The virulence of Finnish Pyrenophora teres f. teres isolates and its implications for resistance breeding

In Finland, barley, Hordeum vulgare L., covers 50 % of the total acreage devoted to cereal cultivation. The most common disease of barley in Finland is net blotch, a foliar disease caused by the ascomycete Pyrenophora teres Drechsler. Disease resistance based on plant genes is an environmentally friendly and economical way to manage plant diseases caused by biotic stresses. Development of a disease resistance breeding programme is dependent on knowledge of the pathogen. In addition to information on the epidemiology and virulence of a pathogen, knowledge on how the pathogen evolves and the nature of the risks that might arise in the future are essential issues that need to be taken into account to achieve the final breeding aims. The main objectives of this study were to establish reliable and efficient testing methods for Pyrenophora teres f. teres virulence screening, and to understand the role of virulence of P. teres f. teres in Finland from a disease resistance breeding point of view. The virulence of P. teres was studied by testing 239 Finnish P. teres f. teres isolates collected between 1994 2007 originating from 19 locations, and 200 P. teres progeny isolates originating from artificially produced P. teres matings. According to the results of this study, screening for P. teres f. teres isolates on barley seedlings under greenhouse conditions is a feasible and cost efficient method to describe the virulence spectrum of the pathogen. Inoculum concentration and the seedling leaf used to gauge virulence had significant effects. Barley grain size, morphological traits of P. teres isolates, spore production and growth rate on agar did not affect the expression of virulence. A common barley differential set to characterize the P. teres virulence was developed and is recommended to be used globally. The virulence spectrum of Finnish P. teres f. teres isolates collected in 1994-2007 was constant both within and between the years. The results indicated differences in the pathogen s aggressiveness and in barley genotypes resistance. However, differences in virulence were rarely significant. Unlike in laboratory conditions, no indications of changes in virulence caused by the sexual reproduction have been observed in Finnish barley fields. In Finland, durable net blotch resistance has been achieved by introducing resistance from other barley varieties using traditional crossing methods, including wide crossing, and testing the breeding material at early generations at several sites under natural infection pressure. Novel resistance is available, which is recommended to minimize the risk of selection of virulent isolates and breakdown of currently deployed resistance.

Current and emerging screening methods to identify post-head-emergence frost adaptation in wheat and barley

Cereal crops can suffer substantial damage if frosts occur at heading. Identification of post-head-emergence frost (PHEF) resistance in cereals poses a number of unique and difficult challenges. Many decades of research have failed to identify genotypes with PHEF resistance that could offer economically significant benefit to growers. Research and breeding gains have been limited by the available screening systems. Using traditional frost screening systems, genotypes that escape frost injury in trials due to spatial temperature differences and/or small differences in phenology can be misidentified as resistant. We believe that by improving techniques to minimize frost escapes, such ofalse-positive' results can be confidently identified and eliminated. Artificial freezing chambers or manipulated natural frost treatments offer many potential advantages but are not yet at the stage where they can be reliably used for frost screening in breeding programmes. Here we describe the development of a novel photoperiod gradient method (PGM) that facilitates screening of genotypes of different phenology under natural field frosts at matched developmental stages. By identifying frost escapes and increasing the efficiency of field screening, the PGM ensures that research effort can be focused on finding genotypes with improved PHEF resistance. To maximize the likelihood of identifying PHEF resistance, we propose that the PGM form part of an integrated strategy to (i) source germplasm;(ii) facilitate high throughput screening; and (iii) permit detailed validation. PGM may also be useful in other studies where either a range of developmental stages and/or synchronized development are desired.

Fusarium graminearum and Fusarium pseudograminearum caused the 2010 head blight epidemics in Australia

Wheat crops in southeast Queensland (Qld) and northern New South Wales (NSW) were infected with fusarium head blight (FHB)-like symptoms during the 201011 wheat growing season. Wheat crops in this region were surveyed at soft dough or early maturity stage to determine the distribution, severity, aetiology and toxigenicity of FHB. FHB was widespread on bread wheat and durum, and Fusarium graminearum and/or F.pseudograminearum were diagnosed from 42 of the 44 sites using species-specific PCR primers directly on spikelets or from monoconidial cultures obtained from spikelets. Stem base browning due to crown rot (CR) was also evident in some samples from both states. The overall FHB and CR severity was higher for NSW than Qld. Deoxynivalenol (DON) concentration of immature grains was more than 1 mg kg-1 in samples from 11 Qld and 14 NSW sites, but only 13 of 498 mature grain samples sourced from the affected areas had more than 1 mg kg-1 DON. DON concentration in straw also exceeded 1 mg kg-1 in eight Qld and all but one NSW sites but this was not linked to DON concentration of immature grains. The proportion of spikelets with positive diagnosis for F.graminearum and/or F.pseudograminearum and weather-related factors influenced DON levels in immature grains. The average monthly rainfall for AugustNovember during crop anthesis and maturation exceeded the long-term monthly average by 10150%. Weather played a critical role in FHB epidemics for Qld sites but this was not apparent for the NSW sites, as weather was generally favourable at all sites.

Agronomic challenges for organic crop husbandry

With respect to resource management and environmental impact, organic farming offers rationales for agricultural sustainability. However, agronomic productivity is usually higher with conventional farming. This work aimed at investigating two factors of major importance for the agronomic productivity of organic crop husbandry, nitrogen (N) supply through symbiotic N fixation (SNF) and weed occurrence. Perennial red clover-grass leys and spring cereal crops subjected to regular agricultural practices were studied on 34 organic farms located in the southern and the north-western coastal regions of Finland. Herbage growth, clover content as a proportion of the ley and extent of SNF in perennial leys, and the occurrence of weed species and weed-crop competition in spring cereal stands were related to climate conditions, soil properties, and management measures. The herbage accumulated from the first and the second cut of one- and two-year-old leys averaged 7.5 t DM ha-1 (SD ± 1.7 t DM ha-1); the clover content averaged 43.9% (SD ± 18.8%). Along with the clover content, herbage production decreased with ley age. Radiation use efficiency (RUE) correlated positively with clover proportion but despite low clover contents, three-year-old leys were still productive with regard to RUE. SNF in the accumulated annual growth of one- and two-year-old leys averaged 247.5 kg N ha-1 yr-1 (SD ± 114.4 kg N ha-1 yr-1). It was supposed that if red clover-grass leys constituted 40% of the rotation, then the mean N supply by SNF would be able to sustain two or three succeeding cereal crops (green manure and forage ley, respectively), yielding 3.0 to 4.0 t grain ha-1. Being a function of clover biomass, the SNF increased from the first to the second cut and thereafter declined with ley age. Coefficients of variation of clover contents (and SNF) between and within fields were around 50%, which was about twice as high as those of herbage production. The lower were the clover contents, the higher were the within-field variations of clover as a proportion of the ley. Low clover contents in one-year-old leys and increasing variability with ley age suggested that red clover growth was limited by poor establishment and poor overwintering. The proportions of clover in leys were lower and their variability was higher in the northwest than in the south. Soil properties, primarily texture and structure, had a major impact on clover proportion and herbage production, which largely explained regional differences in ley growth. Within-field variability of soil properties can be amended through site-specific measures, including drainage, liming, and applications of organic manures and mineral fertilizers. Overwintering and the persistence of leys can be improved by the choice of winter-hardy varieties, careful establishment and the appropriate harvest regime. Mean grain yields of spring cereal crops amounted to 3.2 t ha-1 in the south and 3.6 t ha-1 in the northwest. At 570 and 565 m-2 for the south and northwest respectively, mean weed densities did not differ between the regions, whereas the respective mean weed biomass of 697 and 1594 kg dry weight ha-1, respectively did differ. Weed abundance varied remarkably between single fields. The number of weed species was higher in the south than in the northwest. For example, Fumaria officinalis and Lamium spp. were found only in the south. Frequencies and abundances of Lapsana communis, Myosotis arvensis, Polygonum aviculare, Tripleurospermum inodorum, and Vicia spp. were higher in the south, whereas those of Elymus repens, Persicaria spp. and Spergula arvensis were higher in the northwest. The number of years since conversion to organic farming, i.e. long-term management, was one of the variables that explained the abundance of single weed species. E. repens was the weed species whose biomass increased most with the duration of organic farming. Another significant variable was crop biomass, which was affected by short-term management. The presence of different weed species was related to the duration of organic farming and to low crop yield. This finding demonstrated that it was not the organic farming regime per se, which resulted in high weed infestation and low yielding crops, but failures in the understanding and the management of organic farming systems. Successful weed control relies on farm- and field-specific long- and short-term management approaches. The agronomic productivity of ley and spring cereal crops managed by full-time farmers with an interest in organic farming was on the same level as of the mean for conventional farming. Given the many options for further improvements of the agronomic performance of organic arable systems, organic farming offers foundations for the development of sustainable agriculture. The main threat to the sustainability of farming in Finland, both conventional and organic, is the spatial separation of crop production and animal husbandry by region, along with the simplification of associated crop rotations.

Ode to a Skylark: Agricultural intensification and farmland birds in the Baltic region

Intensification of agricultural land-use has been was shown to be the key reason behind declines in wildlife species associated with farmland. Accession to the European Union is regarded as a potential threat to the farmland biota of its new member states. In my thesis I looked at scenarios of agricultural development across the Baltic states of Estonia, Latvia and Lithuania, and the ways they are seen to affect farmed environments as a habitat of farmland bird species. I looked at the effects of major farmed habitats across the region, and assessed the role of spatial organisation of farmed habitats. I also evaluated the direction and magnitude of changes in bird communities following progression of farmland land-use from a relatively less intensive to the most intensive type within each country. Different aspects of the structural complexity of farmland were critical for supporting farmland birds. There was a clear indication that the more intensively farmed areas across the region provided habitat for fewer bird species and individuals, and intensification of field management was reflected in a tangible decrease in farmland bird abundance. The second part of the thesis, based on interviews in Estonia and Finland, is devoted to farmers interest in and knowledge of farmland wildlife, their understanding of the concept of biodiversity, and awareness of causes behind species declines. I examined the relationship between farmers interest and their willingness to undertake practices favouring farmland wildlife. Many farmers viewed biodiversity from a narrow perspective. In Finland farmers expressed higher concern about the decline in common farmland species than in Estonia. In both countries farmers rated intensification of agriculture as the major driving force behind declines. The expressed interest in wildlife positively correlated with willingness to undertake wildlife-friendly measures. Only farmers with agri-environment contracts targeted specifically at biodiversity were more knowledgeable about practical on-farm activities favouring wildlife, and were more willing to employ them that the rest. The results suggest that, by contributing to simplification of the farmland structure, homogenisation of crops, and increase in intensity of field use, EU agricultural policies will have a detrimental effect on farmland bird populations in Eastern Europe. Farmers are on the whole positive to the idea of supporting wildlife on their farms, and are concerned about declines, but they require payments to offset their income loss and extra work. I propose ways of further improving and better targeting of the agri-environment schemes in the region. I argue that with a foreseen tripling of cereal yields across the region, the EU Council s target of halting biodiversity decline in the EU by 2010 may not be realistic unless considerable improvements are made in conservation safeguards within the EU agricultural policy for the region.

Nitrogen dynamics and nitrogen use efficiency of spring cereals under Finnish growing conditions

Nitrogen (N) is one of the main inputs in cereal cultivation and as more than half of the arable land in Finland is used for cereal production, N has contributed substantially to agricultural pollution through fertilizer leaching and runoff. Based on this global phenomenon, the European Community has launched several directives to reduce agricultural emissions to the environment. Trough such measures, and by using economic incentives, it is expected that northern European agricultural practices will, in the future, include reduced N fertilizer application rates. Reduced use of N fertilizer is likely to decrease both production costs and pollution, but could also result in reduced yields and quality if crops experience temporary N deficiency. Therefore, more efficient N use in cereal production, to minimize pollution risks and maximize farmer income, represents a current challenge for agronomic research in the northern growing areas. The main objective of this study was to determine the differences in nitrogen use efficiency (NUE) among spring cereals grown in Finland. Additional aims were to characterize the multiple roles of NUE by analysing the extent of variation in NUE and its component traits among different cultivars, and to understand how other physiological traits, especially radiation use efficiency (RUE) and light interception, affect and interact with the main components of NUE and contribute to differences among cultivars. This study included cultivars of barley (Hordeum vulgare L.), oat (Avena sativa L.) and wheat (Triticum aestivum L.). Field experiments were conducted between 2001 and 2004 at Jokioinen, in Finland. To determine differences in NUE among cultivars and gauge the achievements of plant breeding in NUE, 17-18 cultivars of each of the three cereal species released between 1909 and 2002 were studied. Responses to nitrogen of landraces, old cultivars and modern cultivars of each cereal species were evaluated under two N regimes (0 and 90 kg N ha-1). Results of the study revealed that modern wheat, oat and barley cultivars had similar NUE values under Finnish growing conditions and only results from a wider range of cultivars indicated that wheat cultivars could have lower NUE than the other species. There was a clear relationship between nitrogen uptake efficiency (UPE) and NUE in all species whereas nitrogen utilization efficiency (UTE) had a strong positive relationship with NUE only for oat. UTE was clearly lower in wheat than in other species. Other traits related to N translocation indicated that wheat also had a lower harvest index, nitrogen harvest index and nitrogen remobilisation efficiency and therefore its N translocation efficiency was confirmed to be very low. On the basis of these results there appears to be potential and also a need for improvement in NUE. These results may help understand the underlying physiological differences in NUE and could help to identify alternative production options, such as the different roles that species can play in crop rotations designed to meet the demands of modern agricultural practices.

Structural analyses of (1->3),(1->4)-β-D-glucan of oats and barley

The structures of (1→3),(1→4)-β-D-glucans of oat bran, whole-grain oats and barley and processed foods were analysed. Various methods of hydrolysis of β-glucan, the content of insoluble fibre of whole grains of oats and barley and the solution behaviour of oat and barley β-glucans were studied. The isolated soluble β-glucans of oat bran and whole-grain oats and barley were hydrolysed with lichenase, an enzyme specific for (1→3),(1→4)-β-D-β-glucans. The amounts of oligosaccharides produced from bran were analysed with capillary electrophoresis and those from whole-grains with high-performance anion-exchange chromatography with pulse-amperometric detection. The main products were 3-O-β-cellobiosyl-D-glucose and 3-O-β-cellotriosyl-D-glucose, the oligosaccharides which have a degree of polymerisation denoted by DP3 and DP4. Small differences were detected between soluble and insoluble β-glucans and also between β-glucans of oats and barley. These differences can only be seen in the DP3:DP4 ratio which was higher for barley than for oat and also higher for insoluble than for soluble β-glucan. A greater proportion of barley β-glucan remained insoluble than of oat β-glucan. The molar masses of soluble β-glucans of oats and barley were the same as were those of insoluble β-glucans of oats and barley. To analyse the effects of cooking, baking, fermentation and drying, β-glucan was isolated from porridge, bread and fermentate and also from their starting materials. More β-glucan was released after cooking and less after baking. Drying decreased the extractability for bread and fermentate but increased it for porridge. Different hydrolysis methods of β-glucan were compared. Acid hydrolysis and the modified AOAC method gave similar results. The results of hydrolysis with lichenase gave higher recoveries than the other two. The combination of lichenase hydrolysis and high-performance anion-exchange chromatography with pulse-amperometric detection was found best for the analysis of β-glucan content. The content of insoluble fibre was higher for barley than for oats and the amount of β-glucan in the insoluble fibre fraction was higher for oats than for barley. The flow properties of both water and aqueous cuoxam solutions of oat and barley β-glucans were studied. Shear thinning was stronger for the water solutions of oat β-glucan than for barley β-glucan. In aqueous cuoxam shear thinning was not observed at the same concentration as in water but only with high concentration solutions. Then the viscosity of barley β-glucan was slightly higher than that of oat β-glucan. The oscillatory measurements showed that the crossover point of the G´ and G´´ curves was much lower for barley β-glucan than for oat β-glucan indicating a higher tendency towards solid-like behaviour for barley β-glucan than for oat β-glucan.

Rintamamiesten muonitus Suomessa sotavuosina 1939-1945

This study analyzes the war-time rations the Finnish soldiers received on the front from 1939 until 1945. The main objective was to determine the contents of the rations and how they affected the soldiers' nutrition and morale. The information concerning food and feeding is mainly based on the official documents found in the Military Archives. Some additional material was from the historical literature, some from memoirs, or from the veterans who personally experienced the front. The documents in the Archives of Military Medicine provided information on the soldiers' deficiencies. During the Winter War, which took place from 30 November 1939 until 13 March 1940, ample food was available. The cold climate caused problems and the fresh food got frozen. However, no severe deficiency cases were reported and the morale was high. By contrast, during the Continuation War, which began in June, 1941 and ended in September, 1944, difficulties were experienced. At the time farming in the country faced serious problems due to the shortage of labour, fuel, etc. Furthermore, importing food was generally not possible. However, importing food mainly from Germany saved the Finns from hunger. In addition, the self activity of the soldiers on the front added somewhat to the food production. But the rations had to be reduced. Their energy values were consequently low, especially for the young men. Food was monotonous and occasionally caused complaints. The main sources of protein, vitamins and minerals were the whole cereal foods. Butter was fortified with vitamin A and vitamin C tablets were also distributed, to compensate for the scant food sources. Only approximately 300 serious deficiency cases required hospital care during the three years time, out of a total of 400 000 soldiers. Feeding the young soldiers during the war (1944 - 1945) in Lapland, which had been destroyed, was problematic but the increased rations also saved them from deficiencies. In spite of the severe difficulties experienced occasionally in feeding the soldiers during the wars, the system worked all the time. The soldiers were fed, the cases of nutritional deficiency and epidemics caused by food were kept very limited and the morale of soldiers remained high.

Folates in rye: Determination and enhancement by food processing

The average daily intake of folate, one of the B vitamins, falls below recommendations among the Finnish population. Bread and cereals are the main sources of folate, rye being the most significant single source. Processing is a prerequisite for the consumption of whole grain rye; however, little is known about the effect of processing on folates. Moreover, data on the bioavailability of endogenous cereal folates are scarce. The aim of this study was to examine the variation in as well as the effect of fermentation, germination, and thermal processes on folate contents in rye. Bioavailability of endogenous rye folates was investigated in a four-week human intervention study. One of the objectives throughout the work was to optimise and evaluate analytical methods for determining folate contents in cereals. Affinity chromatographic purification followed by high-performance liquid chromatography (HPLC) was a suitable method for analysing cereal products for folate vitamers, and microbiological assay with Lactobacillus rhamnosus reliably quantified the total folate. However, HPLC gave approximately 30% lower results than the microbiological assay. The folate content of rye was high and could be further increased by targeted processing. The vitamer distribution of whole grain rye was characterised by a large proportion of formylated vitamers followed by 5-methyltetrahydrofolate. In sourdough fermentation of rye, the studied yeasts synthesized and lactic acid bacteria mainly depleted folate. Two endogenous bacteria isolated from rye flour were found to produce folate during fermentation. Inclusion of baker s yeast in sourdough fermentation raised the folate level so that the bread could contain more folate than the flour it was made of. Germination markedly increased the folate content of rye, with particularly high folate concentrations in hypocotylar roots. Thermal treatments caused significant folate losses but the preceding germination compensated well for the losses. In the bioavailability study, moderate amounts of endogenous folates in the form of different rye products and orange juice incorporated in the diet improved the folate status among healthy adults. Endogenous folates from rye and orange juice showed similar bioavailability to folic acid from fortified white bread. In brief, it was shown that the folate content of rye can be enhanced manifold by optimising and combining food processing techniques. This offers some practical means to increase the daily intake of folate in a bioavailable form.

Microbes in the tailoring of barley malt properties

Microbes have a decisive role in the barley-malt-beer chain. A major goal of this thesis was to study the relationships between microbial communities and germinating grains during malting. Furthermore, the study provided a basis for tailoring of malt properties with natural, malt-derived microbes. The malting ecosystem is a dynamic process, exhibiting continous change. The first hours of steeping and kilning were the most important steps in the process with regard to microbiological quality. The microbial communities consisting of various types of bacteria, yeasts and filamentous fungi formed complex biofilms in barley tissues and were well-protected. Inhibition of one microbial population within the complex ecosystem led to an increase of non-suppressed populations, which must be taken into account because a shift in microbial community dynamics may be undesirable. Both bacterial and fungal communities should be monitored simultaneously. Using different molecular approaches we showed that the diversity of microbes in the malting ecosystem was greater than expected. Even some new microbial groups were found in the malting ecosystem. Suppression of Gram-negative bacteria during steeping was advanategous for grain germination and malt brewhouse performance. Fungal communities including both filamentous fungi and yeasts significantly contributed to the production of microbial beta-glucanases and xylanases, and were also involved in proteolysis. Well-characterized lactic acid bacteria (Lactobacillus plantarum VTT E-78076 and Pediococcus pentosaceus VTT E-90390) proved to be an effective way of balancing the microbial communities in malting. Furthermore, they had positive effects on malt characteristics and notably improved wort separation. Previously the significance of yeasts in the malting ecosystem has been largely underestimated. This study showed that yeast community was an important part of the industrial malting ecosystem. Yeasts produced extracellular hydrolytic enzymes with a potentially positive contribution to malt processability. Furthermore, several yeasts showed strong antagonistic activity against field and storage moulds. Addition of a selected yeast culture (Pichia anomala VTT C-04565) into steeping restricted Fusarium growth and hydrophobin production and thus prevented beer gushing. Addition of P. anomala C565 into steeping water tended to retard wort filtration, but the filtration was improved when the yeast culture was combined with L. plantarum E76. The combination of different microbial cultures offers a possibility to use ther different properties, thus making the system more robust. Improved understanding of complex microbial communities and their role in malting enables a more controlled process management and the production of high quality malt with tailored properties

Occurrence and properties of steryl ferulates and glycosides in wheat and rye

Cereal kernels are known to contain a number of minor components that possess beneficial health attributes. In this thesis rye and wheat were studied as sources of steryl ferulates and steryl glycosides and their behaviour in processing were evaluated. Further, enzymatic hydrolysis of these conjugates was studied, as well as the capacity of steryl ferulates to inhibit lipid oxidation at different temperatures. Steryl ferulates were shown to have a strong positive correlation with dietary fibre contents in milling fractions from the outer parts of the kernels obtained from a commercial scale mill. Highest contents of steryl ferulates were found in the bran in both cereals, with the content decreasing once moving towards the inner parts of the kernel. Variation in the contents of steryl ferulates was higher in wheat fractions than rye fractions. Steryl glycosides, on the other hand, had either negative or no correlation with dietary fibre, and the range of the steryl glycoside contents was much narrower than that of steryl ferulates in both cereals. There were significant differences in the sterol compositions of these steryl conjugates when compared with each other or with the total plant sterols in the corresponding fractions. Properties of steryl ferulates and steryl glycosides were evaluated after common processing methods and in enzymatic hydrolysis. Thermal and mechanical processing had only minor or no effects on the contents of steryl conjugates from rye and wheat bran. Enzymatic treatments on the other hand caused some changes, especially in the contents of glycosylated sterols. When steryl ferulates extracted from rye or wheat bran were subjected to enzymatic treatments by steryl esterase, significant differences in the rates of hydrolysis were observed between steryl ferulates from different sources with differing sterol compositions. Further, differences were also observed between enzymes from different sources. Steryl glycosides were shown to be hydrolysed by β-glucosidase (cellobiase) from A. niger, but less with β-glucosidases from other sources. Steryl ferulates showed good antioxidant activity at both moderate and high temperatures. In bulk and emulsion systems of methyl linoleate at 40°C steryl ferulates extracted from rye and wheat bran inhibited hydroperoxide formation much more effectively than synthetic steryl ferulates or those extracted from rice (γ-oryzanol), demonstrating that the sterol composition has an effect on the activity. At cooking (100°C) and frying temperatures (180°C) sitostanyl ferulate was shown to inhibit polymer formation significantly and, especially at 100°C, comparably to α-tocopherol. The rate of antioxidant degradation was slower for sitostanyl ferulate, showing higher heat stability than α-tocopherol. When evaluated as a mixture, no synergistic effect was observed between these two antioxidants. The data presented in this thesis provides information that may henceforth be applied when evaluating the intakes of steryl conjugates from cereal sources, as well as their possible influences as minor bioactive components. Wheat and rye both are good sources of steryl ferulates and steryl glycosides and, especially with steryl ferulates, what may be lost out to some other cereals on quantity is compensated with quality of the sterol composition.

Preparation, structural analysis and prebiotic potential of arabinoxylo-oligosaccharides

Arabinoxylo-oligosaccharides (AXOS) can be prepared enzymatically from arabinoxylans (AX) and AXOS are known to possess prebiotic potential. Here the structural features of 10 cereal AX were examined. AX were hydrolysed by Shearzyme® to prepare AXOS, and their structures were fully analysed. The prebiotic potential of the purified AXOS was studied in the fermentation experiments with bifidobacteria and faecal microbiota. In AX extracted from flours and bran, high amounts of a-L-Araf units are attached to the b-D-Xylp main chain, whereas moderate or low degree of substitution was found from husks, cob and straw. Nuclear magnetic resonance (NMR) spectroscopy showed that flour and bran AX contain high amounts of a-L-Araf units bound to the O-3 of b-D-Xylp residues and doubly substituted b-D-Xylp units with a-L-Araf substituents at O-2 and O-3. Barley husk and corn cob AX contain high amounts of b-D-Xylp(1→2)-a-L-Araf(1→3) side chains, which can also be found in AX from oat spelts and rice husks, and in lesser amounts in wheat straw AX. Rye and wheat flour AX and oat spelt AX were hydrolysed by Shearzyme® (with Aspergillus aculeatus GH10 endo-1,4-b-D-xylanase as the main enzyme) for the production of AXOS on a milligram scale. The AXOS were purified and their structures fully analysed, using mass spectrometry (MS) and 1D and 2D NMR spectroscopy. Monosubstituted xylobiose and xylotriose with a-L-Araf attached to the O-3 or O-2 of the nonreducing end b-D-Xylp unit and disubstituted AXOS with two a-L-Araf units at the nonreducing end b-D-Xylp unit of xylobiose or xylotriose were produced. Xylobiose with b-D-Xylp(1→2)-a-L-Araf(1→3) side chain was also purified. These AXOS were used as standards in further identification and quantification of corresponding AXOS from the hydrolysates in high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) analysis. The prebiotic potential of AXOS was tested in in vitro fermentation experiments. Bifidobacterium adolescentis ATCC 15703 and B. longum ATCC 15707 utilized AXOS from the AX hydrolysates. Both species released L-arabinose from AXOS, but B. adolescentis consumed the XOS formed, whereas B. longum fermented the L-arabinose released. The third species tested, B. breve ATCC 15700, grew poorly on these substrates. When cultivated on pure AXOS, the bifidobacterial mixture utilized pure singly substituted AXOS almost completely, but no growth was detected with pure doubly substituted AXOS as substrates. However, doubly substituted AXOS were utilized from the mixture of xylose, XOS and AXOS. Faecal microbiota utilized both pure singly and doubly substituted AXOS. Thus, a mixture of singly and doubly substituted AXOS could function as a suitable, slowly fermenting prebiotic substance. This thesis contributes to the structural information on cereal AX and preparation of mono and doubly substituted AXOS from AX. Understanding the utilization strategies is fundamental in evaluating the prebiotic potential of AXOS. Further research is still required before AXOS can be used in applications for human consumption.

Nitrogen dynamics of organic farming in a crop rotation based on red clover (Trifolium pratense) leys

In agricultural systems which rely on organic sources of nitrogen (N), of which the primary source is biological N fixation (BNF), it is extremely important to use N as efficiently as possible with minimal losses to the environment. The amount of N through BNF should be maximised and the availability of the residual N after legumes should be synchronised to the subsequent plant needs in the crop rotation. Six field experiments in three locations in Finland were conducted in 1994-2006 to determine the productivity and amount of BNF in red clover-grass leys of different ages. The residual effects of the leys for subsequent cereals as well as the N leaching risk were studied by field measurements and by simulation using the CoupModel. N use efficiency (NUE) and N balances were also calculated. The yields of red clover-grass leys were highest in the two-year-old leys (6 700 kg ha-1) under study, but the differences between 2- and 3-year old leys were not high in most cases. BNF (90 kg ha-1 in harvested biomass) correlated strongly with red clover dry matter yield, as the proportion of red clover N derived from the atmosphere (> 85%) was high in our conditions of organically farmed field with low soil mineral N. A red clover content of over 40% in dry matter is targeted to avoid negative N-balances and to gain N for the subsequent crop. Surprisingly, the leys had no significant effect on the yields and N uptake of the two subsequent cereals (winter rye or spring wheat, followed by spring oats). On the other hand, yield and C:N of leys, as well as BNF-N and total-N incorporated into the soil influenced on subsequent cereal yields. NUE of cereals from incorporated ley crop residues was rather high, varying from 30% to 80% (mean 48%). The mineral N content of soil in the profile of 0-90 cm was low, mainly 15-30 kg ha-1. Simulation of N dynamics by CoupModel functioned satisfactorily and is considered a useful tool to estimate N flows in cropping systems relying on organic N sources. Understanding the long-term influence of cultivation history and soil properties on N dynamics remains to be a challenge to further research.

Response of Tribolium castaneum and Rhyzopertha dominica to various resources, near and far from grain storage

Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) are common cosmopolitan pests of stored grain and grain products. We evaluated the relative attraction of T.castaneum and R.dominica to wheat, sorghum and cotton seeds in the field, near grain storage facilities and well away from storages in southern and central Queensland using multiple trapping techniques. The results show that T.castaneum is more strongly attracted to linted cotton seed relative to wheat, whereas R.dominica did not respond to cotton seed at all and was attracted only to wheat. Significantly more adults of T.castaneum (10-15 times) were attracted to traps placed on the ground, near grain storage, than to equivalent traps that were suspended (1.5m above the ground) nearby. These results suggest that Tribolium beetles detect and respond to resources towards the end of their dispersal flight, after which they localize resources while walking. By contrast R.dominica was captured only in suspended traps, which suggests they fly directly onto resources as they localize them. The ability of both species to colonize and reproduce in isolated resource patches within the relatively short time of 1month is illustrated by the returns from the traps deployed in the field (at least 1km from the nearest stored grain) even though they caught only a few beetles. The results presented here provide novel insights about the resource location behaviours of both T.castaneum and R.dominica. In particular, the relationship of T.castaneum with non-cereal resources that are not conventionally associated with this species suggests an emphasis on these other resources in investigating the resource location behaviour of these beetles. This new perspective on the ecology of T. castaneum highlights the potential role of non-cereal resources (such as the lint on cotton seed) in the spread of grain pest infestations.

Influence of different nitrogen rates and DMPP nitrification inhibitor on annual N2/O emissions from a subtropical wheat–maize cropping system

Global cereal production will need to increase by 50% to 70% to feed a world population of about 9 billion by 2050. This intensification is forecast to occur mostly in subtropical regions, where warm and humid conditions can promote high N2O losses from cropped soils. To secure high crop production without exacerbating N2O emissions, new nitrogen (N) fertiliser management strategies are necessary. This one-year study evaluated the efficacy of a nitrification inhibitor (3,4-dimethylpyrazole phosphate—DMPP) and different N fertiliser rates to reduce N2O emissions in a wheat–maize rotation in subtropical Australia. Annual N2O emissions were monitored using a fully automated greenhouse gas measuring system. Four treatments were fertilized with different rates of urea, including a control (40 kg-N ha−1 year−1), a conventional N fertiliser rate adjusted on estimated residual soil N (120 kg-N ha−1 year−1), a conventional N fertiliser rate (240 kg-N ha−1 year−1) and a conventional N fertiliser rate (240 kg-N ha−1 year−1) with nitrification inhibitor (DMPP) applied at top dressing. The maize season was by far the main contributor to annual N2O emissions due to the high soil moisture and temperature conditions, as well as the elevated N rates applied. Annual N2O emissions in the four treatments amounted to 0.49, 0.84, 2.02 and 0.74 kg N2O–N ha−1 year−1, respectively, and corresponded to emission factors of 0.29%, 0.39%, 0.69% and 0.16% of total N applied. Halving the annual conventional N fertiliser rate in the adjusted N treatment led to N2O emissions comparable to the DMPP treatment but extensively penalised maize yield. The application of DMPP produced a significant reduction in N2O emissions only in the maize season. The use of DMPP with urea at the conventional N rate reduced annual N2O emissions by more than 60% but did not affect crop yields. The results of this study indicate that: (i) future strategies aimed at securing subtropical cereal production without increasing N2O emissions should focus on the fertilisation of the summer crop; (ii) adjusting conventional N fertiliser rates on estimated residual soil N is an effective practice to reduce N2O emissions but can lead to substantial yield losses if the residual soil N is not assessed correctly; (iii) the application of DMPP is a feasible strategy to reduce annual N2O emissions from sub-tropical wheat–maize rotations. However, at the N rates tested in this study DMPP urea did not increase crop yields, making it impossible to recoup extra costs associated with this fertiliser. The findings of this study will support farmers and policy makers to define effective fertilisation strategies to reduce N2O emissions from subtropical cereal cropping systems while maintaining high crop productivity. More research is needed to assess the use of DMPP urea in terms of reducing conventional N fertiliser rates and subsequently enable a decrease of fertilisation costs and a further abatement of fertiliser-induced N2O emissions.