Nematicidal Volatiles from Bacillus atrophaeus GBSC56 Promote Growth and Stimulate Induced Systemic Resistance in Tomato against Meloidogyne incognita

Bacillus volatiles to control plant nematodes is a topic of great interest among researchers due to its safe and environmentally friendly nature. Bacillus strain GBSC56 isolated from the Tibet region of China showed high nematicidal activity against M. incognita, with 90% mortality as compared with control in a partition plate experiment. Pure volatiles produced by GBSC56 were identified through gas chromatography and mass spectrometry (GC-MS). Among 10 volatile organic compounds (VOCs), 3 volatiles, i.e., dimethyl disulfide (DMDS), methyl isovalerate (MIV), and 2-undecanone (2-UD) showed strong nematicidal activity with a mortality rate of 87%, 83%, and 80%, respectively, against M. incognita. The VOCs induced severe oxidative stress in nematodes, which caused rapid death. Moreover, in the presence of volatiles, the activity of antioxidant enzymes, i.e., SOD, CAT, POD, and APX, was observed to be enhanced in M. incognita-infested roots, which might reduce the adverse effect of oxidative stress-induced after infection. Moreover, genes responsible for plant growth promotion SlCKX1, SlIAA1, and Exp18 showed an upsurge in expression, while AC01 was downregulated in infested plants. Furthermore, the defense-related genes (PR1, PR5, and SlLOX1) in infested tomato plants were upregulated after treatment with MIV and 2-UD. These findings suggest that GBSC56 possesses excellent biocontrol potential against M. incognita. Furthermore, the study provides new insight into the mechanism by which GBSC56 nematicidal volatiles regulate antioxidant enzymes, the key genes involved in plant growth promotion, and the defense mechanism M. incognita-infested tomato plants use to efficiently manage root-knot disease.     

Putative LysM Effectors Contribute to Fungal Lifestyle

Fungal LysM effector proteins can dampen plant host–defence responses, protecting hyphae from plant chitinases, but little is known on these effectors from nonpathogenic fungal endophytes. We found four putative LysM effectors in the genome of the endophytic nematophagous fungus Pochonia chlamydosporia (Pc123). All four genes encoding putative LysM effectors are expressed constitutively by the fungus. Additionally, the gene encoding Lys1—the smallest one—is the most expressed in banana roots colonised by the fungus. Pc123 Lys1, 2 and 4 display high homology with those of other strains of the fungus and phylogenetically close entomopathogenic fungi. However, Pc123 Lys3 displays low homology with other fungi, but some similarities are found in saprophytes. This suggests evolutionary divergence in Pc123 LysM effectors. Additionally, molecular docking shows that the NAcGl binding sites of Pc123 Lys 2, 3 and 4 are adjacent to an alpha helix. Putative LysM effectors from fungal endophytes, such as Pc123, differ from those of plant pathogenic fungi. LysM motifs from endophytic fungi show clear conservation of cysteines in Positions 13, 51 and 63, unlike those of plant pathogens. LysM effectors could therefore be associated with the lifestyle of a fungus and give us a clue of how organisms could behave in different environments.     

SH7对烟草青枯病的抑菌、防病作用及其抑菌物质的初步研究

研究了生防细菌菌株SH7及其除菌发酵液对烟草青枯病菌(Ralstonia solanacearum)的抑菌和防病作用,并对其产生的抑菌物质进行了粗提。结果显示,该菌株对R.solanacearum有很强的抑菌作用,且其除菌体发酵液对烟草青枯病的防效较好。将SH7无菌发酵液、无菌发酵液与青枯病菌混合30 min施入土壤29 d后,两种处理与对照相比,防效分别达到65.99%和53.2%;SH7菌株产生的抑菌物质是SH7除菌发酵液防病的主要机制;SH7分泌的抑菌物质可以被硫酸铵沉淀,初步认为该抑菌物质是蛋白类物质。     

烟草拮抗内生细菌的筛选与防病促生长效果

为了获得能促进烟草生长和防治黑胫病的稳定菌株,通过常规方法从烟草茎、叶中分离到478株内生细菌,其中65株能拮抗烟草黑胫病菌,占13.60%。菌株YN201408、YN201442、YN201448和YN201458对烟草疫霉的抑菌率分别为63.85%、60.82%、64.72%和76.07%,用1.0×107 cfu/mL拮抗菌液浸烟苗根系30 min,移栽后浇灌1次,在温室盆栽试验中控病效果分别为68.24%、65.47%、69.12和41.40%。YN201448对烟草种子萌芽率和烟草的生长都有促进作用,烟草的发芽率、第5~6真叶期苗高和地上部鲜重分别高于清水对照10.95%、29.31%和67.24%。依据菌体形态、生理生化特征和16S rDNA序列,YN201408、YN201442和YN201448鉴定为解淀粉芽孢杆菌,YN201458为铜绿假单胞菌。YN201448因良好的促生长和控病效果而具有继续开发应用的潜力。     

Listeria monocytogenes: A Target for Bacteriophage Biocontrol

Listeria monocytogenes is a growing concern in the food industry as it is the causative agent of human listeriosis. There are many research articles concerning the growth, survival, and diversity of L. monocytogenes strains isolated from food‐related sources, elucidating the difficulty in controlling these bacteria in a food‐processing facility. Bacteriophage biocontrol of L. monocytogenes strains was introduced in 2006, through the first commercial bacteriophage product targeting L. monocytogenes ListShield^TM. This review focuses on the use of bacteriophage biocontrol to target L. monocytogenes in the food industry, specifically direct application of the bacteriophages to food products. In addition, we discuss characteristics of these bacteria that will have a significant influence on the effective treatment of bacteriophages such as genetic diversity between strains prevalent in one facility. There are many positive results of phage treatments targeting L. monocytogenes in food; however, success of in vitro studies might not be reproducible in practice. Future studies should focus on creating experimental design that will imitate the conditions found in the food industry, such as a stressed state of the targeted bacteria. In situ evaluation of bacteriophage treatment of L. monocytogenes will also be necessary because the presence of these bacteria in a processing facility can vary greatly regarding genetic diversity. The potential use of phages in the food‐processing facility as a biosanitizer for L. monocytogenes, as well as the use of lysins to target these bacteria should also be explored. Despite the exciting research avenues that have to be explored, current research shows that biocontrol of L. monocytogenes is feasible and has potential to positively impact the food industry.     

腐植酸生防生物有机肥对辣椒根腐病防治效果的研究

将3种生防菌剂与腐植酸生物有机肥结合,制成4种腐植酸生防生物有机肥,应用于接种了镰孢菌的土壤,研究其对辣椒根腐病防治效果的影响。试验结果表明,4种腐植酸生防生物有机肥处理病情指数下降,防病效果提高。同时,土壤微生物群落也发生了变化,根际土壤和非根际土壤的细菌数量比CK分别增加了3.31~5.77倍和6.06~7.49倍,放线菌分别增加了2.98~5.89倍和6.71~11.62倍,而真菌数量分别减少了9.24%~41.58%和1.79%~56.38%,根尖镰孢菌的数量分别减少了2.18~6.92倍和2.51~7.46倍;土壤微生物量碳、土壤微生物量氮、土壤微生物量磷分别增加了250.35~409.42 m g/k g、50.63~61.89 m g/k g和14.30~20.01 m g/k g。可见,施用腐植酸生防生物有机肥能有效降低辣椒根腐病的发生和危害,提高防治效果,适合在辣椒生产中推广应用。     

0．2％α-吡喃酮WP对植物病原真菌的防治效果

0．2％α-吡喃酮WP的有效成分为5,6-二氢-6-戊基-2H-吡哺-2-酮（5,6-dihydro-6-pentyl-2H-pyran-2-one）。采用菌丝速率法测定了0．2％阻吡喃酮WP的抗菌谱，含药浓度20gg／ml的PDA培养基对测试的11种植物病原真菌均有抑制作用，其中对禾谷丝核菌的抑制作用最强，抑制率为89．3％。温室条件下用干种子量0．5％的0．2％阻吡喃酮WP拌种处理对小麦纹枯病的防治效果达61．6％，对棉花立枯病的防治效果达85．6％，较于种子量1％的40％多菌灵拌种处理防治效果分别提高了14．6％和17．9％。     

Yeasts associated with nectarines and their potential for biological control of brown rot

Resident fruit microflora has been the source of biocontrol agents for the control of postharvest decay of fruits and the active ingredient in commercialized biocontrol products. With the exception of grapes and apples, information on the resident microflora of other fruits is only fragmentary, but greater knowledge in this area can be very helpful in developing biocontrol strategies. We characterized the yeast microflora of nectarines (‘Croce del Sud’) from the early stages of fruit development until harvest. The fruit samples were collected from trees in an unmanaged orchard. The resident fruit microflora was separated from the occasionally deposited microorganisms by discarding initial fruit washings before the final wash, followed by sonication and plating on NYDA medium. The isolated yeasts were identified by BIOLOG and by sequencing the D1/D2 domain of a large subunit of the rRNA gene and, where available, the ITS sequence. BIOLOG identified 19 and the genetic analysis 23 species of yeasts. Although the identification by these two systems was not always the same, the predominant yeasts were Rhodotorula spp., Sporodiobolus spp., Cryptococcus spp., Pichia spp., Candida spp. and yeast‐like Aureobasidium pullulans. Several of the taxa appear to represent new species. The preliminary biocontrol tests against brown rot of nectarine fruit caused by Monilinia fructicola indicates significant decay control potential of some of the identified yeast species, namely Cryptococcus magnus, Cryptococcus sp. nov., Sporidiobolus pararoseus, A. pullulans and Rhodotorula sp. nov. Copyright © 2010 John Wiley & Sons, Ltd.