Virus-induced changes in the response of faba bean to infection by Botrytis

Prior infection of faba bean with the viruses bean yellow mosaic and bean leaf roll increased host susceptibility to subsequent infection by Botrytis fabae and B. cinerea. Cell necrosis beneath inoculum droplets, rate and extent of lesion spread and sporulation of B. fabae were all increased on detached leaves from virus-infected compared with healthy plants. Changes were most marked in young leaves showing conspicuous symptoms of systemic virus infection and in plants virus-infected for at least 2-4 weeks. Localized lesions produced by B. cinerea or a low concentration of B. fabae conidia (10³ spores/ ml) showed increased cell necrosis but were not transformed into aggressive, spreading lesions on virus-infected leaves.     

Phaseollidin stored in vacuoles and the phytoalexin response in bean

In time-course experiments, the amounts of phytoalexin in hypocotyls of the resistant bean cultivar Flor de Mayo were determined after infection with Colletotrichum lindemuthianum . Phaseollin and phaseollidin accumulated as a defence response. However, phaseollidin accumulated earlier than phaseollin and at greater concentrations (155  +  14 compared with 120  +  9  μ g g⁻¹ fresh weight). Phaseollidin was found conjugated as a glucoside in the tissue. Fungal treatment apparently led to a decline of approximately 50% in phaseollidin conjugate after only 7 h after infection. Isolation of vacuoles confirmed the presence of phaseollidin glucosides in this organelle. Treatment of the tissue or isolated protoplasts with a fungal elicitor also produced a decrease, by half, of phaseollidin conjugate concentrations from vacuoles isolated from both sources. The contribution of pre-existing pools of phaseollidin glycoside to the accumulation of this phytoalexin is discussed.     

A comparison of infection of resistant and susceptible lines of field bean (Vicia faba) by Ascochyta fabae

In a series of growth room experiments, a determinate line of Vicia faba was shown to be more susceptible to infection by Ascochyta fabae than a conventional indeterminate line. On the determinate line, lesions developed more quickly on younger leaves. No evidence of systemic infection was found and disease transfer to the emerging seedling was probably by physical contact with the infected seed testa. Successful establishment of the disease required leaf wetness for periods of 4 h at 20–25° C to 12 h at 10 C. The rate of pycnidiospore germination on leaves decreased with temperature over this range, but did not differ between the determinate and indeterminate lines.     

Virulence for faba bean and production of ascochitine by Ascochyta fabae

The production of ascochitine by seven isolates of Ascochyta fabae accounted for the toxicity of culture filtrates of the fungus to cells isolated from leaves of Vicia faba. The LD₅₀ value for cells from cultivars that were susceptible, tolerant or resistant to the fungus was similar i.e. 3·0 × 10⁻⁵ m , 3·8 × 10⁻⁵ m and 2·9 × 10⁻⁵ M, respectively. Ascochitine affected neither the germination of seeds nor the growth of mature plants at 5·17 × 10⁻⁴ m but caused necrosis and wilting of plant cuttings at 2·5 × 10⁻⁴ m and 5·10⁻⁴ m . There was no association between virulence of 16 isolates of A. fabae for three cultivars of V.faba and the production of ascochitine in vitro. One isolate produced no ascochitine in vitro and yet was the most virulent for two of three cultivars. The toxin could not be extracted from infected plants.     

Wheat/faba bean intercropping improves physiological and structural resistance of faba bean to fusaric acid stress

Fusarium oxysporum f. sp. fabae is the causal agent of fusarium wilt. Fusaric acid (FA), produced by F. oxysporum, plays an important role in the occurrence of disease, and intercropping is an effective measure for control of disease and for improving host resistance in plants. The objective of this study was to investigate the physiological and biochemical responses, and mechanisms of tissue structure resistance, of intercropped faba beans following exposure to different concentrations of FA. Results demonstrated that intercropping reduced the occurrence of fusarium wilt, and improved faba bean growth and yield. In addition, wheat intercropping significantly reduced red ink absorption of faba bean (33.2%), increased water content (3.1%), and increased activity of the root antioxidant enzymes peroxidase (POD) and catalase (CAT) (26.3% and 2.2.%, respectively). Furthermore, increased lignin content and callose deposition in plant vessels were observed (12.5% and 42.7%, respectively) when subjected to the highest concentration of FA stress (200 mg/L). Intercropping resulted in more intact root cell morphology, increased occurrence of intracellular vacuoles, increased cell wall thickness, and an increase in the number of mitochondria and rough endoplasmic reticulum. Intercropping alleviated the wilting effect of FA on faba bean via enhanced physiological, biochemical, and tissue structure resistance of faba bean root.     

种植模式与施磷深度对蚕豆群体冠层结构及其产量的影响

在小区试验与大田生产试验条件下,采用三个种植密度(12 000株·667m-2,13 000株·667m-2,14000株·667m-2)、两个留苗方式(一穴单株,一穴双株)及三个施磷深度(10 cm,15 cm,20 cm)处理,通过裂区试验研究了高产蚕豆群体冠层结构指标及其对产量的影响,结果表明,13 000株·667m-2、15 cm施磷深度、双株三角留苗种植模式下,盛花期蚕豆群体叶面积指数、叶绿素SPAD值,主根长均维持在较高水平,冠层结构较优,产量最高,达到275.2 kg·667m-2;生产试验显示,"一穴双株"能有效提高蚕豆结荚率,提高产量,较常规栽培增产14%以上。提出以"深松增密,减穴加距,中层施磷"为主要内容的蚕豆高产栽培技术。     

Effects of phenylpropanoid and energetic metabolism inhibition on faba bean resistance mechanisms to rust

ABSTRACT Effects on penetration and hypersensitive resistance of the cinnamyl acid dehydrogenase (CAD) suicide inhibitor ([(2-hydroxyphenyl) amino] sulphinyl) acetic acid, 1.1 dimethyl ester, which suppresses phenylpro-panoid biosynthesis, and of D-mannose, which sequesters phosphate and reduces energy available in host cells, were studied in faba bean (Vicia faba) genotypes with differing resistance mechanisms to faba bean rust (Uromyces viciae-fabae). Inhibition of CAD reduced penetration resistance in lines 2N-34, 2N-52, V-1271, and V-1272, revealing an important role for phenylpropanoid biosynthesis in the resistance of these lines. Inhibition of CAD also inhibited hypersensitive cell death in these lines. D-mannose had little or no effect on resistance. By contrast, CAD inhibition did not affect penetration resistance of line BPL-261, which has a high degree of penetration resistance not associated with hypersensitive cell death. In BPL-261, D-mannose inhibited penetration resistance. The parallelism between the faba bean genotype responses to rust observed here and the response of barley genotypes with differing resistance mechanisms to powdery mildew after similar inhibitor treatments is analyzed and discussed.     

Identification and properties of a deviant isolate of the broad bean yellow band serotype of pea early-browning virus from faba bean (Vicia faba) in Algeria

A virus, isolated from faba bean (Vicia faba) obtained from Algeria, was readily recognized as a tobravirus by its particle sizes and morphology. Pea (Pisum sativum) and French bean (Phaseolus vulgaris) characteristically reacted to the isolate like pea early-browning virus (PEBV), but faba bean,Antirrhinum majus, Nicotiana rustica, andN. tabacum reacted with line-pattern symptoms which were unusually brilliant on theNicotiana species. In electronmicroscope decoration tests, the isolate did not react with an antiserum to the Dutch type strain of PEBV, but with one to the broad bean yellow band (BBYB) serotype from Italy. It resembles this serotype in reaction on faba bean, but seems to differ appreciably onN. rustica, N. tabacum, andPetunia hybrida. It is described as a deviant isolate of the BBYB serotype of PEBV.All thirteen faba-bean genotypes tested were found to be susceptible to the Algerian isolate and two Dutch type strain isolates of the virus, and to react with erratic line-pattern symptoms to the Algerian isolate only. All ten genotypes of chickpea (Cicer arietinum) tested reacted hypersensitively, and four out of ten genotypes of lentil (Lens culinaris) were susceptible to the virus but reacted differentially to the three isolates. Seed transmission of PEBV, including the new isolate, in faba bean is confirmed (9% for the Algerian isolate, and over 45% for one of the Dutch type strain isolates), and seed transmission of the virus in a non-legume (N. rustica, 4%) is herewith first reported. This is the first report on the occurrence of the BBYB serotype of PEBV outside Italy, and of PEBV outside Morocco in North Africa.     

湿度调控对番茄灰霉病菌侵染的影响

 番茄灰霉病菌(Botrytes cinerea)的分生孢子萌发需要高湿的环境,一般要求相对湿度在80%以上或水滴中萌发最好。在适温下,随着湿度的增加,病菌致病性增强,孢子在相对湿度85%以上、菌丝在相对湿度80%以上的高湿环境能够发生侵染,并形成危害性的软腐斑。在一天中高湿的时间直接影响番茄灰霉病的发生,高湿(相对湿度超过85%)时间8h以上病菌才能够连续侵染。     

Fungal and plant gene expression during synchronized infection of tomato leaves by Botrytis cinerea

An inoculation procedure was developed to obtain efficient and synchronous infection on detached tomato leaves by Botrytis cinerea. In spray-inoculated leaves incubated at 20 °C, the infection process consisted of three phases: the formation of primary necrotic lesions (until 20 hpi), a quiescent phase (20-72 hpi), and the expansion of a proportion of the primary lesions (from 72 hpi onwards), resulting in full tissue maceration. At 4 °C, the infection progressed slowly but steadily without inducing necrotic responses in the host. The actin and -tubulin genes of B. cinerea were cloned, characterized and used as probes on blots containing RNAs from leaves at various stages of the infection. The genes displayed a similar expression pattern throughout the infection and the hybridization signal reflected the amount of fungal biomass. The actin mRNA accumulated to higher levels than the -tubulin mRNA. Tomato PR protein mRNAs (chitinase, -1,3-glucanase and PR-1) were induced during the infection, albeit with different kinetics and to different levels. At 20 °C, -1,3-glucanase and PR-1 mRNAs were induced more rapidly than chitinase mRNAs. At 4 °C, mRNAs encoding extracellular -1,3-glucanase and intracellular, as well as extracellular chitinase were hardly induced.     

Studies on red light-induced resistance of broad bean to Botrytis cinerea: I. Possible production of suppressor and elicitor by germinating spores of pathogen

When detached broad bean leaves were preinoculated with virulent strain B304 of Botrytis cinerea 24 h before a challenge inoculation with strain B304, lesion formation by B304 was significantly inhibited in red light but not in the dark. In leaves that were preinoculated with avirulent strain 021 and then challenged by B304, however, lesion formation was not inhibited even under red light. Such differences in lesion formation after the challenge inoculation with an avirulent strain were also observed with lesions caused by Alternaria alternata, a nonpathogen of broad bean and by avirulent strain 021R in the presence of germination fluid from spores of strains B304 and 021R. These results suggest the possibility that virulent B. cinerea produced a suppressor involved in induced susceptibility and an elicitor involved in resistance induced by red light during spore germination.     

小豆AP2/ERF基因家族鉴定及其应答锈菌侵染的表达分析

 为明确小豆VaAP2/ERF家族基因在小豆应答豇豆单胞锈菌(Uromyces vignae)侵染中的作用,本研究采用生物信息学方法从小豆基因组中鉴定VaAP2/ERFs家族基因186个,包括AP2(24个)、RAV(2个)、Soloist(1个)及ERF(159个)四个亚家族,其中ERF亚家族又可分为DREB和ERF两个亚类。基因结构分析发现,68.3%的VaAP2/ERFs基因不具内含子。保守基序分析发现,各亚族成员保守域组成类似,可作为基因家族分类的重要依据。前期转录组测序发现VaAP2/ERF中的6个成员接种后24 h显著上调,进一步应用qPCR技术对其在‘1-D-3’(免疫)及‘宝清红’(感病)中应答锈菌侵染的表达分析发现,免疫品种中6个成员均于接种后6 h及120 h显著上调,另有2个于接种后12 h也显著上调,表明上述基因均在小豆抗锈病中发挥正调控作用。     

Effect of plant density on grain yield, root–length density and Orobanche crenata infestation in two faba bean genotypes

The effect of host plant cultivar and sowing density on Orobanche crenata Forsk. L. infestation in Vicia faba was studied in a field experiment in north–west Syria. Two faba bean genotypes. ILB 1814 (Syrian Local Large) and 402/29/84 (new breeding line from Egypt), were planted at four sowing densities. Whereas ILB 1814 was severely affected by O. crenata , 402/29/84 proved to be highly resistant. Sowing density did not have a significant effect on O. crenata dry weight in either genotype. However, the number of O. crenata attachments in ILB 1814 was positively correlated with plant density. The resistance of faba bean genotype 402/29/84 to O. crenata is due to: (a) less plant vigour and root–length density; (b) necrosis of host cells preventing O. crenata attack either before or just after penetration into the host root, or developing a barrier in the host root after the formation of a small tubercle: (c) early flowering and pod setting.     

2018年-2019年重庆蚕豆赤斑病发生情况及预测模型的建立

蚕豆赤斑病是世界蚕豆各产区及我国东南沿海和长江流域地区生产中最主要的病害之一?本研究连续2年对重庆地区29个区县的蚕豆赤斑病发生情况开展了调查?调查结果显示, 城口县发病最轻, 两年平均病情指数为40.9, 长寿区发病最重, 两年平均病情指数为73.4?4个自然生态区中, 秦巴山地常绿阔-落叶林生态区的发病最轻, 两年平均病情指数为47.3?三峡库区平行岭谷农林复合生态区发病最重, 两年平均病情指数为68.4?相关性分析和通径分析结果表明, 1月相对湿度?1月平均风速?3月降水量?3月相对湿度在蚕豆赤斑病的发生过程中起主导作用?此外, 11月平均风速对病情的发展产生较强的负向效应?在以上研究基础上初步建立了基于重庆地区蚕豆赤斑病发生规律的病害预测模型:Y=35.019 46-3.016 18 X7-5.575 8 X9+0.567 9 X27+0.158 6 X29, 模型表明, 11月平均风速(X7)?1月平均风速(X9)?1月相对湿度(X27)?3月相对湿度(X29)与病情指数(Y)有较强的线性关系?本模型的建立为蚕豆赤斑病的防控提供了技术支撑?     

Phytoalexin accumulation during infection of bean and soybean by ascospores and mycelium of Sclerotinia sclerotiorum

Infection by ascospores of Sclerotinia selerotiorum caused hypersensitivity in epidermal cells in leaves and etiolated hypocotyls of bean and soybean. In bean, phaseollin and phaseollidin accumulated in leaves but kievitone alone in hypocotyls. In soybean, no phytoalexins were detected in leaves but glyceollin accumulated in hypocotyls.
Mycelial infection caused water-soaked spreading lesions in leaves and etiolated hypocotyls of both hosts. In bean, no phytoalexins were detected in leaves but kievitone alone accumulated in hypocotyls. In soybean, glyceollin accumulated in leaves but was not sought in hypocotyls.
Transfer of bean hypocotyls infected with mycelium from 18 to 28°C caused lesion limitation and marked accumulation of phaseollin and kievitone.
Phaseollin, kievitone and glyceollin inhibited ascospore germination and growth of hyphae from preformed germ-tubes and established mycelia, phaseollin being most active and glyceollin least active. Hyphal growth from mycelia was least affected by the phytoalexins.     

Field and controlled conditions screenings of some faba bean (Vicia faba L.) genotypes for resistance to the parasitic plant Orobanche crenata Forsk. and investigation of involved resistance mechanisms

Journal of Plant Diseases and Protection - The parasitic weed Orobanche crenata is a serious constraint to legumes crops in Mediterranean area. In Morocco, heavy O. crenata infestation level was...     

Sensitivity to,and metabolism of,phaseollin in relation to the pathogenicity of different isolates of Botrytis cinerea to bean (Phaseolus vulgaris)

The pathogenicity of five isolates ofBotrytis cinerea to bean (Phaseolus vulgaris) was compared with their sensitivity to the phytoalexin phaseollin and their ability to metabolize phaseollin. Three of the five isolates were pathogenic to bean, as they formed spreading lesions on bean leaves; the other two isolates were considered nonpathogenic to bean, since they produced lesions limited in size or no lesions at all. The isolates were about equally sensitive to phaseollin, except for one nonpathogenic strain which was more sensitive than the other ones to higher concentrations of phaseollin. The three pathogenic isolates metabolized phaseollin to 6a-hydroxyphaseollin readily in shake cultures containing 9 μg phaseollin/ml, while nonpathogenic isolates were not able, or less able, to do so.     

Effect of Pythium spp. and glyphosate on phytoalexin production and exudation by bean (Phaseolus vulgaris L.) roots grown in different media

Kievitone, phaseollinisoflavan and phaseollin were detected in roots of bean seedlings (Phaseolus vulgaris L.) grown in natural soil. Comparison of phytoalexin production by roots grown in different media indicated that these phytoalexins were probably induced by microorganisms in soil. The influence of common root rot pathogens of bean, Pythium spp., on phytoalexin production was determined. Pythium ultimum elicited kievitone, phaseollinisoflavan and phaseollin in roots grown in sterilized silica sand. P. sylvaticum induced only kievitone and phaseollin in the same growth medium. Glyphosate did not significantly affect the accumulation of phytoalexins within 3 days. However, by day 5, significantly more phaseollin was detected in the roots of Pythium inoculated plants treated with glyphosate than in Pythium inoculated plants not treated with glyphosate. In a hydroponic system, both Pythium spp. elicited accumulation of kievitone and phaseollin in root tissue, and both phytoalexins were exuded into the bathing solution. Glyphosate application did not significantly affect accumulation or exudation of phytoalexins by bean roots in the hydroponic system. The results from this study illustrate the nature and extent of phytoalexin production by bean roots in the absence and presence of microbes.     

Reduced sensitivity of Botrytis cinerea to two sterol biosynthesis-inhibiting fungicides: fenetrazole and fenethanil

Isolates of Botrytis cinerea having reduced sensitivity to the sterol biosynthesis-inhibiting (SBI) fungicides fenetrazole and fenethanil were obtained from one out of four sites from which isolates were tested. Reduced sensitivity was associated with poor disease control by fenetrazole, which had been applied with dichlofluanid. Conidial germination and hyphal growth of B. cinerea from the four sites were tested in vitro on media amended with the fungicides. Following fenetrazole or fenethanil treatment, at the site where control had failed, populations of B. cinerea were detected with higher EC₅₀ and EC₉₀ values than at the three other sites. Germination of conidia of B. cinerea was markedly inhibited by 1.0 μg/ml fenetrazole and 0.5–1.0 μg/ml fenethanil. The frequency of isolates insensitive to 1.0 μg/ml fenetrazole or to 0.5 μg/ml fenethanil was 3.4 and 1.8 times higher, respectively, at the site where control had failed, compared with another site where SBI fungicides had never been applied to control grey mould. Grey mould caused by selected isolates of B. cinerea which expressed the phenotype of low sensitivity to SBI fungicides in leaves of tomato, pepper and Senecio cineraria was not controlled by either fenetrazole or fenethanil (1 .5–3.0 μg/ml). However, up to 100% disease reduction was obtained when leaves infected by sensitive isolates were treated with the fungicides.