Efficacy of Trichoderma asperellum against Ralstonia solanacearum under greenhouse conditions

The rhizosphere soil samples of healthy tomato plants were used to isolate Trichoderma spp and identified based on morphological and molecular characterization as a Trichoderma koningii (T1) T. flavofuscum (T2), T. harzianum (T3), T. asperellum (T4), T. harzianum (T5 & T7), T. koningii (T6), T. asperellum (T8), T. harzianum (T9), T. viride (T10). The isolates screened for antagonistic activity against ten virulent strains of Ralstonia solanacearum (Rs). Two isolates of Trichoderma (T4 and T8) exhibiting high antagonistic activity (24-29mm and 20-27mm respectively) and also studied for several biocontrol mechanisms under greenhouse conditions. These strains were found to be positive to protease, β-1, 3-glucanase, Cellulase, Chitinase, Xylanase, Amylase, Pectinase and lipase activity. Germination percentage increased by 48% and 45% by Trichoderma with pathogen treated seeds and also increased root length, shoot length, fresh weight, dry weight and vigour index. Efficacy of T4 and T8 isolate were evaluated under green house conditions in suppressing disease and promoting tomato plant growth. The disease incidence was significantly reduced by about 50% in tomato plants raised under green house conditions

Electric and magnetic polarizabilities of hexagonal Ln2CuTiO6 (Ln=Y, Dy, Ho, Er and Yb)

We investigated the rare-earth transition metal oxide series, Ln2CuTiO6 (Ln=Y, Dy, Ho, Er and Yb), crystallizing in the hexagonal structure with non-centrosymmetric P63cm space group for possible occurrences of multiferroic properties. Our results show that while these compounds, except Ln=Y, exhibit a low temperature antiferromagnetic transition due to the ordering of the rare-earth moments, the expected ferroelectric transition is frustrated by the large size difference between Cu and Ti at the B-site. Interestingly, this leads these compounds to attain a rare and unique combination of desirable paraelectric properties with high dielectric constants, low losses and weak temperature and frequency dependencies. First-principles calculations establish these exceptional properties result from a combination of two effects. A significant difference in the MO5 polyhedral sizes for M = Cu and M = Ti suppress the expected co-operative tilt pattern of these polyhedra, required for the ferroelectric transition, leading to relatively large values of the dielectric constant for every compound investigated in this series. Additionally, it is shown that the majority contribution to the dielectric constant arises from intermediate-frequency polar vibrational modes, making it relatively stable against any temperature variation. Changes in the temperature stability of the dielectric constant amongst different members of this series are shown to arise from changes in relative contributions from soft polar modes.Comment: Accepted for publication in Phys. Rev. B (21 pages, 2 Table, 8 Figures

Fusarium oxysporum f. sp. lycopersici causal agent of vascular wilt disease of tomato: Biology to diversity– A review

Tomato (Lycopersicon esculentum) is one of the widely grown vegetables worldwide. Fusarium oxysporum f. sp. lycopersici (FOL) is the significant contributory pathogen of tomato vascular wilt. The initial symptoms of the disease appear in the lower leaves gradually, trail by wilting of the plants. It has been reported that FOL penetrates the tomato plant, colonizing and leaving the vascular tissue dark brown, and this discoloration extends to the apex, leading to the plants wilting, collapsing and dying. Therefore, it has been widely accepted that wilting caused by this fungus is the result of a combination of various physiological activities, including the accumulation of fungal mycelia in and around xylem, mycotoxin production, inactivation of host defense, and the production of tyloses; however, wilting symptoms are variable. Therefore, the selection of molecular markers may be a more effective means of screening tomato races. Several studies on the detection of FOL have been carried out and have suggested the potency of the technique for diagnosing FOL. This review focuses on biology and variability of FOL, understanding and presenting a holistic picture of the vascular wilt disease of tomato in relation to disease model, biology, virulence. We conclude that genomic and proteomic approachesare greater tools for identification of informative candidates involved in pathogenicity, which can be considered as one of the approaches in managing the disease

Extracellular Enzymatic Activity of Endophytic Fungal Strains Isolated from Medicinal Plants

Abstract: Endophytic fungi exhibit a complex web of interactions with host plants and have been extensively studied over the last several years as prolific sources of new bioactive natural products. Fungal enzymes are one of them which are used in food, beverages, confectionaries, textiles and leather industries to simplify the processing of raw materials. They are often more stable than enzymes derived from other sources. Enzymes of the endophytes are degraders of the polysaccharides available in the host plants. The use of simpler solid media permits the rapid screening of large populations of fungi for the presence or absence of specific enzymes. Fifty fungal strains, isolated from medicinal plants (Alpinia calcarata, Bixa orellana, Calophyllum inophyllum and Catharanthus roseus) were screened for extracellular enzymes such as amylase, cellulase, laccase, lipase, pectinase and protease on solid media. Sixty four percent of fungi screened for enzymes showed positive fo

Unusual dielectric response in B-site size-disordered hexagonal transition metal oxides

We discover that hexagonal holmium copper titanate (Ho<SUB>2</SUB>CuTiO<SUB>6</SUB>), has a unique and highly desirable combination of high dielectric constant, low losses, very small temperature coefficient, and low frequency dependence. Our first-principles calculations indicate that these exceptional properties result from a size-difference at the Cu/Ti B-site that suppresses the expected ferroelectric transition, combined with the dominance of intermediate-frequency polar vibrational modes in the dielectric response. Our results suggest that the use of such B-site disorder in alloys of hexagonal transition-metal oxides should generally result in similar robust dielectrics

Unusual dielectric response in B-site size-disordered hexagonal transition metal oxides

We discover that hexagonal holmium copper titanate (Ho(2)CuTiO(6)), has a unique and highly desirable combination of high dielectric constant, low losses, very small temperature coefficient, and low frequency dependence. Our first-principles calculations indicate that these exceptional properties result from a size-difference at the Cu/Ti B-site that suppresses the expected ferroelectric transition, combined with the dominance of intermediate-frequency polar vibrational modes in the dielectric response. Our results suggest that the use of such B-site disorder in alloys of hexagonal transition-metal oxides should generally result in similar robust dielectrics. (C) 2010 American Institute of Physics. [doi:10.1063/1.3379293