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Assam Agricultural University, Jorhat

Assam Agricultural University is the first institution of its kind in the whole of North-Eastern Region of India. The main goal of this institution is to produce globally competitive human resources in farm sectorand to carry out research in both conventional and frontier areas for production optimization as well as to disseminate the generated technologies as public good for benefitting the food growers/produces and traders involved in the sector while emphasizing on sustainability, equity and overall food security at household level. Genesis of AAU - The embryo of the agricultural research in the state of Assam was formed as early as 1897 with the establishment of the Upper Shillong Experimental Farm (now in Meghalaya) just after about a decade of creation of the agricultural department in 1882. However, the seeds of agricultural research in today’s Assam were sown in the dawn of the twentieth century with the establishment of two Rice Experimental Stations, one at Karimganj in Barak valley in 1913 and the other at Titabor in Brahmaputra valley in 1923. Subsequent to these research stations, a number of research stations were established to conduct research on important crops, more specifically, jute, pulses, oilseeds etc. The Assam Agricultural University was established on April 1, 1969 under The Assam Agricultural University Act, 1968’ with the mandate of imparting farm education, conduct research in agriculture and allied sciences and to effectively disseminate technologies so generated. Before establishment of the University, there were altogether 17 research schemes/projects in the state under the Department of Agriculture. By July 1973, all the research projects and 10 experimental farms were transferred by the Government of Assam to the AAU which already inherited the College of Agriculture and its farm at Barbheta, Jorhat and College of Veterinary Sciences at Khanapara, Guwahati. Subsequently, College of Community Science at Jorhat (1969), College of Fisheries at Raha (1988), Biswanath College of Agriculture at Biswanath Chariali (1988) and Lakhimpur College of Veterinary Science at Joyhing, North Lakhimpur (1988) were established. Presently, the University has three more colleges under its jurisdiction, viz., Sarat Chandra Singha College of Agriculture, Chapar, College of Horticulture, Nalbari & College of Sericulture, Titabar. Similarly, few more regional research stations at Shillongani, Diphu, Gossaigaon, Lakhimpur; and commodity research stations at Kahikuchi, Buralikson, Tinsukia, Kharua, Burnihat and Mandira were added to generate location and crop specific agricultural production packages.

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20222
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Subject: Agricultural Entomology × End date: 2022 × Start date: 2022 × Type: Thesis ×
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    ThesisItemOpen Access
    Bio-ecological approaches for management of major insect pests in rice ecosystem
    (2022) Baruah, Mayuri; Dutta, Bijon Chandra
    As biotic stress, especially insect pest is one of the most considerable limiting factors of rice productivity, a field study was carried out in the rice field of Regional Agricultural Research Station, Assam Agricultural University, Titabar, Jorhat to investigate the relative abundance of major insect pests as well as the effects of abiotic factors on their damage incidence in seven high yielding varieties, Ranjit, Ranjit Sub-1, Bahadur, Bahadur Sub-1, Gitesh, Swarna Sub-1 and Shraboni in kharif and rabi season during 2018-2020 with an aim to formulate sustainable management strategies against major insect pests in rice. White stem borer (47.49%) was the most predominantly abundant species followed by yellow stem borer (41.97%) among seven major insect pest species including leaf folder, gall midge, caseworm, whorl maggot and gundhi bug observed throughout all the growth stages of rice both in kharif and rabi season. Both the species of stem borer gradually increased and reached peak at reproductive stage due to availability of enough food and then decreased and again increased in the ripening stage during both the season. The relative abundance of white stem borer varied from 38.23 per cent to 47.49 per cent in the seven varieties recorded higher population in rice variety, Shraboni and lower in Gitesh at reproductive stage in rabi season. Rice leaf folder was the most abundant leaf feeder and its population abundance varied from 6.30 per cent to 6.61 per cent in Ranjit Sub -1, Ranjit and Gitesh without significant difference to each other and higher leaf folder population was recorded in Shraboni (9.89%) followed by Bahadur (9.67%), Bahadur Sub-1 (9.61%) and Swarna Sub-1 (8.47%) at vegetative stage which reached peak at reproductive stage during kharif season. The population of caseworm and whorl maggot was higher in vegetative stage and subsequently declined till the reproductive stage in kharif season. No caseworm population was observed during rabi season due to scanty rainfall. Spider was observed as the most prominent predator followed by coccinellid beetle in all the seven varieties during kharif and rabi season. The relative abundance of spider varied from 7.58 per cent to 9.65 per cent recording minimum population in Shraboni and maximum in the mega variety, Ranjit without significant difference with Gitesh and Ranjit Sub-1. Stem borer caused higher damage in comparison to other insect pests in both the season regardless of the varieties recorded higher in reproductive stage in rabi season as compared to that of other growth stages in both the season. Dead heart incidence was 21.71 per cent in the variety Shraboni that was higher than that of 6 Bahadur (20.76%) and Bahadur Sub-1 (20.83%) without significance difference, but it was significantly differed with stem borer incidence of other varieties being lower in Gitesh (7.45%) at reproductive stage during kharif season. The stem borer incidence was higher in rabi season as compared to kharif season in all the varieties and higher stem borer incidence was recorded in the variety Shraboni (22.43%) followed by Bahadur (21.56%) and Bahadur Sub-1 (21.39%) and lower stem borer incidence (10.39%) was observed in the variety Gitesh without significant difference in the varieties, Ranjit (11.56%) and Ranjit Sub-1 (11.37%) at reproductive stage in rabi season. The study on the effects of weather variables on insect pest incidence revealed that maximum temperature and morning relative humidity were the major weather variables that influenced the damage incidence of the rice insect pests during kharif season. Likewise, maximum temperature, morning relative humidity and bright sunshine hour greatly influenced almost all the major insect pest incidence in rice during rabi season. Since stem borer was found to be the most dominant insect pest throughout all the growth stages of rice both in kharif and rabi season, the biochemical profile was estimated in healthy and infested leaves, stems and seeds in the seven rice varieties against stem borer. It was revealed that total soluble sugar, reducing and non reducing sugar, soluble protein, crude protein and free amino acid contents increased in stem borer infested leaves, stems and seeds than those of healthy ones in all the seven varieties. The increase in sugars, proteins and free amino acid content was more pronounced at 60 DAT in healthy and borer infested leaves and stems and also in healthy and borer infested seeds, but it increased without significant difference between healthy and borer infested leaves and stems both at 30 DAT and 90 DAT in all the seven varieties. The total sugar content in healthy leaves was 15.57 mg /g to 19.73 mg /g which increased significantly from 20.46 mg /g to 26.95 mg/g in damaged leaves at 60 DAT as the increase was higher in Shraboni that was more damaged by stem borer and minimum in Gitesh with lower stem borer incidence. The phenol content in healthy stem increased significantly in infested stems of Ranjit Sub-1(1.54 to 2.13 mg/g), Ranjit (1.51 to 2.10 mg/g) , Gitesh (1.46 to 2.14 mg/g) and Swarna Sub-1 (1.08 to 1.43 mg/g) at 60 DAT after borer damage, but the phenol content increased without significant difference between healthy and infested stems in Shraboni (0.80 to 0.97 mg/g), Bahadur Sub-1(1.02 to 1.34 mg/g) and Bahadur (1.01 to 1.32 mg/g) with higher stem borer incidence. As all the biochemical components except phenol and tannin content increased in the varieties of higher stem borer incidence namely, Shraboni, Bahadur and 7 Bahadur Sub-1, but phenol and tannin content increased in the varieties of lower stem borer incidence, viz., Gitesh, Ranjit, Ranjit Sub-1 and Swarna Sub-1. Higher sugar and protein content with lower phenol and tannin content imparted resistance to the rice varieties viz., Gitesh, Ranjit and Ranjit Sub-1 against stem borer. The non- chemical approach using Beauveria bassiana, Pseudomonas florescence and neem products to manage stem borer in three better performed varieties viz., Ranjit, Ranjit Sub-1 and Gitesh revealed that dead heart incidence was 15.43 per cent, 16.68 per cent and 15.84 per cent respectively without significant difference before one day of treatment in non chemical, chemical and farmers‟ practice respectively at 45 DAT. The dead heart incidence drastically reduced both in chemical (6.19%) and organic treatment (7.23%) without significant difference at 65 DAT in Ranjit. The recorded grain yield was 5.13 t/ha in chemical treatment that was at par with 4.45 t/ha in non chemical treatment. The use of these biopesticides was found to be safer to the natural enemies as the spider and coccinellid beetle population in organic treatment (10.59 and 9.49 number/hill) was at par with farmers‟ practice (12.83 and 11.67 number/hill) respectively. Due to cryptic behavior and nocturnal habit, stem borer is very difficult to manage, therefore the present study will surely help in breeding program to develop a stem borer resistant rice variety and to predict the emergence of stem borer for preparedness at the earliest possible time and to manage the stem borer using non chemical products as a better alternative to replace the irrational use of synthetic chemicals for human safety and environmental protection.
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    ThesisItemOpen Access
    POPULATION DYNAMICS AND CROP LOSS ASSESSMENT OF MAJOR INSECT PESTS OF CUCUMBER (Cucumis sativus)
    (2022) Ganesh, Balaga Mohan; Saikia, D.K.
    Cucumber (Cucumis sativus L.2n = 14) is one of the widely cultivated summer vegetable crops from the gourd family of Cucurbitaceae which is native to India. The climatic conditions of northeast India especially Assam are highly conducive for reproduction of insects, and this region has been considered to be a biodiversity hotspot. Moreover, this region has huge potential for the production of vegetable crops especially cucurbits, but insect pests like fruit flies, pumpkin beetle and sucking pests are major limiting factors for successful cultivation of cucurbits like cucumber etc. Therefore, understanding population fluctuation in the field in relation to losses caused by insect pests are a function of their population dynamics which needs to be thoroughly studied. In view of above factors, an investigation on “Population Dynamics and Crop Loss Assessment of Major Insect Pests of Cucumber (Cucumis sativus)” was carried out at Horticultural Farm and RNA laboratory of Agricultural Biotechnology, Assam Agricultural University, Jorhat. The results showed that during 2019 -2021 summer season, the red pumpkin beetle first appeared on 24th April 2019 and 7th May 2020 with initial population of 4.51 and 2.23 beetles per plant, respectively. However, maximum beetle populations were recorded on 8thMay 2019 and 3rd July 2020 with 6.15 and 6.52 beetles per plant, respectively. Similarly, during 2019-2021, the fruit infestation by fruit fly was recorded first time on 13th June, 2019 and 26th June ,2020 with per cent fruit infestation of 10.24 per cent and 10.75 per cent, respectively. However, highest level of fruit infestation by fruit fly was observed on 25th July, 2019 and 8th August 2020 with 46.86 and 41.3 per cent fruit infestation, respectively. The data on relative abundance of different insects of cucumber during 2019-2021 revealed that the relative abundance of fruit fly species, Bactrocera dorsalis (62.27%) was the highest followed by B. tau (15.68%), B. cucurbitae (10.73%), Dacus longicornis (2.47%), Coccinella transversalis (2.45%), Aulacophora foveicollis (2.20%), Micrapsis discolor (1.56%), A. frontalis (1.16%), and Coccinella septumapunctata (1.08%). During 2019 and 2020, the Simpson-Index diversity showed highest value for fruit fly (0.97 and 0.94) followed by predacious coccinellid beetles (0.67 and 0.71) and red pumpkin beetle (0.55 and 0.64), respectively. Whereas, Shannon-Wiener index diversity (H’) during 2019 and 2020 observed highest in fruit fly (1.65 and 1.85) followed by predacious coccinellid beetles (1.15 and 1.05) and pumpkin beetle (0.68 and 0.85), respectively. The results of yield loss studies during 2019-2020 revealed that the per cent fruit infestation was highest in untreated control plot (30.73%) compared to treated plot (26.8%) with fruit yield of 1223.91 kg/ha and 2311.83 kg/ha, respectively. The yield loss in untreated plot was recorded as 1087.91 kg/ha with 47.05 per cent avoidable loss in yield. Whereas, per cent yield increase over control during 2019-2021 (summer season) was observed as 88.88 per cent. However, economic injury level (EIL) of fruit fly with respect to cucumber was determined as 15.27 and 10.40 per cent with per cent fruit loss of 0.743 and 0.745 during 2019 and 2020, respectively. The optimal phylogenetic tree of 10 fruit fly specimens collected from different locations grouped into two clusters (Cluster A and Cluster B) of two specimens out groups namely B. rubigina and D. longicornis with branch length of 0.0724. In cluster-A, highest genetic distance of 0.047 was recorded between B. rubigina and B. dorsalis. Similarly, in cluster-B the highest genetic distance of 0.0682 was recorded between D. longicornis, B.tau and B.cucurbitae collected from different locations.