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Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum caused seedling losses in nurseries, as well as severe losses in many crops in Nghe An province, Vietnam, in 2008. Isolates of the fungus were shown to be pathogenic. All 20 cultivars grown in the province in

Occurrence of toxic cyanobacteria and their toxins has been a root of many consequently serious problems to aquatic plants, animals, and human in the world. However, the toxicity of cyanobacterial toxins from Vietnam waters to the germination and growth of plants has not studied yet. In this study, we investigated the effects of microcystins (MC) (at the concentrations of 20 and 200 µg MC L-1) from field water and crude extract of cyanobacterial scum (mainly Microcystis spp.) from the Dau Tieng Reservoir, on the germination and seedling of Brassica juncea and Medicago sativa during 7 days. The results showed that MC inhibited the germination of the exposed seeds from 10 -35% compared to the control. The fresh weight of exposed B. juncea and M. sativa compared to the control was from 44 -89% and from 55 -90%, respectively. Root length of the plants reduced from 12 -73% for B. juncea and from 17 -54% for M. sativa during toxin exposures. Similarly, the decrease of the shoot length, compared to the control, was from 20 -80% for B. juncea and 13 -52% for M. sativa. Therefore, the use of water contaminated with MC for irrigation may negatively influence on the quality and yield of agricultural crops. It could be inferred that there should be an uptake of MC by the exposed seeds and th toxin might be transferred to the next consumers via the food chain.

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