Diversity of whitefly species and their vector status in vegetable ecosystem

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dc.contributor.advisorSaikia, Dilip Kumar
dc.contributor.authorGayon, Junmoni
dc.date.accessioned2023-10-20T16:01:42Z
dc.date.available2023-10-20T16:01:42Z
dc.date.issued2021
dc.description.abstractBemisia tabaci (Hemiptera : Aleurodidae) is one of the limiting factors of vegetable crop production system across the world. B. tabaci consist of 24 morphologically indistinguishable species and also plays an important role in transmission of more than 111 plant viruses. In the present investigation, survey was conducted to screen and collect B. tabaci adult and immature stages from 6 different locations covering 3 agro- ecological zone of Assam during 2019 and 2020. Altogether 10 samples were collected from 3 different agroclimatic zones, which were brought to the Biocontrol Laboratory, Department of Entomology, Assam Agricultural University, Jorhat for molecular and morphological analysis. Both the laboratory and grow-out experiments to investigate the vector status were conducted, during 2019-20. The molecular study of the B. tabaci samples collected from different agro-climatic zones was conducted at Department of Plant Pathology, AAU, Jorhat during the year 2020. The samples of B. tabaci were examined for 11 numbers of morphometric characteristics in the case of female, while 10 characters in male. The result on morphometric study revealed that the females were bigger in size than of males. The sample UBZ2 collected from Pulibor, Jorhat showed outgrows in terms of measurement than that of rests. The cluster analysis divided the B. tabaci samples into 2 numbers of clusters on the basis of location and morphometric traits. Cluster 1 comprises the samples NBZ1, NBZ2, CBZ1 and CBZ2; while cluster 2 comprises UBZ1 and UBZ2 sample. The principal component analysis of adult B. tabaci revealed that the morphometrical characters of male and female could be divided into 6 principal component and principal component 1 (PC1) accounts for maximum variability of data. The molecular characterization of B. tabaci collected from different agro-climatic zones using primer based PCR method proves the presence of two different genetic groups. During the experimentation, the mtCOI segment of DNA was amplified at 754bp and 816bp position to determine the genetic variation in B. tabaci. The phylogenetic analysis revealed that the collected B. tabaci samples could be grouped into Asia-II 1 and Asia-II 5; where sample CBZ2 belong to Asia-II 1 and others viz., NBZ1, NBZ2, CBZ1, CBZ2 and UBZ1 belong to Asia-II 5. Phylogenetic tree was constructed using Bayesian method and compared the sequence similarity with the sequence available in the NCBI and found 99-96% similarity. The study on seasonal abundance of B. tabaci was conducted in chilli during 2019 and 2020, which revealed that the population of B. tabaci starts appearing on chilli plants from first standard meteorological week (SMW) (i.e. 1st week of January’2019) with a population density of 1.75±0.15 insects /leaf during 2019. The population gives a major peak at 41st SMW (i.e. 2nd week of October) with a number as high as 90 adults per leaf. In the year 2020, the population of B. tabaci started to increase from 4th SMW with a population of 8 insects/leaf and reached the peak of 72 adults/leaf during 41st SMW at a maximum temperature of 32.9oC, minimum temperature of 24.3oC, morning humidity of 96%, evening humidity of 70% and rainfall 10%. The correlation study revealed that none of the abiotic factors except morning relative humidity significantly correlated with the whitefly population during both the year 2019 and in 2020. The study on the biology of B. tabaci on chilli and brinjal plant shows variability in duration accross different developmental stages. The duration of egg, I instar, II instar, III instar and IV instar was 4.20±0.75-10.20±1.17, 1.60±0.49- 5.20±0.75, 3.20±0.40- 5.20±0.75, 3.00±0.63- 5.60±0.49 and 4.80±0.75-7.00±0.00 days, respectively in chilli; while it was recorded to be 3.00±0.00-9.20±0.40, 1.20±0.40-7.00±0.63, 2.40±0.49-5.40±0.49, 2.60±0.49-5.80±0.40 and 4.00±0.63-6.80±0.40 days in brinjal, respectively. The longevity range of adult female and male in chilli was 2.80±0.75-14.00±0.89 and 1.60±0.49-12.40±0.49 days, respectively; while 4.40±0.49-16.40±0.49 and 2.20±0.40-13.80±0.75 days, respectively in brinjal. Moreover, a total of 10 different natural enemies were also recorded to attack different developmental stages of B. tabaci during the course of inve`stigation from Jorhat district of Assam. The study on transmission status of begomovirus revealed that the B. tabaci can acquire the disease with 1 hr feeding on infected plants with 100% of disease acquisition within 24 hrs. In an inoculation study conducted on chilli plants revealed that an inoculation access period of 1 hr was sufficient to produce disease symptoms in 4 numbers of plants out of total nine with 44.44% disease occurrence. The rate of transmission and number of infected plants was found increases with increase in inoculation time and 100% infection and transmission was found reached at 24 hrs of inoculation feeding period.
dc.identifier.urihttps://krishikosh.egranth.ac.in/handle/1/5810199582
dc.language.isoEnglish
dc.publisherAAU, Jorhat
dc.subEntomology
dc.themeDiversity of whitefly species and their vector status in vegetable ecosystem
dc.these.typePh.D
dc.titleDiversity of whitefly species and their vector status in vegetable ecosystem
dc.typeThesis
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