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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.
21

Sistema informatizado para rastreabilidade na produção de sementes / Computerized system for traceability in seed production

Marcolin, Lucas 03 March 2011 (has links)
Made available in DSpace on 2014-08-20T13:44:45Z (GMT). No. of bitstreams: 1 dissertacao_lucas_marcolin.pdf: 1664329 bytes, checksum: d914534bea39a20ab2fb8082ed199d29 (MD5) Previous issue date: 2011-03-03 / The growing demand of consumer markets for seed quality and safety to the producer and consumer is ordering from the production sector a continuous adaptation. Food safety has become an important attribute of food quality. The traceability is in line with this view, since it integrates the entire production chain in a monitoring and certification system. Traceability programs for the productive chain are essential for logistics and management of seed production. The aim of this study was to develop and validate an efficient and effective traceability system for seed production, through a scheme of software, in order to ensure the quality and safety of the products obtained, as well as an important management tool, making the productive chain more competitive in the market. In addition to an extensive literature review, it was also made a partnership with the company Checkplant Traceability Systems LTD, in order to assist in the software scheme that they have already developed for fruit producers and many others. Furthermore, interviews with companies, researchers and seed producers from the south region helped to collect necessary data for the proposed software and to understand the obstacles and critical points of the productive chain. It was presented and tested with the users, the system screens which can work for them, containing the field part (record of field activities, its settings and reports) and the post-harvest stage (record of the activities in the Seed Processing Unit, reports, etc.), paying attention to what should be enhanced to the system implementation. It was observed that the proposed system, based on what happens with fruit producers, it is perfectly adaptable and feasible for seed producers, ensuring, besides of traceability, an important management tool. / A crescente exigência dos mercados consumidores por sementes de qualidade e com segurança ao produtor e consumidor vem ordenando ao setor produtivo uma contínua adaptação. A segurança dos alimentos tem se tornado um importante atributo de qualidade alimentar. A rastreabilidade vem ao encontro com esta perspectiva, uma vez que integra toda a cadeia produtiva em um sistema de monitoramento e certificação. Programas de rastreabilidade para as etapas da cadeia produtiva são essenciais para a logística e o gerenciamento da produção de sementes. O objetivo deste estudo foi propor e validar um sistema eficiente e eficaz de rastreabilidade para a produção de sementes, por meio de um esquema de software, a fim de assegurar a qualidade e segurança dos produtos obtidos, além de uma importante ferramenta de gestão, tornando a cadeia produtiva mais competitiva no mercado. Além de extensa revisão bibliográfica, foi feita também parceria com a empresa Checkplant Sistemas de Rastreabilidade LTDA, afim de auxiliar no esquema de software que os mesmos já desenvolvem para produtores de frutas e tantos outros. Além disso, entrevistas com empresas, produtores e pesquisadores de sementes da região Sul ajudaram para a coleta de dados necessários para a proposta do software e, para entender os entraves e pontos críticos da cadeia produtiva. Foi apresentado e testado junto aos usuários as telas de sistema que podem funcionar para os mesmos, constando a parte de campo (registro de atividades de campo, suas configurações e relatórios) e a etapa pós-colheita (registro das atividades na UBS, relatórios, etc.), prestando atenção ao que deve ser aprimorado para implementação do sistema. Observou-se que a proposta de sistema, baseado no que ocorre com os produtores de frutas, é perfeitamente adaptável e viável para produtores de sementes, assegurando, além da rastreabilidade, em si, uma importante ferramenta de gestão.
22

Local Adaptation of Blue Penstemon: Molecular and Morphological Characterizations of a Potential Restoration Species for the Northern Basin and Range and Snake River Plain

Stettler, Jason Mark 05 April 2022 (has links)
Penstemon is one of North America's largest endemic genera with over 280 described species. These species are distributed throughout most of North America from the Arctic northern latitudes to tropics of Central America. The genus has historically been divided into six subgenera, but has recently been reorganized into two subgenera following some recent phylogenetic studies. I made a comprehensive assessment of the Penstemon genus' geographic distribution utilizing herbaria databases by ecoregion to discuss the general ecologic adaptations of each historic subgenera. I also assessed the Penstemon genus' bee pollinator diversity utilizing online databases of bee specimen collections associated with Penstemon flowers. I investigated the efficacy of utilizing the plastid genomes (plastomes) of 29 species in the Lamiales order, including five newly sequenced Penstemon plastomes, for analyzing phylogenetic relationships and resolving problematic clades. I compared whole-plastome based phylogenies to phylogenies based on individual gene sequences (matK, ndhF, psaA, psbA, rbcL, rpoC2, and rps2) and concatenated sequences. I found that my whole-plastome based phylogeny had higher nodal support than all other phylogenies, which suggests that it provides greater accuracy in describing the hierarchal relationships among taxa as compared to other methods. I found that the genus Penstemon forms a monophyletic clade sister to, but separate from, the Old World taxa of the Plantaginaceae family included in our study. My whole-plastome based phylogeny also supports the rearrangement of the Scrophulariaceae family and improves resolution of major clades and genera of the Lamiales. I evaluated 16 accessions of P. cyaneus with 14 accessions of closely related Penstemon species in common garden in two distinct environments in Aberdeen, ID and Provo, UT during 2018 and 2019. I evaluated the accessions for key commercial seed production traits including survival, plant height, number of stems, and seed production. Both common gardens received supplemental irrigation during 2018, but I withheld irrigation during 2019. Plant survival in our Aberdeen, ID site was not significantly different between years, but survival was a significantly lower in 2019 than in 2018 at our Provo, UT site. The mean survival for P. cyaneus accessions ranged from 56% to 94%, and the mean seed production ranged from 91.2 kg/ha to 397.6 kg/ha. I recommend developing a commercial seed source derived from pooling germplasm of six accessions (PECY3-367, PECY3-371, PECY3-376, PECY3-443, PECY3-457, and PECY3-458). These accessions had mean survival rates of 82-94%, and seed production of 196.2-397.6 kg/ha.
23

Studies on the development of a novel seed production technology for cabbages using the grafting-induced flowering with radish rootstocks / ダイコン台木への接ぎ木による花成誘導を利用したキャベツの新規採種技術の開発に関する研究

Motoki, Ko 25 July 2022 (has links)
京都大学 / 新制・論文博士 / 博士(農学) / 乙第13498号 / 論農博第2902号 / 新制||農||1093(附属図書館) / 学位論文||R4||N5404(農学部図書室) / 京都大学大学院農学研究科農学専攻 / (主査)教授 中﨑 鉄也, 教授 土井 元章, 教授 田尾 龍太郎 / 学位規則第4条第2項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
24

SILVICULTURAL TREATMENT EFFECTS ON OAK SEED PRODUCTION AND ACORN WEEVIL DIVERSITY IN SOUTHEASTERN OHIO

Lombardo, Jeffrey A. 20 April 2007 (has links)
No description available.
25

Herbicide-based Weed Management Systems for Potato (<i>Solanum tuberosum</i>) and Wheat (<i>Triticum aestivum</i>) and Growth and Reproductive Characteristics of Smooth Pigweed (<i>Amaranthus hybridus</i>)

Bailey, William Anthony 26 August 2002 (has links)
Integrated weed management involves the utilization of weed biology principles to develop effective and economical control strategies. This research involved investigations of herbicide-based weed management programs in potato (<i>Solanum tuberosum</i> L.) and winter wheat (<i>Triticum aestivum</i> L.) as well as investigations of the biological characteristics of smooth pigweed (<i>Amaranthus hybridus</i>), a troublesome species in many crops. Sulfentrazone is an herbicide registered for use in soybean [<i>Glycine max</i> (L.) Merr.] and tobacco (<i>Nicotiana tabacum</i> L.) that may also have potential for use in potato. In field experiments, potato tolerance to preemergence (PRE) applications of sulfentrazone at rates up to 0.21 kg/ha was similar to that from the registered herbicides metribuzin, metolachlor, or metribuzin plus metolachlor PRE. Potato generally did not tolerate sulfentrazone applications to foliage. Sulfentrazone effectively controlled common lambsquarters (<i>Chenopodium album</i> L.) at rates as low as 0.11 kg/ha and also controlled several annual grasses at higher application rates, but was slightly less effective on jimsonweed (<i>Datura stramonium</i> L.) and ineffective on common ragweed (<i>Ambrosia artemisiifolia</i> L.). Potato tuber yield and grade from sulfentrazone PRE applications was similar to yield of potato treated with registered herbicides. Laboratory research was also conducted to determine the mechanism of sulfentrazone selectivity between potato (a tolerant species), common lambsquarters (a sensitive species), and jimsonweed (an intermediate species). After 48 h root exposure to [14C] sulfentrazone, absorption by common lambsquarters was nearly two-fold that of jimsonweed and three-fold that of potato. Both weed species also exhibited nearly a two-fold increase in sulfentrazone translocation from roots to shoots compared to potato. Since the site of action of sulfentrazone, protoporphyrinogen oxidase, is located in shoot tissue, translocation to shoots is essential for sulfentrazone toxicity. Therefore, the proposed primary mechanisms of selectivity between these species are differential root absorption and differential translocation. Experiments were also conducted to investigate the potential of the experimental herbicide AE F130060 03 for Italian ryegrass (<i>Lolium multiflorum</i> Lam.) control in winter wheat. In laboratory research, foliar absorption of AE F130060 03 in Italian ryegrass was at least three times that in wheat. Additionally, herbicide metabolism was greater in wheat, particularly in wheat treated with the herbicide safener AE F107892. In field experiments, AE F130060 03 was as effective as diclofop-methyl for control of diclofop-sensitive Italian ryegrass and more effective than diclofop-methyl and all other herbicides tested for control of diclofop-resistant Italian ryegrass. Although wheat injury from AE F130060 03 was greater than from other herbicides, wheat recovered and yields were not affected. Postemergence AE F130060 03 applications controlled Italian ryegrass from emergence until the end of tillering, but applications made to four- to five-tiller Italian ryegrass resulted in the least amount of new Italian ryegrass emergence following application. To further define the utility of AE F130060 03 in winter wheat, ten wheat cultivars adapted to Virginia were evaluated for tolerance to AE F130060 03. Biomass production between cultivars was not influenced by AE F130060 03 application in the greenhouse, although slight yield decreases due to herbicide application were found in FFR 518, Coker 9663, AgriPro Patton, and VA98W593 under weed-free conditions in the field. Greenhouse, growth chamber, and field experiments were also conducted to investigate growth and seed production of one imidazolinone-susceptible (S) and five -resistant (R1, R2, R3, R4, and R5) smooth pigweed biotypes. Although the S biotype produced more total biomass than four of the five R biotypes, R4 displayed a more rapid growth rate at 3 to 5 wk after planting and a faster germination rate than S and all other R biotypes. Seed production in R4 was similar to S and greater than in all other R biotypes. Early rapid growth in R4 did not translate into increased biomass accumulation compared to S at the conclusion of the experiments. / Ph. D.
26

The influence of nutrient solutions on growth, seed production and seed quality of broccoli (Brassica oleracea L. var. italica Plenck)

Du Randt, Marius Louis 03 1900 (has links)
Thesis (MScAgric (Agronomy))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Little is known about the nutrient requirements of broccoli grown for seed production. During 2006 and 2007 broccoli were grown for seed production in sand bags in a net structure, using a drain to waste hydroponic system. The experimental design was a randomized complete block with seven treatments replicated in four blocks. In 2006 seven nutrient solution treatments were tested. The Standard solution based on Steiner’s universal solution was compared with different levels of N, S, K and Ca with regard to the effect on total biomass, nutrient concentration, nutrient assimilation, seed yield and quality. No significant differences in total biomass produced were found. Total dry mass increased by 225% from the mature head stage until harvest of seed. Nutrient concentration in plant samples were not influenced by treatments except where low levels of K and S in nutrient solutions led to significantly lower levels of K and S concentrations. The total assimilation of elements were calculated to determine the effect of the much longer growth period needed for seed production in comparison to normal head production on nutrient requirements. Major elements assimilated ha-1 was: N 173.0 kg, P 35.5 kg, K 348.4 kg, Ca 114.7 kg, Mg 30.5 kg, S 42.2 kg. The seven treatments used during 2007 included three of the treatments which were used in 2006 as well as treatments with foliar sprays containing Ammonium Nitrate and Calcium Metalosate. The standard solution treatment was also used in 2007 to compare results with 2006. Plant analysis done on plants from the standard solution (2006 & 2007) showed similar trends. As the plants developed towards maturity there was a relative increase in concentration in the top plant parts (pods, flowers and stems) for Ca, Mg and S. Contrary, N and P concentration declined. The minor elements, Fe, Mn and B also increased in concentration in the top plant parts at harvest indicating a strong relative flow of these elements to the top plant parts towards maturation. Concentration values of major elements in plant samples were generally different when the two years were compared. Element concentrations in the seed pods were in general higher than in the rest of the plant indicating the pods as a strong sink on the plants. During both years the two best nutrient solutions for yield were the same, namely the Standard solution and Standard - K which contain low levels of K. During 2006 no significant differences in seed quality were found. During 2007 no significant differences were found for seed quality measurements, except for size (of the cotyledons). The results indicate that no special adjustments need to be made to the Standard solution in order to produce good broccoli seed yield of good quality. As substantial differences in nutrient solution composition did not significantly affect the quality of broccoli seed produced. Seed yield was however significantly affected by nutrient solution composition. Key words: Brassica seed, broccoli seed, seed production, broccoli nutrition, hydroponic production, broccoli production, nutrient assimilation. / AFRIKAANSE OPSOMMING: Min inligting is bekend rakende die voedingsbehoeftes van brokkoli wat gekweek word vir saadproduksie. Gedurende 2006 en 2007 is brokkoli gekweek vir saadproduksie in sakke sand in ‘n net struktuur met ‘n oop hidroponiese besproeiingstelsel. Die proefontwerp was ‘n ewekanisige geheel blok met sewe behandelings wat ewekansig binne bloke toegeken is en herhaal is in vier blokke. Sewe voedingsmengsel behandelings is gedurende 2006 toegepas. Die Standaard mengsel is geskoei op Steiner se universele mengsel en dit is vergelyk met verskillende vlakke van N, S, K en Ca t.o.v. die invloed daarvan op biomassa produksie, voedingselement konsentrasie, voedingselement assimilasie, saad opbrengs en saad kwaliteit. Biomassa geproduseer het nie wesenlik verskil nie. Totale droë massa het met 225% toegeneem vanaf die volwasse kop tot die oes stadium. Die konsentrasie van voedings elemente in plant monsters is nie beïnvloed deur behandelings nie behalwe in gevalle waar lae konsentrasies van K en S in die voedingsmengsels gelei het tot lae konsentrasies van K en S in plantontledings. Die totale opname van voedingselemente is bereken om die effek van die veel langer groeiperiode wat benodig word vir saadproduksie in vergelyking met normale kop produksie te bepaal t.o.v. voedingselement behoefte. Makro element opname per hektaar was as volg: N 173.0 kg, P 35.5 kg, K 348.4 kg, Ca 114.7 kg, Mg 30.5 kg, S 42.2 kg. Die sewe behandelings van 2007 het drie behandelings van 2006 ingesluit asook behandelings van blaarbespuitings met Ammonium Nitraat en Kalsium Metalosaat. Die Standaard voedingsmengsel is weer gebruik ten einde die resultate van 2006 en 2007 te vergelyk. Voedingselement ontledings op plante van die Standaard mengsel (2006 & 2007) is vergelyk en het soortgelyke tendense aangedui. Soos wat plante ontwikkel het na volwassenheid was daar ‘n relatiewe toename in konsentrasie in die boonste plant dele (peule, blomme en stele) van Ca, Mg en S. In teenstelling hiermee het die konsentrasies van N en P afgeneem. Die mikro elemente Fe, Mn en B het ook in konsentrasie toegeneem in die boonste plant dele teen oes wat daarop dui dat daar ‘n sterk relatiewe vloei van hiedie elemente na die boonste plant dele plaasvind met volwasse wording. Die konsentrasie vlakke van makro elemente in plantontledings het in die algemeen wesenlik verskil tussen die twee jare. Die voedingselement konsentrasies was in die algemeen hoër in die saad peule as in die res van die plant wat daarop dui dat die peule as ‘n sterk sink op die plant funksioneer. In beide jare was die hoogste opbrengs afkomstig van die Standaard voedingsmengsel en die Standaard – K mengsel wat lae vlakke van K bevat het. Gedurende 2006 is geen wesenlike verskille in saadkwaliteitsnorme gevind nie. Soortgelyke resultate is gevind in 2007 behalwe vir grootte van die kiemblare. Die resultate dui daarop dat dit nie nodig is om die Standaard voedingsmengsel samestelling te verander ten einde goeie opbrengs saad van goeie gehalte te produseer nie. Wesenlike verskille in voedingsmengsels het geen invloed op die kwaliteit van brokkoli saad gehad nie. Saad opbrengs is egter wesenlik beïnvloed deur die samestelling van die voedingsmengsels. Sleutel woorde: brassica saad, brokkoli saad, saad produksie, brokkoli voeding, hidroponiese produksie, brokkoli produksie, voedingstof assimilasie.
27

The effects of defoliation on seasonal growth dynamics, the importance of internal nitrogen-recycling and the availability of soil nutrients: implications for the invasive potential of Buddleia davidii (Franch.)

Thomas, Marc Merlin January 2007 (has links)
ABSTRACT Assessing the impact of herbivory on plant growth and reproduction is important to predict the success of biocontrol of invasive plants. Leaf area production is most important, as photosynthesis provides the foundation for all plant growth and fitness. High levels of defoliation generally reduce the productivity of plants. However, leaf area production fluctuates during the season and compensational growth may occur, which both complicate accurate estimations of defoliation impacts. Under field conditions the interaction with neighbouring species and the availability of soil nutrients need to be assessed in order to gauge long term effects of weed invasions on natural environments. In this thesis I have investigated seasonal leaf area dynamics in Buddleia davidii following repeated artificial defoliation, to quantify compensational leaf production and to understand the regulatory mechanisms involved. The impact of defoliation on photosynthesis, seed production, germination and nitrogen translocation patterns were analysed. Finally, possible facilitation between B. davidii and a native nitrogen fixer, Coriaria arborea, and the impact of B. davidii on soil nutrient availability were investigated. In defoliated B. davidii, increased node production (34%), leaf size (35%) and leaf longevity (12%) resulted in 52% greater total emergent leaf area in the short term. However, with time and diminishing tissue resources the compensation declined. No upregulation of photosynthesis was observed in pre-existing leaves. Compensational leaf area production occurred at the expense of reproduction but the germination capacity of individual seeds was unaffected. In B. davidii, nitrogen reserves are stored in old leaves. Thus, the defoliation-induced decline in tissue reserves led to changes in the remobilisation pattern and increased the importance of soil uptake but biomass production especially that of roots had declined significantly (39%). Slight facilitation effects from the neighbouring nitrogen fixer and VA-mycorrhizae were observed on B. davidii in the field, while its impact on soil chemistry during spring was negligible. Defoliation of B. davidii resulted in priority allocation of resources to compensational leaf growth and a concomitant reduction in flower and seed production. The compensational leaf production greatly increased the demand for nitrogen, while continued leaf removal decreased the pool of stored nitrogen. This led to changes in nitrogen remobilisation and an increased importance of root uptake. However, the significant decline in root growth will likely impair adequate nutrient uptake from the soil, which is especially important where B. davidii invades nutrient poor habitats and will increase the success of biocontrol of the species. While mycorrhizae increase nutrient accessibility for B. davidii, it is likely that the additional stress of defoliation will negate the small facilitative effects from nitrogen-fixing species like C. arborea. This research provides new insights into the mechanisms regulating leaf area dynamics at the shoot level and systemic physiological responses to defoliation in plants, such as nitrogen translocation. The compensation in leaf area production was considerable but only transitory and thus, the opportunity to alleviate effects of leaf loss though adjustment of light capture limited. However, to ascertain that photosynthesis at whole plant level does not increase after defoliation, more detailed measurements especially on new grown leaves are necessary. In general, defoliation had greatly reduced plant growth and performance so that an optimistic outlook for controlling this species can be given. Conclusions about the wider impacts of B. davidii on soil chemistry and community function will require further research.
28

PRODUTIVIDADE DE SEMENTES DE CEBOLA EM FUNÇÃO DE CULTIVARES E DOSES DE NITROGÊNIO EM COBERTURA NA REGIÃO DE PONTA GROSSA – PR / ONION SEED YIELD IN FUNCTION OF CULTIVARS AND LEVEL OF NITROGEN FERTILIZER IN COVERING IN PONTA GROSSA - PR

Olinik, Jean Ricardo 17 February 2009 (has links)
Made available in DSpace on 2017-07-25T19:29:41Z (GMT). No. of bitstreams: 1 Jean Ricardo Olinik.pdf: 1030936 bytes, checksum: f241f2d3aa5f1a75c61a57ee3883634b (MD5) Previous issue date: 2009-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The experiment was ram in Ponta Grossa (PR) with the aim to evaluate onion seed yield of cultivars Bola Precoce e Crioula in function of four levels of nitrogen in covering. The bulbs used in the experiment weighed approximately 80 g each, and were vernalized before planting in cold room at 43 days at a temperature of 5 ± 1 º C and relative humidity of 80%. The experimental design was a randomized blocks with four replications. The treatments followed a split-plot design, being two cultivars (Bola Precoce e Crioula) and four levels of nitrogen in covering (0, 60, 120 and 180 kg ha-1). Bulbs were planted in 07/06/07. Nitrogen fertilization was applied in covering with urea at 55 days after planting. The harvest were realized at 192 days after planting. The following characteristics were evaluated: number of flower stems, fertilized flowers, no fertilized flowers and total flowers per plant, number of seeds per plant and per capsule, number of seeds per plant obtained from capsules with 1, 2, 3, 4, 5 and 6 seeds, weight of 1000 seeds, seed weight per plant and productivity. For the characteristics evaluated, Crioula was superior compared than Bola Precoce, with an increase of 43% in seed yield. Nitrogen fertilization is an important management in onion seed production; compared to control, it was the highlight for a level of 120 kg ha-1 with yield of 558.64 kg ha-1. / O experimento foi realizado na Fazenda Escola, pertencente à Universidade Estadual de Ponta Grossa, localizada em Ponta Grossa – PR, com o objetivo de avaliar a produtividade de sementes de cebola das cultivares Bola Precoce e Crioula em função de quatro doses de nitrogênio em cobertura. Os bulbos utilizados no experimento pesavam aproximadamente 80 g cada, sendo vernalizados antes do plantio em câmara fria por 43 dias a uma temperatura de 5 ±1 ºC e umidade relativa de 80%. O delineamento experimental utilizado foi o de blocos ao acaso com quatro repetições. Os tratamentos foram arranjados em parcelas subdivididas, sendo as parcelas constituídas de duas cultivares (Bola Precoce e Crioula) e as subparcelas de quatro doses de nitrogênio em cobertura (testemunha (0), 60, 120 e 180 kg ha-1). O plantio foi realizado no dia 07/06/07. A adubação nitrogenada em cobertura com uréia foi realizada aos 55 dias após o plantio. A colheita foi realizada aos 192 dias após o plantio. As seguintes características foram avaliadas: número de hastes florais, flores fecundadas, não fecundadas e totais por planta, número de sementes por planta e por cápsula, número de sementes por planta obtidas de cápsulas com 1, 2, 3, 4, 5 e 6 sementes, massa de 1000 sementes e sementes por planta e produtividade. Para as características avaliadas, Crioula foi superior em relação à Bola Precoce, com um incremento de 43% na produtividade de sementes. A adubação nitrogenada é um importante manejo no processo de produção de sementes de cebola;comparada à testemunha, coube o destaque para a dose de 120 kg ha-1, com produtividade de 558,64 kg ha-1.
29

Farmers' perceptions of community-based seed production schemes in Polokwane and Lepelle-Nkumpi Local Municipalities, Limpopo

Phala, Mahlatse January 2019 (has links)
Thesis (M. A. Agricultural Management (Agricultural Extension)) -- University of Limpopo, 2019 / Smallholder farmers’ need for regular supply of adequate, quality and affordable seed led to the establishments of Community-Based Maize Seed Production Schemes (CBSPSs) in most developing countries, including South Africa. In view of the important influence of perception on the adoption and continued use of an innovation, this study was undertaken to evaluate farmers’ perceptions of CBSPSs in Polokwane and Lepelle-Nkumpi Local Municipalities of Limpopo province. The conceptualization of perception used in this study was based on the Düvel (1991) framework. The evaluation focused on whether planting the scheme’s main product, improved Open-Pollinated Varieties (improved OPV maize) seed meets farmers’ needs based on their perceptions and the extent of farmers’ planting of improved OPV maize. A census approach was used in view of the small numbers of seed producers in the schemes; all scheme members (50) were, therefore, interviewed between 27 March and 21 April 2017. To allow for comparison, an equal number of farmers (50) who were not members of the scheme were also interviewed. Data was collected from farmers using a semi-structured questionnaire. Descriptive and inferential statistics were applied to analyze the data using SPSS software. A binary logistic model was used to analyze factors that influence farmer perceptions on OPV benefits. The study findings showed that there is a significant relationship between awareness knowledge of improved OPV maize and planting of improved OPV maize. Furthermore, the results showed that farmers perceptions of the advantages and disadvantages of improved OPV maize seed were not different among scheme and non-scheme members as they were all in agreement that improved OPV maize have more benefits than their own previously recycled seeds. Finally, findings showed that respondents municipality and scheme membership had a significant, effect on the positive perception of planting improved OPV maize seeds. Other explanatory variables such as sex, farming experience, years of viii schooling, farm size, income and age of participants had no significant effect on farmer perceptions. It is therefore recommended that improved OPV maize be made widely available and promoted based on its advantages to enhance its adoption. Future studies on these seed schemes could look into the production and financial analysis of CBSPSs to ascertain their profitability and sustainability. / Agricultural Research Council (ARC)
30

Allelism and allele sequence divergence of LOP, the locus of parthenogenesis in the model apomict Hieracium praealtum (Asteraceae)

McGee, Rob January 2013 (has links)
Apomixis, or asexual seed development, if introduced into crop species, has the potential to greatly improve global food production. Towards this goal, this study focused on uncovering the genetic mechanisms that control the parthenogenesis step within apomixis whereby fertilisation is avoided. In the model apomict, Hieracium praealtum (Asteraceae), parthenogenesis is controlled by the LOSS OF PARTHENOGENESIS (LOP) locus. Previous research showed that in addition to genomic copies of candidate genes at LOP, the genome has at least three other copies referred to as alternative alleles. The main goal of this study was to investigate four candidate genes, Genes B, X, H and Y, at LOP by generating segregation data of the alternative alleles. BAC clones containing alternative allele sequences were identified and Roche 454 pyrosequenced. These sequences were used to design alternative allele specific primers for genotyping two Hieracium praealtum polyhaploid populations (~ 300 plants). Four major conclusions were drawn from this study. First, the alternative alleles were in fact acting like alleles to the LOP alleles of Genes B, X and Y. Second, allelic sequence divergence (ASD) of the LOP alleles of Genes B and X relative to the alternative alleles, indicated a recent and separate evolutionary history. Third and, unexpectedly, recombination was detected at the LOP locus, in contrast to other apomixis loci reported in the literature. Furthermore, Gene B was found to be very closely associated with parthenogenesis in the polyhaploid population indicating that it may be essential to parthenogenesis and therefore requires further investigation. On the other hand, the absence of Genes X, Y and H, due to recombination, had no impact upon parthenogenesis. Fourth, the sequence data suggested that the LOP and alternative alleles originated from a shared common allele ancestor. It is hoped that these findings have made a significant contribution towards the future goal of introducing apomixis into crop species.

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