Browsing by Author "Taggar, Gaurav Kumar"
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ThesisItem Restricted Determination of Crop Losses, Economic Threshold Level and Management of Spotted Pod Borer, Maruca vitrata (Fabricius) in Pigeonpea(Punjab Agricultural University, Ludhiana, 2017) Mahalle, Rashmi Manohar; Taggar, Gaurav KumarField studies were conducted during kharif 2016 to determine the crop losses, to establish economic threshold level (ETL) and to evaluate the efficacy of some novel insecticides for the management of Maruca vitrata in pigeonpea. Using insect density method for estimating the avoidable yield losses due to M. vitrata in pigeonpea var. PAU 881, highest avoidable yield loss of 79.05 per cent was recorded in the treatment with eight larvae per plant as compared to the uninfested control. The correlation coefficients for the larval infestation level and the pod damage as well as seed damage were significantly positive. However, significantly negative correlation was observed between larval infestation level per plant and seed yield as well as with 100 seed weight. On the basis of chemical protection method, avoidable losses due to M. vitrata in two indeterminate varieties (PAU 881 and AL 201) and two determinate varieties (AL 15 and MN-1) of pigeonpea varied from 39.55-84.68 per cent, with the determinate var. MN-1 registering the highest (84.68%) avoidable loss and the lowest (39.55%) in the indeterminate var. PAU 881. On the basis of regression analysis and gain threshold, the EIL and ETL were computed to be 5.58 and 4.19 webs per plant, respectively. Among the different novel insecticides evaluated for their bio-efficacy against M. vitrata in pigeonpea, the treatment comprising chlorantraniliprole 18.5 SC @ 30 g a.i ha-1 was found to be significantly superior over all other treatments as well as untreated control. Results of the study revealed that significantly lowest pod damage (7.22%), highest seed yield (1278 kg ha-1) and maximum net monetary returns over control (Rs. 22,020 ha-1) were obtained in the treatment chlorantraniliprole 18.5 SC @ 30 g a.i ha-1. The next best treatments were indoxacarb 14.5 SC @ 73 g a.i ha-1 and flubendamide 480 SC @ 48 g a.i ha-1. Studies also revealed that all the insecticidal treatments were relatively safer to the natural enemies at their respective dosage.ThesisItem Restricted Development of screening technique and basis of resistance in black gram (Vigna mungo (L.) Hepper) against whitefly, Bemisia tabaci (Gennadius)(Punjab Agricultural University, Ludhiana, 2011) Taggar, Gaurav KumarThe studies on development of screening technique and basis of resistance in black gram against whitefly, B. tabaci were conducted during kharif 2009 and 2010. The leaf injury symptoms due to whitefly were categorized into five grades (I-V). Experiments conducted on standardization of screening technique against B. tabaci confirmed that black gram genotypes can be effectively screened at 3rd trifoliate leaf stage using 100 whitefly adults per plant under screen-house. Evaluation of black gram genotypes against B. tabaci in multiple-choice test on the basis of whitefly resistance index (WRI) revealed that genotypes KU 99-20 and NDU 5-7 were moderately resistant (WRI=1.50) and also recorded significantly lowest whitefly population (eggs, nymphs and adults) as compared to other genotypes. The genotypes IPU 02-043, KU 7-602, KU 7-605, KU 7-618 and Mash 1-1 were categorized as susceptible (WRI ranging from of 2.59 to 3.05) and genotypes KU 7-504 and KU 7-505 as highly susceptible (WRI ranging from 3.66 to 3.70) to B. tabaci. The whitefly adult population among the three canopies (upper, middle and lower) showed non-significant differences. Leaf area, lamina thickness and trichome length were significantly and positively correlated with whitefly eggs, nymphs, adults and WRI, whereas trichome density and angle were negatively correlated. Total phenols, o-dihydroxy phenols, flavonols, peroxidase and catalase were found to be significantly but negatively correlated with whitefly nymphs, adults and WRI. The chlorophyll content indices declined significantly in all the genotypes under whitefly stress conditions, particularly in the lower canopy of the plants. Thus, black gram genotypes with narrow, thin and highly pubescent leaves having short, but erect trichomes and higher total phenol contents should be selected for developing black gram varieties resistant to whitefly.ThesisItem Restricted Induced host plant resistance in pigeonpea against spotted pod borer, Maruca vitrata (Fabricius)(Punjab Agricultural University, 2022) Khokhra, Shivani; Taggar, Gaurav KumarThe studies on “Induced host plant resistance in pigeonpea against spotted pod borer, Maruca vitrata (Fabricius)” were conducted during Kharif 2020 and 2021. Field screening of pigeonpea genotypes revealed that the genotype AL 1747 consistently performed better towards M. vitrata infestation during both years (Kharif 2020 and 2021). The exogenous application of Jasmonic acid (JA) (100 µM) and Salicylic acid (SA) (5.0 mM) on pigeonpea plants triggered the induction of biochemical parameters (enzymes and secondary metabolites) after 12 and 24 h of application, respectively. Pre-treatment with JA (100 µM) followed by infestation with M. vitrata after 12 h elicited a strong defense response in both the resistant (AL 1747) and susceptible (MN 1) genotypes. AL 1747 responded better to the exogenous application of elicitors and M. vitrata than the susceptible genotype MN 1. The induced effect was highest one day after the treatment (in both JA and SA) and showed a declining trend thereafter with no changes in the activities of defensive enzymes and secondary metabolites after 7 days of treatment. Both JA and SA induced an antioxidative response in pigeonpea plants against M. vitrata, which, in turn, affected the insect development, nutritional indices as well as the metabolism of M. vitrata. Imbalance in the digestive enzymes significantly reduced the nutritional indices (AD, ECI, ECD and RGR) of M. vitrata in JA-treated plants. Insect, as a counter-response to plant defense, increased the activities of glutathione-S-transferases (GST) and glucose oxidase (GOX). However, a significant negative correlation was observed between the detoxifying enzyme (GST) and larval weight (r= -0.790**). The GOX activity and larval weight exhibited a non-significant negative correlation with each other post-elicitor application. SA also led to an alteration in the activities of digestive and defense related enzymes in M. vitrata; however, the effect was not as pronounced as JA. An alteration in insect defensive and digestive enzymes and upregulation of plant secondary metabolites by exogenous application of elicitors (either in the pre-/or simultaneous application) indicates that modulation of pigeonpea defense can increase the effectiveness of the host plant to defend against M. vitrata herbivory.