ABSTRACT In disease assessment, the use of diagrammatic scales provides a standard reference point for comparison. There is still no precise and accurate scale for the evaluation of sporulation intensity of downy mildew in lettuce seedlings. The objective of this study was to propose a diagrammatic scale for the evaluation of downy mildew severity in lettuce seedlings. Thirty lettuce seedlings with different sporulation intensities were used to develop the proposed diagrammatic scale. Solaris lettuce cultivar was sown, and fifteen days after sowing, inoculations occurred using distilled water, the pathogen sporangia, and Tween 20. The monitoring of disease development was performed daily.When the first sporulation appeared on the cotyledonaryleaves,the proposed scale was verified to meet the minimum and maximum levels of disease severity. Two evaluators verified the accuracy, precision and performed the estimation of the sporulation and reproducibility using a scale. The images obtained are important in the standardization of a scale to identify resistant, tolerant and susceptible plants to downy mildew. Furthermore, it allows validating a diagrammatic scale of sporulation intensity of B. lactucae in lettuce seedlings. Thus, it is the diagrammatic scale developed in the work will guide future research to accelerate the detection of mildew severity in lettuce seedlings.

ABSTRACT. Brazilian consumers are increasingly seeking unique vegetable products, such as mini lettuces. However, their production is hampered by a wide variety of pathogens, including Pectobacterium carotovorum subsp. carotovorum, which causes soft rot in lettuce. In this study, we aimed to select biofortified mini lettuce genotypes with good agronomic traits and resistance to P. carotovorum. A randomized block design consisting of 12 treatments, conducted in a field and greenhouse (Federal University of Uberlândia [UFU]), was used to select biofortified mini lettuce with good agronomic traits: SPAD index, stem and plant diameter, stem length, plant height, number of leaves, fresh weight, and bolt resistance. A completely randomized design consisting of 13 treatments was used for resistance or susceptibility testing. The bacterial suspension was inoculated and the following were assessed: disease severity, 16 days after inoculation; area under the disease progress curve, calculated separately at 4, 8, 12, and 16 days after inoculation as well as the sum of data calculated on all the assessment days; and the disease resistance class. The genotypes UFU 215#1 and UFU 215#2 had significantly high carotenoid concentrations. The genotypes UFU 66#4, UFU 215#1, and UFU 215#7 showed high bolt resistance. All genotypes were classified as resistant or moderately resistant to the P. carotovorum isolate, UFU A7.

RESUMO O uso de cultivares de alface resistentes é uma das formas de controle do míldio. Objetivou-se avaliar as resistências vertical e horizontal de progênies F5:6 de alface biofortificada com carotenoides aos fenótipos de virulência de Bremia lactucae: 63/63/51/00, 63/31/19/00 e 63/63/19/00. O delineamento experimental utilizado foi inteiramente casualizado, em parcelas subdivididas no tempo. Nas parcelas utilizaram-se os 12 genótipos de alface e nas subparcelas utilizou-se o tempo, sendo este de 7 a 18 dias após a inoculação. Para cada fenótipo de virulência de Bremia lactucae fez-se um experimento separado, com três repetições. Para selecionar genótipos resistentes procedeu-se a inoculação, com mistura de água destilada, esporângios retirados de tecidos infectados do hospedeiro e Tween 20. A avaliação dos genótipos iniciou-se quando houve o aparecimento da esporulação nas folhas cotiledonares da cultivar suscetível Solaris, verificando-se a proporção de plantas necrosadas e com esporulação. Houve interação entre genótipos e tempos para todos os fenótipos de virulência avaliados. Os genótipos de alface biofortificada UFU-189#2, UFU-206#1, UFU-215#3 e UFU-215#14 apresentam resistência vertical aos fenótipos de virulência 63/63/51/00, 63/31/19/00 e 63/63/19/00 de B. lactucae. Níveis de resistência horizontal foram observadas no genótipo UFU- 206#1 para os fenótipos de virulência 63/63/51/00 e 63/31/19/00; no genótipo UFU-66#7 para o fenótipo de virulência 63/31/19/00 e no genótipo UFU-215#10 para o fenótipo de virulência 63/63/19/00 de Bremia lactucae.

ABSTRACT The use of resistant cultivars is one of the strategies for downy mildew management. The objective of this study was to evaluate the vertical and horizontal resistance of F5:6 progenies of carotenoidbiofortified lettuce to virulence phenotypes of Bremia lactucae 63/63/51/00, 63/31/19/00 and 63/63/19/00. The experimental design was completely randomized and subdivided into plots that were evaluated over time. In the plots, 12 genotypes of lettuce were used, and the subplots were monitored over time (7th to the 18th day after inoculation). For each virulence phenotypes of Bremia lactucae, a separate experiment was performed with three replicates. To select resistant genotypes, plants were inoculated with distilled water, sporangia removed from infected tissues and Tween 20. The genotypes were evaluated when sporulation appeared on cotyledonary leaves of the susceptible cultivar Solaris, verifying the proportion of necrotic and sporulated plants. There was a correlation between genotypes and times for all virulence phenotypes evaluated. Genotypes UFU-189#2, UFU-206#1, UFU-215#3 and UFU-215#14 showed vertical resistance to virulence phenotypes 63/63/51/00, 63/31/19/00, and 63/63/19/00 of B. lactucae. Horizontal resistance levels were observed in genotype UFU 206#1 for virulence phenotypes 63/63/51/00 and 63/31/19/00; in genotype UFU-66#7 for virulent phenotype 63/31/19/00; and in genotype UFU-215#10 for virulence phenotype 63/63/19/00.

RESUMO O entendimento da genética e das interações gênicas envolvidas na expressão de determinadas características se torna um fator determinante para a melhor exploração seu uso. Este desconhecimento das bases genéticas envolvidas impacta diretamente no desenvolvimento de programas de melhoramento que aliem uma ou mais características desejáveis em uma única cultivar. O objetivo do presente estudo foi estimar os parâmetros genéticos envolvidos na expressão dos pigmentos e características agronômicas em alface. Foram avaliados parentais P1 (verde) e P2 (roxo), as gerações segregantes F1 e F2, e os backcross Bc1 e Bc2 originados do cruzamento UFU-Crespa199#1#1 x UFU-Albina#2. As avaliações foram feitas para teor de clorofila, teor de antocianina, número de folhas e diâmetro de planta. O estudo foi realizado pelo teste de gerações e as estimativas obtidas por meio das médias e variâncias. Foi verificado indicativo de herança poligênica ou oligogênica para as características número de folhas, diâmetro de plantas e teor de antocianina. Com exceção do teor de antocianina tanto o modelo completo quanto o aditivo-dominante explicaram satisfatoriamente o comportamento das variáveis.

ABSTRACT Understanding genetics and the gene interactions involved in the expression of certain characteristics becomes a determining factor for better exploration of its use. The development of breeding programs that combine one or more desirable trait into a single cultivar is directly impacted by this lack of knowledge of the genetic bases involved. The objective of the present study was to estimate the genetic parameters involved in pigment expression and agronomic characteristics in lettuce. Parental evaluations of lettuce, P1 (green) and P2 (purple) parental generations, the segregating generations F1 and F2, and the backcrosses Bc1 and Bc2 originating from the UFU-Crespa199#1#1 x UFU-Albina#2 crossing were evaluated. The chlorophyll and anthocyanin contents, number of leaves and plant diameter were evaluated. The study was conducted by testing all generations and the estimates obtained by averages and variances. Indications of polygenic or oligogenic inheritance were verified by the characteristic number of leaves, plant diameter, and anthocyanin content. The complete and additive-dominant models satisfactorily explained the performance of the variables, except the anthocyanin content.

RESUMO O cultivo de Piper aduncum para a extração de óleo essencial é crescente, mas carece de informações básicas de manejo e cultivo, que possibilitem produtividade e qualidade do produto para atender a demanda de mercado. Objetivou-se avaliar a relação entre a produção de óleos essenciais em P. aduncum e tensões de água no solo (20 kPa, 40 kPa, 60 kPa, 100 kPa e sem irrigação). Foram avaliados o número de idioblastos e a produção de óleo essencial em folhas de plantas cultivadas. A variação na tensão de água no solo altera a quantidade de idioblastos nas folhas de P. aduncum, com reflexo na produção de óleo essencial. A tensão de água no solo de 20-60 kPa é suficiente para a planta expressar o maior número de idioblastos e maior produção de óleo essencial. A espécie se adapta a diferentes condições de disponibilidade de água no solo. Em condições de estresse, devido ao déficit ou excesso de água, a produção de óleo essencial é reduzida.

ABSTRACT The growing of Piper aduncum for essential oil extraction has increased, but there is a lack of basic information about its management and cultivation, which allows the productivity and quality of the oil, in order to attend the market demands. This study aimed to evaluate the relation between the production of essential oils from P. aduncum and soil water pressure heads (20 kPa, 40 kPa, 60 kPa, 100 kPa and non-irrigated). The assessment comprised the quantification of idioblasts and the production of essential oil extracted from leaves of cultivated plants. The variation in the soil water pressure head alters the amount of idioblasts in P. aduncum leaves, with impacts on the essential oil production. A soil water pressure head range of 20-60 kPa is sufficient for this species to express the highest amount of idioblasts and the highest level of essential oil production. The species adapts itself to different water availability conditions in the soil. Under stress conditions, due to water deficit or excess, the production of essential oil is reduced.