Table of Content

12 December 2015, Volume 41 Issue 12

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CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Development and Application of a Functional Marker of the Blast Resistance Gene Pi35 in Rice

MA Jian**,MA Xiao-Ding,ZHAO Zhi-Chao,WANG Shuai,WANG Jiu-Lin,WANG Jie,CHENG Zhi-Jun,LEI Cai-Lin

Acta Agron Sin. 2015, 41(12):  1779-1790.  doi:10.3724/SP.J.1006.2015.01779

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Rice blast is one of the most destructive diseases, and breeding resistant cultivars is considered to be the most economical and effective strategy to control this disease. The Pi35 gene shows partial resistance to leaf blast and has been used as a broad-spectrum and durable resistance source in rice breeding programs in Japan. However, its distribution is not clear in Chinese rice germplasm and cultivars. For the purpose to facilitate the application of Pi35 in rice breeding programs in China, we compared the coding sequences of Pi35 alleles in multiple resistant and susceptible rice cultivars, found a specific nucleotide 3780T which was only present in the functional resistance allele of Pi35, and further developed a Pi35 functional marker (Pi35-dCAPS). Among 281 rice accessions including 10 Fukei 138-derived japonica cultivars, 67 leading cultivars, and 204 accessions of rice mini-core collection of Chinese germplasm, five Fukei 138-derived cultivars (Kenjiandao 3, Kenjiandao 6, Kendao 8, Suijing 3, and Longjing 34) and two mini-core accessions (japonica cv. Funingzipijingzi and indica cv. Ximaxian) were detected to possess the intact Pi35 gene by using the Pi35-dCAPS marker in combination with the genomic sequencing of Pi35. These results will greatly facilitate the utilization of Pi35 in rice breeding programs by marker-assisted selection.

Comparison of Pathogenicity of Pyricularia oryzae under Different Genetic Backgrounds

MA Jun-Tao,ZHANG Guo-Min,XIN Ai-Hua,ZHANG Li-Yan1,DENG Ling-Wei1,WANG Yong-Li,WANG Ying,REN Yang,GONG Xiu-Jie,GE Xuan-Liang,YANG Xiu-Feng

Acta Agron Sin. 2015, 41(12):  1791-1801.  doi:10.3724/SP.J.1006.2015.01791

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Rice blast is one of the most serious rice diseases in Heilongjiang province, resulting in high incidence and yield reduction. In order to definite the pathogenicity of P. oryzae isolates and resistance improvement of nurse varieties under different genetic backgrounds, the experiment was conducted using four groups of Pyricularia oryzae (P. oryzae) isolates and rice varieties including Chinese differential varieties, Japanese differential varieties, monogenic rice lines and landrace. Using the method of spraying inoculation and associational resistance and gene pyramiding analyses, the main results were as follows: (1) Under the Chinese differential varieties system, the P. oryzae isolates from Kuiku 131, Kendao 12, Shangyu 397, and Ha 9811 were divided into ten, six, six, and nine physiological races respectively, and predominant physiological race of P. oryzae isolates from Ha 9811 was ZF1 while the predominant physiological races of the other three groups of P. oryzae isolates were all ZG1. (2) Under the Japanese differential varieties system, the P. oryzae isolates from Kuiku 131, Kendao 12, Shangyu 397, and Ha 9811 were divided into 19, 11, 13, and 14 physiological races respectively, furthermore, the average disease incidence was 54.17%, 46.21%, 41.67%, and 59.90%, respectively. (3), Under the monogenic rice lines system, the P. oryzae isolates from Kuiku 131, Kendao 12, Shangyu 397 and Ha 9811 were divided into 20, 11, 12, and 16 pathogenic types respectively, additionally, their similarity coefficient of pathogenicity was 0.20–0.87, 0.25–0.90, 0.25–1.00, and 0.31–0.88, respectively. (4) Under the landrace system, the P. oryzae isolates from Kuiku 131, Kendao 12, Shangyu 397, and Ha 9811 were divided intotwelve, sever, nine and thirteen pathogenic types respectively, with the best blast-resistance varieties of Longdun 104, Songjing 6, Songjing 9, and Longdao 7. (5) Using the method of associational resistance, the average associational resistance coefficient and associational pathogenicity coefficient were 0.71–0.92 and 0–0.08, respectively; Using the method of gene pyramiding, the number of immunity gene combination to the P. oryzae isolates from Kuiku 131, Kendao 12, Shangyu 397, and Ha 9811 were two, two, five and seven. In conclusion, using monogenic rice lines to research the pathogenicity of P. oryzae is better than using other appraisal systems. And good effects can be get from two resistance improvement methods, but both of them have their advantages and disadvantages.

Cloning and Expression Analysis of Tolerance to Aluminum-toxicity Candidate Gene GmSTOP1 in Soybean

CONG Ya-Hui,WANG Ting-Ting,LIU Ju-Ge,WANG Ning,GAO Meng-Meng,LI Yan,GAI Jun-Yi

Acta Agron Sin. 2015, 41(12):  1802-1809.  doi:10.3724/SP.J.1006.2015.01802

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Aluminum toxicity is one of the major factors that limits the growth and production of crops in acid soils. AtSTOP1 transcription factors can regulate the expression of genes related to aluminum-toxicity tolerance mechanisms, which plays an important role in aluminum-toxicity tolerance in Arabidopsis. To study the expression features of the STOP1-like gene in soybean, we cloned a STOP1 gene located on chromosome 16 from the aluminum-toxicity tolerant soybean cultivar (Kefeng-1) using RT-PCR, and designated as GmSTOP1. The length of GmSTOP1 coding DNA sequence was 1566 bp, which encoded 521 amino acid residues. Diverse cis-acting promoter elements involved in hormone, heat and stress responses were discovered in the 1500 bp upstream region of GmSTOP1, such as ABRE, HSE, TC-rich repeats, and other elements. Protein structure prediction showed that it did not have any signal-peptide or transmembrane region, but contained four conservative Cys-2-His-2 zinc-finger domains. Phylogenetic analysis demonstrated that GmSTOP1 was similar to the putative STOP1-like protein from Phaseolus vulgaris. Results of subcellular localization showed that GmSTOP1 protein is located in the cell nucleus. The transcripts of GmSTOP1 were detected in all organs tested including root, shoot apical meristem, stem, leaf, flower, pod and seed, with the highest level in seed. GmSTOP1 was up-regulated in soybean roots by 25 μmol L^–1 AlCl₃ treatment, and reached the highest relative expression level at 24 hours, which was about 9.2 times of the level in control (0 μmol L^–1 AlCl₃). In addition, Real-time PCR analysis showed that the expression of GmSTOP1 in soybean leaf and root was also up-regulated by ABA, NaCl, and PEG, respectively. These results indicated that GmSTOP1 might participate in soybean response to abiotic stresses including aluminum-toxicity, high salinity and osmosis stress, which provides the basis for further studying the functions of GmSTOP1.

Cloning and Characterization of a Novel Gene Encoding Proline-Rich Protein in Sesame

Lü Gao-Qiang,WU Xiang-Yang,WANG Xin-Yu

Acta Agron Sin. 2015, 41(12):  1810-1818.  doi:10.3724/SP.J.1006.2015.01810

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Bacterial wilt of sesame is a major threat in sesame production in south China, resulting seriously in yield and quality losses. The disease is caused by bacterial pathogen Ralstonia solanacearum. This study profiled the gene expression of sesame inoculated with Ralstonia solanacearum by using fifty random primers. A gene (fragment) was found to be drastically down regulated by the pathogen. The gene fragment was cloned and sequenced. Using the sequence as queries, the sesame genome database (http://www.ncbi.nlm.nih.gov/) was searched and the corresponding DNA sequence containing a complete ORF was obtained. The full-length of the gene shows that its encoding region is 1458 bp, encoding a putative protein of 486 amino acids. The protein is rich in proline on its N-terminus, and has several repeat sequences (motifs) rich in proline, suggesting that it belongs to proline-rich protein (PRP) family. The protein was named as SiPRP (Sesaumu indicunm Proline-rich Protein). The encoding region of SiPRP was further amplified in sesame cDNAs, sequencing analysis demonstrated that it has the same sequence with the predicted one. Blast analysis revealed that the protein has the lower homology with other plant PRPs, and has new types of proline-rich motifs, suggesting that SiPRP is a new member in PRP family. Semi quantitative RT-PCR and qPCR with newly designed gene-specific primers verified that SiPRP expression was drastically down regulated upon pathogen infection. Previous studies showed that most plant PRPs were located on plant cell wall, however, transient expression in onion epidermal cells showed that SiPRP-YFP fusion protein was located on cell membrane, with a bit secreted outside the cell. Transient expression in tobacco cells revealed that SiPRP protein might be located on special structures of the membrane. SiPRP protein identified in this study may play pivotal roles in Ralstonia solanacearum-sesame interactions.

Cloning and Function Analysis of Pathogenesis Related Protein Gene HaPR1 from Sunflower (Helianthus annuus)

MA Li-Gong,ZHANG Yun-Hua,MENG Qing-Lin,SHI Feng-Mei,LIU Jia,LI Yi-Chu,WANG Zhi-Ying

Acta Agron Sin. 2015, 41(12):  1819-1827.  doi:10.3724/SP.J.1006.2015.01819

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Pathogenesis-related proteins are commonly used as markers of plant defense responses. The full-length cDNA of pathogenesis-related protein 1 (PR1) named HaPR1 in Helianthus annuus was cloned based on the transcriptome of H.annuus induced by Sclerotinia sclerotiorum, and its expression model and function were analyzed in this study. Sequence analysis showed that the cDNA of HaPR1 (GenBank No. KR071874) contained a 489 bp ORF encoding a protein of 162 amino acids residues with the molecular mass of 17.52 kD and theoretical pI of 8.19, HaPR1 possessed six conserved cysteine and four conserved allergen V5/Tpx-1 related domain. The HaPR1 was highly homologous with PR1 in other species. Real-time PCR analysis showed that expression level of HaPR1 was the highest in leaf, and was significantly induced by drought, salt stress, oxalic acid, S. sclerotiorum and its metabolites. Then the HaPR1 gene was transformed into tobacco by Agrobacterium tumefaciens to further verify its function. The results showed that the expression of HaPR1 improved the resistance of transgenic lines, and significantly increased SOD, POD, and CAT activities and reduced the content of MDA. It suggested that HaPR1 has a function of resistance to S. sclerotiorum.

Genetic Diversity and Association Analysis of Protein Content in Weak Gluten Wheat Ningmai 9 and Its Derived Lines

JIANG Peng,ZHANG Ping-Ping,ZHANG Xu,CHEN Xiao-Ling,YAO Jin-Bao,MA Hong-Xiang

Acta Agron Sin. 2015, 41(12):  1828-1835.  doi:10.3724/SP.J.1006.2015.01828

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Ningmai 9 is an elite weak gluten wheat cultivar and an important breeding parent in the south area of Huai River Valley, and 15 new cultivars have been developed and released from Ningmai 9. This study aimed at dissecting the genetic mechanism and inheritance of protein content in Ningmai 9 and its derivatives. The kernel protein content (KPC) and flour protein content (FPC) of Ningmai 9 and its 117 derivatives were evaluated in the 2009–2010 and 2010–2011 growing seasons and the QTLs associated with KPC and FPC were identified by whole genomes screening with 185 SSR markers. The genetic similarity index ranged from 0.55 to 0.88 among Ningmai 9 and its derivatives. In the Neighbor-Joining cluster tree, Ningmai 9 was clustered with most first-generation lines first, then with the second-generation lines, and Yangfumai 4 of first-generation derivative was the last one to incorporate in. The first- and second-generation derivatives inherited 75.60% and 67.81% of Ningmai 9 alleles, respectively. Great variations of KPC and FPC were observed in the Ningmai 9 derived lines with the variation coefficients ranging from 5.07% to 7.28%. Six and five QTLs were identified to be associated with KPC and FPC, respectively, of which three and two were stably detected in both years. One QTL was associated with both KPC and FPC. Three stable QTLs, Xgwm539, Xwmc397, and Xwmc468, had negative effects on KPC or FPC in Ningmai 9 and might be used for quality improvement in weak-gluten wheat breeding.

Technical System of Hybrid Seed Production with Perennial Plants of Cotton Sterile Lines

ZHANG Xiao-Jun,YUE Fu-Liang,ZHANG Xiao-Hong,HOU Rui,ZHANG Xiang-Qiong,LI Wen-Jun

Acta Agron Sin. 2015, 41(12):  1836-1843.  doi:10.3724/SP.J.1006.2015.01836

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It is hard to separate maintainer line and sterile line in two-line-system hybrid breeding, so half of the fertile plants derived from maternal line should be pulled out at bud stage, which increases the cost of seed production and the risk of hybrid seed purity. In this research, taking advantage of specific weather conditions of warm winter and dry winter-spring season in the mid-subtropical zone, we explored hybrid seed production with overwintered perennial sterile plants after eliminating the 50% fertile plants from the nuclear sterile line in the first year. From 2006 to 2011, we investigated various factors that might influence hybrid seed production with perennial cotton sterile plants, including different ages of perennial root, winter-season intercropping of rapid cycling vegetables, pruning times and pruning methods. The results indicated that the perennial plants had extended growth period , its reproductive growth stunted 10 days earlier than that of seedlings with corresponding sowing time, its boll number per plant was significantly higher, while boll weight was slightly lower. The hyrid seed yield in first- and second-year perennial plants was 10.3% to 5.9% higher than that in one year plants. The yield showed non-significant reduction in the third year of prennial production, but significantly reduced by 9.4% to 14.0% in the fourth to fifth years. With the increase of overwintering years, the old root at the basal portion of the plant showed obvious malformation. Within the first five years, the death rate of perennial plants had no relationship with ages of perennial root and field types, but was related to soil water content and pruning methods. The best way for perennial root onverwintering was: no intercropping between winter cotton lines and othen crops, no pruning, and leaving the cotton plants in the field for natural overwintering. In the next year, the main stem and early regenerated buds should be pruned at 10 cm above the ground before the rainy season or the first irrigation, then one or two regenerated primary buds should be reserved with water and nutrition managements.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Effects of Brassinosteroids (BRs) on Photosynthetic Matter, Nitrogen Accumulation and Use Efficiency during Grain Filling Stage of Hybrid Japonica

TIAN Xiao-Ya,LIU Xin,WANG Qiang-Sheng,JIANG Qi,FENG Jin-Xia,ZHANG Hui,DING Yan-Feng

Acta Agron Sin. 2015, 41(12):  1844-1857.  doi:10.3724/SP.J.1006.2015.01844

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Taking the conventional japonica hybrid rice Changyou 3 and indica-japonica super hybrid rice Yongyou 12 as materials, the experiment analyzed the effects of Brassinosteroids (BRs) on photosynthetic characteristics, dry matter accumulation, nitrogen absorption and utilization, non-structural carbohydrates (NSC) accumulation and the NSC/N ratio of different plant organs during grain filling stage. Results showed that the effect of BRs on photosynthetic indexes presented as G_s>T_r>P_n>C_i. Spraying 2,4-epibrassinolide (eBL) could enhance net photosynthetic rate (P_n) and transpiration rate (T_r), maintain chlorophyll content and intercellular CO₂ concentration (C_i), and eventually improve the leaves’ photosynthetic capacity during grain filling stage. It could also increase the amounts of dry matter, nitrogen and NSC accumulation, the proportions and rates of dry matter accumulation, nitrogen absorption and NSC transportation, but reduce the dry matter production efficiency of nitrogen nutrition. The effect of Brz was on the contrary. Spraying eBL improved amounts of the dry matter, NSC, nitrogen and the contribution rate to grains made by nitrogen of the two rice varieties, reduced the contribution rate to grains made by dry matters and NSC after flowering. However, Brassinazole (Brz) decreased transfer amounts and rates of the dry matter, NSC and nitrogen, promoted the contribution rate to grains made by dry matters and NSC. The transfer amounts of NSC and nitrogen of different organs in shoot of the two hybrid rice varieties were shown as eBL>CK>Brz, and early stage of grain filling (EGF) > late stage of grain filling (LGF). The NSC/N of different organs in shoot of the two rice varieties showed an increasing tendency with filling, among which the changes in stem-sheath and panicle were the most significant. Spraying eBL decreased the NSC/N of stem-sheath and leaf, Spraying Brz promoted it, while the effects of BRs on panicle was not clear. Yongyou 12 had a stronger net photosynthetic rate in flag leaves, greater accumulations of dry matter, NSC and nitrogen, larger transfer amounts of NSC and nitrogen in early stage of grain filling, and finally its actual yield was 5.03%-9.32% higher than that of Changyou 3. Spraying eBL showed a diverse rule on the accumulations of dry matter, nitrogen and NSC transportation of the two rice varieties. The inhibiting effect of Brz on dry matter and nitrogen accumulations and NSC transferring was stronger in Yongyou 12 than that of Changyou 3.

Panicle Traits and Grain-filling Characteristics of Japonica/Indica Hybrid Super Rice Yongyou 538

WEI Huan-He,MENG Tian-Yao,LI Chao1,ZHANG Hong-Cheng,SHI Tian-Yu,MA Rong-Rong,WANG Xiao-Yan,YANG Jun-Wen,DAI Qi-Gen,HUO Zhong-Yang,XU Ke,WEI Hai-Yan,GUO Bao-Wei

Acta Agron Sin. 2015, 41(12):  1858-1869.  doi:10.3724/SP.J.1006.2015.01858

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A field experiment was conducted using indica-japonica rice Yongyou 538 as the material, conventional japonica rice Zhendao 18, and hybrid indica rice Zhongzheyou 1 as the check. The panicle was separated into six parts, i.e. upper primary branches (UP), upper secondary branches (US), middle primary branches (MP), middle secondary branches (MS), low primary branches (LP), and low secondary branches (LS). We compared the differences in panicle traits and grain-filling characteristics of different cultivars of rice types. The main results were as follows: (1) Yongyou 538 had an average yield of 12.5 t ha^-1 across two years, which was 17.6% and 15.2% higher than that of Zhongzheyou 1 and Zhendao 18, respectively, Yongyou 538 also had the highest spikelets per panicle and total spikelets among the three varieties. (2) Yongyou 538 had higher grain weight per panicle and grain density, as well as higher number of grains in the six corresponding parts of panicle compared with Zhongzheyou 1 and Zhendao 18, especially in the upper secondary branches and the middle secondary branches of panicle. (3) For Yongyou 538, grain-filling processes were synchronous types between UP and MP, US and MS, and LP and LS, but were asynchronous types between UP and MP, US and MS, and LP and LS. For Zhongzheyou 1 and Zhendao 18, grain-filling processes of UP, US, and MP were synchronous types, while asynchronous types existed between UP, US, MP and LP, LS. Among the varieties, the mean final weight of a kernel in the six parts of the panicle in Zhendao18 was the highest, mean value of maximum grain-filling rate and mean grain-filling rate showed Zhongzheyou 1>Zhendao 18>Yongyou 538, while effective grain-filling period showed Yongyou 538>Zhendao 18>Zhongzheyou 1

Effects of Ethylene-Chlormequat-Potassium on Leaf Nitrogen Assimilation after Anthesis and Early Senescence under Different Planting Densities

LU Lin,DONG Zhi-Qiang,DONG Xue-Rui,JIAO Liu,LI Guang-Yan,GAO Jiao

Acta Agron Sin. 2015, 41(12):  1870-1879.  doi:10.3724/SP.J.1006.2015.01870

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To explore the effects of ethylene-chlormequat-potassium (ECK) on the physiological mechanisms of nitrogen assimilation and early senescence in summer maize, and provide a theoretical basis for high and stable yields of summer maize under high plant density by chemical regulation technology in North China Plain, we conducted a field experiment using two varieties of Zhongdan909 and Xundan20 with different planting densities in 2013 and 2014. The results showed that increasing plant density significantly decreased the activities of nitrate reductase (NR) and glutamine synthetase (GS) after anthesis, glutamate oxaloacetic transaminase (GOT) activity at anthesis, and glutamate pyruvate transaminase (GPT) activity at 30 days after anthesis. The soluble protein and free amino acid contents at 20 days after anthesis, and the SPAD value at 10 days after anthesis were significantly decreased with increasing plant density. For both varieties, grain yield reached the highest under 7.5×10⁴ plants ha^-1, while decreased under the density of ≥7.5×10⁴ plants ha^-1. The higher density resulted in early senescence. ECK treatment significantly increased the activities of NR, GS, and contents of free amino acid, soluble protein and SPAD value during middle and late grain filling stages. ECK treatment also significantly improved the GOT and GPT activities under 7.5×10⁴−10.5×10⁴ plants ha^-1. Under the density ≥ 7.5×10⁴ plant ha^-1, the yields of Zhongdan 909 and Xundan 20 compared with their own control were respectively increased by 5.59%−6.63% and 6.73%−8.10%. ECK treatment significantly increased the nitrogen assimilation key enzyme activity of ear leaf and its product content under different planting densities, promoted normal nitrogen assimilation and prevented early senescence under higher planting densities, therefore increased yield. Thus, an appropriate planting density combined with ECK application could be an important technique for achieving high grain yield for summer maize production in North China Plain.

Photosynthetic Characteristics after Flowering and Contribution of Non-leaf Green Organs of Cotton to Yield under Mulching-drip Irrigation with Water Deficiency

ZHAN Dong-Xia,ZHANG Chao,ZHANG Ya-Li,LUO Hong-Hai,GOU Ling,ZHANG Wang-Feng

Acta Agron Sin. 2015, 41(12):  1880-1887.  doi:10.3724/SP.J.1006.2015.01880

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Leaf is one of the main photosynthetic organs, while other green parts of plant also retain or develop chlorophyll and have photosynthesis. To better understand the whole plant photosynthesis production potential and contribution to cotton yield, we selected Xinluzao 33 and Xinluzao 45 (two common cultivars in Northern Xinjiang) with three irrigation treatments (CI, conventional irrigation; SDI, slight deficit irrigation; MDI, moderate deficit irrigation) to measure the chlorophyll content (Chl), net photosynthetic rate (P_n), stomatal conductance (G_s) and photosynthate accumulation in leaf and non-leaf green organs during different growth stages and the contribution of non-leaf green organs to yield. The results showed that the P_n and Chl in non-leaf organs were relatively insensitive to soil moisture stress, decreasing by only a small amount between 25 and 45 days after anthesis. With reduction of water supply, the dry matter production in non-leaf green organs played more important roles in cotton yield formation. Cotton boll weight in the moderate deficit irrigation treatment decreased by 16.8% to 34.9% when the bolls (capsule walls plus bracts) were shaded and by 7.6% to 17.5% when the stalks were shaded. Hence, limiting-irrigation treatment is important to maintain high leaf photosynthetic rates. It is also important to develop the potential photosynthetic capacity of non-leaf green organs. This is especially important when leaf photosynthesis capacity declines due to leaf aging or water stress.

Spatiotemporal Pattern of Potassium Deficiency Symptoms and K⁺ Concentration in Cotton Leaf

CHEN Qiao,TIAN Xiao-Li,YAN Wei,WANG Ning

Acta Agron Sin. 2015, 41(12):  1888-1898.  doi:10.3724/SP.J.1006.2015.01888

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In order to explore the physiological mechanism of an unusual phenomenon that potassium (K) deficiency symptom first occurs in medium and upper leaves rather than lower leaves of cotton plants, field experiments were conducted at Shangzhuang experimental station of China Agricultural University with a low K soil (64.0 to 70.9 mg kg^–1 of available K) in Beijing (40º08′N, 116º10′E) during 2013 and 2014 growing season, using CCRI 41 (Gossypium hirsutum L.; susceptible to K deficiency) as material. There were three potassium treatments: control (no potassium applied), low potassium (225 kg K₂O hm^–2) and high potassium (375 kg K₂O hm^–2).We observed potassium deficiency symptoms of the main stem leaves from squaring stage to late stage of flowering and boll period and determined the content of K ⁺ of blade. It was found that K deficiency symptoms developed upward from the leaf located at the tenth node or so of mainstem, and those leaves below this node did not show symptoms during the whole season. However, this type of upward development of K deficiency symptoms was not successive, some leaves at medium part of mainstem (the 16th node or so) were always normal or near normal. There was no necessary link between the pattern of K deficiency symptoms and K⁺ concentration in cotton leaves. The latter generally increased with the leaf position raised from bottom to top, which is in accord with the common pattern under K deficiency. However, the increased magnitude from bottom to top and the leaf position with a larger increase in K⁺ concentration were different at contrasting growth stages, as well as between 2013 and 2014. The K⁺ concentration in most leaves decreased faster or slower over time. Nevertheless, some young or functional leaves (e.g. from the 7th to 14th node in 2013, and from the 13th to 16th node in 2014) showed an increase of K⁺ concentration during the period from squaring stage to peak blooming stage. In conclusion, the spatiotemporal pattern of K deficiency symptoms in cotton leaves is more complicated than expected; and according to K⁺ concentration in leaves we cannot explain it well. The further study should focus on the susceptibility to K deficiency in leaves at different positions, and K⁺ redistribution in whole plant.

RESEARCH ACTIVITIES

Genetic Analysis on Dwarfing Trait in Landrace Ailanmai of Triticum turgidum L. ssp. turgidum

ZHOU Qiang,YUAN Zhong-Wei,ZHANG Lian-Quan,NING Shun-Zong,REN Yong,TAO Jun,LI Sheng-Rong,LIU Deng-Cai

Acta Agron Sin. 2015, 41(12):  1899-1905.  doi:10.3724/SP.J.1006.2015.01899

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Ailanmai is an important Triticum turgidum ssp. turgidum landrace carrying dwarf gene in China. Its dwarfing trait was found to be sensitive to gibberellic acid. In 2012, we crossed Ailanmai with two high plant landraces, Qinkemai and Ganmai, and obtained their reciprocal F₁ hybrids. The genetic analysis was carried out in Mianyang, Sichuan Province using the F₁, F₂, and F_2:3 populations during the 2012–2013 crop seasons. One recessive gene proved to control the dwarfing trait in Ailanmai. Polymorphic simple sequence repeat (SSR) primers associated with plant height were selected through bulked segregant analysis (BSA) and used to identify the F₂ individuals. The results indicated that the dwarf gene was located on the short arm of chromosome 7A with a genetic distance of 2.5 cM from marker GWM471. We speculated Rht22 to be the dwarf gene in Ailanmai because the reciprocal F₁ and F₂ hybrids between Ailanmai and Aiganfanmai (carrying Rht22) exhibited similar distributions in plant height. This speculation was validated with high-through molecular marker analysis. The percentages of identical SNP and DArT markers between Ailanmai and Aiganfanmai were as high as 98.7% and 99.3%, respectively. We conclude that the two landraces might be the same variety a long time ago and became synonymic during their spread accompanying with humanity activities. The dwarf gene in Ailanmai had a moderate or weak effect to reduce plant height in synthetic hexaploid wheat. Thus, it should be utilized by pyramiding other dwarfing genes in wheat dwarfing breeding.

RESEARCH NOTES

Effects of Sowing Time on Spring Maize (Zea mays L.) Growth and Water Use Efficiency in Rainfed Dryland

LU Hai-Dong,XUE Ji-Quan,HAO Yin-Chuan,ZHANG Ren-He,GAO Jie

Acta Agron Sin. 2015, 41(12):  1906-1914.  doi:10.3724/SP.J.1006.2015.01906

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To solve the problem of incomplete and irregular maize seeding growth and low and unstable yield in the semiarid region of Weibei Shaanxi Province, we designed six sowing times to study their impact on spring maize growth and development,, dry matter production, grain yield, water use efficiency and environmental factors. The results showed that maize growth period was shortened with postponing sowing time, the vegetative growth stage and the overlapping stage of vegetative and reproductive growth had the variations from 2 to 19 days. But reproductive growth stage was relatively stable, with the change from –3 to 5 days. In a certain range of time, dry matter production per plant in different sowing treatments was not obvious different, however, dry matter accumulation in spikes after flowering, yield and water use efficiency in treatments with appropriate sowing time were 4.0%–23.6%, 3.9%–24.5% and 6.6%–14.5% higher respectively, than these with early sowing time or delayed sowing time, resulting from the changed soil water content by adjusting the sowing date. Yield was highly correlated with soil moisture content in a certain sowing date, rainfall before flowering, effective accumulated temperature after flowering and sunshine hours after flowering. Thousand grain weight was highly correlated with sunshine hours after flowering. In the treatments with early sowing time, the main factor affecting maize yield was the poor soil moisture content that caused less low effective panicle in unit area and low emergence rate. In the treatment with later sowing time, the main factors affecting yield were the decreased effective accumulated temperature and sunshine hours during the reproductive growth stage, resulting in less dry matter accumulation after flowering and lower thousand grain weight. In the treatment with suitable sowing time, actual harvesting panicles and dry matter accumulation of female ear after flowering increased, and water use efficiency was improved. Considering ecological factors and result in this study, the best suitable maize sowing time should be before May 4th for drought avoidance and maize high yield in this region. The research results provide effective cultivation techniques to avoid drought stress for spring maize in this area.