LINKAGE OF RFLP MARKERS TO AN ALUMINUM TOLERANCE GENE IN WHEAT

More than 20% of the world's agricultural land may contain acid soil. Aluminum toxicity becomes a serious growth limiting factor in many pla nt species when the soil pH is lower than 5.5. Wheat (Triticum aestivu m L.) genotypes differ widely in tolerance to excess Al, and breeding of more tolerant genotypes is a priority in many affected regions. Our objectives were to confirm the number of genes for Al tolerance and d etermine their chromosomal arm location in the Brazilian wheat cv. BH 1146 and to identify DNA markers linked to Al tolerance gene(s). A pop ulation of recombinant inbred lines, developed by single-seed descent from the cross of BH 1146 x 'Anahuac', was screened for Al tolerance w ith two methods in hydroponic nutrient solution. Both methods showed a bimodal distribution for Al tolerance, consistent with single gene in heritance. Eighty-three low-copy DNA clones were used to screen for po lymorphism between the parents. Clone bcd1230 detected a restriction f ragment that is located 1.1 centiMorgans from this gene on Chromosome 4DL and explained 85% of the phenotypic variation in Al tolerance. We propose the symbol Alt(BH) to designate the major gene for Al toleranc e located on 4DL. This RFLP marker can aid the transfer of this gene i nto sensitive germplasms.