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ThesisItem Open Access Acaricide resistance and its biochemical and molecular bases in two-spotted spider mite, Tetranychus urticae Koch(Punjab Agricultural University, Ludhiana, 2017) Sharma, Rakesh Kumar; Bhullar, Manmeet BrarTwo-spotted spider mite (TSSM), Tetranychus urticae Koch (Acarina: Tetranychidae), has gained importance in view of their widespread occurrence as a pest on vegetables in Punjab. Studies were conducted to monitor the magnitude of acaricide resistance in T. urticae, against different acaricides viz., propargite, spiromesifen, fenpyroximate and fenazaquin collected from different vegetable growing areas (Amritsar, Hoshiarpur, Malerkotla and Patiala) of Punjab and its mechanism through biochemical and molecular diagnosis. The development of acaricide resistance has been screened in field populations of T. urticae and compared with a laboratory reared susceptible population based on toxicity bioassay using leaf disc dip technique. Patiala population was least susceptible to fenazaquin (RR 24.65) among all tested acaricides while Amritsar population was found to be highly susceptible (RR 6.67) Among all tested acaricides, fenpyroximate (0.00205 – 0.00954 per cent) was found to be the most toxic against all the tested populations except Malerkotla population.Therefore, low to moderate levels of resistance (3.19-24.65 fold) was observed in T. urticae to tested acaricides in Punjab. Biochemical and molecular analysis were done with Fenzaquin selected resistant population that was developed in the laboratory by giving selection pressure with fenazaquin up to 15 generations. Selection with fenazaquin significantly increased the activities of monooxygenases, GST and esterases by 3.21, 1.40 and 1.13-1.27 fold, respectively when compared to susceptible population proving their role in Fenazaquin mediated resistance. Molecular analysis of resistant and susceptible population revealed no changes in genes structure of mtCOI, CYP392A11 and CYP392A12 in the resistant compared to the susceptible population. However, expression profiling of nine different genes associated (CYP392A11, CYP392A12, CYP392A16, CYP392D2, CYP392D3, CYP392D6, CYP392D7, CYP392D8 and CYP392D10p) with METI resistance showed increased mRNA transcripts in CYP392A11, CYP392A12, CYP392D2 and CYP392D10p. The increased MFO activity in the resistant population corresponds to nearly twice fold increase in the expression of CYP392A11 and CYP392A12. The moderate level of resistance observed in the selected population may be attributed to both increased enzyme activity and gene expression. The target site mutation might not have any role in low to moderate level of fenazaquin resistance in mites. Enzyme and mRNA expression has the wide potential to be used as a fast and reliable tool for early detection of resistance against METI acaricides.ThesisItem Open Access Studies On Effect Of Minerals And Hormonal Interventions On Reproductive Performance Of Buffaloes Different Agro-Climatic Zones Of Punjab(Punjab Agricultural University ;Ludhiana, 2003) Sharma, Rakesh Kumar; Gandotra, V. K.