Made available in DSpace on 2015-08-20T17:10:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-03. Added 1 bitstream(s) on 2015-08-20T17:26:03Z : No. of bitstreams: 1 000843406.pdf: 1189340 bytes, checksum: 7b3c890f6719ea226d3e0cc9593afda4 (MD5) / Huanglongbing (HLB) ou greening é uma doença que, no Brasil, está associada às bactérias Candidatus Liberibacter asiaticus e a Ca. L. americanus, ambas transmitidas pelo inseto Diaphorina citri Kuwayama (Hemiptera: Liviidae). O HLB uma doença altamente destrutiva e de difícil controle, sendo atualmente Ca. L. asiaticus a mais frequentemente encontrada nos pomares. Nenhuma variedade explorada comercialmente é resistente ao patógeno ou ao inseto vetor. Visando suprir as necessidades dos produtores por porta-enxertos mais produtivos e que promovam redução no volume da copa, diversos híbridos têm sido testados para uso comercial nos últimos anos. Sobre esses novos híbridos nada se sabe sobre seu potencial em limitar o desenvolvimento da bactéria do HLB ou do inseto vetor, características que poderiam ser úteis no manejo da doença. Em vista disso, o objetivo do presente trabalho foi avaliar taxas de multiplicação de Ca. L. asiaticus e de D. citri em cinco novos híbridos indicados para uso como porta-enxertos. Para fins de comparação foram também incluídos no estudo os porta-enxertos comerciais limoeiro 'Cravo', o citrumeleiro 'Swingle', Poncirus trifoliata, a tangerineira 'Sunki', variedade de laranja doce 'Valência', e a planta ornamental murta (Murraya exotica). A multiplicação de D. citri foi determinada em brotos jovens sadios pela contagem diária do número de ovos, ninfas e adultos gerados do acasalamento de dois casais confinados por 72 horas ou até que ovos fossem visualizados. A multiplicação de Ca. L. asiaticus foi avaliada por meio de PCR quantitativo em raízes e na parte aérea das plantas seis meses após a inoculação do caule por enxertia de ramos doentes, Influência dos genótipos foi detectada tanto na multiplicação do inseto como na multiplicação da bactéria. Maior número de ovos foi encontrado no híbrido 81G513 e na laranjeira 'Valência', e menor número em... / Huanglongbing (HLB), or greening, is a disease that in Brazil is associated to the Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, both transmitted by the insect Diaphorina citri Kuwayama (Hemiptera: Liviidae). HLB is a disease highly destructive and of difficult control. Nowadays Ca. L. asiaticus ismost frequently found in citrus orchards. No commercial variety is resistant to the pathogen or insect vector. In order to satisfy grower necessity for more productive rootstocks and that promote smaller canopies to facilitate harvesting, several new hybrids have been tested for planting in the last years, For these hibrids no information exist on their potential in limiting the multiplication of the HLB bacteria or the vector, which could be used in disease management. In view of this, the objective of the present work was to evaluate multiplication rates of Ca. L. asiaticus and D. citri on five new hybrids suitable for use as rootstocks. For comparison purposes, the commercial rootstocks 'Cravo' Rangpur lime, 'Swingle' citrumelo, Poncirus trifoliata, and 'Sunki' mandarin, the sweet orange variety 'Valencia', and the ornamental orange jasmine Murraya exotica also were included in the study. D. citri multiplication was determined in healthy young shoots by daily counting of the number of eggs, nymphs and adults generated from two adult mating pairs, after confining them for 72 hours on the shoots or until eggs were observed. Ca. L. asiaticus multiplication was evaluated by quantitative PCR on the aerial part and roots of the plants, six months after stem graft inoculation. Influence of genotypes was observed on the multiplication of the insect as well as on the multiplication of the bacteria. The higher number of eggs was found on the hybrid 81G513 and on the orange 'Valencia', and the lower number of eggs on P. trifoliata. Nymph viability was higher on orange jasmine and P. trifoliata and lower on the ...

Orientador: Silvio Aparecido Lopes / Banca: Nelson Arno Wulff / Banca: Rita de Cássia Panizzi / Resumo: Huanglongbing (HLB) ou greening é uma doença que, no Brasil, está associada às bactérias Candidatus Liberibacter asiaticus e a Ca. L. americanus, ambas transmitidas pelo inseto Diaphorina citri Kuwayama (Hemiptera: Liviidae). O HLB uma doença altamente destrutiva e de difícil controle, sendo atualmente Ca. L. asiaticus a mais frequentemente encontrada nos pomares. Nenhuma variedade explorada comercialmente é resistente ao patógeno ou ao inseto vetor. Visando suprir as necessidades dos produtores por porta-enxertos mais produtivos e que promovam redução no volume da copa, diversos híbridos têm sido testados para uso comercial nos últimos anos. Sobre esses novos híbridos nada se sabe sobre seu potencial em limitar o desenvolvimento da bactéria do HLB ou do inseto vetor, características que poderiam ser úteis no manejo da doença. Em vista disso, o objetivo do presente trabalho foi avaliar taxas de multiplicação de Ca. L. asiaticus e de D. citri em cinco novos híbridos indicados para uso como porta-enxertos. Para fins de comparação foram também incluídos no estudo os porta-enxertos comerciais limoeiro 'Cravo', o citrumeleiro 'Swingle', Poncirus trifoliata, a tangerineira 'Sunki', variedade de laranja doce 'Valência', e a planta ornamental murta (Murraya exotica). A multiplicação de D. citri foi determinada em brotos jovens sadios pela contagem diária do número de ovos, ninfas e adultos gerados do acasalamento de dois casais confinados por 72 horas ou até que ovos fossem visualizados. A multiplicação de Ca. L. asiaticus foi avaliada por meio de PCR quantitativo em raízes e na parte aérea das plantas seis meses após a inoculação do caule por enxertia de ramos doentes, Influência dos genótipos foi detectada tanto na multiplicação do inseto como na multiplicação da bactéria. Maior número de ovos foi encontrado no híbrido 81G513 e na laranjeira 'Valência', e menor número em... / Abstract: Huanglongbing (HLB), or greening, is a disease that in Brazil is associated to the Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, both transmitted by the insect Diaphorina citri Kuwayama (Hemiptera: Liviidae). HLB is a disease highly destructive and of difficult control. Nowadays Ca. L. asiaticus ismost frequently found in citrus orchards. No commercial variety is resistant to the pathogen or insect vector. In order to satisfy grower necessity for more productive rootstocks and that promote smaller canopies to facilitate harvesting, several new hybrids have been tested for planting in the last years, For these hibrids no information exist on their potential in limiting the multiplication of the HLB bacteria or the vector, which could be used in disease management. In view of this, the objective of the present work was to evaluate multiplication rates of Ca. L. asiaticus and D. citri on five new hybrids suitable for use as rootstocks. For comparison purposes, the commercial rootstocks 'Cravo' Rangpur lime, 'Swingle' citrumelo, Poncirus trifoliata, and 'Sunki' mandarin, the sweet orange variety 'Valencia', and the ornamental orange jasmine Murraya exotica also were included in the study. D. citri multiplication was determined in healthy young shoots by daily counting of the number of eggs, nymphs and adults generated from two adult mating pairs, after confining them for 72 hours on the shoots or until eggs were observed. Ca. L. asiaticus multiplication was evaluated by quantitative PCR on the aerial part and roots of the plants, six months after stem graft inoculation. Influence of genotypes was observed on the multiplication of the insect as well as on the multiplication of the bacteria. The higher number of eggs was found on the hybrid 81G513 and on the orange 'Valencia', and the lower number of eggs on P. trifoliata. Nymph viability was higher on orange jasmine and P. trifoliata and lower on the ... / Mestre

Orientador: Antonio Baldo Geraldo Martins / Coorientador: José Antonio Alberto da Silva / Banca: Letícia Ane Sizuki Nociti / Banca: Simone Rodrigues da Silva / Banca: Carlos Ruggiero / Banca: Rita de Cássia Panizzi / Resumo: O pessegueiro vem ganhando espaço em regiões produtoras de frutas do estado de São Paulo, principalmente as cultivares de baixo requerimento de frio, como o 'Aurora-1'. O umezeiro é um portaenxerto que condiciona menores volumes de copa em plantas de pessegueiro, além de possuir resistência a patógenos de solo, sendo objeto de estudo neste trabalho, avaliando-se sua clonagem por estaquia, além de sua combinação com o 'Aurora-1', por enxertia de mesa, e enraizamento simultâneo. Em ambos os trabalhos foram utilizadas as concentrações 0; 1.000; 3.000 e 5.000 mg/L de AIB para tratamento das estacas, que foram coletadas em duas situações de vegetação da planta de umezeiro: estacas herbáceas retiradas da planta adulta e estacas herbáceas retiradas da planta após 60 dias da poda de rejuvenescimento. Foram avaliados: porcentagem de sobrevivência, com folhas, calos e enraizamento das estacas, número e comprimento médio de raízes e porcentagem de enxertos vivos e com estacas enraizadas. Também foi realizado um estudo histológico, por microscopia eletrônica de varredura, das regiões de rizogênese e de contato e união da enxertia. Os materiais vegetativos propagados apresentaram melhores resultados depois de uma poda rejuvenescimento. A estaquia teve superioridade em todas as variáveis avaliadas em comparação à enxertia de mesa. O 'Rigitano' apresentou melhores resultados, sendo superado pelo Clone 15 apenas na sobrevivência dos enxertos. O uso de AIB influenciou na sobrevivência e no en... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The peach tree is becoming more popular in fruit producing regions of São Paulo, mainly cultivars with low chill requirement, such as 'Aurora-1'. The japanese apricot, as being a rootstock that conditions smallest canopy in peach plants, besides having resistance to soil pathogens, being object of this work, evaluating their cloning by cuttings and their combination in grafting with simultaneous rooting, with the 'Aurora-1'. In both studies was used the concentrations 0; 1,000; 3,000 and 5000 mg/L of IBA in two vegetation situations of mume plant: softwood cuttings taken from adult plants and softwood cuttings taken from the plant after 60 days of rejuvenation pruning. It was evaluated the rooting percentage parameters of cuttings, number and average length of roots and percentage of survival of grafts with rooting cuttings. It was also conducted a histological study, by scanning electron microscopy, of the root formation zone and contact grafting. The vegetative material propagated showed better results after a rejuvenation pruning. The cuttings had superiority in all variables evaluated, in comparison to the cuttings grafted. The 'Rigitano' had the best results, being overcome by Clone 15 only in the survival of grafts. The IBA concentrations influenced the survival and rooting of cuttings and the use of IBA increased the average number of roots of cutting. / Doutor

Orientador: Renata Aparecida de Andrade / Coorientador: Rita de Cássia Panizzi / Banca: Priscila Lupino Gratão / Banca: Eduardo Custódio Gasparino / Banca: Tatiana Eugenia Cantuarias Avilés / Banca: Simone Rodrigues da Silva / Abstract: The tests in this study aimed to approach the answer to the question : The progeny of avocado tolerant rootstocks keeps the tolerance to to Phytophthora cinnamomi. Moreover aimed at addressing issues related to the in vitro establishment of explants of Duke 7 and Toro canyon cultivars. / Resumo: Os testes relacionados neste trabalho objetivaram se aproximar da resposta da pergunta: A progênie de matrizes de abacateiro tolerantes a Phytophthora cinnamomi mantém a tolerância dos parentais. Alem disso visaram abordar aspectos relacionados à introdução in vitro de explantes dos materiais Duke 7 e Toro canyon. / Doutor

Made available in DSpace on 2014-08-20T14:22:02Z (GMT). No. of bitstreams: 1 Dissertacao_Cari_Rejane_Fiss_Timm.pdf: 2144316 bytes, checksum: 8518bdcc9f7f00d5f3091fdfc5e0d2dc (MD5) Previous issue date: 2011-04-04 / The modern horticulture is based on the use of rootstocks that allow growing most of the cultivars in different climates and regions. However, there are few options of available rootstocks and researches are relatively recent. The use of sexually propagated rootstocks is one of the main problems that the peach crop shows in Brazil, concerning the lack of plant homogeneity which affects orchard yields. In order to solve the heterogeneity problem clonal propagation has been a promising alternative to produce homogenous plants with low costs, speed in the plant production process and maintenance of important agronomical characteristics. Therefore, this work aimed to evaluate the technical viability of the propagation of peach rootstocks (Capdeboscq, Aldrighi, Nemared, Nemaguard, Flordaguard and Okinawa) by herbaceous minicuttings. Also, it was tested different concentrations of IBA and substrates to improve rooting rates. The work consisted of three experiments with different evaluations: 1) the effect of four concentrations of IBA (0, 1.000, 2.000 or 3.000 mg L-1) on rooting of herbaceous minicuttings of five peach rootstocks (Capdeboscq, Aldrighi, Nemared, Nemaguard and Flordaguard); 2) the rooting of herbaceous minicuttings of three peach rootstocks (Nemared, Flordaguard and Okinawa) with 2.000 mg L-1 of IBA and different substrates (medium grade vermiculite; medium grade vermiculite + sand and sphagnum peat); 3) the influence of four concentrations of IBA (0, 1.000, 2.000 or 3.000 mg L-1) on rooting of herbaceous minicuttings of three peach rootstocks (Nemared, Flordaguard and Okinawa). The experiments were carried out under controlled temperature in greenhouse at the Departamento de Fitotecnia (FAEM/UFPel/RS), from December 2009 to January 2010. After rooting period, it was observed a higher percentage of rooting in the cv. Capdeboscq (74%) when using 2.000 and 3.000mg L-1 of IBA at 60 days. Up to 55 days, the cv. Okinawa showed 81% of rooting in vermiculite. 10 Regarding to the influence of IBA (0, 1.000, 2.000 and 3.000 mg L-1) on rooting of the cvs. Nemared, Flordaguard and Okinawa, it was observed that up to 45 days the cv. Nemared showed 66% of rooting whether using the concentration 1.000mg. L-1. / A fruticultura moderna baseia-se na utilização de porta-enxertos, cujo emprego possibilita o cultivo de inúmeras espécies e cultivares-copa nos mais diversos climas e regiões. No entanto existem poucas opções de porta-enxertos disponíveis, no Brasil, para frutíferas de caroço, e os trabalhos de pesquisa nesta área são relativamente recentes. A utilização de porta-enxertos decorrente da propagação sexuada é um dos principais problemas que a cultura do pessegueiro apresenta no Brasil, refletindo na falta de homogeneidade das plantas, comprometendo a produção, a produtividade e a longevidades dos pomares. Para tentar resolver o problema da heterogeneidade, a propagação clonal é uma alternativa promissora para a produção de mudas homogêneas, com baixo custo, rapidez e manutenção das características agronômicas importantes. Neste sentido, o trabalho teve como objetivo avaliar a viabilidade técnica da propagação de algumas cultivares (portaenxertos e copa) de pessegueiro (Capdeboscq, Aldrighi, Nemared, Nemaguard, Flordaguard e Okinawa) através da miniestaquia herbácea, testando-se diferentes concentrações de AIB e substratos. Foram realizados três experimentos em condições de casa de vegetação. Os seguintes fatores e níveis foram testados: Experimento 1 - Efeito do AIB e da cultivar no enraizamento de miniestacas herbáceas de porta-enxertos de pessegueiro. Ramos herbáceos das cultivares de porta-enxertos de pessegueiro Nemared, Nemaguard, Flordaguard, além das cultivares-copa Capdeboscq e Aldrighi, foram coletados de plantas matrizes adultas no verão, para o preparo das miniestacas, que foram imersas por cinco segundos nas concentrações (0, 1.000, 2.000 e 3.000 mg L-1) de AIB, com quatro repetições de 20 miniestacas. Aos 60 dias, avaliou-se a porcentagem de enraizamento, número de raízes, comprimento médio das três maiores raízes, número de brotações e comprimento da maior brotação. Experimento 2 - Enraizamento de miniestacas a partir de ramos herbáceos, de três cultivares de porta-enxertos de pessegueiro 8 (Nemared, Flordaguard e Okinawa) sob diferentes substratos (vermiculita média; vermiculita média + areia e turfa de sphagno) utilizando 2.000 mg L-1 de AIB. Experimento 3 Influência do AIB em quatro concentrações (0, 1.000, 2.000 e 3.000 mg L-1) no enraizamento de miniestacas herbáceas de três cultivares (Nemared, Flordaguard e Okinawa). Os experimentos foram conduzidos em casa de vegetação, com temperatura controlada, do Departamento de Fitotecnia, (FAEM/UFPel/RS) entre dezembro de 2009 e janeiro de 2010. Após o período de enraizamento, observou-se a maior porcentagem de enraizamento para a cv. Capdeboscq, com 74%, utilizando AIB nas concentrações de 2.000 e 3.000mg L-1, em 60 dias. Avaliando aos 55 dias o enraizamento em diferentes substratos, a cv. Okinawa obteve 81% de enraizamento na vermiculita. Em 45 dias, testando a influência do AIB em quatro concentrações (0, 1.000, 2.000 e 3.000 mg L-1) no enraizamento das cultivares Nemared, Flordaguard e Okinawa , observou-se que a cv. Nemared obteve 66% com a concentração de 1.000mg. L-1 de AIB.

Orientador: Antonio Baldo Geraldo Martins / Coorientador: Eduardo Sanches Stuchi / Banca: Carlos Ruggiero / Banca: Simone Rodrigues da Silva / Resumo: No Brasil, o uso do trifoliata 'Flying Dragon', como porta-enxerto em citros, tem crescido quando se busca pomares com altas densidades, devido, principalmente, por induzir nanismo à maioria das variedades de copa compatíveis. No entanto, por possuir desenvolvimento lento, existe a necessidade de se estudar melhor o crescimento deste porta-enxerto. A nutrição é uma importante ferramenta que visa acelerar o crescimento, melhorar o vigor e a qualidade das plantas. Diante disso, foi avaliado a aplicação de nutrientes no crescimento do porta-enxerto em ambiente protegido durante três etapas: 1ª etapa crescimento inicial em tubetes preenchidos com substrato comercial Bioplant ®, 2ª etapa pós-transplantio para sacos plásticos, 3ª etapa desenvolvimento do enxerto. Em cada etapa realizou-se três experimentos: no primeiro utilizaram-se seis doses de N parceladas; no segundo, seis doses de P (aplicadas em dose total, misturadas diretamente no substrato); e no terceiro, seis doses de K parceladas. As seis doses foram constituídas por: D0 = testemunha sem adubação; D1= metade da dose padrão; D2 = a dose padrão (920 mg dm-3 de N, 790 mg dm-3 de K e 100 mg dm-3 de P); D3 = uma vez e meia a dose padrão; D4 = duas vezes a dose padrão; e D5 = duas vezes e meia a dose padrão. Assim, coletaram-se dados biométricos do porta-enxerto de diâmetro e altura, quinzenalmente e dados de massa seca da parte aérea e raiz, mensalmente. O delineamento utilizado foi o inteiramente casualizado com parcela subdividida. As doses de N proporcionaram alterações significativas em todas as variáveis avaliadas, sendo fundamental no incremento das massas secas de raiz e da parte aérea. O P é necessário apenas na fase de tubete e o uso de K foi prejudicial / Abstract: In Brazil, the use of trifoliata 'Flying Dragon' as a rootstock of citrus has grown when seeking orchards with high densities, due mainly to induce dwarfism in the most varieties of compatible canopies. However, by having slow development, there is a need to better study the growth of the 'Flying Dragon'. Nutrition is an important tool that aims to accelerate growth, improve the vigor and quality of the plants. Therefore, was evaluated the application of nutrients in the growth of the rootstock in greenhouse during three stages: 1st stage initial growth in small tubes filled with commercial substrate Bioplant ®, 2nd stage post-transplantation for plastic bags, 3rd stage development of the graft. At each step were conducted three experiments: in the first were used six doses of nitrogen splitter, in the second six doses of phosphorus (total dose applied, mixed directly into the substrate), and the third, six doses of potassium splitter. The six doses were constituted by: D0 = control without fertilization; D1 = half the standard dose; D2 = the standard dose (920 mg dm-3 N, 790 mg dm-3 K and 100 mg dm-3 P) ; D3 = one and a half standard dose, D4 = twice the standard dose, and D5 = half times the standard dose. Thus, biometric data were collected of the rootstock every fortnight for diameter and height, and monthly for dry mass of shoots and roots. The experimental design was completely randomized with subplot. Nitrogen rates have provided significant changes in all variables, being essential in the increasing of the dry mass of root and shoot. Phosphorus is necessary only in the phase of small tube and the use of potassium was harmful / Mestre

Thesis (M.Sc. Agriculture (Horticulture)) -- University of Limpopo, 2019 / Cucurbitacin-containing phytonematicides and a variety of unidentified soil microbes in suppressive soils (Biomuti) had been consistent in suppression of population densities of root-knot (Meloidogyne spp.) nematodes on various crops. However, information on suppressive effects of cucurbitacin-containing phytonematicides and Biomuti on citrus growth and suppression of the citrus nematode (Tylenchulus semipenetrans) had not been documented. The objective of this study therefore, was to determine the interactive effects of Nemarioc-AL and Nemafric-BL phytonematicides and Biomuti on growth and nutrient elements in leaf tissues of Poncirus trifoliata rootstock seedlings under greenhouse and field conditions. Uniform six-month-old citrus rootstock seedlings [Du Roi Nursery (Portion 21, Junction Farm, Letsitele)] were transplanted in 4 L plastic bags filled with growing mixture comprising steam-pasteurised (300°C for 1 h) loam and compost (cattle manure, chicken manure, sawdust, grass, woodchips and effective microorganisms) at 4:1 (v/v) ratio and placed on greenhouse benches. A 2 × 2 × 2 factorial experiment with the first, second and third factors being Nemarioc-AL phytonematicide (A) and Nemafric-BL phytonematicide (B) and Biomuti (M), were arranged in randomized complete block design, with 10 blocks. The treatment combinations were A0B0M0, A1B0M0, A0B1M0, A0B0M1, A1B1M0, A1B0M1, A0B1M1 and A1B1M1, with 1 and 0 signifying with and without the indicated factor. Treatments were applied at 3% dilution for each product as substitute to irrigation at a 17-day application interval. Under greenhouse conditions, seedlings were irrigated every other day with 300 ml chlorine-free tap water. Under field conditions, the study was executed using similar procedures to those in the greenhouse trial, except that the citrus seedlings were transplanted directly into the soil of a prepared field and seedlings were irrigated using drip irrigation for 2 h every xxi other day. At 64 days after transplanting, plant growth variables were measured and foliar nutrient elements were quantified using the Inductively Coupled Plasma Optical Emission Spectrometry (ICPE-9000). Data were subjected to analysis of variance using SAS software. Significant second and first order interactions were further expressed using the three-way and two-way tables, respectively. At 64 days after the treatments, under greenhouse conditions Nemarioc-AL × Nemafric-BL × Biomuti interaction was not significant (P ≤ 0.05) on plant variables of seedling rootstocks in both experiments. In contrast, the Nemarioc-AL × Biomuti interaction was highly significant (P ≤ 0.01) on stem diameter, contributing 52% in TTV of the variable in Experiment 1 (Table 3.1), whereas in Experiment 2 the interaction was highly significant on dry shoot mass, contributing 33% in TTV of the variable (Table 3.2). Relative to untreated control, the two-way matrix showed that the Nemarioc-AL × Biomuti interaction, Nemarioc-AL phytonematicide and Biomuti each increased stem diameter by 1%, 12% and 5%, respectively (Table 3.3). Relative to untreated control, the two-way matrix table showed that Nemarioc-AL × Biomuti interaction increased dry shoot mass by 10%, whereas Nemarioc-AL phytonematicide and Biomuti each increased dry shoot mass by 23% and 17%, respectively (Table 3.4). Nemarioc-AL × Nemafric-BL × Biomuti interaction was not significant (P ≤ 0.05) for all plant growth variables in both experiments. However, Nemarioc-AL × Nemafric-BL interaction was significant for leaf number and stem diameter contributing 45% and 29% in TTV of the respective variables in Experiment 2 (Table 4.1). Relative to untreated control, two way matrix table showed that the Nemarioc-AL × Nemafric-BL interaction and Nemafric-BL phytonematicides each increased stem diameter by 8% and 11% respectively, whereas Nemarioc-AL phytonematicides reduced stem diameter by 2% (Table 4.2). Also using two-way matrix table showed that Nemarioc-AL and Nemafric xxii BL phytonematicides each increased leaf number by 1% and 7% respectively, whereas the Nemarioc-AL × Nemafric-BL interaction increased leaf number by 6% (Table 4.2). Nemafric-BL × Biomuti interaction was significant for stem diameter contributing 29% in TTV of the respective variable in Experiment 2 (Table 4.1). Using two-way matrix table showed that Nemafric-BL × Biomuti interaction and Nemafric-BL phytonematicide each increased stem diameter by 7%, whereas Biomuti alone reduced stem diameter by 6% (Table 4.3). Under greenhouse conditions, the second order Nemarioc-AL × Nemafric-BL × Biomuti interaction was highly significant for foliar Mg, contributing 5% in TTV of the variable in Experiment 1 (Table 3.4). Relative to untreated control, the three-way matrix table showed that the three factors, Nemafric BL phytonematicide and Biomuti each reduced Mg by 33%, 35% and 53%, respectively, whereas Nemarioc-AL phytonematicide increased Mg by 12% (Table 3.5). Nemarioc-AL × Biomuti interaction was highly significant for foliar Mg, contributing 9% in TTV of the variable in Experiment 1 (Table 3.4). Relative to untreated control, the two-way matrix table showed that the Nemarioc-AL × Biomuti interaction and Nemafric-BL phytonematicide reduced Mg by 42% and 12%, respectively, whereas Nemarioc-AL phytonematicide alone increased Mg by 14% (Table 3.6). Nemarioc-AL × Biomuti interaction was highly significant for foliar Ca and Mg, contributing 59 and 4% in TTV of the respective variables in Experiment 1 (Table 3.4). Also using two-way matrix table showed that Nemarioc-AL phytonematicide and Biomuti separately reduced Ca by 12% and 22% respectively, whereas the Nemarioc-AL × Biomuti interaction increased Ca by 1% (Table 3.7). Relative to untreated control, the Nemarioc-AL × Biomuti interaction, Nemarioc-AL phytonematicide and Biomuti reduced foliar Mg by 26%, 21% and 33%, respectively (Table 3.7). Nemafric-BL × Biomuti interaction was highly significant for foliar Mg and P, contributing 50 and 21% xxiii in Experiment 1, whereas in Experiment 2 the interaction was significant for foliar Ca and Mg, contributing 41% and 38% in TTV of the respective variables (Table 3.4). Relative to untreated control, the two-way matrix table showed that Nemafric-BL phytonematicide and Biomuti individually reduced Mg by 60% and 51%, respectively, whereas the Nemafric-BL × Biomuti interaction reduced Mg by 38% (Table 3.8). Also, in the two-way matrix table the Nemafric-BL × Biomuti interaction and Nemafric-BL phytonematicide each reduced Mg by 13% and 2%, respectively, whereas Biomuti alone increased P by 17% (Table 3.8). Relative to untreated control, Nemafric-BL phytonematicide and Biomuti reduced Ca by 29% and 18%, respectively, whereas Nemafric-BL × Biomuti interaction reduced Ca by 14% (Table 3.9). Using two-way matrix table showed that Nemafric-BL phytonematicide and Biomuti separately reduced Mg by 21%, whereas the Nemafric-BL × Biomuti interaction reduced Mg by 16% (Table 3.9). Interaction of Nemarioc-AL × Nemafric-BL × Biomuti had no significant effect on K, Na and Zn in both experiments. Under field conditions, the second order Nemarioc-AL × Nemafric-BL × Biomuti interaction was not significant for all the nutrient elements in Experiment 1. Nemarioc-AL × Biomuti was significant for Ca, K and highly significant for Mg and P, contributing 31, 8, 23 and 19% in TTV of the respective variables in Experiment 1 (Table 4.4). Relative to untreated control, two-way matrix table showed that Nemarioc-AL phytonematicide and Biomuti each increased Ca by 15% and 26% repectiviely, whereas the Nemarioc-AL × Biomuti increased Ca by 17% (Table 4.5). Interaction of Nemarioc-AL × Biomuti, Nemarioc-AL phytonematicide and Biomuti each reduced Mg by 48%, 70% and 37% (Table 4.5). Also using two-way matrix table showed that Nemarioc-AL phytonematicide and Biomuti each increased P by 4% and 5% respectively, whereas the Nemarioc-AL × Biomuti interaction increased P by 50% (Table 4.5). Realative to untreated control, xxiv Biomuti and Nemarioc-AL phytonematicide each reduced K by 10% and 5% respectively, whereas the Nemarioc-AL × Nemafric-BL interaction reduced K by 38% (Table 4.7). Nemafric-BL × Biomuti interaction was highly significant for Mg and Zn, contributing 11% and 29% in TTV of the respective variables in Experiment 1 (Table 4.4). Relative to untreated control, two-way matrix table showed that Nemarioc-AL phytonematicide and Biomuti separately increased Mg by 1% and 19% respectiviely, whereas the Nemafric-BL × Biomuti interaction reduced Mg by 43% (Table 4.6). Nemafric-BL × Biomuti interaction, Nemafric-BL phytonematicide and Biomuti each reduced Zn by 35%, 31% and 64% (Table 4.6). Using three-way matrix table showed that the Nemarioc-AL × Nemafric-BL × Biomuti, Nemarioc-AL × Nemafric-BL, Nemarioc-AL × Biomuti and Nemafric-BL × Biomuti interactions each increased Ca by 44%, 18%,10% and 24% (Table 4.8). Further the matrix showed that Nemarioc-AL, Nemafric-BL phytonematicides and Biomuti each increased Ca by 25%, 31% and 23% (Table 4.8). Under both greenhouse and field conditions, although second and first order interactions were not consistent of various variables, results demonstrated that the three products interacted significantly for various products. In conclusion, the study suggested that these innovative products could be used in combination with Biomuti to stimulate plant growth but had antagonistic effects on accumulation of nutrient elements in P. trifoliata rootstock seedlings, suggesting that the products should be applied separately. / Agricultural Research Council-Universities Collaboration Centre and the National Research Foundation (NRF)

Mechanisms of root growth under variable field conditions were investigated by observing corn ( Zea mays L.) root growth and distribution in the field and by observing the influence of soil physical stresses on corn seedling root growth in controlled environments. The field soil was Groseclose silt loam (clayey, mixed, mesic Typic Hapludult). Groseclose A horizon material was used for the growth chamber experiments where corn was grown in a range of aggregate sizes, bulk densities, low and high soil moisture levels, and temperatures. Rooting patterns in the field were altered by drought. Root length density decreased in the dry surface soil and proliferated in the moist subsurface soil. Distribution of roots length densities was skewed. A few samples contained many roots and many samples contained few roots because roots were restricted to interpedal voids. In the growth chamber experiments, roots were not able to penetrate large aggregates and were restricted to interaggregate zones. This tortuous path of root growth led to transitory impedances as roots were deflected around aggregates. Corn roots were able to push small aggregates out of their path. An equation was developed to describe this impedance as a function of aggregate size, root diameter, and deflection angle. Mechanical impedance, oxygen stress, lower temperatures, and moisture stress reduced seedling root elongation to some extent, but the influence of reduced temperature was the most dramatic. At 6 days corn root length at 21°C was 20% of that at 25°C while root length at 17°C was only 5% of that at 25°C. Mechanical impedance and reduced temperatures also increased root diameter. In wet soil, oxygen stress was the most immediate factor affecting root growth, but after 4 days root elongation was stimulated suggesting other unknown factors. Two semi-empirical models were developed. One was based on the exponential growth rate of the root system and the other based on the linear growth rate of each root member. These models accounted for the reduction in root growth rate due to the soil physical stresses. / Ph. D.

Laranjeiras ‘Valência’ enxertadas em citrandarins e outros híbridos de trifoliata foram plantadas em 1988, em Itirapina (SP), num Latossolo Vermelho-amarelo-textura arenosa e conduzidas sem irrigação. Os citrandarins Sunki x English (1.628), Cleópatra x Rubidoux (1.660) e Cleópatra x English (710), induziram as maiores produções de frutos nas cinco e nas treze colheitas. Os citranges ‘Troyer’ e ‘Carrizo’ foram significativamente menos produtivos que o Sunki x English (1.628) nas cinco primeiras e no total das treze colheitas. Os citrandarins Clementina x Trifoliata (1.615), Cleópatra x Swingle, seleções (715) e (1.614), Cleópatra x Rubidoux (1.600) e Cleópatra x Christian (712) induziram plantas nanicas. Sunki x English (1.628), ‘Troyer’ e ‘Carrizo’ proporcionaram as maiores plantas e lideraram a produção de frutos e de sólidos solúveis no período 2001-2003. Nenhuma planta mostrou sintomas de suscetibilidade à tristeza ou ao declínio. As plantas enxertadas no trangpur Cravo x Carrizo (717), mostraram sintoma de incompatibilidade na região de enxertia. "Seedlings" dos citrandarins Cleópatra x Swingle (1.587), Cleópatra x Trifoliata (1.574) e Cleópatra x Rubidoux (1.600) foram mais resistentes à gomose de Phytophthora parasitica que os demais porta-enxertos. / ‘Valência’ sweet orange trees budded onto citrandarins and others trifoliate hybrids rootstocks were planted in 1988 on a sandy textured Oxisol in São Paulo state, Brazil, and managed without irrigation. Tristeza and blight diseases are endemic in the area. Trees on Sunki x English (1628), Cleopatra x Rubidoux (1660) and Cleopatra x English (710), produced the highest cumulative yields in the first five and in the thirteen crops. ‘Carrizo’ and ‘Troyer’ citranges gave the lowest productions in the first five yields but were similar to Sunki x English (1628) in 13-years cumulative yields. Clementine x Trifoliate (1615), Cleopatra x Swingle (715) and (1614) selections, Cleopatra x Rubidoux (1600) and Cleopatra x Christian (712) induced dwarfed trees. Sunki x English (1628) and ‘Troyer’ and ‘Carrizo’ citranges induced the largest trees and fruit and soluble solids production by tree in the 2001-2003 period. None tree showed symptoms of tristeza or declinio. Trees on Cravo x Carrizo (717) showed bud-union-ring symptom of incompatibility. Seedlings of Cleopatra x Swingle (1587), Cleopatra x Trifoliate (1574) and Cleopatra x Rubidoux (1600) were more resistent to Phytophthora parasitica infections than the others rootstocks.

Thesis (M.Sc. (Plant protection)) --University of Limpopo, 2013. / Studies were initiated to investigate (1) the aggressiveness of the citrus nematode (Tylenchulus semipenetrans Cobb) isolates from two provinces in South Africa (2 experiements ) and (2) the biotype of T. semipenetrans in South Africa. In the aggressive study, isolates from Limpopo and Mpumalanga Provinces were used on Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and rough lemon (Citrus jambhiri) seedling rootstocks under greenhouse conditions (18 experiements). Each seedling was inoculated with 0, 10 000, 20 000, 30 000 and 40 000 J2s of T. semipenetrans isolates, which were arranged in a randomised complete block design, with six replications. At 120 days, the reproductive factor of T. semipenetrans isolate from Mpumalanga Province was significantly higher than that from Limpopo Province. Similarly, due to its higher relative impact on the reproductive factor values, the Mpumalanga isolate reduced plant growth variables more than the Limpopo isolate. Consequently, the Mpumalanga isolate was viewed as being more aggressive than the Limpopo isolate, suggesting that there might be genetic variability and/or adaptation in populations from the two locations. A national study, comprising T. semipenetrans isolates from 18 citrus-producing district municipalities in South Africa was then initiated under greenhouse conditions using isolates from each district – for a total of 18 separate experiments. Three differential hosts, viz. rough lemon, P. trifoliata and olive (Olea europaea), served as treatments, arranged in a randomised complete block design, with 15 replications. Initially, an orchard was randomly selected in each of the six citrus-producing provinces, viz. Eastern Cape, KwaZulu Natal, Limpopo, Mpumalanga, North West and Western Cape. Three-month old differential host seedlings were inoculated with approximately 10 000 J2s of T. semipenetrans and allowed to establish and grow under greenhouse conditions. At 120 days, penetration indices and standardised reproductive potentials/g roots demonstrated that T. semipenetrans failed to reproduce and develop on olive, but reproduced and developed on the other two hosts. Using T. semipenetrans biotype classification system, findings suggested that the biotype in citrus-producing district municipalities was Poncirus biotype. This biotype reproduces on P. trifoliata and hybrid rootstocks, which therefore, suggested that trifoliate orange and its hybrid rootstocks were not suitable for use in managing population nematode densities of T. semipenetrans in South Africa. In conclusion, results of this study demonstrated that the South African T. semipenetrans biotype was Poncirus, which suggested different management decisions and strategies for the citrus industry with regard to the management of this nematode. / By National Research Foundation, National Department of Agriculture, Forestry and Fisheries and the Land Bank Chair of Agriculture − University of Limpopo,