Table of Content

10 October 2018, Volume 44 Issue 10

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CROP GENETICS & BREEDING · GERMPLASM RESOURCES · MOLECULAR GENETICS

Use of Bar Gene for the Stable Transformation of Herbicide-resistant Foxtail Millet Plants

Qian-Nan CHEN,Ke WANG,Sha TANG,Li-Pu DU,Hui ZHI,Guan-Qing JIA,Bao-Hua ZHAO,Xing-Guo YE,Xian-Min DIAO

Acta Agronomica Sinica. 2018, 44(10):  1423-1432.  doi:10.3724/SP.J.1006.2018.01423

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Efficiency of Agrobacterium-mediated genetic transformation has been the main factor that restricts the study of functional genes and transgenic breeding in foxtail millet. In this study, foxtail millet variety Jigu 11 panicle primordia were used as explants. Young panicles of 0.5-1.0 cm in length were picked and cut into small pieces. The young embryos were cultured in modified MS medium for inducing embryogenic calli, totally forming 3120 embryogenic calli in 15-20 days. Soaking the calli in the infection suspension prior to transformation, and the heat treatment at 45°C for 3 min could effectively improve the transient genetic transformation efficiency by 26.1%. The transformed calli were screened with phosphinothricin (PPT), in which 513 were resistant calli, with the resistant calli rate of 16.4%. Seven herbicide-resistant plants were obtained after resistant calli differentiation and seedling culture. Six T₀ transgenic positive plants were identified by PCR and Southern blot. PPT resistance analysis was carried out on leaves in T₃ generation of transformed plants, and combined with Bar protein antibody test strip identification, the results confirmed that the Bar gene stably incorporated into the genome of foxtail millet seedlings. This study established a stable genetic transformation system in foxtail millet, which is of great significance in improving the efficiency of molecular breeding, and prompting foxtail millet as a new model plants.

Cloning and Function Analysis of ZmNAOD Gene in Maize

Chen-Yu MA,Wei-Min ZHAN,Wen-Liang LI,Meng-Di ZHANG,Zhang-Ying XI

Acta Agronomica Sinica. 2018, 44(10):  1433-1441.  doi:10.3724/SP.J.1006.2018.01433

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The development of kernels and the photoperiod characters are key elements that impact yield in maize. A N-acetylornithine deacctylase (NAOD) gene named ZmNAOD was cloned from maize inbred line Chang 7-2 by the method of RT-PCR in our work. The length of CDS (coding DNA sequence) in ZmNAOD gene is 1344 bp, coding a polypeptide of 447 amino acids. The expression of ZmNAOD was abundant in tassel, kernel, leaf, stem and root successively, and was up-regulated in seed from 0 to 15 d, and down-regulated after 15 d. The over-expression recombinant plasmid, pCAMBIA1304-ZmNAOD, was transformed into Arabidopsis using Agrobacterium mediated method, and homogeneous transgenic lines were obtained. The ZmNAOD gene expression was abundant in roots of transgenic Arabidopsis, and the root length was significantly longer than that of the wild type (WT) after a 10-day dark treatment. Flowering days of transgenic lines were earlier, the seeds were longer and the thousand seed weight was heavier than those of the WT. These results demonstrated that the ZmNAOD might be involved in seed development and photoperiod.

Molecular and Cytogenetic Identification of Triticum aestivum-Leymus racemosus Translocation Line T5AS-7LrL·7LrS

Lin-Sheng WANG,Ya-Li ZHANG,Guang-Hui NAN

Acta Agronomica Sinica. 2018, 44(10):  1442-1447.  doi:10.3724/SP.J.1006.2018.01442

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Leymus racemosus is highly resistant to wheat scab. The transfer of resistance genes from L. racemosus to common wheat (Triticum aestivum) is important for broadening the resistant sources against scab in common wheat. In this study, the pollen of DA7Lr, a T. aestivum-L. racemosus disomic addition line with scab resistance, was irradiated with ⁶⁰Co-γ ray at 1200 Rad (100 Rad min ^-1) before pollinating to emasculated T. aestivum cv. Chinese Spring. One plant with one translocation chromosome was detected in the M₁ generation by GISH. This plant was then self-pollinated and the pollen mother cells (PMCs) of the offspring plants with two translocation chromosomes were cytologically observed, and one ring bivalent was found at meiotic metaphase I, indicating that the plant with two translocation chromosomes was one translocation homozygote. The translocation line was proved to be T5AS-7LrL·7LrS by C-banding, and sequential GISH-FISH using Oligo-pAs1-2 and Oligo-pSc119.2-2 as probes. Three EST-STS markers (BE591127, BQ168298, and BE591737) were identified to be able to track the T5AS-7LrL·7LrS line. The translocation line also serves as an resistant source against wheat scab in wheat breeding programs.

Characterization of Growth Period Structure and Identification of E Genes of MGIII Soybean Varieties from Different Geographic Regions

Hong JIANG,Shi SUN,Wen-Wen SONG,Cun-Xiang WU,Ting-Ting WU,Shui-Xiu HU,Tian-Fu HAN

Acta Agronomica Sinica. 2018, 44(10):  1448-1458.  doi:10.3724/SP.J.1006.2018.01448

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In 2014 and 2015, 60 Maturity Group (MG) III soybean varieties from different geographic regions were chosen to characterize the maturity-related traits and to identify the alleles of the maturity genes (E alleles) in these varieties. The MGIII soybean varieties shared the similar growth period but owned different growth period structure. The spring-sowing MGIII soybean varieties from Northern China and the US bloomed earlier (shorter VP) and exhibited lower R/V values than those from Yellow-Huai-Hai River Valley (YHH) and South China. Six combinations of E alleles were identified in the tested Chinese varieties, among them E1e2E3E4 and e1-asE2E3E4 were found to distribute in larger areas of different regions and cover more ecotypes than other four combinations. In contrast, the type of e1-asE2E3E4 was the only E allele combination in the eight US standard varieties, indicating that the Chinese MGIII varieties were more abundant in genetic variations for the maturity-related traits. By comparing the average effect of each E allele on the maturity-related traits in MGIII soybean varieties under different sowing dates, it was found that the varieties with more dominant E alleles showed longer VP, shorter RP and smaller R/V value. The effects of different E alleles on flowering time and maturity were different, and the effect of the dominant E alleles on spring- sowing soybeans was stronger than that on the summer-sowing ones. The agronomic traits for MGIII varieties from different regions were significantly different and that correlated with the growth period structure. The height of bottom pods of MGIII soybean varieties from Northern China was negatively correlated with R/V, while the number of pods per plant was positively correlated with R/V. Branch number, pod number per plant and 100-seed weight of YHH MGIII varieties were not correlated with R/V. The branch number of southern soybean varieties was significant negative correlated with the VP. These results provide a basis for the improvement of the growth period structure of soybean varieties and adaptability of soybeans to multiple environments.

Identification of Cold-tolerance During Germination Stage and Genetic Diversity of SSR Markers in Peanut Landraces of Shanxi Province

Dong-Mei BAI,Yun-Yun XUE,Jiao-Jiao ZHAO,Li HUANG,Yue-Xia TIAN,Bao-Quan QUAN,Hui-Fang JIANG

Acta Agronomica Sinica. 2018, 44(10):  1459-1467.  doi:10.3724/SP.J.1006.2018.01459

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Cold injury is one of the main factors causing yield and quality decline in peanut. Cultivating and planting varieties with high and stable yield and strong cold tolerance is an ideal way to reduce cold injury, However, the lack of high cold tolerant germplasm and the difficulty of cold tolerance identification are the main reasons to limit the breakthrough of cold tolerance breeding. In this study, 72 local peanut varieties in Shanxi province were identified for cold tolerance at germination stage. Based on their relative germination rate and relative germination index, the cold tolerance of 72 peanut cultivars we preliminarily divided the 72 peanut cultivars into five grades, namely high-cold-tolerant type, cold-tolerant type, middle type, sensitive type, and high sensitive type. Ninety pairs of SSR primers with good polymorphism were used to evaluate the peanut cultivars with different cold-tolerance levels, and to examine the genetic diversity of cold-tolerant peanut landraces in Shanxi province making rational and efficient use of cold tolerant peanut resources. The tested cultivars were highly different in genetic diversity and were clustered into three groups with genetic distance of 0.4. Three high-cold-tolerant cultivars and seven cold-tolerant cultivars were clustered into three different groups, indicating that the cold-tolerant peanut varieties are rich in genetic diversity.

Construction of Hairy Root Induction System and Functional Analysis of TTG1 Gene in Brassica juncea

Long LI,Cheng CHENG,Xiao-Fang WU,Da-Wei ZHANG,Li-Li LIU,Jing ZHOU,Mei-Liang ZHOU,Kai-Xuan ZHANG,Ming-Li YAN

Acta Agronomica Sinica. 2018, 44(10):  1468-1476.  doi:10.3724/SP.J.1006.2018.01468

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Yellow seed rape has the advantages of thin seed coat and high oil yield. It is of great significance to study the formation of yellow seed in rapeseed. Previous studies showed that TTG1 (TRANSPARENT TESTA GLABRA 1) gene was involved in the formation of seed coat color. In this study, Agrobacterium rhizogenes A4 strain was used to induce hairy roots of Sichuan yellow, and investigate the effects of bacterial concentration and different sources of explants on hairy root induction. The highest average rooting rate was 71.5% when the OD value of A. rhizogenes A4 reached to 0.8. The average rooting rate of hypocotyls was significantly higher than that of cotyledons and up to 87.3% after the infection. Overexpression of TTG1 gene in Sichuan yellow hairy roots inhibited the expression of DFR (Dihydroflavonol4-reductase), ANS (Anthocyanidin synthase), and BAN (Anthocyanidin reductase) genes, encoding key enzymes of the proanthocyanidins biosynthesis. In this study, we optimized the induction system of hairy roots in B. juncea, and analyzed the function of TTG1 in the regulation of proanthocyanidins synthesis pathway, which provide a new idea and method for the functional analysis of genes in the hairy root system.

Identification of Rice Chromosome Segment Substitution Line Z1377 with Increased Plant Height and QTL Mapping for Agronomic Important Traits

Guo-Qing CUI,Shi-Ming WANG,Fu-Ying MA,Hui WANG,Chao-Zhong XIANG,Yun-Feng LI,Guang-Hua HE,Chang-Wei ZHANG,Zheng-Lin YANG,Ying-Hua LING,Fang-Ming ZHAO

Acta Agronomica Sinica. 2018, 44(10):  1477-1484.  doi:10.3724/SP.J.1006.2018.01477

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Plant height is an important agronomic trait in rice, usually relating to yield-related traits. Here, a novel rice chromosome segment substitution line Z1377 with increased plant height was identified from recipient Nipponbare and donor Jinhui 35 through selection of both phenotype and molecular marker. Z1377 carried 18 substitution segments with average substitution length of 2.95 Mb. Compared with Nipponbare, Z1377 had significantly increased plant height, length of the 1st, 2nd, 3rd, and 4th internode, panicle length, number of primary and secondary branches and grain length, and decreased grain width, number of panicles per plant and seed setting ratio. However, the seed setting ratio was still 86.75%. Furthermore, F₂ population from crosses between Nipponbare and Z1377 was used to map QTLs for plant height and other important agronomic traits. A total of 16 QTLs were detected, of which eight had been reported with the cloned genes such as GW2, EUI1, ZFP185, and the other eight were still not reported, such as qPH3. The plant height of Z1377 was mainly controlled by a major QTL (qPH3) with the explained phenotypic variance of 28.59% and a minor QTL (qPH5). Moreover, the high and dwarf plants basically displayed a bimodal distribution in the F₂ population, and fitted to 3:1 segregation ratio by Chi-square test, indicating that high plant is dominant to dwarf plants and mainly conferred by qPH3. These results lay a foundation for fine mapping and cloning qPH3, meanwhile, also provide good bases for developing excellent chromosome segment substitution lines with moderate height plant carrying 2-3 substitution segments to be used in breeding.

TILLAGE & CULTIVATION · PHYSIOLOGY & BIOCHEMISTRY

Effects of Reduced Nitrogen on Soil Ammonification, Nitrification, and Nitrogen Fixation in Maize-soybean Relay Intercropping Systems

Tai-Wen YONG,Ping CHEN,Xiao-Ming LIU,Li ZHOU,Chun SONG,Xiao-Chun WANG,Feng YANG,Wei-Guo LIU,Wen-Yu YANG

Acta Agronomica Sinica. 2018, 44(10):  1485-1495.  doi:10.3724/SP.J.1006.2018.01485

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The ammonification, nitrification, and nitrogen fixation processes of soil are the main factors affecting nitrogen acquisition by plants and nitrogen loss in soil. A field experiment was conducted to reveal the characteristics of soil nitrogen transformation and emission with reduced nitrogen application in the maize-soybean relay intercropping. The effects of three planting patterns (MM: maize monoculture; MS: soybean monoculture; IMS: maize-soybean relay strip intercropping) and three nitrogen application rates (no nitrogen, NN: 0; reduced nitrogen, RN: reduced N 180 kg ha ^-1; conventional nitrogen, CN: conventional N 240 kg ha ^-1) on ammonification, nitrification, nitrogen fixation, N emission, and NO₃ ^--N accumulation were assessed. The IMS enhanced soil nitrification and ammonification enhanced in IMS compared with the corresponding monocultures. The ammonia volatilization and N₂O loss ratio were decreased by 21.6% and 29.7% in IMS compared with those in MM, respectively. Additionally, compared with the corresponding monocultures, IMS had significantly higher soil NO₃ ^--N accumulation of maize, while that of soybean significantly lower. Under different N levels, the soil ammonification and nitrification of maize were decreased in RN compared with those in CN, and the soil nitrification and nitrogen fixation of soybean were increased in RN compared with those in CN. The total nitrogen fixation of maize and soybean in IMS was increased by 29.7% and 32.0% in RN compared with those in CN, respectively. In addition, the annual soil ammonia volatilization and N₂O emission of IMS were decreased by 37.2% and 41.0% in RN compared with those in CN, respectively. In summary, the maize-soybean relay intercropping with reduced nitrogen can provide sufficient nitrogen for crops by strengthening soil ammonification, nitrification, nitrogen fixation, and increasing soil nitrogen residual and decreasing nitrogen emissions.

Effects of Potassium Application on Photosynthetic Performance, Yield, and Quality of Sugar Beet with Mulching-drip Irrigation

Chun-Yan HUANG,Wen-Bin SU,Shao-Ying ZHANG,Fu-Yi FAN,Xiao-Xia GUO,Zhi LI,Cai-Yuan JIAN,Xiao-Yun REN,Qian-Heng GONG

Acta Agronomica Sinica. 2018, 44(10):  1496-1505.  doi:10.3724/SP.J.1006.2018.01496

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The technology of drip irrigation under mulch is widely used for sugar beet cultivation in cold and arid region of Inner Mongolia. In order to investigate proper potassium application rate and effects of potassium on photosynthetic characteristics, yield and quality on sugar beet with mulching-drip irrigation, a field experiment was conducted at Liangcheng city of Inner Mongolia in 2014-2015 with five treatments (0, 90, 180, 270, and 360 kg ha ^-1)potassium application. The results indicated that potassium could increase the photosynthetic performance of sugar beet, enhancing plant height, leaf area index and net photosynthetic rate. The treatments of 180, 270, and 360 kg ha ^-1 potassium fertilizer increased the net photosynthetic rate, which mainly affected by RuBPCase activity, followed by stomatal conductance. Proper potassium application benefited dry weigh increasing of roots, shoots and leaves, and yield increasing. But excessive application of potassium fertilizer significantly decreased the dry matter distribution to roots, and sugar content. There were the highest yield 270 kg ha ^-1 potassium application, the highest sugar content in the treatment of 90 kg ha ^-1 potassium and the largest economic benefits in the treatment of 180 kg ha ^-1potassium. When the application amount of potassium was more than 180 kg ha ^-1, the contents of K ⁺ and Na ⁺ increased in root. When the application amount of potassium was more than 270 kg ha ^-1, the content of α-amino acid in roots increased. According to the effects of potassium on sugar beet yield and quality, the recommended potassium fertilizer rate was 180 kg ha ^-1 in the main sugar beet planting area in Inner Mongolia.

Variation of Grain Iron and Zinc Contents and Their Bioavailability of Wheat Cultivars with Different-colored Grains under Combined Nitrogen and Phosphorus Fertilization

Xin HUANG,Yao-Guang LI,Wan SUN,Jun-Feng HOU,Ying MA,Jian ZHANG,Dong-Yun MA,Chen-Yang WANG,Tian-Cai GUO

Acta Agronomica Sinica. 2018, 44(10):  1506-1516.  doi:10.3724/SP.J.1006.2018.01506

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Six wheat cultivars with different-colored grains (white, red, and black) were used to investigate effects of combined N (N1: 90 kg N ha^-1; N2: 240 kg N ha^-1) and P (P1: 60 kg P₂O₅ ha^-1; P2: 209 kg P₂O₅ ha^-1) fertilization on grain yield, Fe and Zn contents and accumulation in grain, and their bioavailability in a two-year field experiment. Black-grain cultivars had a higher average Fe and Zn bioavailability than the red- and white-grain cultivars. Meanwhile, there were inter-annual differences in Fe and Zn contents and accumulation in grains among different wheat cultivars. Maximum grain yield, Fe and Zn contents and accumulation were observed under N2P1 treatment, while highest Fe and Zn bioavailability were observed under N2P2 or N2P1 treatment. Red-grain cultivars Yangmai 15 and Yangmai 22 got the highest Fe and Zn contents, and accumulation amount under N2P1 treatment. Black-grain cultivars Zhouheimai 1 and Zimai 1 got the highest Fe content and accumulation amount under N2P2 treatment, followed by N2P1. Most cultivars had the highest Fe and Zn bioavailability under N2P1 or N2P2 treatment, which indicated that increasing N application results in a higher grain yield, Fe and Zn contents, and their bioavailability. In this experiment, wheat cultivars would benefit from N2P1 treatment in terms of grain yield, Fe and Zn contents, and their bioavailability.

Grain Filling and Dehydration Characteristics of Summer Maize Hybrids Differing in Maturities and Effect of Plant Density

Ze-Hua WAN,Bai-Zhao REN,Bin ZHAO,Peng LIU,Shu-Ting DONG,Ji-Wang ZHANG

Acta Agronomica Sinica. 2018, 44(10):  1517-1527.  doi:10.3724/SP.J.1006.2018.01517

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Exploring grain-filling and dehydration characteristics of summer maize hybrids differing in maturities and the regulation function of plant density, could provide theoretical and technical reference for the mechanized grain harvest in The Yellow- Huaihe-Haihe Rivers plain region. A field experiment was conducted from 2016 to 2017, using early hybrids Denghai 518 (DH518), Hengzao 8 (HZ8) and middle-late hybrids Zhengdan 958 (ZD958), Denghai 605 (DH605) with three plant densities of 60 000, 75 000, and 90 000 plants ha ^-1. The grain-filling duration was shorter and the yield was lower in early hybrids DH518, HZ8 than in middle-late hybrids ZD958, DH605. Grain moisture content of the four hybrids at physiological maturity had no significant correlation with their growth period duration. Compared with middle-late hybrids, grain dehydration rate of early hybrids at late growth stage was faster. In 2016 and 2017, mean value of grain dehydration rate from the date reaching maximum grain water content to physiological maturity of DH518 and HZ8 was 0.015% °C ^-1 and 0.014% °C ^-1 higher than that of ZD958 and DH605 respectively. The grain dehydration rate had no significant correlation with filling rate, the moisture content in grain at late growth stage was positively correlated with that in stem, sheath and leaf at P < 0.05, and with that in bract and cob at P < 0.01. With increasing plant density, grain-filling duration of different summer maize hybrids become shorter, average filling rate reduced, and grain moisture content at physiological maturity reduced. Reasonably increasing plant density could significantly improve the yield of summer maize hybrids differing in maturities.

Effect of Exogenous Ca ²⁺ on Physiological Characteristics and Secondary Metabolites accumulation of Atropa belladonna L. Seedlings under UV-B Stress

Ke-Huan LU,Xing LIU,Yi YANG,Zhi-Hua LIAO,Neng-Biao WU

Acta Agronomica Sinica. 2018, 44(10):  1527-1538.  doi:10.3724/SP.J.1006.2018.01527

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Ultraviolet B (UV-B) radiation does harm to plant, for which growth and development. Ca ²⁺is one of the most necessary elements. Exogenous Ca ²⁺ can enhance plant abilities to resist stress and regulate secondary metabolism. In this research, we used Atropa belladonna L. seedlings to investigate the effects of different concentrations of exogenous Ca ²⁺ and different treatment days on the physiological characteristics, nitrogen metabolism, secondary metabolites content and relative genes expression levels of three key enzymes in secondary metabolism under the background of UV-B radiation. The UV-B radiation not only caused inhibitory effect on the Atropa belladonna L. photosynthesis, nitrogen metabolism, alkaloid content, but also increased peroxidation of membrane lipid. The F_o, MDA content gradually decreased, but the F_v/F_m, photosynthetic pigment content, antioxidant enzyme activity gradually increased under Ca ²⁺ treatment, showing that Ca ²⁺ is propitious to relieve inhibitory effect on photosynthesis and enhance resistance to UV-B stress. Moreover, Ca ²⁺ reduced the content of nitrate nitrogen significantly, promoted the contents of free amino acids, soluble proteins, atropine alkaloids, and raised the activities of key enzymes in nitrogen metabolism. Using real-time fluorescence quantitative PCR, we found that exogenous Ca ²⁺ increased the relative gene expression levels of three key enzymes in secondary metabolism in different degrees. This research could provide a theoretical references for plantation in the field.

Bacterial Diversity of Soybean Rhizosphere Soil under Different Cropping Patterns

Fang WANG,Jing-Sheng CHEN,Da-Wei LIU

Acta Agronomica Sinica. 2018, 44(10):  1539-1547.  doi:10.3724/SP.J.1006.2018.01539

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To study bacterial community structure of soybean rhizosphere soil in rotation and continuous cropping, 16S rDNA gene were sequenced of soil samples infected soybean cyst nematode from Heilongjiang Province two regions by the second generation of high-throughput sequencing Illumina MiSeq platform. A total of 25 419 OTUs were obtained from six soil samples and classified into 47 phylum, 147 class, and 709 genera. Proteobacteria, Actinobacteria, Acidobacteria, Gemmatimonadetes, Planctomycetes were dominant bacteria, accounting for more than 90% of all soil bacterial communities. The total OTUs and richness were the highest in four years continuous cropping and the lowest in twenty years continuous cropping. The difference of bacteria abundance in different rotational cropping years was not obvious (P > 0.05), but abundance and adversity were significant in continuous cropping (P < 0.05). The relative abundance of Actinobacteria in different rotations was lower than that in continuous cropping, and the relative abundance of Gemmatimonadetes and Bacteroidetes was higher than that in the same area. The relative abundance of soil functional bacteria Bradyrhizobium, Streptomyces, Bacillus, Lysobacter, and Pedomicrobium were higher in different continuous cropping years than those in rotations. Predominant bacterial abundance in long term continuous cropping was more similar with that in rotational cropping.

TILLAGE & CULTIVATION · PHYSIOLOGY & BIOCHEMISTRY

Differences in Yield and Grain Quality among Various Types of Indica/japonica Hybrid Rice and Correlation between Quality and Climatic Factors during Grain Filling Period

Dong XU, Ying ZHU, Lei ZHOU, Chao HAN, Lei-Ming ZHENG, Hong-Cheng ZHANG, Hai-Yan WEI, Yu WANG, An-Ye LIAO, Shi-Bo CAI

Acta Agronomica Sinica. 2018, 44(10):  1548-1559.  doi:10.3724/SP.J.1006.2018.01548

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Abstract: In order to find out the reasons for quality performance difference in different indica/japonica hybrid rice varieties, a field experiment was conducted with 18 early maturing late indica/japonica hybrid rice varieties (lines), among them three representative types of indica/japonica hybrid rice (including Type A: good quality with high yield; Type B: bad quality with high yield; Type C: bad quality and low yield) were screened according to them yield, cooking and eating quality. The variation in the yield and quality of different types of indica/japonica hybrid rice was studied. The average yields of A and B were 22.66% and 22.26% higher than there of C respectively, due to more panicles per unit area and large number of spikelets per panicle of A and B. The rates of brown rice and head milled rice of A were 1.9% to 2.5% and 13.9% to 22.7% higher than those of B and C respectively. Compared with A, the average chalky rate and chalkiness of B and C were 43.3% to 47.5% and 64.5% to 71.4% higher. The average amylose contents were 31.7% and 33% higher in B and C than in A, and the average gel consistency was 4.0% and 4.5% longer in A than in B and C respectively. Type A had the highest peak viscosity, breakdown, and the lowest setback. There was no significant differences in protein content among three types of indica/japonica hybrid rice. The temperature during the grain filling period was negatively correlated with the processing quality, appearance quality, the cooking and eating quality of indica/japonica hybrid rice. Therefore, in addition to genetic factors, through reasonable sowing date or cultivation management regulation, we can get relatively low temperature at grain filling stage of rice, which is conducive to the synchronous improvement in appearance quality and cooking and eating quality.

RESEARCH NOTES

Effect of Planting Density on the Growth, Water Use Efficiency and Yield of Dry-farming Potato under Different Rainfall Year Types

Xian-Qing HOU,You-Wen NIU,Wen-Li WU,Jin-Peng XU,Long SHI,Shao-Ying TANG,Xu MA,Rong LI

Acta Agronomica Sinica. 2018, 44(10):  1560-1569.  doi:10.3724/SP.J.1006.2018.01560

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In order to explore the reasonable planting density of potato under plastic film mulching and ridge planting, a 2-year field experiment was conducted in semi-arid areas liable to droughts of southern Ningxia between 2015 and 2016, with five planting density treatments, including 37 500 (A), 45 000 (B), 52 500 (C), 60 000 (D), and 67 500 plant ha ^-1 (E). Local traditional planting density of 37 500 plant ha ^-1 (A) was as the control. Different planting densities could significantly influence the water status of soil layer at 0-100 cm during the earlier and middle stages of potato growth. The soil water storages in treatments B and C were the highest, which were significantly higher than those in treatments A and E. The treatments B and C could significantly increase emergence rate of potato, and promote the growth of potato during the early stage and middle stage compared with other treatments, whereas there were no significant differences among the five treatments during the later stage of potato growth. The tuber yield and commodity rate of potato increased at first and then decreased with increasing planting density. Compared with treatment A, the 2-year mean rainfall use efficiency of treatments B and C were significantly increased by 15.3% and 17.6%, and mean water use efficiency were significantly increased by 11.1% and 15.0%, respectively. By function fitting with the two-year data, the highest tuber yield and water use efficiency of dry-farming potato under plastic film mulching and ridge planting was demonstrated in normal year and dry year in semi-arid areas liable to droughts of southern Ningxia, which was 51 187-51 302 plant ha ^-1.

Effects of Water and CO₂ Concentration on Stomatal Traits, Leaf Gas Exchange, and Biomass of Winter Wheat

Hai-Xia WU,Li-Li GUO,Li-Hua HAO,Hao ZHANG,Qing-Tao WANG,Dong-Juan CHENG,Zheng-Ping PENG,Fei LI,Xi-Xi ZHANG,Shu-Bin LI,Ming XU,Yun-Pu ZHENG

Acta Agronomica Sinica. 2018, 44(10):  1570-1576.  doi:10.3724/SP.J.1006.2018.01570

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The experiment was conducted in environmental growth chambers with accurately controlled CO₂ concentrations. Water deficit resulted in the decrease of stomatal openness and more irregular stomatal distribution of winter wheat, and elevated CO₂ concentration ([CO₂]) mitigated the negative impacts on the morphological traits of individual stoma and spatial distribution of stomata. The net photosynthetic rate, stomatal conductance, and transpiration rate of winter wheat significantly decreased (P < 0.05) under water deficits than under full irrigation condition, while elevated [CO₂] could mitigate the influence of mild water deficit on leaf gas exchange, and this mitigated effect declined with the increase of water deficit degree. In addition, the biomass of winter wheat was substantially decreased with water deficits but barely affected by elevated [CO₂] under water deficits. These results suggested that winter wheat changes its leaf gas exchange by adjusting morphological traits of individual stoma and spatial distribution pattern of stomata under water deficit, and the “CO₂ fertilization effect” on winter wheat may be modified by soil water conditions.