Mapping of the locus associated with tolerance to high manganese in rapeseed (Brassica napus L.).

Rapeseed (syn. oilseed rape/canola, Brassica napus L, 2n = 4x = 38) is the world's third most important oilseed crop. Germplasm tolerant to high levels of manganese (Mn2+) is becoming increasingly important in areas where rapeseed is grown on acidic soils (pH <5.5). In Australia, canola quality rapeseed having low erucic acid and glucosinolate content occupies approximately 1.2-1.6 million ha of the cropped area in New South Wales, Victoria, South Australia and Western Australia and is estimated to be worth over $700 million. However soil acidity is a major sustainability and production issue within these regions with at least 10-15 million ha affected. Due to the seasonal variation that occurs in soil Mn2+ concentrations, Mn2+ toxicity in rapeseed, induced by low pH levels, climate and biological interaction in the soil, is complex, and often not a clearly identifiable disorder. Use of lime in Australia to increase pH is frequently limited as acidic soils are often sporadic and the cost of lime treatment in this country is relatively high. Genetic tolerance of plants to soil acidity can therefore play an important role as a component of acid soil management. Although rapeseed germplasm tolerant to high Mn2+ is available, currently there are no molecular markers associated with tolerance to high Mn2+ which may facilitate the introgression of this trait into sensitive material. This study was conducted to identify molecular markers associated with tolerance to high Mn2+.