Effect of liming on hexazinone sorption and desorption behavior in various soils

Liming is a practice commonly used to modify soil acidity, neutralize aluminum, and increase calcium and magnesium in the soil. Liming can change herbicide retention processes and consequently weed control and potential environmental contamination. The effects of liming on the sorption and desorption of hexazinone in different soils were evaluated. Samples from seven Brazilian soils were collected and separated into two subsamples, with and without limestone incubation. Hexazinone was quantified using ultra high-performance liquid chromatography. The sorption and desorption coefficients were determined in soils using Freundlich isotherms. Increasing the pH did not alter the sorption kinetics of hexazinone in the same soil class. The shortest sorption time of hexazinone occurred in soils with higher organic matter (OM) and clay content. Liming reduced the sorption and increased the desorption of hexazinone in the soils, which was caused by the increase in pH and reduction of OM content. Although the application of limestone increased desorption, the rate at which this process occurred was less than the sorption rate of hexazinone in most cases. In alkaline soils, the recommended dose of hexazinone for pre-emergence application should be low to avoid leaching and reduce the contamination of groundwater resources.     

Effect of pre- and postmating nutritional manipulation on plasma progesterone,blastocyst development,and the oviductal environment during early pregnancy in gilts

Two experiments were conducted to determine mechanisms mediating effects of nutritional manipulation before and after mating on embryonic survival in pigs. Experiment 1 studied the mechanisms by which continued high feeding levels after mating result in differences in plasma progesterone during early pregnancy. Gilts fed 2.0 times maintenance energy requirements either remained on this high level or feed was reduced to 1.5 times maintenance immediately after mating. Ovarian, oviductal, and jugular vein progesterone concentrations were determined 72 h after onset of estrus, and samples taken every 4 h were used to determine LH and progesterone during the periestrous period. Treatment did not affect peripheral progesterone concentrations, the timing or rate of rise of progesterone, or progesterone in ovarian, oviductal, or jugular veins at the time of surgery. Time after the LH peak was highly correlated (P = 0.0001) with jugular progesterone concentrations, but not with those in oviductal and ovarian veins, suggesting that responses in the reproductive tract mediated by peripheral progesterone concentrations will be temporally different to effects within tissues supplied by the ovarian and oviductal vasculature. Experiment 2 studied mechanisms mediating nutritional manipulation in the preovulatory period on postovulatory reproductive function, using feed restriction during the first (RH) or second (HR) week of the estrous cycle. Surgeries were performed 12 to 20 h after ovulation, and fertilized oocytes were cultured for 144 h in vitro. Ovulation rate was not affected by previous nutritional regimen. Fertilization rate was higher (P = 0.056) in RH vs HR gilts, but development of cultured oocytes was not affected by treatment. There were no treatment differences in peripheral or oviductal plasma progesterone, estradiol, or insulin-like growth factor-I (IGF-I) at surgery, or in porcine oviductal secretory protein abundance and IGF-I concentrations in oviduct flushings, but treatment affected total protein concentration (P = 0.002). These results indicate that either previous nutritional treatment does not affect the early developmental competence of fertilized oocytes in vitro or differences in developmental competence of oocytes are not expressed up to the early blastocyst stage. However, the lack of an effect of previous nutrition on steroids in the local oviductal circulation may also be related to the lack of effects on oviductal function and embryonic development.     

Development ofClonostachys rosea and interactions withBotrytis cinerea in rose leaves and residues

The effect of microclimate variables on development ofClonostachys rosea and biocontrol ofBotrytis cinerea was investigated on rose leaves and crop residues. C.rosea established and sporulated abundantly on inoculated leaflets incubated for 7–35 days at 10°, 20° and 30°C and then placed on paraquat—chloramphenical agar (PCA) for 15 days at 20°C. On leaflets kept at 10°C, the sporulation after incubation on PCA increased from 60% to 93% on samples taken 7 to 21 days after inoculation, but decreased to 45% on material sampled after 35 days. A similar pattern was observed on leaves incubated at either 20° or 30°C. The sporulation ofC. rosea on leaf disks on PCA was not affected when the onset of high humidity occurred 0, 4, 8, 12 or 16 h after inoculation. However, sporulation was reduced to 54–58% on leaflets kept for 20–24 h under dry conditions after inoculation and before being placed on PCA. The fungus sporulated on 68–74% of the surface of leaf disks kept for up to 24 h at high humidity after inoculation, but decreased to 40–51% if the high humidity period before transferral to PCA was prolonged to 36–48 h. The growth ofC. rosea on leaflets was reduced at low inoculum concentrations (10³ and 10⁴ conidia/ml) because of competition with indigenous microorganisms, but at higher concentrations (10⁵ and 10⁶ conidia/ml) the indigenous fungi were inhibited. Regardless of the time of application ofC. rosea in relation toB. cinerea, the pathogen’s sporulation was reduced by more than 99%. The antagonist was able to parasitize hyphae and conidiophores ofB. cinerea in the leaf residues. AsC. rosea exhibited flexibility in association with rose leaves under a wide range of microclimatic conditions, and in reducingB. cinerea sporulation on rose leaves and residues, it can be expected to suppress the pathogen effectively in rose production systems.     

Differentiation of Xanthomonas species Pathogenic to Sugarcane by PCR-RFLP Analysis

The PCR-RFLP of the 16S-23S rDNA spacer region was used to differentiate Xanthomonas species pathogenic to sugarcane. Strains of X. albilineans, X. campestris pv. vasculorum Types A and B, X. sacchari and Xanthomonas sp. from Trinidad, South Africa and India were examined. The amplification products were digested with Alu I, Hae III, Hpa II and Mbo I and the results showed that the different groups of bacterial strains exhibited distinct RFLP patterns for each tested endonuclease, except X. albilineans and X. sacchari which could only be differentiated from each other by the digestion with Hpa II. The results also allowed the separation of X.c. pv. vasculorum Type A from X.c. pv. vasculorum Type B and strongly suggested that the analyzed Xanthomonas sp. strains belong to X. sacchari. Nine X. campestris (pv. not determined) strains included in this study showed identical profiles to X.c. pv. vasculorum Type A group and DNA–DNA hybridization experiments confirmed these results. PCR-RFLP of the 16S-23S rDNA spacer region could be applied as a reliable method for differentiating the xanthomonads pathogenic to sugarcane.     

中国六个白灵菇(Pleurotus nebrodensis) 商业菌株的DNA指纹图谱分析

Pleurotus nebrodensis(Inzengae)Qulet wasfirst described by Inzengae in1863asAgaricusnebrodensis,and subsequently renamedPleurotusnebrodensisin1886(VENTURELLA,2000).InChina,the species is found only in the Xinjiangregion(MAO,2000).Xinjiang researcherscommenced domesticationofthis mushroomin1987,andthe first commercial strain was obtainedin1997(HUANG,1997).Since then,the popularity ofP.nebrodensisin Asia has increased due to itsdesirable organoleptic qualities and market value,and man…     

Micropropagation of the Brazilian endemic bromeliad Vriesea reitzii trough nodule clusters culture

Vriesea reitzii Leme & Costa is an endemic bromeliad from the Atlantic Forest in South Brazil. The devastation of this biome threatens the extinction of this species that besides its role in the ecosystem has an ornamental value. Tissue culture techniques are important tools for the mass propagation of threatened bromeliad species. In the present work we established an in vitro regenerative protocol for the large-scale propagation, and improvement of this species. Young basal leaves used as explants showed 90.6% induction rate of nodule clusters in MS culture medium supplemented with 20.0 μM 2,4-D and 1.0 μM Kin. The subculture of these nodule clusters to MS medium with BAP, Kin and 2-iP resulted in a regeneration rate of 60 shoots/g nodule clusters. Subsequent subculture to MS media supplemented with 2.5 μM 2-iP and 0.5 μM NAA and then to MS medium free of PGR enhanced the full development of plantlets. Plantlets longer than 3 cm were successfully acclimatized showing a survival rate of 90%.     

Viral reinfection affecting bulb production in garlic after seven years of cultivation under field conditions

Six sequential field experiments were conducted from 1999 to 2002 to evaluate virus reinfection in garlic cv. Amarante and its effect on bulb production. The treatments in the year 1999 were: T₁ – virus-free garlic-seed obtained by thermotherapy and meristem-tip culture and indexed for virus by immuno-sorbent electron microscopy (ISEM) under its first field cycle; T₂, T₃ and T₄ – garlic-seed in the second, third and fourth field cycles, respectively; and C – standard garlic-seed from the grower (with no control of virus infection) as a control. In the years 2000 to 2002, a new plot of virus-free seed was added to the experiment and cloves from the previous treatments were again grown under field conditions. In the fourth year of experiments, the treatments comprised T₁ (virus-free garlic seeds under the first field cycle) to T₇ (garlic-seed in the sixth field cycle) and C. Two experiments were conducted in the years 1999 and 2000, at two locations and in the years 2001 and 2002 only one experiment per year at one location. The combined analysis of variance for all experiments indicated a significant difference between the treatments for plant height and yield. The bulbs were classified into commercial classes according the Brazilian regulation and the commercial classes 4–7 were 72 %, 60%, 59%, 53% and 35% of the total number of bulbs harvested, from T₁ to T₅, respectively. Virus reinfection at the end of the second field cycle, determined by serology using antisera against the most common viruses of garlic in Brazil reached 83%. Treatments T₁–T₇ yielded 118%, 79%, 57%, 51%, 39%, 33% and 31% higher than the control.     

Adhesion and invasion of Escherichia coli from single and recurrent clinical cases of bovine mastitis in vitro

Seven strains of Escherichia coli, originating from clinical cases of bovine mastitis, and one Salmonella typhimurium control strain were tested for their ability to adhere to, and invade, bovine mammary epithelial cells (MAC-T cells) in vitro. Four of the seven strains were isolated from cows with chronic intramammary infections with recurrent episodes of clinical mastitis and three strains were isolated from single cases of clinical mastitis. Both adhesion and invasion of all strains were dose and time dependent. The four E. coli strains isolated from recurrent cases of clinical mastitis invaded twice as frequently as and three times faster than the strains isolated from single cases of clinical mastitis. By contrast, there was no difference in the amount or speed of adhesion between the two types of strains of E. coli. Adhesion and invasion curves of E. coli resembled a two-step chain reaction, where invasion was the rate-limiting step. Although adhesion and invasion of E. coli has not been demonstrated in vivo yet, the results of the present study may contribute to an understanding of the pathogenesis of chronic intramammary infections caused by E. coli.     

Evaluation of ‘Hamlin’ sweet orange + ‘Montenegrina’ mandarin somatic hybrid for tolerance to Xanthomonas axonopodis pv. citri and Xylella fastidiosa

Asiatic citrus canker (ACC), caused by Xanthomonas axonopodis Starr & Garces pv. citri (Hasse) Vauterin et al., and citrus variegated chlorosis (CVC), caused by Xylella fastidiosa Wells et al., are considered the main diseases affecting sweet orange scion varieties in Brazil. Among commercial varieties, mandarins and tangerines are recognized as tolerant to these pathogens. We report herein the production of ‘Hamlin’ sweet orange (Citrus sinensis L. Osbeck) + ‘Montenegrina’ mandarin (Citrus deliciosa Ten.) allotetraploid somatic hybrid plants by protoplast fusion with improved disease tolerance that could be used as a donor of resistance genes in interploid hybridisation. Somatic hybridisation was confirmed by leaf morphology, flow cytometry and RAPD analyses. The somatic hybrid was propagated by grafting and cultivated in a screenhouse for tolerance assays. For X. axonopodis pv. citri assays, buds were collected from both ‘Hamlin’ sweet orange and the somatic hybrid and grafted onto ‘Cleopatra’ mandarin (Citrus reshni hort. ex Tanaka). As a negative control, buds from ‘Mexerica Tardia’ mandarin (C. deliciosa) were collected and grafted onto ‘Cleopatra’ mandarin. Two-month old plants with at least one young vegetative flush were individually spray-inoculated with a 10⁶ CFU mL⁻¹X. axonopodis pv. citri suspension and incubated in a growth chamber, at 27 °C, under 16-h photoperiod. The somatic hybrid showed a statistically significant reduction in susceptibility to ACC 30 days after inoculation. Compared to ‘Hamlin’ sweet orange, disease severity was reduced by 70%, with similar tolerance to that of the mandarin negative control. For X. fastidiosa assays, buds were collected from the somatic hybrid and its parental plants and grafted onto ‘Rangpur’ lime (Citrus limonia Osbeck). The developed plants were needle-inoculated with a X. fastidiosa suspension (8.7 × 10¹⁰ CFU mL⁻¹) into the new growth flush stem. Bacterial population was quantified both at 4 (at the inoculation point) and 8 months (50 cm above the inoculation point) after inoculation. The first evaluation detected X. fastidiosa in 63% of ‘Hamlin’ sweet orange and ‘Hamlin’ + ‘Montenegrina’ mandarin samples. In the second evaluation, X. fastidiosa was detected in 47.4% of ‘Hamlin’ sweet orange and 10.5% of ‘Hamlin’ + ‘Montenegrina’ somatic hybrid samples, suggesting that bacterial movement was restricted in the somatic hybrid. X. fastidiosa was not detected in both evaluations in samples collected from leaves of ‘Montenegrina’ mandarin. These results indicate that the ‘Hamlin’ sweet orange + ‘Montenegrina’ mandarin somatic hybrid has potential for improved disease tolerance that should enhance its value regarding future use in citrus breeding programs.