Triticale grain growth and morphometry as affected by drought stress, late sowing and simulated drought stress

The effects on grain filling and morphometry of natural drought, late sowing and simulated drought by means of a chemical treatment with potassium iodide (KI) were compared over 3 years of field trials in triticale ( ¥ Triticosecale Wittmack) cv. Trujillo and three near-isogenic lines derived from it. Grain weight data fitted accurate to a logistic curve. The maximum rate of grain filling was the curve coefficient most sensitive to drought stress, and accounted for 7–50% of grain yield variation. Chemical treatment with KI caused greater variation in grain filling curve coefficients and grain morphometry than did a delay in the sowing date, which in turn caused greater variation than natural drought. The type and magnitude of the effects of the different kinds of stresses on grain growth and morphometry could be related to the time that elapsed from anthesis, at which time the effects were perceptible. KI reduced the maximum rate of grain filling and final grain weight by 38 and 32%, respectively, its effect being significant from 8 d after the treatment. The volume of grain was reduced 11% by KI. The impact of delayed sowing date and drought were significant 29 and 33 d after anthesis, respectively, corresponding to the end of the linear phase of the grain filling curves. Both treatments diminished grain filling duration (13% by delayed sowing, and 6% by drought, respectively), final grain weight (16 and 12%, respectively), grain volume (15% and 8%, respectively), and embryo area (8% in both cases), but neither altered the maximum grain filling rate.