This study has investigated the gene expression of ubiquitin¡B20S proteasome beta subunit type 1 (20s£]1)¡Bubiquitin-conjugating enzyme e2 (ucee2)¡BATP-dependent caseinolytic protease regulatory subunit (clpC) in the marine macroalga Ulva fasciata Delile in relation to the hypersalinity-induced oxidative stress and protein oxidation. During the early stage (0-1 h), the water contents and TTC (2,3,5-tripheny tetrazolium chloride) reduction ability maintained unchanged but recovery ability and photosynthetic ability (PS II activity as indicated by Fv/Fm) were decreased along with accumulated H2O2, suggesting the occurrence of oxidative stress. Only ubiquitin expressed at this stage. During 1-3 h, water lost (approximately 33% of the control) with a further decrease in recovery ability, TTC reduction ability¡BPS II activity but more H2O2 accumulation and protein carbonyl compound. The transcripts of 20s£]1 and clpC and caseinolytic protease activity increased at this stage with the maximum of clpC at hour 3. In the 6-48 h, water lost seriously with high accumulated free amino acid at 6-12 h but low recovery ability. The transcript amounts of ubiquitin¡B20s£]1 and ucee2 increased marked during this stage, in which these might be related to programmed cell death caused by long-term exposure to hypersalinity. Reactive oxygen species (ROS) scavengers inhibited H2O2 accumulation, caseinolytic proteolytic activity increase, carbonyl compound formation and gene expression of ubiquitin¡B20s£]1¡Bucee2¡BclpC, indicating a role of ROS in the regulation of protease genes. A role of polyamines in the regulation of protease gene expression was tested. Spermidine and spermine inhibited the gene expression of ubiquitin¡B20s£]1 and ucee2, the oxidation of proteins (carbonyl groups) and the induction of caseinolytic protease activity in 90‰-treated thalli, whereas putrescine inhibited clpC expression, the oxidation of proteins and caseinolytic protease activity but enhanced the gene expression of ubiquitin¡B20s£]1 and ucee2. In conclusion, the results of the present investigation show that the degradation of oxidatively damaged proteins under hypersalinity conditions by increased caseinolytic protease activity is driven by the up-regulation of clpC gene expression via ROS and polyamines. It seems likely that the induction of ubiquitin¡B20s£]1 and ucee2 gene expression might be associated with the hypersalinity-mediated programmed cell death.

Reduced water availability and salinity are two major environmental factors influencing crop establishment in semi-arid environments. Therefore the effect of reduced water availability using polyethylene glycol (PEG) 4000 solutions and of salinity (NaCl) on the germination of six soybean cultivars was examined. Cultivars differed in their response to reduced water availability and salinity and in their ability to recover from the stresses. A large increase in germination during a recovery period at 0 MPa following water stress suggested that PEG was not toxic whilst the failure of seeds to recover from high salinity revealed the toxic effects of NaCl. At the same water potential, germination in saline conditions was higher than that in PEG and the rate of water uptake by individual seeds was more rapid in NaCl solutions than in PEG. The most plausible explanation for the greater water uptake and germination in NaCl is that seeds accumulated salts which lowered their osmotic potential. The effects of NaCl on seedling growth were much greater when experiments were conducted in a hydroponic system compared with a paper towel method. However, analysis of the solutions soaking the paper towels revealed that 4.25<I> </I>mMolal Ca2⁺ was available to the seeds in this system in saline conditions. This may have reduced Na⁺ uptake or provided a protective effect against Na⁺ toxicity. Germination (40%) was possible at a tissue Na⁺ concentration in the embryonic axis of 9.3mg g-1 FW whilst seedling growth was completely inhibited at a tissue Na⁺ concentration of 6.1 mg g^-1FW. Germination at higher tissue Na⁺ concentrations was associated with higher K⁺+Ca2⁺ concentrations, suggesting that these ions may protect the seeds in the pregermination phase against salinity. A reduction in seed vigour due to ageing resulted in reduced germination under saline conditions compared to the germination of unaged seeds, but there was no significant interaction between salinity and seed ageing. However, unaged seeds showed a greater increase in germination after transfer to 0 MPa than did the aged seeds. Since both the site of ageing and the toxic effect of NaCl is the cell membrane, there may be additive effects of NaCl toxicity on cell membrane in aged seeds.

Plant responses to abiotic stress are neither singular nor linear. The research represented within this dissertation was intended to evaluate selected biochemical and physiological responses in two Arugulas (Images 1-5), to agronomic interventions designed to mitigate extreme environmental abiotic factors, characteristic of arid agricultural production regions. Plant stress responses were investigated under field conditions and within controlled environments (CE), during the course of a preliminary trial and three independent studies, all four directly related. The preliminary trial evaluated harvest and postharvest nutritional content (i.e., antioxidants) of two Arugulas, Eruca sativa (L.) Cav. ssp. sativa (P. Mill.) and Diplotaxis tenuifolia (L.) DC cv. Sylvetta; grown under field conditions in the semi-arid upper Sonoran Desert. In this trial, we defined baseline harvest and postharvest antioxidant values for the Arugulas, cultivated in a semi-arid environment. The initial study, conducted within a CE utilizing a water recycling system, evaluated changes in the nutritional value of three specialty leafy cruciferous vegetables: D. tenuifolia, E. sativa and Lepidium sativum; when subjected to increasing salinity levels in the nutrient solution. It was concluded that, when specific Crucifers are irrigated with moderately high levels of salinity, neither harvest nor postharvest nutritional values are compromised. The second study, investigated the response of a suite of plant physiological parameters (e.g., yield and photosynthetic rate) in the three Crucifers to salinity, within the CE. This research provided guideline salinity values where yields did not decline, and encourages growers to consider water resources compromised by salinity and nutrient solution recycling. During the third study, the influence of environmental conditions on the nutritional content in leafy vegetables, prevalent immediately before harvest, was investigated; by subjecting plants to reduced sunlight treatments and early irrigation termination. We observed that, modulating light intensity late in the season, and early irrigation termination strategies, modify the nutritional content of leafy vegetables; and potentially the subsequent postharvest shelf life. Collectively evaluated, this research suggests that simple agronomic interventions are valuable, yet practicable, tools that can enhance the nutritional content of specialty vegetables, in arid regions: be that intervention an imposed controlled-stress, utilizing nutrient recycling systems within a CE, or basic light-reduction and irrigation termination strategies within conventional fields systems.

Salinity stress is one of the main challenges for crop growth and production. The estimated loss of crop yield due to salinity stress is up to 20% worldwide each year. Plants have evolved an array of mechanisms to defend themselves against salinity stress. A key aspect of plant responses to salinity stress is the engagement of a nitrosative burst that results in nitric oxide (NO) accumulation. A major mechanism for the transfer of NO bioactivity is S-nitrosylation which is a modification of the reactive thiol group of a rare but highly active cysteine residue within a protein through the addition of a NO moiety to generate an S-nitrosothiol (SNO). S-nitrosylation can result in altered structure, function and cellular localisation of a protein. Our findings suggest that S-nitrosylation is a key regulator of plant responses to salinity stress. Glutathione (GSH), a tripeptide cellular antioxidant, is S-nitrosylated to form S-nitrosoglutathione (GSNO), which functions as a stable store of NO bioactivity. Cellular GSNO levels are directly controlled by S-nitrosoglutathione reductase (GSNOR), thereby, regulating global SNO levels indirectly. The absence of this gene results in high levels of SNOs. In Arabidopsis, previous research has shown that loss-of-function mutation in GSNOR1 results in pathogen susceptibility (Feechan et al., 2005). In our study, we investigated salt tolerance in gsnor1-3 plants. We have found that this line is salt sensitive at various stages of their life cycle. Interestingly, classical salt stress signalling pathways are fully functional in gsnor1-3 plants. We have also explored non-classical pathways involved in salt tolerance. Autophagy is a cellular catabolic process which is involved in the recycling and degradation of unwanted cellular materials under stressed and non-stressed conditions. We have demonstrated that gsnor1-3 plants have impaired autophagy during salt stress. An accumulation of the autophagy marker NBR1 supports the lack of autophagosome formation. We hypothesised that S-nitrosylation might regulate upstream nodes of autophagosome formation. Our study demonstrated that at least one key player involved in autophagosome biogenesis is regulated by S-nitrosylation. ATG7, an E1-like activating enzyme, which regulates ATG8-PE and ATG12-ATG5 ubiquitin like conjugation systems, is S-nitrosylated in vitro and in vivo. S-nitrosylation of ATG7 impairs its function in vitro. We showed that S-nitrosylation of ATG7 is mediated by GSNO. Interestingly, ATG7 is also transnitrosylated by thioredoxin (TRX), another important redox regulatory enzyme. We suggest that similar mechanisms might exist in planta. Finally, work in this study revealed that S-nitrosylation of Cys558 and Cys637 cause the inhibition of ATG7 function. In aggregate, this study revealed a novel mechanism for the redox-based regulation of autophagy during salt stress.

This research has investigated the gene expression of protein disulfide isomerase (PDI; EC 5.3.4.1) and thioredoxin (Trx) in the marine macroalga Ulva fasciata Delile in response to hypersaline (90‰) for 1 h. 90‰ induced H2O2 accumulation, reflecting the occurrence of oxidative stress. The contents of free and protein-bound SH were increased by 90‰. Trx transcripts increased in response to 90‰. PDI transcripts and enzyme activities increased in response to 90‰. H2O2 accumulation under 90‰ condition was increased by putrescine (Put) but decreased by spermidine (Spd) and spermine (Spm). By treatment of spermidine and spermine, the contents of free SH was increased and the contents of protein-bound SH decreased, showing that spermidine and spermine can increase free SH against oxidative stress. The gene expression and activity of PDI were further increased by Spd and Spm. Overall, the gene expression of PDI and Trx were responded to 90‰ for 1 hour and were adjusted protein¡VSH in polyamines treatment.

Germination of plants is one of the most important stages during their growth which is often influenced by environmental stresses, especially drought and salinity. This study was conducted to investigate the effects of salinity and drought on seed germination and growth of Lathyrus sativa. The experiment was laid out in a completely randomized design with factorial arrangement in 4 replications. Salinity treatments were 0, 2, and 4 dS/m and drought treatments included 0, 0.4, 0.8, 1.2 MPa. Salinity and drought treatments were prepared by using sodium chloride and polyethylene glycol 6000, respectively. The results showed that salinity and drought stresses decreased germination percentage, root and radicle length.

Soil salinity and heat stress are two major abiotic stresses affecting plant growth and yield. Transcription factors (TFs) are key regulators in stress responses. They link stress sensing with many tolerance mechanisms by translating stress signals into changes in gene expression that ultimately contribute to stress tolerance. The NAC (NAM, ATAF and CUC) TF family have been found to be involved in responses to biotic and abiotic stresses. In this PhD project, the role of NAC TFs in response to heat and salt stress was studied in the model system Arabidopsis thaliana (Arabidopsis), and in two agriculturally relevant species, Solanum lycopersicum (tomato) and Chenopodium quinoa (quinoa). Plants have the ability to acquire thermotolerance if they are pre-exposed to a mild, non-lethal high temperature. The maintenance of acquired thermotolerance for several days is known as thermomemory. Here we investigated the role of NAC TFs in thermotolerance. The expression profiles of 104 Arabidopsis NAC TFs were measured and compared between primed and unprimed plants. Some NACs with a distinctive expression pattern in response to thermopriming were selected for further phenotypic analysis. Knock-out (KO) mutants of the ATAF1 gene showed an enhanced thermomemory phenotype compared with wild type plants (WT) and from this work, the functions of the ATAF1 gene were studied further. RNAseq co-expression analyses of ATAF1 overexpressor and ataf1 KO plants found that ANAC055 expression was co-regulated with that of ATAF1. JUBGBRUNNEN1 (JUB1) is another NAC TF involved in responses to heat, drought and salinity. In this study, the role of AtJUB1 overexpression in salinity was investigated in tomato plants. AtJUB1 overexpression resulted in higher proline levels and improved maintenance of water content and biomass in AtJUB1-overexpressing plants grown hydroponically under salinity compared with WT plants. Quinoa has recently gained much attention because of its high nutritional value and high tolerance to several stresses including drought and salinity. NAC TFs are hypothesized to play a major role in quinoa’s tolerance to abiotic stresses. In this study, the NAC TFs family were identified and investigated in the genome of quinoa. 107 NAC TF genes were identified and their transcriptional responses to different stresses including salt, drought and heat were investigated.

>Magister Scientiae - MSc / Salinity is one of the major limiting factors to crop production, which consequently contributes to the risk of reduced food security. Among other factors, food security depends on availability of sufficient and nutritious food for humans. Livestock such as cattle and sheep are fed with various plant-based feeds; with Medicago sativa (commonly known as alfalfa or lucerne) being a very important forage/feed crop, so much that it is regarded as the queen of forage crops. However, alfalfa is severely affected by high soil salinity and thus its growth and yield are drastically reduced in soils with high NaCl content. Among the various alfalfa genotypes/varieties examined in this study, Agsalfa was identified as salt tolerant because it performed better under salt treatment compared to Magna601.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Good quality water for agricultural use is rapidly becoming a luxury due to competition for this water among the municipal, industrial and agricultural sectors. This has often forced growers to use poor quality water for irrigation. Salinity is one of the main sources of poor water quality and high electrical conductivities (EC’s) due to salinity may become a problem. The aim of this study was to compare the response of South African spring wheat and South African spring barley at germination, seedling growth, vegetative growth, reproductive growth and maturity stage to salinity stress caused by irrigation with saline water. This study was conducted in the laboratory and under controlled glasshouse conditions at the University of Stellenbosch in the Western Cape Province of South Africa. Treatments in trial 1 (incubation trial) were made up of three wheat cultivars (SST 027, SST 056 and SST 087) and three barley cultivars (Nemesia, Erica and Hessekwa) exposed to five EC levels of NaCl solutions (4, 8, 12, 16 and 20 dS m-1) and a control (0 dS m-1) of distilled water, during the germination phase. In trial 2 (pot trial), wheat cultivar SST 027 and barley cultivar SVG 13 were also subjected to the above solutions, but plants were grown till the tillering stage. In trial 3 (pot trial) cultivars used in trial 2 were subjected to five nutrient solutions with EC levels of 1.6, 3, 6, 9 and 12 dS m-1 and allowed to grow till maturity (harvesting stage). Fully balanced nutrient solution with EC = 1.6 dS m-1 was used as a control and NaCl was added to the solutions to obtain the needed EC. In trial 1, final germination percentage (FGP), salt tolerance (ST) and germination rate (GR) were measured at 7 days after incubation. The study showed that when the EC level was increased, FGP, ST and GR of all wheat and barley cultivars tested were decreased. However, significant reduction was only observed at high EC levels with regard to FGP and ST. Wheat cultivars recorded faster GR compared to barley cultivars and tended to be less sensitive to salinity in the germination stage. Cultivars from the same species did not show significant differences. In trial 2, shoot length (SL), root length (RL), shoot fresh weight (SFW), root fresh weight (RFW), shoot dry weight (SDW) and root dry weight (RDW) were measured at 35 days after planting (DAP). In general, the study showed that salinity had a significant (P0.05) effect on seedling growth of all measured parameters of both wheat and barley. Mean values for most growth parameters were higher for barley cultivar SVG 13 as compared to wheat cultivar SST 027. However, little evidence was found to show that barley is more salt tolerant than wheat at the seedling stage. In trial 3, selected growth parameters were measured at tillering (28 DAP), booting (54 DAP), flowering (71 DAP) and maturity stage (150 DAP). The study showed that salinity had a significant (P0.05) effect on the vegetative growth, reproductive growth and grain yield of both wheat and barley. Although barley generally produced higher dry weights especially at the early growth stages no clear evidence was found that South African spring barley is more salt tolerant than South African spring wheat. / AFRIKAANSE OPSOMMING: Besproeiingswater met ‘n goeie kwaliteit vir landboukundige gebruik word vinning baie skaars weens kompetisie, a.g.v menslike en industriële gebruik. Produsente word dus dikwels gedwing om water met ‘n swak kwaliteit te gebruik vir besproeiing. ‘n Hoë sout inhoud (brakwater) soos gemeet deur ‘n hoë elektriese geleidingsvermoë (EC), mag dus ‘n problem wees. Die doel van hierdie studie was om te bepaal hoe Suid Afrikaanse lente koring en gars gedurende ontkieming asook saailing-, vegetatiewe-, reproduktiewe- en rypwordingstadiums reageer teenoor soutstremming wat veroorsaak is deur besproeiing met brakwater. Die studie is uitgevoer in laboratoriums en onder gekontrolleerde glashuistoestande by die Universiteit van Stellenbosch in die Weskaap Provinsie van Suid Afrika. Behandelings in die eerste proef (inkubasie studie) het bestaan uit drie koring kultivars (SST 027, SST 056 en SST 087) en drie gars kultivars (Nemesia, Erica en Hessekwa) wat tydens ontkieming benat is met vyf NaCl-oplossings met EC waardes van 4, 8, 12, 16 en 20 dS m-1 onderskeidelik, asook ‘n kontrole met gedistilleerde water (0 dS m-1). In die tweede proef is die koring kultivar, SST 027 en die gars kultivar SVG 13 in ‘n potproef ook aan bogenoemde oplossings blootgestel maar toegelaat om tot die stoelstadium te ontwikkel. In die derde proef is genoemde twee kultivars besproei met vyf voedingsoplossings met EC-waardes van 1.6, 3, 6, 9 en 12 dS m-1 en toegelaat om tot oesstadium te ontwikkel. ‘n Volledig gebalanseerde voedingsoplossing met EC = 1.6 dS m-1 is as kontrole gebruik en NaCl is by ander oplossings gevoeg om die verlangde EC te verkry. In die eerste proef waar die finale ontkiemingspersentasie (FOP), sout toleransie (ST) en ontkiemingstempo (OT) na 7 dae gemeet is, is gevind dat FOP, ST en OT van al die koring en gars kultivars wat getoets is, met toenemende EC gedaal het. Statisties betekenisvolle afnames in FOP en ST is egter slegs by hoë EC waardes waargeneem. Koring kultivars het vinniger ontkiem as gars kultivars en was geneig om meer tolerant teenooor sout stremming te wees vergeleke met gars. Verskille tussen kultivars van dieselfde spesie was egter weglaatbaar klein. In die tweede proef waar plante toegelaat is om te groei tot die stoelstadium (35 dae na plant) is al die gemete planteienskappe (stingel- en wortellengte, asook vars en droë massas van stingels en wortels) van beide gars kultivar, SVG 13 en koring kultivar, SST 027, betekenisvol verlaag deur ‘n toename in EC van die besproeiingswater. Hoewel gars ten opsigte van die meeste gemete eienskappe groter gemiddeldes as koring getoon het, is weinig bewys gevind wat daarop dui dat die getoetsde gars kultivar SVG 13 meer souttolerant is as die koring kultivar SST 027. In die derde proef waar dieselfde koring en gars kultivars vanaf plant tot oestyd besproei is met genoemde voedingsoplossings en metings tydens stoelstadium (28 dae na plant), stamverlenging (54 dae na plant), blomstadium (71 dae na plant) en oesrypstadium (150 dae na plant) gedoen is, is alle gemete vegetatiewe-, reproduktiewe- en opbrengskomponente van beide spesies verlaag deur die soutstremming. Hoewel gars ook in hierdie proef veral gedurende vroeë groeistadiums groter droë massas as koring geproduseer het, is geen konkrete bewyse gevind wat daarop dui dat die getoetsde Suid Afrikaanse lente gars kultivar SVG 13 meer sout tolerant is as die koring kultivar SST 027.

Submitted by (ana.araujo@ufrpe.br) on 2017-02-10T14:18:44Z No. of bitstreams: 1 Gabriela de Morais Guerra Ferraz.pdf: 1062151 bytes, checksum: b0123f5d7101341f981de975826dc25b (MD5) / Made available in DSpace on 2017-02-10T14:18:44Z (GMT). No. of bitstreams: 1 Gabriela de Morais Guerra Ferraz.pdf: 1062151 bytes, checksum: b0123f5d7101341f981de975826dc25b (MD5) Previous issue date: 2008-02-29 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The Northeast of Brazil, major national producer of bananas, presents as a major limiting factor the stretch of saline soil. The urgency in the development of tolerant cultivars to salinity has led to breeding programs with the aimed to differ the bananas cultivars in diploid genotypes tolerant and sensitive, to be considered viable genetic material for pollination of triploid and tetraploid cultivars. Generally, the present study aimed to characterize diploid genotypes belonging to the AA banana genomic group on salinity and identify genes differentially expressed in contrasting genotypes. At first, this research assessed the growth and accumulation of inorganic ions in 19 diploid genotypes (AA) of bananas subjected to salt stress. The genotypes were grown in a greenhouse and submitted to irrigation with no saline water (0 mM NaCl) or with saline water (100 mM NaCl) for a period of 21 days, when the experiment was collected. To the physiological evaluation, were considered the parameters of growth:leaf area, height, number of leaves, diameter of the pseudostem, weight of the tax burden of fresh and dry, while the chemical assessment observed the concentration of sodium ions, potassium, chloride, magnesium and calcium in limbo leaf, and root pseudostem / subroot. The addition of NaCl to the cultivar solution has, in general, reduced the growth expressed by height, formation of new leaves, leaf area, diameter of the pseudostem and production of fresh and dry materials. This reduction in growth probably due to factors such as: the toxic effect of ions that have been absorbed, the low osmotic and water potential of the cells as well as the use of metabolic energy in the process of osmotic adjustment. In assessing chemical factors, it was possible to observe that the ions concentration has been preferentially presented in root tissue, showing that it is a culture moderately tolerant to salinity.The sodium and chlorine ions increased significantly with the salt increase in differentparts of the plant, while potassium suffered reduction in the leaf lamina and the pseudostem probably because it is associated to the competition with the sodium ion leading to the conclusion that the differential accumulation of ions potentially toxic (sodium and chlorine) and the maintenance of potassium, contribute to the tolerance to salinity in banana. From the physiological analysis and by means of the toxicity symptoms caused by NaCl, it was possible to observe that the effects were less intense in Birmania and Khai Nai On genotypes, than in Sowmuk, its indicates the possibility of use of this plants in programmes for cultivars improvement as tolerant and sensitive, respectively. Seven genotypes were selected for characterization by means of molecular markers RAPD, with the aim to link the physiological responses to salt stress with the formation of groups. We tested 16 random primers. The resultsshow a broad molecular genetic variability among seven genotypes studied. The formation of groups, in part is related to the data obtained in the physiological assessment, keeping in the same group the Birmania and Khai Nai On genotypes.These genotypes that showed higher tolerance to salt stress, when compared to the more salt-sensitive genotype (Showmuk), became distant genetically, so, it can be noticed the possibility of use of this molecular marker in the study of genetic diversity for this species. For the genome functional study, or transcriptoma, this study aimed the detection of possible changes in the pattern of genes expressed in the three diploid genotypes (AA) of banana, Khai Nai On, Burma and Sowmuk with contrasting results when in the absence and presence of high salt concentrations. The Differential Display PCR - ddPCR technique was used to identify and compareregions of bands from fragments of cDNA on agarose gel. A total of 43 fragments of differentially expressed cDNA was generated from the combination of four primers anchors and six random primers. Among the transcripts, 30 were once expressed by the genotype Burma and Kha Nai On, and 13 only by Sowmuk genotype. Theregions of bands with greater consistency of formation, is between 4000 bp and 150 bp. By the results of this research, it was possible to identify some fragments potentially involved to the condition of salinity in banana. The isolation, purification and sequencing of these - Expressed sequence tags - ESTs can assist in the development of new varieties of banana, more adapted to salt stress, in addition to enriching the database of public functional sequences of genomes banks. / O Nordeste do Brasil, maior produtor nacional de banana, apresenta como fator limitante a grande extensão de solos salinos. A urgência no desenvolvimento de cultivares tolerantes a salinidade tem levado programas de melhoramento genético da cultura a classificar os genótipos diplóides de bananeira em tolerantes e sensíveis, por serem considerados materiais genéticos viáveis para polinização de cultivares triplóides e tetraplóides. De modo geral, o presente trabalho buscou caracterizar genótipos diplóides pertencentes ao grupo genômico AA de bananeira quanto a salinidade além de identificar genes diferencialmente expressos nos genótipos contrastantes. Na primeira fase desta pesquisa, foi avaliado o crescimento vegetativo e o acúmulo de íons inorgânicos em 19 genótipos diplóides (AA) de bananeiras submetidas a estresse salino. Os genótipos foram cultivados em casa de vegetação e submetidos à irrigação com água não salina (0 mM de NaCl) ou águasalina (100 mM de NaCl) durante um período de 21 dias, quando foi coletado o experimento. Para a avaliação fisiológica, foram considerados os parâmetros de crescimento: área foliar, altura, nº de folhas, diâmetro do pseudocaule, peso da matéria fresca e peso da matéria seca; enquanto que a avaliação química observou a concentração dos íons sódio, potássio, cloro, magnésio e cálcio no limbo foliar, pseudocaule e raiz/rizoma. A adição de NaCl à solução de cultivo, provocou, de modo geral, redução no crescimento expresso pela altura, formação de novas folhas, área foliar, diâmetro do pseudocaule e produção de matéria fresca e seca, provavelmente devido a fatores como: o efeito tóxico dos íons que foram absorvidos; o baixo potencial osmótico e hídrico das células; bem como a utilização de energia metabólica no processo de ajustamento osmótico. Na avaliação química, foi possívelobservar que a concentração dos íons foi preferencialmente no tecido radicular, reafirmando tratar-se de uma cultura moderadamente tolerante a salinidade. Os íonssódio e cloro aumentaram significativamente frente ao incremento salino nas diferentes partes da planta, enquanto o potássio sofreu redução no limbo foliar e no pseudocaule, possivelmente por estar associado a competição com o íon sódio levando a conclusão de que o acúmulo diferencial de íons potencialmente tóxicos (sódio e cloro) e a manutenção do potássio, contribuem para a tolerância à salinidade em bananeira. A partir da análise fisiológica e por meio da sintomatologia de toxidez provocada pelo NaCl, foi possível observar que os efeitos foram menos intensos nos genótipos Birmânia e Khai Nai On, do que no Sowmuk, indicando possíveis plantas a serem utilizadas nos programas de melhoramento da cultura como tolerantes e sensível, respectivamente. Sete genótipos foram selecionados para caracterização por meio de marcadores moleculares RAPD, buscando-se relacionar as respostas fisiológicas ao estresse salino com a formação de grupos.Foram testados 16 primers randômicos. Os resultados moleculares mostram uma ampla variabilidade genética entre os sete genótipos estudados. A formação dos agrupamentos, em parte correspondeu aos dados obtidos na avaliação fisiológica, mantendo em um mesmo grupo os genótipos Birmânia e Khai Nai On. Estes genótipos que apresentaram maior tolerância ao estresse salino, quando comparados com a mais sensível ao sal (Showmuk), mostraram-se distantes geneticamente, o que vem a demonstrar a possibilidade de utilização deste marcador molecular no estudo da diversidade genética para esta espécie. Para o estudo do genoma funcional, ou transcriptoma, o presente trabalho objetivou a detecção das possíveis alterações no padrão de genes expressos nos três genótipos diplóides (AA) de bananeira, Khai Nai On, Birmânia e Sowmuk, com respostascontrastantes quando na ausência e presença de alta concentração salina. A técnica de Differential Display PCR – ddPCR foi utilizada para identificar e comparar regiões de bandas de fragmentos de cDNA em gel de agarose. Um total de 43 fragmentosde cDNA diferencialmente expressos foram gerados a partir da combinação de quatro primers âncoras e seis primers aleatórios. Dentre os transcritos, 30 foram expressos unicamente pelos genótipos Birmânia e Kha Nai On, e 13 apenas pelo genótipo Sowmuk. As regiões de bandas com maior consistência de formação, encontraram-se entre 4000 pb e 150 pb. Pelos resultados deste trabalho, foi possível identificar alguns fragmentos potencialmente envolvidos em respostas à condição de salinidade em bananeira. O isolamento, purificação e sequenciamento destes –Expressed sequence tags - ESTs poderá auxiliar no desenvolvimento de novos cultivares de bananeira, mais adaptados ao estresse salino, além de enriquecer a base de dados de bancos públicos de seqüências de genomas funcionais.