Non-Fumigant Treatments and Their Combinations Affect Soil Pathogens and Strawberry Performance in Southern California

ABSTRACT

Finding effective non-fumigant solutions to soil disinfestation is an international priority for sustainable strawberry production. In these studies at Ventura, California, combinations of steam, solarization, and mustard meal were evaluated to manage troublesome soil-borne pathogens: Macrophomia phaseolina and Fusarium oxysporum. Treatments containing steam and solarization reduced levels of these pathogens in soil 70–96% compared to untreated soil and had lower rates of late season pathogen-related plant mortality. All treatments improved plant canopy growth and fruit production of ‘San Andreas’ strawberry 58% to 83% compared to untreated control. Even though these treatments did not eradicate pathogen spores and sclerotia in soil, they enhanced early and whole season fruit production and when feasible can be applied in non-fumigated and organic strawberry fields to help sustain production.     

Transformation of tomatoes with osmotin and chitinase genes and their resistance to Fusarium wilt

Summary

Tomato (Lycopersicon esculentum cv. ‘A53’) was transformed with a tobacco osmotin gene and a bean chitinase gene using Agrobacterium to produce germplasm with improved Fusarium wilt-resistance. Molecular characterisation by polymerase chain reaction and Southern blot hybridisation confirmed the stable integration of the transferred genes into the genome at various insertion sites.Assays of transgene expression were performed using northern blot analysis. Susceptibility tests on two generations of transgenic tomatoes showed improved resistance to Fusarium oxysporum f. sp. lycopersici, the fungal pathogen responsible for Fusarium wilt in tomato. This dual combination of pathogenesis-related (PR) proteins may be useful in controlling other fungal pathogens in tomato.     

The effect of thermal environment,planting date and crown size on growth,development and yield of Fragaria × ananassa Duch. cv. Elsanta

Summary

The effects of environmental conditions, planting date and crown size on the timing, intensity and duration of cropping in the strawberry Fragaria × ananassa cv. Elsanta were investigated. Temperature was positively correlated with the rate of progress to fruiting whereas crown size had no effect. The first fruit reached harvest maturity after an estimated 891 day-degrees had elapsed above a base temperature of 2.9°C for waiting bed plants and 831 day-degrees above a base temperature of 2.4°C for cold stored plants. Temperature was negatively correlated with total yield, berry number and average berry weight for both waiting bed and cold stored plants of different crown sizes. Yield, berry number and average berry weight were positively correlated with crown size. The effect of temperature on the yield components appeared to be due to its effect on vegetative growth of the plants: canopy development was more limited at warmer temperatures. These results can be used to generate models to predict the effect of growth environment on cropping in strawberry.     

Status of Macrophomina phaseolina on Strawberry in California and Preliminary Characterization of the Pathogen

ABSTRACT

Macrophomina crown and root rot has become a significant soil-borne disease issue in California. For many locations in the state, the disease is associated with fields that are no longer pre-plant, flat field fumigated with methyl bromide + chloropicrin. Inoculation experiments indicated that some differences in strawberry cultivar susceptibility to Macrophomina phaseolina were seen a short time after the inoculation, but as disease progressed such differences did not persist. Preliminary characterization studies of Macrophomina phaseolina isolates from strawberry indicated that such isolates may have a host preference for strawberry. Macrophomina phaseolina isolates from watermelon, thyme, and apple failed to cause disease in strawberry. Five cover crop species, which can be rotated with strawberry, did not develop disease when inoculated with strawberry isolates. In preliminary analysis using simple sequence repeat markers, isolates obtained from strawberry formed a separate group compared to isolates recovered from other known Macrophomina phaseolina hosts.     

Evaluation of Strawberry Genotypes for Chaetosiphon fragaefolii (Strawberry Aphid) Preference

ABSTRACT

Thirty-one strawberry genotypes were evaluated for supporting the reproductive success of the strawberry aphid (Chaetosiphon fragaefolii), a vector of several strawberry viruses. A pure colony of C. fragaefolii was initiated from eggs collected from field strawberry leaves in Fall 2013. In Spring 2014 greenhouse-grown strawberry plants with four to five leaves were placed in screened cages (16 genotypes/cage) and five aphids were placed on each plant. After 30–32 days, the number of aphids in each of four developmental stages was counted on each plant. Total aphid numbers/plant ranged from a mean of 33 on Fragaria chiloensis CFRA 48 (PI 551459) to 279 on F. × ananassa ‘AAC Lila’. Cultivars with relatively low numbers of aphids included ‘Bounty’ (106 aphids), ‘Mira’ (114 aphids), and ‘Annapolis’ (115 aphids). This experiment, part of a larger project on aphids and virus diseases associated with the cultivated strawberry, will inform decisions in the strawberry breeding program.     

对羟基苯甲酸对豇豆枯萎病菌的抑制作用

研究了不同浓度的对羟基苯甲酸(p-HB)对豇豆枯萎病菌孢子萌发、菌丝生长及挑战接种后对幼苗发病率的影响。结果表明：低浓度p-HB对豇豆枯萎病菌菌丝生长抑制作用不明显,而中、高浓度（5.0、10.0 mmol·L^-1）p-HB对菌丝生长的抑制作用达到极显著水平;在1.0～10.0mmol·L^-1范围内,p-HB 随着浓度的升高对豇豆枯萎病菌孢子萌发的抑制作用越大;1.0～10.0 mmol·L^-1的p-HB均能降低幼苗的发病率,尤其是浓度为10.0 mmol·L^-1时,能显著降低幼苗的发病率。     

Histopathological Observations in Guava Root during Wilting caused by Fusarium Species: A Scanning Electron Microscopy Study

Fusarium oxysporum and Fusarium solani are the two most destructive pathogens causing wilt disease in guava (Psidium guajava L.) commonly known as ‘super fruits’. These pathogens attack mainly on the root region of the plant and cause severe infection. In the present investigation the infection process was studied with scanning electron microscopy (SEM) and it was observed that the root region of the guava plant showed disintegration and necrosis in the epidermal layer, cortex tissue, and in vascular bundles, while the root region of a healthy sapling showed no such changes. The rupturing of the epidermal layer may show the entry of pathogens in the host tissue through the secretion of toxic enzymes/metabolites. These toxins have great potential to cause wilting symptoms in guava plants in the form of necrosis. Wilt disease causes huge losses in guava production in both tropical and subtropical countries. Therefore, there is a need to find the responsible factors. The present study is an attempt to understand the interaction mechanism of phyto-pathogens causing wilt disease.     

Bioassay method for testing Fusarium wilt disease tolerance in transgenic banana

Fusarium wilt caused by the fungus, Fusarium oxysporum f.sp. cubense is a major factor limiting commercial banana production in Malaysia. Field evaluation of banana plants for Fusarium wilt disease has not been effective as the infection period is slow and other variables such as distribution of inoculum concentration is difficult to control. Therefore, a study was carried out to develop a semi-qualitative bioassay for early and rapid susceptibility tests against Fusarium wilt disease in banana plantlets. The induction of sporulation and germination of Foc race 1 (VCG 01217) were firstly determined. Then, the effect of inoculum density of fungal spores on the magnitude of infection in Pisang Rastali (AAB) plantlets was carried out. The concentration of hydrogen peroxide (H₂O₂) and other enzyme activities such as phenylalanine ammonia lyase (PAL), chitinase, glucanase, peroxidase (PER) and polyphenol oxidase (PPO) in infected roots of banana plants were determined to relate to the levels of tolerance or susceptibility to Fusarium wilt disease. Using similar conditions, transgenic Pisang Rastali (AAB) was tested to investigate the effectiveness of this bioassay. Hydrogen peroxide and phenylalanine ammonia lyase is the most sensitive compound and enzyme detectable after inoculated with Fusarium spores. The chitinase, β-1,3-glucanases, peroxidase and polyphenol oxidase enzymes activity of transgenic plants were higher than untransformed plantlets. The results obtained indicate that the use of these biochemical parameters has the potential to predict the levels of tolerance or susceptibility to Fusarium wilt disease in other banana cultivars.     

西瓜枯萎病的研究进展

西瓜枯萎病是西瓜栽培中常见的土传病害,由尖孢镰刀菌西瓜专化型侵染所致,已成为限制西瓜生产的主要因素之一。本文对西瓜枯萎病病原菌、西瓜抗枯萎病机理及其防治方法的研究进展进行了综述,并提出利用植物间的化感作用寻求抑菌植物并采用合理的间、轮、套作技术是一项安全控制西瓜枯萎病的有效措施。     

Cold Storage of Strawberry Plants

Abstract

Cold storage has not only been a good method to overwinter strawberry plants safely and to compensate for the lack of natural chilling. Initially cold stored plants were used for early spring cropping only. Meanwhile this technique has become a normal commercial practice among growers in central Europe and has given them the opportunity to extend the strawberry production season from July until January. Cold stored waiting bed plants have been used since the early seventies in The Netherlands and Belgium and currently represent an important part of strawberry production. These sixty-day-plants are planted mainly outdoors in the soil for a production from July until September. More recently waiting bed plants have gained popularity in the UK, Germany and northern Italy to extend the season. Alternatively in France and Germany cold stored runner (A+) plants are traditionally being used for a summer production outdoors followed by a spring crop. During the last decade module or tray plants have gained popularity for autumn cropping on substrate culture in plastic tunnels and greenhouses. During the most recent years the programmed “out of season” production of strawberries has become more important in several European countries. Intensive research has been going on concerning the improvement of the growing techniques and quality of plant material and cold Storage conditions.     

西瓜重组自交系群体的AFLP 分子图谱构建

 以可溶性固形物含量高、皮薄、感枯萎病的栽培西瓜自交系( Citrullus lanatus var. lanatus)97103 和可溶性固形物含量低、皮厚、抗病的野生西瓜种质( Citrullus lanatus var. citroides) PI296341 为亲本构建获得F₂S₇ 的重组自交系群体, 通过AFLP 技术对该群体进行扩增, 建立了一个包括150 个标记组成的分子图谱。该图谱包括17 个连锁群, 覆盖基因组范围1240.2 cM, 两个标记间的平均图距为8.3 cM。图谱的建立对于西瓜高密度遗传图谱的构建、重要农艺性状的QTL 定位以及重要基因的图谱克隆均具有重要的参考价值。     

黑龙江省西瓜枯萎病病原菌鉴定及生物学特性研究

西瓜枯萎病是一种世界性的严重的土传真菌病害。在黑龙江省西瓜生产中,每年因枯萎病导致西瓜减产10%左右。试验结果表明:供试的8个枯萎病菌株形态均为典型的尖孢镰刀菌;致病菌株最适生长条件为温度26℃,pH值=7,PDA培养基。     

Phloem unloading follows an extensive apoplastic pathway in developing strawberry fruit

Summary

Strawberry (Fragaria × ananassa) is widely used as a model for fleshy fruit biology research; nevertheless, the pathway of phloem unloading in strawberry fruit remains unknown. Using transmission electron microscopy (TEM) and the symplastic tracer, carboxyfluorescein, the phloem unloading pathway was studied in ‘Akihime’ strawberry fruit from post-anthesis to the ripening stage. Ultrastructural analysis showed that many plasmodesmata existed between the sieve element cells (SEC) and the companion cells (CC), but plasmodesmata were absent between the sieve element cell – CC complexes and their surrounding phloem parenchyma cells (PPCs). Interestingly, an abundance of plasmodesmata was observed between parenchyma cells. Imaging of carboxyfluorescein unloading revealed that the dye was confined only to the phloem vascular bundles in developing receptacles. In conclusion, the results obtained from the present study indicate that sugar unloading from the phloem occurs through an apoplastic pathway. Post-phloem transport of sugar then follows a symplastic pathway in strawberry fruit.     

Breeding Strawberry for Higher Phytochemicals Content and Claim It: Is It Possible?

ABSTRACT

Commercial strawberries (Fragaria × ananassa) are one of the most investigated berries for nutritional and nutraceutical properties. A strawberry breeding program, including inter-specific back-crosses, is now producing new genotypes with increased vitamin C, folates, and phenols combined with important commercial traits. The release of new cultivars with a high content of bioactive compounds, which may contribute to health, wellness, and reduced disease risk, is expected from this program. The ultimate goal is to properly obtain and integrate new scientific knowledge from genetic, agronomic, and biomedical studies that may bring acceptance from food agencies for specific health claims on new strawberry cultivars.     

苦瓜枯萎病抗性鉴定与抗性遗传规律研究

 以4 份田间抗性水平不同的苦瓜为材料,探讨了适用于苦瓜苗期人工接种枯萎病菌的抗性 鉴定方法;以此为基础,对来自国内外的43 份苦瓜种质资源进行了抗源筛选,以其中的抗病亲本‘0417’ 和感病亲本‘472113’为材料,研究了苦瓜对枯萎病抗性的遗传规律。结果表明,直接水培接种法是较适 合于苦瓜苗期枯萎病抗性鉴定的方法,适宜的接种菌液孢子浓度为4 × 106 · mL-1。在苦瓜种质资源中,枯 萎病抗源普遍存在,尤以野生种或半栽培种抗病性较强。苦瓜枯萎病抗性受单一显性核基因控制,其广 义遗传力为90.78%。     

生防菌+恶霉灵最优组合的筛选及对苦瓜枯萎病的防治效果研究

苦瓜枯萎病是由尖孢镰孢菌苦瓜专化型（Fusarium oxysporum f. sp. momordicae）侵染引起的一种土传病害，目前市场上缺乏防治效果较好的农药或生防菌剂。为了更好地防治苦瓜枯萎病，通过盆栽试验筛选出绿针假单胞菌（Pseudomonas chlororaphis）G5 与恶霉灵复配施用的最优组合，并在苦瓜枯萎病发病样地对盆栽试验筛选出的最优组合进行防效验证。试验结果表明：菌药组合B+0.75Hym（1×10⁹ cfu · mL^-1 G5 菌悬液+187.5 mg · L-¹ 恶霉灵）处理对盆栽苦瓜枯萎病的防病效果为81.60%，明显高于其他处理；同时该组合对苦瓜幼苗的促生作用最为明显。接种苦瓜枯萎病菌后，菌药组合B+0.75Hym的苦瓜叶片中PAL、PPO、POD 防御酶活性较高。田间防效验证试验中苦瓜苗移栽30、60 d 后菌药组合B+0.75Hym 对苦瓜枯萎病的防治效果较高，分别达到了52.59%、32.13%，且苦瓜产量也高于其他处理。表明盆栽试验筛选出的菌药最优组合B+0.75Hym 不仅能够降低农药的使用量，而且能够有效防治苦瓜枯萎病，提高苦瓜产量，有一定的生产实用价值。     

缺钾胁迫对连作草莓生长和土传病害的影响

 以草莓‘红颜’品种为试材,设缺K（K+ 48.75 mg · L^-1,缺量水平）、1/2K（K+ 415.58 mg · L^-1, 半量水平）和全量K（K+ 782.41 mg · L^-1,正常水平）营养液处理,对缺钾胁迫与草莓连作障碍的关系进 行了探讨。结果表明,缺钾处理显著抑制二茬草莓植株地下部分和地上部分的生长,其中缺K 的长势最 弱,1/2K 比全量K 的长势强;缺K 二茬植株根系分泌物对草莓组培苗生长有显著影响,表现为低浓度（1%、 2%）根系分泌物促进幼苗侧根和茎叶生长,高浓度（4%）则抑制根系生长。不同浓度钾营养液处理的三 茬植株分别接种尖孢镰刀菌和大丽轮枝菌后,在不同时期比未经过连作的基质对照发病都严重。缺K 三 茬植株发病最重,接菌后10 d 时病情指数就高达75,全量K 三茬植株发病次之,1/2K 三茬植株发病相 对较轻。因此,缺K 环境会加重草莓的连作障碍,适宜的K 量对草莓连作障碍的防治有重要意义。     

铜、锌元素对香蕉枯萎病的防治效果与机理

 为寻找香蕉枯萎病防治措施,通过盆栽试验和室内试验,研究铜、锌（EDTA-Cu、EDTA-Zn）对香蕉尖孢镰刀菌（Fusarium oxysporum f. sp. cubense）生理特性的影响,以及锌与拮抗菌21号（SQR21^＃,多粘芽孢杆菌Paenibacillus polymyxa）配合使用对香蕉枯萎病的防治效果。结果表明：（1）用尖孢镰刀菌培养得到的粗毒素处理香蕉幼苗96 h后,对照植株萎蔫严重,呈枯死状,添加EDTA-Cu或EDTA-Zn,显著减轻了粗毒素对香蕉幼苗的伤害。（2）与对照相比,添加EDTA-Cu或EDTA-Zn均显著增加了香蕉尖孢镰刀菌小型分生孢子数量和真菌生物量,但显著降低了镰刀菌酸的产量,分别降低73%和96%。（3）盆栽试验中,加锌（ZnSO₄ · 7H₂O）处理显著降低了香蕉枯萎病的病情指数。其中锌与拮抗菌21号菌同时使用防治效果最好,处理75 d病情指数比直接接菌处理降低62%。（4）21号菌显著降低了香蕉根际土壤尖孢镰刀菌数量,与直接接菌处理相比降低了18%,锌与21号菌同时使用显著增加了尖孢镰刀菌数量,比直接接菌处理增加了30%。上述结果表明,锌离子可能通过降低香蕉尖孢镰刀菌镰刀菌酸的产量以及增强拮抗菌21号菌的生防活性来有效降低香蕉枯萎病的发病率。     

Factors affecting the quality and in vitro germination capacity of strawberry pollen

Summary

Poor pollen quality and germination capacity curtails early yield in strawberry. The aim of this study was to establish a reliable method for in vitro assessment of strawberry pollen germination ability and to investigate further the effects of photoperiod and gibberellin on pollen germination and quality. In the first part of the study, pollen from seven strawberry cultivars (Chandler, Selva, Tudla, Camarosa, Eris, Pajaro and Irvine) was collected and its germination capacity and incidence of deformed pollen grains assessed in vitro using the hanging-drop technique. Highest germination rates, in ‘Selva’, were observed in a nutrient medium of 10% sucrose. Addition of calcium nitrate to the medium decreased the germination percentages of all cultivars. There was no significant difference, on average, between the germination rate at 20° and 25°C. Genetic factors affected the incidence of deformed pollen grains significantly, with ‘Pajaro’ showing the highest percentage (76%). In the second part, groups of young strawberry plants, cultivar Seascape, grown either under natural early spring conditions or under long-day or short-day conditions were sprayed once with GA₃ at 0, 50, or 200 mg l^–1. Pollen germination and deformation and stamen length were assessed three months later. In plants of the first group, GA₃ at 50 mg l^–1 increased pollen germination and decreased the incidence of deformed pollen grains, while GA₃ at 200 mg l^–1 decreased pollen germination without affecting the formation of deformed pollen grains. Plants of the second group showed a higher rate of pollen germination under long than under short days. GA₃ at 200 mg l^–1 decreased pollen germination under either short- or long-day conditions compared with the controls but doubled the percentage of deformed pollen only under short days. Stamens in control plants grew four times as long under long- than short-day conditions. GA₃ did not affect stamen length under long days but significantly enhanced their growth under short days.