Histopathology of red crown rot of soybean

Histopathological analyses of red crown rot (RCR) of soybean were performed using field-grown and indoor-grown soybean plants. These analyses revealed that soybean plants formed a periderm to prevent pathogen invasion. When a break formed in the periderm, an additional periderm newly differentiated into the inner cells and prevented pathogen invasion. If the pathogen reached the intravascular tissues, some xylem parenchyma cells died, and the vessels were occluded by gum. Periderm formation and vessel occlusion were observed not only in slightly diseased soybean plants, but also in seriously diseased plants, indicating that both reactions function as part of the defense response against RCR.     

一种值得关注的大豆病害——大豆红冠腐病

大豆红冠腐病是一种为害大豆生产的重要病害,该病害的典型症状是大豆叶片变黄萎蔫,植株枯萎,根系变黑腐烂,茎基部及根系表面产生大量红橙色小点,是病原菌的子囊壳。其致病菌为寄生柱枝孢菌（Cylindrocladiumparasiticum）,有性阶段为冬青丽赤壳菌（Calonectriailicicola）。本文对大豆红冠腐病及其致病菌的文献进行了简要的综述。     

Toxic culture filtrates produced byCalonectria ilicicola, causal agent of red crown rot of soybean

Eleven soybean cultivars with different levels of susceptibility to virulent isolate SG915 ofCalonectria ilicicola were examined for reaction to metabolites produced by the isolate. When the culture filtrate from isolate SG915 was applied to trifoliates from 11 cultivars, cvs. ‘Cajun’ and ‘Asgrow 7986’ exhibited reduced wilting severity. However, there was no correlation between sensitivity to culture filtrate and susceptibility to the fungal isolate. Wilting severity on cv. ‘Riverside 699’ was greatest when trifoliates were treated with culture filtrates from isolates SG915 (highly virulent) and C31 (less virulent). The dilution end-point for culture filtrates of virulent isolate SG915 was determined to be 1:8. Nonautoclaved culture filtrates caused complete wilt of soybean trifoliates after 36 h, but autoclaved culture filtrates demonstrated a reduced ability to wilt leaves. Electrolyte leakage from treated leaf tissues increased over time regardless of the concentrations of culture filtrate tested. The greatest electrolyte losses were observed during the initial 30 min incubation of leaf tissues. The highest concentration of culture filtrate (50%, v/v) induced more electrolyte loss than the low concentration (10%, v/v) or control. These results suggest that toxic metabolites ofC. ilicicola may be involved in disease development with leaf symptom expression.     

Studies of the epidemiology and control of tomato stem rot caused by Didymella lycopersici

Pycnidiospores of Didymella lycopersici were capable of inducing stem lesions when used at concentrations as low as two spores per 15-μl droplet, provided the inoculum was placed on wounded tissue and the relative humidity maintained at more than 90%. At c. 75% RH, lesions were not produced even at high spore concentrations and with pre-inoculation stem wounding. Pycnidiospores remained viable when stored for 17 weeks in sterile water and 14 weeks in nutrient solution. Detailed examination of tomato stems with a single lesion indicated that, in some cases, the pathogen may be widely distributed as it was isolated at distances of up to 1000 mm above the lesion and 750 mm below. Experiments on the transmission of D. lycopersici using sciarid flies demonstrated that, although this may be possible, it is probably infrequent in occurrence. None of the fungicides tested for the control of stem lesions were better than the standard benomyl in Actipron, but benomyl in medical-grade liquid paraffin was as good.     

Nodulation during vegetative growth of soybean stage does not affect the susceptibility to red crown rot caused by Calonectria ilicicola

Soybean cultivar Enrei and its derivative lines, non-nodulating En1282 and supernodulating Sakukei 4, were grown in an experiment field naturally infested with the red crown rot fungus, Calonectria ilicicola, to determine whether nodulation elicits the disease. Infection frequency by the fungus invariably increased with time and reached about 100% 6 weeks after sowing. Disease severity was invariably slight until 8 weeks after sowing. At harvest, however, disease severity was lowest in En1282 and highest in Sakukei 4. Enrei was intermediately susceptible. Sakukei 4 produced many more nodules than Enrei, while En1282 completely failed to nodulate. For three other pairs of nodulating and non-nodulating isogenic lines, all non-nodulating lines had lower severity than their nodulating counterparts at harvest. Pot experiments with Enrei and its derivatives revealed that inoculation with Bradyrhizobium sp. did not affect disease severity during the vegetative stage of plant growth, i.e., 6 weeks after sowing. These results suggested that the production of nodules in the vegetative stage is not, at least directly, related to susceptibility to the disease, but physiologic changes after anthesis vary depending on the nodulation traits in the respective soybean lines, resulting in different levels of susceptibility to red crown rot.     

Methyl bromide and PCNB for sclerotium crown rot control in iris

Methyl bromide (MB) at rates of 500, 1000 and 1500 kg/ha, Terraclor 75 WP (PCNB) at 150 and 300 kg/ha, and combinations of the two, were studied for control ofSclerotium rolfsii prior to iris cultivation. Sclerotia buried 10 cm deep in soil were all killed by MB at 500 kg/ha; at greater depths higher doses were required. Bulbs harvested from PCNB- and PCNB + MB-treated plots were healthy; 75% of the bulbs in control plots were infected at harvest. When MB was used alone, the soil became re-infested (2–6% diseased plants). Bromide toxicity, correlated with the MB dose applied, appeared 41/2 months after planting; leaves yellowed and senesced prematurely. MB treatments also reduced bulb size, and residual phytotoxicity was found when the bulbs from treated plots were planted in the following year.     

河西灌区马铃薯茎基腐病的发生规律与防治技术研究

本文首次报道马铃薯茎基腐病在田间表现为立枯型、萎蔫型、根腐型、黄化型4种症状类型,一般在苗期至现蕾期、开花期至结薯期为发病高峰期;明确了河西灌区种植的大多数品种对茎基腐病无明显抗性;发病程度与多种因素有关,灰钙土发病较重,其次为壤土,沙土发病较轻;土壤pH与含水量较高发病重;植株密度较高发病重;连作年限越长发病越重;与油菜、茄科蔬菜连作发病较重;高温有利于该病发生;经药剂种薯、土壤、灌根处理表明：以代森锰锌、菌核净和敌磺钠种薯和土壤处理,代森锰锌、井•1亿活枯草芽孢菌、菌核净灌根处理,防效达50.3%～65.9%。     

Phylogenetic diversity of <Emphasis Type="Italic">Calonectria ilicicola</Emphasis> causing Cylindrocladium black rot of peanut and red crown rot of soybean in southern China

Calonectria ilicicola Boedijin & Reitsma (anamorph: Cylindrocladium parasiticum Crous, Wingfield & Alfennas) is an important pathogen worldwide, which causes Cylindrocladium black rot (CBR) in peanut (Arachis hypogaea L.) and red crown rot (RCR) in soybean [Glycine max (L.) Merr.]. We isolated the CBR and RCR pathogens from heavily diseased peanut and soybean fields in southern China and assessed their pathogenicity. Two inoculation methods were applied separately to evaluate the pathogenicity of different C. ilicicola strains on peanut cultivar Yueyou 13. Our results indicate that the Chinese C. ilicicola strains exhibited a range of virulence on peanut, with strains of soybean origin exhibiting a weak virulence relative to strains isolated from peanut. Multilocus sequence type analysis indicates that the C. ilicicola strains partitioned into two distinct clades, which were heavily structured based on geographical origin. Phylogenetic results demonstrated that the origins of C. ilicicola in southern China were multiple. This study also revealed that the backgrounds of CBR pathogens may be different from those of RCR pathogens.     

醚菌酯对假禾谷镰孢的抑制作用及对小麦茎基腐病的防效研究

 为了明确醚菌酯对假禾谷镰孢的抑制作用,本研究采用菌丝生长速率法和孢子萌发抑制法分别测定了醚菌酯对2019年从河南省13个地市分离的50株假禾谷镰孢的毒力。两种方法结果表明,醚菌酯对供试50株菌株的EC₅₀值范围分别在0.127 3~3.070 9 μg·mL^-1和0.001 3~0.070 9 μg·mL^-1,平均EC₅₀值为(1.304 1±0.804 2)μg·mL^-1和(0.017 4±0.017 0)μg·mL^-1。敏感性频率分布图显示,两种方法分别有80％(40株)和70％(35株)的菌株敏感性频率呈正态分布,其平均EC₅₀值分别为(1.135 2±0.531 2)μg·mL^-1和(0.011 4±0.006 3)μg·mL^-1,可作为假禾谷镰孢对醚菌酯的敏感性基线。方差分析结果表明,同一县市的假禾谷镰孢对醚菌酯的敏感性差异较大,EC₅₀值变化范围为0.545 2~2.156 4 μg·mL^-1和0.001 9~0.036 7 μg·mL^-1。聚类分析结果显示,河南省假禾谷镰孢对醚菌酯敏感性差异与菌株的地理来源无明显关联性。温室防效结果显示,小麦种子与醚菌酯悬浮种衣剂进行拌种处理可以起到一定防治效果,0.42 μL AI/2g处理防效最高,防治效果可达50.33％。本研究结果可为河南省假禾谷镰孢对醚菌酯的敏感性监测提供信息,同时为醚菌酯对小麦茎基腐病的防治提供理论依据。     

Inhibitory influence of inorganic salts on banana postharvest pathogens and preliminary application to control crown rot

Lasiodiplodia theobromae, Thielaviopsis paradoxa, Colletotrichum musae, C. gloeosporioides, Fusarium verticillioides, and F. oxysporum were screened in vitro for sensitivity to Na₂CO₃, NaHCO₃, CaCl₂, NaCl, and NaClO. The spore germination of all pathogens was completely inhibited by Na₂CO₃ 4g/l, NaClO 5g/l, and NaHCO₃, CaCl₂, and NaCl 6g/l each. Dipping the bananas for 10–15min in these concentrations reduced the incidence of crown rot (compared with the untreated fruits) 17 days after harvest in fruits treated with NaClO by 67%, with NaHCO₃ by 62%, with NaCl by 38%, and with CaCl₂ by 33%. Na₂CO₃-treated fruits had the same incidence of crown rot as untreated fruits.     

警惕小麦冠腐病发生及时做好病害防控

由假禾谷镰刀菌(Fusarium pseudograminearum O'DonnellT.Aoki)引起的小麦冠腐病(wheat crown rot)是我国小麦生产上新发生的病害,发展迅速,为害严重。为此,对其症状、国内外发生现状、病原学研究、病害发生成因、风险评估及防控措施等进行了综述,并为今后对小麦冠腐病的深入研究进行了展望。     

Fusarium crown and root rot of tomatoes in the UK

Fusarium crown and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici was found in the UK in 1988 and 1989 mainly in rockwool-grown tomato crops. Up to 14% of plants were affected in individual crops. In experiments, leaf and stem symptoms did not appear until the time of first fruit harvest even when the plants were inoculated at planting, first flowers or fruit set. Conidial inoculum at 10⁶ spores/plant applied at seed sowing killed 70–83% of tomato seedlings, whereas similar levels of inoculum applied to young plants caused root and basal stem decay, and eventually death but only after fruit harvest began. Disease incidence and symptom severity increased with inoculum concentration. Experimentally, the disease was more severe in peat- or compost-grown plants than in rockwool. Disease spread was only a few centimetres in 50 days in experimental rockwool-grown plants. All tomato cultivars tested were highly susceptible. Prochloraz-Mn was highly effective against the pathogen in vitro and controlled the disease in the glasshouse, but only when applied preventively. Non-pathogenic Fusarium oxysporum isolates and Trichoderma harzianum also reduced FCRR disease levels.     

苯醚甲环唑等杀菌剂包衣种子防治花生冠腐病和根腐病

为筛选能兼治花生冠腐病和根腐病、安全而高效的种子处理药剂,采用室内生测法比较了4种杀菌剂对花生冠腐病菌和根腐病菌的毒力,评价了其包衣种子对花生的安全性,并进行了温室接菌盆栽和田间防治试验。结果显示,苯醚甲环唑、氟啶胺、咯菌腈和氟菌唑对花生冠腐病菌的毒力差异较大,EC_(50)分别为0.05、6.56、0.52和1.43 mg/L;对花生根腐病菌的毒力均较高,EC_(50)分别为0.49、0.31、0.44和0.37 mg/L。氟菌唑2 g(a.i.)/kg种子包衣后,花生出苗率和幼苗的根长、株高和茎叶鲜重均降低,出苗时间延迟1~2 d;而氟菌唑0.5、1 g(a.i.)/kg种子包衣及苯醚甲环唑、氟啶胺、咯菌腈3种杀菌剂的所有剂量处理对花生出苗和幼苗生长均无影响。苯醚甲环唑0.5、1、2 g(a.i.)/kg种子,氟啶胺0.4、0.8、1.6 g(a.i.)/kg种子,咯菌腈0.1、0.2、0.4 g(a.i.)/kg种子和氟菌唑0.5、1 g(a.i.)/kg种子包衣对花生冠腐病、根腐病的温室接菌盆栽防效均在80.19%以上。苯醚甲环唑1、2 g(a.i.)/kg种子和咯菌腈0.4 g(a.i.)/kg种子包衣对花生冠腐病、根腐病的田间防效较高,均在75.30%以上,且对荚果的增产率为5.60%~11.10%。表明苯醚甲环唑和咯菌腈包衣种子对花生安全,且可有效防治花生冠腐病和根腐病,具有开发为兼治药剂的潜力。     

小麦茎基腐病生防菌株YB-161的分离鉴定及防效测定

为筛选防治小麦茎基腐病的高效生防菌株,采用稀释涂布法从小麦茎基腐病病土中分离细菌,以假禾谷镰孢Fusarium pseudograminearum为靶标菌,通过平板对峙培养法和室内盆栽试验筛选优良菌株并测定其田间防治效果,分析优良菌株发酵滤液对假禾谷镰孢的抑菌能力,并结合形态特征、Biolog微生物自动鉴定系统和gyrA序列分析对其进行种类鉴定,以及测定该菌株的抑菌谱。结果表明,10份供试土样中共分离到98株细菌,对假禾谷镰孢的菌丝生长抑制率超过40.00%的菌株有14株,其中菌株YB-161对假禾谷镰孢的菌丝生长抑制率最高,达63.50%。室内盆栽试验结果显示,菌株YB-161处理小麦的病情指数最低,为31.40,对小麦茎基腐病的防治效果最好,为68.15%,其对小麦也表现出较好的促生作用。田间调查结果显示,菌株YB-161菌液拌种处理对小麦茎基腐病的田间防治效果高于52.35%,并对小麦具有一定的增产作用。菌株YB-161的发酵滤液5倍稀释液和10倍稀释液对假禾谷镰孢的菌落抑制率分别达66.67%和44.33%,该菌株被鉴定为解淀粉芽胞杆菌Bacillus amyloliquefaciens。此外,菌株YB-161对辣椒炭疽病菌Colletotrichum capisci、烟草疫霉病菌Phytophthora parasitica等5种植物病原真菌均有较好的拮抗作用。表明生防菌株YB-161对绿色防控小麦茎基腐病具有良好的开发利用潜能。     

Phytophthora root and crown rot of raspberry in Bulgaria

Root and crown rot of raspberry (Rubus idaeus L.) was observed in a plantation at the experimental station of small fruits in Kostinbrod, Bulgaria. Isolates ofPhytophthora spp. were obtained from diseased plants. Colony morphology, growth rates, features of asexual and sexual structures were studied and as a result twoPhytophthora species were identified:Phytophthora citricola Saw. andPhytophora citrophthora (R.E. Sm. & E.H. Sm.) Leonian. Their pathogenicity was confirmed in artificial inoculation experiments. The isozyme (-esterase) patterns ofP. citrophthora andP. citricola isolates from raspberry and from the collection of the CBS, Baarn the Netherlands were compared, using micro-gel electrophoresis. Both species are reported for the first time as pathogens of raspberry in Bulgaria. This is only the second report in phytopathological literature ofP. citrophthora on raspberry, the first being from Chile [Latorre and Munoz, 1993].     

Evaluation of plant-growth-promoting rhizobacteria, acibenzolar-S-methyl and hymexazol for integrated control of Fusarium crown and root rot on tomato

BACKGROUND: Plant growth‐promoting rhizobacteria (PGPR) can be potential agents for biological control of plant pathogens, while their combined use with conventional pesticides may increase their efficacy and broaden the disease control spectrum. The effect of four different Bacillus sp. PGPR strains (B. subtilis GB03 and FZB24, B. amyloliquefaciens IN937a and B. pumilus SE34) applied individually and in mixtures, as well as in combined use with acibezolar‐S‐methyl (ASM) and hymexazol, on plant growth promotion and on the control of Fusarium crown and root rot (FCRR) of tomato was evaluated. RESULTS: All PGPR strains promoted the tested plant growth characteristics significantly. A higher promoting effect was provided by SE34. Experiments on population dynamics of PGPR strains revealed that, after 28 days of incubation, populations of strain SE34 remained stable, while the remaining bacterial strains showed a slight decline in their population densities. The GB03 and FZB24 strains provided a higher disease suppression when applied individually. However, application of IN937a in a mixture with GB03 provided a higher control efficacy of Fusarium oxysporum f. sp. radicis‐lycopersici (Forl). Treatment of tomato plants with ASM resulted in a small reduction in disease index, while application of hymexazol provided significantly higher control efficacy. Combined applications of the four PGPR strains with either ASM or hymexazol were significantly more effective. CONCLUSION: The results of the study indicate that, when bacilli PGPR strains were combined with pesticides, there was an increased suppression of Forl on tomato plants, and thus they may prove to be important components in FCRR integrated management. Copyright © 2011 Society of Chemical Industry