Phenotypic characterisation of Phaeoacremonium and Phaeomoniella strains isolated from grapevines: enzyme production and virulence of extra-cellular filtrate on grapevine calluses

Extra-cellular enzyme production of different Phaeoacremonium spp. and Phaemoniella chlamydospora isolates were used to assay the possibility of inter-specific characterisation. Isolates of Phaeoacremonium aleophilum, Phaeoacremonium angustius, P. viticola and Ph. chlamydospora were grown on solid media and the activities of extra-cellular amylases, lipases, proteases, cellulases, xylanases, laccase, polygalacturonase, pectate lyase, lignin peroxidase, manganese peroxidase, urease and chitinase were assayed. Phaeoacremonium species showed activities of a larger number of enzymes and also enzyme activity was frequently higher suggesting that Phaeoacremonium can be more virulent. To assay if the produced extra-cellular enzymes could reflect the virulence capacity of the two genera, calluses of Vitis vinifera L. (cvs. Baga and Maria Gomes) and of a rootstock (R3309) were inoculated with filtrated culture liquid medium of three isolates of Ph. chlamydospora and one of P. angustius. Filtrates from all strains decreased callus growth and membrane integrity, while soluble protein content of calluses decreased with the strains CAP 054 and 1AS. P. angustius (CAP 054) induced the more severe symptoms in all genotypes. Water content decreased together with an increase of osmolality in both cultivars but not in rootstock suggesting that osmorregulatory capacity is more affected in cultivars. Data show that: (1) Phaeoacremonium and Phaeomoniella genera have different patterns of extra- cellular enzymatic production; (2) these fungi produce extra-cellular compound(s) that induce(s) senescence symptoms in plant cells inhibiting callus proliferation; (3) among the strains tested in plant calluses the most virulent isolate (CAP 054) also produced higher amounts of some extra-cellular enzymes; (5) rootstock calluses were less sensitive to inoculation than grapevine calluses.     

Response of Vitis vinifera L. plants inoculated with Phaeoacremonium angustius and Phaeomoniella chlamydospora to thiabendazole,resveratrol and sodium arsenite

The effect of some pesticides (sodium arsenite, thiabendazole and ziram) and the natural phytoalexin (resveratrol) on mycelial growth of Phaeomoniella chlamydospora and Phaeoacremonium angustius was studied. Several strains of these species were grown on malt extract agar (MEA) plates containing different concentrations of inhibitory compounds and colony diameters were measured. While sodium arsenite and ziram had little effect on the growth of both species, thiabendazole inhibited colony growth, at minimum concentrations of 6 μM for Ph. chlamydospora and 15 μM for P. angustius. Resveratrol at concentrations equal to or grater than 867 μM also inhibited colony growth of both species. To assay the effect of these substances on plant response to infection, in vitro grapevines were inoculated with Ph. chlamydospora or P. angustius spores and were grown in the presence of sodium arsenite (0–30 μM), thiabendazole (0–30 μM) or resveratrol (0–876 μM). Infected untreated plants and sodium arsenite-treated plants developed symptoms of senescence (reduced growth, increased membrane lipid peroxidation, and decreased chlorophyll content and fluorescence). In contrast, infected plants treated with thiabendazole (30 μM) or with resveratrol (876 μM) showed similar characteristics of fresh weight, malondialdehyde accumulation and chlorophyll fluorescence to those of uninfected plants. These results are promising with respect to the use of thiabendazole-containing pesticides as alternatives to currently used pesticides for control of esca in vines. Results also suggest that the presence of resveratrol in grapevines may be useful to induce resistance to these fungi.     

Growth and flower quality of four Rosa hybrida L. cultivars in response to propagation by stenting or cutting in soilless culture

Performance of four Rosa hybrida L. cultivars (‘African Dawn’, ‘Ilios’, ‘Maroussia’ and ‘Soprano’) was evaluated. They were grown either on their own roots or grafted (stenting) onto Rosa canina L. ‘Inermis’ rootstock in a polyethylene greenhouse with hydroponics system. Parameters of plant growth and flower quality were investigated for two successive harvesting years (2005 and 2006). Results indicated that, all the cultivars were superior for most of the parameters studied when grafted onto rootstock compared to being on their own roots. Flowering stem fresh weight and diameters, flower fresh and dry weight, flower diameter and length, petal number, leaf chlorophyll content and quality index were higher in grafted plants compared to those propagated by cuttings. However, highest flowering stem length and number were observed in plants propagated by cutting, although not significant as compared with stenting method.     

The responses of photosynthetic capacity,chlorophyll fluorescence and chlorophyll content of nectarine (Prunus persica var. Nectarina Maxim) to greenhouse and field grown conditions

Three nectarine (Prunus persica var. Nectarina Maxim.) cultivars grown under solar-heated greenhouse and open-field in northwest China, were tested to evaluate their photosynthetic and chlorophyll fluorescence response to both growth conditions, and whether nectarine plants acclimate to the solar-heated greenhouse growth condition. Comparisons of light-saturated photosynthetic capacity (Amax) and CO₂-saturated photosynthetic capacity (RuBPmax) indicated that each cultivar (Z, Zao-Hongzhu; H, Hua-Guang; Y, Yan-Guang) maintained similar rates of light-saturated and CO₂-saturated carbon assimilation when grown in both conditions. The curve of diurnal variation of net photosynthetic (P_N) rate showed double peaks in open-field but single when grown in greenhouse. Compared with open-field-grown plants, a significant increase of daily average P_N was found in Z but decreased in Y in greenhouse. The diurnal variation of F_v/F_m indicate that plants grown in greenhouse experience less photoinhibition than in open-field condition. A reduction in chlorophyll (chl) a/b ratio in leaves of greenhouse grown plants with significant increase in chlorophyll (chl) b content were obtained. The results suggest that some nectarine cultivars have the ability to acclimate to the solar-heated greenhouse growth condition.     

Determination of grafting compatibility of grapevine with electrophoretic methods

This study was carried out to determine the efficiency of electrophoretic methods in predicting graft incompatibility of grape cultivars with American rootstocks. Three isoenzyme systems (peroxidase, PER; esterase, EST; acid phosphatase, AcPH) and total protein profiles were obtained in 15 grape cultivars (Vitis vinifera L.) and 12 American rootstocks. Compatibility levels were determined by the band similarities. Field compatibilities were also calculated. Results showed that incompatibility exists between different cultivar–rootstock combinations. AcPH and total protein profiles of the cultivar–rootstock combinations could be suggested to use for forecasting graft incompatibility.     

Comparison of three pea cultivars (Pisum sativum) regarding their responses to direct and bicarbonate-induced iron deficiency

The aim of this work was to explore leaf characteristics underlining the difference in the sensitivity of pea cultivars (cv. Kelvedon, Douce and Lincoln) to Fe deficiency. Plants were grown in a greenhouse under controlled conditions in continuously aerated solution. Three treatments were used: 30 μM Fe (+Fe), 0 μM Fe (−Fe); direct deficiency and 30 μM Fe + 10 mM NaHCO₃ (+Fe+Bic); indirect deficiency for 12 days. Growth parameters, iron status, potassium content, chlorophyll fluorescence and photosynthetic capacity were studied. Our results showed that Fe deficiency led to a significant decrease of chlorophyll index (SPAD readings) and bivalent iron content in all Pisum sativum cultivars. The lower reduction was observed in Fe-deficient plants of Kelvedon and Douce. In addition, shoot length and whole plant dry weight were not affected by Fe deficiency in the latter cultivars. Both tolerant cultivars showed higher accumulation of potassium content in their leaves compared with the sensitive one. Moreover, both chlorophyll fluorescence ratios (F_v/F_m and F_v/F₀) were significantly decreased in all cultivars under both Fe deficiency treatments. The photosynthetic electron transport activity was reduced in the sensitive cultivar, especially in the absence of iron. The adverse effect of bicarbonate-induced Fe deficiency on the above mentioned parameters were more pronounced than that of the direct one. The capacity of both tolerant cultivars to preserve adequate chlorophyll synthesis, photosynthetic capacity and plant growth under iron-limiting conditions is related to the suitable nutrition of their leaves in ferrous iron, due to (at least partially) their higher potassium content.     

Antioxidant and stomatal responses of grapevine (Vitis vinifera L.) to boron toxicity

Although of considerable agronomic importance, our understanding of B toxicity mechanism in plants is still not completely understood, and remains an open question. Therefore, we investigated the effect of increasing levels of B (0, 10, 20 and 30 mg kg⁻¹) on the growth, boron (B) concentrations, stomatal resistance, lipid peroxidation (MDA), membrane permeability (MP), lypoxygenase activity (LOX), proline (PRO) and H₂O₂ accumulation, and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of grapevine (Vitis vinifera L. cv. Kalecik Karasi) grafted on 5BB rootstock (V. berlandieri × V. riparia) was investigated. Applied toxic levels of B significantly reduced leaf and root growth and increased the B concentration of the leaf, and stem, bark and root of rootstock. In the all B levels leaf tissues of grapevine accumulated more B than that of the other plant parts. In order to restrict excessive uptake of B, stomatal resistance of the leaves increased especially at high B treatments (20 and 30 mg kg⁻¹). The concentrations of H₂O₂, MDA and membrane permeability were increased as the result of B toxicity while proline and the activity of lypoxygenase were decreased. Compared with control plants, the activities of SOD and CAT were increased by B treatments while the activity of APX was decreased. To our knowledge, this is the first report that B toxicity elevated the antioxidant enzymes to protect the membrane functions from reactive oxygen species (ROS) injury in grapevine and it was hoped that this study would provide a basis for developing strategies for reducing the risks associated with B toxicity.     

Differential tolerance to iron deficiency of citrus rootstocks grown in nutrient solution

We studied the effects of Fe deficiency on physiological parameters of citrus rootstocks grown in nutrient solution. Three 4-week old rootstocks (‘Troyer’ citrange – Citrus sinensis (L.) Osb. × Poncirus trifoliata (L.) Raf., Citrus taiwanica Tan. and Shim., and ‘Swingle’ citrumelo – Poncirus trifoliata (L.) Raf. × Citrus paradisi Macf.) were grown in nutrient solutions with 0, 5, 10, 15 and 20 μmol Fe dm⁻³. Calcium carbonate (1 g dm⁻³) was added to all solutions to mimic the natural conditions in calcareous soils. For each rootstock, shoot length, number of leaves, and root and shoot dry weights were measured at the end of experiment. Chlorophyll concentration was estimated using a portable SPAD-502 meter calibrated for each rootstock. The amount of nutrients (P, K, Mg, Ca, Fe, Zn, Mn, and Cu) was determined in shoots. Chlorophyll fluorescence parameters (F₀: basal fluorescence; F_m: maximum fluorescence; F_v = F_m − F₀: variable fluorescence) were measured with a portable fluorimeter. ‘Troyer’ citrange rootstock was the most tolerant to Fe deficiency. These plants grew more and accumulated more chlorophyll and nutrients than the others in the presence of low levels of Fe (10 μmol Fe dm⁻³). ‘Swingle’ citrumelo plants needed 20 μmol Fe dm⁻³ in the nutrient solution to secure adequate growth. ‘Taiwanica’ orange rootstock had an intermediate behaviour, but could be distinguished from ‘Troyer’ citrange based on fluorescence parameters, since there was a variation in the basal fluorescence in the former, whereas in ‘Troyer’ citrange the basal fluorescence was not affected by the supply of Fe.     

Interaction of photoperiod and temperature in the control of growth and dormancy of Prunus species

Growth and dormancy induction of seedlings or micropropagated plants of three Prunus species were studied under controlled environment conditions. All the species tested, P. cerasus L. and P. insititia L. (two cultivars each), and P. avium L. were insensitive to photoperiod at high temperature and maintained continuous growth in both 10 and 24-h photoperiods at 21 °C. At lower temperatures, however, growth was controlled by the interaction of photoperiod and temperature, the species and cultivars varying somewhat in their responses. At 9 °C growth cessation was induced regardless of day-length conditions in the plum rootstocks ‘St. Julien A’ and ‘Weito’ as well as in the sour cherry rootstock ‘Weiroot’, whereas in the sour cherry rootstock ‘Gisela 5’ growth cessation took place in short day (SD) only. At intermediate temperatures (12 and 15 °C) growth cessation occurred in SD only in both sour cherry cultivars. In P. avium seedlings on the other hand, growth cessation in SD was only induced at 9 °C, continuous but reduced growth taking place also in SD at all higher temperatures. Growth rates increased progressively with increasing temperature under long day (LD) conditions in all species, and this was associated with increased internode length in LD compared with SD conditions. Production of new leaves was unaffected by photoperiod at high temperature, but was higher in LD than in SD at lower temperatures. After growth cessation at low temperature the plants developed winter buds and became dormant also in LD conditions. These results demonstrate that, like several species of the Pomoidae subfamily of the Rosaceae, these Prunus species are insensitive to short photoperiods at relatively high temperatures. However, the photoperiodic response of the Prunus species is highly temperature dependent, and the transition temperatures for shifts in the photoperiodic response mode vary among the species.     

Screening of vincristine yield in ex vitro and in vitro somatic embryos derived plantlets of Catharanthus roseus L. (G) Don.

Catharanthus roseus L. (G.) Don. (Apocynaceae) is an important dicotyledonous medicinal plant as it is the sole source of vincristine and vinblastine that are used against a variety of cancers. Quantitative estimation of vincristine was carried out using high performance liquid chromatography (HPLC) in various in vitro grown tissues; calluses (embryogenic and non-embryogenic callus), embryogenic stages (proliferated, matured and germinated embryos), somatic embryo derived plantlets (leaf, root and whole plant) and leaves of ex vitro developed plantlets. The yield in those in vitro and ex vitro-developed tissues was monitored for 30 weeks. Except at an early lag period, vincristine production was detected up to 20–25 weeks old plant samples. Vincristine content was very high in leaf callus and germinated embryos. Leaves of in vitro raised plants showed higher amount of vincristine when compared to ex vitro-developed leaves of similar age. Vincristine production was tissue specific and age dependent that was discussed in detail in this present communication.     

山葡萄应答霜霉病侵染过程中叶绿素荧光成像的变化

以抗霜霉病的‘左山一’和易感病的‘双丰’山葡萄（Vitis amurensis Rupr.）为试材,离体叶片接种霜霉病菌后观察叶绿素荧光成像及参数变化。结果显示：叶绿素荧光成像系统可在接种霜霉病菌3 d时观察到病斑;霜霉病侵染叶片组织会显著改变叶绿素荧光参数;接种7 d时病斑与不接种对照相比,抗病品种‘左山一’Fv/Fm、ФPSⅡ、Y（NPQ）与Y（NO）的变化幅度（–73.42%、–100%、–49.64%、+ 3285.21%）均大于易感病品种‘双丰’的变化幅度（–22.98%、–28.17%、+ 5.62%、+ 26.18%）,‘左山一’病斑周围组织的ФPSⅡ与rETR高于对照,而‘双丰’低于对照。由此可见,‘左山一’能够较早形成枯斑,快速改变病斑处的荧光参数,并提高病斑周围组织的ФPSⅡ与rETR值,从而增强对霜霉病的抗病性。因此,病斑周围组织的ФPSⅡ与rETR可以作为初步筛选山葡萄抗霜霉病种质的指标。     

Propagation of Lilium hybrids. II. Production of plantlets from bulb-scale callus cultures for increased propagation rates

A method has been developed for the large-scale propagation of lilies from callus cultures. Bulb scales, being available at all times, are an ideal source of explants. Callus was induced throughout the annual cycle of all the 12 Oriental hybrid cultivars tested, by treating the bulb scales with a combination of 5 μM BA and 5 μM 2,4-D. Once initiated, this callus grew vigorously on media lacking exogenous growth substances. Callus induction by BA and 2,4-D, and the subsequent growth of such callus in the absence of exogenous growth substances, occurs within a broad range of cultivars and species within the genus. The callus could be maintained on a medium lacking ammonium salts, but the maximum growth rate was obtained at 10 mM NH₄NO₃. At low (0.2 mM) or zero levels of NH₄NO₃, light as compared with darkness was inhibitory to growth.The callus maintained its capacity for organogenesis. Maximum production of plantlets was obtained in continuous light on agar medium with 0.5 μM NAA.Potentially, the successive use of liquid and agar cultures can produce 6 × 10¹² plants per year from 1 g (dry wt.) of callus. Plantlets derived from callus were consistently diploid and could be readily transferred to soil.     

In vitro testing of strawberry resistance to Verticillium dahliae and Phytophthora cactorum

The effects of culture filtrates and homogenates of Verticillium dahliae and Phytophthora cactorum on in vitro growth and development of strawberry shoots of cvs. Elsanta, Real and Senga Sengana were investigated. The filtrates of fungal cultures as well as filtrates of homogenated mycelia did not affect strawberry shoot growth and development, whereas inoculation with mycelia of V. dahliae and P. cactorum resulted in leaf yellowing, growth inhibition, inhibition of root formation, and after several days, the death of infected plants. However, fungal growth on the media that were used was irregular and the infection rate of individual plants was very variable.Mycelial homogenates affected growth and development of strawberry shoots in a similar way to that of an intact mycelium. Because the homogenate was distributed evenly in the culturing medium, the effect was uniform and thus possible to quantitate. It was also possible to differentiate a pathogen’s inoculum potential by adequate dilution of the homogenate. The best effect was obtained with V. dahliae. Fungal homogenate inhibited root formation and shoot growth, caused leaf necrosis and death of the plants after 7–8 weeks. The reaction of the cultivars tested was similar to their sensitivity to verticillium wilt in the field.P. cactorum affected in vitro strawberry shoot growth and development in a similar way to V. dahliae, but the effect was not cultivar-dependent. Preliminary tests showed that the method developed is useful for selection of somaclonal variants resistant/tolerant to infection with these pathogens.     

Novel organized growth and somatic variation of Nicotiana bonariensis protoplast-derived colonies: Transmission to regenerated plants

Mesophyll protoplasts isolated from leaves of axenic shoot cultures of Nicotiana bonariensis underwent sustained cell division and concomitant novel cellular organizational patterns when cultured in liquid Murashige and Skoog medium (1962) containing 2.0 mg 1^?1 naphthaleneacetic acid (NAA), 0.5 mg 1^?1 6-benzylaminopurine (BA) and 9% mannitol. The novel patterns were leaf-like and embryo-like structures which resumed unorganized callus growth prior to shoot regeneration. In addition, the presence or absence of anthocyanin and of chlorophyll pigmentation in the protoplast-derived colonies was also observed. The variation in either presence or absence of anthocyanin in protoplast-derived colonies is restored as anthocyanin synthesis in the regenerated plants. However, the variation for chlorophyll pigmentation observed at the colony stage was transmitted as differences in morphology in the regenerated plants. The mode of shoot regeneration of N. bonariensis protoplasts and the potential value of somatic variants are discussed.     

Growth of Vitis vinifera L. and Vitis aestivalis Michx. as Affected by Temperature

Abstract

Four European (Vitis vinifera L.) winegrape cvs., ‘Semillon’, ‘Pinot Noir,’ ‘Chardonnay’, and ‘Cabernet Sauvignon’, and one American (Vitis aestivalis Michx.) winegrape cv. ‘Cynthiana’, were subjected to three temperature regimes in growth chambers set at 20/15°C, 30/ 25°C, or 40/35°C, for 16/8 hr day/night to determine the influence of temperatures on vine growth and development. In general, the best temperature for shoot and root growth 28 days after temperature treatments was 20/15°C for ‘Semillon’, ‘Cabernet Sauvignon’, and ‘Cynthiana’, and 30/25°C for ‘Pinot Noir’ and ‘Chardonnay’. Although 40/35°C reduced number of leaves, shoots, tendrils, and internodes, total leaf area (LA), and total shoot biomass of all the cultivars, the reduction was more pronounced in ‘Cynthiana’ than in the European cultivars. The average reduction in number of leaves at 40/35°C for the European cultivars was 47%, compared with 92% for ‘Cynthiana’. The two types of grapes adapted differently to high temperature. Shoot growth in the European cultivars continued under high temperature, whereas growth ceased in ‘Cynthiana’. Roots of ‘Cynthiana’, however, were less susceptible to the adverse effect of high temperatures than were the shoots. This study shows that the European cultivars were relatively more tolerant to high temperature than the American cultivar and they have a potential for production of wine in the climate of south central Kansas.     

High-frequency somatic embryo production from unfertilized ovules of grapes

Somatic embryos were produced in large numbers from cultured, unfertilized ovules of Vitis vinifera, cultivars ‘Cabernet Sauvignon’ and ‘Grenache’, and of the hybrid grape ‘Gloryvine’ (V. vinifera × V. rupestris). Callus of nucellar origin was produced by culturing the ovule explants initially in Nitsch medium containing 5 μM 2,4-dichlorophenoxy acetic acid (2,4-D) or 5 μM β-naphthoxyacetic acid (NOA) plus 1 μM benzyladenine (BA), and then in a medium supplemented with NOA (10 μM) plus BA (1 μM). Embryos were produced when callus was transferred to basal medium containing no auxin or cytokinin. Secondary and tertiary embryos were formed by budding of primary somatic embryos. Prolonged culture of ovular callus in NOA (10 μM) plus BA (1 μM) gave rise to cell aggregates which developed into free-floating roots when transferred to basal medium.     

Physiological and biochemical responses for two cultivars of Pisum sativum (“Merveille de Kelvedon” and “Lincoln”) to iron deficiency conditions

The aim of this work was to compare the tolerance and the physiological responses to Fe deficiency of two Pisum sativum cultivars (“Merveille de kelvedon” and “Lincoln”) commonly cultivated in Tunisia. We studied the effects of Fe deficiency on: (i) chlorophyll content, relative growth rate (RGR) and Fe status, (ii) rhizosphere acidification, (iii) changes under Fe-deficient conditions in the activities of two root enzymes, the first related to the proton extrusion (H⁺-ATPase) and the second to iron reduction mechanism (Fe(III)-chelate-reductase: FCR). Three treatments were used: C, control, complete nutrient solution (CNS) containing 30 μM Fe; DD, direct deficiency, CNS without iron; ID, indirect deficiency, CNS containing 30 μM Fe + lime. Fe deficiency led to a significant decrease of chlorophyll content in both cultivars. The below reduction was observed in Fe-deficient plants of Merveille de Kelvedon. In addition, relative growth of shoots and whole plant was not affected by Fe deficiency. H⁺-ATPase and FCR activities were more stimulated in Merveille de Kelvedon than in Lincoln, under DD and ID Fe deficiency. The capacity of this cultivar to maintain plant growth and to preserve adequate chlorophyll synthesis under iron-limiting conditions is related to its better Fe-use efficiency, in addition to its high acidification and root reducing capacities. This allows us to suggest that Merveille de Kelvedon is more effective in overcoming Fe deficiency than Lincoln.     

嫁接对苦瓜在水渍条件下的产量及某些生理特性的影响

以有棱丝瓜、无棱丝瓜、黑籽南瓜和瓠瓜作砧木,苦瓜作接穗进行嫁接栽培试验.有棱丝瓜作砧木插接法的嫁接成活率最高,达92.66%.有棱丝瓜和黑籽南瓜作砧木的苦瓜嫁接苗比自根苗提早进入开花结果期.水渍条件下两种砧木嫁接植株比自根苗植株分别增产36.5%和 33.7%,同时以有棱丝瓜作砧木的嫁接植株的叶绿素、氮、磷、钾含量和伤流量以及植株体内保护性酶(SOD、POD、CAT)的活性均大于自根苗植株和以黑籽南瓜作砧木的嫁接植株,而膜脂过氧化产物(MDA)的含量最低.     

石油烃污染对三种灌木植物生理及叶绿素荧光参数的影响

通过盆栽试验,研究了不同浓度的石油烃胁迫对连翘、大花水桠木、紫穗槐生理及叶绿素荧光特性的影响。结果表明:在石油烃胁迫下,3种植物的MDA含量、电导率和叶绿素荧光参数与对照相比均有显著变化。3种植物的生理指标和叶绿素荧光参数的变化存在种间差异。石油烃含量在3 g/kg土和6 g/kg土2个处理中,连翘的生理指标和叶绿素荧光参数的变化幅度要小于大花水桠木和紫穗槐,对石油烃胁迫的抗性更强;石油烃含量在12 g/kg土时,3种植物的生长均受到最大抑制。     

Pathogenicity of dried-shrink disease and evaluation of resistance in a germplasm collection of sea buckthorn (Hippophae L.) from China and other countries

Sea buckthorn (Hippophae L.) is a woody, dioecious plant that can be grown in dry and poor soil conditions. It has recently received world-wide attention as a new berry crop with a very high nutritional value and unique medicinal properties, as well as a means of combating soil erosion. A major problem is, however, dried-shrink disease (DSD), which destroys sea buckthorn plants and halts commercial production. In this study, we investigated symptoms and pathogenicity of DSD, isolated and identified pathogens using a combination of morphology and ITS sequences, and evaluated the disease index (DI) of different cultivars in the field. DSD infection causes isolated yellowing of plant tissues, and as the disease develops the bark putresces, dries and shrinks, and finally the plant dies. DSD infects older plants (>3 years), often at the plant base. Death of plant parts above the infected area does not influence root vitality, and a new plant can therefore be regenerated. Combining morphological characters and ITS sequences, we isolated and identified four fungal pathogens causing DSD, including Fusarium acuminatum, F. oxysporum, Fusarium camptoceras and Phomopsis spp. DI values for 27 cultivars ranged from 0 to 10.4. About half of the cultivars were regarded as resistant (DI < 3.2) to DSD, and half as susceptible (DI > 6.7). Cultivar ‘Zhongguoshaji’ (DI = 4.2) showed an intermediate level of DSD resistance. Our data provides basic information for further studies of the mechanism of pathogenicity, and for breeding of DSD-resistant cultivars.