L. F. García del Moral

Durum wheat quality in Mediterranean environments. I. Quality expression under different zones, latitudes and water regimes across Spain

Ten durum wheat genotypes were studied in a total of 10 field trials in three different regions of Spain, associated with two latitudes (north and south) under both irrigated and rainfed conditions during the 1998 and 1999 growing seasons. Different technological and commercial quality parameters were studied: thousand kernel weight (TKW), test weight, vitreousness, ash content, protein content, pigment content and the SDS sedimentation test. The results demonstrated the strong influence of environmental conditions on the majority of quality traits in durum wheat, with growing zones, latitudes and moisture regimes showing the greatest effects. Genotypic effects were mainly observed for pigment content and SDS volume. These appear to be predominantly under genetic control. TKW and protein content were higher in Lleida in the north, probably due to the greater amount of nitrogen applied in comparison with Granada and Jerez in the south. Grain quality under the growing conditions of Lleida, however, was negatively influenced by the high percentages of ash accumulated in the grain. In general, Granada and Jerez provided an acceptable grain quality, and Jerez in particular favoured good semolina colour and higher test weights. Moisture stress increased mainly protein content and vitreousness, and reduced TKW and ash content at both latitudes. It is clear that rainfed conditions in the south offer the best opportunity for production of durum wheat of good quality.

Durum wheat quality in Mediterranean environments II. Influence of climatic variables and relationships between quality parameters

A total of 10 field experiments were carried out during the 1998 and 1999 growing seasons both in the north (Lleida) and the south (Granada and Jerez) of Spain. In Lleida and Granada, the experiments were conducted under both irrigated and rainfed conditions, while the Jerez trials were carried out only under rainfed conditions. Ten durum wheat genotypes were used in this study. Quality determinations consisted of 1000-kernel weight (TKW), test weight, vitreousness, ash content, protein content, pigment content and SDS sedimentation test. The influence of environment was predominant in determining the majority of quality traits, although pigment content and SDS volume were also genetically controlled. Environmental effects, studied by the mean of the climatic patterns influencing each trial, showed that total water input during grain filling appears to negatively affect grain quality by reducing test weight, grain vitreousness, and SDS volume, and by increasing ash content. High seasonal temperatures increased pigment content in the grain, but reduced TKW. From the correlations between quality parameters, an inverse and interesting relationship was found between protein content and SDS volume. Relationships between quality traits appear to be influenced to a certain extent by climatic conditions during grain filling and, depending on temperatures and water input during this phase, correlation coefficients can be either positive, negative or close to zero.

Durum wheat quality in Mediterranean environments: III. Stability and comparative methods in analysing G×E interaction

Stability of grain quality characteristics is an interesting feature of today’s durum wheat breeding programmes, due to the high annual variation in both grain yield and quality, particularly in the Mediterranean area. Ten field trials were carried out during two seasons (1998 and 1999) in both the north (Lleida) and south (Granada and Jerez) of Spain. Ten durum wheat genotypes were used, including four Spanish commercial varieties and six advanced lines from the durum wheat breeding programme of CIMMYT-ICARDA. Many quality parameters were evaluated in this study including thousand kernel weight, test weight, vitreousness, ash content, protein content, pigment content and the SDS sedimentation test. Several statistical methods and techniques were used to describe the genotype×environment (G×E) interaction and to define stable genotypes in relation to the seven quality parameters considered in this study. The partition and interpretation of the G×E interaction revealed that the joint regression analysis was not efficient and demonstrated the usefulness of AMMI for describing the interaction patterns. The study of genotypic stability demonstrated that the Spanish commercial varieties, Altar-aos and Jabato and the CIMMYT-ICARDA advanced line, Waha, had high stability for quality characteristics and proved to be the best within the pool of the studied genotypes.

Yield Formation in Mediterranean durum wheats under two contrasting water regimes based on path-coefficient analysis

The components of grain yield are altered by adverse growing conditions as the effects of certain environmental factors on crop growth and yield differ depending upon the developmental stages when these conditions occur. Path-coefficient analysis was used to investigate the main processes influencing grain yield and its formation under Mediterranean conditions. Twenty-five durum wheat genotypes, consisting of four Spanish commercial varieties and 21 inbred lines from the ICARDA durum wheat breeding program, were grown during 1997 and 1998 under both rainfed and irrigated conditions in southern Spain. {P}ath-coefficient analysis revealed that under favourable conditions grain yield depended in equal proportion on the three primary yield components (i.e. spikes m−2, grains spike−1, and mean grain weight), whereas in the rainfed experiments, variations in grain yield were due mainly to spikes m−2 and to a lesser extent to grains spike−1. Compensatory effects were almost absent under irrigated treatments; however, under water shortage, spikes m−2 exerted a negative influence on grain spike−1 due mainly to a negative interrelationship between tiller production and apical development. These compensatory effects could partially explain the restricted success in durum wheat breeding observed in water-limited environments of the Mediterranean region. Under rainfed conditions the number of spikes m−2 depended mainly on the ability for tiller production, whereas in the irrigated experiments the final number of spikes was determined mostly by tiller survival.

Yield development in potatoes as influenced by cultivar and the timing and level of nitrogen fertilization

Path-coefficient analysis based on an ontogenetic model was used to study the relationships between tuber yield and yield components as influenced by cultivar and nitrogen fertilization. Four experiments were carried out from 1987 to 1989 in Granada, southern Spain. Two of these experiments used six potato cultivars with a single N rate, while the other two experiments used one cultivar and nine levels of N, split between planting and top-dressing. Variation in tuber yield between cultivars resulted mainly from differences in stem number per m2 followed by tubers per stem and, to a lesser extent, average tuber weight. In N experiments, however, average tuber weight was the only yield component that showed a significant direct effect on yield, while the number of stems per m2 and tubers per stem had negligible direct effects. In addition, the ontogenetic model used indicated compensatory mechanisms during the formation of the three yield components in the potato, which resulted stronger in the N experiments.CompendioPara estudiar las relaciones entre la producción de tubérculos y los componentes del rendimiento en función de la variedad y fertilización nitrogenada en el cultivo de patata, se ha realizadado un análisis mediante coeficientes de sendero (path-coefficient analysis) basado en un diagrama ontogénico. Se han llevado a cabo para ello cuatro experimentos entre 1987 y 1989 en Granada, Sur de España. Dos de ellos con seis variedades, y otros dos con nueve dosis de N total, repartido entre fondo y cobertera. Las variaciones en la producción de tubérculos debidas a la variedad han dependido principalmente del número de tallos por m2, del número de tubérculos por tallo y en menor proporción del peso medio de los tubérculos. Sin embargo, en los experimentos de aplicación de N, el peso medio por tubérculo fue el único componente del rendimiento que mostró un efecto directo significativo sobre la producción final, mientras que el número de tallos por m2 y el número de tubérculos por tallo sólo ejercieron efectos directes insignificantes. El diagrama ontogénico utilizado reveló también la existencia de mecanismos de compensación durante la formación de los tres componentes del rendimiento en la patata, que resultaron más pronunciados en los experimentos de N

Integration of statistical and physiological analyses of adaptation of near-isogenic barley lines

Seven near-isogenic barley lines, differing for three independent mutant genes, were grown in 15 environments in Spain. Genotype x environment interaction (G x E) for grain yield was examined with the Additive Main Effects and Multiplicative interaction (AMMI) model. The results of this statistical analysis of multilocation yield-data were compared with a morpho-physiological characterization of the lines at two sites (Molina-Cano et al. 1990). The first two principal component axes from the AMMI analysis were strongly associated with the morpho-physiological characters. The independent but parallel discrimination among genotypes reflects genetic differences and highlights the power of the AMMI analysis as a tool to investigate G x E. Characters which appear to be positively associated with yield in the germplasm under study could be identified for some environments.

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.

Image Analysis of Grain and Chemical Composition of the Barley Plant as Predictors of Malting Quality in Mediterranean Environments

ABSTRACT We have explored the possibility of predicting the malting quality of barley grain, indicated by malt extract yield, by characteristics measured either on plants at anthesis or in mature dry grain by image analysis. To produce barley samples with varying levels of all the characteristics studied, we used grain from an experiment designed to study the influence of lowinput husbandry practices on malting quality of barley by growing five malting genotypes at each of four environments (site × season) and with two different agronomic treatments (N fertilization and herbicide-mechanical roguing of weeds). The results showed that nitrogen content in the plant at anthesis was a good predictor of grain protein content, this characteristic in turn being positively correlated with embryo size and grain volume, as estimated by image analysis, and negatively correlated with nonstructural carbohydrate content in the plant at anthesis. Extract yield was positively correlated with Kolbach index (ratio of solubl...

Usefulness of remote sensing for the assessment of growth traits in individual cereal plants grown in the field

Biomass determination usually involves destructive and tedious measurements. This study was conducted to evaluate the usefulness of the Normalized Difference Vegetation Index (NDVI) and the Simple Ratio (SR), calculated from the spectra of individual plants, for the assessment of leaf area per plant (LAP), green area per plant (GAP) and plant dry weight (W) at different growth stages. Two varieties of four cereal species (barley, bread wheat, durum wheat and triticale) were sown in a field experiment at a density of 25 plants m−2. The spectra were captured on three plants per plot on eight occasions from the beginning of jointing to heading using a narrow‐bandwidth visible‐near‐infrared portable field spectroradiometer adapted for measurements at plant level. Strong associations were found between NDVI and SR and growth traits, both indices being better estimators of GAP and W than of LAP. Exponential models fitted to NDVI data were more useful for a wide number of situations than the linear models fitted to SR data. However, SR was able to discriminate between genotypes within a species. The accuracy of the reflectance measurements was comparable to that obtained by destructive measurements of growth traits, in which differences between varieties of over 24% were needed to be statistically significant. However, differences in SR of only 18% were statistically significant (P<0.05). The reliability of the spectral reflectance measurements and the non‐destructive nature convert this methodology into a promising tool for the assessment of growth traits in spaced individual plants.

Barley response to nitrogen rate and timing in a Mediterranean environment

Nitrogen is an important factor determining grain yield of barley ( Hordeum vulgare L.). Optimal rates and application timing can vary according to the environmental conditions under which the crop is grown. For 8 years (1979–86) barley yield, tillering, and leaf-area response to N application rates and timing were studied in southern Spain. The results showed that, under our experimental conditions, the most advantageous N rate for grain yield was 60 kg/ha, either split equally between sowing and tillering, or else with the greater proportion applied at tillering. Nitrogen applied at sowing increased number of tillers per plant, and N applied at tillering favoured tiller survival for later spike formation. In addition, N applied at tillering increased the number of leaves per plant, leaf area per plant, and the leaf area index, the maximum value of which occurred at anthesis.