VARIATION IN GROWTH, DEVELOPMENT, AND YIELD OF DURUM-WHEAT IN RESPONSE TO HIGH SOIL BORON .2. DIFFERENCES BETWEEN GENOTYPES

This greenhouse study examined the variation in growth, development, a nd yield between 9 durum wheat (Triticum turgidum L. var. durum Desf., syn. T. durum) lines in response to high soil boron (B) levels. The l ines were selected to represent the range of B-toxicity tolerance in a n earlier screening experiment. Three soil B levels (hot-water extract able B concentrations of 0.3, 7.1, and 17.4 mg/kg, designated as B0, B 25, and B50, respectively) were set up by mixing different amounts of boric acid with soil. Foliar B-toxicity symptom score, dry weight, and shoot-B concentration were measured at tillering. Agronomic traits an d yield were measured. There were differential responses to high soil B levels between the durum lines. The boron x line interaction was sig nificant for B-toxicity symptom score and shoot-B concentration. Based on these 2 characters, and percentage of shoot dry weight and grain y ield reduction from B0 to B50, Oued Zenati, Omrabi-5, and Gezira-17 we re the most tolerant of the 9 durum lines, yet they were less tolerant to high soil B levels than the tolerant bread-wheat check, Halberd. N onetheless, until more tolerant materials are developed, these moderat ely tolerant durum lines could still be useful for areas, like souther n Australia, where B toxicity is a problem.