Heavy metals and arbuscular mycorrhizal (AM) fungi can alter the yield and chemical composition of volatile oil of sweet basil (<Emphasis Type="Italic">Ocimum basilicum</Emphasis> L.)

The effects of increasing levels of metals (10 and 20 mg of Cr kg^-1 and 25 and 50 mg of Cd, Pb, and Ni kg^-1 soil) and arbuscular mycorrhizal (AM) fungi Glomus intraradices on the yield, chemical composition of volatile oil, and metal accumulation in sweet basil (Ocimum basilicum L.) were investigated in a pot experiment. The shoot yield, content of essential oil, and root yield of sweet basil were increased by the application of low dose of Cd, Pb, and Ni as compared to control. The application of high level of metals had deleterious effect on the yield. In soil with low dose of metal applied, AM fungi inoculation significantly enhanced the metal concentration in shoots and had adverse effect on the yield, whereas in soil with high dose of metal applied, AM fungal inoculation reduced the metal concentration in shoot and had beneficial effect on the yield. The content of linalool in basil oil was decreased and that of methyl chavicol was increased by the application of Cr, Cd, and Pb in soil as compared to control. Similarly, the level of linalool and methyl chavicol was decreased and that of methyl eugenol was increased by the application of Ni as compared to control. However, AM fungal inoculation led to maintain the content of linalool, methyl chavicol, and methyl eugenol in volatile oil, which were either increased or decreased by the application of metals. We conclude that the AM–sweet basil symbiosis could be used as a novel approach to enhance the yield and maintain the quality of volatile oil of sweet basil under metal-contaminated soils.     

Influence of nitric oxide on in vitro growth, survival, steroidogenesis, and apoptosis of follicle stimulating hormone stimulated buffalo (Bubalus bubalis) preantral follicles

Effect of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on in vitro survival, growth, steroidogenesis, and apoptosis of buffalo preantral follicles (PFs) was investigated. PFs (200~250 µm) were isolated by micro-dissection and cultured in 0 (control), 10^-3, 10^-5, 10^-7, and 10^-9 M SNP. To examine the reversible effect of SNP, PFs were cultured with 10^-5 M SNP + 1 mM N^ω-nitro-L-arginine methyl ester (L-NAME) or 1.0 µg hemoglobin (Hb). The results showed that greater concentrations of SNP (10^-3, 10^-5, 10^-7 M) inhibited (p < 0.05) FSH-induced survival, growth, antrum formation, estradiol production, and oocyte apoptosis in a dose-dependent manner. However, a lower dose of SNP (10^-9 M) significantly stimulated (p < 0.05) the survival, growth, antrum formation, follicular oocyte maturation, and stimulated progesterone secretion compared to the control. A combination of SNP + L-NAME promoted the inhibitor effect of SNP while a SNP + Hb combination reversed this effect. Nitrate and nitrite concentrations in the culture medium increased (p < 0.05) in a dose-dependent manner according to SNP concentration in the culture medium. At higher concentrations, SNP had a cytotoxic effect leading to follicular oocyte apoptosis whereas lower concentrations have stimulatory effects. In conclusion, NO exerts a dual effect on its development of buffalo PFs depending on the concentration in the culture medium.     

Involvement of proline in response of chickpea (Cicer arietinum L.) to chilling stress at reproductive stage

Chickpea is sensitive to chilling stress, especially at its reproductive stage and experiences abortion of flowers and poor pod set at temperatures below 10 °C. The metabolic controls governing chilling-sensitivity in chickpea, particularly involving proline are not known. Hence, in the present study we explored the role of proline in this regard. A set of chickpea plants (cv. GPF2) growing under warm conditions of the glass house (temperature – 28/14 °C as average maximum and minimum till early flowering stage) was exposed to low temperature conditions of the field (8.3–9.6/2.8–5.3 °C; average maximum and minimum temperature, respectively) during the onset of reproductive phase while another set of plants continued to grow under warm conditions. In case of chilling-stressed plants, one set of the plants was treated with 10 μM proline while the other set not treated with proline served as control under low temperature conditions. In untreated chilling-stressed plants, the endogenous proline increased to 230 μmol g⁻¹ dry weight (DW) on 4th day of stress and decreased thereafter to reach 28 μmol on 7th day. In plants treated with 10 μM proline, its endogenous content reached 310 μmol g⁻¹ DW on 4th day and stayed significantly higher than untreated chilling-stressed plants. The proline-treated plants showed significant improvement in retention of flowers and pods leading to better seed yield compared to the untreated ones. The proline-applied plants also had greater pollen viability, pollen germination, pollen tube growth and ovule viability. The stress injury measured as oxidative stress, electrolyte leakage, loss of chlorophyll and decrease in leaf water content was mitigated significantly in proline-treated plants. Additionally, proline application increased the level of sucrose and trehalose (cryoprotectants) in chilling-stressed plants. The studies revealed that proline application was significantly effective in reducing the impact of chilling injury on reproductive growth in chickpea.     

H2O2 degradation is suppressed in kumquat leaves infected with Xanthomonas axonopodis pv. citri

We found in a previous study that after leaves of kumquat [Fortunella margarita (Lour.) Swingle] cv ‘Nagami’ were inoculated with Xanthomonas axonopodis pv. citri (Xac), total superoxide dismutase activity (SOD) increased to promote higher H₂O₂ concentrations that coincided with a 4-fold decline in Xac populations ( Kumar et al., 2011a). The objective of the current study was to determine how activities and isoforms of important enzymes that catabolize H₂O₂, specifically catalase (CAT), ascorbate peroxidase (APOD), and the Class III peroxidases (POD) that are located in the apoplast, change in infected kumquat leaves to affect concentration and compartmentalization of H₂O₂. DAB (3,3-diaminobenzidine) staining of the Xac-infected leaves confirmed higher overall concentration of H₂O₂ as in our earlier study. One day after inoculation (dai), APOD activity declined below the controls and declines steadily up to 10 dai when the experiment was terminated. CAT activity was similar to the controls until 4 dai then declined rapidly to about 60% the activity of the controls by 6 dai, after which it remained fairly constant until 10 dai. There were 4 CAT isoforms in control leaves and 5 isoforms in infected leaves. The CAT-1 isoform band was much smaller in infected plants than the control at all sampling times. The CAT-3 isoform band disappeared at 10 dai. The CAT-5 isoform band, which was not observed in control leaves, appeared only at 4 dai in infected leaves. POD activity of infected leaves increased above the controls starting 1 dai and reached a maximum of about 3-fold higher than the controls 8 dai after which it declined. Two POD isoforms were detected in control and infected plants. This study demonstrated that the higher accumulation of H₂O₂ in kumquat leaves infected with Xac was promoted during pathogenesis first by the suppression of APOD activity and later by suppression of CAT activity. We propose that the higher SOD and lower APOD and CAT activities in the symplast contributed H₂O₂ substrate for the higher POD activity in the apoplast, which is known to be involved in plant defense against pathogens.     

Screening of AM fungi and Azotobacter chroococcum under natural,solarization, chemical sterilization and moisture conservation practices for commercial mango nursery production in north-west Himalayas

The present study investigates the performance of mango seedlings screened with indigenous arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum strains under solarized, chemical sterilized and natural soil conditions. Two isolates each of AM fungi namely, Glomus fasciculatum (Thaxter sensu Gerdemann) and Glomus mosseae (Nicol. & Gerd.), and two strains of A. chroococcum viz., A. chroococcum strain-I (AZ1) and A. chroococcum strain-II (AZ2) were inoculated at nursery stage under four different moisture conservation practices viz., black polyethylene mulch and organic mulches (grass mulch, cover crops, green manure) and clean cultivation. The observations on microbial population, root colonization, growth parameters and leaf nutrient content of the seedlings were recorded. Mango seedling's inoculated with G. fasciculatum and AZ1 had increased seedling's height, diameter, leaf area and total root length, microbial consortium of the rhizosphere soil and leaf N, P, K and Zn content in plots where solarization and black polyethylene mulching was used. The study revealed that the inoculation of mango stones and the saplings with G. fasciculatum and AZ1 under solarized black polyethylene mulched practice may be considered the best practice for raising mango nursery and maintaining soil health under rain-fed conditions of mid-hills of north-west Himalayas.     

H2O2 metabolism during sweet orange (Citrus sinensis L. Osb.) ‘Hamlin’ Xanthomonas axonopodis pv. citri interaction

Sweet orange (Citrus sinensis L. Osb.) ‘Hamlin’ is a canker (Xanthomonas axonopodis pv. citri: Xac) susceptible citrus genotype grown commercially worldwide. Canker causes severe economic losses and restricts the marketability of crop for export. Little is known about the role of oxidative stress in canker development. In the present investigation, sweet orange ‘Hamlin’ leaves were artificially inoculated with Xac to determine the impact of Xac infection on hydrogen peroxide (H₂O₂) metabolism. Characteristic symptoms following artificial inoculation were water soaking of the infiltrated zone between 2 and 8 days after inoculation (dai); raised epidermis accompanying tiny yellow colored bacterial colonies at 8 dai; and yellowing and necrosis of the infected zone by 12–16 dai. In planta Xac population increased 1000 fold by 14 dai from an initial population of 7.3 × 10⁶ cfu cm⁻² (0 dai). Peak concentrations of H₂O₂ were observed at 24 h and between 8 and 10 dai and coincided with higher activity of total superoxide dismutase (SOD). Lower levels of H₂O₂ in infected leaves were maintained by Xac induced higher activities of catalase (CAT), ascorbate peroxidase (APOD), and guaiacol peroxidase (POD). It appears Xac altered H₂O₂ metabolism in C. sinensis L. Osb. ‘Hamlin’ to enhance survival and growth.     

Effect of Pasteurella haemolytica saline capsular extract on bovine pulmonary endothelial cells.

The purpose of this in vitro study was to determine whether Pasteurella haemolytica capsular extract (CE) damages bovine pulmonary endothelial cells (EC) directly or through neutrophil-mediated mechanisms. Chromium 51-labeled EC were treated with the following variables: CE (1, 10, and 100 ng of protein/ml), CE and bovine neutrophils (10(6) cells/well), and CE and polymyxin B (500 U/ml). Although only minimal damage to EC occurred by 5 hours after treatment, by 22 hours after treatment, the 10-ng and 100-ng CE dose produced severe damage to EC, as indicated by 51Cr release, cellular detachment, and loss of monolayer confluency. The component in the CE that was toxic to the EC was lipopolysaccharide, evidenced by effective neutralization of the toxic effect with polymyxin B. Neutrophils inhibited the CE-mediated EC toxicity and were activated, as indicated by shape change and adhesion to EC monolayers. We concluded that the lipopolysaccharide component of CE causes direct damage to EC, which can be attenuated by neutrophils and polymyxin B.     

Estimation of Nitrogen Fixation by the Natural 15N-abundance Technique and Nitrogen Uptake by Pigeonpea Genotypes of Different Maturity Groups grown in an Inceptisol1

The modulation, nitrogen fixation and nitrogen uptake of four pigeonpea genotypes belonging to extra short duration, short duration and long duration maturity groups grown on an Inceptisol were studied to examine why, despite the poor nodulation of pigeonpea in this soil, it still produces greater yields, than in Alfisols and Vertisols. The percentage nitrogen derived from the atmosphere (%Ndfa) was estimated by ¹⁵N natural abundance and N-difference methods using a long duration sorghum as the non-fixing reference crop. In general, nodulation of pigeonpea in the Inceptisol was much lower than that reported in Alfisols and Vertisols. The above-ground dry matter ringed from 3.1 to 17.1 t ha^?1 while the N uptake ranged from 62.3 to 215 kg ha^?1 The fallen plant parrs of pigeonpea genotypes ranged from 1.4 to 4.9 t ha^?1 and their N contents ranged from 25 to 84 kg ha^?1. The estimates of percentage Ndfa obtained by the two methods were different. Those obtained by the ¹⁵N natural abundance appeared more appropriate as the δ¹⁵N of sorghum harvested along with short duration pigeonpea and later when it was mature did not change significantly. The extra short duration pigeonpea genotype ICPL 84023 contained very little N from atmospheric N₂, while the short duration pigeonpea cv. ICPL 151 had 17% Ndfa and the long duration genotypes. ICPL 366 and T7 had up to 36 % Ndfa. It can be concluded that one of the causes of high yields of pigeonpea on Inceptisols compared to Alfisols and Vertisols despite poor nodulation could be the high N supplying capacity of these Inceptisols. Strategies have been suggested as to how pigeonpea genotypes grown in Inceptisols could improve their nodulation and nitrogen fixation and thus better contribute to a sustainable agriculture.     

Control of ticks and tick borne diseases in exotic/cross-bred dairy cattle in India

Tropical Animal Health and Production -