Dual-purpose wheat grain and animal production under different grazing periods

The objective of this work was to evaluate the influence of different grazing periods on beef animal production and on wheat forage and grain yield. The experiment was carried out in Pato Branco, PR, Brazil. Six grazing periods were evaluated (0, 21, 42, 63, 84, and 105 days) on dual-purpose wheat cultivar BRS Tarumã. Purunã steers, with average live weight of 162 kg and ten months of age, were kept under continuous grazing using a variable stocking rate, in order to maintain the established sward height of 25 cm. Greater increases in total animal gain (TAG) occurred with longer grazing periods. However, there was little increase after 63 days (490 kg ha-1), and TAG decreased from 552 to 448 kg ha-1 between 84 and 105 days. Grain yield decreased from 2,830 to 610 kg ha-1 when the grazing period increased from 0 to 105 days, but there was little change after 63 days (750 kg ha-1). Cultivar BRS Tarumã shows excellent animal production potential, and the decision on how long wheat pastures should be grazed must be based on relative prices of grain and livestock.

Methods for assessment of pre-harvest sprouting in wheat cultivars

The objective of this work was to test methods for pre-harvest sprouting assessment in wheat cultivars. Fourteen wheat cultivars were grown in Londrina and Ponta Grossa municipalities, Paraná state, Brazil. They were sampled at 10 and 17 days after physiological maturity and evaluated using the methods of germination by rainfall simulation (in a greenhouse), in-ear grain sprouting, and grains removed from the ears. The in-ear grain sprouting method allowed the differentiation of cultivars, but showed different resistance levels from the available description of cultivars. The sprouting of grain removed from the ears did not allow a reliable distinction of data on germination in any harvest date or location. The method of rainfall simulation is the most suitable for the assessment of cultivars as to pre-harvest sprouting, regardless of the sampling date and evaluated location.

Faba beans in diets for growing-finishing pigs

Selostus: Härkäpapu lihasikojen ruokinnassa

Wheat alleles introgress into selfing wild relatives: empirical estimates from approximate Bayesian computation in Aegilops triuncialis.

Extensive gene flow between wheat (Triticum sp.) and several wild relatives of the genus Aegilops has recently been detected despite notoriously high levels of selfing in these species. Here, we assess and model the spread of wheat alleles into natural populations of the barbed goatgrass (Aegilops triuncialis), a wild wheat relative prevailing in the Mediterranean flora. Our sampling, based on an extensive survey of 31 Ae. triuncialis populations collected along a 60 km × 20 km area in southern Spain (Grazalema Mountain chain, Andalousia, totalling 458 specimens), is completed with 33 wheat cultivars representative of the European domesticated pool. All specimens were genotyped with amplified fragment length polymorphism with the aim of estimating wheat admixture levels in Ae. triuncialis populations. This survey first confirmed extensive hybridization and backcrossing of wheat into the wild species. We then used explicit modelling of populations and approximate Bayesian computation to estimate the selfing rate of Ae. triuncialis along with the magnitude, the tempo and the geographical distance over which wheat alleles introgress into Ae. triuncialis populations. These simulations confirmed that extensive introgression of wheat alleles (2.7 × 10(-4) wheat immigrants for each Ae. triuncialis resident, at each generation) into Ae. triuncialis occurs despite a high selfing rate (Fis ≈ 1 and selfing rate = 97%). These results are discussed in the light of risks associated with the release of genetically modified wheat cultivars in Mediterranean agrosystems.

Salt tolerance and regulation of gas exchange and hormonal homeostasis by auxin-priming in wheat

The objective of this work was to assess the regulatory effects of auxin-priming on gas exchange and hormonal homeostasis in spring wheat subjected to saline conditions. Seeds of MH-97 (salt-intolerant) and Inqlab-91 (salt-tolerant) cultivars were subjected to 11 priming treatments (three hormones x three concentrations + two controls) and evaluated under saline (15 dS m-1) and nonsaline (2.84 dS m-1) conditions. The priming treatments consisted of: 5.71, 8.56, and 11.42 × 10-4 mol L-1 indoleacetic acid; 4.92, 7.38, and 9.84 × 10-4 mol L-1 indolebutyric acid; 4.89, 7.34, and 9.79 × 10-4 mol L-1 tryptophan; and a control with hydroprimed seeds. A negative control with nonprimed seeds was also evaluated. All priming agents diminished the effects of salinity on endogenous abscisic acid concentration in the salt-intolerant cultivar. Grain yield was positively correlated with net CO2 assimilation rate and endogenous indoleacetic acid concentration, and it was negatively correlated with abscisic acid and free polyamine concentrations. In general, the priming treatment with tryptophan at 4.89 × 10-4 mol L-1 was the most effective in minimizing yield losses and reductions in net CO2 assimilation rate, under salt stress conditions. Hormonal homeostasis increases net CO2 assimilation rate and confers tolerance to salinity on spring wheat.

Tolerance to preharvest sprouting and yield of wheat genotypes from different breeding programs

Abstract:The objective of this work was to characterize the performance of elite wheat genotypes from different Brazilian breeding programs for traits associated with grain yield and preharvest sprouting. The study was conducted in 2010 and 2011 in the municipality of Capão do Leão, in the state of Rio Grande do Sul, Brazil, in a randomized complete block design with three replicates. Thirty-three wheat genotypes were evaluated for traits related to preharvest sprouting and grain yield. The estimate of genetic distance was used to predict potential combinations for selection of plants with high grain yield and tolerance to preharvest sprouting. The combined analysis of sprouted grains and falling number shows that the TBIO Alvorada, TBIO Mestre, Frontana, Fundacep Raízes, Fundacep Cristalino, and BRS Guamirim genotypes are tolerant to preharvest sprouting. Combinations of TBIO Alvorada and TBIO Mestre with Fundacep Cristalino show high potential for recovering superior genotypes for high grain yield and tolerance to preharvest sprouting.

Two distinct plant respiratory physiotypes might exist which correspond to fast-growing and slow-growing species

The origin of the carbon atoms in CO2 respired by leaves in the dark of several plant species has been studied using 13C/12C stable isotopes. This study was conducted using an open gas exchange system for isotope labeling that was coupled to an elemental analyser and further linked to an isotope ratio mass spectrometer (EA-IRMS) or coupled to a gas chromatography-combustion-isotope ratio mass spectrometer (GC-C-IRMS). We demonstrate here that the carbon, which is recently assimilated during photosynthesis, accounts for nearly ca. 50% of the carbon in the CO2 lost through dark respiration after illumination in fast-growing and cultivated plants and trees and, accounts for only ca. 10% in slow-growing plants. Moreover, our study shows that fast- growing plants, which had the largest percentages of newly fixed carbon of leaf-respired CO2 , were also those with the largest shoot/root ratios, whereas slow-growing plants showed the lowest shoot/root values.

Prediction of crude protein and classification of the growth stage of wheat plant samples from NIR spectra

Near-infrared spectroscopy (NIRS) was used to analyse the crude protein content of dried and milled samples of wheat and to discriminate samples according to their stage of growth. A calibration set of 72 samples from three growth stages of wheat (tillering, heading and harvest) and a validation set of 28 samples was collected for this purpose. Principal components analysis (PCA) of the calibration set discriminated groups of samples according to the growth stage of the wheat. Based on these differences, a classification procedure (SIMCA) showed a very accurate classification of the validation set samples : all of them were successfully classified in each group using this procedure when both the residual and the leverage were used in the classification criteria. Looking only at the residuals all the samples were also correctly classified except one of tillering stage that was assigned to both tillering and heading stages. Finally, the determination of the crude protein content of these samples was considered in two ways: building up a global model for all the growth stages, and building up local models for each stage, separately. The best prediction results for crude protein were obtained using a global model for samples in the two first growth stages (tillering and heading), and using a local model for the harvest stage samples.

Influence of "historic" photoperiod during stem elongation on the number of fertile florets in wheat

Extending the duration of the late reproductive phase in wheat has been proposed as a possible avenue to improve spike fertility. There is a positive correlation between the number of fertile florets and the duration of the stem elongation phase when this phase is varied by extended photoperiod. Photoperiod treatments imposed during the vegetative period also influence the duration of stem elongation. The present study analysed the effect of long photoperiod (19 h) of different duration (10, 12, 14, 18 or 22 d) imposed before the onset of stem elongation on floret fertility in wheat. It was found that the length of the stem elongation phase was modified by earlier ‘historic ’ photoperiod treatments imposed during previous phases. However, neither the number of fertile florets per spike nor the spikelet fertility was affected significantly by these historic treatments. The results of the study therefore showed that an increased duration of the late reproductive phase was ineffective in increasing the number of fertile florets, unless the length of that phase was directly altered by current photoperiod.

Quantitative developmental response to the length of exposure to long photoperiod in wheat and barley

The present study was designed to analyse the effect of the length of exposure to a long photoperiod imposed c. 3 weeks after sowing in spring wheat (cv. UQ189) and barley (cv. Arapiles) to (i) establish whether the response to the number of cycles of exposure is quantitative or qualitative, (ii) determine the existence of a commitment to particular stages well before the stage has been observable, and (iii) study the interrelationships between the effects on final leaf number and phyllochron when the stimulus is provided several days after seedling emergence. Both wheat and barley seemed to respond quantitatively to the number of long-day cycles they were exposed to. However, wheat showed a requirement of approximately 4 long-day cycles to be able to produce a significant response in time to heading. The barley cultivar used in the study was responsive to the minimum length of exposure. The response to extended photoperiod cycles during the stem elongation phase was due to the ‘ memory’ photoperiod effects being related, in the case of wheat, to the fact that the pre-terminal spikelet appearance phase saturated its photoperiod response well before that stage was reached. Therefore, the commitment to the terminal spikelet appearance in wheat may be reached well before this stage could be recognized. As the response in duration to heading exceeded that of the final leaf number, and the stem elongation phase responded to memory effects of photoperiod, the phyllochron of both cereals was responsive to the treatments accelerating the average phyllochron when exposed to longer periods of long days. The response in average phyllochron was due to a switch from bi-linear to linear models of leaf number v. time when the conditions were increasingly inductive, with the phyllochron of the initial (6–8) leaves being similar for all treatments (within each species), and from then on increased.

Effect of temperature and carpel size during pre-anthesis on potential grain weight in wheat

The effect of environmental conditions immediately before anthesis on potential grain weight was investigated in wheat at the experimental field of the Faculty of Agronomy (University of Buenos Aires, Argentina) during 1995 and 1996. Plants of two cultivars of wheat were grown in two environments (two contrasting sowing dates) to provide different background temperature conditions. In these environments, transparent boxes were installed covering the spikes in order to increase spike temperature for a short period (c. 6 days) immediately before anthesis, i.e. between ear emergence and anthesis. In both environments, transparent boxes increased mean temperatures by at least 3n8 mC. These increases were almost entirely due to the changes in maximum temperatures because minimum temperatures were little affected. Final grain weight was significantly reduced by higher temperature during the ear emergence–anthesis period. It is possible that this reduction could be mediated by the effect of the heat treatment on carpel weight at anthesis because a curvilinear association between final grain weight and carpel weight at anthesis was found. This curvilinear association may also indicate a threshold carpel weight for maximizing grain weight.

Shading effects on the yield of an Argentinian wheat cultivar

Shading treatments of 50% of the incident radiation were applied to the semidwarf wheat cultivar Leones INTA before and after anthesis in two field experiments in Argentina in 1987 and 1988. The treatments reduced biological (above-ground dry matter) yield, grain yield and number of grains/m2. Number of grains/m2 was closely and linearly correlated with ear dry weight at anthesis and with the photothermal quotient, calculated from 20 days before to 10 days after anthesis. Grain yield was sink limited, and the shading treatments reduced sink strength. The contribution of preanthesis assimilates to grain yield was smaller in the shaded crops than in the unshaded controls; in unshaded crops, almost 40% of grain yield was contributed by preanthesis assimilates whilst in preanthesis shaded crops this contribution was negligible. The proportion of preanthesis assimilates contributed to the grain was closely related to the decrease in stem dry weight during grain filling. The effects of shading on main stems and tillers were the same.

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 (22\12 mC, and 15\5 mC day\night temperatures, respectively), in growth chambers. The 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 the 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 to seed-grading size.

Sink limitations to yield in wheat : how could it be reduced?

Further genetic gains in wheat yield are required to match expected increases in demand. This may require the identification of physiological attributes able to produce such improvement, as well as the genetic bases controlling those traits in order to facilitate their manipulation. In the present paper, a theoretical framework of source and sink limitation to wheat yield is presented and the fine-tuning of crop development as an alternative for increasing yield potential is discussed. Following a top-down approach, most crop physiologists have agreed that the main attribute explaining past genetic gains in yield was harvest index (HI). By virtue of previous success, no further gains may be expected in HI and an alternative must be found. Using a bottom-up approach, the present paper firstly provides evidence on the generalized sink-limited condition of grain growth, determining that for further increases in yield potential, sink strength during grain filling has to be increased. The focus should be on further increasing grain number per m2, through fine-tuning pre-anthesis developmental patterns. The phase of rapid spike growth period (RSGP) is critical for grain number determination and increasing spike growth during pre-anthesis would result in an increased number of grains. This might be achieved by lengthening the duration of the phase (though without altering flowering time), as there is genotypic variation in the proportion of pre-anthesis time elapsed either before or after the onset of the stem elongation phase. Photoperiod sensitivity during RSGP could be then used as a genetic tool to further increase grain number, since slower development results in smoother floret development and more floret primordia achieve the fertile floret stage, able to produce a grain. Far less progress has been achieved on the genetic control of this attribute. None of the well-known major Ppd alleles seems to be consistently responsible for RSGP sensitivity. Alternatives for identifying the genetic factors responsible for this sensitivity (e.g. quantitative trait locus (QTL) identification in mapping populations) are being considered.