The effect of breeding on the phenology of Italian durum wheats: From landraces to modern cultivars

An understanding of the changes in phenology resulting from durum wheat breeding in Italy can inform breeding objectives for durum wheat improvement in Mediterranean environments. The phenology of a set of 20 durum wheat cultivars, grouped according to their period of release into ‘old’, ‘intermediate’ and ‘modern’, was compared in two sowings (September and May) with or without artificial vernalization. The vernalization treatment and the 6 h range in daylength and wide variation in temperature were responsible for the variation in anthesis date from 817 to 2105 °Cd (base 0 °C) from sowing. Old cultivars had the greatest photoperiod sensitivity and cold requirement, intermediate ones the greatest earliness per se and modern ones the least photoperiod sensitivity and greatest earliness per se. The first substantive effect of breeding in Italy on phenology was achieved with introgression from syriacum germplasm, which increased earliness both by an increase in earliness per se and a reduction in photoperiod sensitivity. The next step, characterized by the introduction of the semi-dwarfing gene Rht1, had a specific effect of reducing photoperiod sensitivity, although the modern group of varieties has a relatively low level of earliness per se, which is fundamental for preserving and increasing the length of the TS-anthesis period. Some quantitative cold requirement still persists in Italian germplasm, although all the cultivars tested are classified as spring types. The main phenological events affected by the changes in anthesis date resulting from breeding depend on the mechanism involved. Variability among cultivars within each group is also described.     

Genotypic variation in durum wheat root systems at different stages of development in a Mediterranean environment

Summary Glasshouse and field experiments were carried out to compare root growth of eight durum wheat genotypes at different stages of development with different moisture levels and in different soils. Genotypic differences were found, particularly at the stem elongation and heading stages of development, but the ranking of genotypes varied in relation to soil moisture level and fertility. Differences under optimal moisture level were mainly due to differences in tillering and disappeared by considering the root number and weight per culm. Drought caused an increase in the root-to-total-plant weight ratio (18.5 vs 14.3% at heading) but also an increase in absolute root weight. Karel, the genotype with the largest root mass under drought and the greatest proportion of roots in the upper soil layers (more than 50% in the 0–20 cm layer from heading onwards), showed the lowest yield reduction under severe stress. A large root system with a high density of roots in the upper layers of the soil profile may be beneficial in Mediterranean climates.Research supported by a grant of Ministero della Pubblica Istruzione (40%).     

The effect of nitrogenous fertiliser application on leaf traits in durum wheat in relation to grain yield and development

Nitrogen (N) fertilisation boosts the grain yield of wheat through its influence on yield components, phenology and leaf traits. Both crop growth and senescence are dependent on N supply, as are the number of kernels set per unit area and per ear, and the mean kernel size. A two-season trial of four semi-dwarf durum wheat cultivars, grown at two levels of N, was used to illustrate the effects of N on canopy temperature, leaf resistance and flag leaf senescence pattern under irrigated conditions in a Mediterranean climate, and to explore the consequences of these effects on the crop phenology, its yield and its yield components. The well-fertilised crop developed a larger leaf area index at anthesis and a lower leaf resistance, thus generating a lower canopy temperature and delayed anthesis. Its grain fill duration was shorter, in spite of its lower canopy temperature, presumably because the increased N availability resulted in the development of a stronger sink (more kernels per unit area and per ear), which was associated with earlier senescence, thereby shortening the duration of grain fill, and led to reduced kernel weight.     

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. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development and validation of an ultrasensitive chemiluminescent enzyme immunoassay for aflatoxin M1 in milk

A fast and ultrasensitive chemiluminescent enzyme immunoassay for aflatoxin M(1) in milk samples has been developed and validated. The method is an indirect competitive type format involving the immobilization of an aflatoxin M(1)-bovine serum albumin conjugate on 384 well black polystyrene microtiter plates and the use of a secondary antibody labeled with horseradish peroxidase detected with a luminol-based substrate. Aflatoxin M(1) standard solutions were prepared in milk-based buffer, and milk samples were analyzed without any cleanup procedure. The limit of quantification was 1 ppt, the coefficient of variation was below 9% for both intra- and interassay precision, and the recovery ranged from 96 to 122%. The method is specific, and other aflatoxins do not significantly cross-react with the antibody. Twenty-four milk samples were analyzed, and a good correlation was observed (y = 0.98x + 1.71, r(2) = 0.98, n = 24) when the data were compared with a reference high-performance liquid chromatography method with a fluorescent detector. The developed method is suitable for an accurate, sensitive, and high-throughput screening of aflatoxin M(1) in milk samples with a reduction of costs and increased detectability, as compared with previously developed immunoassays.     

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. This revised version was published online in August 2006 with corrections to the Cover Date.     

Fructan and free fructose content of common Australian vegetables and fruit

Fructans are not digested in the small intestines of humans. While many health benefits have been attributed to these carbohydrates, they can cause gastrointestinal symptoms in some individuals. We measured the total fructans in 60 vegetables and 43 fruits using the Megazyme fructan assay. Vegetables with the highest quantity of fructans included garlic, artichoke, shallots, leek bulb, and onions (range, 1.2-17.4 g/100 g fw). Fruits with low, but detectable, fructans included longon, white peach, persimmon, and melon (range, 0.21-0.46 g/100 g fw). The fructan assay was modified to provide an estimate of the average chain length (degree of polymerization) for high fructan vegetables. d-Fructose can also be malabsorbed in the small intestine of humans, so the d-fructose content in some foods was measured to supplement the current food tables. Research in this area will be facilitated through the availability of more comprehensive food composition data.