Glucosinolates are amino acid derived secondary metabolites found in the order Capparales. It is an important class of phytochemicals involved in plant-microbe, plant-insect, plant-animal and plant-human interactions. It is, therefore, important to understand genetic mechanism of glucosinolate biosynthesis in Brassica for efficient manipulation. In this study, QTL mapping of leaf and seed glucosinolates was performed in B. rapa using two RIL populations, SR-RILs and BU-RILs. QTL mapping was performed using SR-RILs developed from a cross of Chinese cabbage and turnip rapeseed and a genetic map in B.rapa. Genetic map was developed using a total 1,579 molecular markers including 9 markers specific to glucosinolate genes, GSL-ELONG, GSL-PRO, GSL-FMOOX1, and GSL-AOP/ALK. Several QTL for progoitrin, gluconapin, glucoalyssin, glucobrassicanapin, 2-methylpropyl and 4-hydoxyglucobrassicin glucosinolates were identified with phenotype variance between 6 and 54%. Interestingly, a major QTL for 5C aliphatic glucosinolates was co-localized with a candidate Br-GSL-ELONG locus on linkage group A3, displayed co-segregation with co-dominant SCAR marker BrMAM1-1. The Br-GSL-ELONG locus was identified to regulate 20 µmole/g seed 5C glucosinolate biosynthesis. BU-RILs derived from a cross of yellow sarson and USU9 was segregated for glucoerucin, gluconapin and progoitrin 4C aliphatic glucosinolates with 4-hydoxyglucobrassicin. Phenotyping was performed in controlled and field environments for seed glucosinolates and controlled environments for leaf glucosinolates. Genetic map was developed using SRAP markers and glucosinolate gene, GSL-ELONG and GSL-PRO specific 4 loci were integrated on map. Four and three QTL were identified for seed glucoerucin and gluconapin, respectively in both environments with phenotypic variance up to 49%. Additionally, genetic manipulation of glucosinolates was performed by backcross with MAS in B. rapa. Resynthesized B. napus line was backcrossed with B. rapa genotypes, RI16, BAR6 and USU9 for replacement or introgression of glucosinolate genes, GSL-ELONG- and GSL-PRO+. In RI16 genotype, 15 to 25 µmole/g seed 5C glucosinolates reduced in 15 BC3F2 lines those were positive with GSL-ELONG- marker and negative with the A-genome and gene specific marker BrMAM1-1. This suggests that the functional allele has replaced by non-functional from B. oleracea. GSL-PRO+ positive backcross lines in RI16 genotype displayed sinigrin 3C aliphatic glucosinolate in B. rapa. This suggests introgression of GSL-PRO+ in B. rapa.

A genetic linkage map of mustard (Brassica juncea) was developed using two double haploid populations produced from crosses between a low erucic cultivar “ZEM1” and two moderate erucic acid lines “Vniimk351” and “Vniimk405” with the use of SSR and SRAP markers. The linkage map of the ZEM1xVniimk351 population included 13 linkage groups with an overall length of 791 cM with an average marker interval of 5.7 cM. The linkage map of the ZEM1xVniimk405 population also contained 13 linkage groups with a distance of 623 cM and an average marker interval of 4.6 cM. Using the linkage maps for the two populations, QTLs were detected for seed oil, protein and fatty acids. QTL analysis for fatty acids indentified QTLs on LG1, 7 and 12 for the ZEM1xVniimk351 population and LG1, 3 and 4 for the ZEM1xVniimk405 population. Analysis for the seed oil and protein content in the ZEM1xVniimk351 population identified 2 QTLs on LG1 and LG4 and 1 QTL on LG1 respectively. The QTL analysis ZEM1xVniimk405 of oil and protein content identified 1 QTL for oil and protein on LG1. The variation of fatty acids was shown to be the result of monogenic inheritance of the FAE1 gene in both populations.

Zusammenfassung Brassica-Arten sind von großer Bedeutung für die menschliche Ernährung und für die Tierernährung. Brassica napus ist hinter der Sojabohne die zweit wichtigste Ölsaat. Brassica oleracea umfasst mehrere wichtige Gemüseformen. Die Produktivität dieser Arten wird weltweit durch Versalzung als ein biotischer Stressfaktor beeinträchtigt. Die Salztoleranz ist abhängig von der Pflanzenentwicklung, also stadienspezifisch, artspezifisch und organspezifisch. Im Vergleich zu unseren Kenntnissen über Samenglucosinolate ist wenig über die genetische Kontrolle von Blattglucosinolaten bekannt. Die Arbeit hat folgende Zielsetzungen: (1) den Einfluss von Salzstress auf zwei Entwicklungsstadien zu untersuchen, und zwar auf die Keimung und die Jungpflanzenentwicklung, und in doppel-haploiden (DH) Populationen von B. napus und B. oleracea QTL (Quantitative Trait Loci) für Salztoleranz in beiden Entwicklungsstadien zu kartieren, und (2) die Variation im Blatt-GSL Gehalt zu untersuchen und QTL zu kartieren für den GSL Gehalt in einer Kontrolle und unter Salzstress. Der Einfluss von Salzstress auf die Keimfähigkeit wurde an drei DH Populationen untersucht, zwei B. napus und eine B. oleracea Population. Die beiden erstgenannten Populationen wurde aus Alesi × H30 bzw. Mansholts × Samourai entwickelt. Die B. oleracea Population entstand aus der Kreuzung zwischen der „rapid cycling“ Linie TO1000DH3 (TO) und einer DH Linie aus dem Broccoli Early Big (EB). Die Anzahl DH Linien 138 Für die QTL Analysen wurde eine framework map verwendet mit 188, 208 bzw. 128 Markern für die Populationen Alesi × H30, Mansholts × Samourai bzw. TO × EB. Die Versuche wurden mit den Salzkonzentrationen 200 mM NaCl für B. napus und 100 mM NaCl für B. oleracea durchgeführt. Von jeder DH Linie wurden 10 Samen in 9 cm Petrischalen auf Filterpapier ausgelegt, das mit 5 ml Leitungswasser als Kontrolle bzw. 5 ml Salzlösung befeuchtet war. Die Petrischalen wurden bei 20 °C im Dunkeln inkubiert. Die Anzahl gekeimter Samen wurde täglich gezählt. Unter Salzstress war die Keimfähigkeit signifikant reduziert und die Keimgeschwindigkeit verlangsamt. Einige DH Linien übertrafen dabei ihre Eltern mit einer höheren Keimfähigkeit und Keimgeschwindigkeit. Es konnten für alle untersuchten Merkmale mehrere QTL identifiziert werden. Einige dieser QTL beeinflussen die Merkmalsausprägung sowohl in der Kontrolle als auch unter Salzstress, während andere QTL nur entweder in der Kontrolle oder in der Stressvariante auftreten. Der Einfluss von Salz auf die Jungpflanzenentwicklung wurde in der B. napus DH Population Mansholts × Samourai und in der B. oleracea Population TO × EB untersucht. Von jeder Population wurden die DH Linien und die Eltern in Topfversuchen im Gewächshaus bei halbkotrollierten Bedingungen angezogen. Die Salzkonzentrationen waren 200 mM NaCl für B. napus und 100 mM NaCl für B. oleracea. Die erfassten Merkmale waren Frischgewicht (FW), Trockengewicht (DW), Chlorophyllgehalt (SPAD), relativer Wassergehalt (RWC), Natriumgehalt (Na+ mg/g DM), Kaliumgehalt (K+ mg/g DM) sowie das Natrium/Kalium-Verhältns (Na+/K+). Der Salzstress begann 21 Tage nach Aussaat und der Versuch wurde 35 Tage nach Aussaat beendet. In beiden Populationen trat für alle Merkmale eine signifikante Variation auf. In beiden Populationen war das Wachstum unter Salzstress gehemmt, wobei FW und DW sehr stark reduziert waren während der RWC nur eine leichte Reduktion zeigte. Die anderen Merkmale zeigten unter Salzstress einen Anstieg mit Ausnahme von K+ in der B. oleracea Population. Die SPAD Werte zeigten einen Anstieg. Auch Na+ mg/g DM und Na+/K+ zeigten einen starken Anstieg. Der K+ Gehalt stieg in der B. napus Population unerwartet an, während er in der B. oleracea Population abnahm. Das Aufrechterhalten von hohen K+ Konzentrationen unter Salzstress ist ein Merkmal für Salztoleranz. Diese Ergebnisse unterstützen frühere Ergebnisse dass B. napus eine höhere Salztoleranz hat als B. oleracea. In beiden Populationen wurde sowohl in der Kontrolle als auch unter Salzstress eine Reihe von QTL identifiziert. In der B. napus Population wurden auf verschiedenen Kopplungsgruppen (LG) QTL „hotspots“ entdeckt. Der größte „hotspot“ lag auf LG C3. Auch in der B. oleracea Population wurde auf LG C3 ein „hotspot“ entdeckt mit QTL für mehrere Merkmale. Hier liegen also in derselben Region des Genoms Gene für mehr als nur ein Merkmal sowohl in der Kontrolle als auch unter Salzstress. Die Variation dieser Merkmale wird entweder von einem Gen mit pleiotropem Effekt gesteuert oder von mehreren unabhängigen Genen. Regionen mit QTL für mehrere Merkmale sind von großem Interesse weil dadurch mehr als nur ein Merkmal gleichzeitig verbessert werden kann. Unter den gleichen Bedingungen wurde in den beiden B. napus bzw. B. oleracea Populationen auch die Variation in den Blatt-GSL untersucht. Die Elternlinien beider Populationen unterschieden sich stark in GLS Gehalt und Zusammensetzung. In der B. napus Population hatte Mansholts einen im Vergleich zu Samourai hohen GSL Gehalt sowohl in der Kontrolle als auch unter Salzstress. Unter Salzstress verhielten sich die beiden Eltern unterschiedlich, Mansholts zeigte einen Anstieg und Samourai eine Abnahme des GSL Gesamtgehalts. In der B. oleracea Population zeigte die Elternlinie TO eine höheren GSL-Gehalt als der Elter EB. Die einzelnen GSL Komponenten zeigten in beiden DH Populationen eine Abnahme bei Salzstress mit Ausnahme von RAA und GBC bei B. napus und GBC bei B. oleracea. Aufgrund ihrer antioxidativen Eigenschaften könnte der Anstieg von RAA und GBC dazu dienen die ROS zu detoxifizieren, die als Reaktion auf Salzstress produziert wurden. Mehrere QTL wurden sowohl in der Kontrolle als auch unter Salzstress kartiert. In der B. napus Population wurden QTL „hotspots“ in Regionen identifiziert in denen bereits früher QTL für Samen-GSL lokalisiert wurden. Dies war vor allem auf LG A9 und LG C2 der Fall. In der B. oleracea Population wurden QTL „hotspots“ auf LG C9 und LG C7 lokalisiert. Das gleichzeitige Auftreten von QTL an derselben Position lässt sich teilweise dadurch erklären dass es sich um Komponenten derselben GSL Gruppen handelt. Es gab keine Übereinstimmung zwischen den QTL für die Keimfähigkeit unter Salzstress und den QTL für Variation bei Jungpflanzen. Dies weist darauf hin dass für die Salztoleranz während der Pflanzenentwicklung unterschiedliche Mechanismen verantwortlich sind. Durch die Kombination von QTL für Salztoleranz in den unterschiedlichen Entwicklungsstadien lässt sich eine verbesserte Anpassung an Salzstress erreichen.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2001. / Härtill 7 uppsatser.

Thesis (M. Agr. Sc.) -- Lincoln University, 2008. / "'Pasja' is considered both as a species and cultivar in this document as it [is] marketed as such in New Zealand. Technically 'Pasja' is a leaf turnip"--Abstract. Also available via the World Wide Web.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 115-117). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 19 (1958) no. 4, p. 627. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [60]-63).

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-08-09T16:29:47Z No. of bitstreams: 1 texto completo.pdf: 768841 bytes, checksum: 20c78debd7b3f93ec71b8cad3b9c52d9 (MD5) / Made available in DSpace on 2017-08-09T16:29:47Z (GMT). No. of bitstreams: 1 texto completo.pdf: 768841 bytes, checksum: 20c78debd7b3f93ec71b8cad3b9c52d9 (MD5) Previous issue date: 2017-04-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O repolho apresenta elevada demanda de nutrientes, dentre eles destaca-se o potássio (K) que é um dos macronutrientes mais extraídos pela cultura. Por apresentar elevada demanda de nutrientes, é uma cultura que requer a proposição de modelos de recomendação condizentes com o potencial produtivo atual. Diante disso, objetivou-se avaliar a produtividade e índices de eficiência de K na planta e no solo, a fisiologia e o metabolismo do repolho em função de doses e fontes desse nutriente, e propor um modelo de balanço nutricional para recomendação de nutrientes para a cultura. Foram conduzidos dois experimentos a campo em duas épocas do ano (verão e inverno) em áreas com diferentes disponibilidades de K no solo. O delineamento experimental foi em blocos ao acaso com quatro repetições. Os tratamentos consistiram de cinco doses de K 2 O (0, 100, 200, 400 e 800 kg ha -1 ) com a fonte Cloreto de Potássio (KCl), e um tratamento adicional com a fonte Sulfato de Potássio (K 2 SO 4 ) na dose de 200 kg ha -1 de K 2 O. O repolho apresentou alta eficiência de uso e de recuperação de K do solo quando em condições de menor disponibilidade de K, com a possibilidade de alcançar altas produtividades com aplicação de baixas doses de K. Com o incremento das doses de K a cultura acumulou grandes quantidades do nutriente na parte aérea, porém sem incremento correspondente na produtividade. Esse acúmulo de K diminuiu o acúmulo de N-NO 3- nas duas épocas de cultivo. A exportação de K foi a maior parte do acumulado na parte aérea para as duas épocas de cultivo, o que evidencia ser o repolho uma planta esgotante do solo. O uso restritivo ou excessivo de K incrementaram as atividades de enzimas antioxidantes, principalmente no período de verão, e também aumentaram o acúmulo de sólidos solúveis totais para as duas épocas de cultivo. Foram mínimas as diferenças entre as fontes K 2 SO 4 e KCl sobre a produtividade e índices de eficiência da adubação potássica no repolho. A fonte K 2 SO 4 acarretou menor acúmulo de Na + e de N-NO 3- para os dois períodos de cultivo, o que reforça o uso dessa fonte na obtenção de um produto com maior qualidade nutritiva. Para a modelagem da recomendação de fertilizantes, o sistema considerou o subsistema requerimento, que inclui a demanda da cultura e a eficiência de recuperação do nutriente aplicado, e o subsistema fornecimento, que corresponde ao fornecimento de nutrientes pelo solo e pelos resíduos culturais. Para determinar os atributos necessários à estimativa da demanda nutricional foram obtidos valores médios a partir de dados da literatura e de três experimentos, um com nitrogênio e dos dois experimentos com K citados anteriormente. A modelagem mostrou-se uma ferramenta útil para recomendação de adubação para a cultura do repolho. / Cabbage crop presents high demand of nutrients, potassium (K) stands out and it is one of the macronutrients most extracted by the crop. Cabbage requires proposition of recommendation models that are consistent with current productive potential because the crop presents high nutrient demand. This study aimed to evaluate the productivity and efficiency indexes of K in the plant and soil, the physiology and metabolism of cabbage in response to doses and sources of K, and to propose a nutritional balance model for nutrient recommendation for the crop. Two experiments were conducted in the field at two crop seasons (summer and winter) in areas with different soil K availability. The experiment was designed as randomized blocks with four replications. The treatments consisted of five doses of K 2 O (0, 100, 200, 400 and 800 kg ha -1 ) applied as Potassium Chloride (KCl), and an additional treatment with Potassium Sulphate (K 2 SO 4 ) at 200 kg ha -1 of K 2 O. Cabbage showed high use efficiency and recovery efficiency of K from soil under low K availability. High yields may be achieved applying low K doses. The crop accumulated large K quantities in the shoot, but without increases on productivity with increasing K doses. This accumulation of K decreased nitrate accumulation in both crop seasons. Potassium export was most of the accumulated in the shoot in both crop seasons, which shows that cabbage is a high demanding crop. The restrictive or excessive use of K increased the activities of antioxidant enzymes, mainly in the summer period, and also increased the accumulation of total soluble solids for both crop seasons. The differences between K 2 SO 4 and KCl sources on productivity and efficiency indices of K fertilization in cabbage were minimal. Potassium sulphate caused less accumulation of sodium and nitrate for both crop seasons, which reinforces the use of this source in order to obtain a product with higher nutritional quality. The system considered the subsystem requirement, which includes crop demand and nutrient recovery efficiency applied, and the subsystem supply, which corresponds to nutrient supply by soil and cultural waste for modeling the fertilizers recommendation. To determine the attributes needed to estimate nutritional demand, mean values were obtained from literature and from three experiments, one with nitrogen and the two K experiments cited above. The modeling showed to be a useful tool of fertilizers recommending for cabbage crop. / Foram impressas e anexadas 9 páginas no final da dissertação que estavam faltando.

Made available in DSpace on 2015-07-22T20:49:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-03-25 / Objetivos: Avaliar, em um modelo experimental, a aplicabilidade do teste do micronúcleo em células sanguíneas e da medula óssea no diagnóstico de alterações esofágicas decorrentes da doença do refluxo gastroesofágico; e ainda investigar o efeito quimiopreventivo de Brassica oleracea e do fármaco omeprazol. Método: A dose do extrato de Brassica oleracea foi determinada pelos testes de toxicidade in vitro e in vivo, enquanto que o refluxo duodeno-gastroesofágico foi induzido em ratos Wistar machos pelo modelo cirúrgico anastomose esofagojejunal. Oito semanas após a cirurgia, os animais foram tratados com 500 mg/Kg do extrato ou com 30 mg/Kg do Omeprazol por quatro semanas. Os animais foram pesados semanalmente. Após o término dos tratamentos, o tubo esofágico dos animais foi removido para análise histológica, enquanto que amostras de sangue e da medula óssea foram obtidas para o teste do micronúcleo. Resultados: Os animais do grupo Refluxo apresentaram um peso inferior quando comparados com os animais do grupo Controle (p < 0,0001). Entretanto, o peso dos animais não diferiu significativamente entre os tratamentos. Todos os animais do grupo Refluxo não tratados desenvolveram esofagite severa e um deles desenvolveu um carcinoma epidermóide escamoso 12 semanas após a cirurgia. Os animais tratados com o Omeprazol apresentaram uma menor incidência de espongiose (p = 0,028) e um menor grau de esofagite (p = 0,018) quando comparados com os animais não tratados. Para os animais tratados com o extrato, esta melhora não foi estatisticamente significativa. A distribuição e freqüência dos micronúcleos, bem como a freqüência dos eritrócitos micronucleados não diferiram significativamente entre os grupos e tratamentos estudados. Conclusões: O modelo anastomose esofagojejunal permitiu o estudo da evolução da doença do refluxo gastroesofágico até a esofagite severa. O tratamento com Omeprazol reduziu o processo inflamatório na mucosa esofágica, enquanto que esse efeito foi apenas indicativo nos animais tratados com Brassica oleracea. Os tipos celulares avaliados pelo teste do micronúcleo não reproduziram as características esofágicas determinadas histologicamente. Considerando a importância desse teste na investigação da genotoxicidade de substâncias in vivo, a avaliação de células diretamente expostas ao refluxo exploraria as reais alterações decorrentes da doença do refluxo gastroesofágico, bem como os possíveis efeitos dos tratamentos. / Aim: To evaluate, in an experimental model, the applicability of erythrocyte micronucleus assay in diagnosis of esophageal damage caused by gastroesophageal reflux disease (GERD) and to investigate the chemopreventive effect of Brassica oleracea extract and Omeprazole pump inhibitor drug. Methods: Brassica oleracea dose of 500 mg/Kg was determined using in vitro and in vivo toxicity tests. Male Wistar rats underwent esophagojejunostomy model to produce duodeno-gastroesophageal reflux. Eight weeks after surgical procedure, animals were treated with 500 mg/Kg of Brassica oleracea extract or 30 mg/Kg of Omeprazole for four weeks. The animals were weighed once a week. After the last treatment, the esophagus of each animal was removed for histological analysis, as well as, blood and bone marrow samples were obtained for erythrocyte micronucleus test. Results: Body weights of Reflux group were significantly lower than Control group (p < 0.0001). This difference was not observed among treatments. All non-treated animals of Reflux group developed severe esophagitis and one animal developed squamous cell carcinoma type twelve weeks after surgery. Omeprazole-treated animals developed lower incidence of spongiosis (p = 0.028) and lower grade of esophagitis (p = 0.018) compared to non-treated animals. Whereas the animals treated with Brassica oleracea extract showed the same results, no significant difference was observed. Micronucleated erythrocytes and micronucleus frequencies did not differ signicantly among groups and treatments and were not associated with histological alterations. Conclusions: The esophagojejunostomy model allowed the study of GERD progression ultil severe esophagitis. The Omeprazole treatment reduced the inflammatory process in esophageal mucosa and this effect was only indicative in Brassica oleracea treatment. The cell types evaluated by micronucleus assay did not reproduce the esophageal characteristics determined histologically. Considering the importance of this test in investigation of genotoxicity of various substances in vivo, the evaluation of esophageal cells exposed directly to reflux could show the real alterations caused by GERD, as well as the possible effects of Brassica oleracea extract and Omeprazole treatments. / TEDE / BV UNIFESP: Teses e dissertações

Com o objetivo de estimar-se a densidade de Plutella xylostella (Linnaeus, 1758) numa cultura de Brassica oleracea L. var. acephala D C., cultivar "tronchuda portuguesa", foram realizadas amostras a intervalos regulares durante a estação 1980/81, na Estação Experimental Fitotécnica de Viamão, Distrito de Águas Claras, Município de Viamão, R.S. A área experimental consistiu de 500 plantas de couve; a unidade de amostra foi a folha. Na estação de 1980/81, em paralelo, estimou-se a mortalidade ocasionada por parasitóides aos estágios de larva e pupa. Acompanharam-se durante todo o período de ocorrência em campo as variações nas taxas de parasitismo em relação ao nível da população da praga. As três espécies predominantes de parasitóides foram Tetrastichus sokolowskii Kurdjmov, 1912. Apanteles piccotrichosus Blanchard, 1943 e Spilochalcis sp. aff. a fulvovariegata (Cameron, 1884). Em 1981/82, o parasitismo foi estimado independentemente da densidade do hospedeiro. Para as amostras, consideraram-se apenas os dois últimos estádios larvais. Nas condições em que foram realizados os experimentos, a ocorrência de P. xylostella e de seu complexo de parasitóides restringiu-se a um curto período do ano. Fora deste, a ocorrência da praga foi esporádica e insignificante na cultura, o que pode ser atribuido, ao menos em parte, à associação entre o fotoperíodo e temperaturas vigentes nas condições locais, uma vez que estes dois fatores estiveram freqüentemente acima ou abaixo do ótimo para a fecundidade de P. xylostella. T. sokolowskii foi o parasitóide dominante do complexo verificado. Esta espécie é aqui, pela primeira vez registrada para a América do Sul. Aspectos relevantes para a avaliação de sua eficiência como agente de mortalidade de P. xylostella, foram estudados em condições controladas de laboratório. Verificaram-se os seguintes aspectos: tamanho dos indivíduos da progênie resultante de diferentes relações numéricas hospedeiro:parasitóide; órgãos internos de reprodução das fêmeas; duração do período pré-emergência (ovo, larva, pupa); longevidade dos adultos; fecundidade das fêmeas do parasitóide; alterações na fecundidade das fêmeas quando se promove privação de hospedeiros por períodos determinados e em condições alternadas de abundância e escassez de hospedeiros; número de indivíduos emergidos por hospedeiro nas diferentes relações numéricas parasitóide:hospedeiro; número de hospedeiros atacados nas diferentes relações numéricas parasitóide: hospedeiro; proporção de sexos da progênie em condições de abundância de hospedeiros. Todos os experimentos levaram em consideração o tamanho das fêmeas do parasitóide. Os resultados dos trabalhos de campo e de laboratório indicam que T. sokolowskii possue atributos que lhe conferem características de um eficiente inimigo natural de P. xylostella: alta capacidade de busca quando de baixas densidades do hospedeiro; sincronização com o hospedeiro em campo; facilidade de criação em insetário; proporção de sexos com forte preponderância de fêmeas; acasalamento entre irmãos de uma mesma progênie ("sib-sib mating"), o que diminui a ocorrência de partenogênese arrenótoca quando de baixas densidades do parasitóide; longevidade suficiente para permitir o ataque a um grande número de hospedeiros; fecundidade alta; capacidade de acumular ovos quando da ausência de hospedeiros; capacidade de regular o número de ovos depositados em cada hospedeiro, evitando o superparasitismo. A especificidade de hospedeiro, conforme se depreende da literatura, se adiciona a estas características. Os resultados indicam, também, a conveniência de trabalhar-se em condições conhecidas de relação numérica hospedeiro:parasitóide em programas de liberação em campo do parasitóide para o controle de P.xylostella. / The abundance of the larval and pupal stage of the diamond-back moth Plutella xylostella (Linnaeus, 1758) was estimated in a kale crop. Samples were taken at regular intervals; the sampling unit was the leaf. The experiments were carried out in 1980/81. The experimental area was sited at the "Estação Experimental Fitotécnica de Viamão", Águas Claras district, Viamão County, RS. The sampling universe was 500 plants of Brassica oleracea L. var. acephala D C. Mortality of the larval and pupal stages due to parasitoids was estimated in 1980/81 along with the estimation of abundance of the host. In 1981/82 mortality was estimated independent of the abundance of the host. Only the two last larval stages were considered. The complex of parasitoids consisted of three main species: the eulophid Tetrastichus sokolowskii Kurdjmov, 1912, the braconid Apanteles piceotrichosus Blanchard, 1943 and the chalcid Spilochalcis sp. near fulvovariegata (Cameron, 1884). The occurrence of both P. xylostella and its parasitoids was restricted to a short period of the year (December - February). The density of larvae and pupae of P. xylostella was low throughout the sampling period. If present, from March to November numbers in the field were negligible. The scarcity in numbers might be attributed, at least in part, to the inadequate combined effect on fecundidy of photoperiod and temperature. T. sokolowskii was the main parasitoid in both seasons. This is the first record for this species for South America. Laboratory studies were conducted to determine some of the attributes of T. sokolowskii as a parasitoid of P. xylostella. Experiments were carried out under controlled laboratory conditions to assess: size of individuals of a batch of offspring as a result of different host:parasitoid ratios, female internal reproductive organs; duration of the pre-emergence period (egg, larvae, pupa); longevity of the adults; fecundity of the female parasitoid under a constant host-parasitoid ratio; fecundity under alternate conditions of scarcity and abundance of hosts; fecundity when females are deprived of hosts for a given number of days; number of hosts attacked per female; number of individuals per batch of offspring; sex ratio of the progeny under conditions of host abundance. All experiments took into account the size of the female parasitoids. The results both from field and laboratory conditions indicate that T. sokolowskii has attributes of an effective natural enemy of P. xylostella:high searching capacity, that is, the ability to find its host when the host is scarce; field occurrence synchronous with that of the host; amenability to be cultured in the insectary; primary sex ratio spanandrous; inbreeding with sib-sib mating; sufficiently long-lived females to attack a large number of hosts; high fecundity; capacity to store eggs in the absence of hosts; capacity to regulate the nunber of eggs deposited/host thus avoiding superparasitism. Futhermore, references in the literature suggest host-specificity. The results also indicate that the ratio host-parasitoid should be known in programs involving inoculative colonizations to establish T. sokolowskii for the control of P. xylostella.