Francesco Giunta

Effect of drought on yield and yield components of durum wheat and triticale in a Mediterranean environment

Field experiments were carried out with durum wheat and triticale under different moisture levels, in a typical Mediterranean climate. Yield of wheat showed significant reductions (by 25, 54 and 87%) under drought stress, while triticale showed only a slight and non-significant decrease (by 8%) in comparison to the irrigated control. The most severe stress (treatment S) caused a reduction in all the yield components of wheat, but particularly in the number of fertile ears per unit area (by 60%) and in the number of grains per ear (by 48%). In contrast, the reduction in yield under the mild stress was solely due to a lower grain weight. Harvest index and nitrogen harvest index were significantly decreased (going from 48 to 24% and from 64 to 42% respectively) in cases of severe drought in wheat. Male sporogenesis was only studied in the case of mild drought, which was not severe enough to delay it or to induce male sterility, and only caused sporogenesis to begin earlier. The greater drought resistance of triticale can be attributed to the earliness of its heading date and to the greater capacity of its roots to extract water from the soil.

SPAD readings and associated leaf traits in durum wheat, barley and triticale cultivars

SPAD readings may represent a useful screening criterion in breeding programs aimed at increasing the rate and duration of leaf photosynthesis. A two-year trial was conducted on 17 cultivars of durum wheat, 8 of triticale and 18 of barley at two experiment stations in Sardinia, Italy, to evaluate the existence of genetic variation for SPAD readings, and to quantify the genetic associations between SPAD readings, area per leaf blade (LA), specific leaf area (SLA), leaf nitrogen concentration (LNC) and leaf nitrogen per unit of leaf surface (LN) in the period between beginning of tillering and flag leaf appearance. Plants were grown at sufficient nitrogen fertilization. The average SPAD reading of barley was 9–10 units lower than that of durum wheat and triticale. The combined ANOVA indicated that, in all the three species, the genotype by environment interaction variance associated with SPAD readings was lower than the genetic variance. In durum wheat and barley, SPAD readings exhibited a greater genetic variance in comparison with LNC, LN and SLA. In durum wheat and triticale, SPAD readings were genetically correlated with LN and SLA. Durum wheat differed from triticale because its genetic variation in SLA was not associated with LA. A screening based on both SPAD readings and LA values should identify lines with good photosynthetic machinery that is not associated with low area per leaf blade.

Relationship between grain yield and quality of durum wheats from different eras of breeding

High protein content and a ‘strong’ gluten are required in durum wheat (Triticumturgidum L. var. durum) to process semolina into a suitable final pasta product. The variation in grain protein content and quality realized through breeding and the concomitant variation in biomass production and partitioning have been analyzed by comparing in a 2-year field trial, four groups of cultivars released in different eras and areas of breeding. Three groups of cultivars represented the evolution of the Italian germplasm from the first landraces and genealogical selections (Group 1) to the cultivars constituted by crossing Mediterranean types with Syriacum types (Group 2), and the modern dwarf and semi-dwarf cultivars (Group 3). Group 4 was an ICARDA collection of breeding lines bred for adaptation to high altitudes. The measured traits included both biomass production and its partitioning to the grain, and total nitrogen uptake and its partitioning to the grain. Grain protein percentage, gluten content and gluten index were utilized as quality traits. Breeding resulted in an increased earliness, reduced height without significant decreases in total biomass, and improved partitioning. The concomitant total nitrogen uptake did not change, whereas the changed biomass partitioning caused a parallel change in nitrogen partitioning, with an increase in nitrogen harvest index from 0.41 to 0.59. The lower protein percentage in the grains of modern cultivars was therefore not due to a reduced nitrogen uptake, nor to a lower NHI or to less milligram of nitrogen per grain, but to the dilution effect caused by the heavier grains of modern cultivars. A notable increase in gluten index was observed in the modern cultivars, reflecting an improvement in the pasta-making quality of grain proteins.

Relationships between grain-filling parameters, fertility, earliness and grain protein of durum wheat in a Mediterranean environment

Abstract Seven Italian durum wheat ( Triticum turgidum L. var. durum ) cultivars characterized by different height, time to anthesis, fertility and kernel weight were compared under different moisture levels and soil types in two experiments. Duration, and maximum and average rate of grain-filling (GF) were estimated from 2nd and 3rd order polynomials, regressing kernel weight on growing degree days (GDD, base temperature 9°C). In both experiments Messapia was the earliest cv, flowering between 132 and 139 days after sowing (das), and Vespro and Creso the latest, flowering between 141 and 148 das. The largest kernels, ranging between 51.8 and 59.5 mg, were always realized by these three cultivars and were always associated with the highest rates of GF. Average rates ranged from 105 to 152 μg °C day −1 and were significantly correlated, both environmentally and phenotypically, with maximum kernel weight. Maximum rates of GF, ranging from 172 μg °C day −1 in the genotype D3415 to 282 μg °C day −1 in cv Creso, were only phenotypically correlated with maximum kernel weight. GF duration was related to earliness as it ranged from a minimum of 380 GDD in the late cv Vespro, to a maximum of 481 GDD in the earliest cv Messapia. Fertility varied greatly, from 37 kernels per spike in Creso and Vespro, to 61 kernels per spike in Vespro. Significant differences in grain protein were recorded between cultivars (8.9% in Karel to 15.8% in D3415) and soils (10.8% and 14.1%). In this environment, large kernels can be achieved with genotypes characterized by high rates of GF, irrespective of earliness, and without negative effects on spike fertility and on grain protein content.

Awnedness affects grain yield and kernel weight in near-isogenic lines of durum wheat

The importance of awns in durum wheat (Triticum turgidum L. var. durum) has to be evaluated whenever an increase in grain yield is expected due to a greater photosynthetic capacity of the awned ear. Awned and awnless isolines of durum wheat were compared in a 3-year field trial in Sardinia (Italy). Ear and flag-leaf size, radiation interception, canopy temperature, yield, and yield components were measured. Awns increased the ear surface area from 36 to 59%, depending on their length, which ranged from 5.5 to 13.8 cm. This resulted in an average 4% more radiation intercepted by the awned ears. Canopy temperature was 0.9°C lower, on average, in the awned isolines, and was negatively correlated with kernel weight (r = –0.85**, n = 10), although consistent and marked effects of awns on canopy temperature were only observed in the long-awned lines. Awns positively affected grain yield, with an average increase of 10 and 16%, respectively, in the 2 years in which they affected kernel weight. The irrelevant effect of awns on yield in the year characterised by a severe drought was a consequence of their early desiccation. The effects of awns on grain yield and kernel weight strongly depend on the genetic background, on awn length and functionality, and on the environmental conditions during grain filling.

Expression of a tiller inhibitor gene in the progenies of interspecific crosses Triticum aestivum L.×T. turgidum subsp. durum

Abstract The genetic inhibition of tillering in wheat can be useful for two reasons: firstly, to control leaf area development and hence water use in water limited environments; secondly, to reduce the incidence of unproductive tillers. Bread wheat lines (Triticum aestivum L.) carrying the major gene tin responsible for both reduced tillering and gigas features, were crossed with durum wheat cultivars (Triticum turgidum subsp. durum) to evaluate the pleiotropic effects of the tin gene in the new genetic background. Phenotypic and genetic correlations were calculated on data recorded in F3 and F4 generations. HI was negatively correlated with the number of culms both phenotypically ( r P =−0.73 ∗∗ ) and genetically ( r A =−0.50 ∗∗ ), and increased from 0.31 in freely tillering plants to 0.35 in uni- and bi-culm plants. Low tillering was also associated with greater grain yields per ear, mainly resulting from a greater spikelet fertility (up to 3.5 kernels per fertile spikelet) and a lower incidence of sterile spikelets. The presence of the tin gene also resulted in some negative effects, namely an increase in chaff weight more than proportional to the increase in ear fertility, and a greater culm density. These negative effects were responsible for the less than expected increase in HI. No substantial differences were observed in the pleiotropic effects of the tin gene in the studied progenies in comparison with bread wheat.

Environmental conditions affect semolina quality in durum wheat (Triticum turgidum ssp. durum L.) cultivars with different gluten strength and gluten protein composition

BACKGROUND Sowing time may impact semolina and pasta cooking quality by changing the environmental conditions during grain filling. The effect of an optimum and a delayed sowing time on semolina quality was studied by comparing six cultivars under irrigation, in order to isolate temperature from drought effects. RESULTS Protein content was higher in the old cultivars and in the late sowings, according to the number of days with temperature between 30 and 40 °C during ripening. Gluten index increased as temperature rose to a threshold of about 30 °C, then decreased under higher temperatures. Mixograph parameters were less sensitive to high temperatures. Gliadin:glutenin correlated with gluten strength. Spaghetti firmness and protein content were positively correlated independently of sowing date. Cultivars Trinakria and Cappelli had the highest spaghetti firmness (900 and 828 g). CONCLUSIONS Late sowings may represent a way of increasing pasta cooking quality whenever they place grain filling under thermal conditions able to increase protein percentage, although the accompanying decrease in yield may represent a drawback in environments prone to drought stress during ripening. The lower protein percentages of modern durum wheat cultivars under conventional sowing times results in a lower pasta cooking quality despite higher gluten strength.

Factors affecting the genotype × environment interaction in spring triticale grown in a Mediterranean environment

The identification of the genotypic and environmental factors responsible for the genotype by environment interaction is essential in any breeding program. A Multi Environmental Trial (MET) including 3 years, 3 locations and 14 lines of spring triticale (× TriticosecaleWittmack) was carried out in a Mediterranean environment (Sardinia, Italy). Water available to the crops was calculated through a model run with the environmental variables and the phenological data recorded in each environment. Yield, yield components and heading date were used to perform an Additive Main effects and Multiplicative Interaction (AMMI) analysis. Interaction for yield was relevant only in 2 environments out of 8, one characterised by a late sowing, the other by the warmest pre-anthesis period. Correlations between Interaction Principal Component Axis (IPCA) scores and environmental and genotypic variables showed that genotype by environment interaction for yield and kernels per m2 is related to interaction for phenology but not to the yield level. Yield level was significantly correlated with the water availability. Genotype by environment interaction for yield is mainly determined by thermal conditions in the pre-anthesis period, genotypic photoperiodic sensitivity and sowing time.

Development of durum wheat and triticale cultivars as affected by thermo-photoperiodic conditions

The understanding of the interaction between thermo-photoperiodic conditions and the genetic control of anthesis date is fundamental in explaining the environmental adaptation of durum wheat and triticale cultivars. The development of 8 durum wheat (Triticum turgidum L. var. durum) and 2 triticale (× Triticosecale Wittmack) cultivars was studied at 3 sowing dates (September, November, and March) by observations on apex development, number and rate of leaf appearance, spike fertility, and number and length of elongated internodes. Variation in anthesis date was mostly explained by the total number of leaves, which ranged between 8.3 and 15, and hence by the duration of the phase of leaf primordium production. Total leaf number also affected the length of the subsequent phase until flag leaf appearance. The phyllochron was influenced by both sowing date and genotype, and was minimum in the March sowing (87 degree-days). The genotypic variability in phyllochron was due either to the variations in leaf number or to genotypic intrinsic differences. Time to terminal spikelet stage was related to the number of spikelets per spike and to the number of elongated internodes, although stem length depended more on internode length than on internode number. The number of spikelets per spike was associated with leaf number, but their relationship was affected by the thermal conditions during spikelet primordium initiation. No differences were observed between wheat and triticale cultivars, apart from the number of spikelets per spike.

Grain yield, dry matter, and nitrogen accumulation in the grains of durum wheat and spring triticale cultivars grown in a Mediterranean environment

Comparisons among species can be a valuable approach to identifying traits important for plant breeding. Differences between 2 durum wheat (Duilio and Creso) and 1 triticale (Antares) cultivar have been analysed in a 2-year field trial in Sardinia (Italy), in order to define a more productive durum wheat ideotype for Mediterranean- type environments. The greater grain yield (569 v. 447 g/m 2 ) and the lower protein percentage (9.2 v. 10.6%) of triticale cv. Antares compared with the durum wheat cultivars, at a similar level of biomass produced at heading, were analysed in terms of number of grains per unit surface and rate and duration of dry matter (DM) and nitrogen (N) accumulation, calculated from a logistic curve. When the single grains were considered, Antares showed a lower rate but a longer duration of DM and N accumulation in the more favourable season, resulting in lower DM (40 v. 54 mg) and N (0.7 v. 1.0 mg) contents in the grain. On the other hand, when data were expressed on a per unit surface basis, the greater spike fertility of Antares (53 v. 39 grains per spike) and its longer duration of accumulation, were responsible for similar or even greater amounts of DM and N accumulated in the grains per m 2 . Growth rate of single grains, although able to explain differences in single grain weight, cannot explain differences in grain weight per m 2 and hence in yield, which mainly result from variation in the number of grains per spike. Nitrogen percentage of the grains decreased from the maximum values observed at the beginning of grain filling, until a constant final value attained before the end of DM and N accumulation. Rate is more important than duration in determining the quality characteristics of grains, as higher grain weights and protein percentages correspond to higher rates of DM and N accumulation.