No description available.

Thesis (PhD(Agric) (Agronomy))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The use of capacitance water sensors for the scheduling of irrigation for hydroponic tomato and cucumber crops grown in coir was investigated in a series of laboratory and glasshouse experiments in the Free State province of South Africa. Laboratory experiments in a climate controlled chamber were conducted to accurately calibrate ECH2O capacitance sensors, models EC-10 and EC-20, in coir with an improved calibration procedure. Water content predictions by the coir-specific calibration and manufacturer’s calibration equations were compared to actual water content measured from mass loss of the coir sample. The manufacturer’s calibration equation indicated a poor accuracy of prediction, which mostly underestimated the volumetric water content, compared to the near perfect prediction of the coir-specific calibration of individual sensors. A rapid calibration procedure for EC-10 and EC-20 sensors was proposed to reduce the calibration time of the sensors and promote their commercial use for irrigation management in coir. The accuracy of prediction by the rapid calibration procedure for the plant available water content range was high for both EC-10 and EC-20 sensors and allowed for the compensation for variation between sensors. Glasshouse studies aimed to characterise the water retention and ability of coir to supply water to greenhouse tomato and cucumber crops through the continuous monitoring of medium water content in small and large growing bags with the EC-10 and EC-20 capacitance sensors during a drying cycle, compared to well-watered plants. Stages of crop water stress were identified and, based only on the plant’s response to the drying cycle, it was suggested that water depletion can be allowed to the point of mild water stress for both greenhouse tomato and cucumber crops, which can be detected by soil water sensors. In a second series of glasshouse experiments, the identified stages of crop water stress were used to determine and apply depletion levels in coir and compare this irrigation strategy to a well-watered treatment for greenhouse cucumber and tomato plants, with regard to the water balance components, yield and water use efficiency for different bag sizes. Results indicated that irrigation was successfully managed to the pre-determined water depletion levels for cucumber and tomato plants in coir, through the use of in situ calibrated capacitance sensors. For both crops the depletion of water varied between bag sizes, indicating that various bag sizes require different irrigation management strategies. Scheduling to the highest pre-determined by 124 L m-2 in the small and 240 L m-2 in the large bags for cucumbers and 427 L m-2 in the small and 487 L m-2 in the large bags for tomato plants, compared to the well-watered treatments. Yields achieved by the greenhouse tomato plants in the large growing bags and cucumber plants in the small and large bags were maintained or improved when scheduled to the highest depletion level (approximately 60% available water content) compared to the well-watered treatment. The combination of reduced irrigation and improved or maintained yields resulted in improved water use efficiencies (based on irrigation and transpiration) for the highest depletion level compared to the well-watered treatments. In all glasshouse experiments the well-watered treatment resulted in luxury water use by the plants. Finally, a study was conducted in order to compare crop water stress of greenhouse cucumber and tomato plants under luxury water supply and cyclic water deficit conditions. The comparison was based on the transpiration ratio and yield, while the use of capacitance sensors was evaluated for irrigation scheduling in coir for both crops. Transpiration data indicated that cucumber and tomato plants subjected to luxury water supply experience water stress earlier than plants subjected to cyclic water deficit conditions, irrespective of bag size. Results also indicated that irrigation scheduling according to water depletion levels in small bags is not yet recommended for greenhouse tomato and cucumber plants grown in coir, until further research is conducted. Scheduling to water depletion levels in large bags is, however, justified by the improved or maintained yields of the greenhouse cucumber and tomato plants. The estimated depletion levels for large bags beyond which yield are reduced was at 85% for tomatoes and 70% for cucumbers. In conclusion, the results clearly indicated that the use of capacitance sensors in large growing bags improves irrigation management of hydroponic cucumbers and tomatoes in coir by eliminating over-irrigation and improving water use efficiency. More research is needed before a conclusion can be made regarding irrigation scheduling with capacitance sensors in small growing bags. / AFRIKAANSE OPSOMMING: Die gebruik van kapasitansie water sensors vir besproeiingskedulering van tamatie en komkommer plante wat hidroponies in kokosveen gegroei is, is ondersoek in ‘n reeks laboratorium en glashuis eksperimente in die Vrystaat provinsie van Suid Afrika. Laboratorium eksperimente is uitgevoer in ‘n klimaat beheerde kas om ECH2O kapasitansie sensors, modelle EC-10 en EC-20, akkuraat te kalibreer vir kokosveen deur ’n verbeterde kalibrasie prosedure. Waterinhoud voorspellings deur die kokosveen spesifieke kalibrasie en die vervaardiger se kalibrasie vergelykings is vergelyk met die werklike waterinhoud wat gemeet is deur die kokosveen monster se massaverlies te monitor. Akkuraatheid van voorspelling deur die vervaardiger se kalibrasie vergelykings was swak en het meestal die volumetriese waterinhoud onderskat in vergelyking met die byna perfekte voorspelling deur die kokosveen spesifieke kalibrasie van individuele sensors. ’n Vinnige kalibrasie prosedure vir die EC-10 en EC-20 sensors is voorgestel om die kalibrasie tyd te verkort en die kommersiële gebruik van die sensors vir besproeiingsbestuur in kokosveen aan te moedig. Die akkuraatheid van voorspelling deur die vinnige kalibrasie prosedure, binne die grense van plant beskikbare waterinhoud, was hoog vir beide EC-10 en EC-20 sensors, terwyl die prosedure ook voorsiening maak vir variasie tussen sensors. Glashuis studies is uitgevoer om die water retensie en vermoë van kokosveen om water te voorsien aan tamatie en komkommer gewasse in kweekhuise, te karakteriseer. Dit is bereik deur die mediumwaterinhoud van klein en groot plantsakke deurlopend te monitor met behulp van die EC-10 en EC-20 kapasitansie sensors gedurende ’n uitdroging siklus, en dit te vergelyk met ’n waterryke behandeling vir elke gewas waarvolgens die plante agt keer per dag besproei is. Fases van gewas waterstremming is geïdentifiseer en, volgens die reaksie van die plant tot die drogingsiklus, is dit voorgestel dat wateronttrekking toegelaat kan word tot die punt van matige waterstremming wat aangewys kan word deur kapasitansie water sensors vir beide kweekhuis tamatie en komkommer gewasse. In ’n tweede reeks glashuis eksperimente is die geïdentifiseerde fases van gewas waterstremming gebruik om onttrekkingsvlakke vir kokosveen te bepaal en toe te pas as besproeiingskeduleringstrategie vir kweekhuis komkommer en tamatie plante. Toegepaste vlakke is vir elke gewas vergelyk met ’n waterryke behandeling ten opsigte van die waterbalans komponente, opbrengs en watergebruiksdoeltreffendheid in verskillede sakgroottes. Resultate het aangedui dat besproeiing suksesvol bestuur is tot die voorafbepaalde wateronttrekkingsvlakke vir komkommer entamatie plante in kokosveen, deur gebruik te maak van in situ gekalibreerde kapasitansie sensors. Die onttrekking van water deur beide gewasse het verskil tussen klein en groot sakke, wat aangedui het dat verskillende sakgroottes verskillende besproeiingsbestuur strategieë vereis. Skedulering tot die hoogste voorafbepaalde onttrekkingsvlak het, in vergelyking met die waterryke behandelings, besproeiing verminder met 124 L m-2 in die klein en 240 L m-2 in die groot sakke vir komkommers, en 427 L m-2 in die klein en 487 L m-2 in die groot sakke vir tamatie plante. Opbrengste van kweekhuis tamatie plante in die groot plantsakke en komkommer plante in die klein en groot sakke is gehandhaaf of verbeter deur skedulering tot die hoogste onttrekkingsvlak (ongeveer 60% van beskikbare water inhoud), in vergelyking met die waterryke behandeling. Die kombinasie van verminderde besproeiing en verbeterde of gehandhaafde opbrengste het gelei tot verbeterde watergebruiksdoeltreffendheid (besproeiing en transpirasie) vir die hoogste onttrekkingsvlak, in vergelyking met die waterryke behandelings. In al die glashuis eksperimente het die waterryke behandeling gelei tot oorvloedige watergebruik deur plante. ’n Finale studie is uitgevoer om gewas waterstremming van kweekhuis komkommer en tamatie plante wat onderwerp is aan oorvloedige watervoorsiening deur agt keer per dag te besproei en sikliese watertekorttoestande, te vergelyk. Die vergelyking is gebaseer op die transpirasie verhouding en opbrengs, terwyl die gebruik van kapasitansie sensors vir besproeiingskedulering in kokosveen vir beide gewasse geëvalueer is. Transpirasie data het aangedui dat komkommer en tamatie plante wat onderwerp is aan oorvloedige watervoorsiening vroeër waterstremming ervaar as plante wat onderwerp is aan sikliese watertekorttoestande, ongeag van die sakgrootte. Resultate het aangedui dat besproeiingskedulering volgens wateronttrekkingsvlakke vir klein sakke nog nie aanbeveel kan word vir kweekhuis tamatie en komkommer plante alvorens verdere navorsing gedoen is nie. Skedulering tot wateronttrekkingsvlakke vir groot sakke word egter geregverdig deur die verbeterde of gehandhaafde opbrengste van kweekhuis komkommers en tamaties. Die beraamde laagste onttrekkingsvlakke vir groot sakke wat nie opbrengs betekenisvol sal beïnvloed nie is 85% vir tamaties en 70% vir komkommers. Ten slotte dui die resultate duidelik daarop dat die gebruik van kapasitansie sensors in groot plantsakke besproeiingsbestuur van hidroponiese komkommers en tamaties in kokosveen verbeter deur oorbesproeiing uit te skakel en die watergebruiksdoeltreffendheid te verbeter. Meer navorsing is nodig alvorens ’n gevolgtrekking gemaak kan word ten opsigte van besproeiingskedulering met kapasitansie sensors in klein plantsakke.

Call number: LD2668 .T4 1979 L65 / Master of Science

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Horticulture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology, 2012 / The effects of various water quantities were assessed on Cucumber (Cucumis sativa L.) grown hydroponically in the greenhouse. The objectives of the study were to evaluate influence of water quantities on: i) photosynthesis and chlorophyll content of Cucumis sativa L.; ii) the nutrient uptake in Cucumis sativa L. iii) flavonoid and anthocyanin metabolism in Cucumis sativa L. and iv) growth and yield in Cucumis sativa L. The treatments included 8 various water regimes (2l/h, 4l/h, 6l/h, 8l/h, 10l/h, 12l/h, 14l/h and 16l/h. The plants received water five times a day, making it 10, 20, 30, 40, 50, 60, 70, and 80 litres per day. Results showed that generally the Photosynthetic rate (A), intercellular CO2 concentration (Ci) and stomata conductance (gs) and the transpiration rate of the cucumber plants were significantly increased by increasing water quantities compared with lower water quantities. Additionally, there were significant improvements in leaf colour in weeks 2, 3, 4, 5, 6, 7 and 8. Overall, the foliage colour was improved as water supply was increased. The greener leaves were documented in treatments supplied with higher water doses. Additionally, the chlorophyll content of cucumber plants was increased significantly with varying water quantities. The highest chlorophyll contents were found in plants treated with 16l/h. The fresh and dry weights of roots, leaves and stems were significantly (P≤0.001) influenced by different water quantities supplied to Cucumis sativa L. The largest quantity of fresh roots was recorded in the control treatment (2l/h) in comparison with all other treatments. However, the best growth with regard to fresh and dry weights of leaves and stems were recorded by supplying the water quantities ranging from 10-16l/h. Altering water supply significantly (P≤0.001) affected the uptake of nitrogen, phosphorous, potassium, calcium, sodium, copper, zinc, aluminium and iron in roots of Cucumis sativa L. Irregular results were recorded in the uptake of these nutrients in the roots. However, leaf uptake of N, P, K, Ca, magnesium, sulphur, Cu, Zn, manganese, boron, and Al responded significantly (P≤0.001) to the different water quantities. The best result for each was observed at quantities involving 16l/h. In stems of cucumber water quantities significantly (P≤0.001) affected the uptake of N, P, K, Ca, Mg, Na, S, Cu, Zn, Mn and B. The highest uptake of N, P, Ca, Mg and S were found at the maximum supply of water (16l/h) compared with the control (2l/h). Sodium uptake showed irregular patterns, whereas K and Zinc uptake peaked at 14l/h. The data from this study showed that flavonoid metabolism was not significantly affected by the different water quantities supplied to cucumber plants. However, the anthocyanin content in roots, leaves, and stem was significantly influenced by water levels. The lowest water quantity (2-6l/h) significantly increased the levels of anthocyanins in all tissues tested. Increasing water quantities significantly decreased the anthocynanin metabolism in all tissues. Plant height displayed significant differences with water quantities from weeks 1-8. In week 1, the plant height was superior at supplying 4l/h in comparison with other treatments. In week 2 and 5 irregular trends were detected. At weeks 3 and 4, plants supplied with 8-12l/h displayed superior plant height performance. At weeks 7-8, significant and optimal results were observed at water quantities ranging from 4-16l/h compared with the control treatment. Water quantities significantly (P≤0.001) affected the number of leaves per plant from weeks 2-8. Irregular results were displayed in weeks 2 and 3. At weeks 4 and 5, the highest numbers of leaves were in water quantities of 12l/h and 10l/h, respectively. Generally, leaf numbers increased with increasing water levels from weeks 6-8. Plant vigour was significantly affected by the alteration of water quantities at weeks 1, 2, 4, 5, 6, 7 and 8. At weeks 1 and 4, more vigorous plants were found in the treatments that received from 10-16 l/h. At weeks 2 and 5, optimal results were found at treatments that received from 6-14l/h. At weeks 6, 7 and 8, the most vigorous plants were found at the highest water quantity of 16l/h. With fruit length, fruit width, rind colour, fruit quality (marketable fruit) and weight, results from the harvest done in the first, second and third week showed that water quantities significantly influenced these parameters. Optimal results were reported when the plants were supplied with water ranging between 14-16l/h. During harvesting at week 4, the fruit length, width, rind colour, were of marketable quality at 16l/h. Generally, the plants that received highest amount of water (16l/h) had the highest cucumber yields compared with all other treatments. Higher water quantities in this study resulted in increased physiological responses such as photosynthesis and nutrient uptake which resulted in the higher fruit yields. In water-limited environments, results from this study could assist growers with reasonable cucumber yields while saving water for other farm uses.

Orientador: Antonio Ismael Inácio Cardoso / Banca: Noberto da Silva / Banca: Keigo Minami / Resumo: Foram conduzidos dois experimentos na FCA/UNESP, objetivando avaliar a depressão causada por endogamia com sucessivas gerações de autofecundação em uma população de pepino do tipo japonês. No primeiro experimento foram avaliadas características de produção de frutos imaturos no período de 21/08/2002 à 29/11/2002 em ambiente protegido. No segundo experimento foram avaliadas características de produção e qualidade de sementes no período de 12/03/2003 à 13/06/2003 em condições de campo. A partir do intercruzamento entre plantas do híbrido Natsu suzumi foi obtida a geração F2, considerada como população S0. Obtiveram-se progênies S1, S2, S3, S4 e S5, através de autofecundações sucessivas pelo método do SSD ('Single Seed Descent'). Ao partir da mistura ao acaso de sementes de progênies com igual número de autofecundações sucessivas foram obtidas cinco populações denominadas de população S1 a população S5. Foram sete tratamentos (híbrido Natsu suzumi, populações S0 a S5) e o delineamento experimental foi em blocos ao acaso, com seis e quatro repetições no primeiro e segundo experimento, respectivamente e cinco plantas por parcela nos dois experimentos. No primeiro experimento (frutos imaturos) foram avaliados, número de folhas, comprimento da haste principal, número e massa de frutos, total e comercial, número de nós e porcentagem de brotações. No segundo experimento (frutos maduros) avaliaram-se características relacionadas com produção (número e massa de sementes por planta e por fruto) e qualidade de sementes (teste padrão de germinação, primeira contagem de sementes, índice de velocidade de germinação, massa de 100 sementes). Foram realizadas as análises de variância para cada característica, e as médias dos tratamentos foram comparadas pelo teste de Tukey (%). Também foram realizados análises de variância apenas com as seis... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Two experiments were set up at FCA/UNESP. The objective of this work was to evaluate the inbreeding depression with successive generations of self pollination in a cucumber Japanese population. It was studied one population F2 obtained from a commercial hybrid (Natsu suzumi) considered as S0 population. In the first experiment were appraised characteristics of production of immature fruits in the period of 21/08/2002 to 29/11/2002 in protected cultivation. In the second experiment were appraised seed production and quality in the period of 12/03/2003 to 13/06/2003 in open field conditions. It was obtained progenies S1, S2, S3, S4 and S5 through the 'Single Seed Descent' methodology. It was used randomized blocks with seven treatments (different generations of self pollination - S0 to S5 and the hybrid Natsu suzumi) six and four replicates in the first and second experiment and five plants per plot in both. In the first experiment (immature fruits) were evaluated number of leaves, length of the main stem, number and weight of fruits, total and commercial, number of nodes and vines percentage. In the second experiment (mature fruit) characteristic related with production were evaluated (number and weight of seeds per plant and per fruit) and quality of seeds (germination test, first counted of seeds, index of germination speed and weight of 100 seeds). The variance analyses were accomplished each characteristic and the averages of the treatments were compared by the test of Tukey (%). Also accomplished just with the six inbreed generations to evaluate the possible inbreeding depression (without including the commercial hybrid). In the comparison among the population differences were not observed for the characteristics appraised showing there were not production loss for inbreeding in this population. However, for the characteristics length of the main stem, number of total fruit, weight of seeds per fruit and seed number per fruit the commercial. / Mestre

No description available.

Thirty-two isolates of rhizosphere bacteria, selected for their ability to inhibit zoospore germination and/or mycelial growth of Pythium aphanidermatum (Pa) in vitro, were evaluated in a test tube bioassay using cucumber c.v. 'Straight 8'. These isolates were identified as Psedudomonas corrugata (Pc13 or 35) and P. fluorescens (Pf15, 16 or 27). All but one of the five isolates effectively colonised the roots of cucumber plants in short term studies. Isolates 15 and 35 were found to maintain high population densities throughout the time period. Pa-inoculated plants treated with the Pc13 or Pf15 produced fruit yields equal to 92 and 74% respectively of the control (no Pa, no bacteria). Pa-inoculated plants without bacteria yielded only 46% of the control. In the fall crop, Pa-inoculated plants treated with Pc13 or Pf15 yielded 52 and 47% of the control compared to Pa-only treatment, which yielded 12.5% of the control. In both crops, treatment with any of the bacterial isolates resulted in significantly reduced cull rates compared to the Pa-only treatment.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.

Made available in DSpace on 2015-04-17T14:55:25Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7694336 bytes, checksum: 9e31ccfd75ef937c6222af7f15aff9a9 (MD5) Previous issue date: 2013-04-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The class Holothuroidea has approximately 1400 species existent, these nearly 50 are recorded to de Brazilian coast. Studies about this class are relatively few, particularly to the North and Northeast of Brasil. In front of the lack of information on the species of holothurians to the Brazilian coast the present study aimed to identify the species of the class Holothuroidea from the Northeast of Brasil to inventory and provide detailed taxonomic information as well as data on their distribution in the region. The Invertebrate Collection Paulo Young, of the Department of Systematics and Ecology (DSE), of Federal University of Paraíba (CIPY-DSE-UFPB) was the main the main material analyzed. Were also examined the collections of the museums of the Federal University of Bahia (MZUFBA), Museu Nacional do Rio de Janeiro (MNRJ) and University of São Paulo (MZUSP). The study of specimens includes analysis of external and internal morphological characters, beyond the pattern of calcareous ossicles, these latter are fundamental for determining the specific level. 32 species were identified, belonging to 3 orders, 8 families, 19 genera and 8 subgenera. Of the species recorded Thyone crassidisca Miller & Pawson, 1981, Euthyonidiella trita (Sluiter, 1910), Protankyra ramiurna Heding, 1928 and Holothuria (Holothuria) dakarenisis represent new records to Brazilian coast. The states with the highest diversity regarding Holothuroidea fauna was, respectively, Paraíba (n = 22 spp.), Bahia (n = 21 spp.), Alagoas (n = 14 spp.) and Pernambuco (n = 10). No species were recorded for states of Maranhão e Sergipe. The fauna of infralittoral requires better sampling. Moreover, in some species taxonomic problems were observed and discussed. The study provides the first annotated list of sea cucumbers from Northeastern Brazil. Reinforces the importance of scientific collections for systematic studies and increased knowledge of biodiversity. / A classe Holothuroidea possui aproximadamente 1400 espécies viventes, das quais 50 foram registradas para a costa brasileira. Estudos sobre a classe no Brasil são relativamente escassos, principalmente para as regiões Norte e Nordeste. Diante da carência de informações sobre as espécies de holotúrias do litoral brasileiro o presente estudo objetivou identificar as espécies da classe Holothuroidea proveniente da região Nordeste do Brasil, a fim de inventariar e fornecer informações taxonômicas detalhadas bem como dados sobre sua distribuição na região. O principal acervo analisado foi o da Coleção de Invertebrados Paulo Young, do Departamento de Sistemática e Ecologia (DSE), da Universidade Federal da Paraíba (CIPY-DSE-UFPB). Além deste, Foi examinado material do Museu de Zoologia da Universidade Federal da Bahia (MZUFBA), Museu Nacional (MNRJ) e Museu de Zoologia da Universidade de São Paulo (MZUSP). O estudo dos espécimes abrange a análise de caracteres morfológicos externos e internos, bem como do padrão dos ossículos calcários, estes últimos são fundamentais para a determinação a nível específico. Foram identificadas 32 espécies pertencentes a 3 ordens, 8 famílias, 19 gêneros e 8 subgêneros. Das espécies registradas Thyone crassidisca Miller & Pawson, 1981, Euthyonidiella trita (Sluiter, 1910), Protankyra ramiurna Heding, 1928 e Holothuria (Holothuria) dakarenisis representam novos registros para a costa brasileira. Os estados que apresentaram maior diversidade em relação à fauna de Holothuroidea foram respectivamente, Paraíba (n = 22 spp.), Bahia (n = 21 spp.), Alagoas (n = 14 spp.) e Pernambuco (n = 10). Com base nos acervos analisados, Maranhão e Sergipe foram os únicos estados em que nenhuma espécie da classe foi registrada. Nota-se que a fauna do infralitoral necessita de uma melhor amostragem. O estudo fornece a primeira lista comentada dos Holothuroidea do Nordeste. Fortalece ainda a importância das coleções científicas para estudos em sistemática e ampliação do conhecimento da biodiversidade.

CAPES / A indução de resistência é conceituada como a ativação de um estado de resistência contra doenças, o qual é induzido sistemicamente em plantas pela utilização de agentes bióticos ou abióticos, sem qualquer alteração do genoma da planta, ocorrendo de maneira não específica, por meio da ativação de genes que codificam para diversas respostas de defesa vegetal. A quitosana é um polímero derivado da desacetilação da quitina, encontrada em grande quantidade na carapaça de crustáceos, sendo estudada com potencial para controle fitopatógenos, tanto para sua ação fungistática direta, quanto pela capacidade de induzir a defesa das plantas, indicando a presença de moléculas com características elicitoras. Foram desenvolvidos três experimentos com objetivos de avaliar o potencial da quitosana na indução de resistência a plântulas de beterraba (Beta vulgaris), tomate (Solanum lycopersicum) e pepino (Cucumis sativus) e no controle de Fusarium sp., Rhizoctonia solani Kuhn e Pythium sp. em condições in vitro. O delineamento experimental foi inteiramente casualisado, com quatro repetições As sementes de beterraba, tomate e pepino foram submersas em solução de quitosana por 20 minutos, nas concentrações de 0,25; 0,5; 1 e 2% e na testemunha água destilada. As sementes foram semeadas em bandejas de poliestireno expandido contendo substrato lantmax Florestalr previamente esterilizado e inoculado com Fusarium sp., Rhizoctonia solani Kuhn e Pythium sp., respectivamente, para as três culturas. O experimento foi conduzido por 14 dias em câmara de cultivo com controle de temperatura (25 C 2 C), luminosidade (fotoperíodo de 12 horas) e umidade relativa (70% 10%). As avaliações realizadas foram emergência das sementes, tombamento de plântulas, comprimento de plântulas, massa da matéria fresca e atividade das enzimas fenilalanina amônia-liase (FAL), quitinases e b-1,3- glucanase. Foi avaliado tamb´em o crescimento micelial de Fusarium sp., Pythium sp. e R. solani em meio de cultura B.D.A. (Batata-Dextrose e Agar) contendo quitosana nas mesmas concentrações avaliadas nas sementes. Na cultura da beterraba, o tratamento de sementes com quitosana propiciou maior emergência e comprimento das plântulas, e reduziu o percentual de tombamento. O tratamento com quitosana ativou a resistência sistêmica adquirida com expressão das enzimas quitinases e b-1,3-glucanase. No tomate a quitosana na concentração de 0,25% favoreceu a emergência das plântulas, reduziu a incidência de tombamento e ativou as enzimas FAL, quitinases e b-1,3-glucanase. Em pepino, com concentração de até 0,5%, favoreceu a emergência das plântulas e reduziu a incidência de tombamento. A quitosana ativou as enzimas FAL e b-1,3-glucanase. A quitosana também apresentou ação fungistática sobre o crescimento inicial de Pythium sp. e Rhizoctonia solani Kuhn em condições in vitro, no entanto, tal ação não prevaleceu até o término do experimento. Para Fusarium sp. o aumento da concentração da quitosana resultou na redução do crescimento micelial in vitro. / Induction of resistance is defined as the activation of a state of resistance against diseases which is induced systemically in plants by the use of biotic or abiotic agents without any modification of the plant genome, occurring non-specific way, by activating genes coding for various plant defense responses. Chitosan is a polymer derived from the deacetylation of chitin, which is found in large quantities in crustacean shell, and studied with the potential to control plant pathogens, both by its direct fungistatic action, as the ability to induce protection of plants, indicating the presence of molecules of elicitoras characteristics. Three experiments with objective of evaluating the potential of chitosan in the seedling resistance induction were developed, beet (Beta vulgaris) seeds, cucumber (Cucumis sativus) seeds and tomato (Solanum lycopersicum) seeds, and the control of Fusarium sp., Rhizoctonia solani K¨uhn e Pythium sp. in vitro conditions. The experimental design was completely randomized, with four replications. Beet seeds, tomato and cucumber were submerged in chitosan solution for 20 minutes, in concentrations of 0.25, 0.5, 1 and 2% in the control and distilled water. Seeds were sown in trays containing Plantmax Florestalr substrate sterilized and inoculated with Fusarium sp., Rhizoctonia solani K¨unh and Pythium sp., respectively for the three cultures. The experiment was conducted for 14 days in growth chamber with controlled temperature (25 C 2 C), light (12 hour photoperiod) and humidity (70% 10%). The evaluations were seed emergency, seedling damping-off, seedling length, fresh weight and activity of the enzymes phenylalanine amˆonia-liase (PAL), chitinase and b-1,3-glucanase. It was also rated the mycelial growth of Fusarium sp., Pythium sp. and R. solani on P.D.A. (Potato-Dextrose and Agar) culture medium containing chitosan at the same concentrations evaluated in seeds. For beet growing, seed treatment with chitosan presented higher emergence and the length of the seedlings, and reduced the percentage of tipping. Treatment with chitosan activated the systemic acquired resistance with expression of chitinase and b-1,3-glucanase enzymes. For the tomato crop in chitosan concentration of 0.25% favored the emergency of seedlings, reduced the incidence of tipping and activated the PAL enzymes, chitinase and b-1,3-glucanase. In cucumber on the concentration of up 0.5% favored seedlings emergence and reduces the incidence of tipping. Chitosan activated the PAL enzymes and b-1,3-glucanase. Chitosan also presented fungistatic action on the initial growth of Pythium sp. and R. solani in vitro conditions, however, such action did not prevail until the end of the experiment. To Fusarium sp. the concentration of chitosan resulted in the reduction of mycelial growth in vitro.