V. B. NargundSuresh Patil2016-07-262016-07-262013http://krishikosh.egranth.ac.in/handle/1/69871In recent years, twister disease of onion has become epidemic in coastal tract and other onion growing districts of Karnataka which caused heavy loss. Survey carried out during kharif and rabi/summer 2011-12 and 2012-13 revealed highest PDI 26.71 in Uttar Kannada district. Typical symptoms of the disease: twisting of leaf, neck with blight as well as dieback (anthracnose), scanty root system with galls and showing fungal growth was noticed. Artificial inoculations of onion seedlings with Colletotrichum gloeosporioides, Fusarium oxysporum, Meloidogyne spp. alone and in combinations expressed twister disease symptoms. Metabolomic changes like increased total sugars and growth hormones (IAA and GA) were seen. A two year pooled correlation analysis of weather parameters on incidence and severity showed that cumulative rainfall contributed more (0.97) to disease development followed by maximum temperature (0.41). Among the different planting dates, least incidence was recorded in 15th January. Molecular identification of fungi by amplification of ITS rDNA region was done, sequenced and confirmed as C. gloeosporioides, C. acutatum, Glomerella acutata, F. oxysporum and Gibberella moniliformis. Sequences were deposited in genbank. Specific amplification of CgInt region at 450 bp for C. gloeosporioides ; for C. acutatum CaInt region at 490 bp and for F. oxysporum at 550-570 bp was obtained. PCR – RFLP with HaeIII resulted in a characteristic pattern of three fragments. In vitro evaluation of fungicides revealed triazolels and combi products were effective in inhibiting growth of both fungal pathogens. Botanicals as consortia of plant extracts (neem, prosopis, clerodendron and Vinca rosea) and bioagent Trichoderma harzianum were also effective. Integrated management of twister disease revealed that, T5 (Adoptive + Nutrient module) recorded least PDI 20.50 and 19.86 with maximum yield of 67.33 t/ha and 39.36 t/ha at Dharwad and Kumta locations respectively.Thesis