FURTHER STUDIES ON CHLOROTIC MOTTLE DISEASE OF BIDI TOBACCO, NICOTIANA TABACUM L.
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Date
1990
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AAU, Anand
Abstract
Investigations on effect of chlorotic mottle virus in single and mixed infection with tobacco leaf curl virus (TLCV) on growth and chemical constituents of bidi tobacco as well as effect of plant extracts, botanical pesticides, growth filtrate of a fungus and milk on chlorotic mottle virus infection were carried out. Evaluation of tobacco genotypes for chlorotic mottle virus infection was also done. Single infection with chlorotic mottle virus or TLCV had considerably reduced all the growth parameters, viz., leaf number, plant height, leaf length and width, green and cured leaf weight, green and dry stem weight, fresh and dry root weight and green and dry leaf thickness. Effect of chlorotic mottle virus infection on leaf width was comparatively more than TLCV infection. Mixed infection with two viruses exhibited severe impact on all growth parameters as compared to the single infections and the effect was still more severe when compared with healthy plants, thus ultimately resulting in greater reduction in green and cured leaf weight. Alteration in the sequence of inoculation with two viruses did not exert much change in effects on growth parameters barring leaf number and leaf width. Three major chemical constituents, viz., nicotine, reducing sugars and protein nitrogen were affected considerably due to chlorotic mottle virus infection. Nicotine and reducing sugars contents, however, were not altered considerably due to TLCV infection. In general, virus treatments reduced nicotine and protein nitrogen but elevated reducing sugars content. Mixed infection resulted in considerable reduction of nicotine and protein nitrogen and a greater improvement in reducing sugars content over singly infected plants. Effect on nicotine and redoing sugars contents was more with chlorotic mottle virus than with TLCV when the former was inoculated first in the sequence. Leaf extracts of Clerodendron inerme, Parkinsonia aculeata and Ipomea carnea were found to possess potential inhibitors, which completely inhibited chlorotic mottle virus infection on systemic host, Nicotlana tabacum cv GT 5. Ailenthus excelsa, Boerhavia diffusa, Azadirachta indica and Ocimum basilicum were also found to possess fairly strong inhibitory property against the virus infection. When leaf extracts of Catharanthus roseus and Euphorbia prostrata were retested against a lower virus concentration, an increase in antiviral activity was noticed thus suggesting that inhibitors were acting directly on virus before its entry into the plant system. Two botanical pesticides, viz., Nemark and Repelin were found to be poor inhibitors, but exhibited increased inhibitory activity against a lower virus concentration. Growth filtrate of Trichoderma harzianum. a fungal antagonist, was also found to possess some antiviral property. Between whole milk of cow and its dilution 1 : 10, whole milk was found to completely inhibit the virus infection." Evaluation of 134 tobacco (N. tabacum) genotypes revealed that variability existed among them for chlorotic mottle virus infection. Two cultivars, viz., Canellie and Taschlisko seme produced mild symptoms of the disease in response to artificial inoculation of the virus and were considered to be moderately resistant. Out of 7 Nicot iana species tested, only N. glauca remained free from infection and was considered as highly resistant to chlorotic mottle disease.
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Plant Pathology, Agriculture, A Study