Responses of six Brachiaria spp. accessions to root zone flooding

Some morphophysiological responses of Brachiaria brizantha cv. Marandu, cv. Piata, cv. Arapoty, B163, B166 and B. ruziziensis R124 were compared in plants grown in pots, under flooded and well-drained conditions. Flooding reduced leaf elongation rate in all accessions. Leaf dry mass production was lower under flooding than in the control plants in all the studied accessions, except in cv. Piata. Root dry mass production was reduced by flooding in cv. Marandu and in R124, while the proportion of biomass allocated to roots was reduced by flooding only in R124. It was not possible to detect significant differences between water regimes in the percentage of biomass allocated to culms and leaves for all accessions. Flooding decreased the number of tillers in cv. Marandu, in B163, B166 and in R124. Relative growth rate was decreased by flooding in cv. Marandu, in B163 and in R124. Flooding reduced gas exchange parameters in all accessions, but cv. Arapoty. The accessions tested differ in their relative tolerance to flooding. B. brizantha cv. Arapoty is considered the most tolerant. B. ruziziensis R124 is the most sensitive, followed by B. brizantha cv. Marandu. B. brizantha cv. Piata, B163 and B166 are intermediate in flooding tolerance.