Wind as a limitation on the growth and yield of strawberries

Reduction in mean wind speed from 1.6 m/s to 1.1 m/s produced a mean increase of 56% in the yield of the strawberry Cambridge Favourite over a 3-year cropping period. Variation in response from year to year was appreciable and appeared to be linked to the wind conditions in the previous growing season.

Extensive bruising of leaves in exposed plots was recorded, and this appeared to be a more likely reason for growth depression than indirect effects of exposure by altering plant temperature or soil water balance. Earliness of cropping was virtually unaffected by reduction in wind speed.

Shelter improved not only the total yield but also the regularity of yield from year to year. The exposed plots showed yield variation from 9.8 to 15.8 t/ha compared with 16.6 to 19.1 t/ha in the sheltered plots.     

Ethylene production as an indicator of stress conditions in hydroponically-grown strawberries

As a soilless system, hydroponics eliminates competing weeds and soil-born pests while conserving water and providing conditions that can be quickly altered to suit specific crops. However, stress-induced physiological conditions may arise within the system from factors such as mechanical injury, pests, or inconsistent nutrient flow rates that result in some plants receiving too much or too little water. Most abiotic stress conditions result in increased production of the plant hormone ethylene. High levels of ethylene inhibit growth, cause premature ripening, and induce the onset of senescence, potentially reducing the productivity of hydroponically-grown crops. In this study, we demonstrate that assessing ethylene levels from leaves of hydroponically-grown strawberry plants can be used as an early indicator of stress conditions. Our results demonstrate that there is no significant correlation between ethylene production and temperatures ranging from 15 to 37 °C or with light intensities ranging from 63 to 1500 μmol m⁻² s⁻¹. However, an increase in ethylene production tended to be positively correlated with sampling time; levels were higher during midday compared to early morning or later afternoon. The daily ethylene fluctuations under greenhouse conditions due to sampling time, light intensity, or temperature changes were not significantly high enough to indicate stress conditions. Overall, three system analyses showed altered ethylene production in plants farthest from the pump supplying the nutrient solution. This effect was interpreted to be caused by excess accumulation of nutrient solution around the plant roots, causing increased ethylene production in the leaves. Our results indicate that different watering patterns, manifested as pump pressure or drainage control, was the more difficult component to control in the design of these hydroponic systems. For example, in one system, an increase in ethylene production was measured for the position farthest from the pump, and resulted in those plants having a lower number of flowers and significantly reduced overall plant radii relative to the system average. In a separate experiment, plants from trays that had been flooded for 24 h showed a significant decrease in the plant radii and number of leaves and flowers 1 month after the flooding treatment. We conclude that system-wide ethylene measurements can be used to identify stressed plants within hydroponic systems. This type of analysis would be especially useful as an indicator of general stress conditions no matter the cause, identifying locations that may result in lower plant productivity.     

甜菜安·宁等除草剂防除甜菜田杂草试验

选择性苗后茎叶处理除草剂两种混用组合精喹禾灵-甜菜安.宁和精喹禾灵-安·宁·乙呋黄应用于甜菜田的除草效果较为理想,精喹禾灵-甜菜安.宁组合对杂草总草株数防效为66.57%,鲜重防效为93.44%;精喹禾灵-安.宁.乙呋黄组合株数防效为73.69%,鲜重防效为95.27%。     

Long-day control of flowering in everbearing strawberries

Summary

Photoperiod and temperature control of flowering in a number of perpetual-flowering or everbearing strawberry cultivars of widely varying pedigree has been studied in controlled environments. Flower bud initiation in the cultivars ‘Flamenco’, ‘Ridder’, ‘Rita’ and ‘Rondo’ was significantly advanced by long-day (LD) conditions at temperatures of 15°C and 21ºC; while, at 27ºC, flowering took place under LD conditions only. Some plants of the seed-propagated F₁-hybrid ‘Elan’, raised at 21°C, also flowered under short-day (SD) conditions at 27°C, but reverted to the vegetative state after a few weeks when maintained under these conditions. When vegetative plants growing in SD at 27°C were transferred to LD conditions at the same temperature, they consistently initiated flower buds and started flowering after about 4 weeks. At such a high temperature, flowering could thus be turned on and off by switching between SD and LD conditions. This applied to all the cultivars studied. Also the cultivar ‘Everest’, which was tested only at 21°C, produced similar results. Night interruption for 2 h was effective in bringing about the LD response. At 9°C, flowering was substantially delayed, especially in ‘Flamenco’ and, at this temperature, flowering was unaffected by photoperiod. Runner formation was generally promoted by high temperature and SD conditions, but the photoperiodic effect varied between experiments. We conclude that everbearing strawberry cultivars, in general, whether of the older European-type or the modern Californian-type originating from crosses with selections of Fragaria virginiana ssp. glauca, are qualitative (obligatory) LD plants at high temperature (27°C), and quantitative LD plants at intermediate temperatures. Only at temperatures below 10°C are these cultivars day-neutral.     

Comparison of chemical control and manual runner removal in summer-planted strawberries

In summer (August) planting of chilled cv. Tioga strawberry runners, under Israeli growing conditions, there is excessive runner production until mid-December. These runners are removed manually several times during the autumn season. Frequent runner removal had no salutary effect on subsequent flowering and yield. PP-413 inhibited runner production and development highly significantly, but at high concentrations (1 000–2 000 ppm) it had an adverse effect on yield. Ancymidol (25 ppm) had almost no effect on runner development.     

Water relations and yield of lysimeter-grown strawberries under limited irrigation

The effects of partial root-zone drying (PRD), as compared to deficit irrigation (DI) and full irrigation (FI), on strawberry (cv. Honeoye) berry yield, yield components and irrigation water use efficiency (WUE_I) were investigated in a field lysimeter under an automatic rain-out shelter. The irrigation treatments were imposed from the beginning of flowering to the end of fruit maturity. In FI the whole root zone was irrigated every second day to field capacity viz. volumetric soil water content (θ) of 20%; while in DI and PRD 60% water of FI was irrigated to either the whole or one-half of the root system, respectively, at each irrigation event. In PRD, irrigation was shifted from one side to the other side of the plants when θ of the drying side had decreased to 8–11%. Compared to FI plants, leaf water potential was significantly lower in DI and PRD plants in 3 out of 10 measurement occasions, while stomatal conductance was similar among the three treatments. Leaf area, fresh berry yield (FY), individual berry fresh weight, berry water content, and berry dry weight (DW) were significantly lower in DI and PRD plants than those of FI plants; whereas the total number of berry per plant was similar among treatments. Compared with FI, the DI and PRD treatments saved 40% of irrigation water, and this led to a 28 and 50% increase of WUE_I based on berry FY and DW, respectively, for both DI and PRD. Conclusively, under the conditions of this study PRD had no advantage compared to DI in terms of berry yield and WUE_I. DI and PRD similarly decreased berry yield and yield components and thus cannot be recommended under similar conditions.     

Nutrition of glasshouse strawberries with nitrogen,phosphorus and potassium

A study was made of the fertilisation of glasshouse soil and nursery beds in the open for strawberries. The response of the crop to variations in fertiliser treatment was greater in the nursery beds than in the glasshouse. Only nitrogen dressing were of some importance under glass, but too much nitrogen proved to be harmful. The correct fertilisation of the nursery beds with nitrogen and potash is most important. Basic slag proved to be a suitable phosphate fertiliser for the nursery beds, but triple superphosphate cannot be recommended.     

江苏丘陵地区草莓灰霉病菌(Botrytis cinerea)对QoIs类杀菌剂的抗药性研究

【目的】明确江苏丘陵地区草莓灰霉病菌(Botrytis cinerea)对甲氧基丙烯酸酯类杀菌剂(QoIs)的抗药性区域分布和抗药性分子机制,为抗药性治理提供依据。【方法】区分计量法和抑制中浓度法测定草莓灰霉病菌对嘧菌酯和吡唑醚菌酯的抗药性区域分布和对药剂的敏感性表型,采用草莓果实离体测定法评估药剂对不同药剂敏感性菌株的防效,通过药剂靶标基因的序列分析确定抗药性分子机制。【结果】236株草莓灰霉病菌中对嘧菌酯和吡唑醚菌酯呈抗性的菌株有192株,2个药剂呈正交互抗性。嘧菌酯和吡唑醚菌酯敏感菌株的平均抑菌中质量浓度(EC50值)分别为0.269 8和0.055 9 mg·L~(-1)。77个嘧菌酯抗性菌株的EC50值全部大于100 mg·L~(-1),而吡唑醚菌酯抗性菌株的EC50平均值为67.680 7mg·L~(-1)。接种抗性菌株后再防治的试验证明,嘧菌酯和吡唑醚菌酯在推荐剂量(a.i 166.67 mg·L~(-1))下失去防效;所有抗性菌株的cyt b基因上都只含有G143A点突变,且第143位氨基酸后均不含有内元(Bcbi-143/144);敏感菌株cyt b基因分为2种,47.4%的敏感菌株不含有Bcbi-143/144,而52.6%的敏感菌株含有Bcbi-143/144。【结论】江苏丘陵地区田间草莓灰霉病菌群体中,对QoIs类药剂产生高水平抗药性的种群已成为主导种群,生产中不宜再用该类药剂防治草莓灰霉病。所有田间采集灰霉病菌抗性菌株的抗性分子机制均为cyt b基因G143A点突变,未发现其他位点突变类型。     

Chromosome observation method at metaphase and pro-metaphase stages in diploid and octoploid strawberries

Chromosome observation is necessary to elucidate the structure, function, organization, and evolution of octoploid strawberry plants’ genes and genomes. However, distinguishing strawberries’ chromosomes from one another using light microscopy is extremely difficult, not only because of their small size and large number, but also because current chromosome observation methods are insufficient. Chromosome preparation and staining using maceration enzymes, acetic acid, and DAPI (4′,6-diamidino-2-phenylindole) were improved for this study to obtain clear images of somatic chromosomes in Fragaria vesca (2n = 14) and Fragaria×ananassa (2n = 56). Collected root tips of octoploid plants were placed in 0.002 M 8-hydroxyquinoline solution for 1 h and stored at 4 °C for 16 h. Subsequently, they were fixed using 3:1 absolute alcohol:glacial acetic acid for 40 min, hydrolyzed in the 1N HCl solution at room temperature for 2 h, macerated using an enzyme solution for 25 min at 42 °C, and stained in 1.5% lacto-propionic orcein solution. On the other hand, in case of DAPI staining, the macerated root tips of octoploid plants were soaked in 60% acetic acid for 5 min before staining. Clear digital images of F. vesca and F.×ananassa were obtained using light and fluorescent microscopy. Their respective 14 and 56 chromosomes were counted. Fluorescent microscopy yielded clear chromosome images at the pro-metaphase in F. vesca and F.×ananassa. This chromosome observation method alleviates the difficulties that have heretofore hindered chromosome analyses of strawberry plants.     

Postharvest quality response of strawberries with aloe vera coating during refrigerated storage

Strawberries (Fragaria × ananassa Duch.) were coated either with chitosan (1, 1.5, and 2% solution, w/v) or aloe vera (AV) gel and the coatings were air dried. Coated strawberries were put in a polypropylene box and stored in refrigerator (6 ± 1°C and 50 ± 5% relative humidity. The success of coating in retaining the postharvest quality of the strawberries was evaluated by determining respiration rate, firmness, weight loss, external colour change, ascorbic acid content, total soluble solids, acidity, pH, microbial decay and sensory quality. The incidence of microbial rot started on day-6 in uncoated and 1% chitosan coated strawberries. Strawberries coated with 1.5 and 2% chitosan were affected by microbial decay on day-9 of storage. On the other hand, rot incidence was initiated in AV gel coated strawberries on day-15 of storage. Aloe vera gel or chitosan coating reduced respiration rate, weight loss, and microbial decay and preserved firmness, ascorbic acid content, and other quality parameters, thus delaying ripening and the progress of fruit decay due to senescence or microbial attack. Furthermore, AV gel delayed the changes in external colour and retained all other postharvest quality of strawberries compared to chitosan coated or uncoated ones throughout the storage.     

Effect of phosphite fertilization on growth,yield and fruit composition of strawberries

Traditionally, phosphates (Pi, salts of phosphoric acid, H₃PO₄) have been used for plant fertilization, and phosphites (Phi, salts of phosphorous acid, H₃PO₃) have been used as fungicides. Nowadays several Phi fertilizers are available in the EU market despite the fact that in research trials Phi has often had a negative influence on plant growth. The objective of this study was to elucidate the effect of a Phi fertilizer on plant growth, yield and fruit composition of strawberries (Fragaria × ananassa Duch.). Experiments were carried out with ‘Polka’ frigo plants in South Estonia in 2005 and 2006. The number of leaves per plant, total and marketable yields, fruit size, fruit ascorbic acid content (AAC), soluble solids content (SSC), titratable acidity (TA), anthocyanins (ACY) and total antioxidant activity (TAA) were recorded.     

Progress in the establishment of human embryonic stem cell lines

Embryonic stem(ES) cells are derived from totipotent cells of the early mammalian embryo and are capable of unlimited, undifferentiated proliferation an vitro .The establishment of mouse ES cell lines demonstrated the unmatchable convenience for the study of mouse embryonic development and the particular gene regulation and function. It has been long expected to construct such cell line for human. Here we summarized the development in the construction of human ES cell line, its potential utilization in various fields and the possible ethical dilemmas it brought with were also discussed.     

Evaluation of an agricultural experiment station as a case study site for the establishment of a multi-use urban forest

In an attempt to contribute towards a more sustainable development for the island of Puerto Rico, this project focuses on the documentation and evaluation of the Tropical Agriculture Research Station (TARS) near the urban center of the city of Mayagüez, Puerto Rico as a case study site to establish a multi-use and research-oriented urban forest. This location has been used since the beginning of the 20th century as a plant introduction and evaluation site, and as an in situ germplasm collection for numerous plant species. The evaluation methods consisted of identifying unique resources within the study area and stressors which could affect the latter. Unique resources were also identified on a Preliminary Resource Inventory Map (PRIM) using GPS technology. Obtained results and observations indicate that the study area represents a major potential asset for the positive economic, social, and educational development of the Mayagüez urban area due to its unique, historic, and complex ecosystems with significant environmental and cultural resources. Of the identified stressors, urban expansion was considered as the most threatening. Hypothetical recommendations providing a base for future development and management efforts in the study area were formulated with the objective of protecting and sustainably using its resources, while promoting environmental and socioeconomic benefits in the region.     

利用叶绿素荧光技术分析2个草莓品种的低温适应性

利用快速叶绿素荧光诱导动力学曲线分析技术及JIP-test分析,研究了4℃低温胁迫1、2、4、6 d对一季草莓‘红颜’和四季草莓‘圣安德瑞斯’光系统Ⅱ的影响,结合相对电导率和叶绿素含量分析2个草莓品种的低温适应性。结果表明:胁迫条件下K相可变荧光占F_J-F_o振幅的比例(W_k)无显著增加,PSII放氧复合体未受到伤害;但随低温胁迫时间延长2个草莓品种最大光化学效率(F_v/F_m)及性能指数(PI_abs)降低,发生光抑制;同时用于电子传递到Q^-_A以下的效率(ψ_o)和电子传递的量子比率(φ_Eo)也在降低;反应中心的数量(RC/CS_o),反应中心吸收、捕获的能量(ABS/RC、TR_o/RC)随胁迫时间延长大致呈增加趋势,但低于各自对照;‘圣安德瑞斯’虽在胁迫后期反应中心吸收的光能(ABS/RC)较‘红颜’多,但没有更多用于推动电子传递(ET_o/RC),而是通过热耗散(DI_o/RC)减轻对植株的伤害,相反‘红颜’反应中心数量增加后吸收的能量多用于推动电子传递;4℃低温下,2个草莓品种质膜透性相对稳定;与各自对照相比,‘红颜’叶片的各参数在低温胁迫后变化幅度缓于‘圣安德瑞斯’。快速叶绿素荧光动力学参数、相对电导率和叶绿素含量的比较结果显示,‘红颜’对低温的适应性优于‘圣安德瑞斯’。     

RIP和TCS双价转基因草莓抗草莓镶脉病毒鉴定

用小叶嫁接法对农杆菌转化RIP和TCS双价抗病毒基因所获得的草莓品种森嘎拉和戈雷拉转基因植株接种草莓镶脉病毒,采用PCR方法检测嫁接成活后的转基因草莓苗草莓镶脉病毒。结果表明:这2个品种的转基因植株均有部分植株未扩增出草莓镶脉病毒特异条带,说明转入的外源基因具有一定的抗草莓镶脉病毒作用。     

广东香蕉商品树立品牌问题

新世纪年初，国内农贸批发市场推介了不少的果菜名产，如赣南脐橙，宜宜夏橙，砀山酥梨，高州储良，东莞糯米糍，周至猕猴桃，注蝻莲藕，寿光韭菜，金乡大蒜……等优质农产品，这是以地域命名的农产品，     

Sod establishment and turfgrass growth as affected by urea–formaldehyde resin foam soil amendment

Urea–formaldehyde resin foam (UFRF) has recently been introduced as a soil amendment for turfgrass culture. A field study was performed to evaluate the impact of UFRF on soil physical and chemical properties, sod establishment and turfgrass shoot and root growth. Treatments included a non-amended, sandy loam soil and the same soil amended with UFRF at a rate of 20% (v/v) incorporated into the upper 0.1 m of the substrate. Physical and chemical analyses of the two substrates involved the determination of bulk density, total porosity, air-filled porosity at 0.4 m, moisture release curve, pH and electrical conductivity. Turfgrass growth was determined through several measurements that included shoot growth rate, root growth rate and monitoring of three root architecture parameters namely, total root length, total root area and mean root diameter. Turfgrass establishment was evaluated by measuring the vertical force applied to detach the sod from the substrate.UFRF amendment did not influence pH and EC and provided minimal alterations (non-significant) in soil physical properties by slightly increasing total porosity, easily available water and air-filled porosity, and by reducing bulk density. The impact of UFRF amendment improved cumulative clipping yield in five sampling dates but root growth and sod establishment rate were better than the control only on one sampling date. There appears to be limited benefit in amending soil with UFRF.     

Relationships between yield components in first cropping year and average yield of short-day strawberries over two main seasons

Fruit productivity of the garden strawberry, Fragaria × ananassa Duch., is a result of interrelationship of yield components contributing to it directly or indirectly. The main aim of the investigation was to find out whether there exists any general regularity, connecting relationships between main yield components in first cropping year to average yield of two main seasons. Two successive studies which primarily included 23 genotypes, differing in yield components and productivity, each, were planted in field conditions in spring 1999 and in spring 2000, respectively, and used for data collection to explore the material obtained in them. Four key yield components and average yields were measured in both cropping years, after which all possible ratios between the components were calculated to find out: first, the relationships to be influential on average yield of the two main seasons; second, type of the probable yield dependence upon the ratios; and, third, their values leading to high yields. Two ratios between the key yield components in first season, i.e.: inflorescence number per plant to branch crown number per plant, named ratio 1, and fruit weight (g) to flower count per inflorescence, named ratio 2, have been found to be related to average yield. An irregular surface, with a single peak falling approximately in its centre, describes average yield dependence upon the ratios. Values of the two ratios falling in the range of 1.0–1.6 each, provided that they are close, have enabled plants to produce high yields cumulatively over two first years. The paper highlights the most important differences in plant behaviour and yield dynamics of strawberry genotypes, depending on combinations of the ratios in first year, discerning those, which have been particularly advantageous to obtain very high yields, and are influenced by negative environmental factors least of all. Based on the findings, a method of predicting of average yield has been developed. Following this, usefulness of the method and possibilities of its using in strawberry breeding and variety trial are discussed.     

Landscape patterns in boundary intensity: a case study of mussel beds

This work examines the proposition that positive interactions among neighboring individuals within a population may produce landscape patterns in boundary intensity. The large scale patterns emerge because the interactions favor an aggregated distribution in the face of a potential limiting factor, and the strength of that factor varies over the landscape. The consequences of spatially varying neighborhood processes were explored using cellular automata simulating the structure of mussel beds in 2-dimensional intertidal landscapes, each characterized by a vertical gradient of tidal immersion and a horizontal gradient of wave energy. Running the model with and without the neighborhood processes demonstrated that the facilitating neighborhood processes elevate intensity above that caused by the gradients, and consequently abrupt (high intensity) boundaries emerged in the midst of gradual environmental variation. Trends generated on the 2-D landscape by the model were compared with those in photo-mosaics of intertidal mussel beds, Mytilus californianus on rocky shores of the British Columbia. The analysis involved interpolation of boundary locations using a spatially-constrained cluster algorithm, and then estimation of the corresponding boundary intensities using a landscape index aggregation (CLUMPY). The general similarity between predicted and real trends in intensity over the wave energy gradients suggests that spatially varying neighborhood processes determine much of the landscape scale variation in boundary intensity, while certain discrepancies (e.g. a more rapid rise of observed intensities with increasing wave exposure) suggest modifications of the theory and new empirical work.     

Health status of the pear tree following the establishment of Fire blight in Northern Tunisia

ABSTRACT

Pears have great importance in Tunisia for their desirable taste and commercial value. Until 2012, the pear cultivation was protected against fire blight by the application of a rigorous quarantine system. Fire blight, caused by Erwinia amylovora, was outbreak in Tunisia in the spring of 2012 and has spread rapidly through the most important pear growing regions destroying several hundred hectares of pear plantations. Therefore, the total pear production has decreased from 60,000 metric tons in 2011 to less than 20,000 metric tons in 2016. In this study, collected data of pear culture and surveys were carried out during four years (2012–2016) in the main pear growing areas to evaluate the current situation of the disease in the country particularly in the damaged regions of the lower valley of Medjerda (Manouba, Ben Arous, Bizerte, and Beja). Samples collected from symptomatic trees were processed for the isolation and identification of the causal agent using microbiological and molecular techniques. The results indicate that the disease had destroyed more than 5500 hectares among a total of 8400 hectares of pear plantations area. Both provinces Manouba and Ben Arous were the most affected by fire blight disease resulting in the eradication of 350 and 325 hectares of pear plantations, i.e., 100% and 98% of the total infected area, respectively. All control attempts, including sanitary measures, the application of mineral oil and copper, growth regulators and biological control have failed to limit the spread of the disease. The presence of pathogen in the prospected regions was confirmed by pathogenicity and molecular tests, which are compatible with the symptoms observed throughout the surveys. The pear cultivation in Tunisia is threatened by fire blight due to the restriction tolerance of the available varieties and the climatic conditions favoring the staggered flowering of the species. Quarantine measures must be implemented to prevent the spread of this disease in a new disease-free areas.