This result indicates that the B-exclusion mechanism is not involved in differential expression of B tolerance within 70 durum wheat genotypes. It seems very likely that the internal mechanisms (., adsorption to cell walls and compartementation of B in vacuoles) could be a more plausible explanation for B tolerance in the durum wheats tested in the present study. | Turk J Agric For 30 (2006) 49-58 © TÜB‹TAK Genotypic Variation in Tolerance to Boron Toxicity in 70 Durum Wheat Genotypes Ayfer A. TORUN1, Atilla YAZICI2, Halil ERDEM3, ‹smail ÇAKMAK2 1Çukurova 2Sabanc› University, Faculty of Agriculture, Department of Soil Science, Adana - TURKEY University, Faculty of Engineering and Natural Sciences, 34956, ‹stanbul - TURKEY 3Çukurova University, Faculty of Agriculture, Department of Soil Science, Adana - TURKEY Received: Abstract: By using 70 durum wheat (Triticum durum) genotypes, a greenhouse experiment has been carried out to study genotypic variation in tolerance to boron (B) toxicity in soil. Plants were grown in a soil containing 12 mg extractable B kg-1 soil and treated additionally with (+B: 25 mg kg-1 soil) and without B (-B: 0 mg B kg-1 soil). Following 30 days of growth, only shoots have been harvested and analyzed for dry matter production and shoot concentrations of B. There was a large genotypic variation in tolerance to B toxicity based on the severity of leaf symptoms and decreases in dry matter production caused by B toxicity. Among the genotypes tested, the growth of the genotypes Sabil-1, Stn “S”, Aconhi-89 and Wadelmez-2 was not affected; even, there was a tendency for an increase in growth by B treatment. By contrast, the dry matter production of all other genotypes was markedly decreased by the applied B, particularly in the genotypes Lagost-3, Dicle-74, Brachoua/134xS-61 and Gerbrach. In case of the genotypes Brachoua/134xS-61 and Gerbrach, B application reduced dry weight of the plants by 2-fold. Interestingly, there was no relationship between shoot B concentrations and relative decreases in shoot dry weight by B toxicity. The most B-sensitive genotypes had generally much lower amount of B in shoot than the genotypes showing higher tolerance to B toxicity. This result indicates that the B-exclusion mechanism is not involved in differential expression of B tolerance within 70 durum .
