Role of alcohol dehydrogenase, malate dehydrogenase and malic enzyme in flooding tolerance in Brachiaria species

A pot culture experiment was conducted to assess the role of malate dehydrogenase, alcohol dehydrogenase and malic enzyme in flooding tolerance in Brachiaria species. Ethanol levels were several times more in B. mutica (para-grass, tolerant) roots and leaves in comparison to B. brizantha (intolerant) roots and leaves, respectively, Ethanol concentration did not change during flooding in both the species. ADH activity increased four fold in B. mutica roots during flooding and remained unaffected in B. brizantha. Tolerance to higher concentration of ethanol and higher ADH activity in B. mutica roots during flooding would allow for the maintenance of ethanol fermentation system and result in continued energy production, MDH levels increased seven fold in B. mutica roots and decreased to half in leaves during flooding and remained unchanged in B, brizantha. Malic enzyme showed similar pattern in both the species indicating that ME may not be a limiting factor in determining flooding tolerance in Brachiaria species. Increased ADH and MDH activity played a central role in metabolic adaptation to flooding stress. Possible role of these responses in flooding tolerance in Brachiaria species is discussed.