll fluorescence parameters of wheat. For example, the F_v/F_m value was significantly lower in the treatment of LT at jointing or booting stage than in the control except for Taishan 6426. When exposed to LT stress, leaf epidermic cells were severely damaged, showing their loose arrangement and irregular structures of guard cell and accessory cell. Our results indicate that photosynthetic rate, transpiration rate, stomata conductance, intercellular CO₂ concentration and F_v/F_m can be used as indicators to identify tolerance of wheat cultivars to spring coldness.

Homologous Cloning of BnGS3 and BnGhd7 Genes in Brassica napus and Their Relationship with Rapeseed Yield-related Traits

Zhi-Fei XUE, Xia WANG, Fu-Peng LI, Chao-Zhi MA

Acta Agronomica Sinica. 2018, 44(02):  297-305.  doi:10.3724/SP.J.1006.2018.00297

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Brassica napus is an allotetraploid with complex genomic structure, but Brassica genome has a collinearity with that of rice. In this study, the homologous genes BnGS3 and BnGhd7 of Brassica napus were obtained by homologous cloning of the yield related genes GS3 and Ghd7 of rice. BnGS3 has six exons with a 666 bp of ORF and encodes 222 amino acids. BnGS3 protein has VWF structure, one of the four conserved domains of rice GS3, and belongs to type A. BnGhd7 contains one exon having ORF with a full-length of 1014 bp and encoding 337 amino acids. BnGhd7 protein has two important domains, the N-terminal B-Box and the C-terminal CCT. BnGS3 and BnGhd7 were located in linkage groups A2 and A10, respectively. Polymorphism markers brgs-16 of BnGS3 and polymorphism markers brghd-3 and ghd7-7 of BnGhd7 were obtained by comparative sequencing, among which brghd-3 with thousand kernel weight (P < 0.05) and ghd7-7 with plant height (P <0.01) were positively correlated, and ghd7-7 was negatively correlated with flowering stage (P < 0.05). The results indicate that it is feasible to clone the homologous genes of Brassica napus using rice functional gene sequence information, which provides an effective way in Brassica napus functional gene research.

Analysis of Brown Rust Resistance Inheritance Based on Field Phenotypes and Detection of Bru1 Gene in Sugarcane

Zhu LI, Li-Ping XU, Ya-Chun SU, Qi-Bin WU, Wei CHENG, Ting-Ting SUN, Shi-Wu GAO

Acta Agronomica Sinica. 2018, 44(02):  306-312.  doi:10.3724/SP.J.1006.2018.00306

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With characteristics of high pathogenic spore yield and strong popularity, sugarcane brown rust caused by Puccinia melanocephala leads to a serious loss in sugarcane yield and sucrose content. An understanding of the inheritance of brown rust resistance will contribute to parent selections and combination arrangements, while an efficient technique for resistance identification is necessary for selection of segregated individuals. Combination phenotypic survey with Bru1 gene detection, the segregated population derived from crossing combinations with different brown rust resistances was used to explore rust resistance inheritance and evaluate the efficiency of Bru1 gene detection. The undetected rate of Bru1 gene in the individuals with rust sensitivity at the stage of prosperous epidemic peak was 96.7%, while the detected rate in all uninfected individuals was only 66.0% in spite of two from four combinations showed 100.0% in resistant individuals. It indicates the disease sensitivity and resistance can be estimated based on the detection of Bru1 gene in the genetic background with rust resistance regulated by Bru1. In addition, none of the healthy individuals in the segregated population derived from combination of CP84-1198 × Yunzhe 89-7 have Bru1 gene been detected, suggesting the new resistance genes, different from Bru1, are present in sugarcane gene pool. In addition, both maternal and paternal components affected the rust susceptibility of their offspring, but male parent other than female parent tended to transmit a higher frequency of rust-susceptible genes.