Ricardo Blanco

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.

Seedling development and biomass as affected by seed size and morphology in durum wheat

This work evaluated the effect of seed size and morphology on the development and biomass of durum wheat seedlings. Three different seed-grading sizes selected by sieving were used in glasshouse experiments, and a set of three developmental and 23 biomass-related indices were measured on eight genotypes, at two moisture levels. The influence of seed size on seedling development was studied at high and low temperatures (2212 mC, and 155 mC daynight temperatures, respectively), in growth chambers. nThe area of the seed and the area of the embryo were the seed morphological traits most affected by seed size. Seed size was strongly associated with seedling development and seedling biomass until nthe complete extension of the first two leaves, at the fourth leaf stage. The rate of first-leaf growth and the area of the first leaf were the developmental and biomass traits, respectively, most sensitive nto seed-grading size.

Leaf and green area development of durum wheat genotypes grown under Mediterranean conditions

Abstract Future increases in the potential yield of wheat will require an improvement in the photosynthetic area in early growth stages. Our aim was to investigate the genotypic and environmental effects on the pattern of leaf and green area development of durum wheat (Triticum turgidum L. cv. durum). Twenty-five genotypes were grown during 2 years under irrigated and rainfed conditions in Lleida (northeastern Spain). Leaf area index (LAI) and green area index (GAI) were determined on eight occasions from seedling to maturity and data were fitted to an asymmetric logistic peak curve. Multivariate analysis of variance was used to assess the curve characteristics responsible for differences between years, sites and genotypes. Genotypic differences in the pattern of changes in LAI and GAI from sowing to maturity were not statistically significant, indicating a lack of genetic diversity for these traits in the germplasm used in this study. A decrease in the peak of the curves of 27% for LAI and 35% for GAI was observed under rainfed conditions compared to the irrigated site. Drought caused a lengthening of crop development until anthesis of about 2% (3–4 days). Contrarily, the time from sowing to the maximum LAI and GAI values were reduced by drought in around 10%, causing an acceleration of the onset of plant senescence. Once started, the senescence of the green organs of the plant was more rapid at the irrigated than at the rainfed site. It is concluded that LAI and GAI patterns were more influenced by the environment (mainly water availability) than by the genotype. The results suggest a certain degree of independent regulation for phenological development and the swiftness of green area accumulation in the plant.

Grain growth and yield formation of durum wheat grown at contrasting latitudes and water regimes in a Mediterranean environment

A set of ten durum wheat genotypes was grown in experiments conducted under four contrasting Mediterranean conditions during three years to assess the effect of latitude and water regime on grain growth and grain yield formation. The relationship between grain weight and accumulated growing degree-days (GDD) from anthesis was described by a logistic equation and final grain weight (W) and maximum rate (R) and duration (D) of grain filling were calculated from the fitted curves. Thousand kernel weight (TKW) was positively related to grain yield at both latitudes and water regimes, although the contribution of the number of grains per m 2 to final yield was only significant in the south, where environmental constraints likely limited the achievement of a large grain set. Differences in final grain weight between latitudes could be mostly explained by differences in the grain filling rate, while changes on W between water regimes were due to altered grain filling durations. Under northern conditions grain yield was positively associated to grain filling duration but negatively related to the maximum rate of grain filling, while in the south the coefficients of the grain filling curves had little or no effect on final yield. Reductions in grain yield under rainfed conditions were due to the fall in the number of grains per m 2 since TKW was not significantly affected by drought.