PHENOTYPIC VARIATION IN BORON-TOXICITY TOLERANCE AT SEEDLING STAGE IN DURUM-WHEAT (TRITICUM-DURUM)

Nineteen durum wheat landraces, cultivars or advanced lines of different origins in West Asia and North Africa (WANA), and three barley and two bread wheat varieties were evaluated for their boron (B) toxicity tolerance. Seedlings were grown at five levels of soluble soil B in a plastic house under controlled temperatures. Significant differences existed between the durum wheat entries in days-to-symptom appearance and foliar symptom score. Under the highest soil B treatment, large differences existed between entries for dry weight per plant (P < 0.05) but differences were non-significant for shoot B concentrations. Days-to-symptom appearance was highly correlated with symptom score, which was not correlated with shoot B concentrations. Boron toxicity symptom scores of the durum wheat entries ranged from the sensitive barley check to the moderately sensitive bread wheat check. As expected, days-to-symptom appearance decreased and symptom severity increased as the soil B concentrations increased. The result of this study supported the preliminary finding that small, though statistically significant, variation in B toxicity symptom scores exist in durum wheat. The higher CV of symptom scores found here was mainly due to one sensitive entry, Cakmak. If Cakmak was excluded from the analysis, the CV would be reduced by half, to 10%. Durum wheat genotypes which are more tolerant to B toxicity should be sought. Based on the results of this study, and of soil surveys and information collected in WANA, germplasm collected from Algeria, Iraq, Libya, Syria, and the Anatolian Plateau of Turkey should be screened first.