VISWANATH, KRAMANJINEYULU, P2019-05-072019-05-072018http://krishikosh.egranth.ac.in/handle/1/5810102204D5728Groundnut (Arachis hypogaea L.) is the fourth important source of edible oil and third most source of vegetable protein. It is susceptible to losses incited by soil borne pathogens due to the close association of the pods with the soil. Among soil borne diseases of groundnut, pod rot is a complex disease and emerging as a serious disease in different agro-climatic zones of Andhra Pradesh due to change in soil moisture, pH, soil temperature and crop sequence facilitating rapid multiplication of different micro-flora in crop rhizosphere. In the survey on the pod rot incidence in groundnut, the mean pod rot disease incidence in Chittoor district varied from 11.4 to 28.6 per cent while in the Anantapur district, the mean pod rot incidence varied from 8.5 to 30.0 per cent. In the Chittoor district, from the 34 pod rot affected samples collected from the seven mandals, nine isolates of Fusarium spp., five isolates of Rhizoctonia bataticola and seven isolates of Sclerotium rolfsii. Similarly from the Anantapur district, one isolate of Fusarium spp., five isolates of R. bataticola and three isolates of S. rolfsii were isolated from 12 samples. A total of four Trichoderma isolates and four bacterial isolates were isolated from the rhizosphere soil samples. In the evaluation of the efficacy of four isolates of Trichoderma spp, against all the isolates of Fusarium spp, R. bataticola, S. rolfsii, the highest inhibition of 35.8, 67.7 and 57.2 per cent was recorded on TF2, TRb5, TSr5 isolates respectively. Similarly with four isolates of rhizospheric bacteria against all the isolates of Fusarium spp., R. bataticola, S. rolfsii the highest inhibition of 56.6, 64.4, and 69.1 per cent was recorded on TF3, TRb10, TSr2 isolates respectively. Based on the dual culture study results, the potential isolate of Trichoderma sp. (TT4) and TB3 isolate of rhizospheric bacteria along with pathogen isolates which exhibited the lowest mean per cent inhibition viz., TF1 of Fusarium sp., TRb8 of R. bataticola and TSr6 of S. rolfsii were selected for the in vitro as well as in vivo studies. Among the fungicides tested against TF1 isolate of Fusarium sp.; TRb8 isolate of R. bataticola and TSr6 isolate of S. rolfsii, tebuconazole and tebuconazole + trifloxystrobin has shown cent per cent inhibition at all the three concentrations. The effective fungicide tebuconazole, potential isolates of Trichoderma sp (TT4) and rhizospheric bacteria (TB3) identified under in vitro studies were evaluated under in vivo by integrating the respective components in pot culture. In the studies against the three isolates of pathogen viz., Fusarium sp (TF1), R. bataticola (TRb8), S. rolfsii (TSr6), the integrated treatment T6 i.e. seed treatment with tebuconazole @ 1g/kg of seed + soil application of potential fungal and bacterial bio agents + soil application of gypsum at 45 DAS has recorded the lowest pod rot incidence of 11.4, 20.7 and 6.0 per cent respectively. From the present study it can be concluded that the groundnut pod rot disease is complex in nature due to the association of more than one soil borne pathogens for the control of which there is a need for the integration of cultural, biological and chemical methods in disease management.en-USnullThesis