Association between accumulation of total cyanogens and progression of cassava mosaic disease in cassava (Manihot esculenta Crantz)
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Date
2006
Journal Title
Journal ISSN
Volume Title
Publisher
Uganda J. Agric. Sci
Abstract
Cyanogenic plants, such as cassava, exhibit genetic resistance to diseases and pests, which is associated with a general defence signalling mechanism that responds to stress situations. Cyanogens in cassava vary diversely with cultivar, stress, location, environment and plant age. Factors that induce plant stress often result in increased total cyanogens. Interestingly though, increased total cyanogens often associate with increased resistance to stress. This overlap between plant defence systems and plant stress is not coincidental. The infection of cassava with diseases and pests not only affects yields, but also influences the level of total cyanogens, which are presumed to be a part of the plant defence system. To qualify the extent to which total cyanogens are influenced by cassava mosaic disease (CMD), the effects of CMD status, cultivar resistance and plant vigour on total cyanogens accumulation in cassava at different growth stages of the crop was investigated. A total of 436 cassava plants were studied in the field and greenhouse, representing three different CMD status categories i.e., resistant, moderately susceptible and highly susceptible genotypes. Associated cyanogenic potential (CNp) levels were determined using standard protocols. CMD and CNp were shown to be highly associated (r = 0.90, P d” 0.001 for variety; Pd” 0.003 for CMD) suggesting a role of CNp in the defence mechanism against CMD infection. Notably, lower cyanogen levels occurred in vigorous highly susceptible cassava than in the non-vigorous highly susceptible (most stressed), suggesting a positive correlation between stress level and CNp content. The results of the greenhouse studies matched with those from the field further supporting the observed association between CMD and CNp (P d” 0.001), although, CNp levels were lower than in field trials (by 19.3 fold for roots and 6.3 fold for leaves) possibly due to temperature and nutrition effects. Future studies including understanding of the genetic link between CNp and CMD, interaction between vigour x variety x CMD status, effects of seasonality on CNp accumulation, temperature regimes and nutrition on CNp yield, together may further our knowledge and capacity to control CMD.
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Keywords
Association, progression, total cyanogens, Euphorbiaceae, linamarase, poisoning
Citation
Tumwesigye, S. K., Baguma, Y., Kyamuhangire, W., & Mpango, G. (2006). Association between accumulation of total cyanogens and progression of cassava mosaic disease in cassava (Manihot esculenta Crantz). Uganda J. Agric. Sci, 12(1), 13-21.