No description available.

Fear of continuing food shortage in India has stimulated efforts to increase agricultural output, and in recent years much research has been directed towards raising returns per unit area of land. Dwarf, high yielding varieties of wheat, rice, maize and millet introduced to India in the 1960s are capable of at least doubling the yields of their indigenous counterparts, and in addition, the shorter maturation period required by the new varieties potentially increases the number of crops that can be harvested each year. Theoretically, these plants could contribute much towards raising agricultural output, but only if their environmental needs are met, as high yields depend heavily on large and frequent applications of water, fertilizer, insecticide and pesticide. In the agricultural district of Bulandshahr in western Uttar Pradesh, by 1972, new varieties of wheat in particular, had been widely adopted, but the level of their success was unknown. A study limited to six villages was conducted in central Bulandshahr in 1972, with the aim of assessing how successfully farmers were growing dwarf wheat. Data were collected mainly by questionnaire and as areal patterns showed that the adoption of new wheat was almost complete in the study area, the next step was to see whether new farming methods had been similarly adopted. Essential cultivation techniques were examined to see if they had changed significantly from traditional methods, but the best measure of success, in farming dwarf wheat -is the yield, so information on crop returns was collected and the relationships of such returns with farming techniques examined. As all results showed considerable variation, the cultivators were classified, for example, according to their caste, farm size or education level, in an attempt to identify any factors which may have influenced their farming practices. The success of the high yielding varieties rests not only on the cultivators' enthusiasm, but also on a continued supply of essential inputs. Both field work and secondary sources showed the growing difficulties of obtaining adequate inputs, a trend unlikely to change rapidly, and which, if it continued, could reverse the initial success which attended the raising of dwarf varieties.

Phosphorus (P) is one of the most limiting and important elements in crop production, yet often has limited availability in the soil. Manufactured inorganic P fertilisers are required to improve soil and crop P supply but their use depletes finite reserves of rock phosphate and impacts on water quality and ecosystem biodiversity. Bio-inoculants have a potential role to increase soil P supply and reduce dependence on expensive fertilisers. The objective of this thesis was to further understand the role of mycorrhizae (M) and P solubilizing bacteria (PSB) bio-inoculants and external P sources (super phosphate (SP), struvite (AMP) and rock phosphate (RP)on phosphorus availability in soil and their effects on the growth, yield and P uptake of barley. Field experiments on low P status soils in 2010 and 2011 demonstrated the potential for the use of bio-inoculants (PSB and M) in mobilizing P from soil and significantly (P <0.05) enhancing P uptake to increase growth of barley, and to a lesser extent, grain yield. It was postulated that bio-inoculant effects in the field were compromised by the presence of native M and PSB. Glasshouse pot experiments were conducted with a range of growth media: horticultural sand (zero P), field soil (low P status but with native micro-organisms) and heat sterilized field soil. These demonstrated the effects of bio-inoculants without the presence of native M and PSB, and to a lesser extent in the presence of native micro-organisms, in terms of increased plant root and shoot growth, grain yield and tissue P concentration. Across all experiments bio-inoculants (M and PSB) increased the effectiveness of water soluble SP, partially soluble AMP and insoluble RP. M and PSB were equally effective. In combination with these external P sources, bio-inoculants (M and PSB) significantly (P < 0.05) increased yield, P concentration and total P uptake, plant dry matter and concentration of P in the grain compared to P fertilizers without bio-inoculants. However, applications of P fertilizers reduced the colonization of roots by mycorrhizae. The potential role of P uptake enhancing bio-inoculants in reducing external inputs in agriculture is discussed.

Variation in agronomy and crop production environment often have interactive effects on cereal seed dormancy and seed and grain quality, possibly by effects on canopy temperature, seed size, or grain drying rate. The effect of rain, nitrogen (N) fertilizer, and fungicide on seed dormancy, grain quality and subsequent seedling growth of winter cereals was studied in three field experiments. Dormancy was released during seed development and maturation in barley, rye and triticale (2012) but released and then re-imposed in wheat (2012 and 2013). Dormancy release was stimulated in barley, rye and triticale, but not wheat, when crops were sheltered from rain in the field. Alpha-amylase activity was reduced and Hagberg falling number (HFN) increased by rain shelter in barley and wheat; HFN was associated positively with grain drying rate in barley and rye. Dormancy release in wheat was stimulated by fungicide application but delayed by early N. The latter increased sulphur and protein concentrations, HFN, and sodium dodecyl sulphate sedimentation volume. This effect was greater when fungicide and/or late N application were also applied. Fungicide improved subsequent seedling growth in wheat in 2012 only. Plumule and root length and dry weight were associated positively with seed size in both years. It is proposed that rain and N fertilizer delayed dormancy release through an indirect effect on grain drying rate and/or canopy temperature, whereas fungicide stimulated dormancy release by reducing grain surface fungal colonies. As expected, rain reduced but N fertilizer increased HFN, but treatment effects on grain drying rate and/or seed size could not account for all these effects on HFN. Fungicide increased subsequent seedling growth indirectly by increasing seed size in addition to a direct effect of fungicide on reducing infection on seedlings, but only when crop disease pressure was high (2012, not 2013).

The effect of drought and simulated rainfall on wheat (Triticum aestivum L.) seed and grain quality during development and maturation, including delayed harvest, were investigated with pot-grown plants harvested serially in a ventilated poly tunnel. Grain quality was assessed by seed mean dry weight (MOW), moisture content, HFN (Hagberg falling number), 50S (sodium dodecyl sulphate sedimentation), nitrogen content, sulphur content a nd seed size; seed quality by ability to germinate and subsequent air-dry seed storage survival. Developmental duration was the dominant factor influencing quality: HFN increased progressively and substantially from early seed filling to beyond harvest maturity in a sigmoidal pattern; 50S in a linear trend in 2012, but plateaued in 2013 from the end of seed filling; seed longevity in a curvi-linear trend (quantified by a polynomial) till harvest maturity; ability to germinate was maximal (100% normal germination) from 15-17 days before to 30-32 days after mass maturity (control). Stopping irrigation before seed filling ended reduced MOW and grain size, but increased HFN, 50S, germinability and seed longevity. Drought resulted in more rapid increase in HFN (14 days after anthesis > 21 DAA > 28 DAA > Control) and earlier attainment of maximum seed longevity. Ear wetting once close to harvest maturity reduced HFN considerably; thereafter it increased, though less than the control. Ear wetting reduced but root wetting increased HFN early in development, whereas both treatments at harvest maturity reduced seed and grain quality. Ear wetting reduced subsequent seed longevity immediately, but a period of re-drying in planta improved longevity - surpassing the control. Ear wetting (25-50mm) once at harvest maturity resulted in greater subsequent seed longevity than wetting for several days or >50mm. Hence direct and indirect and immediate and delayed effects of simulated rainfall were detected; drought improved and rainfall reduced HFN, but seed quality was increased by both.

No description available.

The rapid development of biotechnologies in crop genetics has increased the prospects for more efficient crop improvement. In barley breeding programmes, marker assisted selection (MAS) approaches for quantitative trait loci (QTL) for yield and yield components is still developing as it requires a thorough understanding of the genetic architecture of complex traits. This project reports an investigation of QTL for yield and yield components in two-row winter barley using three QTL mapping experiments. First, a bi-parental mapping population from an elite cross identified 23 genetic factors involved in the control of complex traits, including a strong grain weight QTL on the short arm of chromosome 2H. Second, two genome wide association studies (GWAS) were used to explore the genetic diversity for agronomic traits in European variety panels used in the NUE-CROPS and the AGOUEB projects. The integration of QTL mapping results revealed clustering of significant effects as potential targets for MAS. A major QTL cluster identified on 2H suggests that the centromeric HvCEN candidate gene is strongly involved in controlling the phenology and number of grains per ear in two-row winter barley and has additional pleiotropic effects on several agronomic traits. Some QTL effects were further confirmed by a QTL validation experiment using near isogenic lines (NILs) developed from advanced breeding material alongside the mapping experiments. Most of the QTL clusters involving different yield components showed that allele effects mirrored phenotypic correlations and a few QTL clusters were identified that had unidirectional increasing effects on all traits, such as an important tillering locus on 4HL. The exploitation of comparative genomics with rice revealed that SNP haplotypes could be used for candidate gene discovery at barley QTL clusters. The complexity of the QTL clusters associated with yield and yield components highlight the challenges in identifying relevant targets for marker assisted breeding when accounting for pleiotropic effects of loci controlling phenology and correlated traits. The study provides insights into the genetic architecture of complex traits in small grain cereals and for the implementation of associated QTL in commercial barley breeding activities.

Zymoseptoria tritici, the fungus that causes Septoria tritici blotch (STB) of wheat, is spread by splash borne transfer from the base of the plant to the flag leaf. This project is on a potential new source of resistance to STB discovered on chromosome 6A using association mapping (Arraiano & Brown 2016). Near isogenic lines generated for this region show no significant differences in STB symptoms when leaves are directly inoculated with Z. tritici. However, trials that are naturally infected or inoculated at the base of the plant show clear differences in their level of STB. This indicated that this region contains genes that cause differences in disease escape. The fact that the same marker Psp3071 is associated with yield traits (Snape et al, 2007) led to the hypothesis that the region may control a physiological trait that improves yield at the cost of aiding spore transmission. Candidate physiological traits, that could influence disease escape, have been tested in the 6A NILs including plant height, leaf area and senescence. The trait that fits with the pattern of the disease results best is leaf emergence, with later emerging leaves getting more STB. However, the effect of the 6A alleles on disease escape may be caused by multiple traits. Recombinant lines generated for the region have reduced the interval that contains the yield traits, though it is still unclear if the disease escape and yield effects are connected by linkage or pleiotropy.

Wheat is a major component of the UK diet, and provides approximately 20% of global caloric intake. Wheat is grown on more land area than any other crop, and the continued supply of wheat is essential for global food security. Biotechnology is likely to play an important role in the sustainable increase of wheat yields, and the genetic manipulation of chloroplasts for photosynthetic improvement has many potential advantages over transformation of the nuclear genome. The genetic modification of the chloroplast genome via transformation was first demonstrated in the late 1980’s, and since then, chloroplast transformation of many Dicotyledonous (dicot) plant species such as Nicotiana tabaccum has been routinely performed. In comparison, the transformation of chloroplasts in Monocotyledons (monocot) plant species, which includes all cereal crops, has made far less progress. To date, there has been no reproducible homoplasmic plastid transformation event in the monocots. This study identifies a number of bottlenecks responsible for the prevention of chloroplast transformation in wheat. One such bottleneck is the lack of a suitable explant for plastid transformation, as traditional nuclear transformation targets are absent of metabolically active plastids. This study has developed a robust regeneration protocol for a previously undescribed tissue, termed the primary inflorescence leaf sheath (piLS), which is rich in active chloroplasts. Functional wheat specific chloroplast transformation vectors have been generated, and bombardment studies have been conducted with these on piLS and a second tissue, the immature embryosderived callus. Immature embryo callus (IEC) does not contain active plastids, however contains pro-plastids and is highly embryogenic. To uncover novel ways of increasing photosynthesis in C3 plants, a number of transplastomic tobacco lines expressing the Synechococcus elongatus PCC 7942 ictB gene were generated. Previous studies suggest that ictB may be an inorganic carbon transporter. In a number of transplastomic lines produced in this study, the intercellular carbon concentration (Ci) is significantly increased. This increased Ci did not result in an increased photosynthetic rate, however did cause a number of phenotypic differences, such as smaller plants, wider leaves, and earlier seed pod formation. The results, with regards to chloroplast transformation, and its implications in improving photosynthesis within C3 plants, are discussed in this thesis.

Fusarium head blight (FHB) is an economically important disease of barley caused by mycotoxin-producing Fusarium species. Resistance to FHB is associated with several agronomic traits, particularly height. Taller cultivars are generally more resistant; however increased height is less favourable due to the prospect of lodging, creating a trade-off between disease resistance and agronomic qualities. Disease assays with pathogens of differing trophic lifestyles were conducted using barley BRI1 mutation lines, which display brassinosteroid (BR) insensitivity and a semi-dwarf phenotype. Interestingly, bri1 semi-dwarf lines did not display increased susceptibility to FHB. Additionally, bri1 mutation provided advantageous resistance to necrotrophs but did not increase susceptibility to biotrophs, demonstrating an absence of a resistance trade-off. The barley cultivars Chevallier and Armelle display significant FHB resistance, yet also possess a tall height phenotype. To determine whether the resistance of these cultivars was associated with height, bi-parental populations were created by crossing to the short, modern variety NFC Tipple. High density genetic maps of the populations were produced using Genotyping-by-Sequencing and 384-SNP BeadXpress assays to enable quantitative trait loci (QTL) mapping of both FHB and agronomic traits. Within the C×T population, a QTL for FHB resistance was identified on chromosome 6H which was not associated with either height or heading date, suggesting that resistance in this region is not due to linkage or pleiotropy with these traits. In contrast, FHB resistance within the A×T population was coincident with both height and heading date QTL on 3H. QTL analysis of malting traits of Chevallier, an English malting landrace, was also undertaken. Chevallier compared favourably to NFC Tipple, a modern malting cultivar, for several malting characteristics including free amino nitrogen, diastatic power and wort β-glucan content. This demonstrates that Chevallier may be a useful potential source of both FHB disease resistance and quality traits.