Environmental variables for modeling wheat yields in the southwest pampa region of Argentina

Two types of time scales – 10-day intervals (D) and phenological phases (P) – were applied to environmental variables for the development of statistical regression models relating to the southwest pampa region of Argentina, with the aim of detecting the effects of weather on wheat yields for the period 1977–1999. The parameters were grouped as meteorological and processed variables and indices. The processed variables used were total soil water availability (SWA) and the ratio of actual evapotranspiration to potential evapotranspiration (), obtained from a water-balance model in which the moisture anomaly index (Z) and the Palmer drought severity index (PDSI) were calculated according to Palmers model. For these parameters it was possible to establish the times of year and the phenological phases with the best correlation to grain yield. The regression equation for meteorological variables on a 10-day scale provides one of the best fits. Using mixed parameters, the two models, D and P, give rise to a standard error of estimate of approximately 200 kg ha^–1. Truncated models perform better on a P scale than on a D scale. The use of phenological stages improved yield assessment, particularly for those years with extreme meteorological conditions. The optimum models were tested and root-mean-square errors (RMSE) of 440 kg ha^–1 and 470 kg ha^–1 were obtained for P and D scales respectively.     

Evaluation of experimental designs and spatial analyses in wheat breeding trials

Thirty-three wheat breeding trials were conducted from 1994 to 1996 in the Northern Grains Region (QLD and Northern NSW) of Australia to evaluate the influence of experimental designs and spatial analyses on the estimation of genotype effects for yield and their impact on selection decisions. The relative efficiency of the alternative designs and analyses was best measured by the average standard error of difference between line means. Both more effective designs and spatial analyses significantly improved the efficiency relative to the randomised complete block model, with the preferred model (which combined the design information and spatial trends) giving an average relative efficiency of 138% over all 33 trials. When the Czekanowski similarity coefficient was used, none of the studied models were in full agreement with the randomised complete block model in the selection of the top lines. The agreement was influenced by selection proportions. Hence, the use of these methodologies can impact on the selection decisions in plant breeding. Received: 17 December 1998 / Accepted: 29 July 1999     

Alleviation of salt stress by plant growth regulators and IAA producing bacteria in wheat

The action of phytohormone producing bacteria and plant growth regulators on germination and seedling growth of wheat under saline conditions were studied. Seed dormancy enforced by salinity (100 mM NaCl) was substantially alleviated and the germination was promoted by gibberellin, auxin, zeatin, and ethephon from 54 to 97%. The IAA producing bacterial strains Pseudomonas aureantiaca TSAU22, Pseudomonas extremorientalis TSAU6 and Pseudomonas extremorientalis TSAU20 significantly increased seedling root growth up to 25% in non-salinated conditions and up to 52% at 100 mM NaCl, compared to control plants. It is concluded that growth regulators considerably alleviated salinity-induced dormancy of wheat seeds. The facts mentioned above make it possible to recommend root colonizing bacteria that produce phytohormone to alleviate salt stress of wheat grown under conditions of soil salinity.     

Characterization of the caryopsis of common wheat varieties and F2 generation hybrids by means of multivariate analysis

Summary Nineteen parameters of common wheat kernels were investigated by the multivariate procedure. A relationship between the DBC parameter and both specific gravity and kernel filling was found. In some populations an interdependence of the DBC parameter and the subaleurone endosperm thickness was found. In the analysis of principal components the DBC parameter was represented mostly by particular component. Significant dependences were found between the dimensions as well as the weight of the caryopsis and some dimensions of the crease and endosperm cavity. The dendrite constructed on the basis of the calculated Mahalanobis's generalized distances matrix represents the near affinity of reciprocal hybrids or pure lines originating from a single cultivar as well as hybrids and their parental forms.     

Using vegetation indices derived from conventional digital cameras as selection criteria for wheat breeding in water-limited environments

The ability to assess green biomass is of particular interest in a number of wheat breeding environments. However, the measurement of this and similar traits is either tedious and time-consuming or requires the use of expensive, sophisticated equipment, such as field-based spectroradiometers to measure vegetation indices (VIs). Here, conventional digital cameras are proposed as affordable and easy-to-use tools for gathering field data in wheat breeding programmes. Using appropriate software, a large set of images can be automatically processed to calculate a number of VIs, based on the performance of simple colour operations on each picture. The purpose of this study was to identify a set of picture-derived vegetation indices (picVIs) and to evaluate their performance in durum wheat trials growing under rainfed and supplementary irrigation conditions. Here, zenithal pictures of each plot were obtained roughly 2 weeks after anthesis, and the picVIs that were calculated were compared with the normalised difference vegetation index (NDVI), an index derived from spectroradiometrical measurements, and with the grain yield (GY) from the same plots. The picVIs that performed best were the Hue, CIE-Lab a* and CIE-Luv u* components of the average colour of each picture, the relative green area (GA) and the 'greener area', similar to GA but excluding the more yellowish-green pixels. Our results showed a high correlation between all these picVIs and the NDVI. Moreover, in rainfed conditions, each picVI provided an estimation of GY similar to or slightly better than that provided by the NDVI. However, in irrigated conditions during anthesis, neither these picVIs nor the NDVI provided a good estimation of GY, apparently because of the saturation of the VI response in conditions of complete soil cover and high plant density.     

Effects of plant breeding and selection on yields and nitrogen fixation in soybeans under two soil nitrogen regimes

Summary Soybeans (Glycine max (L.) Merr.) have a high N requirement which is fulfilled by soil N uptake and N₂-fixation. This study was concerned with the effects of past yield selection on N₂-fixation in soybeans.The soybean cultivars, Lincoln, Shelby, and Williams, which represent successive improvements in the Lincoln germplasm, and a non-nodulating control were planted in a soil containing¹⁵N labelled organic matter. Two replications occurred on soil previously cropped to alfalfa and two on soil previously cropped to soybeans. Plants were harvested at five growth stages and leaf area, plant weight, total N, and atom percent¹⁵N were determined. Mature grain was harvested and yield components were also determined, as well as the total N and¹⁵N content.Cultivar differences in total dry matter were only evident at physiological maturity, when Williams contained the greatest dry matter. Williams exhibited the longest period of seed formation and seed fill and also had the highest grain yield which resulted from a larger weight per seed.The N content of the cultivars did not vary until physiological maturity when Williams contained the highest percent N. The quantity of N fixed at physiological maturity was highest for Williams and lowest for Lincoln. Fixed N contained in the harvested grain was greater for Williams than for the other two cultivars. The fraction of the total plant N derived from fixation was not greatly affected by cultivar and all cultivars acquired an average of 50% of their total N through N₂-fixation.Previous cropping history greatly affected the quantity of N fixed and the fraction of the total plant N derived from fixation. Soybeans following soybeans were more dependent upon N₂-fixation than soybeans following alfalfa with the former deriving 65% of the total plant N from fixation and the latter only 32%. These soybean cultivars apparently utilized soil N first and then used N₂-fixation to satisfy their N requirement.The past selection for higher yield has resulted in soybean cultivars with improved capacities to fix atmospheric N₂ and an improved ability to take up available soil N.     

Effects of applying stem-shortening plant growth regulators to leaves on root elongation by seedlings of wheat, oat and barley: mediation by ethylene

Several plant growth regulators (PGRs) commonly used in practicalfarming to restrict shoot height and control lodging were examined for theirimpact on root growth in naturally short or tall cultivars of barley (cvs.Kymppi and Saana), oat (cvs. Veli and Pal), and wheat (cvs. Mahti and Tjalve).The possible involvement of ethylene in the responses was also examined. Shootswere sprayed at the two-leaf stage with the gibberellin biosynthesis inhibitorsCycocel (chlormequat chloride) (CCC) or Moddus (Trinexapac-ethyl) (TE), or withthe ethylene-releasing agent Cerone (ethephon) (ETH) at 0, 0.1, 1, 10 or 50times the recommended agricultural rate (RR). Root elongation and ethyleneproduction by roots or shoots were unaffected by CCC at all application ratesorby TE at ×0.1 or ×1.0 RR. At ×10 and ×50 RR, TE wasinhibitory to root extension but did not increase ethylene biosynthesis bytheseroots or the shoots. ETH at ×0.1 or ×1.0 RR did not affect rootextension or ethylene production in roots or shoots. At all higher rates ofapplication ETH stimulated ethylene production strongly in shoots and roots ofall three species, while root elongation was retarded severely in barley,moderately in oat and only slightly in wheat. These differences in elongationresponse are attributed to differences in sensitivity to ethylene released byethephon. Accordingly, root elongation in wheat was only slightly affected whenethylene gas was supplied at concentrations up to 100 ppm for 3d. In contrast, root elongation in barley was strongly inhibitedbyethylene, with oat demonstrating an intermediate responsiveness.     

Prediction of near-term climate change impacts on UK wheat quality and the potential for adaptation through plant breeding

Wheat is a major crop worldwide, mainly cultivated for human consumption and animal feed. Grain quality is paramount in determining its value and downstream use. While we know that climate change threatens global crop yields, a better understanding of impacts on wheat end-use quality is also critical. Combining quantitative genetics with climate model outputs, we investigated UK-wide trends in genotypic adaptation for wheat quality traits. In our approach, we augmented genomic prediction models with environmental characterisation of field trials to predict trait values and climate effects in historical field trial data between 2001 and 2020. Addition of environmental covariates, such as temperature and rainfall, successfully enabled prediction of genotype by environment interactions (G × E), and increased prediction accuracy of most traits for new genotypes in new year cross validation. We then extended predictions from these models to much larger numbers of simulated environments using climate scenarios projected under Representative Concentration Pathways 8.5 for 2050–2069. We found geographically varying climate change impacts on wheat quality due to contrasting associations between specific weather covariables and quality traits across the UK. Notably, negative impacts on quality traits were predicted in the East of the UK due to increased summer temperatures while the climate in the North and South-west may become more favourable with increased summer temperatures. Furthermore, by projecting 167,040 simulated future genotype–environment combinations, we found only limited potential for breeding to exploit predictable G × E to mitigate year-to-year environmental variability for most traits except Hagberg falling number. This suggests low adaptability of current UK wheat germplasm across future UK climates. More generally, approaches demonstrated here will be critical to enable adaptation of global crops to near-term climate change.     

Use of multivariate analyses to investigate the contribution of metal pollution to diatom species composition: search for the most appropriate cases and explanatory variables

The aim of this study was to elucidate how the spatial scale and the set of variables included influence our ability to detect the effects of different types of pollution on the biota. Using variance partitioning analysis, we assessed the individual importance of a set of environmental factors (eutrophication and organic pollution) versus metal level pollution on the community structure of diatom assemblages at different spatial scales. At regional scale, environmental factors did not explain more of the variance compared to the watershed study. The results of the watershed scale field survey indicate that diatom community composition was influenced by low metal concentrations, but this pattern was only observed by the inclusion of biofilm metal concentration data. We recommend the analysis of metal traces in the water phase and the biota (fluvial biofilms) as well as the use of the Diffusive Gradient in Thin films (DGT) technique to characterize low metal level pollution in freshwater systems. Handling editor: Judit Padisák     

Influence of ethanol concentration of extraction solvent on metabolite profiling for Salviae Miltiorrhizae Radix et Rhizoma extract by 1H NMR spectroscopy and multivariate data analysis

Salviae Miltiorrhizae Radix et Rhizoma (Danshen in China) and its related preparations are widely used in clinical practice due to its high medicinal value. In recent years, ¹H NMR technology has made great progress and demonstrated its unique advantages in the field of botanical metabolomics. In this study, ¹H NMR-based metabolomics was used to investigate the dissolution of various metabolites in Danshen as a function of ethanol concentration. ¹H NMR spectroscopy of Danshen extract identified 28 metabolites including 6 sugars, 11 amino acids, 3 organic acids, 4 salvianolic acids, and 4 tanshinones. Multivariate statistical analysis was used to classify and compare various Danshen extracts. PCA and HCA were used to obtain a global overview of the similarity in the samples and two-class OPLS-DA models were established for identifying characteristic metabolites. Then, ¹H-qNMR method was used to estimate the concentration of 22 metabolites, which is helpful to further describe the changes in metabolite ratios of various Danshen extracts. The result of this study laid the foundation for further biological activity research, and also provided an important reference for subsequent process research and quality control of Danshen related preparations.     

Genotype x strain interactions for resistance to Fusarium head blight caused by Fusarium culmorum in winter wheat

Summary In 3 consecutive years, a set of 17 winter wheat genotypes, representing a wide range of Fusarium head blight resistance, was inoculated with four strains of Fusarium culmorum. Fusarium head blight ratings were analyzed. The interaction between genotypes, strains, and years was described using a Finlay-Wilkinson model and an Additive Main effects and Multiplicative Interaction effects (AMMI) model. The interaction consisted primarily of a divergence of genotypical responses with increasing disease pressure, modified by genotype specific reactions in certain years. The divergence was mainly caused by one very pathogenic strain. The Fusarium head blight resistance in this study can be described as horizontal resistance in terms of Vanderplank, with the exception of three genotypes selected from one particular cross that showed a strain-year combination dependent resistance which was ineffective in 1 year.     

Assessment of 1H NMR spectroscopy and multivariate analysis as a technique for metabolite fingerprinting of Arabidopsis thaliana

An approach to metabolite fingerprinting of crude plant extracts that utilizes 1H nuclear magnetic resonance (NMR) spectroscopy and multivariate statistics has been tested. Using ecotypes of Arabidopsis thaliana as experimental material, a method has been developed for the rapid analysis of unfractionated polar plant extracts, enabling the creation of reproducible metabolite fingerprints. These fingerprints could be readily stored and compared by a variety of chemometric methods. Comparison by principal component analysis using SIMCA-P allowed the generation of residual NMR spectra of the compounds that contributed significantly to the differences between samples. From these plots, conclusions were drawn with respect to the identity and relative levels of metabolites differing between samples.     

Improved tissue culture response of an elite maize inbred through backcross breeding,and identification of chromosomal regions important for regeneration by RFLP analysis

Summary The frequency of initiation of friable, embryogenic callus from immature embryos of the elite maize inbred line B73 was increased dramatically by introgression of chromosomal segments from the inbred line A188 through classical backcross breeding. Less than 0.2% of the immature B73 embryos tested (5 of 3,710) formed embryogenic callus. The breeding scheme consisted of six generations of backcrossing to B73 with selection at each generation for high frequency initiation of embryogenic cultures. BC₆ individuals were selfed for four generations to select homozygous lines. The average embryogenic culture initiation frequency increased to 46% (256/561). Nearly all (91%) of the embryos from one BC₆ S₄ plant formed embryogenic cultures. RFLP analysis was used to determine the locations and effects of the introgressed A188 chromosomal segments. Five segments were retained through at least the fifth backcross generation. The hypothesis that one or more of these five regions contains genes controlling somatic embryogenesis in maize was tested using an F₂ population of the cross A188 X Mo17. A set of five DNA markers (three of them linked) explained 82% of the observed phenotypic variance for percentage of immature embryos forming embryognic callus. Four of the five markers were located in or near introgressed A188 chromosome segments.The region marked by probe c595 on the long arm of chromosome 9 was highly associated with several measures of in vitro culture response (percent embryogenic embryos, plants per embryo, and plants per embryogenic embryo). We propose that there is a major gene (or genes) in this region in A188 that promotes embryogenic callus initiation and plant regeneration in B73, Mo17, and probably many other recalcitrant inbred lines of maize.     

Use of tuber progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents, chosen for their fertility, from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. The progenies were grown in randomised complete block trials with two replicates at a high-grade seed site from 1994 to 1996 inclusive and at a ware site in 1995 and 1996. The parents were included in the ware trials. Tubers were assessed for visual preference in all trials and for fry colour at both sites in 1996. Emergence and maturity were recorded in the ware trials and the tubers were assessed for yield, dry matter, size, appearance (regularity of shape), scab, uniformity, sprouting in store and keeping quality. There were very few growth cracks and very few internal defects. No reciprocal differences were found. Inbreeding depression was marked for emergence, yield, tuber size and appearance, and visual preference. In contrast, the selfs had a lighter fry colour than the parents and F₁s. Combining-ability analysis (selfs omitted) identified fry colour, emergence, maturity, yield, dry matter and sprouting resistance as traits for which the GCA (general combining ability) variance and narrow-sense heritability were high enough for good progress from full-sib family selection. Correlations between GCAs for pairs of traits were examined, including those from previously published seedling progeny tests. For fry colour, an unfavourable correlation with low yield (r = 0.596) was compensated by a favourable one with high dry matter content (r = 0.652), whereas unfavourable ones between foliage and tuber blight resistance and sprouting susceptibility (r = 0.578 and 0.596) were identified for monitoring. Clones with high GCAs were identified for use as parents in future breeding and the extent to which GCAs could be predicted from the parents, and the offspring means from the midparent means, was determined by regression and correlation analysis. The offspring-midparent regression was highest for fry colour, followed by dry matter, emergence and sprouting. Values were lower for scab due to environmental variation; for maturity, yield and tuber size due to SCA (specific combining ability); and for visual preference due to both factors. The implications for a breeding strategy are discussed. Received: 28 November 1998 / Accepted: 19 December 1998     

Use of seedling progeny tests for genetical studies as part of a potato (Solanum tuberosum subsp. tuberosum) breeding programme

A diallel set of crosses, including selfs and some reciprocal crosses, was made between 15 parents chosen for their male fertility from those included in a tetraploid potato (Solanum tuberosum subsp. tuberosum) breeding programme at the Scottish Crop Research Institute. Seedling progeny tests were used to evaluate the progenies for non-race-specific resistance to late blight (Phytophthora infestans) in both foliage and tubers, quantitative resistance to the white potato cystnematode (PCN) (Globodera pallida) and the commercial worth of their tubers as judged by breeders' visual preference. No reciprocal differences were found. Comparisons of the selfs and crosses revealed inbreeding depression for breeders' preference, which varied among the parents from negligible to severe, whilst there were also statistically significant differences for foliage and tuber blight, but not for PCN. When the selfs were omitted from the combining ability analyses, large differences in general combining ability (GCA) were found for all four traits, and smaller differences in specific combining ability for tuber blight and breeders' preference. The only statistically significant correlation between GCAs for different traits was a favourable one of r = 0.56 between foliage and tuber resistance to late blight. It was concluded that prospects were good for simultaneously improving all four traits by multitrait genotypic recurrent selection.     

EPR spectroscopy as a tool for investigation of differences in radical status in wheat plants of various tolerances to osmotic stress induced by NaCl and PEG-treatment

Two kinds of wheat genotypes with different tolerance to osmotic stress (NaCl and PEG-treatment) were investigated with biochemical analyses, including the measurements of total antioxidant capacity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity, reducing power and starch content. The results were compared with electron paramagnetic resonance (EPR) data concerning the nature and amounts of stable long lived radicals present in the control and stressed plants. In addition, the changes in manganese content upon stress conditions were monitored. Different mechanisms of protection against PEG stress in sensitive and tolerant wheat genotypes were postulated. In sensitive genotypes, electrons were created in excess in stress conditions, and were stabilized by polysaccharide molecules, whereas in tolerant genotypes, protection by antioxidants dominated. Moreover, the quinone–semiquinone balance shifted towards semiquinone, which became the place of electron trapping. NaCl-treatment yielded significant effects mainly in sensitive genotypes and was connected with the changes of water structure, leading to inactivation of reactive oxygen species by water molecules.     

Polyamines as biomarkers for plant regeneration capacity: improvement of regeneration by modulation of polyamine metabolism in different genotypes of indica rice

The importance of cellular polyamine (PA) levels and the ratio of putrescine (Put) to spermidine (Spd) for plant regeneration ability via somatic embryogenesis in several commercially grown indica rice varieties is reported here. The genotypes namely NDR-624, IR-20, IR-36, BJ-1 (having Put:Spd ratio2.3) showed superior plant regeneration while KL, PB-1 and TN-1 (having Put:Spd ratio3.8) showed moderate plant regeneration ability. The genotypes namely HS, Bindli, DV-85, ACB-72, IR-64 and IR-72 (having Put:Spd ratio5.0) showed poor plant regeneration ability. In contrast KH-7 (Put:Spd ratio10.0) showed no response at all. Favorable modification of cellular PA titers and their Put:Spd ratio by the addition of exogenous PAs (Put, Spd) or their biosynthesis inhibitor, difluoromethylarginine (DFMA) led to the induction/promotion of plant regeneration in poorly responding genotypes. These results showed a close relationship between cellular PA levels and their Put:Spd ratio with in vitro morphogenetic capacity in indica rice and suggest that the cellular PAs and Put:Spd ratios are important determinants (biomarkers) of plant regeneration ability in indica rice, and the improvement/induction of plant regeneration in morphogenetically poor and recalcitrant species could be achieved by modulating PA metabolism.     

Sex‐biased oviposition by a nursery pollinator on a gynodioecious host plant: Implications for breeding system evolution and evolution of mutualism

Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen‐bearing sex, with sex‐specific fitness effects that can affect breeding system evolution. Nursery pollination, where adult insects pollinate flowers but their larvae feed on plant reproductive tissues, is a model for understanding mutualism evolution but could also yield insights into plant breeding system evolution. We studied a recently established nursery pollination interaction between native Hadena ectypa moths and introduced gynodioecious Silene vulgaris plants in North America to assess whether oviposition was biased toward females or hermaphrodites, which traits were associated with oviposition, and the effect of oviposition on host plant fitness. Oviposition was hermaphrodite‐biased and associated with deeper flowers and more stems. Sexual dimorphism in flower depth, a trait also associated with oviposition on the native host plant (Silene stellata), explained the hermaphrodite bias. Egg‐receiving plants experienced more fruit predation than plants that received no eggs, but relatively few fruits were lost, and egg receipt did not significantly alter total fruit production at the plant level. Oviposition did not enhance pollination; egg‐receiving flowers usually failed to expand and produce seeds. Together, our results suggest that H. ectypa oviposition does not exert a large fitness cost on host plants, sex‐biased interactions can emerge from preferences developed on a hermaphroditic host species, and new nursery pollination interactions can arise as negative or neutral rather than as mutualistic for the plant.