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In greenhouse experiments, three strains of plant growth-promoting rhizobacteria (PGPR), Serratia sp. J2, fluorescent pseudomonad J3, and Bacillus sp. BB11, were evaluated for biological control of bacterial wilt of tomato caused by Ralstonia solanacearum. A total of four field trials were conducted, each in a different location in Jiangsu and the Hebei provinces. Strains J2, J3, and BB11 provided disease control and increased yield. In trial one in Qixia (1999), disease was reduced 66.1, 73.6, and 68.4% by J2, J3, and BB11, respectively, compared to the control. Yield increases with bacteria in this trial ranged from 49.5 to 70.8%. In trial two in Huaian (2000), disease was reduced 78.1, 94.1, and 86.9% by J2, J3, and BB11, respectively. Yield increases ranged from 180 to 237%. In trial three in Handan (1999), biocontrol efficiencies of 71.3, 63.6, and 78.2% were achieved by J2, J3, and BB11, respectively. Yield increases ranged from 53.5 to 76.2%. In trial 4 in Handan (2000), disease was reduced 74.4, 75.1, and 81.9% by J2, J3, and BB11, respectively, compared to the control. Yield increases with these bacteria ranged from 46.3 to 78.5%. Additional tests were conducted with 1-year-old and 2-year-old formulations of each PGPR strain. Populations of PGPR in the 1-year-old formulations were nearly identical to freshly prepared PGPR formulations. Biological control efficacy was retained by the stored formulations of all three PGPR strains, with 1-year-old formulations providing 68.4–99.5% control and 2-year-old formulations providing 63.4–78.5% control. Yield increases with stored formulations ranged from 35.4 to 67.0%. We conclude that our method of formulating PGPR products provides stable formulations that retain biological control and plant growth-promoting activities. [Copyright &y& Elsevier]

[Display omitted] • Bacillus amyloliquefaciens HSSN09 with antagonistic effect on FON was isolated. • B. amyloliquefaciens HSSN09 could effectively control watermelon Fusarium wilt and promote the growth of watermelon seedlings. • Tacrolimus has a very obvious antifungal effect and can be used to control watermelon Fusarium wilt. • Tacrolimus was also able to stimulate the growth of watermelon seedlings. • Tacrolimus or its analogs may play a role as a pleiotropic factor in B. amyloliquefaciens HSSN09 biological control. Watermelon Fusarium wilt caused by Fusarium oxysporum f. sp. niveum (FON) is one of the most devastating diseases in watermelon production. Biological control approaches are efficient and environmentally-friendly, thus have aroused broad interest. However, only a few biocontrol factors/molecules have been characterized due to varied genomes and diversified secreted secondary metabolites of biocontrol microorganisms. We report the screen and identification of a Bacillus amyloliquefaciens strain HSSN09 with high antagonism to FON and watermelon growth promotion capacity. B. amyloliquefaciens HSSN09 and its secondary metabolites showed inhibition on FON mycelial growth, spore formation and spore germination. Metabolomes of the highly antagonistic strain B. amyloliquefaciens HSSN09, medium antagonistic strain B. amyloliquefaciens FGW53, weakly antagonistic strain B. subtilis JC03 and non-antagonistic strain B. cereus FGW109 were compared with LC-MS/MS. By antagonistic assay, tacrolimus was screened out among the 531 molecules that appeared in the sequencing results of HSSN09 metabolome but not in that of the non-antagonistic strain without significant inhibition on the growth of FON. Among the four tested Bacillus strains, tacrolimus analogue was only observed in the supernatant of HSSN09 by HPLC and MALDI-TOF-MS. We further confirmed the ability of tacrolimus to suppress FON and promote watermelon seedling growth. [ABSTRACT FROM AUTHOR]

Plant gray mold disease caused by necrotrophic pathogen Botrytis cinerea , has been a serious threat to many important crops. It is urgent and necessary to seek an effective and environmentally friendly control strategy to control grey mold disease during the crop production. Moreover, it is also urgently needed to clear understand how the strategy works. To screening an efficient biocontrol agent in control of gray mold disease caused by B. cinerea , one hundred strains, which have the potential in controlling plant diseases, were selected from our laboratory’s strain library, and employed to our research. The results in the study indicated that Bacillus velezensis could act as a potential and efficient biocontrol agent (BCA), and two B. velezensis strains 5YN8 and DSN012 were screened out with high antagonistic and hydrolase activity, which could significantly control pepper gray mold disease and promote the pepper growth. Further deeply study on biocontrol mechanism indicated that B. velezensis could suppress the growth and spore formation of B. cinerea by secreting some secondary metabolites or releasing numbers of volatile organic compounds (VOCs). In the other hand, we also found that B. velezensis could trigger plant basal immunity. The BCA could increase the expression of SA signal markers and plant defense related genes. It was able to induce hydrogen peroxide accumulation and plant related enzyme activities in leaves of pepper as well. This study provides another high-efficiency, and potential strategies for the biological control of gray mold disease. It is the first report of B. velezensis strain which can control gray mold disease, In addition, it is also the first to comprehensively illustrate how the strains can efficiently protect pepper from B. cinerea attacking. [ABSTRACT FROM AUTHOR]

When two parasitoids exploit a common host simultaneously, competitive interactions between them usually occur, and are more complex among host-killing species. Diglyphus isaea (Walker) and Neochrysocharis formosa (Westwood) are larval parasitoids of agromyzid leafminers. They have widespread distributions and share the same host resources when sympatric. In this study, interactions between these two parasitoids and different parasitoid release modes were investigated. Parasitoids were exposed to leaves infested with late second to early third instar Liriomyza sativae at two different host densities in Petri dishes. The total death rate of N. formosa released alone was density-dependent. And release modes also impacted the total death rate of parasitoids at a high host density. However, the oviposition number of D. isaea was significantly greater than that of N. formosa when they coexisted. In addition, host-feeding proportions were greatest among three host-killing behaviors: parasitism, host feeding and host stinging. These results contribute to a further understanding of parasitoids’ host-killing strategies. [ABSTRACT FROM AUTHOR]

Highlights: [•] China has the largest area in the world under greenhouse vegetable. [•] Whiteflies, aphids, spider mites and thrips cause 18% production loss. [•] 14 Natural enemies used against 8 pests in 8 crops between 1988 and 2007. [•] More than 40 species of predators and parasitoids have been applied in greenhouse. [•] The importance of using native species rather than non-native agents is increasing. [ABSTRACT FROM AUTHOR]

Abstract: Of the 420 bacterial strains isolated from rhizosphere soil and the plant surface as well as the stem, leaf, and root tissue of ginger, 85 were selected for amplified ribosomal DNA restriction analysis (ARDRA) fingerprint analysis based on their antagonistic activity in vitro against Ralstonia solanacearum and on their ability to produce certain enzymes and metabolites. Of these 85, 19 antagonists from different clusters were assessed for their antagonism in greenhouse against Ralstonia wilt of ginger and biocontrol efficacies of these strains were 26.09–69.17%. In order to find out the relationship between potential and practical biocontrol ability we established an assessment system that evaluated their in vitro activity. The correlation coefficient between the assessments in vitro and biocontrol efficacies was 0.87, which indicates that this selection strategy can be used in screening biocontrol agents against plant diseases. In the greenhouse, the following strains showed biocontrol efficacies greater than 50%: Bacillus subtilis strain 1JN2, Myroides odoratimimus 3YW8, Bacillus amyloliquefaciens 5YN8, and Stenotrophomonas maltophilia 2JW6. This is the first report of using Myroides sp. and Stenotrophomonas sp. as biocontrol agents against ginger wilt caused by R. solanacearum, and these strains show promise as commercial biocontrol agents. [Copyright &y& Elsevier]

Abstract: Bacterial wilt (Ralstonia solanacearum) of tomato, Lycopersicon esculentum, causes a considerable amount of damage to tomato in Southern China. Biological control is one of the more promising approaches to reduce the disease incidence and yield losses caused by this disease. Based on antagonistic activity against R. solanacearum and three soil-borne fungal pathogens as well as biocontrol efficacy in the greenhouse, two bacterial strains Xa6 (Acinetobacter sp.) and Xy3 (Enterobacter sp.) were selected out of fourteen candidates as potential biocontrol agents. In order to find a suitable antagonist inoculation method, we compared the methods of root-dipping with soil-drenching in the aspects including rhizocompetence, biocontrol efficacy, and effect of promoting plant growth under greenhouse conditions. The drenching treatment resulted in a higher biocontrol efficacy and plant-yield increase, and this method was also easier to operate in the field on a large scale. Field trials were conducted for further evaluation of these two antagonistic strains. In both greenhouse and field experiments, the strain Xy3 had a better control effect against bacterial wilt than Xa6 did, while Xa6 caused higher biomass or yield increases. As recorded on the 75th day after treatment in two field experiments, biocontrol efficacy of Xy3 was about 65% in both field trials, and the yield increases caused by Xa6 were 32.4 and 40.7%, respectively, in the two trials. This is the first report of an Acinetobacter sp. strain used as a BCA against Ralstonia wilt of tomato. [Copyright &y& Elsevier]

Abstract: Biocontrol efficiency of various Bacillus preparations (BB11 and FH17 strains, and a mixture of both strains (BF) at a 1:1 ratio by concentration) and different application methods against Phytophthora blight of bell pepper were studied. The application methods included (A) mixing (mixing BF with rapeseed residue and then immediately applying in the field), (B) composting (mixing BF with rapeseed residue and made compost before application), (C) spraying (spraying diluted BF into field or rhizosphere of plants), and (D) watering (watering diluted BF into field or rhizosphere of plants). In greenhouse experiments, the addition of BF increased biocontrol efficiency (60.3%), and yield increase (200%) was better than with BB11 (55.8 and 80.6%, respectively) or FH17 (37.1 and 50.0%, respectively). In field trials at Huai’an in 2001, the best dosages of BF mixture (1010 cfu/ml) with the four above-mentioned application methods were 15, 7.5, 15, and 22.5L/ha, respectively. When preparations were applied at the best dosage in the same field, the BF mixture provided superior biocontrol efficiency and greater yield increase with treatment B than those with treatment A or C. Combining the field trial results from 2002 to 2003 at Huai’an and Wu’han, the total average control efficiencies and yield increases for treatments A, B, and C reached 81.0, 88.0, and 79.1% and 33.1, 44.3, and 29.1%, respectively, with their best dosages. However, method B, composting, provided better disease control and greater yield increases than all other methods, and did so at a lower application rate. [Copyright &y& Elsevier]