Variation in growth, development, and yield of durum wheat in response to high soil boron .1. Average effects

A greenhouse study was conducted to examine how the performance of a group of durum wheat (Triticum turgidum L. var. durum Desf., syn. T. Durum) lines was affected by high soil boron (B) levels in terms of growth, phenological development, and grain yield components. Three soil B levels (hot-water extractable B concentrations of 0.3, 7.1, and 17.4 mg/kg) were set up by mixing soil with boric acid. Foliar symptom scores of B toxicity were taken at the beginning of tillering. Six seedlings were then harvested from each pot for measurement of dry weight and shoot B concentration. Days to heading, numbers of tillers and heads, giant height, flag-leaf area, grain and straw yield, and number of grains were also measured. The high soil B level (17.4 mg/kg) caused symptoms of B toxicity on the foliage, increased shoot B concentrations, retarded growth, and reduced grain yield. Other effects included delayed heading; greater reduction in grain yield than straw yield; severely reduced grain yield per tiller due to an increase in aborted tillers; and decreased 1000-grain weight and number of heads per plant. The moderately high soil B level (7.1 mg/kg) also severely depressed the grain yield of these durum lines.