Waxflower (Chamelaucium spp. and hybrids) is the singlemost important Australian export cut-flower. The major problem in waxflower trading is flower abscission after harvest. While several factors are involved, ethylene production resulting from preharvest infection with the fungus Botrytis cinerea is the most important cause. The general objectives of this study were to investigate the biology of Botrytis infecting waxflower flowers and potential elicitation of host defence against this pathogen. Effects of anti-ethylene and S-carvone treatments on Botrytis-induced flower abscission were also evaluated. Infection of flowers by Botrytis was studied on two waxflower cvs. Mullering Brook and My Sweet Sixteen using light and electron microscopy. Conidial germination and protoappressorial formation occurred within 8 h post-inoculation (hpi). Infection of most floral organs, including petals, anthers and filaments, stigma, and hypanthium, was within 24 hpi. Infection cushions on stamen bases were formed at 36 hpi by saprophytic hyphae that originated from anthers. This infection route probably gives rise to the typical tan-coloured Botrytis symptoms that appear to radiate from this part of the flower. Subcuticular hyphae were present at very high density near stamen bases. They evidently resulted at multiple penetrations from single infection cushions. Flower abscission occurred at 72 hpi. At this time, floral tube tissues remained uninfected. This temporal pattern infers the possible transmission of a signal (e.g. ethylene) upon Botrytis infection (6–36 hpi) that intiates a defence response of shedding infected flowers (72 hpi). Susceptibility of waxflower before and after harvest to B. cinerea under various environmental conditions (laboratory, greenhouse, and field) was investigated. Flowers, either on plants or on cut stems showed similar susceptibility to B. cinerea and abscised under cool temperatures (~20 ºC) and high humidity (>95% RH) conditions following infection. Compared to cv. Mullering Brook, cv. My Sweet Sixteen was somewhat more resistant to B. cinerea infection under field conditions. Constitutive and inducible antifungal compounds in waxflower flower tissues were screened in cvs. CWA Pink, Stephan’s Delight, Mullering Brook and My Sweet Sixteen using thin layer chromatography bioassays with isolates of B. cinerea and Alternaria alternata (pathogenic) and Cladosporium cladosporioides (non-pathogenic). Common inhibition zone observed at Rf 0.28–0.38, 0.46–0.56 and 0.67–0.76 contained phenolic compounds. There were at least five (cv. Mullering Brook) and one (cv. My Sweet Sixteen) inducible antifungal phenolic compounds as judged by increases in inhibition area as a result of B. cinerea infection and methyl jasmonate treatment. The total areas of B. cinerea- and MeJA-induced inhibition zones were approximately 2.0- and 2.5-folds greater, respectively, than zones from control flowers. Preharvest sprays of three different known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH), and silicon (Si), were applied to waxflower cvs. Mullering Brook and My Sweet Sixteen plants. BTH or Si sprays generally had no significant effect on postharvest Botrytis severity on either cultivar. MeJA sprays did not reduce B. cinerea on cv. Mullering Brook. MeJA slightly suppressed B. cinerea on cv. My Sweet Sixteen at 500 and 750 µM. Overall, field applications of these host plant defence elicitor chemicals as spray treatments had little effect on vase life, water uptake and relative fresh weight of the cut sprigs. Moreover, they did not appreciably suppress B. cinerea or associated postharvest floral abscission. The efficacy of combined elicitor treatments and combined pre- and postharvest MeJA treatments were assessed. Preharvest foliar applications of MeJA (1000 µM; 2 or 4 times), MeJA (1000 µM) combined with BTH (150 mg/L), and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress postharvest B. cinerea development and flower abscission from harvested sprigs. A pre- plus post-harvest 1000 µM MeJA spray treatment consistently but only slightly suppressed B. cinerea infection on flowers from both pot- and field-grown plants. Pre- and post-harvest MeJA treatments reduced B. cinerea development, but increased flower abscission. Combined MeJA and anti-ethylene treatments were then screened for potential to suppress B. cinerea while preventing flower abscission. However, the combined MeJA and 1-MCP treatment reduced neither Botrytis disease nor flower abscission on sprigs from pot- and field-grown plants. The combined MeJA and STS treatment reduced disease severity for up to 6 days on sprigs harvested from pot-grown plants but tended to increase Botrytis severity on sprigs from field-grown plants 6 days after inoculation. Antifungal effects of the essential oil S-carvone against B. cinerea germination and mycelial growth were demonstrated in vitro. Inhibition increased with increasing S-carvone concentrations from 0.64 mM to 5.08 mM. However, in planta, S-carvone concentrations in this range did not affect either Botrytis disease levels or flower abscission on cut waxflower flowers.

Waxflower (Chamelaucium spp. and hybrids) is the singlemost important Australian export cut-flower. The major problem in waxflower trading is flower abscission after harvest. While several factors are involved, ethylene production resulting from preharvest infection with the fungus Botrytis cinerea is the most important cause. The general objectives of this study were to investigate the biology of Botrytis infecting waxflower flowers and potential elicitation of host defence against this pathogen. Effects of anti-ethylene and S-carvone treatments on Botrytis-induced flower abscission were also evaluated. Infection of flowers by Botrytis was studied on two waxflower cvs. Mullering Brook and My Sweet Sixteen using light and electron microscopy. Conidial germination and protoappressorial formation occurred within 8 h post-inoculation (hpi). Infection of most floral organs, including petals, anthers and filaments, stigma, and hypanthium, was within 24 hpi. Infection cushions on stamen bases were formed at 36 hpi by saprophytic hyphae that originated from anthers. This infection route probably gives rise to the typical tan-coloured Botrytis symptoms that appear to radiate from this part of the flower. Subcuticular hyphae were present at very high density near stamen bases. They evidently resulted at multiple penetrations from single infection cushions. Flower abscission occurred at 72 hpi. At this time, floral tube tissues remained uninfected. This temporal pattern infers the possible transmission of a signal (e.g. ethylene) upon Botrytis infection (6–36 hpi) that intiates a defence response of shedding infected flowers (72 hpi). Susceptibility of waxflower before and after harvest to B. cinerea under various environmental conditions (laboratory, greenhouse, and field) was investigated. Flowers, either on plants or on cut stems showed similar susceptibility to B. cinerea and abscised under cool temperatures (~20 ºC) and high humidity (>95% RH) conditions following infection. Compared to cv. Mullering Brook, cv. My Sweet Sixteen was somewhat more resistant to B. cinerea infection under field conditions. Constitutive and inducible antifungal compounds in waxflower flower tissues were screened in cvs. CWA Pink, Stephan’s Delight, Mullering Brook and My Sweet Sixteen using thin layer chromatography bioassays with isolates of B. cinerea and Alternaria alternata (pathogenic) and Cladosporium cladosporioides (non-pathogenic). Common inhibition zone observed at Rf 0.28–0.38, 0.46–0.56 and 0.67–0.76 contained phenolic compounds. There were at least five (cv. Mullering Brook) and one (cv. My Sweet Sixteen) inducible antifungal phenolic compounds as judged by increases in inhibition area as a result of B. cinerea infection and methyl jasmonate treatment. The total areas of B. cinerea- and MeJA-induced inhibition zones were approximately 2.0- and 2.5-folds greater, respectively, than zones from control flowers. Preharvest sprays of three different known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH), and silicon (Si), were applied to waxflower cvs. Mullering Brook and My Sweet Sixteen plants. BTH or Si sprays generally had no significant effect on postharvest Botrytis severity on either cultivar. MeJA sprays did not reduce B. cinerea on cv. Mullering Brook. MeJA slightly suppressed B. cinerea on cv. My Sweet Sixteen at 500 and 750 µM. Overall, field applications of these host plant defence elicitor chemicals as spray treatments had little effect on vase life, water uptake and relative fresh weight of the cut sprigs. Moreover, they did not appreciably suppress B. cinerea or associated postharvest floral abscission. The efficacy of combined elicitor treatments and combined pre- and postharvest MeJA treatments were assessed. Preharvest foliar applications of MeJA (1000 µM; 2 or 4 times), MeJA (1000 µM) combined with BTH (150 mg/L), and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress postharvest B. cinerea development and flower abscission from harvested sprigs. A pre- plus post-harvest 1000 µM MeJA spray treatment consistently but only slightly suppressed B. cinerea infection on flowers from both pot- and field-grown plants. Pre- and post-harvest MeJA treatments reduced B. cinerea development, but increased flower abscission. Combined MeJA and anti-ethylene treatments were then screened for potential to suppress B. cinerea while preventing flower abscission. However, the combined MeJA and 1-MCP treatment reduced neither Botrytis disease nor flower abscission on sprigs from pot- and field-grown plants. The combined MeJA and STS treatment reduced disease severity for up to 6 days on sprigs harvested from pot-grown plants but tended to increase Botrytis severity on sprigs from field-grown plants 6 days after inoculation. Antifungal effects of the essential oil S-carvone against B. cinerea germination and mycelial growth were demonstrated in vitro. Inhibition increased with increasing S-carvone concentrations from 0.64 mM to 5.08 mM. However, in planta, S-carvone concentrations in this range did not affect either Botrytis disease levels or flower abscission on cut waxflower flowers.

Waxflower (Chamelaucium spp. and hybrids) is the singlemost important Australian export cut-flower. The major problem in waxflower trading is flower abscission after harvest. While several factors are involved, ethylene production resulting from preharvest infection with the fungus Botrytis cinerea is the most important cause. The general objectives of this study were to investigate the biology of Botrytis infecting waxflower flowers and potential elicitation of host defence against this pathogen. Effects of anti-ethylene and S-carvone treatments on Botrytis-induced flower abscission were also evaluated. Infection of flowers by Botrytis was studied on two waxflower cvs. Mullering Brook and My Sweet Sixteen using light and electron microscopy. Conidial germination and protoappressorial formation occurred within 8 h post-inoculation (hpi). Infection of most floral organs, including petals, anthers and filaments, stigma, and hypanthium, was within 24 hpi. Infection cushions on stamen bases were formed at 36 hpi by saprophytic hyphae that originated from anthers. This infection route probably gives rise to the typical tan-coloured Botrytis symptoms that appear to radiate from this part of the flower. Subcuticular hyphae were present at very high density near stamen bases. They evidently resulted at multiple penetrations from single infection cushions. Flower abscission occurred at 72 hpi. At this time, floral tube tissues remained uninfected. This temporal pattern infers the possible transmission of a signal (e.g. ethylene) upon Botrytis infection (6–36 hpi) that intiates a defence response of shedding infected flowers (72 hpi). Susceptibility of waxflower before and after harvest to B. cinerea under various environmental conditions (laboratory, greenhouse, and field) was investigated. Flowers, either on plants or on cut stems showed similar susceptibility to B. cinerea and abscised under cool temperatures (~20 ºC) and high humidity (>95% RH) conditions following infection. Compared to cv. Mullering Brook, cv. My Sweet Sixteen was somewhat more resistant to B. cinerea infection under field conditions. Constitutive and inducible antifungal compounds in waxflower flower tissues were screened in cvs. CWA Pink, Stephan’s Delight, Mullering Brook and My Sweet Sixteen using thin layer chromatography bioassays with isolates of B. cinerea and Alternaria alternata (pathogenic) and Cladosporium cladosporioides (non-pathogenic). Common inhibition zone observed at Rf 0.28–0.38, 0.46–0.56 and 0.67–0.76 contained phenolic compounds. There were at least five (cv. Mullering Brook) and one (cv. My Sweet Sixteen) inducible antifungal phenolic compounds as judged by increases in inhibition area as a result of B. cinerea infection and methyl jasmonate treatment. The total areas of B. cinerea- and MeJA-induced inhibition zones were approximately 2.0- and 2.5-folds greater, respectively, than zones from control flowers. Preharvest sprays of three different known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH), and silicon (Si), were applied to waxflower cvs. Mullering Brook and My Sweet Sixteen plants. BTH or Si sprays generally had no significant effect on postharvest Botrytis severity on either cultivar. MeJA sprays did not reduce B. cinerea on cv. Mullering Brook. MeJA slightly suppressed B. cinerea on cv. My Sweet Sixteen at 500 and 750 µM. Overall, field applications of these host plant defence elicitor chemicals as spray treatments had little effect on vase life, water uptake and relative fresh weight of the cut sprigs. Moreover, they did not appreciably suppress B. cinerea or associated postharvest floral abscission. The efficacy of combined elicitor treatments and combined pre- and postharvest MeJA treatments were assessed. Preharvest foliar applications of MeJA (1000 µM; 2 or 4 times), MeJA (1000 µM) combined with BTH (150 mg/L), and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress postharvest B. cinerea development and flower abscission from harvested sprigs. A pre- plus post-harvest 1000 µM MeJA spray treatment consistently but only slightly suppressed B. cinerea infection on flowers from both pot- and field-grown plants. Pre- and post-harvest MeJA treatments reduced B. cinerea development, but increased flower abscission. Combined MeJA and anti-ethylene treatments were then screened for potential to suppress B. cinerea while preventing flower abscission. However, the combined MeJA and 1-MCP treatment reduced neither Botrytis disease nor flower abscission on sprigs from pot- and field-grown plants. The combined MeJA and STS treatment reduced disease severity for up to 6 days on sprigs harvested from pot-grown plants but tended to increase Botrytis severity on sprigs from field-grown plants 6 days after inoculation. Antifungal effects of the essential oil S-carvone against B. cinerea germination and mycelial growth were demonstrated in vitro. Inhibition increased with increasing S-carvone concentrations from 0.64 mM to 5.08 mM. However, in planta, S-carvone concentrations in this range did not affect either Botrytis disease levels or flower abscission on cut waxflower flowers.

A interacao planta-patogeno desencadeia uma serie de sinais que ainda nao estao completamente elucidados. Uma das respostas e a reacao de hipersensibilidade (RH), onde ocorre a morte celular programada no sitio da infeccao, impedindo a proliferacao do patogeno. Acredita que a morte celular e provocada pelo aumento do ERO, principalmente peroxido de hidrogenio (H2O2) e com o acumulo de acido salicilico (AS) que inibe a catalase, enzima responsavel pela transformacao de H2O2 em H2O e O2. Alem disso, ocorre o aumento da sintese e liberacao dos compostos fenolicos e alteracao da parede celular dos vegetais, com o aumento das atividades de diversas enzimas, capazes de degradar a parede celular da planta e do microrganismo invasor, liberando fragmentos que podem atuar como moleculas sinalizadoras, tornando as plantas mais resistentes. Nesse trabalho as celulas de Rubus fruticosus (amora-preta) foram tratadas, separadamente, com tres diferentes moleculas elicitoras, ou seja, moleculas capazes de ativar o mecanismo de defesa das plantas, o acido salicilico (AS), o metil jasmonato (MeJA) e ramnoglucuronogalactana (F-I), na concentracao de 1 Êmol/L durante 1h, para o estudo dos componentes extracelulares liberados e das modificacoes dos monossacarideos da parede celular durante resposta de hipersensibilidade. A concentracao de proteinas totais extracelulares foi aumentada com os indutores F-I e MeJA. A atividade enzimatica de -D-xilosidase nao se alterou na presenca de F-I, AS e MeJA. Entretanto, o MeJA tem a capacidade de aumentar as atividades das enzimas -D-galactosidase, -Dglucosidase, quitinase e laminarinase e inibir as atividades das enzimas galacturonase e -Lfucosidase na concentracao e tempo usado. O AS e F-I provocaram um aumento nas atividades de galacturonase e quitinase e inibiram a laminarinase. A aplicacao exogena de F-I e AS induziram a liberacao de compostos fenolicos para meio extracelular, que provavelmente, foi decorrente da tentativa das celulas de se protegerem de microrganismos invasores, com um decrescimo desses compostos no meio intracelular. O MeJA nao foi capaz de alterar a sintese de compostos fenolicos totais intracelulares e extracelulares e de acucares extracelulares, em tais condicoes. Tambem F-I e AS nao alteraram o teor de acucar redutor extracelular. O MeJA foi mais efetivo na producao de ERO durante 30 minutos de incubacao na concentracao de1 Êmol/L . F-I foi tambem ativador na liberacao de ERO, no entanto, o AS provocou inibicao. Os principais monossacarideos neutros que constitui a parede celular de suspensao de celulas de Rubus fruticosus sao as glucose (55-61%), arabinose (22-29%) e manose (13,8-15%). Ocorrendo em menor concentracoes os monossacarideos de fucose (0,65-1,2%), galactose (0,5-0,8%), xilose (0,5-0,8%) e ramnose (aproximadamente 0,5%).Os monossacarideos ramnose, fucose, xilose e galactose de parede celular tiveram um decrescimo na presenca do AS e um aumento na presenca de MeJA. Entretanto, o AS e o MeJA nao alteraram o percentual de arabinose, manose e glucose. O F-I foi capaz de aumentar o percentual dos monossacarideos ramnose e fucose e diminuir de glucose. Os resultados obtidos demonstram que a via de ativacao dos mecanismos de defesa da celula vegetal, induzida pelo MeJA, difere das vias ativadas pelo AS e F-I, pois o F-I e o AS induziram a liberacao de compostos fenolicos e o MeJA provocou aumento nas atividades enzimaticas, principalmente que atuam na parede celular da propria planta. O AS e o F-I foram mais efetivos no aumento das atividades enzimaticsa relacionadas a defesa da planta, as quais agem nas paredes de diversos fitopatogenos, sendo que as enzimas que podem atuar na parede celular da propria planta foram inibidas ou nao sofreram alteracao. / The plant-pathogen interactions trigger a series of signals that are not yet completely understood. One of the mechanisms is the hypersensitive response (HR), which is characterized by cell death in the infection site in order to prevent pathogen proliferation. Our previous studies with different elicitors demonstrated the correlation between the formation of reactive oxygen species (ROS) and cell wall degradation. Here, the cells were elicited with 1 mol/L salicylic acid (SA), methyl jasmonate (MeJA) or acid polysaccharide (rhamnoglucuronogalactan, F-I) (1mol/L) from characterization the extracellular components released and the modifications of the monosaccharide composition in cell wall during a hypersensitive response in Rubus fruticosus (blackberry-black).The extracellular proteins released to the extracellular were increased with the inducers molecules F-I and MeJA. The -D-xylosidase enzymatic activities didnt change in the presence of F-I, SA and MeJA. The time-course curves for -D-galactosidase, -D-glucosidase activities in fraction E were most effective for MeJA, while F-I and AS inhibited -Dgalactosidase. Also, the MeJA has ability to activate laminarinase and chitinase enzymatic activities and inhibit galacturonase and -L-fucosidase enzymatic activities. After 1h, the SA and F-I caused an increase galacturonase and chitinase activities and inhibited laminarinase enzymatic activity. Also, the time-course curves chitinase in the fraction increased with SA.The F-I and SA increased extracellular phenolic compounds, although they decreased them in the fraction I. MeJA was unable to change the synthesis of either intracellular or extracellular phenolic compounds. The data suggest that F-I and AS modulate the defense responses of plants through a via different that of MeJA. The extracellular reducing sugar didnt change with F-I, SA and MeJA.The MeJA was more effective in the release ROS incubation of 30 minutes at concentration of 1 mol/L. However, the presence of SA caused inhibition and F-I activated of ROS by cells.The main constituents of neutral sugars in the cell wall of Rubus fruticosus were glucose (55-61%), arabinose (22-29%) and mannose (13.8-15%). Minor constituents were fucose (0.65-1.2%), galactose (0.5- 0.8%), xylose (0.5-0.8%) and rhamnose (~0.5%). SA decreased the rhamnose and fucose concentrations; F-I both decreased the percentage of mannose and glucose and increased rhamnose and fucose. MeJA, in turn, increased the percentage of rhamnose, xylose and galactose. The data suggest that F-I and SA modulate the defense responses of plants through a mechanism unrelated to the MeJA via. Since the F-I and the SA induced the release phenolic compounds and the MeJA increased in enzymatic activities, mainly age in the own plant cell wall. The SA and F-I were more effective in the increasing defense enzyme-related activity of the plant that acts on the walls of several phytopathogens, and the enzymes that can act in the cell wall of the plant were inhibited or did not change.

In the first part of this research, we constructed a Genome scale Metabolic Model (GEM) of Taxus cuspidata, a medicinal plant used to produce paclitaxel (Taxol®). The construction of the T. cuspidata GEM was predicated on recent acquisition of a transcriptome of T. cuspidata metabolism under methyl jasmonate (MJ) elicited conditions (when paclitaxel is produced) and unelicited conditions (when paclitaxel is not produced). Construction of the draft model, in which transcriptomic data from elicited and unelicited conditions were included, utilized tools including the ModelSEED developed by Argonne National Laboratory. Although a model was successfully created and gapfilled by ModelSEED using their software, we were not able to reproduce their results using COBRA, a widely accepted FBA software package. Further work needs to be done to figure out how to run ModelSEED models on commonly available software. In the second part of this research, we modeled the MJ elicited/defense response phenotype in Arabidopsis thaliana. Previously published models of A. thaliana were tested for suitability in modeling the MJ elicited phenotype using publicly available computation tools. MJ elicited and unelicited datasets were compared to ascertain differences in metabolism between these two phenotypes. The MJ elicited and unelicited datasets were significantly different in many respects, including the expression levels of many genes associated with secondary metabolism. However, it was found that the expression of genes related to growth and central metabolism were not generally significantly different for the MJ+ and MJ- datasets, the pathways associated with secondary metabolism were incomplete and could not be modeled, and FBA methods did not show the difference in growth that was expected. These results suggest that behavior associated with the MJ+ phenotype such as slow growth and secondary metabolite production may be controlled by factors not easily modeled with transcriptome data alone. Additional research was performed in the area of cryosectioning and immunostaining of fixed Taxus aggregates. Protocols developed for this work can be found in Appendix B.

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2022 / The South African Avocado Industry has recently announced plans to expand exports into new markets, such as the United States (US). As a requirement for these markets, fruit of high quality must be stored at ultra-low temperature to mitigate phytosanitary risks. However, ‘Hass’ avocado fruit are susceptible to chilling injury when stored at temperatures below 3°C. Moreover, CI development resulted in uneven ripening and disease infestation due to damaged cell membranes. Therefore, the objective of this study was to evaluate the potential of methyl jasmonate (MeJA) and salicylic acid (SA) on quality maintenance of 'Hass' avocado fruit during ultra-low cold storage. Matured ‘Hass’ avocado fruit were harvested at commercial dry matter (22%). The experiment was conducted using a completely randomized design (CRD) with eight replications per treatment. Treatment concentrations for methyl jasmonate (MeJA) were 0 (control), 10 and 100 μmol•L−1 , while those for salicylic acid (SA) were 0 (control), 1.0, 2.0 and 3.0 mM. After treatments, fruit were stored at 2°C for 31 days and thereafter, ripened at ambient temperature (±25°C) until fully ripe. During ripening, fruit were evaluated for weight loss, exocarp colour, firmness, chilling injury, as well as physiological (vascular browning) and pathological disorders (fruit rot). In this study, dipping fruit in MeJA solution significantly (P < 0.05) reduced ‘Hass’ avocado fruit firmness loss. Moreover, MeJA showed a significant effect (P < 0.05) on hue angle (h°) but did not significantly affect (P > 0.05) visual colour rating, chroma (C*), lightness (L*) and weight loss. The results showed that ‘Hass’ avocado fruit treated with 10 μmol•L−1 MeJA reduced weight loss when compared with 100 μmol•L−1 MeJA from day 2 to day 8 of ripening. Overall results showed a visual change in ‘Hass’ avocado fruit exocarp colour, with eye colour changing from rating 1 (emerald-green) to 3 (olive- green) for control and fruit treated with MeJA throughout the ripening days. Furthermore, MeJA reduced ‘Hass’ avocado fruit external chilling injury, physiological and pathological disorders. With respect to SA treatments, the result showed that dipping fruit at 1.0 and 2.0 mM SA had a significant effect (P < 0.05) on reducing firmness loss during ripening. Salicylic acid (1.0 mM) reduced and alleviated ‘Hass’ avocado fruit external chilling injury during ultra-low cold storage. Furthermore, result showed that 1.0 and 2.0 mM SA treatments had significant affect (P < 0.05) on firmness loss. Moreover, a significant effect was observed on visual colour and C* but did not affect (P > 0.05) L* and h°. Fruit treated with SA showed poor exocarp colour development with extended exposure to ultra-low cold storage, as a result, developed chilling symptoms. The treatment of ‘Hass’ avocado fruit with 1.0 mM SA inhibited the incidence of fruit rot and vascular browning when compared with control and fruit treated with 2.0 and 3.0 mM SA. In conclusion, 10 and 100 μmol•L−1 MeJA and 1.0, 2.0 and 3.0 mM SA effectively preserved ‘Hass’ avocado fruit quality during storage at ultra-low temperature. / Agricultural Sector Education Training Authority (AgriSeta) and National Research Foundation (NRF)

Nos frutos, a cor é fundamental para a aceitabilidade inicial do consumidor, especialmente para os chamados \"pequenos frutos\" como morangos e framboesas, sendo um critério tradicional para a apreciação e seleção do estado de maturação. Em framboesas (Rubus idaeus), as pesquisas têm focado a síntese de antocianinas, os pigmentos mais abundantes nesta espécie. Seus precursores provem da via de biossíntese dos fenilpropanóides, porém os fatores que regulam a atividade dessa via metabólica ainda são pouco conhecidos. Sabe-se que alguns hormônios como o etileno, o ácido indol-3-acético (AIA), o ácido abscísico (ABA) e o metil-jasmonato (MJ) estão relacionados à inibição da síntese ou aumento no acúmulo destes flavonóides. Neste contexto, o objetivo do trabalho é avaliar o efeito destes fatores hormonais sobre a biossíntese de antocianinas em framboesas da cultivar (cv.) Autumn Bliss. Foram avaliados os efeitos dos hormônios sobre as características físico-químicas e fisiológicas dos frutos (açúcares solúveis, ácidos orgânicos, respiração, síntese de etileno, cor), conteúdo de compostos fenólicos e flavonóides. Também foram quantificados os níveis de AIA livre, ABA e MJ e a expressão relativa das enzimas antocianidina sintase (ANS), dihidroflavonol redutase (DFR) e do fator de transcrição MYB10, regulador da transcrição de genes da via de biossíntese de antocianinas em framboesas. As alterações mais significativas foram observadas no tratamento com MJ, para o qual os frutos apresentaram acentuada produção de etileno (sem efeito sobre a respiração) e também na cor, mais acentuada nos frutos maduros deste grupo em comparação com os frutos do grupo controle. O MJ também induziu aumento nos níveis de expressão relativa de MYB, ANS e DFR, nos dois primeiros dias pós-colheita. Outro grupo que se destacou foi o tratado com AIA por apresentar inibição na síntese de antocianinas e compostos fenólicos, a qual foi correlacionada à inibição da transcrição do MYB e ANS. O ABA por sua vez, inibiu o acúmulo de transcritos da DFR, de forma correlata ao menor acúmulo de antocianinas. Exceto pelo ACC, que não produziu efeitos significativos em nenhum dos parâmetros avaliados, os resultados indicam que o metabolismo de antocianinas deve ser regulado por múltiplos sinais hormonais. / The color is fundamental for the fruits, for the initial acceptability of the consumers, is a factor that influence the appreciation and selection of the maturity stage, especially for berries, like strawberries and raspberries. In raspberries (Rubus idaeus), the research have focused on the anthocyanin biosynthesis, the pigments most frequent on this species. Their precursors came from the phenylpropanoid pathway but the factors that regulate this metabolic pathway remain unclear. There are evidences that some phytohormones as ethylene, indole-3-acetic acid (IAA) abscisic acid (ABA) and methyl jasmonate (MJ) are related to the inhibition or increase of these flavonoids on fruits. In this context, the aim of this study is to evaluate the effect of these phytohormones on the anthocyanin pathway in raspberries Autumn Bliss. It was evaluated the effects of these phytohormones in some physico-chemical and physiologic characteristics of these fruits (soluble sugars, organic acids, respiration, ethylene biosynthesis, color), phenolic compounds and flavonoid content. Also, it was quantified the auxin, ABA and MJ levels, and the relative transcript levels of anthocyanidin synthase (ANS), dihydroflavonol 4-reductase (DFR) and the transcriptional factor MYB10, a transcriptional regulator of the anthocyanin pathway in raspberries. The most significant alterations were observed on MJ treatment, in which the ethylene production in berries reach the highest levels (without effect on the respiration) and the most intense red color on ripe fruits in comparison with the control group. MJ also induced the increase on relative expression of MYB, ANS and DFR two days after harvest prior to the anthocyanin accumulation. Other noticeable effect was detected in the IAA group in which anthocyanin synthesis and phenolic compound content were inhibited and related to the inhibition of MYB and ANS transcription. ABA inhibited the DFR transcript accumulation, related to the delay in anthocyanins synthesis in relation to control group. Except by ACC, that did not have significant effects in any of the evaluated parameters, the results suggest that the anthocyanin metabolism might be regulate for multiple hormonal signs.

Como os outros organismos, as plantas têm a habilidade de se defenderem através do reconhecimento de patógenos (resposta de hipersensibilidade - RH), causando a morte imediata das células no sítio primário da infecção, desta maneira oferecendo resistência ao seu crescimento. A RH é caracterizada pela necrose dos tecidos neste local, através de muitos sinais ainda não completamente elucidados, como a formação de radicais livres, incluindo o peróxido de hidrogênio (H2O2), e o reforço da parede celular. O objetivo deste estudo foi estabelecer a relação entre esses sinais em cultura de células de amora-preta (Rubus fruticosus). As condições experimentais para a análise da parede celular, das espécies reativas de oxigênio (EROs) e do H2O2 foram padronizadas. O polissacarídeo ácido (ramnoglucuronogalactana, F-I), o ácido salicílico (AS), e o metil jasmonato (MeJA), bem estabelecidos efetores da resposta da defesa, foram usados como elicitores. A produção das EROs e do H2O2 foram ativadas por F-I e pelo AS, seguidos da liberação de fragmentos de dissacarídeos da parede celular, aparentemente devido a sua degradação. Por outro lado, uma produção pequena de EROs e de H2O2 foram observadas na presença de MeJA, assim como um aumento de fragmentos de massa molecular mais elevada, que podem funcionar como sinais para o reforço da parede celular, indução de enzimas e para a produção de outra moléculas de defesa. Quando da elicitação, concomitante, com dois elicitores, AS + MeJA, houve a inibição da produção de EROs causada pelo MeJA e foi mantida a liberação de compostos extracelulares de massa molecular mais elevada. / Like the other organisms, plants have the ability to self-defend through recognition of pathogens (hypersensitive response - HR), causing immediate cell death at the primary infection site, thus offering resistance to their grown. The HR is characterized by necrosis of tissues in this site via many signals still not completely elucidated, like formation of free radicals including H2O2 and reinforcement of cell wall. The aim of this study was to establish the relationship between these signals in blackberry-black cell culture (Rubus fruticosus). The experimental conditions for analysis of cell wall, reactive oxygen species (ROS) and H2O2, were established. Acid polysaccharide (rhamnoglucuronogalactan, F-I), salicylic acid (SA), and methyl jasmonate (MeJA), well established effectors of the defense response, were used as elicitors. ROS and H2O2 production was activated by F-I and SA, followed by release of fragments like disaccharides from the cell wall, apparently due to its degradation. By contrast, a small production of ROS and H2O2 was observed in presence of MeJA, as well as an increase of high molecular weight fragments, that may function as signals for reinforcement of cell wall, enzyme induction and production of others defense molecules. Together, the two elicitors SA and MeJA inhibited the ROS production, caused by MeJA, while sustaining release of the extra cellular compounds of high molecular weight.

Terpenes and phenols are of importance in conifer defense against insects and pathogens. Knowledge about tree chemical defense is vital for developing practical methods to maintain healthy forests. With the aims of characterizing the defensive chemical induction in Norway spruce Picea abies and demonstrating its ecological function to spruce bark beetle Ips typographus, we measured the terpenoid and phenolic content in the bark of mature Norway spruce trees suffering windstorm, inoculated with Ceratocystis polonica, or treated with methyl jasmonate (MeJA), and investigated the colonization and pheromone emission of I. typographus. All three stressors altered the chemical profile in the bark of Norway spruce. Trees damaged by windstorm had lower proportions of (+)-3-carene and two unidentified stilbenes, and a higher taxifolin glycoside content than trees without apparent windstorm damage; C. polonica inoculation induced extremely strong quantitative terpene accumulation in the wound reaction zone, but only increased the levels of (+)-3-carene, sabinene and terpinolene in the bark near the reaction zone; MeJA treatment generally elicited quantitative terpene accumulation, but the induction differed extensively between individual trees. In addition, logs from MeJA-treated tree showed much stronger wounding response compared to control logs. The chemical profile of Norway spruce affected the colonization and pheromone emission of I. typographus. In response to fungal inoculation, terpene present in the reaction zone inhibited the colonization of I. typographus in a dose-dependent manner. Host defense elicited by MeJA treatment reduced emissions of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two key aggregation pheromone components of I. typographus, and altered the ratio between the two components. / QC 20110503

Made available in DSpace on 2014-07-29T15:16:31Z (GMT). No. of bitstreams: 1 Dissertacao de Mestrado Marilia.pdf: 852367 bytes, checksum: 8be87e653d87766bc06bb6d29f5cb94e (MD5) Previous issue date: 2011-11-26 / Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen that causes the disease known as white mold in many plants. During infection, it secretes several endopolygalacturonases (PGs) to degrade cell wall pectin. To counteract the action of PGs, plants express polygalacturonases-inhibiting proteins (PGIPs) that reduce the hydrolytic activity of endo-PGs and favor the accumulation of oligogalacturonides (OGs) with are elicitors of a variety of defense responses. PGIPs belong to the superfamily of leucine rich repeat (LRR) proteins and play important roles in resistance to infection of pathogens. In this study, real time RT-PCR was used to evaluate the expression of Pvpgip genes in dry bean plants (Phaseolus vulgaris L) submitted to different stress conditions. Transcriptional analysis showed that these genes are differentially expressed and activated by biotic (S. sclerotiorum infection) and abiotic (wound or methyl jasmonate treatment) stresses. Pvpgip1 was induced at early stages of the infection especially for plants treated with methyl jasmonate (MeJA) in which the transcript accumulation was higher. High levels of Pvpgip2 and Pvpgip3 expression were observed in infect plants treated or not with MeJA. All treatments showed induction of gene Pvpgip4. These results show that the/ four genes Pvpgip respond differently to treatment with the resistance inducer, fungal infection and wound. / Sclerotinia sclerotiorum (Lib.) de Bary é um fungo necrotrófico patogênico causador da doença conhecida como mofo branco em muitas plantas. Durante a infecção, secreta várias endopoligalacturonases (endo-PGs) que degradam a pectina da parede celular da planta hospedeira. Para contrapor à ação das PGs, as plantas produzem proteínas inibidoras de poligalacturonases (PGIPs) que reduzem a atividade hidrolítica das endo-PGs e favorecem o acúmulo de oligogalacturonídeos (OGs) que são indutores de uma variedade de respostas de defesa. As PGIPs pertencem à superfamília de proteínas ricas em repetições de leucina (LRR), e desempenham um papel importante na resistência à infecção de patógenos. Neste estudo, RT-PCR em tempo real foi usada para avaliar a expressão de genes Pvpgip em plantas de feijão comum (Phaseolus vulgaris L.) submetidas a diferentes condições de estresse. A análise transcricional mostrou que estes genes são ativados por fatores bióticos (infecção por S. sclerotiorum) e abióticos (injúria ou tratamento com metil jasmonato) e que existe uma variação em termos de expressão. Pvpgip1 foi induzido nos estágios iniciais da infecção, principalmente para as plantas tratadas com metil jasmonato (MeJA) em que o acúmulo deste transcritos foi maior. Altos níveis de expressão dos genes Pvpgip2 e Pvpgip3 foram observados nas plantas tratadas ou não com MeJA. Todos os tratamentos mostraram indução do gene Pvpgip4. Estes resultados mostraram que os quatro genes Pvpgip respondem diferentemente ao tratamento com indutor de resistência, infecção por fungo e injúria.