[Identification of Pantoea agglomeran XM2 with biocontrol activity against postharvest pear black spot].

OBJECTIVE: We isolated the bacterial strain XM2 from prunes (Prunus domestica L.) fruit surface. XM2 was identified and tested as an antagonist for postharvest biological control of black spot disease (Alternaria alternata) on pear fruits. METHODS: Strain XM2 was identified according to its morphological, physiological and biochemical characteristics and 16S rDNA sequence analysis. Inhibition tests were performed in wounds of pear fruits using different types of XM2 inocula, different concentration and inoculation time of XM2 and A. alternata. Effect of XM2 on mycelia morphology of A. alternata was observed under microscope. RESULTS: Strain XM2 was identified as Pantoea agglomeran. Biological control of XM2 against black spot disease was significantly better than the control, and the best inhibitory was observed when inoculated with suspension (97.73% of control effect). Higher XM2 concentration and lower A. alternata concentration showed better inhibitory effect. Similarly, the earlier inoculation of XM2 than A. Alternata, the better inhibitory effect on disease development. Microscopic observation found that XM2 broke part of the mycelia, making cell contents spilled and hyphae distorted. CONCLUSION: Pantoea agglomeran XM2 has the potential as an effective antagonist against postharvest pear blank spot disease.

Construction of A GBS-Based High-Density Genetic Map and Flower Color-Related Loci Mapping in Grasspea (Lathyrus sativus L.).

Grasspea (Lathyrus sativus L.), a legume crop with excellent resistance to a broad array of environmental stressors, has, to this point, been poorly genetically characterized. High-density genetic linkage maps are critical for draft genome assembly, quantitative trait loci (QTLs) analysis, and gene mining. The lack of a high-density genetic linkage map has limited both genomic studies and selective breeding in grasspea. Here, we developed a high-density genetic linkage map of grasspea using genotyping-by-sequencing (GBS) to sequence 154 grasspea plants, comprising 2 parents and 152 F2 progeny. In all, 307.74 Gb of data was produced, including 2,108,910,938 paired-end reads, as well as 3536 SNPs mapped to seven linkage groups (LG1-LG7). With an average length of 996.52 cM per LG, the overall genetic distance was 6975.68 cM. Both the χ2 test and QTL analysis, based on the Kruskal-Wallis (KW) test and interval mapping (IM) analysis, revealed the monogenic inheritance of flower color in grasspea, with the responsible QTL located between 308.437 cM and 311.346 cM in LG4. The results can aid grasspea genome assembly and accelerate the selective breeding of new grasspea germplasm resources.

In utero antiretroviral exposure and sociodemographic characteristics on neurodevelopment of HIV-exposed uninfected children versus HIV-unexposed uninfected healthy children in Malawi.

BACKGROUND: To evaluate mental development index (MDI) and psychomotor development index (PDI) scores of HIV-exposed uninfected (HEU) children by timing of in utero antiretroviral treatment (ART) initiation (Option B+) and sociodemographic characteristics compared with HIV-unexposed uninfected (HUU) children in Mzuzu, Malawi. METHODS: One hundred HEU children and 100 HUU children aged 2-30 months were recruited. The differences in MDI and PDI scores between HEU and HUU children were tested by Student's t test, analysis of variance, Mann-Whitney U test, and logistic regression analysis. RESULTS: The differences in MDI and PDI scores might be related to number of children in the family, delivery, place of residence, family income, complementary feeding, father's or mother's occupation, and degree of education. No significant difference in MDI and PDI scores between HEU and HUU children (P = 0.076 and P = 0.407) was found. Among HEU children, ART in the third trimester and beyond produced a lower PDI score compared with ART before pregnancy and in the first or second trimester (P = 0.027). CONCLUSION: The MDI and PDI scores of HEU subgroups with different timing of ART (Option B+) initiation were comparable to those of the HUU group. Early in utero ART initiation was associated with better neurodevelopmental outcomes than ART initiation in the third trimester and beyond.

[Identification of endophytic Actinomycete Lj20 from plant and its antifungal substances].

OBJECTIVE: Endophytic actinomycete Lj20 with antifungal activity was isolated from the roots of capsicum plants. We identified Lj20 and synthesized its antifungal substances. METHODS: Morphological, biological and biochemical characteristics, chemotaxonomy analysis and 16S rDNA sequences were used to identify Lj20. According to GC-MS extrapolation result, one of antifungal substances in the metabolites of Lj20 was chemically synthesized. The bioactivities were determined by mycelium growth inhibition method. RESULTS: Lj20 belonged to Streptomyces sp. and was similar to Streptomyces rochei. The metabolites contained butylated hydroxytoluene and 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether. The median effective concentration (EC50) of these two compounds to Botrytis cinerea Pers. were 237.04 mg/L of the water and 186.48 mg/L of the water, respectively. CONCLUSION: Lj20 was classified as Streptomyces rochei. Butylated hydroxytoluene and 3, 5-di-tert-butyl-4-hydroxybenzyl methyl ether had significant inhibition to the pathogen.

Functional Analysis of the Ferric Uptake Regulator Gene fur in Xanthomonas vesicatoria.

Iron is essential for the growth and survival of many organisms. Intracellular iron homeostasis must be maintained for cell survival and protection against iron toxicity. The ferric uptake regulator protein (Fur) regulates the high-affinity ferric uptake system in many bacteria. To investigate the function of the fur gene in Xanthomonas vesicatoria (Xv), we generated a fur mutant strain, fur-m, by site-directed mutagenesis. Whereas siderophore production increased in the Xv fur mutant, extracellular polysaccharide production, biofilm formation, swimming ability and quorum sensing signals were all significantly decreased. The fur mutant also had significantly reduced virulence in tomato leaves. The above-mentioned phenotypes significantly recovered when the Xv fur mutation allele was complemented with a wild-type fur gene. Thus, Fur either negatively or positively regulates multiple important physiological functions in Xv.

[Evidence of long distance migration of diamondback moth (DBM) Plutella xylostella: a review].

As cruciferous plants have been cultivated northwards due to climate warming, diamondback moth (DBM) Plutella xylostella is becoming a major pest in North China. The long distance migration of DBM not only induces its sudden outbreak over extensive areas, but also leads to its insecticide resistance by the spread of resistant genes in large area. To elucidate the long distance migration of DBM is of significance for early warning and decision-making in integrated pest managements. So far, the migration of DBM has not yet been systematically investigated in China. Here, we reviewed the literatures about the long distance migration of DBM at home and abroad, and summarized the related evidence: 1) DBM cannot overwinter in cold regions such as northern Japan, western Canada, and northeast China, where the DBM outbreak is presumed from elsewhere by long distance migration, 2) DBM adults are captured from seas, mountain tops, sea islands, and sky, etc., and the collection of large quantity of DBM presents the powerful direct evidence of DBM long distance migration, 3) the sudden increase of DBM in fields is consistent with the meteorological conditions such as the presence of nocturnal temperature inversion layer and the front passage, suggesting that these meteorological conditions supply suitable backgrounds for the insect migration, 4) the target insect characters identified by vertical insect looking radar is consistent with the measured DBM characters in laboratory and the trapping data from fields, confirming the long distance migration of DBM, 5) the biological characteristics and genetic variations of different DBM populations have no correlations with geographic distance, suggesting the frequent gene flows among the populations in different positions, and 6) the flight test of DBM indicates its long distance flight capacity, and the decreasing fitness of host plants is probably one of the trigger factors for the migration of DBM. Some future research directions are prospected: the construction of track model for DBM long distance migration to clarify the DBM long distance migration pathways in China; the further understanding on the physiological, biochemical, and ecological bases of DBM long distance migration; the strategies for the population insecticide resistance management based on the long distance migration of DBM.

[Identification of endophytic actinomycete St24 tomato plants from and its application in biocontrol of gray mold disease].

An endophytic actinomycete strain St24 with acaricidal activity was isolated from the root-stem junction of tomato plants, with the taxonomic position of the strain and its control effect against gray mold disease investigated. The St24 was identified as Streptomyces vinaceus, and its broth's petroleum ether extracts could inhibit a variety of pathogens. The inhibitory effect of the extracts on Botrytis cinerea was the strongest, with the EC50 of inhibiting B. cinerea mycelia growth being 11.78 mg x L(-1). After treated with the extracts, the amount of the mycelia decreased, and the mycelia became crenate or broken, with the protoplast extravasated and the tuberculate malformation appeared. The B. cinerea culture treated with the extracts showed the maximum absorption at 260 nm, which was absent in the control, indicating that the St24 extracts increased the pathogens cell membrane permeability. Pot experiment showed that the extracts could protect tomato plants against B. cinerea. Foliar spraying the extracts at 100 mg x L(-1) had the best protective effect, with the controlling effect reached 94.3% after 24 h and 85.4% after 120 h.

[Bioactivity of the metabolites from endophytic actinomycete Fq24 against Tetranychus cinnabarinus].

An endophytic actinomycete strain Fq24 was isolated from healthy tomato plants. The acaricidal substances in the metabolites from Fq24 were collected and identified by the methods of extraction, column chromatography, and gas chromatography-mass spectrometry (GC-MS), and their bioactivities against Tetranychus cinnabarinus were measured with slide-dip and leaf-residue methods. Among the extracts, petroleum ether extract had high bioactivity in contact toxicity and oviposition deterrent against T. cinnabarinus. Its lethal concentration of 50% (LC50) was 52.57 mg x L(-1), and its oviposition deterrent concentration of 50% (ODC50) was 43.18 mg x L(-1). The identification with GC-MS showed that the main chemical component of fraction S11 was methyl hexadecanoate, whose molecular formula was C17H34O2, being one of the substances with acaricidal activity in the metabolites from Fq24. The 24 h corrected mortality rate of female mite at 5 mg x mL(-1) of methyl hexadecanoate was 78.3%, and the oviposition deterrent rate was 81.6%.

[Effects of sub-lethal dosages abamectin on food intake and digestive enzyme activities of silkworm Bombyx mori L].

Mulberry leaves treated with sub-lethal dosages (LC5, LC10 and LC20) abameetin were fed to the 5th instar larvae of silkworm (Bombyx mori L.), and the food intake and digestive enzyme activities of the larvae were studied by using gravimetric method and measuring enzyme activities. The results showed that sub-lethal dosages abameetin significantly inhibited the growth and food intake of the larvae, with their body mass and its increase rate as well as their relative growth rate being significantly lower than the control, and accompanied with the decreases of food intake, its relative consumption rate, and feces amount. The efficiency of the conversion of ingested food (ECI) and that of the conversion of digested food (EDI) also reduced, but the approximate digestibility (AD) increased significantly. The amylase and sucrase activities in the midgut of the larvae treated with abameetin decreased significantly for a longer time at the beginning, and then recovered to the same as or a higher level than the control, whereas the trehalase activity decreased significantly for a shorter time at the beginning, then increased significantly, and finally recovered to the normal. It was suggested that sub-lethal dosages abameetin had definite toxicity to the silkworm, and the toxic effect was increased with increasing dosage, which could result in the turbulence of silkworm's digestive system, and further, affect its food intake and its growth and development.

[Interactive system of Delphastus catalinae and its competitor: interspecies competition].

Delphastus catalinae and Serangium japonicum are the important natural enemies of Bemisia tabaci, of which, the former is exotic, and the latter is indigenous. In this paper, the influence of interspecies competition on the population growth of D. catalinae and S. japonicum was studied under conditions of single and mixed rearing, and Lotka-Volterra equation was used to simulate the competition when more and less preys provided for the two ladybirds. The results showed that the population growth of D. catalinae was greater than that of S. japonicum when single rearing, and the population growth of S. japonicum was greater than that of D. catalinae when mixed rearing. In the competition system of the two ladybirds, S. japonicum was dominant, while D. catalinae could exist simultaneously.