Browsing by Author "H.V. Singh"

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Effects of mercuric chloride on akinete germination and sporulation in Pithophora oedogonia (Mont.) Wittrock (Cladophorales, Chlorophyceae)
(1986) B.R. Chaudhary; H.V. Singh
The effect of mercuric chloride on akinete germination and sporulation with respect to time lapse and extent was studied in Pithophora oedogonia (Mont.) Wittrock (Cladophorales, Chlorophyceae). At HgCl2 concentrations from 1.25 to 45 mg/l akinetes showed progressive delay in the initiation and reduction in the extent of germination. HgCl2 concentrations of 60 mg/l and above proved to be completely lethal to the spores as they failed to germinate. The time necessary for the initiation of akinete formation and the percentage sporulation also decreased with an increase in the concentration of HgCl2 from 1.25 to 45 mg/l where spore germination was encountered. Inactivation of enzymes and metabolic inhibition seemed to be the cause of spore lethality. Copyright © 1986 Wiley‐VCH
Influence of certain environmental factors on spore germination and spore differentiation in Pithophora oedogonia
(Springer Netherlands, 1987) B.R. Chaudhary; H.V. Singh
Of the light- and dark-stored spores of Pithophora oedogonia for over a period of one and half years, the latter exhibited complete failure of germination under controlled culture conditions. pH 8, blue light and 1 klx intensity of white light proved to be ideal conditions as they resulted in optimum germination of akinetes. pH 5, green light and 0.25 klx light intensity delayed the initiation of sporulation and also reduced percentage sporulation. All filaments died before sporulation in pH 4. © 1987 Institute of Microbiology, Academy of Sciences of the Czech Republic.
Karyological investigations on the genus oedogonium link (Oedogoniales, chlorophyceae)
(1990) H.V. Singh; B.R. Chaudhary
Six dioecious macrandrous and three monoecious macrandrous taxa of Oedogonium Link were studied cytologically and subjected to karyotypic analyses. Nuclear events conformed to the standard pattern of mitosis met with in typical eukaryotes. The chromosome numbers exhibited by various taxa are Oe. gracilius var. globosum, n = 13; Oe. hindustanense, n = 17; Oe. lemmermannii, n = 19; Oe. hatei, n = 21; Oe. plagiostonum f. minuta, n = 22; Oe. calcareum, n = 32; Oe. intermedium f. tenuis, n = 21; Oe. pseudaureum var. maius, n = 25 and Oe. tropicum, n = 37. These taxa were investigated for the first time and most of the chromosome numbers represented new counts for the genus. A perusal of chromosome number revealed that aneuploidy has played a more efficient role in the speciation and evolution of this genus. Furthermore, clear differences in karyotypes of the taxa with common chromosome numbers indicated positive role of chromosomal rearrangements in speciation of the genus Oedogomum. Lack of identifiable sex chromosomes in macrandrous homothallic taxa and the presence of identical karyotypes- chromosome number and morphology in the male and female strain of macrandrous heterothallic taxa clearly suggested that sex differentiation, in Oedogonium, is controlled by genes rather than specific sex-chromosomes. Thus, the decisive role of genes in the evolution of taxa investigated cannot be ignored. © 1990 Taylor & Francis Group, LLC.
Microbial Interactions in the Rhizosphere Contributing Crop Resilience to Biotic and Abiotic Stresses
(Springer, 2020) Deepti Malviya; Udai B. Singh; Shailendra Singh; Pramod K. Sahu; K. Pandiyan; Abhijeet S. Kashyap; Nazia Manzar; Pawan K. Sharma; H.V. Singh; Jai P. Rai; Sushil K. Sharma
Rhizosphere is a hot spot where specific kinds of diverse microbial communities develop under the influence of exudates from plant roots and in turn modulate growth and development of the plant. Such communities with or without interactions perform an array of functions, including nitrogen fixation, P, Zn, Si and K-solubilization, siderophore production, ammonification, hormones production, ACC deaminase production, ethylene production, anammox, comammox, nitrification, denitrification, antagonisms, induce resistance to plant, C-sequestration, volatile production, secondary metabolites production and many others that are known to modulate soil and plant health contributing to the corresponding responses to various stresses of biotic and abiotic nature. The magnitude of resilience of plant to biotic and abiotic stresses is completely dependent on types of communities and their interactions. With enhanced knowledge and understanding about rhizosphere, researchers are evaluating various approaches to engineer rhizosphere in such way that it enables plant to enhance the productivity and sustain it while maintaining soil health. This chapter highlights detailed account of microbial interactions in the rhizosphere with associated mechanisms that contribute to resilience of plants to stress for better growth and development. © Springer Nature Singapore Pte Ltd. 2020.
Nutritional Control on Sex Differentiation in the Filamentous Green Alga Oedogonium hatei Kam.
(1988) B.R. Chaudhary; H.V. Singh
Effects of various nutrients constituting the Godward and Chu 10 media on oogonial development in Oedogonium hatei, a macrandrous heterothallic alga were studiedWhile Godward medium supported massive vegetative growth, the Chu 10 medium favoured sex differentiation in OhateiOf the various nutrients of the Godward medium tested deficiency of only NO3-N was found inductive for the differentiation of sexContrarily, omission of other nutrients of the Chu 10 medium as well resulted into an increase in the percentage of oogonium which, however, decreased in the medium deficient in K2HPO4Extra addition of all other nutrients except K2HPO4, on the other hand, reduced the percentage of oogoniumThe alga grown in the medium containing 3- to 10-fold Ca(NO3)2 exhibited complete inhibition of sexual differentiation. That the level of NO3-N in the nutrient medium is the most crucial factor in the differentiation of sexual structures, whereas PO4-P has either no or little effects on the process of sex differentiation was concludedBesides, NO3-N and PO4-P seemed to exert opposite effects on oogonial differentiation, for which no explanations can be offered at least for the present. © 1988, VEB Gustav Fischer Verlag Jena. All rights reserved.
Physiological and morphological aspects of Bipolaris sorokiniana conidia surviving on wheat straw
(2002) R. Chand; H.V. Singh; A.K. Joshi; E. Duveffler
Wheat samples showing typical spot blotch symptoms on stems and sheaths were collected from the field after physiological maturity, and were sealed in paper bags and stored in the laboratory at room temperature to study the survival of Bipolaris sorokiniana conidia on wheat straw. The materials were observed at monthly intervals to assess the conidia viability during storage. After 4 months, the frequency of individual conidia already present on wheat straw at the time of sampling was reduced and appeared to be progressively replaced by the formation of round structures consisting of conidia aggregates. After 5 months, distinct, individual conidia were no longer detected, and only 'clumps of conidia' were observed. These dark black aggregates or 'clumps of conidia' measured 157-170 μm in diameter and were grouped into boat-shaped olivaci-ous conidia showing thick wall and measuring 50-82 × 20-30 μm. The germination was unipolar and below 0.5%, suggesting the occurrence of dormancy. In contrast, individual conidium produced on wheat during the growing season were 96-130 ×16-20 μm, slightly curved, hyaline to light pale, and euseptate with a bipolar germination reaching 98-100%. Bipolaris sorokiniana conidia produced on PDA were 55-82 × 20-27 μm, tapered at both ends, dark brown to olivacious, distoseptate, showed up to 1% germination, and were predominantly unipolar. Results of the present study suggest that B. sorokiniana conidia belonged to two different physiological categories corresponding to the pathogen's infection phase and its survival, respectively. The infection phase is characterized by a high germination percentage as opposed to the survival phase harboring apparent dormancy. © The Korean Society of Plant Pathology.
Toxicity of CuSo4 for growth and oogonium formation in Oedogonium hatei
(Springer Netherlands, 1993) H.V. Singh; B.R. Chaudhary
The effect of CuSO4 on the germination and growth of swarmers and subsequent induction of oogonia was studied in Oedogonium hatei Kam. (Oedogoniales, Chlorophyceae). A 0.05 mg/L concentration of the metal compound showed a stimulatory effect on the growth of the alga in comparison to control. Growth was inhibited at above 0.1 mg/L concentrations. The percentage of oogonia formed and the mature oogonia developed linearly decreased with increase in concentrations of CuSO4 employed. Two mg/L CuSO4 proved to be highly toxic to the growth and/or multiplication of zoospores and further development of sexual structures in this alga. The germination of zoospores and the growth of germlings were so markedly affected that induction of oogonia remained- completely inhibited at 2 mg/L CuSO4. A 3 mg/L concentration of CuSO4 proved to be completely lethal to asexual swarmers and no survival of zoospores was encountered in any case. © 1993 Folia Microbiologica.
Trichoderma harzianum-and methyl jasmonate-induced resistance to bipolaris sorokiniana through enhanced phenylpropanoid activities in bread wheat (Triticum aestivum L.)
(Frontiers Media S.A., 2019) Udai B. Singh; Deepti Malviya; Shailendra Singh; Manoj Kumar; Pramod K. Sahu; H.V. Singh; Sunil Kumar; Manish Roy; Mohd. Imran; Jai P. Rai; A.K. Sharma; A.K. Saxena
The aim of the present study was to evaluate the impact of Trichoderma harzianum UBSTH-501-and methyl jasmonate-induced systemic resistance and their integration on the spot blotch pathogen, Bipolaris sorokiniana through enhanced phenylpropanoid activities in bread wheat (Triticum aestivum L.). It was found that the application of MeJA (>100 mg L−1 ) inhibits the germination of B. sorokiniana spores under controlled laboratory conditions. To assess the effect of MeJA (150 mg L−1 ) in combination with the biocontrol agent T. harzianum UBSTH-501 in vivo, a green house experiment was conducted. For this, biocontrol agent T. harzianum UBSTH-501 was applied as seed treatment, whereas MeJA (150 mg L−1 ) was applied 5 days prior to pathogen inoculation. Results indicated that application of MeJA (150 mg L−1 ) did not affect the root colonization of wheat by T. harzianum UBSTH-501 in the rhizosphere. The combined application of T. harzianum UBSTH-501 and MeJA also enhanced indole acetic acid production in the rhizosphere (4.92 µg g−1 of soil) which in turn helps in plant growth and development. Further, the combined application found to enhance the activities of defense related enzymes viz. catalase (5.92 EU min−1 g−1 fresh wt.), ascorbate peroxidase [µmol ascorbate oxidized (mg prot)−1 min−1 ], phenylalanine ammonia lyase (102.25 µmol cinnamic acid h−1 mg−1 fresh wt.) and peroxidase (6.95 Unit mg−1 min−1 fresh wt.) significantly in the plants under treatment which was further confirmed by assessing the transcript level of PAL and peroxidase genes using semi-quantitative PCR approach. The results showed manifold increase in salicylic acid (SA) along with enhanced accumulation of total free phenolics, ferulic acid, caffeic acid, coumaric acid, and chlorogenic acid in the leaves of the plants treated with the biocontrol agent alone or in combination with MeJA. A significant decrease in the disease severity (17.46%) and area under disease progress curve (630.32) were also observed in the treatments with biocontrol agent and MeJA in combination as compared to B. sorokiniana alone treated plant (56.95% and 945.50, respectively). Up-regulation of phenylpropanoid cascades in response to exogenous application of MeJA and the biocontrol agent was observed. It was depicted from the results that PAL is the primary route for lignin production in wheat which reduces cell wall disruption and tissue disintegration and increases suberization and lignification of the plant cell as seen by Scanning Electron microphotographs. These results clearly indicated that exogenous application of MeJA with T. harzianum inducing JA-and/or SA-dependent defense signaling after pathogen challenge may increase the resistance to spot blotch by stimulating enzymatic activities and the accumulation of phenolic compounds in a cooperative manner. This study apparently provides the evidence of biochemical cross-talk and physiological responses in wheat following MeJA and biocontrol agent treatment during the bio-trophic infection. © 2019 Singh, Malviya, Singh, Kumar, Sahu, Singh, Kumar, Roy, Imran, Rai, Sharma and Saxena.
Variability and its probable cause in natural populations of spot blotch pathogen Bipolaris sorokiniana of wheat (T. aestivum L.) in India
(2003) R. Chand; S.P. Pandey; H.V. Singh; Sundeep Kumar; A.K. Joshi
A study was undertaken to find out the extent of variability and the probable cause of its emergence in natural populations of the spot blotch pathogen Bipolaris sorokiniana of wheat. The pathogen was isolated from infected seeds and leaves on PDA and purified by monoconidial isolation. The frequency of nucleus in mycelial cells of isolates was recorded using fluorescent staining. Based on colony morphology, the isolates were grouped into five groups. Cluster analysis confirmed this classification. Maximum frequency (44.63%) of isolates in the natural populations was that of black suppressed type. This group was most aggressive and identified as the epidemic population. Lowest frequency (4.96%) was observed for white isolate which produced very few conidia. The mean radial growth of isolates on 8th day ranged form 4.77 to 8.27 cm. The monoconidial isolates, when inoculated on resistant and susceptible cultivars, showed mean AUDPC range of 176.67-1237.59 and 600.83-2144.21% days, respectively. In the epidemic population, cells with two nuclei displayed highest frequency, while in other groups, cells with three or four nuclei were most frequent. The present study revealed that the variability in Bipolaris sorokiniana was reflected in different combinations of the nuclei.