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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Testes laboratoriais para a avaliação do desempenho germinativo no campo de sementes de lotes de soja (Glycine max (L.) Merrill /

Salum, Juliane Dossi. January 2009 (has links)
Resumo: trabalho foi desenvolvido na Faculdade de Ciências Agrárias e Veterinárias do Câmpus de Jaboticabal (UNESP), na Escola Superior de Agricultura "Luiz de Queiroz" em Piracicaba (USP) e na Universidade Camilo Castelo Branco (UNICASTELO) em Fernandópolis, e teve por objetivo verificar a eficiência de alguns testes de vigor, conduzidos em laboratório, na previsão do desempenho germinativo de sementes de lotes de soja quando semeados sob condições de campo compatíveis com a prática agrícola. Foram avaliados nove lotes de sementes por meio dos seguintes testes laboratoriais: primeira contagem, padrão de germinação, envelhecimento acelerado, condutividade elétrica, frio, comprimento de plântula de acordo com procedimentos recomendados pela ISTA (1995), comprimento de plântulas de acordo com procedimentos recomendados pela ABRATES (1999), massa seca e emergência de plântulas no campo nas três localidades. O tempo de duração de cada teste foi também determinado. Os dados obtidos foram submetidos à análise de variância e as médias comparadas pelo teste Tukey a 5% de probabilidade. Dados da correlação entre resultados laboratoriais e desempenho germinativo no campo foram também determinados. Os resultados deste trabalho indicam que o produtor de sementes de soja dispõe de um número razoavelmente alto de testes entre os quais optar para avaliar, com um grau aceitável de confiança, o que esperar do desempenho germinativo de um lote de sementes quando semeado sob condições ambientais usuais para a prática agrícola. Os testes de maior precisão seriam os do envelhecimento artificial, o da condutividade elétrica e o do frio. Se, além da confiabilidade, ao produtor de sementes interessar também rapidez na obtenção de resultados, o teste da condutividade elétrica seria o mais... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This research work was carried out on the campi of Jaboticabal, a unit of the Paulista State University (UNESP), Piracicaba, a unit of the University of São Paulo (USP), and Fernandópolis, a unit of the Camilo Castelo Branco University, the three of them localities of the state of São Paulo, Brazil. The objective of this work was the evaluation of some laboratory tests for the analysis of soybean seeds quality as to their efficiency in forecasting seed lots germinative performance in the field. The environmental conditions in Jaboticabal, Piracicaba, and Fernandópolis were within the limits usually found under normal agricultural practice. Nine commercial soybean seed lots were used whose vigor levels previous laboratory tests showed to be high, medium, and low. The laboratory tests were the following: standard germination, germination first count, accelerated aging, electrical conductivity, cold, seedling length according to procedures found in ISTA (1995), seedling length according to procedures found in ABRATES (1999), seedling dry matter and field emergence at the three localities. The results indicate that soybean seed companies have a reasonably high number of laboratory tests among which to choose, all of them yielding highly trustable results. The accelerated aging, the electrical conductivity, and the cold tests would be those of the highest precision. The electrical conductivity test, in addition to being of high precision, was found to be the fastest one. In addition to those, the seed company still has a high number of tests from which to choose. Among them, those in which seedling length is measured were found to be more efficient than those in which seedling dry matter is measured. The seedling length tests have a duration between 128 and 151 hours. The measuring of seedling length according to... (Complete abstract, click electronic access below) / Orientador: Nelson Moreira de Carvalho / Coorientador: Silvio Moure Cícero / Coorientadora: Gisele Herbst Vazquez / Banca: João Nakagawa / Banca: Roberval Daiton Vieira / Mestre
2

The Organizational Field of Crowdfunding : Emergence and Special Characteristics

Hammar, Corrie January 2015 (has links)
Crowdfunding is an online fundraising technique, where individuals or groups ask for contributions from a large number of people, i.e. “the crowd”. Crowdfunding first appeared in 2003 and has doubled its financial scope every year since 2011. Yet, very little is known about it, especially from a societal perspective. In this thesis I have attempted to understand how the organizations surrounding crowdfunding have structured themselves into an organizational filed, and also how “the crowd” might have granted this field special characteristics. This since “the crowd” is an element not earlier taken into consideration when studying field emergence. I have conducted a content analysis with data from 170 crowdfunding platforms and 190 media articles. I found that several events coincided in 2009 and opened up for the emergence of the crowdfunding field, and also that the understanding of crowdfunding’s purpose has shifted since 2003, from culture projects to start-ups. Regarding the special characteristic of the field it seems like the online nature enabled a fierce structuration pace, and also that “the crowd” constitutes an entity that cannot be captured by our traditional understanding of fields. The results suggest that when “the crowd” takes on functions in a field, the functions become invisible, and this has implications for future research regarding organizational fields.
3

Development of New and Alternative Resources for Breeding Low Phytate Soybeans

Burleson, Sarah Ann 12 May 2011 (has links)
Soybean (Glycine max (L.) Merr) cultivars with genetic reduction in seed phytate concentration will be a valuable resource to livestock producers both nutritionally and economically, as well as in the preservation of the environment. However, due to association with reduced seed germination and field emergence potential, low phytate (LP) soybean cultivars are not being advanced to commercialization. Soybean breeders of LP lines must adjust their techniques and resources in order to efficiently select LP germplasm. Reduced seed germination and field emergence potential associated with LP germplasm eliminates many individuals with the desired LP trait during early generation population development, making improvement of agronomic performance among LP lines difficult. Thus, development of resources for improved phenotyping, genotyping, and early generation population development will facilitate the commercialization of LP cultivars. Discovery of variation for field emergence potential among F2-derived LP families suggests the potential for using a pedigree method for early generation population development in LP germplasm, as it preserves diversity and allows selection for improved field emergence. Integration of markers into a pedigree method will be useful to breeder. An example is BARCSOYSSR_11_1495 with 90-93% selection efficiency in various V99-5089-derived populations. Another resource for improved LP selection is a time-efficient, high-throughput modified iron (Fe) colorimetric phytate assay that does not suffer from inorganic phosphorus (P) concentration interference. Together these tools will provide breeders more accurate selection of LP lines. / Master of Science
4

Disponibilidade de minerais, germinação e vigor de sementes de milho

Magalhães, Stefânia Caixeta [UNESP] 23 July 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:27Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-23Bitstream added on 2014-06-13T18:57:40Z : No. of bitstreams: 1 magalhaes_sc_me_jabo.pdf: 624079 bytes, checksum: 37a746a1dac768fd2d8f6dcc974b9b8d (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A maioria dos métodos utilizados para estimar o vigor de amostras de sementes são qualitativos, portanto sujeito a erros do avaliador e de interpretação dos resultados. Metodologias quantitativas podem constituir alternativas mais confiáveis. Este trabalho teve como objetivo verificar se os níveis de alguns minerais armazenados nas sementes e disponibilizados durante etapas iniciais do processo de germinação constituem indicadores sensíveis e confiáveis do nível de vigor de sementes de milho. Vinte lotes de milho foram avaliados pelos testes de germinação, de condutividade elétrica, frio e de emergência da plântula. Após 12 h, 24 h, 36 h e 48 h do início da germinação, foram avaliados também as concentrações de fósforo inorgânico (Pi), fósforo, cálcio, potássio e magnésio por meio das técnicas de análise de injeção em fluxo (FIA) e de espectrometria de emissão ótica acoplada a plasma de argônio induzido (ICP-OES). Para estas análises, os minerais foram extraídos de amostras moídas com água a 95ºC, agitadas por 30 minutos e centrifugadas. Concluiu-se que as concentrações de Pi, P, Ca, Mg e K, extraídos pelo método da água aquecida, em sementes de milho híbrido após determinados períodos de germinação, permitiram agrupar amostras de lotes de sementes de forma idêntica à permitida pelos resultados obtidos com vários testes utilizados para avaliar o nível de vigor de amostras de sementes. Nesse trabalho isso foi verificado pelas avaliações dos níveis de Pi após 12 h e 48 h, de P após 12 h, 36 h e 48 h, de Ca após 24 h, 36 h e 48 h, de Mg após 36 h e 48 h e de K após 36 h e 48 h de germinação. / Most of the traditional methods used for seed vigor evaluation are qualitative and, as such, prone to errors and results misinterpretation. Quantitative methods may constitute more reliable alternatives. The aim of this work was to verify if the concentrations of some minerals stored in the seeds and made available during the initial stages of the germination process constitute sensitive and reliable indicators of the level of corn seed vigor. Twenty seed lots were evaluated by means of the germination, electrical conductivity, cold and seedling field emergence tests. Additionally, the concentrations of inorganic phosphorus, phosporus, calcium, potassium and magnesium at 12 h, 24 h, 36 h and 48 h after the initiation of the germination process were also evaluated by means of the injection analysis in flow (FIA) and the spectrometry of optic emission coupled to plasma of induced argon (ICP-OES) techniques. For these analyses grinded seed samples were extracted with water at 95ºC, agitated for 30 minutes and centrifuged . It was concluded that the concentrations of Pi, P, Ca, Mg and K, extracted by the warm water method, in hybrid corn seeds after certain stages of the germination process, allowed the rating the of seed lots in a way similar to that obtained with the results of several other seed vigor tests. Specifically, this was achieved by evaluating the concentratrions of Pi after 12 h and 48 h, of P after 12 h, 36 h and 48 h, of Ca after 24 h, 36 h and 48 h, of Mg after 36 h and 48 h and of K after 36 h and 48 h after the beginning of the germination process.
5

Testes laboratoriais para a avaliação do desempenho germinativo no campo de sementes de lotes de soja (Glycine max (L.) Merrill

Salum, Juliane Dossi [UNESP] 10 August 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-10Bitstream added on 2014-06-13T19:16:23Z : No. of bitstreams: 1 salum_jd_me_jabo.pdf: 501902 bytes, checksum: 620f27e762303dc5c1baa13c0b5715ef (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / trabalho foi desenvolvido na Faculdade de Ciências Agrárias e Veterinárias do Câmpus de Jaboticabal (UNESP), na Escola Superior de Agricultura “Luiz de Queiroz” em Piracicaba (USP) e na Universidade Camilo Castelo Branco (UNICASTELO) em Fernandópolis, e teve por objetivo verificar a eficiência de alguns testes de vigor, conduzidos em laboratório, na previsão do desempenho germinativo de sementes de lotes de soja quando semeados sob condições de campo compatíveis com a prática agrícola. Foram avaliados nove lotes de sementes por meio dos seguintes testes laboratoriais: primeira contagem, padrão de germinação, envelhecimento acelerado, condutividade elétrica, frio, comprimento de plântula de acordo com procedimentos recomendados pela ISTA (1995), comprimento de plântulas de acordo com procedimentos recomendados pela ABRATES (1999), massa seca e emergência de plântulas no campo nas três localidades. O tempo de duração de cada teste foi também determinado. Os dados obtidos foram submetidos à análise de variância e as médias comparadas pelo teste Tukey a 5% de probabilidade. Dados da correlação entre resultados laboratoriais e desempenho germinativo no campo foram também determinados. Os resultados deste trabalho indicam que o produtor de sementes de soja dispõe de um número razoavelmente alto de testes entre os quais optar para avaliar, com um grau aceitável de confiança, o que esperar do desempenho germinativo de um lote de sementes quando semeado sob condições ambientais usuais para a prática agrícola. Os testes de maior precisão seriam os do envelhecimento artificial, o da condutividade elétrica e o do frio. Se, além da confiabilidade, ao produtor de sementes interessar também rapidez na obtenção de resultados, o teste da condutividade elétrica seria o mais... / This research work was carried out on the campi of Jaboticabal, a unit of the Paulista State University (UNESP), Piracicaba, a unit of the University of São Paulo (USP), and Fernandópolis, a unit of the Camilo Castelo Branco University, the three of them localities of the state of São Paulo, Brazil. The objective of this work was the evaluation of some laboratory tests for the analysis of soybean seeds quality as to their efficiency in forecasting seed lots germinative performance in the field. The environmental conditions in Jaboticabal, Piracicaba, and Fernandópolis were within the limits usually found under normal agricultural practice. Nine commercial soybean seed lots were used whose vigor levels previous laboratory tests showed to be high, medium, and low. The laboratory tests were the following: standard germination, germination first count, accelerated aging, electrical conductivity, cold, seedling length according to procedures found in ISTA (1995), seedling length according to procedures found in ABRATES (1999), seedling dry matter and field emergence at the three localities. The results indicate that soybean seed companies have a reasonably high number of laboratory tests among which to choose, all of them yielding highly trustable results. The accelerated aging, the electrical conductivity, and the cold tests would be those of the highest precision. The electrical conductivity test, in addition to being of high precision, was found to be the fastest one. In addition to those, the seed company still has a high number of tests from which to choose. Among them, those in which seedling length is measured were found to be more efficient than those in which seedling dry matter is measured. The seedling length tests have a duration between 128 and 151 hours. The measuring of seedling length according to... (Complete abstract, click electronic access below)
6

Disponibilidade de minerais, germinação e vigor de sementes de milho /

Magalhães, Stefânia Caixeta. January 2009 (has links)
Orientador: Francisco Humberto Dübbern de Souza / Banca: Roberval Daiton Vieira / Banca: Ana Dionísia da Luz Coelho Novembre / Resumo: A maioria dos métodos utilizados para estimar o vigor de amostras de sementes são qualitativos, portanto sujeito a erros do avaliador e de interpretação dos resultados. Metodologias quantitativas podem constituir alternativas mais confiáveis. Este trabalho teve como objetivo verificar se os níveis de alguns minerais armazenados nas sementes e disponibilizados durante etapas iniciais do processo de germinação constituem indicadores sensíveis e confiáveis do nível de vigor de sementes de milho. Vinte lotes de milho foram avaliados pelos testes de germinação, de condutividade elétrica, frio e de emergência da plântula. Após 12 h, 24 h, 36 h e 48 h do início da germinação, foram avaliados também as concentrações de fósforo inorgânico (Pi), fósforo, cálcio, potássio e magnésio por meio das técnicas de análise de injeção em fluxo (FIA) e de espectrometria de emissão ótica acoplada a plasma de argônio induzido (ICP-OES). Para estas análises, os minerais foram extraídos de amostras moídas com água a 95ºC, agitadas por 30 minutos e centrifugadas. Concluiu-se que as concentrações de Pi, P, Ca, Mg e K, extraídos pelo método da água aquecida, em sementes de milho híbrido após determinados períodos de germinação, permitiram agrupar amostras de lotes de sementes de forma idêntica à permitida pelos resultados obtidos com vários testes utilizados para avaliar o nível de vigor de amostras de sementes. Nesse trabalho isso foi verificado pelas avaliações dos níveis de Pi após 12 h e 48 h, de P após 12 h, 36 h e 48 h, de Ca após 24 h, 36 h e 48 h, de Mg após 36 h e 48 h e de K após 36 h e 48 h de germinação. / Abstract: Most of the traditional methods used for seed vigor evaluation are qualitative and, as such, prone to errors and results misinterpretation. Quantitative methods may constitute more reliable alternatives. The aim of this work was to verify if the concentrations of some minerals stored in the seeds and made available during the initial stages of the germination process constitute sensitive and reliable indicators of the level of corn seed vigor. Twenty seed lots were evaluated by means of the germination, electrical conductivity, cold and seedling field emergence tests. Additionally, the concentrations of inorganic phosphorus, phosporus, calcium, potassium and magnesium at 12 h, 24 h, 36 h and 48 h after the initiation of the germination process were also evaluated by means of the injection analysis in flow (FIA) and the spectrometry of optic emission coupled to plasma of induced argon (ICP-OES) techniques. For these analyses grinded seed samples were extracted with water at 95ºC, agitated for 30 minutes and centrifuged . It was concluded that the concentrations of Pi, P, Ca, Mg and K, extracted by the warm water method, in hybrid corn seeds after certain stages of the germination process, allowed the rating the of seed lots in a way similar to that obtained with the results of several other seed vigor tests. Specifically, this was achieved by evaluating the concentratrions of Pi after 12 h and 48 h, of P after 12 h, 36 h and 48 h, of Ca after 24 h, 36 h and 48 h, of Mg after 36 h and 48 h and of K after 36 h and 48 h after the beginning of the germination process. / Mestre
7

A Survey of the Agronomic and End Use Characteristics of Low Phytic Acid Soybeans

Averitt, Benjamin James 10 June 2016 (has links)
Phytic acid (PA) accounts for up to 75% of the P in soybean (Glycine max L. Merr.) seeds, but it is indigestible by mono- and agastric animals resulting in economic and environmental detriment. Soybean lines with genetically reduced PA contents have been developed using three distinct mutant alleles at the MIPS1, LPA1, and LPA2 genes resulting in up to a 75% reduction in PA. Low PA (LPA) soymeal-based feeds have been tested on several agricultural species and shown to reduce the P in the animal effluent, but they have not been tested on any aquacultural species. However, LPA soybean lines often exhibit low field emergence making them commercially inviable. The cause of this phenomenon is widely debated with possibilities ranging from increased disease pressure to decreased seedling vigor. The objectives of this research were to 1) enhance field emergence of LPA soybean varieties through pre-planting seed treatments, 2) study the impact of the LPA mutant alleles on agronomic, quality, and seed composition traits, and 3) design a low-error method for studying the effect of LPA soymeal-based feeds on aquatic animals using Pacific White Shrimp (Litoenaeus vannamei). These results describe a variety of agronomic and genetic strategies with which the low field emergence of LPA soybeans can be addressed, reveal a heretofore not reported interaction between the mips1 and lpa2 alleles to further increase the digestibility of soymeal, and a possible method for studying LPA soymeal based feed on aquacultural animals. / Master of Science
8

Ambiguity and intermediation in the early moments of market formation : the case of the UK social investment market

Casasnovas, Guillermo January 2016 (has links)
Markets are arenas of social interaction for the exchange of products and services that are embedded in specific networks, cultures, and political relations. The study of how new markets come into being is a lively area of scholarly debate, and the purpose of this thesis is to shed light on the dynamics of these early moments of market formation. These nascent markets are characterized by the lack of shared meanings and settled rules around their participants, processes, and infrastructure. I approach them with arguments from economic sociology and from theories of organizations and institutions. The empirical context is a longitudinal study of the UK social investment market from 2000 to 2015, a field that intersects the social, financial, and public sectors. Social investment refers to the combination of financial returns and social impact, but the contest over its meaning and practice is itself a part of this analysis. The core data collection is based on interviews, reports, field events, and online sources, which provide an empirical basis to understand the social, cultural, and political processes that are shaping this market. I build on different traditions in the sociology of markets to explore changes over time in the rules, identities, practices, and dominant actors during the early moments of the UK social investment market. My first main finding is that the initial period of uncontested ambiguity is followed by efforts from mainstream organizations to reduce that ambiguity by reshaping rules and practices. This then results in a period of collaborative contestation, where peripheral actors challenge the core features of the field and hinder the path to stability. The second finding is about the role played by intermediary organizations in nascent markets, which consists of building the market infrastructure by connecting actors, developing a language, and establishing rules and practices. These findings point to the importance of theorizing about ambiguity in the early moments of markets. I contribute to this endeavor by specifying some of its features and dynamics, and by emphasizing the centrality of intermediation. I also further our understanding of those markets that span across the worlds of business, policy, and civil society.
9

Kvalitet semena samooplodnih linija kukuruza različitih grupa zrenja i genetičke osnove / Seed quality of ZP maize inbred lines of different maturity groups and genetic background

Milivojević Marija 30 September 2016 (has links)
<p>U radu su sprovedena ispitivanja kvaliteta semena samooplodnih linija kukuruza stvorenih u Institutu za kukuruz &bdquo;Zemun Polje&ldquo; razliĉitih grupa zrenja i genetiĉke osnove. U laboratorijskim i poljskim uslovima utvrĊena je klijavost i vigor semena iz 2011. nakon ĉetiri godine ĉuvanja u kontrolisanim uslovima (18 &deg;C i 60% RH) i semena iz 2014. nakon godinu dana ĉuvanja na 5 &deg;C i 60% RH.<br />Cilj je bio utvrditi tolerantnost odabranih linija na niske temperature prilikom klijanja i nicanja, dugoveĉnost semena u kontrolisanim uslovima ĉuvanja, genetiĉku divergentnost linija primenom proteinskih markera i proceniti uticaj genetiĉke osnove na kvalitet semena.<br />U laboratoriji za ispitivanje semena praćeni su sledeći parametri kvaliteta: vitalnost, klijavost, energija klijanja, dužina klijanaca, vigor ispitan tetrazolium testom, hladnim testom, testom ubrzanog starenja, testom pojave primarnog korena i testom provodljivosti.<br />Primenom vigor testova na semenu dva nivoa starosti omogućena je bolja klasifikacija linija u pogledu kvaliteta, nego standardnim testom klijavosti. Rezultati rada ukazuju da su hladni test i test ubrzanog starenja najpogodniji za procenu vigora semena u laboratoriji, s tim da je hladni test bolji pokazatelj nicanja u polju.<br />Ispitivane samooplodne linije pokazale su dobru sposobnost oĉuvanja kvaliteta semena kao i visok nivo toleratnosti na niske temperature u toku klijanja i ranog porasta biljaka. Kontrolisani uslovi ĉuvanja na 18 &deg;C omogućili su da se klijavost i vigor semena u ispitivanom periodu, održi na visokom nivou.<br />Dužina vegetacije samooplodnih linija nije imala znaĉajan uticaj na klijavost i vigor semena. Kvalitet semena ispitivanih samooplodnih linija je prvenstveno bio pod uticajem genetiĉke osnove. Linije poreklom od Lancaster populacije imale su slabiji vigor u odnosu na linije BSSS i Iowa Dent porekla.<br />U radu je potvrĊeno da vigor testovi imaju važnu ulogu u ispitivanju kvaliteta semena samooplodnih linija kukuruza. Dobijeni rezultati direktno se mogu iskoristiti u oplemenjivaĉkim programima u cilju pobolj&scaron;anja klijavosti i vigora semena. Ostvareni rezultati ukazuju da su informacije o genetiĉkom poreklu samooplodnih linija važan indikator vigora semena. Pored podataka o genetiĉkom poreklu linija veliki znaĉaj ima karakterizacija putem biohemijskih markera.</p> / <p>The extensive seed quality evaluations of maize inbred lines developed at the Maize Research Institute Zemun Polje of different maturity groups and genetic background were conducted. In laboratory and field conditions germination and vigour of seed produced in 2011 and 2014 was determined, after four years of storage at 18 &deg;C, 60% RH and one year of storage at 5 &deg;C, 60% RH, respectively.<br />The objective of this research was to determine the chilling tolerance of selected inbred lines during germination and emergence, seed longevity under controlled storage conditions, genetic divergence determined by biochemical markers and to assess the impact of the genetic background on seed quality.<br />Following seed quality parameters were tested: viability, germination, seedling length and vigour examined by cold test, accelerated ageing test, tetrazolium test, radicle emergence test and conductivity test.<br />Vigour tests provided a better classification of inbred lines of different seed age in terms of quality than standard germination test. Obtained results show that cold test and accelerated aging test are the most suitable for assessing seed vigour in the laboratory, but cold test is a better indicator of field emergence.<br />Tested maize inbred lines showed good seed storability and high level of chilling tolerance during germination and early growth of plants. Controlled storage conditions at 18 &deg;C, have enabled that germination and seed vigor remains at the high level in the examined period.<br />Seed germination and vigour of maize inbred lines were not affected by length of vegetation. Seed quality was primarily influenced by genetic background of tested inbred lines. Inbred lines originating from Lancaster populations had lower vigour compared to lines with BSSS and Iowa Dent origin.<br />This research confirmed that vigor tests play an important role in seed quality testing of maize inbred lines. Results of this work can be directly used in breeding programs to improve germination and seed vigour. Achieved results indicate that information about the genetic origin of inbred lines is an important indicator of seed vigour. Finally, data emphasized the importance of inbred line characterization by biochemical markers in addition to genetic origin information.</p>
10

Determining seed vigour in selected Brassica species

Leeks, C. R. F. January 2006 (has links)
Variables for the accelerated ageing (AA) test, methods for reducing fungal contamination during the AA test, using the conductivity test as a vigour test, the effect of seed size on seed vigour and the relationship between laboratory test results and field perfonnance in selected Brassica spp were investigated. In the first experiment, three seed lots of turnip rape hybrid (B. rapa x campestris), turnip (B. campestris) and forage rape (B. napus); and seven seed lots of Asian rape (B. napus), six seed lots of Asian kale (B. oleraceae var. alboglabra L.) and five seed lots of choisum (B. rapa var. pekinensis) with germinations above 90% were aged at two different temperatures (41 and 42°C ± 0.3°C) and three ageing times (24, 48 and 72 ± 15 minutes). The second experiment was divided into three sections. In the first, the same seed lots and species were aged at one temperature (41°C) and time (72 h), but either 40 ml of saturated salts; KCl (83%RH), NaCl (76%RH), NaBr (55%RH); or distilled water (96%RH) were used as the ageing solutions. In the second, one turnip rape hyprid seed lot was aged at three temperatures (41, 42 and 45°C) and two times (72 and 96h), again using the three saturated salts and distilled water as ageing solutions. In the third, three turnip rape hybrid seed lots and three Asian kale seed lots were surface sterilised (1 % sodium hypochlorite) prior to ageing at one temperature (41°C) and time (72 h). In the third experiment, the same species and seed lots used in experiment one at their original seed moisture content (SMC) were tested for conductivity after soaking in deionised water for 4, 8, 12, 16, 20 and 24 h. They were then re-tested after the SMC had been adjusted to 8.5%. In the fourth experiment, three seed lots of forage rape and three seed lots of Asian kale were graded into three seed size categories; large (retained on a 2.0 mm screen), medium (retained on a 1.7 mm screen) and small (passed through a 1.7 mm screen). Graded seeds were then tested for standard germination, AA (41°C/48 h) and conductivity (measured at 16 and 24 h). In the final experiment, the relationships between laboratory tests for the six species (each consisting of three seed lots), field emergence from three sowings, and cold room emergence were evaluated. Both time and temperature influenced post-AA germination. Increasing the ageing period from 48 to 72 hours at 41°C, and 24 to 48 hours at 42°C resulted in decreased mean germination percentage for all species but not always clear separation of seed lots. While there were sometimes few differences between ageing at 41°C and 42°C, the former is preferred because it is already the temperature used for other species. For Asian rape, choisum and turnip, the previously recommended testing conditions of 41°C/72 h provided good seed lot separation, but for Asian kale and turnip rape hybrid, AA testing at 41°C/48 h provided better results. Seed moisture content after ageing ranged from 29-37% depending on species. Fungal growth on seeds during the ageing period appeared to reduce post-ageing germination in some seed lots . Substituting saturated salts for distilled water did not stress seed lots in the AA test, due to the lowered RH%, the exception being seed lots 1210 and 1296. For forage and Asian species, seed lot germination mostly remained above 90% when aged for 72 h at lowered RH%. Increasing the ageing duration from 72 to 96 hours resulted in some decreases in post-AA germination but no clear separation of seed lots. Surface sterilising the seeds prior to the AA test resulted in a lower incidence of contaminant fungi which was associated with a lower percentage of abnormal seedlings. The conductivity test was mostly able to identify vigour differences among forage and Asian vegetable brassica seed lots. Differences in conductivity readings were observed among seed lots in all species. Increasing the period of imbibition resulted in increased conductivity from most seed lots but radicle emergence occurred after 16-20 h of imbibition. Variation was observed in the time to reach 95% maximum of the imbibition curve for most species. Conductivity readings at 16 h would avoid possible influences of radicle emergence on results. Adjusting the SMC to 8.5% resulted in reduced variation in conductivity among replicates of seed lots, due to a reduction in imbibition damage. Seed size had a significant effect on both post-AA germination and conductivity results. In forage rape, large size seeds had higher post-AA germination cf. medium cf. small size seeds. In Asian kale, large size seeds had higher post-AA germination compared with small size seeds. For both forage rape and Asian kale, large size seeds had lower conductivity readings cf. small size seeds. The correlation analyses demonstrated significant relationships between AA testing and field emergence parameters (percentage emergence, emergence index and emergence rate). Significant relationships were also observed between conductivity testing and these field emergence parameters. Based on the correlation analysis, AA testing at 41°C/48 hand/or 42°C/48 h could be recommended to be used as an AA test for turnip and Asian rape; and 41°C/48 hand/or 41°C/72 h for Asian kale and choisum. Based on the correlation analysis, conductivity testing at 16 h can be used to predict the field emergence potential of forage and Asian vegetable seed lots. Vigour tests were consistently able to provide better indicators of field perfonnance than the standard germination test, although these relationships did vary with the different field sowings.

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