Biological control of peach twig blight (Monilinia laxa) with Epicoccum nigrum

Various preparations of spores and mycelium of the antagonist Epicoccum nigrum , alone or in combination with Captan, were applied in four different field trials to peach trees inoculated with Monilinia laxa , the cause of twig blight. Biocontrol obtained after application of E. nigrum was variable each year, depending on the releative disease severity in the first 2–3 weeks after infection and the climatic conditions. In three out of four trials, treatments with E. nigrum were comparable with Captan in reducing disease severity and combinations of E. nigrum and Captan gave a level of disease suppression similar to that given by the antagonist or chemical alone. In the remaining trial, combinations of E. nigrum and Captan were necessary to obtain successful disease suppression.     

Effects of pyroquilon on the infection process of Monilinia laxa causing peach twig blight

The capacity of Monilinia laxa (Aderh. et Ruhl.) Honey to induce peach twig blight was lost in an albino mutant and in a wild-type strain of the pathogen treated with pyroquilon, a melanin biosynthesis inhibitor. Pyroquilon (10 ù ml^?1) inhibited melanin biosynthesis but did not inhibit mycelial growth of the pathogen or the albino mutant in vitro. These observations indicate that the compound interferes in some manner with the infection process of host cells.     

进口智利李子上核果褐腐病菌鉴定

从进口智利李子上分离到一种引起李子果实腐烂的病原真菌,接种李子能引起果实变褐和腐烂。该真菌菌丝在PDA培养基上的生长最适温度为25℃,产孢少,菌落初始为浅灰色,边缘浅裂状,多次传代后逐渐变为浅白色,边缘整齐。分生孢子无色,单孢,柠檬形或卵圆形,大小11．5（9．5～14．7）μm×7．4（5．3～9．2）μm。ITS序列分析结果表明该分离物ITS区序列与GenBank中登录的16株舱laxa序列相似性分别为99．8％～100％,碱基的差异为0～1bp;与21株旭frueticola序列相似性为99．0％～99．2％,碱基的差异为4～5bp;与10株M.fructigena的序列相似性为97．5％～97．7％,碱基的差异为13～14bp。基于ITS序列的系统发育关系分析表明分离物sh675和GenBank中登录的16个M.laxa菌株属于同一个聚类群,相关的Mfructieola和M.fructigena属于另一个聚类群。M.laxa特异性引物ITS1Mix／ITS4Mlx能扩增分离物sh675的菌丝DNA,得到预期的356bp扩增产物。根据该真菌的菌落形态特征、分生孢子形态特征、ITS序列和PCR检测结果,将其鉴定为核果褐腐病菌（Monilinia laxa）。     

Occurrence of Monilinia laxa and M. fructigena after introduction of M. fructicola in peach orchards in Spain

Seventeen field surveys were done in four commercial orchards during six consecutive fruit-growing seasons from 2006 until 2011 in order to determine the current frequencies of occurrence of M. laxa, M. fructigena, and M. fructicola and their relative contributions to postharvest brown rot in peaches and nectarines in the Ebro Valley. The relative frequencies of occurrence of Monilinia spp. were determined on three sources of primary inoculum and on three sources of secondary inoculum. The major relative frequencies of Monilinia spp. were significantly recorded (P?=?0.05) from mummified fruit on the trees (approx. 42 %) and 7-day-old harvested fruit with brown rot (32 %), followed by that recovered from mummified fruit on the orchard bed (14 %), pruned branches on the orchard bed (8 %) and latent infections of immature fruit (3 %). We found that: (a) the relative frequency of M. fructicola has increased over the years to coexist on the same level as at the time M. laxa, (b) M. fructigena is no longer a cause of brown rot in harvested peaches, (c), a progressive reduction in the time of the first appearance of Monilinia airborne conidia (r?=??0.30, P?=?0.003), and the time of the first latent infection (r?=??0.44, P?=?0.0001) was detected along years after correlation analysis, and (d) these displacements are not associated with an increased incidence of brown rot disease. The M. fructicola increase was due to its significantly increased presence in 7-day-old harvested fruit with brown rot (r?=?0.73, P?=?0.0009), in latent infections of immature fruit (r?=?0.68, P?=?0.002), on pruned branches on the orchard bed (r?=?0.56, P?=?0.018), and on mummified fruit sampled on the trees (r?=?0.53, P?=?0.03). This progressive increase was accompanied by a progressive reduction in the relative frequency of occurrence of M. laxa in 7-day-old harvested fruit with brown rot (r?=??0.55, P?=?0.021) and M. fructigena on mummified fruit sampled on the trees (r?=??0.51, P?=?0.03).     

楠木枝枯病病原菌鉴定

<正>楠木为我国传统名贵树种,其木质紧密、耐腐蚀性强,能够驱虫美化环境,是建筑、家具、雕刻的首选木料;同时具有净化空气、吸烟滞尘、涵养水源、固土防沙等功能,有着巨大的经济及生态价值。楠木主要包括润楠属(Machilus Nees)以及楠属(Phoebe Nees)植株,均属于濒危树种,在我国境内     

楠木枝枯病病原菌鉴定

Phoebe is a traditional precious tree species in China, which has great economic and ecological value. A new disease twig blight was found in the Phoebe planting area of Zhejiang province. Symptoms usually appear on the base or fork of branches with black swollen epidermis and gradually get worse resulting branch wilting or whole plant death when longitudinal epidermis cracking. The diseased samples were collected in 2017-2018 and the fungal isolate was identified as Lasiodiplodia pseudotheobromae based on morphological characteristics of colony and spore and sequence analysis of ITS region and EF1-α gene. The pathogenicity tests on Phoebe showed that L. pseudotheobromae caused the typical symptoms of twig blight. Koch′s postulates were satisfied following reisolation and identification of the isolate from the infected tissues using the methods described above. This is the first report of Phoebe twig blight caused by L. pseudotheobromae in China.     

A novel strategy to reduce overwintering inoculum of Monilinia laxa

Brown rot on cherry and plum, caused by Monilinia laxa, is an important disease, for which overwintered mummified fruit is a significant inoculum source for infection of flowers and fruit in the spring. Experiments were conducted to assess the potential of applying plant protection products in winter and/or early spring to suppress sporulation on mummified fruit. Products tested included Indar 5 EW (a commercial fungicide, a.i. fenbuconazole), Aureobasidium pullulans Y126 [a candidate biocontrol agent (BCA)]), Bacillus sp. B91 (a candidate BCA) and Serenade (a commercially formulated BCA of Bacillus subtilis strain QST 713) in addition to control treated with tap water. Indar and A. pullulans Y126 significantly reduced sporulation when applied once in winter. Overall, a single treatment in early spring (February) was slightly more effective than single treatment in winter (November). Application of all products in both winter and early spring led to significant reduction in sporulation. Indar had the highest efficacy, reducing the number of spores from 9?×?10⁵ to 5?×?10³ per mummified plum when applied twice. Of the three BCAs applied on both occasions, A. pullulans Y126 had the highest efficacy, reducing the number of spores from 9?×?10⁵ to 5?×?10⁴ per mummified plum. There were no synergistic but additive effects between the two applications in winter and early spring based on the Bliss independence test. These results suggest that reducing overwintering inoculum in dormant season is effective and may be part of an integrated management strategy for brown rot on stone fruit.     

Biological control of fire blight of hawthorn (Crataegus monogyna) with Erwinia herbicola under protected conditions

Isolates of Erwinia herbicola , obtained from flowers and leaves of hawthorn ( Crataegus monogyna) , were screened as potential control agents of fire blight disease (caused by Erwinia amylovora) using an immature pear fruit assay. Selected isolates were subsequently tested for disease control by infection of hawthorn blossom in the laboratory, and by shoot infection of hawthorn plants grown under controlled (glasshouse) and fluctuating (polythene tunnel) environmental conditions.
Although the immature pear fruit assay provided a general screen for the selection of antagonists for the control of both blossom and shoot blight, it had two major limitations when quantitatively applied. Firstly there were inconsistencies in the relative effects of different isolates on the pear-slice surface, with some isolates being more suppressive than the standard antagonist Eh252 in the first screening and less in the second. Secondly the assay was not able to predict accurately the level of control in the intact plant-as no correlation occurred between the level of control in the pear fruit assay and the percentage control of either blossom blight or shoot blight.
Two isolates of E. herbicola , WL9 and WL40, reduced both blossom- and shoot-blight. WL9 provided over 80% control of blossom blight, equivalent to that provided by chemical agents, and also gave total control of shoot blight when applied at a WL9: pathogen ratio of 10:1.     

Monilinia species identified on peach and nectarine in Croatia,with the first record of Monilinia fructicola

During 2012, an official survey was conducted for Monilinia species present on peach and nectarine in Croatia. In total, 169 Monilinia spp. isolates were collected from 24 commercial orchards and identified according to morphology in culture and PCR. Eighty of the isolates were identified as Monilinia laxa, 70 as M. fructigena and 19 as M. fructicola. M. fructicola was found only at one location in the Mediterranean part of the country, and this is the first record of this quarantine fungus in Croatia. PCR diagnostic tests using M. fructicola‐specific primer pair MO368‐5/MO368‐10R repeatedly gave false negatives for some isolates. PCR tests using primer pair ITS1‐Mfc1/ITS4‐Mfc1 amplified M. fructicola‐specific product in all isolates and was therefore shown to be more suitable for diagnostic purposes.     

Characterization and PCR-based detection of benzimidazole-resistant isolates of Monilinia laxa in California

Monilinia laxa is a pathogen of brown rot of stone fruit and almond in California, causing blossom blights and fruit rots. In this study, low-level resistance to the benzimidazole fungicides benomyl and thiophanate-methyl was detected in field isolates of M laxa collected from stone fruits and almonds in California. Low-resistant (LR) isolates grew in potato dextrose agar (PDA) plates amended with benomyl and thiophanate-methyl at 1 and 5 microg ml(-1), respectively, but not in plates amended with benomyl at 5 microg ml(-1) or thiophanate-methyl at 50 microg ml(-1). The benzimidazole LR isolates were characterized by temperature sensitivity and the DNA sequence of the beta-tubulin gene. The LR isolates showed high-temperature sensitivity, being sensitive to 1 microg ml(-1) of benomyl at 28 degrees C but resistant at 8-24 degrees C. Analysis of the DNA sequence of the beta-tubulin gene showed that the LR isolates had a point mutation at the amino-acid position 240, causing substitution of leucine by phenylalanine. Based on the point mutation, a pair of allele-specific PCR primers was developed for rapid detection of LR isolates of M laxa. In addition, a pair of PCR primers specific to M laxa was developed on the basis of the differences in the DNA sequence of the intron 6 of beta-tubulin gene from M laxa, M fructicola and other fungal species. The primer pair amplified the expected 376-bp DNA fragment from all M laxa isolates tested, but not from 14 other fungal species isolated from stone fruit and almond crops. The restriction endonuclease BsmA I recognized the sequence GTCTCC in the PCR products from sensitive (S) isolates only, but not the GTTTCC sequence in the PCR products from LR isolates. The endonuclease digested the 376-bp PCR products from S isolates to produce two bands (111 and 265 bp) on agarose gels. Thus, both allele-specific PCR and the PCR-restriction fragment length polymorphism (PCR-RFLP) methods could be useful for rapidly detecting benzimidazole-resistant isolates of M laxa from stone fruit and almond crops in California.     

Monilinia laxa associated with blossom wilt of apricot and almond in Himachal Pradesh, India

Blossom wilt, an important phase of the brown rot disease, resulting in crop losses in apricot and almond, is reported for the first time from North India. Based on general morphology, cultural and sporulation characteristics, and isoelectric focusing profiles, the causal fungus was identified as Monilinia laxa.     

Epidemiology and management of brown rot on stone fruit caused by Monilinia laxa

Stone fruit is attacked by various pathogens, of which brown rot disease is one of the important diseases. There are three Monilinia species mainly responsible for the brown rot disease: Monilinia fructicola is mainly found in North America and Australasia, and M. laxa and M. fructigena mainly in Europe. Both M. fructicola and M. laxa can infect flowers, resulting in blossom blight, as well as both healthy and wounded fruit, resulting in brown rot. On the other hand, M. fructigena can only infect wounded fruit. Compared to the two other species, M. fructicola has been extensively studied, whereas the equally important M. laxa has had less attention. This paper addresses this imbalance and reviews research on the biology, epidemiology and management of M. laxa on stone fruits. Due to EU regulations, the number of fungicides available for controlling plant diseases has been steadily decreasing, particularly in the post-harvest environment. This has placed much more emphasis on alternative control methods, a focus of the present review. Numerous physical and biological approaches to control have achieved successful outcomes but often in small-scale trials and in isolation from integrated strategies. Promising physical control methods include removal of mummified fruit in orchards and post-harvest hot-water treatment. Many micro-organisms have been shown to have biocontrol potential against brown rot but only a few have been commercially formulated. It is generally agreed that the use of biocontrol agents needs to be integrated with other measures. Current research focuses on disease management from flowering to post-harvest period. Recent results have suggested that reducing overwintering inoculum should be considered as one of key aspects of integrated management of brown rot on stone fruit. Finally, we make recommendations about future research and development on integrated pest management strategies for control of M. laxa, especially on strategic deployment of biocontrol agents and interactions among brown rot pathogens.     

Biological control of fire blight of apple and pear with antagonistic Lactobacillus plantarum

Lactic acid bacteria (LAB) can be a source of biological control agents (BCA) of fire blight disease. Several species of LAB are inhabitants of plants and are currently used as biopreservatives of food because of their antagonistic properties against bacteria, and are considered as generally safe. Candidates to BCA were selected from a large collection of LAB strains obtained from plant environments. Strains were first chosen based on the consistency of the suppressive effect against E. amylovora infections in detached plant organs (flowers, fruits and leaves). Lactobacillus plantarum strains PC40, PM411, TC54 and TC92 were effective against E. amylovora in most of the experiments performed. Besides, strains PM411, TC54 and TC92 had strong antagonistic activity against E. amylovora and also other target bacteria, and presented genes involved in plantaricin biosynthesis (plnJ, plnK, plnL, plnR and plnEF). The strains efficiently colonized pear and apple flowers; they maintained stable populations for at least 1 week under high RH conditions, and survived at low RH conditions. They were effective in preventing fire blight on pear flowers, fruits and leaves, as well as in whole plants and in a semi-field blossom assay. The present study confirms the potential of certain strains of L. plantarum to be used as active ingredient of microbial biopesticides for fire blight control that could be eventually extended to other plant bacterial diseases.     

内生芽孢杆菌TB2防治辣椒疫病效果及其机理初探

 内生芽孢杆菌(Bacillus sp.) TB2对辣椒疫霉(Phytophthora capsici)引起的辣椒苗和果疫病有良好的防治效果,菌液浸种处理的苗接种病菌后20 d防病效果可达70.0%;菌液浇灌后48 h的苗接种病菌后20 d防病效果可达88.1%;菌液喷雾处理的果接种病菌后14 d防病效果可达65.2%。喷雾或浇灌菌株培养液后间隔24 h以上接种病原菌的防病效果比二者同时接种时高。生防菌菌体及其胞外分泌物均有防病作用,其胞外分泌物的速效性较好,菌体的持效性较好。菌株胞外分泌物对病菌菌丝生长、孢子囊形成和游动孢子释放均有明显的抑制作用。菌液可诱导植物抗性相关酶的变化,但其与病菌共同接种于辣椒时诱导作用可相互影响。疫霉菌处理可使辣椒果的丙二醛(MDA)含量和过氧化物酶(POD)、超氧化歧化酶(SOD)、过氧化氢酶(CAT)活性出现明显的峰值;菌液处理可诱导辣椒SOD和POD活性增强;但菌液与病菌共同处理后,辣椒果的MDA含量和SOD、POD、CAT的活性均较低,与清水对照接近,表现出一种相对稳定的状态。     

Biological control of fusarium seedling blight disease of wheat and barley

ABSTRACT Fusarium fungi, including F. culmorum, cause seedling blight, foot rot, and head blight diseases of cereals, resulting in yield loss. In a screen for potential disease control organisms and agents, Pseudomonas fluorescens strains MKB 100 and MKB 249, P. frederiksbergensis strain 202, Pseudomonas sp. strain MKB 158, and chitosan all significantly reduced the extent of both wheat coleoptile growth retardation and wheat and barley seedling blight caused by F. culmorum (by 53 to 91%). Trichodiene synthase is a Fusarium enzyme necessary for trichothecene mycotoxin biosynthesis; expression of the gene encoding this enzyme in wheat was 33% lower in stem base tissue coinoculated with Pseudomonas sp. strain MKB 158 and F. culmorum than in wheat treated with bacterial culture medium and F. culmorum. When wheat and barley were grown in soil amended with either chitosan, P. fluorescens strain MKB 249, Pseudomonas sp. strain MKB 158, or culture filtrates of these bacteria, the level of disease symptoms on F. culmorum-inoculated stem base tissue (at 12 days post- F. culmorum inoculation) was >/=31% less than the level on F. culmorum-inoculated plants grown in culture medium-amended soil. It seems likely that at least part of the biocontrol activity of these bacteria and chitosan may be due to the induction of systemic disease resistance in host plants. Also, in coinoculation studies, Pseudomonas sp. strain MKB 158 induced the expression of a wheat class III plant peroxidase gene (a pathogenesis-related gene).     

Effect of hot water treatment on peach volatile emission and Monilinia fructicola development

The effect of hot water treatment (HWT) to control peach brown rot was investigated. Peaches were dipped in water at 60°C for 60 s and artificially inoculated with Monilinia fructicola conidia. HWT failed to control brown rot if applied before inoculation and microscopic observations revealed a stimulatory effect on germ tube elongation of M. fructicola conidia placed immediately after HWT on the fruit surface, compared to the control. The influence of fruit volatile emission due to HWT was performed on the pathogen conidia exposed to the headspace surrounding peaches. The results showed an increase of M. fructicola conidial germination ranging from 33 to 64% for cultivars Lucie Tardibelle and Red Haven heat‐treated peaches, respectively, compared to the control. The volatile blend emitted from heat‐treated fruit was analysed by solid‐phase microextraction/gas chromatography‐mass spectrometry (SPME/GC‐MS) and proton transfer reaction‐time of flight‐mass spectrometry (PTR‐ToF‐MS). Fifty compounds were detected by SPME/GC‐MS in volatile blends of cv. Lucie Tardibelle peaches and significant differences in volatile emission were observed among heated and control fruit. Using PTR‐ToF‐MS analysis, acetaldehyde and ethanol were detected at levels 15‐ and 28‐fold higher in heated fruit compared to unheated ones, respectively. In vitro assays confirmed the stimulatory effect (60 and 15%) of acetaldehyde (0·6 μL L^?1) and ethanol (0·2 μL L^?1) on M. fructicola conidial germination and mycelial growth, respectively. The results showed that volatile organic compounds (VOCs) emitted from heat‐treated peaches could stimulate M. fructicola conidial germination, increasing brown rot incidence in treated peaches when the inoculation occurs immediately after HWT.