Browsing by Author "Ramkumar, Govindaraju"

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    Characterization and Evaluation of Metarhizium spp. (Metsch.) Sorokin Isolates for Their Temperature Tolerance
    (MDPI, 2022) Velavan, Viswakethu; Dhanapal, Rajendran; Ramkumar, Govindaraju; Karthi, Sengodan; Senthil-Nathan, Sengottayan; Ndomba, Osmund A.; Kweka, Eliningaya J.
    A field survey was done in teak (Tectona grandis F.) forests in South India to explore the entomopathogenic effect of Metarhizium anisopliae (Ascomycota: Sordariomycetes) against teak defo-liator, Hyblaea puera (Lepidoptera: Hyblaeidae). About 300 soils and infected insect samples were collected during the survey and thirty-six fungal isolates were isolated from soil and insect samples and characterized. The fungi were cultured on PDAY with dodine and antibiotics. Generally, the EPF culture was incubated at 27?C in darkness for 15 days. Virulence of the Entomopathogenic Fungi (EPF) ability to germinate under cold and heat temperatures was assessed in a culture impreg-nated with conidia. In the experiment, it was found that for the first time Metarhizium quizhouense, Metarhizium robertsii, and Metarhizium majus species caused significantly higher mortality to hosts. These isolates of M. anisopliae, M. robertsii, M. majus, and M. quizhouense were all considered to be effective virulent and environmentally adaptive. The Metarhizium isolates were recommended as effective bio-control agents through the field investigation of teak defoliator Hyblaea puera from South India forest. This study paves the way to utilize the indigenous isolates of EPF for the control of teak defoliator and to combat the pests thatare resistant to insecticide. � 2022 by the authors. Licensee MDPI, Basel, Switzerland.
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    Impact assessment of natural variations in different weather factors on the incidence of whitefly, Bemisia tabaci Genn. and yellow vein mosaic disease in Abelmoschus esculentus (L.) Moench
    (Academic Press Inc., 2023) Dhole, Radheshyam Ramakrishna; Singh, Rajendra Nath; Dhanapal, Rajendran; Singla, Saurav; Ramkumar, Govindaraju; Muthuusamy, Ranganathan; Salmen, Saleh H.; Alharbi, Sulaiman Ali; Narayanan, Mathiyazhagan; Karuppusamy, Indira
    Bemisia tabaci Gennadius, also renowned as the silver leaf whitefly, is among the most damaging polyphagous insect pests in many commercially important crops and commodities. A set of field experiments were conducted for three consecutive years i.e., 2018�2020, to investigate the role of variations in rainfall, temperature, and relative humidity on the abundance of B. tabaci in okra (Abelmoschus esculentus L. Moench). In the first experiment, the variety Arka Anamika was cultivated twice a year to analyse the incidence of B. tabaci concerning the prevailing weather factors and the overall pooled incidence recorded during the dry and wet season was 1.34 � 0.51 to 20.03 � 1.42 and 2.26 � 1.08 to 18.3 � 1.96, respectively. Similarly, it was observed that the highest number of B. tabaci catch (19.51 � 1.64 whiteflies/3 leaves) was recorded in morning hours between 08:31 to 09:30 a.m. The Yellow Vein Mosaic Disease (YVMD) is a devastating disease of okra caused by begomovirus, for which B. tabaci acts as a vector. In another experiment, screening was conducted to check the relative susceptibility of three different varieties viz., Arka Anamika, Pusa Sawani, and Parbhani Kranti against B. tabaci (incidence) and YVMD ((Percent Disease Incidence (PDI), Disease Severity Index (DSI), and Area Under the Disease Progress Curve (AUDPC)). The recorded data was normalized by standard transformation and subjected to ANOVA for population dynamics and PDI. Pearson's rank correlation matrix and Principal Component Analysis (PCA) have been used to relate the influences of various weather conditions on distribution and abundance. SPSS and R software were used to create the regression model for predicting the population of B. tabaci. Late sown Pusa Sawani evolved as a highly susceptible variety in terms of B. tabaci (24.83 � 6.79 adults/3leaves; mean � SE; N = 10) as well as YVMD i.e., PDI (38.00 � 4.95 infected plants/50plants), DSI (71.6�96.4% at 30 DAS) and AUDPC (mean ?-value = 0.76; R2 = 0.96) while early sown Parbhani Kranti least susceptible to both. However, the variety Arka Anamika was observed as moderately susceptible to B. tabaci and its resultant disease. Moreover, environmental factors were predominantly responsible for regulating the population of insect pests in the field and hence its productivity like rainfall and relative humidity were negative while the temperature was positively correlated with B. tabaci (incidence) and YVMD (AUDPC). The findings are helpful for the farmers to choose need-based IPM strategies than timing-based, which would fit perfectly with the present agro-ecosystems in all ways. � 2023 Elsevier Inc.
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    Mitigation of Abiotic and Biotic Stress Using Plant Growth Regulators in Rice
    (Multidisciplinary Digital Publishing Institute (MDPI), 2023) Ajaykumar, Ramasamy; Murali Krishnasamy, Subramani; Dhanapal, Rajendran; Ramkumar, Govindaraju; Megaladevi, Pachamuthu; Manjubala, Muthusamy; Chandrasekaran, Perumal; Pradeeshkumar, Thangavel; Navinkumar, Chinnaraju; Harishankar, Kanthaswamy
    Split plot design experiments were conducted to assess the performance of growth regulating compounds for mitigating moisture stress and the incidence of Brown Plant Hopper (BPH) in rice. The main plot treatments (4) comprised moisture stress free control (M1), moisture stress during panicle initiation stage alone (M2), moisture stress during flowering stage alone (M3), and moisture stress during both panicle initiation and flowering stages (M4). The sub-plot treatments (5) were foliar application of growth regulating compounds including chlormequat chloride at 200 ppm (S1), mepiquat chloride at 200 ppm (S2), brassinolide at 0.1 ppm (S3), pink pigmented facultative methylotrophs (PPFM) at 1% (S4), and no spray control (S5). The reduced plant growth attributes were registered under moisture stress at both panicle initiation and flowering stages. The spraying of 1% PPFM during the flowering or both at panicle initiation and flowering stages led to better performance than the other treatments. Also, spraying 1% PPFM brought down the population of BPH to a considerable level during both years of experiments. This suggests that spraying 1% PPFM in the post-flowering stage helps to mitigate the ill effect the moisture stress and BPH incidence. � 2023 by the authors.
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    Pretreatment of mosquito larvae with ultraviolet-B and nitropolycyclic aromatic hydrocarbons induces increased sensitivity to permethrin toxicity
    (Elsevier Ltd, 2022) Ramkumar, Govindaraju; Muthusamy, Ranganathan; Narayanan, Mathiyazhagan; Dhanapal, Rajendran; Karthik, Chinnannan; Shivakumar, M.S.; Malathi, Govindhan; Kariyanna, B.
    Nitropolycyclic aromatic hydrocarbons (Nitro-PAH) are highly toxic PHA derivatives. Nitro-PHAs are emitted by carbonaceous materials and PHA post-emission transformation, which causes water and environmental pollution and also exists as carcinogenic and immunotoxic agents. UV light has been shown to cause DNA damage and improves the covalent binding of PAH to DNA significantly. Mosquito breeding grounds are pools of water that can be large open zones or encased ponds with varying levels of sunlight exposure. This research was performed to assess the combined effects of UV-B exposure and Nitro-PAH on the physiological function of Culex quinquefasciatus larvae. To assess the impact of UV-B irradiation and Nitro-PAH exposure on mosquito vectors, parameters were examined: (1) Nitro-PAH availability and its impact on cell fatalities; (2) the detoxifying abilities of cytochrome P450, glutathione-S-transferase, and esterase; (3) the reactions to Reactive Oxygen Species; and (4) The resistance of mosquito larvae to three synthetic pesticides (temephos, imidacloprid, and permethrin). UV-B and Nitro-PAH treatment caused cellular damage and increased major detoxification enzymes such as ? & ?-esterase, cytoP450, CAT, GST, and POX. The levels of oxidative stress, ROS and protein carbonyl content, nitrite, ascorbic acid and thiobarbituric acid were decreased significantly. Toxicology bioassays revealed that UV-B + Nitro-PAH exposure significantly increased larval susceptibility. The current study concludes that prior exposure to Nitro-PAHs and UV-B may make mosquito larvae more vulnerable to chemical insecticides. � 2022 The Authors