Adaptability and genetic stability of hepatitis A virus SYX_1 strain in human diploid cell MRC-5 / 中国生物制品学杂志

@#Abstract：Objective To investigate the adaptability and genetic stability of hepatitis A virus（HAV）SYX1 strain in human diploid cell MRC⁃5. Methods HAV SYX1 strain isolated from feces of patients with hepatitis A was continuously propagated in MRC⁃5 cells for 28 passages，of which the 1st ~ 26th passages were determined for antigen contents and virus titers，the 6th passage was observed for the morphology under microscope and detected for physicochemical properties，and the 13th ~ 15th passages were studied for virus proliferation dynamics to determine the peak yield of virus proliferation. Genomic RNA was extracted from the 8th，12th，18th，20th，22nd，25th，26th and 28th passages and sequenced to analyze the genetic stability. The main seed batch and working seed batch of HAV SYX1 strain were established and verified according to the requirements of Chinese Pharmacopoeia（VolumeⅢ，2020 edition）. Results The antigen content of HAV SYX1 was stable at 160 ~ 320 EU／mL and the titer was maintained at 7. 3 ~ 8. 3 lgCCID50／mL after the 8th passages in MRC 5 cells；Virus particles showed two types：hollow and solid，with a diameter of 27 ~ 32 nm，spherical，without envelope and protrusions on the surface，which tolerated low pH value and ether. The peak period of virus proliferation was 10 d with an antigen content of more than 160 EU／mL and a virus titer of more than 7. 0 lgCCID50／mL. HAV SYX1 was a subtype of HAV IB，and no mutation in the coding region of all structural proteins during passage was observed. The verification results of main seed batch and working seed batch of HAV all met the relevant requirements. Conclusion HAV SYX1 strain showed good adapt⁃ ability and genetic stability in MRC⁃5，which might be used for the development and production of inactivated hepatitis A vaccine.

Evaluación de ocho líneas de arveja arbustiva (Pisum sativum L.) en seis ambientes de la zona cerealista de Nariño / Evaluation of eight shrub pea lines (Pisum sativum L.) in six environment of the Nariño cerealist zone

RESUMEN La arveja arbustiva tiene características potenciales para la agroindustria y comercio en fresco y puede ser una alternativa para la zona cerealista de Nariño. La presente investigación, se realizó en dos municipios (Yacuanquer y Guaitarilla), pertenecientes a la zona cerealista de Nariño, durante tres épocas de siembra, en el 2017. La combinación de localidades por épocas constituyeron los seis ambientes estudiados. Se evaluaron ocho líneas de arveja arbustiva por número de vainas por planta, adaptabilidad y estabilidad fenotípica, para rendimiento en vaina verde y reacción a enfermedades foliares. En número de vainas sobresalieron GRICAND404 y GRICAND402. El análisis de adaptabilidad y de estabilidad fenotípica permitió identificar, como ambientes favorables, a Yacuanquer abril, Guaitarilla abril y Yacuanquer marzo; GRICAND405, con un rendimiento promedio de 9,27t.ha-1, se consideró una línea adaptable y predecible en los seis ambientes evaluados y GRICAND406, con 9,07t.ha-1, fue predecible y mostró mejor adaptación a los ambientes más favorables. En reacción a las enfermedades evaluadas, todas las líneas fueron susceptibles al ataque del complejo Ascochyta y el porcentaje de infestación de la enfermedad, se evidenció mayor en épocas muy lluviosas, como la época 1 (siembra de marzo) y disminuyó en épocas secas, como la época 3 (siembra de mayo); el ataque de Oídio, se evidenció mayormente en la época de menor precipitación (época 3), siendo resistente la línea GRICAND402.

ABSTRACT The shrub pea has potential characteristics for agroindustry and fresh trade and can be an alternative for the cereal zone of Nariño. The present investigation was carried out in two municipalities (Yacuanquer and Guaitarilla) belonging to the Nariño cereal zone during three sowing seasons in 2.017; the combination of the localities by the times was the six environments studied. Eight shrub pea lines were evaluated by number of pods per plant, adaptability and phenotypic stability to yield in green pod and reaction to foliar diseases. The number of pods stood out GRICAND404 and GRICAND402. The analysis of adaptability and phenotypic stability made it possible to identify the favorable environments for Yacuanquer april, Guaitarilla april and Yacuanquer march; GRICAND405 with an average yield of 9.27t.ha-1 was considered the adaptable and predictable line in the six environments evaluated and GRICAND406 with 9.07t.ha-1 was predictable and showed better adaptation to the most favorable environments. In reaction to diseases, all the lines were susceptible to attack by the Ascochyta complex and the percentage of infestation of the disease was greater in very rainy seasons such as season 1 (march sowing) and decreased in dry seasons such as season 3 (planting of may), the attack of Oídio was evidenced mainly in the period of least precipitation (season 3), being resistant the GRICAND402 line.

Standardization and quality assessment for clinical grade mesenchymal stem cells from human adipose tissue

Abstract Background Mesenchymal stem cells have immense potential in stem cell-based therapies, however there is a pre-requisite to develop a curative cell dose. Adipose tissue-derived mesenchymal stem cells are promising mainly due to their potential abundance, immunomodulatory effect and remarkable differentiation potential. Nevertheless, senescence may develop during their in vitro expansion due to the incidence of genetic instability. Hence, it is important to attain an ideal balance between mesenchymal stem cell growth, quality and genetic integrity before their clinical use. Methods Stromal vascular fraction was obtained from omentum tissue of patients undergoing liposuction procedures for morbid obesity. This study standardized a closed system protocol which can be utilized for clinical grade stem cell derivation. Stages of cell growth and characterization of human adipose tissue-derived mesenchymal stem cells were also assessed along with the chromosomal stability in these in vitro cultures. Results Human adipose tissue-derived mesenchymal stem cells maintained their spindle-shaped morphology and were able to proliferate and renew, confirming their suitability for in vitro cultivation and generate clinical grade mesenchymal stem cells. Immunophenotyping indicates that the cells expressed cluster of differentiation (CD)73/CD90/CD105, mesenchymal stem-cell markers, while lacked CD34/CD45/ Human Leukocyte antigen-antigen D related (HLA-DR) expression (hematopoietic cell markers). A cell cycle study demonstrated growth kinetics under in vitro culture conditions. Human adipose tissue derived mesenchymal stem cells expressed normal cell karyotype by chromosomal G-banding indicating their genetic stability at Passage 5. Mesenchymal stem cells also demonstrated trilineage differentiation. Conclusions Availability of adipose tissue in abundance is a major advantage for clinical applications. Furthermore, detailed characterization of human adipose tissue-derived mesenchymal stem cells, their genomic stability and differentiation potential from stromal vascular fraction of human adipose tissue would help assist in tissue regeneration and repair.

Successive subculture and genetic stability of hepatitis A virus vaccine strain H2 / 中华实验和临床病毒学杂志

Objective@#To investigate the genetic stability of virus seed H2M20K7 (K7) of live attenuated Hepatitis A virus H2 strain (HAV, H2 strain) for production of hepatitis A (Live) vaccine, lyophilized after continuous passages.@*Methods@#The virus seed K7 of H2 strain was proliferated and passaged in KMB17 cells in cell factories. Viruses of different passages were harvested after continuous passages. Virus RNA was extracted and the complete genomes of different virus passages (K7, K10, K11, K13, K15, K18) were sequenced by using next-generation deep sequencing. The mutation rates of different passages were compared. The infectivity titers of different virus passages of H2 strain were tested by ELISA.@*Results@#The mutation rates of complete genomes of different passages were low after continuous passages of master virus seed. The structure of gene was stable and non-synonymous mutation rate was lower than 0.57%. The mutation rate of 5 ’non-coding regions was lower than 0.1%. There was no significant mutation in VP1/2 A and 2C virulence site. The infectious titers of H2 strains of different passages were within 7.76-8.50 lgCCID50/ml. No statistically significant difference was found in this study.@*Conclusions@#The gene structure of the master virus seed, working seed and different passages of H2M20K7 after subculture was stable and the mutation rate was low. No significant mutation was found in 5’non-coding regions, and the critical virulence sites such as VP1/2 A, 2B and 2C showed attenuated characteristics with low mutation rate. Virulence of the virus did not changed. The H2 strain maintained stable viral infectivity and genetic stability and comply with the requirements as virus seed for vaccine manufacturing.

RAPD analysis of genetic diversity of Dioscorea opposita germplasm resources from Jiangxi and genetic stability of their plantlets / 中草药

Objective: To analyze the genetic diversity of 11 varieties of Dioscorea opposita germplasm resources from Jiangxi, and detect the genetic stability of the tissue cultured plantlets. Methods: RAPD-PCR was applied. Results: Twenty primers were screened out, 238 bands were amplified, 234 of them were polymorphic bands, the average amplified polymorphic bands were 11.7, and the ratio of polymorphic bands was 98.32%. The genetic similarity coefficient was 0.575 6-0.970 6 and the average similarity coefficient was 0.723 1. According to the results of UPGMA clustering analysis, the 11 D. opposita germplasm resources from Jiangxi province were divided into five categories: The first class included D. bulbifera. The second class included D. opposita. The third class included D. opposita Nancheng 1, D. opposita, D. opposita, D. opposite, and D. opposita, which showed that D. opposita 1, D. opposita, D. opposita and D. opposite, had closer relationship with D. opposita came from Wenxian County, Jiaozuo City, Henan province. The fourth class included D. opposita, D. opposita Nancheng 2 and D. opposita. The fifth class included D. opposita. The RAPD analysis results of plantlets subcultured for six times by in vitro rapid propagation method of stem segment with a bud of D. opposita L. germplasm resources from Jiangxi province (treatment group) and their seedlings germinated from microtuber (control group) also showed that 11 yam varieties were spread out 126-179 identifiable bands and each variety appeared 5-18 mutation bands, which indicated plantlets subcultured for six times by in vitro rapid propagation method of stem segment with a bud of D. opposita. germplasm resources from Jiangxi province existed somaclonal variation, but their genetic similarity coefficient compared with their seedlings germinated from microtuber was still relatively high, illustrating that their genetic traits were still relatively stable and did not affect their genotype. Conclusion: The experimental results can provide the reliable basis for introduction breeding, resource improvement, variety identification, germplasm conservation, and their plantlet culture of D. opposita germplasm resources from Jiangxi province.

Micropropagación de plantas de lechosa en recipientes de inmersión temporal a partir de brotes axilares / Micropropagation of papaya plants in temporary immersion recipients from axilary shoots

Se estandarizaron las condiciones de iniciación, multiplicación, enraizamiento y aclimatización de plantas hermafroditas de lechosa cv Maradol provenientes de brotes axilares, producidos en recipientes de inmersión temporal RITA®. En cada envase, contentivo de 200 ml de medio de cultivo líquido de Fitch, se colocaron cuatro brotes de 2 a 3 cm de longitud. Los biorreactores se conectaron a tres líneas de inmersión de 5, 2 y 1 min cada 4h y se colocaron 6 envases en promedio por línea, en condiciones de fotoperíodo de 16 h. Transcurridos 30 a 45 días, se cuantificaron los brotes y se clasificaron de acuerdo al tamaño: < 2 cm (pequeños), entre 2 a 3 cm (medianos), > 3 cm con y sin raíz (grandes). Los dos primeros tipos de brotes se continuaron multiplicando en los mismos medios; y los más elongados se aclimatizaron utilizando el Sistema Autotrófico Hidropónico (SAH). Se determinó la sanidad y la fidelidad de las plantas producidas mediante pruebas de ELISA y RAPD, respectivamente. Durante un periodo de 6 meses se reciclaron un total de 47 recipientes, los cuales produjeron 1.091 brotes: 377 pequeños; 482 medianos; 175 grandes sin raíz y 57 con raíz. Usando el SAH se obtuvo 89,5% de plantas aclimatizadas cuando se usaron brotes enraizados, y 41,6% a partir de brotes sin raíces. Con la combinación de las técnicas RITA y SAH se logró un sistema continuo y eficiente de producción de plantas sanas y fieles al tipo, en comparación con los métodos convencionales de micropropagación y aclimatización.

We standardized initiation, multiplication, rooting and acclimatization conditions of papaya cv Maradol hermaphrodite plants from axillary buds produced in temporary immersion reactor RITA®. Recipients contained 200 ml of Fitch liquid culture medium, and four shoots of 2 to 3 cm. in length were placed in each. The bioreactors were connected to three different immersion lines of 5, 2, and 1 min each 4h, with 6 containers per line on average, in 16 h photoperiod. After 30 to 45 days, the shoots produced were quantified and classified according to size: <2 cm (small), from 2 to 3 cm (medium), >3 cm with or without roots (large). The first two types of shoots were multiplied in the same culture media, and more elongated shoots were acclimatized using Autotrophic Hydroponic System (AHS). The sanity and fidelity of the produced plants were determined using ELISA and RAPD, respectively. For a period of six months 47 vessels were recycled and 1,091 shoots were produced: 377 small; 482 medium; 175 large without roots and 57 rooted shoots. Using AHS, 89.5% acclimatized plants were obtained when rooted shoots were used, and 41.6% from rootless shoots. With the combination of RITA and AHS techniques we achieved a continuous and efficient production of healthy and true to type papaya plants, in comparison to conventional micropropagation and acclimatization procedures.

Analysis of the genetic stability of the master virus seeds for live attenuated influenza vaccine produc-tion / 中华微生物学和免疫学杂志

Objective To analyze the genetic stability of master virus seed lots of live attenuated influenza vaccineA/17/California/2009/38(H1N1)andA/17/Perth/09/87(H3N2)strains.Methods The master virus seed lots were inoculated into chicken eggs for subculture.The complete genome of the 2nd, 3rd, 5th and 10th generations of viruses were amplified and sequenced.The genes encoding hemagglu-tinin ( HA) and neuraminidase ( NA) were compared with those of the WHO recommended circulating wild-type virus strains used for vaccine production in northern hemisphere during 2011-2012 influenza season.Six internal genes (PB2, PB1, PA, NP, M and NS) of each virus generation were compared with their master donor virus strain (A/Leningrad/134/17/57) for the evaluation of the genetic stability.Results The muta-tion rates of H1N1 and H3N2 strains after 10 passages were 0.035%and 0.022%, respectively.No muta-tions were found at the critical sites for controling thecold adapted ( ca) , temperature sensitive ( ts) and at-tenuated ( att) phenotypes.Conclusion The live attenuated influenza vaccine strains possessed high genet-ic stability as their tenth generations still shared 99% of homology with the original seed lots.All of the working virus seed lots met the requirements of Pharmacopoeia of the People′s Republic of China ( 2010 edition) .

Evaluación del potencial mutagénico de biocidas (vertimec y pentacloro) sobre cebolla / Evaluation of the mutagenic potential of biocides (vertimec and pentachloro) on onion

El uso de biocidas es una constante en el campo agronómico, el daño ocasionado a los cultivos y por consiguiente el gran potencial de daño para los consumidores es conocido, sin embargo su uso sigue en marcha. Por ello se realizaron pruebas citogenéticas para la observación de aberraciones cromosómicas en Allium cepa, usando muestras de raíces de plantas expuestas y no expuestas a biocídas. Los tratamientos se realizaron con el objetivo de comparar el grado de afectación de los biocídas sobre la mitosis y la ocurrencia de mutaciones cromosómicas. El ANOVA para los datos de desarrollo radicular al finalizar la experimentación, mostraron un CV de 9.88, se observo diferencias significativas entre el control y los tratamientos, los porcentajes de inhibición llegaron a tener valores máximos de 84.2% para vertimec X8 y 76.5% para pentacloro X8, y valores mínimos de 38.2% para vertimec X0.5 y 43.8% para pentacloro 0.5 X. El índice mitótico fue mayor para el control (0.193) y menores para el tratamiento con menor desarrollo radicular, vertimec X8 (0.021) y pentacloro X8 (0.028). Las pruebas citogenéticas mostraron la ocurrencia de anomalías en el ciclo celular siendo la más frecuente la C-mitosis. Se puede concluir que el test Allium es un buen indicador de citotoxicidad y genotoxicidad. Los biocidas ocasionan cambios en la estructura genómica de un cultivo, estos cambios podrían acumularse y ocasionar cambios de expresión génica, pudiendo dañar regiones de interés agronómico para una especie y afectar su estabilidad genética.

Use of biocides is a constant in the agronomic field, the damage to crops and therefore the potential for harm to consumers is known, however its use is ongoing. Therefore, tests were performed to observe cytogenetic aberrations in Allium cepa using plant root samples exposed and not exposed to biocides. Treatments were performed in order to compare the degree of impact of biocides on mitosis and the occurrence of chromosomal mutations. The ANOVA for root development data at the end of the experiment showed a CV of 9.88, significant differences was observed between control and treatments; the inhibition percentages have reached maximum values of 84.2% for Vertimec X8 and 76.5% for pentachloro X8, and minimum values of 38.2% for Vertimec X0.5 and 43.8% for pentachloro X0.5. The mitotic index was higher for control (0.193) and lower for treatment with less developed root Vertimec X8 (0.021) and pentachloro X8 (0.028). Tests showed the occurrence of cytogenetic abnormalities in the cell cycle being the most frequent C-mitosis. It can be concluded that the Allium test is a good indicator of cytotoxicity and genotoxicity. Biocides cause changes in the genomic structure of crops; these changes may accumulate and cause gene expression changes, can damage agronomic interest regions for a species and affect their genetic stability.

Evaluation of cassava plants generated by somatic embryogenesis at different stages of development using molecular markers

Background: Cassava (Manihot esculenta Crantz) is a crop that is high in carbohydrates in the roots and in protein in the leaves, important for both human consumption and animal feed, and also has a significant industrial use for its starches. In this study we evaluated the genetic variability with molecular markers in different stages in micropropagated plants from somatic embryos of Venezuelan native clone 56. Results: Three markers were used: ISTR, AFLP and SSR, finding that ISTR showed the highest polymorphism among individuals tested. With AFLP a high similarity between the evaluated individuals was observed and with SSR total monomorphism was seen. Using cluster analysis it was found that individuals from an embryo labeled as fasciated at the beginning of the somatic embryogenesis process were grouped as independent of the other plants when analyzed at the acclimatization stage. The differences found with the different markers used are discussed. In field trials, micropropagated plants had a yield between 4 and 5 times the average yield of cassava in Venezuela. Conclusion: Despite variability in terms of DNA markers, somatic embryogenesis is suitable for mass propagation of highly performing cassava clones.

Variação somaclonal nos descritores mínimos de tubérculo em batata / Somaclonal variation in minima descriptors of tuber in potato

Em batata, a cultura de tecidos é utilizada para recuperar cultivares infectadas por viroses, entretanto, o cultivo in vitro pode conduzir à variação somaclonal. O presente estudo teve como objetivos identificar somaclones e avaliar o efeito do tipo de explante e do tempo de subcultivo sobre a ocorrência de variantes somaclonais nas cultivares 'Asterix' e 'Macaca'. Tubérculos produzidos em plantas regeneradas por organogênese direta e indireta de explantes derivados do cultivo de ápices caulinares de clones em subcultivo há 12 (clone novo) ou 70 (clone velho) meses em meio nutritivo MS e cultivadas em campo foram avaliados em relação a seis descritores mínimos da batata. As médias observadas foram comparadas aos padrões descritos para as cultivares e somente foram consideradas somaclones aquelas que foram enquadradas em uma classe fenotípica diferente do padrão da cultivar respectiva. Em 'Asterix' e 'Macaca' ocorreram somaclones em quatro e dois descritores, respectivamente, contudo, apenas no formato e cor da polpa do tubérculo, houve variação somaclonal, simultaneamente, nas duas cultivares. Variantes somaclonais podem ser identificadas pelo uso dos descritores mínimos de tubérculo. 'Asterix' e 'Macaca' são, igualmente, suscetíveis à ocorrência de variação somaclonal, mas esse fenômeno afeta de maneira diferenciada os descritores mínimos nas duas cultivares. O tempo de subcultivo age diferencialmente sobre as características morfoagronômicas.Doze meses de subcultivo já são suficientes para originar somaclones. Segmentos apicais caulinares e segmentos nodais, originados por organogênese direta ou indireta, são explantes igualmente instáveis para a produção de batata-semente.

In potato, tissue culture is used to retrieve cultivars infected by viruses, however, in vitro culture can lead to somaclonal variation. This study aimed to identify somaclones and evaluate the effect of type of explant and subculture time on the occurrence of somaclonal variants in cultivars 'Asterix' and 'Macaca'. Tubers produced in plants regenerated by direct and indirect organogenesis of shoot apical and nodal segments derived from the culture of shoot tips of clones in subculture for 12 (young clone) or 70 (old clone) months in nutritive medium MS and cultivated in field were assessed in six minima descriptors of the potato. The averages were compared to patterns described for the cultivars and somaclones were considered only those that were framed in a different phenotypic class from standard of cultivar. In 'Asterix' and 'Macaca' somaclonal variants were observed in four and two descriptors, respectively, however, only in the tuber shape and flesh color occurred somaclonal variation simultaneously in both cultivars. Moreover, remained stable the depth of the eyes and the greening of the tuber. Somaclonal variants can be identified by use of minima descriptors of tuber. 'Asterix' and 'Macaca' are equally susceptible to somaclonal variation. Twelve months of subculture is enough to cause somaclones in both cultivars. Shoot apical and nodal segments derived by direct or indirect organogenesis, are explants equally unstable to the production of seed potatoes.

Biological Characteristics of Mesenchymal Stem Cells during Ex Vivo Expansion.

Mesenchymal stem cells (MSC) have been widely used in different areas of medicine because of their immunosupressive properties and influence on regeneration of the damaged tissues. The objective of this study was to examine the kinetics of growth (MSC from 4-3 passages had significantly higher proliferative activity compared with cultures of 10-12 passages), changes in immunophenotypic characteristics of human MSC in early (3-4) and late (10-12) passages when cultured in vitro as well as study of genetic stability. In the analyzed cultures of MSC was found normal karyotype (46, XY or 46, XX). In most of cultures studied MSC karyotype and the level of aneuploidy remained unchanged even after prolonged culturing. The author's experience of ex vivo expansion of MSC using both standard medium DMEM with the supplementation of fetal bovine serum (FBS) and serum-free medium MesenCult MSC Basal Medium (Human) (StemCell technologies Inc.) with addition of Mesenchymal Stem Cell Stimulatory Supplements (Human) is presented. The influence of the type of medium on the growth and immunophenotype of MSC is analyzed. The study found that when cultured in serum-free medium proliferative potential of MSCs was lower.

Persistence of DDT, malathion & deltamethrin resistance in Anopheles culicifacies after their sequential withdrawal from indoor residual spraying in Surat district, India.

Background & objectives: Under the national antimalaria programme DDT was introduced in early 1950s for vector control and later hexachloro cyclohexane (HCH) followed by malathion and recently synthetic pyrethroids in 1990s to manage the insecticide resistance in Anopheles culicifacies. Subsequent replacement led to development of multiple resistances in An. culicifacies in Surat district in Gujarat State. Indoor residual spray (IRS) was completely withdrawn in southern villages in Surat in 2002. This study was undertaken in these areas to study the persistence of resistance to DDT, malathion and deltamethrin after sequential withdrawal of IRS with these insecticides at different times. Methods: Susceptibility tests on An. culicifacies were conducted using standard WHO methods and kits. Mortality, knockdown time and lethal times were calculated for An. culicifacies exposed to WHO prescribed diagnostic concentrations of different insecticide impregnated papers. Results: Persistence of DDT-resistance was observed even after 30 yr of its withdrawal from IRS. Similarly, persistence of malathion resistance was also observed after 9 yr of its withdrawal from IRS, while reversal of deltamethrin-resistance was observed very fast within 2-3 yr after its withdrawal from IRS in 2002. Interpretation & conclusion: Present data indicate that the quantum of reversion of insecticide resistance in a population is relative and depends on the genetic stability of the respective resistance genes in the mosquitoes. In the present study withdrawal of pyrethroid-IRS resulted in increased susceptibility against pyrethroids alone and was independent of existence of resistance to insecticides of other groups. This study emphasizes that appropriate rotation of different insecticides; including carbamates may prevent or delay the onset of resistance.

Using antisense nucleic acid technology to study the influence of POL? on genetic stability / 中国病理生理杂志

AIM: To establish cell line FL-POL? - and to study the role of POL?(polymerase kappa) on genetic stability. METHODS: A mammalian expression vector expressing antisense POL? gene fragment pMAMneo -amp -- POL? was constructed by cloning the 1 690-1 918 fragment of POL? gene into the mammalian expression vector pMAMneo-amp - in antisense orientation. FL cells were fransfected with this antisense RNA expressing vector and selected by G418. Based on the shuttle-plasmid pZ189, the mutation assay was made. RESULTS: The spontaneous mutation frequency of supF tRNA gene in the plasmid replicated in the FL-POL? - was 11.2?10 -4 , while it was 4.9?10 -4 and 3.7?10 -4 in the control cells FL and FL-M , respectively. CONCLUSION: POL? playes an important role in maintenance of genetic stability.

Genetic Stability of a Recombinant Biocontrol Bacteria 308R(pKSH) / 微生物学通报

Biocontrol bacteria 308R(pKSH) with hrpN of Erwinia amyloyora. It can secrete the Harpin protein which can induce plant resistance. After successive growth in antibiotic-free LB medium for 50 generations, only 23.1% of the cell still retained the plasmid pKSH, in comparison with 4.75% of the cosmid pCPP430. Sprayed onto the leaves of tomato, the recombinant strain maintained a population density of over 10~ 5 cfu/cm~ 2 when kept under high humidity in thirteen days, but if without humidity, the strain keep 10~ 4 cfu/cm~ 2 over in five days. On the tomato leaves, the stability of the recombinant strain 308R(pKSH) was higher than the strain 308R(pCPP430). The experiment indicated that the recombinant strain 308R(pKSH) had higher stability compared with the strain 308R(pCPP430), but that was not enough. In this paper reasons for unstability and strategies for improving were discussed for the recombinant strain.