Tobacco (Nicotiana spp.) is an important commercial crop of India occupying about 4 lakh ha (0.23% of the total arable land in the country) and producing around 600 million kg of cured leaf annually. India occupies first place in respect of non-fcv tobacco and 5 place in respect of area under FCV tobacco on global basis. Brown spot is an endemic disease, often becomes epiphytotic under favourable conditions. In India the losses in tobacco due to brown spot ranges from 17-25% under favourable weather condition. Based on studies on brown spot incidence at different locations in Dinhata subdivision it has been observed that disease intensity ranging from 17.72-25.00%. Variability aspect of host pathogen system included isolation of the pathogen from different symptoms, characterization of the isolates in vitro for their growth pattern and degree of virulence in the host. Out of a total 3 isolates isolated from 3 different symptom pattern in the host, the frequency of isolate Aa 3 was higher (62%) while Aa1 was more virulent and aggressive. Based on AUDPC, a total of 175 germplasm accessions of Motihari tobacco were categorized against brown spot under field conditions. Biochemical aspects of disease resistance were studied in relation to OD phenol, phenol, peroxidase, protein and chlorophyll. Predisposing factors of the disease in relation to weather parameters were studied and positive co-relation was found with maximum temperature, maximum relative humidity and rain fall with disease severity. The management of brown spot under field conditions was tried with different chemicals and bio agents. Significant reduction in the disease was achieved by propiconazole followed by mancozeb. Soil application and foliar spray with bio agent consortium was found statistically at par with positive check treated with Propiconazole in terms of disease suppression. Signature of Chairman Signature of the Student Advisory Committee

Variability and management of brown spot disease in motihari tobacco caused by aliernaria alternata ( FRIES) KEISSLER

https://www.tiprpress.com/chmen/ch/reader/create_pdf.aspx?file_no=CHM1068D&flag=1&journal_id=chmen&year_id=2010

Stem blight control of Schizonepeta tenuifolia caused by Phytophthora nicotianae using Trichoderma spp.

Study on pathogenicity differentiations of Alternaria alternata and biocontrol of tobacco brown spot

One isolate of Trichoderma sp was obtained by the method of baiting The antagonistic test of the isolate to strains of Phtophthora nicotiana (pathogen of tobacco black shank) from diseased tobacco stems from different area of Yunnan were carried out by pairing culture on PDA The results showed that this isolate was strong antagonistic to black shank fungus The antagonistic mechanism appeared to be competitive growth and antibiosis The control effect of this isolate applied for tobacco black shank in greenhouse was as high as 976% (10~(6) cfu/mL) When applied in field soil around the tobacco root at 4 g every root, the control effect could arrive at 67%

Li Zhenguo

Papers

Study on pathogenicity differentiations of Alternaria alternata and biocontrol of tobacco brown spot

Study on the Antaganistic Mechanism of Trichoderma sp.for Phytophthora Nicotianae and it's Biocontrol Effection