Typescript (photocopy) / v, 256 leaves, [2] leaves of col. plates : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Plant Physiology, University of Adelaide, 1982

The literature suggests that grain number largely determines and as such limits yield in barley. Many of the reported studies were conducted in relatively low yielding environments and it is unclear if grain number is also a limiting factor in high yield potential climates. Nor is it known with certainty what physiological or morphological traits must be targeted in order to increase grain number. There may be a degree of trade-off between yield components whereby grain number is adjusted according to resource availability to the plant, either pre- or post-anthesis, in a way that ensures consistently well-filled grains at harvest. If mechanisms exist for adjusting grain numbers or grain storage capacity after anthesis to match assimilate availability, this may place limits on how far yield can be increased without increasing post-anthesis assimilate production. In order to determine the scope for increasing the yield potential of barley a more thorough understanding of the potential trade-offs between grain number, grain storage capacity and post-anthesis assimilate supply is required. The aim of research reported in this thesis was to establish what determines the yield of spring barley in Ireland and to investigate the timing and possible mechanisms involved in regulating grain number and grain storage capacity in relation to the supply of photoassimilates. Field experiments were carried out on spring barley (Hordeum vulgare L., cv. Quench) at several locations in Ireland from 2011 to 2013. A sub-set of experiments involving destructive sampling and in-field assessments on plots managed as per current best farm practice gathered crop growth, development, and yield component data across sites and seasons in order to establish what determines yield under typical crop production conditions. Separate experiments artificially manipulated the source:sink ratio of plots via shading and seed rate treatments to investigate in more detail the mechanisms determining grain number and grain weight and any potential trade-off between the two components. Grain number accounted for most of the variation in yield across 9 site/seasons of crops managed as per current best practice in Ireland (P < 0.001; R2 = 0.84) while grain weight remained relatively conserved. Ear number accounted for most of the variation in grain number (P = 0.002; R2 = 0.75) and ear number itself was largely determined by shoot survival from an early season peak through to harvest (P <0.001; R = 0.96). Shoot size and weight at the beginning of stem extension had the largest influence on shoot survival. Shading treatments were used to test whether there was a mechanism for adjusting grain numbers after anthesis to match the availability of assimilate for grain filling. Substantial post-anthesis reductions in assimilate supply during grain filling in 2011 and 2012 did not significantly reduce grain number (P > 0.05). A small reduction in grain number (8%) was found in response to shading for a two week period early post-anthesis in 2013, however this was likely a reduction in grain set in shoots or spikelets that reached anthesis after the treatment was imposed rather than a post-anthesis abortion or down-regulation of grain number. Percentage light interception by well managed (unshaded) canopies shortly after anthesis was generally greater than 93% across several sites and seasons, therefore increasing grain numbers to increase sink capacity would likely be associated with an unavoidable decrease in the amount of light intercepted per grain during the early grain development period. However, experiments showed that grain weight at harvest was neither reduced nor increased in response to variations in light interception during this period of endosperm development (P > 0.05), because soluble sugar concentrations in the grain were maintained at the expense of storage reserve deposition in the stems. Results suggest that grain number and grain storage capacity may both be determined pre-anthesis resulting in a trade-off during stem extension whereby grain numbers are adjusted in a way that helps conserve grain weight. A strong negative relationship between ear number and grain number per ear (P < 0.001; R2 = 0.81) across two sites of seed rate experiments in 2013 resulted in a plateau in overall grain number of approximately 18,000 grains m-2 suggesting that there may be a limit to how many grains can be established in a given environment; this was achieved with an ear number of approximately 1000 ears m-2. Yield potential for Irish conditions was estimated at 12.29 t ha-1 at 85% dry matter based on estimates of potential assimilate supply during grain filling; with a grain number of 26,481 m-2 required to utilise this. These estimates are both 44% higher than the mean yield and grain number achieved in crops managed as per current best farm practice. Once high potential ear numbers are secured (> 1000 m-2), breaking the negative relationship between ear number and grain number per ear may hold the key to further increasing grain number and hence yield potential. Increasing assimilate production and partitioning to ears during stem extension, either through increases in the duration of stem extension or solar radiation use efficiency, may enable larger grain numbers to be produced whilst maintaining or increasing individual grain storage capacity and deposition of stem storage reserves. Water and nutrient availability, as well as susceptibility to lodging may present further limitations to yield in the future.

Current trends in population growth suggest that global food production is unlikely to satisfy future demand under predicted climate change scenarios. Therefore, further improvements on wheat yield potential will be essential to meet future food demand. Thus, to further raise wheat grain yield it is critical to understand the physiological basis of grain number per m2 determination. Yield responsiveness to resource availability is usually related to grain number per m2 in most of grain crops, such as durum wheat. Under Mediterranean conditions, wheat yields vary widely, mainly in response to erratic rainfall, but it has been proposed that part of this variability may be reduced through nitrogen (N) management. Wheat yield responses to N fertilisation are usually related to those of grains per m2, which in turn is the consequence of processes related to floret development (floret initiation followed by floret death/survival) during stem elongation. However, there are almost no studies published relating floret primordia generation and survival in response to increases in N availabilities in wheat. Understanding the dynamics of floret primordia development as a physiological determinant of grain setting can be relevant to further increase grain yield in wheat. The focus of this thesis was to study the effects of N availability and the differences among modern cultivars (and, in some cases, combined with availability of other resources) on dynamics of floret development and survival determining the fate of these primordia and the generation of grain number in durum wheat. Six experiments were conducted (4 semi-controlled and 2 field conditions) during four consecutive growing seasons at Catalonia, NE Spain, with a combination of different N and water availabilities and contrasting modern durum wheat cultivars. Across all experiments, yield responsiveness to N was, in general, related to grain number increases as an indirect response to N through its effect on increasing growth. This is not only based on the fact that the relationship of grain number with spike dry matter was not improved if spike N were used instead, but also on the fact that detillering did increased grain number through the same relationships to spike dry matter. Also, improved spike fertility was due to both producing more fertile florets (in response to N and water or to the removal of competing shoots) and to reduce the percentage of failure of fertile florets in becoming grains. Responsiveness of the number of fertile florets was determined by a developmental response of floret primordia, which under high resource availability conditions continued developing normally in some distal florets of the spikelets, at any position of the spike, whilst in more stressful conditions their development stopped. Genotypic variation in fruiting efficiency was found for modern durum wheat cultivars and there was a tendency for some cultivars to have higher values of fruiting efficiency in most of the environments. Differences in fruiting efficiency were responsible for genotypic differences in grain number. A functional negative relationship was found between grain weight and fruiting efficiency, revealing a trade-off related to spike growth per floret developing normally.

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No. of bitstreams: 2 Dissertação - Daniany Rodrigues Adorno Silva - 2016.pdf: 3317454 bytes, checksum: 2a1e85ca0c09e0b89edfaf2b184ee8e7 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The rice (Oryza sativa) is a staple food for the majority of the world's population. One of the main challenges for the breeding programs of this crop is the increase of the yield potential of commercial cultivars. For the development of superior lines and cultivars is necessary to identify and incorporate superior alleles in genetic breeding programs. One of the alterna-tives for the identification of useful genetic variability is the crossing involving genetically unrelated parents, as well as genotyping and phenotyping the segregating populations de-rived from these crossings, and posterior analysis of QTL (Quantitative Trait Locus). This study aimed to identify genes associated with yield of grains in rice through Genotyping by Sequencing (GBS), field experiments and a posterior analysis of QTL involving 232 RIL’s (Recombinant Inbred Lines) derived from the inter-subspecific crossing Epagri 108 (indica) x IRAT 122 (japonica) in two locations (Goianira - State of Goias and Boa Vista - State of Roraima). For the QTL analysis it was mapped 2,382 SNP markers, which identified two QTLs for yield, both located on chromosome 6, exclusively for the experiment of Goianira. The average effects of allele substitutions were 1,365.20 kg.ha-1 and 1,075.49 kg.ha-1, and the proportions of the phenotypic variance explained by the QTLs were 18% and 29%, clas-sified as QTL of large effect. All favorable alleles for yield were derived from genitor IRAT 122. One of the QTL identified to the productivity showed interaction QTL x E, which was expected due to the high significance of interactions G x E detected in the joint analysis. For the experiment of Goianira was also analyzed the trait hundred grain weight, and it were found three QTLs on chromosomes 5, 6 and 12. The average effects of the allelic substitution for the hundred grain weight ranged from 0.12 to 0.14 grams. The proportions of the pheno-typic variance explained by the QTLs ranged from 6 to 8%. Approximately 84% of the QTLs for the hundred grain weight were obtained from the parent IRAT 122. In chromosomal regions identified QTLs for grain yield are contained two genes: the LOC_Os06g16870, a transposon En/Spm, and the LOC_Os06g33320 whose function remains unknown, but whose expression was almost exclusively found in the inflorescences of rice. For the hundred grain weight, the chromosome region of the QTL located on chromosome 5 is located in a linkage block with 82 genes that co-segregate, and whose putative functions include, among others, the adjustment of tillering, pollen formation, grain filling and resistance to abiotic stress. For the QTL located on chromosome 6 it was identified the gene LOC_Os06g16160, which the function still unassigned, but whose expression is located almost exclusively in the root. On chromosome 12, the QTL containing the gene LOC_Os12g41956 expresses a protein of the galactosyl-transferase family, which participates in the synthesis of the RFO’s (Raffinose Family of Oligosaccharides), regulating the levels of reserve oligosaccharides in seeds. / O arroz (Oryza sativa) é um alimento básico para a maioria da população mundial. Um dos principais desafios para os programas de melhoramento dessa cultura é o aumento do poten-cial produtivo de cultivares comerciais. Para o desenvolvimento de linhagens e cultivares superiores é necessário que sejam incorporados alelos superiores em genitores dos progra-mas de melhoramento. Uma das alternativas para a identificação da variabilidade genética útil é a realização de cruzamentos envolvendo genitores pouco aparentados e a genotipagem e fenotipagem de populações segregantes derivadas desses cruzamentos, com uma posterior análise de QTL (locos de caracteres quantitativos). Esse trabalho teve por objetivo identificar genes associados à produtividade de grãos em arroz por meio da genotipagem por sequenci-amento (GBS), experimentos de campo e uma posterior análise de QTL envolvendo 232 RILs (linhas puras recombinantes) derivadas do cruzamento inter-subespecífico Epagri 108 (indica) x IRAT 122 (japonica) em dois locais (Goianira-GO e Boa Vista-RR). Para a análise de QTL foram mapeados 2.382 marcadores SNPs, os quais identificaram dois QTLs para produtividade, ambos localizados no cromossomo 6, exclusivamente para o experimento de Goianira. Os efeitos médios de substituição alélica foram de 1.365,20 kg.ha-1 e 1.075,49 kg.ha-1, e as proporções das variâncias fenotípicas explicadas pelos QTLs foram de 18% e 29%, classificadas como QTLs de grandes efeitos. Todos os alelos favoráveis para produti-vidade foram provenientes do genitor IRAT 122. Um dos QTLs identificados para a produ-tividade apresentou interação QTL x E, o que já era esperado devido à alta significância das interações G x E detectadas na análise de variância conjunta. Para o experimento de Goianira também foi analisado o peso de 100 grãos, e foram encontrados três QTLs, localizados nos cromossomos 5, 6 e 12. Os efeitos médios de substituição alélica para o peso de 100 grãos variaram de 0,12 a 0,14 gramas. As proporções da variância fenotípica explicadas pelos QTLs variaram de 6 a 8%. Cerca de 84% dos QTLs identificados para o peso de 100 grãos foram provenientes do genitor IRAT 122. Nas regiões cromossômicas dos QTLs identifica-dos para produtividade de grãos estão contidos dois genes: o LOC_Os06g16870, um trans-poson En/Spm, e o LOC_Os06g33320, de função ainda desconhecida, mas cuja expressão foi quase que exclusivamente identificada nas inflorescências de arroz. Para o peso de 100 grãos, a região cromossômica do QTL localizado no cromossomo 5 está contido em um bloco de ligação contendo 82 genes que co-segregam, e cujas funções putativas incluem, dentre outras, a regulação do perfilhamento, formação de pólen, enchimento de grãos e re-sistência a estresse abiótico. Para o QTL identificado no cromossomo 6, nesta região cro-mossômica está presente o gene LOC_Os06g16160, ainda sem atribuição de função, mas cuja expressão está localizada quase que exclusivamente na raiz. Já no cromossomo 12, a região cromossômica do QTL contém o gene LOC_Os12g41956, que expressa uma proteína 15 da família galactosil-transferase, que participa da síntese dos RFOs (oligossacarídeos da fa-mília das rafinoses), regulando os níveis de oligossacarídeos de reserva nas sementes

The theses presents results of experiments with spring barley started in years 2017 and 2018. The experiments were put into practice at Mr Jiří Nepovím's (BSc) place in Opatovice near Světlá nad Sázavou. Laudis 550 was used as the experimental variety of spring barley and the objective of the experiment was to observe the increasing amount of nitrogen and its effect on the resulting quantity and quality. The experimental amounts of nitrogen were set to 60 kg.ha-1, 75 kg.ha-1, 90 kg.ha-1, 105 kg.ha-1 and 120 kg.ha-1. With the increasing amount of nitrogen the crop increased of 0,2 - 0,4 t.ha-1. The share of nitrogen substances in grain increased of 0,2-0,5 %.