Differential Responses of <i>NHX1</i> and <i>SOS1</i> Gene Expressions to Salinity in two <i>Miscanthus sinensis</i> Anderss. Accessions with Different Salt Tolerance

The lignocellulosic crop Miscanthus spp. has been identified as a good candidate for biomass production. The responses of Miscanthus sinensis Anderss. to salinity were studied to satisfy the needs for high yields in marginal areas and to avoid competition with food production. The results indicated that the relative advantages of the tolerant accession over the sensitive one under saline conditions were associated with restricted Na⁺ accumulation in shoots. Seedlings of two accessions (salt-tolerant ‘JM0119’ and salt-sensitive ‘JM0099’) were subjected to 0 (control), 100, 200, and 300 mM NaCl stress to better understand the salt-induced biochemical responses of genes involved in Na⁺ accumulation in M. sinensis. The adaptation responses of genes encoding for Na⁺ /H⁺ antiporters, NHX1 and SOS1 to NaCl stress were examined in JM0119 and JM0099.The cDNA sequences of genes examined were highly conserved among the relatives of M. sinensis based on the sequencing on approximate 600 bp-long cDNA fragments obtained from degenerate PCR. These salt-induced variations of gene expression investigated by quantitative real-time PCR provided evidences for insights of the molecular mechanisms of salt tolerance in M. sinensis. The expression of NHX1 was up-regulated by salt stress in JM0119 shoot and root tissues. However, it was hardly affected in JM0099 shoot tissue except for a significant increase at the 100 mM salt treatment, and it was salt-suppressed in the JM0099 root tissue. In the root tissue, the expression of SOS1 was induced by the high salt treatment in JM0119 but repressed by all salt treatments in JM0099. Thus, the remarkably higher expression of NHX1 and SOS1 were associated with the resistance to Na⁺ toxicity by regulation of the Na⁺ influx, efflux, and sequestration under different salt conditions.     

Spatial Heterogeneity of Selected Soil Nutrients Related to <i>Torreya grandis</i> cv. <i>Merrillii</i> Plantation in Southeastern China

Chinese Torreya grandis (Torreya grandis cv. Merrillii) is a unique economic tree species in China. Intensive management related to application of chemical fertilizer and herbicides caused serious soil quality degradation of Chinese Torreya grandis plantations. Totally, 120 soil samples were collected from the main disbtributed areas of Chinese Torreya grandis in Southeastern China. In this area, soil pH values varied from 3.68 to 6.78, with a median value of 4.91, implying a trend of acidification. The average concentrations of organic matter, available nitrogen, available phosphorus and available potassium were 27.52 g kg⁻¹, 135.77 mg kg⁻¹, 15.12 mg kg⁻¹, and 153.43 mg kg⁻¹, respectively. The results of spatial analysis revealed that target variables had clear spatial patterns. The soil fertility was relevantly high in most of the study area, with soil nutrient imbalances existing. The stand age had a large effect on soil properties, which were also mainly influenced by human activities. Therefore, it is necessary to change the fertilization method for a sustainable management of Torreya grandis plantation.     

<i>In vitro</i> Germination and Micropropagation of <i>Aconitum vilmorinianum</i>: An Important Medicinal Plant in China

Aconitum vilmorinianum, a well-known traditional Chinese herb, is recently being threatened by overexploitation and environment disturbance. This study was conducted to provide propagation methods through in vitro germination and explant cultivation. Germination was stimulated up to 66.00% on Murashige and Skoog (MS) medium containing 2.0 mg L⁻¹ 6-benzylaminopurine (BAP), 0.1 mg L⁻¹ 1-napthaleneacetic acid (NAA), and 30 g L⁻¹ sucrose. Three bacteria (Pantoea agglomerans, Erwinia persicina, and Pseudomonas tolaasii) would be responsible for consistent contamination during germination. The latter two were effectively eradicated after disinfected. The influence of explant types and hormone combinations on direct and indirect organogenesis was evaluated in the present work. The frequency of shoot induction from axillary bud explants was 100% on the MS fortified with 2.0 mg L⁻¹ BAP and 0.3 mg L⁻¹ NAA. Shoots multiplication was optimized on MS medium supplemented with 0.1 mg L⁻¹ thidiazuron (TDZ) and 0.1 mg L⁻¹ NAA. High callus induction percentage (96.67%) was obtained from stem segments on MS medium with 2.0 mg L⁻¹ 2,4-D, then successfully regenerated into shoots on MS medium in the presence of 0.1 mg L⁻¹ TDZ and 0.2 mg L⁻¹ NAA. The present work could be useful for the utilization and conservation of this valuable species.     

Optimization of <i>Agrobacterium tumefaciens</i>-Mediated Genetic Transformation of Maize

Immature embryos of inbred maize (Zea mays) lines (H8183, H8184, and H8185) were used for Agrobacterium infection. We used the β-glucuronidase gene (GUS) as the target gene and the glufosinate resistance gene (bar) as the selection marker. We conducted research on several aspects, such as different genotypes, coculture conditions, screening agent concentrations, and concentrations of indole-3-butytric acid (IBA), 6-benzylaminopurine (6-BA), and ascorbic acid (Vc) in the differentiation medium. We optimized the genetic transformation system, and the obtained results indicated that among the three lines studied, the induction rate of H8185 was the highest at 93.2%, followed by H8184, with H8183 having the lowest induction rate (80.1%). The best coculture method was that using the N6 coculture medium layered with a sterile filter paper. Using orthogonal analysis, we found that the optimal combination of the three factors in the differentiation medium was A₃ (1 mg mL⁻¹ IBA), B₃C₁ (1.6 mg mL⁻¹ 6-BA), and D₃ (1.5 mg mL⁻¹ Vc). Through GUS staining analysis, Bar test-strip analysis, and polymerase chain reaction, five transgenic plants were finally obtained. This study established the optimal conditions for genetic transformation in maize.     

Biomass yield in a genetically diverse Miscanthus sacchariflorus germplasm panel phenotyped at five locations in Asia,North America,and Europe

Miscanthus is a high-yielding bioenergy crop that is broadly adapted to temperate and tropical environments. Commercial cultivation of Miscanthus is predominantly limited to a single sterile triploid clone of Miscanthus × giganteus, a hybrid between Miscanthus sacchariflorus and M. sinensis. To expand the genetic base of M. × giganteus, the substantial diversity within its progenitor species should be used for cultivar improvement and diversification. Here, we phenotyped a diversity panel of 605 M. sacchariflorus from six previously described genetic groups and 27 M. × giganteus genotypes for dry biomass yield and 16 yield-component traits, in field trials grown over 3 years at one subtropical location (Zhuji, China) and four temperate locations (Foulum, Denmark; Sapporo, Japan; Urbana, Illinois; and Chuncheon, South Korea). There was considerable diversity in yield and yield-component traits among and within genetic groups of M. sacchariflorus, and across the five locations. Biomass yield of M. sacchariflorus ranged from 0.003 to 34.0 Mg ha⁻¹ in year 3. Variation among the genetic groups was typically greater than within, so selection of genetic group should be an important first step for breeding with M. sacchariflorus. The Yangtze 2x genetic group (=ssp. lutarioriparius) of M. sacchariflorus had the tallest and thickest culms at all locations tested. Notably, the Yangtze 2x genetic group's exceptional culm length and yield potential were driven primarily by a large number of nodes (>29 nodes culm⁻¹ average over all locations), which was consistent with the especially late flowering of this group. The S Japan 4x, the N China/Korea/Russia 4x, and the N China 2x genetic groups were also promising genetic resources for biomass yield, culm length, and culm thickness, especially for temperate environments. Culm length was the best indicator of yield potential in M. sacchariflorus. These results will inform breeders' selection of M. sacchariflorus genotypes for population improvement and adaptation to target production environments.     

Rapid Propagation of <i>Rhynchostylis retusa in Vitro</i>

An efficient regeneration system of Rhynchostylis retusa was established to provide technical reference for the application of tissue culture tube seedlings in production. The mixtures of callus and protocorm from aseptic germination were used as explants. The optimal media of each stage was selected for callus proliferation, protocorm occurrence and growth, rejuvenation and rooting via a single, complete combination and orthogonal experiment. The results showed that the optimal medium for callus proliferation, protocorms occurrence and growth was 1/2 Murashige and Skoog (MS) medium adding 50 g·L⁻¹ banana puree, 0.1 mg·L⁻¹ α-naphthaleneacetic acid (NAA), 1.5 mg·L⁻¹ 6-benzylaminopurine (6-BA) and 1.0 mg·L⁻¹ kinetin (KT) with 17.33 proliferation coefficient of callus and 19.63 occurrence coefficient of buds after 90 days. Then the buds occurred from protocorm were cultured on 1/2 MS medium including 100 g·L⁻¹ banana puree, 1.0 mg·L⁻¹ NAA, 2.0 mg·L⁻¹ 6-BA and 0.05 mg·L⁻¹ KT, in which the proliferation coefficient of callus was 10.32 and occurrence coefficient of buds reached 17.87. In the further subculture, the same medium was simultaneously used for callus proliferation, protocorm occurrence and bud growth. The plantlets developed roots in 1/2 MS medium containing 70 mL·L⁻¹ coconut water and 1.5 mg·L⁻¹ NAA with 100% rooting rates after 90 days. The survival rate was more than 90% after domestication and transplantation. This regeneration protocol will provide technique foundation for protecting wild resource and developing artificial cultivation.     

Integrated Nutrient Management Improves Productivity and Quality of Sugarcane (<i>Saccharum Officinarum</i> L.)

Sugarcane is one of the major important sugar yielding crops in Bangladesh. As an exhaustive crop, sugarcane removes a huge amount of plant nutrients from the soil. However, the combined use of organic and inorganic fertilizers can be a good approach to deal with nutrient depletion and promote sustainable crop production as well as improve soil health. Therefore, an attempt was made to identify the most fruitful and profitable integrated nutrient management on the aspects of growth, yield and quality of sugarcane in two consecutive growing seasons. Seven treatments: T₁=Control, T₂=165:55:120:30:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₃=Poultry Litter (PL) at 5 t ha⁻¹+95:51:87:9:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₄=Cow Dung (CD) at 15 t ha⁻¹+ 36:52:60:17:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₅=Press Mud (PM) at 15 t ha⁻¹+10:50:43:0:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹, T₆=Mustard Oil Cake (MOC) at 0.5 t ha⁻¹+140:54:115:25:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹ and T₇=GM (Green Manure) at 5 t ha⁻¹+140:53:100:28:10:2.5:4 kg N:P:K:S:Mg:Zn:B ha⁻¹ were used in this experiment. Two years data showed that treatment T₃ produced the maximum amount of tillers, total dry matter yield, millable sugarcane, cane yield and sugar yield, followed by the T₄ treatment. The highest stalk heights were recorded in the T₃ treatment, which was statistically similar to all other treatments except T₁ and T₂. The juice quality parameters viz., brix and pol in cane were found significant in treatment T₃ while the highest purity was obtained in the T₇ treatment. All the data of Jaggery (goor) quality parameters, the highest sucrose content, color transmittance, Jaggery (goor) recovery and the lowest ash content of Jaggery (goor) were observed in the T₃ treatment, which was statistically similar to the T₄ treatment in both seasons. The highest cost of production was obtained from the T₆ treatment while the highest gross return, net return and BCR were recorded in the T₃ treatment. No significant changes were found in one cycle of sugarcane in initial and post-harvest soil characteristics viz., pH, organic carbon, total N, and available P, K and S contents due to integrated use of different fertilizer packages. From the experimental findings, it was concluded that treatment T₃ followed by T₄ treatment would be the better productive and profitable integrated nutrient management technology for ensuring higher yields and quality of sugarcane without soil fertility degradation in the High Ganges River Floodplain soils.     

Biomass production and energy balance of Miscanthus over a period of 11 years: A case study in a large‐scale farm in Poland

Giant miscanthus (Miscanthus × giganteus Greef and Deuter) and Amur silver grass (Miscanthus sacchariflorus Maxim./Hack) are rhizomatous grasses with a C4 photosynthetic pathway that are widely cultivated as energy crops. For those species to be successfully used in bioenergy generation, their yields have to be maintained at a high level in the long term. The biomass yield (fresh and dry matter [DM] yield) and energy efficiency (energy inputs, energy output, energy gain, and energy efficiency ratio) of giant miscanthus and Amur silver grass were compared in a field experiment conducted in 2007–2017 in North‐Eastern Poland. Both species were characterized by high above‐ground biomass yields, and the productive performance of M. × giganteus was higher in comparison with M. sacchariflorus (15.5 vs. 9.3 Mg DM ha^?1 year^?1 averaged for 1–11 years of growth). In the first year of the experiment, the energy inputs associated with the production of M. × giganteus and M. sacchariflorus were determined at 70.5 and 71.5 GJ/ha, respectively, and rhizomes accounted for around 78%–79% of total energy inputs. In the remaining years of cultivation, the total energy inputs associated with the production of both perennial rhizomatous grasses reached 13.6–15.7 (M. × giganteus) and 16.9–17.5 GJ ha^?1 year^?1 (M. sacchariflorus). Beginning from the second year of cultivation, mineral fertilizers were the predominant energy inputs in the production of M. × giganteus (78%–86%) and M. sacchariflorus (80%–82%). In years 2–11, the energy gain of M. × giganteus reached 50 (year 2) and 264–350 GJ ha^?1 year^?1 (years 3–11), and its energy efficiency ratio was determined at 4.7 (year 2) and 18.6–23.3 (years 3–11). The energy gain and the energy efficiency ratio of M. sacchariflorus biomass in the corresponding periods were determined at 87–234 GJ ha^?1 year^?1 and 6.1–14.3, respectively. Both grasses are significant and environmentally compatible sources of bioenergy, and they can be regarded as potential energy crops for Central‐Eastern Europe.     

Improving Quantitative and Qualitative Characteristics of Wheat (<i>Triticum aestivum</i> L.) through Nitrogen Application under Semiarid Conditions

Nitrogen (N), the building block of plant proteins and enzymes, is an essential macronutrient for plant functions. A field experiment was conducted to investigate the impact of different N application rates (28, 57, 85, 114, 142, 171, and 200 kg ha⁻¹) on the performance of spring wheat (cv. Ujala-2016) during the 2017–2018 and 2018–2019 growing seasons. A control without N application was kept for comparison. Two years mean data showed optimum seed yield (5,461.3 kg ha⁻¹) for N-application at 142 kg ha⁻¹ whereas application of lower and higher rates of N did not result in significant and economically higher seed yield. A higher seed yield was obtained in the 2017–2018 (5,595 kg ha⁻¹) than in the 2018–2019 (5,328 kg ha⁻¹) growing seasons under an N application of 142 kg ha⁻¹. It was attributed to the greater number of growing degree days in the first (1,942.35°C days) than in the second year (1,813.75°C). Higher rates of N (171 and 200 kg ha⁻¹) than 142 kg ha⁻¹ produced more number of tillers (i.e., 948,300 and 666,650 ha⁻¹, respectively). However, this increase did not contribute in achieving higher yields. Application of 142, 171, and 200 kg ha⁻¹ resulted in 14.15%, 15.0% and 15.35% grain protein concentrations in comparison to 13.15% with the application of 114 kg ha⁻¹. It is concluded that the application of N at 142 kg ha⁻¹ could be beneficial for attaining higher grain yields and protein concentrations of wheat cultivar Ujala-2016.

     

Synthetic polyploid production of Miscanthus sacchariflorus,Miscanthus sinensis,and Miscanthus x giganteus

Plants from the genus Miscanthus are potential renewable sources of lignocellulosic biomass for energy production. A potential strategy for Miscanthus crop improvement involves interspecific manipulation of ploidy levels to generate superior germplasm and to circumvent reproductive barriers for the introduction of new genetic variation into core germplasm. Synthetic autotetraploid lines of Miscanthus sacchariflorus and Miscanthus sinensis, and autoallohexaploid Miscanthus x giganteus were produced in tissue culture from oryzalin treatments to seed‐ and immature inflorescence‐derived callus lines. This is the first report of the genome doubling of diploid M. sacchariflorus. Genome doubling of diploid M. sinensis, M. sacchariflorus, and triploid M. x giganteus to generate tetraploid and hexaploid lines was confirmed by stomata size, nuclear DNA content, and chromosome counts. A putative pentaploid line was also identified among the M. x giganteus synthetic polyploid lines by nuclear DNA content and chromosome counts. Comparisons of phenotypic performance of synthetic polyploid lines with their diploid and triploid progenitors in the greenhouse found species‐specific differences in plant tiller number, height, and flowering time among the doubled lines. Stem diameter tended to increase after polyploidization but there were no significant improvements in biomass traits. Under field conditions, M. x giganteus synthetic hexaploid lines showed greater phenotypic variation, in terms of plant height, stem diameter, and tiller number, than their progenitor lines. Production of synthetic autopolyploid lines displaying significant phenotypic variation suggests that ploidy manipulation can introduce useful genetic diversity in the limited Miscanthus germplasm currently available in the United States. The role of polyploidization in the evolution and breeding of the genus Miscanthus is discussed.     

Genome-wide association and genomic prediction for yield and component traits of Miscanthus sacchariflorus

Accelerating biomass improvement is a major goal of Miscanthus breeding. The development and implementation of genomic-enabled breeding tools, like marker-assisted selection (MAS) and genomic selection, has the potential to improve the efficiency of Miscanthus breeding. The present study conducted genome-wide association (GWA) and genomic prediction of biomass yield and 14 yield-components traits in Miscanthus sacchariflorus. We evaluated a diversity panel with 590 accessions of M. sacchariflorus grown across 4 years in one subtropical and three temperate locations and genotyped with 268,109 single-nucleotide polymorphisms (SNPs). The GWA study identified a total of 835 significant SNPs and 674 candidate genes across all traits and locations. Of the significant SNPs identified, 280 were localized in mapped quantitative trait loci intervals and proximal to SNPs identified for similar traits in previously reported Miscanthus studies, providing additional support for the importance of these genomic regions for biomass yield. Our study gave insights into the genetic basis for yield-component traits in M. sacchariflorus that may facilitate marker-assisted breeding for biomass yield. Genomic prediction accuracy for the yield-related traits ranged from 0.15 to 0.52 across all locations and genetic groups. Prediction accuracies within the six genetic groupings of M. sacchariflorus were limited due to low sample sizes. Nevertheless, the Korea/NE China/Russia (N = 237) genetic group had the highest prediction accuracy of all genetic groups (ranging 0.26–0.71), suggesting that with adequate sample sizes, there is strong potential for genomic selection within the genetic groupings of M. sacchariflorus. This study indicated that MAS and genomic prediction will likely be beneficial for conducting population-improvement of M. sacchariflorus.     

An Efficient Plant Regeneration System of <i>Hydrangea bretschneideri</i> Dipp via Stem Segments as Explants

Hydrangea bretschneideri Dipp is a highly popular ornamental plant for garden decoration. Genetic engineering technology has been successfully used in many plant species, but it is limited in Hydrangea. Here we established an efficient regeneration system by using stem segments as explants for the first time. In our study, the plant growth regulators (PGRs) were evaluated at the different regeneration processes, including axillary shoots regeneration and root induction. We found that the optimal concentration for axillary buds’ induction was 2.0 mgL⁻¹ 6-BA and 0.5 mgL⁻¹ 1 IAA, its highest induction rate was 70%. Moreover, the highest axillary shoots proliferation coefficient was 10.7 on the Murashige and Skoog (MS) medium with 2.0 mgL⁻¹ 6-benzyladenine (BA), 0.2 mgL⁻¹ indole-3-butyric acid (IBA), and 1.0 mgL⁻¹ gibberellin A3 (GA3). The highest frequency of root induction was 80.0 ± 0.06% by culturing the elongated shoots in 1/2 MS medium containing 0.1 mgL⁻¹ IBA. In summary, our study will provide an effective technology for large-scale propagation and important pathway for promoting the popularization and application of Hydrangea bretschneideri Dipp.     

Malate secretion from the root system is an important reason for higher resistance of Miscanthus sacchariflorus to cadmium

Miscanthus is a vigorous perennial Gramineae genus grown throughout the world as a promising bioenergy crop and generally regarded as heavy metal tolerant due to its ability to absorb heavy metals. However, little is known about the mechanism for heavy metal tolerance in Miscanthus. In this study, two Miscanthus species (Miscanthus sacchariflorus and Miscanthus floridulus) exhibiting different cadmium (Cd) sensitivity were used to address the mechanisms of Cd tolerance. Under the same Cd stress, M. sacchariflorus showed higher Cd tolerance with better growth and lower Cd accumulation in both shoots and roots than M. floridulus. The malate (MA) content significantly increased in root exudates of M. sacchariflorus following Cd treatment while it was almost unchanged in M. floridulus. Cellular Cd analysis and flux data showed that exogenous MA application markedly restricted Cd influx and accumulation while an anion‐channel inhibitor (phenylglyoxal) effectively blocked Cd‐induced MA secretion and increased Cd influx in M. sacchariflorus, indicating that MA secretion could alleviate Cd toxicity by reducing Cd uptake. The genes of malate dehydrogenases (MsMDHs) and Al‐activated malate transporter 1 (MsALMT1) in M. sacchariflorus were highly upregulated under Cd stress, compared with that in M. floridulus. The results indicate that Cd‐induced MA synthesis and secretion efficiently alleviate Cd toxicity by reducing Cd influx in M. sacchariflorus.     

<i>In Vitro</i>-Propagation of <i>Agave tequilana</i> Weber cv. azul in a Temporary Immersion System

In Mexico, there is a need to produce large quantities of plantlets for the establishment and replanting of blue (cv. azul) agave production areas. Most of these plots are within the origin denomination area (DOT, Spanish acronym) of the distilled product of this plant, known as tequila. The objective of this study was to develop an in vitro-propagation protocol for Agave tequilana Weber cv. azul using segmented stems in both: solid and liquid media. A disinfection and in vitro technique were developed to obtain shoots, through plantlets collected in commercial plots, which attained 100% surface-disinfection and budding rate. At the multiplication stage, the effects of 6-Benzylaminopurine (BA) (0.0, 4.4 and 13.2 μM) and kinetin (0.0, 9.4, 18.8 and 37.6 μM) were evaluated on lateral-shoot production of segmented sagittal stems. These were cultivated on Murashige & Skoog (MS) medium, with the addition of 3.0% sucrose and 8 g L⁻¹ agar. It was observed that BA and kinetin increased the number of shoots per explant, obtaining up to 18 and 26, respectively. Furthermore, it was found that just the sagittal segmentation of explants increased axillary budding. On the other hand, segmented-stem bases were grown in MS liquid medium with 3.0% sucrose, inside a RITA® system, programmed by a 5 min immersion step with a frequency of every 4 h. The effect of Indole−3-Acetic acid (IAA) (0.57, 2.9, 5.7 μM) was evaluated, while maintaining a concentration of BA (13.2 μM). It was observed that the greatest concentration of IAA led to the formation of more than 20 buds per explant. These results offer a new methodology to increase the efficiency of A. tequilana Weber cv. azul-in vitro multiplication by sagittal segmentation of stems and the addition of BA and/or IAA.     

N-Exponential Fertilization Could Affect the Growth and Nitrogen Accumulation of <i>Metasequoia glyptostroboides</i> Seedling in a Greenhouse Environment

Metasequoia glyptostroboides (M. glyptostroboides) is a unique plant species related to relic flora in China. It plays a positive role in afforestation and its long-term protection with high paleoclimate research value. However, due to the nutrients-supply deficiency, it is a big challenge to cultivate the high-quality seedlings of M. glyptostroboides. In this study, a pot experiment in a greenhouse environment was carried out to identify the effect of N-exponential fertilization on the growth and nutrient distribution of M. glyptostroboides seedling. The M. glyptostroboides rooted seedlings with 12-month growth were chosen. Different N fertilizer levels with conventional fertilization (CF: 5.0 g seedling⁻¹), exponential fertilization including EF1, EF2, EF3 and EF4 were determined. The relevant growth indexes were measured after 210-day growth. The results indicated that non-significant differences in seedlings’ height and ground diameter were found among the above treatments (P > 0.05); At the same time, N-exponential fertilization promoted the M. glyptostroboides’s biomass in different organs (P < 0.05), with the maximum total biomass under EF3 treatment. The N accumulation in root and stem of the N-exponential fertilization treatments were increased in to some extent (P < 0.05). The maximum N accumulation was also found under EF3 treatment. Therefore, steady-state nutrition and superior growth performance of M. glyptostroboides could be obtained by N-exponential fertilization of 5.0 g cutting⁻¹.     

13种茎叶处理除草剂对不同生育期白花鬼针草的生物活性

[目的] 白花鬼针草是一种恶性外来入侵杂草,近年来已侵入农田,对农业生产及生态系统带来严重危害。为筛选防治白花鬼针草的有效除草剂,分析评价了13种常见茎叶处理除草剂对幼苗期和成株期白花鬼针草的防治效果。[方法] 采用整株盆栽法,在白花鬼针草幼苗期（2~3对叶期）和成株期（6~7对叶期）分别进行茎叶喷雾处理,每种除草剂设置3个剂量。[结果] 供试的13种除草剂中,灭生性除草剂草甘膦、草铵膦和敌草快对幼苗期和成株期的白花鬼针草防效达到100%。选择性除草剂中,麦草畏和辛酰溴苯腈对幼苗期和成株期的白花鬼针草均有较好的防效,三氯吡氧乙酸、乙羧氟草醚和氯吡嘧磺隆在高剂量下对幼苗期的白花鬼针草有较好的防除效果,但对成株期的白花鬼针草防效较差,氯氟吡氧乙酸、乳氟禾草灵、灭草松、二氯吡啶酸、乙氧氟草醚对幼苗期和成株期白花鬼针草防效均较差。[结论] 白花鬼针草对多种化学除草剂具有较强的耐药性,生育期对除草剂防除白花鬼针草的效果有较大影响。灭生性除草剂草甘膦、草铵膦、敌草快及选择性除草剂辛酰溴苯腈和麦草畏适用于防除白花鬼针草。     

Expression of a rice <Emphasis Type="Italic">CYP81A6</Emphasis> gene confers tolerance to bentazon and sulfonylurea herbicides in both <Emphasis Type="Italic">Arabidopsis</Emphasis> and tobacco

Bentazon and sulfonylurea are two different classes of herbicides that have been widely used to kill broad-leaf weeds in rice fields. A cytochrome P450 gene, CYP81A6, encoding a monooxygenase has been previously identified to confer resistance to these two classes of herbicides in wild-type rice. In this study, we introduced the rice CYP81A6 gene into Arabidopsis and tobacco plants to test the possibility of engineering tolerance to these two types of herbicides in other susceptible plants. Arabidopsis and tobacco plants expressing CYP81A6 showed tolerance to both bentazon and bensulfuron-methyl (BSM), a widely applied sulfonylurea herbicide. The optimal concentrations of bentazon and BSM for the selection of CYP81A6 transgenic plants were also determined. In addition, we also demonstrated that CYP81A6 can be used as a selection marker to effectively screen for positive transgenic Arabidopsis plants. The selection efficiency of CYP81A6 was comparable to that of the bar gene in Arabidopsis. These results suggest that CYP81A6 can not only be used to produce transgenic plants tolerant to both bentazon and sulfonylureas, but that it can also be used as a novel plant-derived selection marker in plant transformation.     

Plant morphology,genome size,and SSR markers differentiate five distinct taxonomic groups among accessions in the genus Miscanthus

Information on genome size, ploidy level, and genomic polymorphisms among accessions of the genus Miscanthus can assist in taxonomic studies, help understand the evolution of the genus, and provide valuable information to biomass crop improvement programs. Taxonomic investigation combining variation in plant morphology, genome size, chromosome numbers, and simple sequence repeat (SSR) marker polymorphisms were applied to characterize 101 Miscanthus accessions. A total of 258 amplicons generated from 17 informative SSR primer pairs was subjected to cluster and principal coordinate analysis and used to characterize genetic variation and relationships among 31 Miscanthus accessions, including four interspecific Miscanthus hybrids created from controlled pollinations, and four Saccharum, six Erianthus, and one Sorghum bicolor accessions. Miscanthus accessions were distinct from accessions in the genera Erianthus and Saccharum. Miscanthus accessions fell into five taxonomic groups, including the existing taxonomic section Miscanthus, diploid and tetraploid Miscanthus sacchariflorus, and a fourth (M. × giganteus) and fifth group (Miscanthus ‘purpurascens’); the last two being intermediate forms. In contrast to previous work, our findings suggest diploid and tetraploid M. sacchariflorus are taxonomically different, the latter more closely related to M. sacchariflorus var lutarioriparius. We also suggest that Miscanthus ‘purpurascens’ accessions are interspecific hybrids between Miscanthus sinensis and diploid M. sacchariflorus based on DNA content and SSR polymorphisms. The evolution of Miscanthus and related genera is discussed based on combined analysis and geographical origin.     

Effect of Water Stress Induced by Polyethylene Glycol on Growth,Proline Accumulation in <i>Agave americana</i> L.

The effect of water deficit was determined on both in vitro and soil seedling as well as in cells in suspension of Agave americana L. In order to do the establishment of cells, the formation of callus was induced; for it two auxins were evaluated: 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-mino-3,5,6-trichloropicolinic acid (picloram) at three concentrations (0.25, 0.5 and 0.75 mg L⁻¹) in three explants (leaf, root and meristems) cultured in MS semisolid medium. The callogenesis response was related to the type and section of the explant, as well as the regulator used, and a cell suspension was established using 0.5 mg L⁻¹ naphthaleneacetic acid (NAA) + 0.5 mg L⁻¹ Benzylaminopurine (BAP). Seedlings were exposed to polyethyleneglycol (15% and 30% w/v) with a water potential of −0.87 and −2.67 MPa, respectively, under soil conditions. Water stress was applied through restricted irrigation. Fresh weight, root system growth, and chlorophyll concentration were some of the parameters that were affected by the effect of water deficit on A. americana L. Chlorophyll concentration values were significantly decreased by 15 at 30% PEG (19.6 SPAD units) compared to the control treatment. In in vitro plants, the highest concentration of proline was found in the roots, being the treatment with 30% polyethylene glycol where the highest concentration of this osmoregulator was obtained (62.5 mg g⁻¹ DW). Under restricted irrigation conditions, an increase in proline concentration was observed both in the aerial part (2.2 µg 100 g⁻¹ DW) and in the root system (1.8 µg 100 g⁻¹ DW). However, the concentrations found were approximately ten times greater, less than those found under in vitro conditions. Therefore, the accumulation of proline can be considered an indicator of stress in Agave Americana L. growth in vitro.     

<Emphasis Type="Italic">Humulus japonicus</Emphasis> Accelerates the Decomposition of <Emphasis Type="Italic">Miscanthus sacchariflorus</Emphasis> and <Emphasis Type="Italic">Phragmites australis</Emphasis> in a Floodplain

Humulus japonicus in communities of Miscanthus sacchariflorus and Phragmites australis can grow large enough to overtop other species in the Amsa-dong floodplain. Because of strong winds and the weight of Humulus, plants of M. sacchariflorus and P. australis fell in mid-August and were subject to decomposition under its dense shading. To assess the effects of H. japonicus on nutrient cycling in these communities, we collected fresh samples of M. sacchariflorus and P. australis in litterbags and decomposed them under H. japonicus for 9 months, beginning in August. Biomass and organic contents from M. sacchariflorus during this incubation period were 49–51% and 44–48%, whereas those of P. australis were 49–61% and 32–52%, respectively. Their annual k values were 1.61–1.74 and 1.46–3.54, respectively. Initial N concentrations in M. sacchariflorus and P. australis were 13 and 20 mg g⁻¹, while C:N ratios were 31 and 21, respectively. These results indicate that H. japonicus is responsible for the collapse of M. sacchariflorus and P. australis in August and also accelerates their nutrient cycling through rapid decomposition, thereby increasing nutrient circulation in floodplains.