Comparative salt tolerance of amphidiploid and diploid Brassica species.

Salt (NaCl) tolerance of three amphidiploid Brassica species, B. napus (AC genome), B. carinata (BC genome), and B. juncea (AB genome), and their putative diploid relatives, B. campestris (A genome), B. oleracea (C genome) and B. nigra (B genome) was examined under glasshouse conditions. The plants were grown in sand culture throughout the study period (51 days). Twenty-three day old plants of all six species were subjected for 28 days to control (0 mol m(-3) NaCl), 100 and 200 mol m(-3) NaCl in Hoagland nutrient solution. Under saline conditions, growth of the three amphidiploid species was significantly greater in shoot and root weights, and seed yield was greater than that of the diploids. The amphidiploids accumulated lower Na(+) but higher K(+) in their shoots and roots, the K/Na ratio therefore being considerably higher than those of the diploids. Ca(2+) accumulation was similar in the diploids and amphidiploids, and the Cl(-) accumulation pattern was not consistent in the different species. The occurrence of high salt tolerance of amphidiploids, and their enhanced K/Na discrimination with respect to their diploid relatives, suggests that salt tolerance has been obtained from A and C genomes and the latter trait from all three genomes (A, B, and C).