Aplicación de redes neuronales convolucionales para la detección del tizón tardío Phytophthora infestans en papa Solanum tuberosum / Application of convolutional neural networks for detection of the late blight Phytophthora infestans in potato Solanum tuberosum

RESUMEN La presencia del tizón tardío o gota en el cultivo de papa afecta directamente el crecimiento de la planta y el desarrollo del tubérculo, por ello, es importante la detección temprana de la enfermedad. Actualmente, la aplicación de redes neuronales convolucionales es una oportunidad orientada a la identificación de patrones en la agricultura de precisión, incluyendo el estudio del tizón tardío, en el cultivo de papa. Este estudio describe un modelo de aprendizaje profundo capaz de reconocer el tizón tardío en el cultivo de papa, por medio de la clasificación de imágenes de las hojas. Se utilizó, en la aplicación de este modelo, el conjunto de datos aumentado de PlantVillage, para entrenamiento. El modelo propuesto ha sido evaluado a partir de métricas de rendimiento, como precisión, sensibilidad, puntaje F1 y exactitud. Para verificar la efectividad del modelo en la identificación y la clasificación del tizón tardío y comparado en rendimiento con arquitecturas. como AlexNet, ZFNet, VGG16 y VGG19. Los resultados experimentales obtenidos con el conjunto de datos seleccionado mostraron que el modelo propuesto alcanza una exactitud del 90 % y un puntaje F1, del 91 %. Por lo anterior, se concluye que el modelo propuesto es una herramienta útil para los agricultores en la identificación del tizón tardío y escalable a plataformas móviles, por la cantidad de parámetros que lo comprenden.

ABSTRACT The presence of late blight in potato crops directly affects plant growth and tuber development; therefore, early detection of the disease is important. Currently, the application of convolutional neural networks is an opportunity oriented to the identification of patterns in precision agriculture, including the study of late blight in potato crops. This study describes a deep learning model capable of recognizing late blight in potato crops by means of leaf image classification. The PlantVillage augmented dataset was used in the application of this model for training. The proposed model has been evaluated from performance metrics such as precision, sensitivity, F1 score, and accuracy; to verify the effectiveness of the model in the identification and classification of late blight and compared in performance with architectures such as AlexNet, ZFNet, VGG16, and VGG19. The experimental results obtained with the selected data set showed that the proposed model achieves an accuracy of 90 % and an F1 score of 91 %. Therefore, it is concluded that the proposed model is a useful tool for farmers in the identification of late blight and scalable to mobile platforms due to the number of parameters that comprise it.

Media preferences, micro-morphometric analysis, and cardinal growth temperature determination for Phytophthora infestans sensu lato isolated from different hosts in Colombia / Preferências de mídia, análise micro-morfométricos e determinação da temperature cardeal de crescimento para Phytophthora infestans sensu lato isolada de diferentes hospedeiros na Colômbia

Abstract During the last years Phytophthora infestans sensu lato (Mont. De Bary) has caused epidemics in Colombia in Andean fruit crops such as Solanum quitoense and Solanum betaceum. Establishment of new or modified experimental procedures to study this pathogen is a mandatory subject for scientists. Twelve isolates of Phytophthora spp. obtained from six different Solanum hosts in Colombia were used to evaluate the effect of five different solid media for growth and ability to produce sporangia and liberate zoospores. Determination of the best media culture and optimal growth temperature were necessary to perform measurements and correlate the provenance of isolates with phenotypic traits. Modifications were made to use ingredients available in local markets on the following media: lime bean agar (LBA), Tree tomato or tree tomato agar (TA), carrot agar (AZ), Rye A modified agar and 32% non-clarified V8 agar. Cardinal temperature determination was performed at 10, 15, 20, and 25 °C. Morphometric traits were measured once the optimal media culture and temperature were defined. Correlation analysis showed that there is a relationship between the host and isolate's preferences for media culture and optimal growth temperature. In addition, the production of characteristic sporangia, sporangiophore and mycelia was related with the media type used and host from which the isolate was collected. In this work useful information was provided to make studies about the biology and development of isolates gathered from cultivated and wild non-traditional hosts.

Resumo Durante os últimos anos Phytophthora infestans sensu lato causou epidemias na Colômbia em lavouras de frutos andinos, como Solanum quitoense e Solanum betaceum. Estabelecimento de procedimentos experimentais novos ou modificados para estudar este patógeno é um assunto obrigatório para os cientistas. Doze isolados de Phytophthora spp. obtidos de seis diferentes hosts Solanum na Colômbia foram usados para avaliar o efeito de cinco diferentes mídias sólidas para o crescimento e a capacidade de produzir esporângios e libertar zoósporos. Determinação da melhor cultura de mídia e temperatura de crescimento ideal foram necessárias para realizar medições e correlacionar a proveniência de isolados com traços fenotípica. Foram feitas modificações para usar os ingredientes disponíveis nos mercados locais nos seguintes meios: ágar do feijão de cal (LBA), tomate da árvore ou ágar do tomate da árvore (TA), ágar da cenoura (AZ), centeio um ágar modificado e 32% de ágar-V8 não-esclarecido. A determinação da temperatura Cardeal foi realizada em 10, 15, 20 e 25 °C. Traços morfométricos foram medidos uma vez que a cultura de mídia ideal e temperatura foram definidos. Análise de correlação mostrou que há uma relação entre o hospedeiro e isolar as preferências para a cultura de mídia e temperatura de crescimento ideal. Além disso, a produção de esporângios característica, esporangióforo e mycelia foi relacionada com o tipo de mídia utilizado e hospedeiros a partir do qual o isolado foi coletado. Neste trabalho foram fornecidas informações úteis para fazer estudos sobre a biologia e o desenvolvimento de isolados recolhidos de hospedeiros não-tradicionais cultivados e selvagens.

Characterization of glycolipid biosurfactant from Pseudomonas aeruginosa PA 1 and its efficacy against Phytophtora infestans

Aim: The aim of the present study was to identify biosurfactant produced by Pseudomonas aeruginosa and to determine the effectiveness of biosurfactants (rhamnolipid) against P. infestans causing late blight of potato. Methodology: Pseudomonas aeruginosa strains were isolated from soil samples and the potential strain PA 1, selected because of its antagonistic ability, was used to optimize anti-metabolite production and its characterization using HPLC-Mass spectrometry. Rhamnolipid based formulation was developed and its efficacy was tested against late blight disease. Results: The results revealed that four rhamnolipids congeners were identified, among them three were mono-rhamno-di-lipidic congeners and one was di-rhamno-di-lipdic congeners, abundantly present in the crude biosurfactant obtained from P. aeruginosa PA1. The mass spectra of mono-rhamno-di-lipidic Rha-C12-C14 peak value (m/z 584), Rha-C12.1-C10.CH3 peak value (m/z 545), Rha-C12-C-12-CH3 peak value (m/z 575) and di-rhamno-di-lipidic. Rha-Rha-C10-C10 peak value (m/z 651) were also detected. Rhamnolipid-based formulation was developed and evaluated at different concentration ranging from 0.012 and 0.3% in detached leaf test. Significant reduction in lesion area was recorded at 0.2% concentration (lesion area 0.06 cm2 as against 9.8 cm2 on 5th day of inoculation). Interpretation: Microbial produced rhamnolipid based formulation at 0.2% concentration was found effective against late blight of potato in detached leaf test. Further, it could be used in field study as green chemical which would help in replacing application of chemicals in agriculture.

Media preferences, micro-morphometric analysis, and cardinal growth temperature determination for Phytophthora infestans sensu lato isolated from different hosts in Colombia

Abstract During the last years Phytophthora infestans sensu lato (Mont. De Bary) has caused epidemics in Colombia in Andean fruit crops such as Solanum quitoense and Solanum betaceum. Establishment of new or modified experimental procedures to study this pathogen is a mandatory subject for scientists. Twelve isolates of Phytophthora spp. obtained from six different Solanum hosts in Colombia were used to evaluate the effect of five different solid media for growth and ability to produce sporangia and liberate zoospores. Determination of the best media culture and optimal growth temperature were necessary to perform measurements and correlate the provenance of isolates with phenotypic traits. Modifications were made to use ingredients available in local markets on the following media: lime bean agar (LBA), Tree tomato or tree tomato agar (TA), carrot agar (AZ), Rye A modified agar and 32% non-clarified V8 agar. Cardinal temperature determination was performed at 10, 15, 20, and 25 °C. Morphometric traits were measured once the optimal media culture and temperature were defined. Correlation analysis showed that there is a relationship between the host and isolates preferences for media culture and optimal growth temperature. In addition, the production of characteristic sporangia, sporangiophore and mycelia was related with the media type used and host from which the isolate was collected. In this work useful information was provided to make studies about the biology and development of isolates gathered from cultivated and wild non-traditional hosts.

Resumo Durante os últimos anos Phytophthora infestans sensu lato causou epidemias na Colômbia em lavouras de frutos andinos, como Solanum quitoense e Solanum betaceum. Estabelecimento de procedimentos experimentais novos ou modificados para estudar este patógeno é um assunto obrigatório para os cientistas. Doze isolados de Phytophthora spp. obtidos de seis diferentes hosts Solanum na Colômbia foram usados para avaliar o efeito de cinco diferentes mídias sólidas para o crescimento e a capacidade de produzir esporângios e libertar zoósporos. Determinação da melhor cultura de mídia e temperatura de crescimento ideal foram necessárias para realizar medições e correlacionar a proveniência de isolados com traços fenotípica. Foram feitas modificações para usar os ingredientes disponíveis nos mercados locais nos seguintes meios: ágar do feijão de cal (LBA), tomate da árvore ou ágar do tomate da árvore (TA), ágar da cenoura (AZ), centeio um ágar modificado e 32% de ágar-V8 não-esclarecido. A determinação da temperatura Cardeal foi realizada em 10, 15, 20 e 25 °C. Traços morfométricos foram medidos uma vez que a cultura de mídia ideal e temperatura foram definidos. Análise de correlação mostrou que há uma relação entre o hospedeiro e isolar as preferências para a cultura de mídia e temperatura de crescimento ideal. Além disso, a produção de esporângios característica, esporangióforo e mycelia foi relacionada com o tipo de mídia utilizado e hospedeiros a partir do qual o isolado foi coletado. Neste trabalho foram fornecidas informações úteis para fazer estudos sobre a biologia e o desenvolvimento de isolados recolhidos de hospedeiros não-tradicionais cultivados e selvagens.

Expresión de efectores RXLR en el linaje clonal EC-1 de Phytophthora infestans en Perú / Expression of RXLR effectors in the EC-1 clonal lineage of Phytophthora infestans in Peru

La papa (Solanum tuberosum L.) es en nuestros días uno de los cultivos alimenticios más importantes. Esta es propensa a la enfermedad de Tizón Tardío, causada por el oomiceto patógeno Phytophthora infestans, el cual secreta cientos de efectores que actúan como factores de virulencia. Poco se conoce sobre la diversidad de genes de virulencia de las cepas pertenecientes al linaje de reproducción clonal EC-1. En el presente estudio, mediante el secuenciamiento del transcriptoma de la interacción de la papa y P. infestans durante los primeros días después de la infección en las hojas de papa, se identificó la expresión diferencial de genes efectores tipo RXLR en dos cepas de P. infestans EC-1, siendo confirmados por qRT-PCR. Estas cepas, aisladas de papas cultivadas en el centro de los Andes peruanos, tienen diferentes patrones de virulencia. Los genes efectores, fueron silenciados en una cepa, para Avr-vnt1 en POX109 y para el homólogo Avh9.1 en POX067, pero expresados en la otra. Los resultados de transcriptoma fueron comparados con tres cepas adicionales del linaje EC-1. La información del repertorio de los efectores del patógeno y su expresión podrían ser informativos para el mejoramiento genético de la resistencia. El descubrimiento de efectores silenciados en las poblaciones del patógeno pueden guiar al uso de genes R específicos en los programas de mejoramiento genético. Por ejemplo, en el contexto de los Andes, donde el linaje clonal EC-1 predomina, el gen Rpi-vnt1 podría no ser recomendado.

Potato (Solanum tuberosum L.) is nowadays one of the most important food crops. It is prone to the disease known Late blight caused by the oomycete pathogen Phytophthora infestans, which secrete a hundreds of effectors that act as virulence factors. Little is known of the diversity of virulence genes of the strains that belong to a clonally reproducing lineage EC-1. In this paper, through the transcriptome sequencing of potato and P. infestans interaction, we identified differentially expressed RXLR type effector genes in two P. infestans isolates EC-1, being confirmed by qRT-PCR. The isolates, originate from cultivated potato in the central Peruvian Andes, have different virulence patterns. Effector genes, were silenced in one isolate, such as Avr-vnt1 in POX 109 and for Avh9.1 homolog in POX 067, but expressed in the other. The transcriptomics results were compared with three additional isolates from the EC-1 lineage. The information on the pathogen effector repertoire and its expression should be informative for resistance breeding. Discovery of silenced effectors in the pathogen populations can guide the use of specific R genes in the breeding programs. For example in the Andean setting where EC-1 lineage dominates the Rpi-vnt1 would not be recommended.

Asociaciones de marcadores moleculares con la resistencia a enfermedades, caracteres morfológicos y agronómicos en familias diploides de papa (Solanum tuberosum L.) / Associations of molecular markers with diseases resistance, morphological and agronomic characters in potato diploid families (Solanum tuberosum L.)

Quince familias de papa (824 genotipos) provenientes de cruzas inter-específicas entre especies de Solanum stenotomum, S. goniocalyx y S. phureja fueron genotipadas, con el objetivo de asociar seis marcadores moleculares (GP94, HC, Nl25, Gro 1-4, RYSC3 y CP60) con genes mayores de resistencia para tizón tardío (Phytophthora infestans), verruga (Synchytrium endobioticum), nematodo - quiste (Globodera pallida y G. rostochiensis) y virus PVY y PVX. Los resultados mostraron que cinco de los marcadores aplicados fueron polimórficos y amplificaron en más del 80% de las familias. El marcador RYSC3 que co-localiza con el gen Ry adg no amplificó en ninguna de las familias evaluadas. La familia 8 amplificó la banda para tres marcadores (CP60, GP94 y NL25) en la totalidad de sus clones. La prueba de χ² se utilizó para determinar el ajuste de las proporciones de segregación de cada familia para cada marcador y genotipar los progenitores. Nueve caracteres agronómicos y morfológicos fueron evaluados en la cosecha. Mediante agrupamiento cluster fueron seleccionados 107 clones con resistencia a PVX, P. infestans, G. rostochiensis y S. endobioticum, alto rendimiento y volumen de tubérculos, elevado número de tubérculos y ojos superficiales. Sobre la base de estos resultados, aspectos prácticos para la aplicación eficiente de la selección asistida por marcadores moleculares son discutidos en este artículo.

Fefteen families of potato (824 genotypes) originated from inter-specific crosses among Solanum stenotomum, S. goniocalyx and S. phureja were genotyped in order to associate six molecular markers (GP94, HC, Nl25, Gro 1-4, RYSC3 y CP60). These molecular markers are linked to major genes for resistance to late blight (Phytophthora infestans), wart (Synchytrium endobioticum), root cyst nematode (Globodera pallida and G. rostochiensis) and viruses PVY and PVX. Results showed that five of six molecular markers were polymorphic and primers amplified in more than 80 % of the families. Molecular marker RYSC3 that is linked to Rya dg gene did not amplify in any family. All individuals in Family 8 scored positive for three markers (CP60, GP94, and NL25). χ² test was used to determine the significance of the segregation ratios of each marker in every single family; so to the possible genotype of its parents was inferred. Nine morphological and agronomical characters were assessed during the harvest. Cluster analysis classified and selected 107 genotypes by putative resistance to PVX, P. infestans, G. rostochiensis and S. endobioticum, high yield, tuber volume and tuber number and shallow eyes. According to our results, practical aspects of efficient use of marker assisted selection in potato are discussed in this paper.

Sequence analysis and expression patterns of histone H2A variants in Phytophthora infestans / 生物工程学报

In eukaryotic cells, DNA is packaged inside the nucleus together with histones to form nucleosomes. Each histone molecule contains two of each core histone subunits H2A, H2B, H3 and H4. Among core histones, the H2A family is of great interest due to the high diversity of specialized variants. These variants have shown important role in critical cellular processes. Epigenetic mechanism in oomycetes is barely known. Phytophthora infestans is a severe pathogen and a model species in oomycetes. In this study, we studied the sequence and expression pattern of H2A variants of P. infestans through genome search, sequences alignment, phylogenetic analysis and realtime qPCR detection. P. infestans contains conserved genes encoding histone variants H2A.X.1, H2A.X.2 and H2A.Z, and these genes have specific expression patterns during development and infection stages. Our datasets provide useful inputs to help explore the epigenetic mechanisms of oomycetes.

Phytophthora infestans POPULATION STRUCTURE: A WORLDWIDE SCALE / Estructura poblacional de Phytophthora infestans: una escala global

Phytophthora infestans, the causal agent of late blight disease in potato and other members of the Solanaceae family, is responsible for causing the Irish potato famine and, even today, it causes enormous economic losses all over the world. For the establishment of an adequate pest management strategy, the determination of the pathogen's population structure is required. To characterize P. infestans populations worldwide two allozymes, Gpi (Glucose-6-phospate isomerase) and Pep ( Pep tidase), the RG57 DNA RFLP fingerprinting probe, as well as resistance to the fungicide metalaxyl and mating type, have been used as markers. P. infestans populations in Mexico have been one of the main focuses of research in the population biology of this pathogen because this country has been considered as one of the possible centers of origin of this oomycete. In this review we present the population structure of P. infestans in Mexico, Europe, Africa, Asia, North America, and South America, expanding it on the present situation of P. infestans in Colombia. Finally, we will discuss different lines of research that are being carried out today with respect to P. infestans in Colombia, which have shown the importance of continuing the study of this devastating plant pathogen in our country.

Phytophthora infestans, el agente causal del tizón tardío de la papa y otros miembros de la familia de las Solanáceas, es el responsable de la gran hambruna irlandesa y aún hoy sigue causando grandes pérdidas económicas alrededor del planeta. Para establecer estrategias de control adecuadas contra este patógeno se requiere comprender la estructura poblacional del mismo. Mundialmente se han utilizado como marcadores las aloenzimas, Gpi (Glucosa-6-fosfato isomerasa) y Pep (Peptidasa) y la sonda de fingerprinting de RFLP (Polimorfismos de la Longitud de los Fragmentos de Restricción), RG57. De igual forma, la resistencia al fungicida metalaxyl y el tipo de apareamiento, han sido empleados para caracterizar las poblaciones de P. infestans. Las poblaciones de P. infestans en México han sido uno de los focos principales de investigación en la biología poblacional de este patógeno debido a que este país ha sido considerado como uno de los posibles centros de origen de este oomiceto. En esta revisión se presentará la estructura poblacional de P. infestans en México, Europa, África, Asia, Norte América y Sur América, profundizando en la situación actual de P. infestans en Colombia. Finalmente, se discutirá las diferentes líneas de investigación que se llevan a cabo hoy respecto a P. infestans en Colombia, las cuales han mostrado la importancia de continuar con el estudio de este devastador patógeno de plantas en nuestro país.

Evaluación de marcadores moleculares asociados con resistencia a gota (Phytophthora infestans L) en papas diploides y tetraploides / Evaluation of molecular markers associated with resistance to late blight (Phytophthora infestans L) in diploid and tetraploid potatoes

La papa, cultivo de importancia a nivel mundial es gravemente afectado por gota, enfermedad ocasionada por el oomycete Phytophthora infestans. Actualmente la forma más efectiva para combatir la enfermedad es mediante el desarrollo de cultivares resistentes al patógeno. Para esto, una estrategia es identificar genes que confieran resistencia al patógeno, para lo cual se buscan marcadores asociados con el carácter de resistencia. En este estudio se evaluaron marcadores moleculares tipo SCAR (Sequence Characterized Amplified Region): CosA, GP179, BA47f2 y Prp1 asociados con resistencia a P. infestans y el gen de resistencia R1, en 22 cultivares tetraploides pertenecientes a la subespecie andigena y cinco especies silvestres. Se evaluó el polimorfismo y se determinó si los alelos polimórficos permitían diferenciar genotipos resistentes de susceptibles. Se comparó el tamaño de los fragmentos obtenidos con los fragmentos esperados asociados con resistencia de acuerdo a reportes. El análisis se realizó considerando presencia/ausencia de los fragmentos: CosA210, CosA250, R11400, R11800, BA47f2500, GP179570, Prp1300, Prp1600, y Prp1900. Los resultados indicaron que en los cultivares tetraploides y silvestres, se presentaron polimorfismos en todos los marcadores evaluados, con excepción del marcador GP179. No se encontró correlación entre el rasgo de resistencia y los alelos. Los resultados de este estudio muestran que hay repuesta diferencial a los marcadores entre las subsp. tuberosum y subsp. Andigena.

Potato is an important worldwide crop seriously affected by late blight disease caused by the oomycete Phytophthora infestans. Currently, the most effective way to control the disease is developing resistant cultivars to the pathogen by identifying genes that confer resistance to the pathogen. For this purpose it is important to find molecular markers associated with the trait. In this study, the SCAR (Sequence Characterized Amplified Region) markers: CosA, GP179, BA47f2 y Prp1, associated with late blight and the resistant gen R1 were evaluated in 22 tetraploid cultivars from subspecie andigena and five wild potato species. Polymorphism was evaluated and it was evaluated if polymorphic alleles allow differentiating resistant from susceptible genotypes. The fragment length for each marker was compared to the allele size reported associated to resistance. The analysis considered the presence/absence of the fragments: CosA210, CosA250, R11400, R11800, BA47f2500, GP179570, Prp1300, Prp1600 and Prp1900. The results indicated that both, tetraploid cultivars and wild potatoes, showed polymorphisms with all these markers, except with the GP179 marker. It was not found correlation between resistance and the presence of specific alleles. Evidence found in this study indicates that results obtained with molecular markers differed between subsp. tuberosum and subsp. andigena.

Controle da requeima em batata cv. 'Asterix' como base para modelos de previsão da doença / Controlling potato cv. 'Asterix' late blight base on forecast systems

O controle da requeima da batata requer aplicação freqüente de fungicidas, o que encarece a produção, impactando de modo desnecessário o ambiente. A utilização de modelos de previsão dessa doença permitiria reduzir as aplicações sem afetar a produção. Neste trabalho, objetivou-se avaliar os modelos "Blitecast e Prophy" como referência para o controle da requeima por fungicidas. Os experimentos foram conduzidos na primavera de 2004 e no outono de 2005, em Santa Maria, RS. Os dados meteorológicos foram medidos no centro da área experimental, a 0,10 e a 1,50 m acima da superfície do solo. Utilizaram-se diferentes valores de severidade (VS) acumulada, calculada pelos modelos "Blitecast" (VS= 18, 24, 30, 36 e 42) e "Prophy" (VS= 15, 20, 25, 30 e 35) que se constituíram os tratamentos, adicionando-se o tratamento com aplicação semanal e a testemunha, sem aplicação. O delineamento foi inteiramente casualizado com quatro repetições, sendo cada parcela composta de quatro fileiras de plantas com 5 m de comprimento. Avaliou-se a severidade da requeima por parcela a cada três a cinco dias. Verificou-se que o uso do modelo "Blitecast" com 18 valores de severidade acumulados, incrementou, em pelo menos, 42,6 por cento a produtividade de tubérculos comerciais em relação às áreas sem aplicação de fungicida e reduziu o número de aplicações em 25 por cento nos períodos úmidos e, em 70 por cento nos períodos secos, em relação às aplicações semanais. A eficiência de controle da requeima foi similar à obtida com aplicações semanais de fungicida nos tratamentos Bli18 e Pro15. O uso do modelo "Prophy" requer maior número de aplicações do que o "Blitecast" e não resultou em melhor controle.

The control potato late blight needs a great number of fungicide sprayings. These increase the costs of cropping and cause undesirable environmental impacts. The use of forecast systems to predict disease has the potential of reducing fungicide applications without reducing yield. The objective of this study was to evaluate the performance of Blitecast and Prophy systems as a reference model for predicting late blight potato and support decision of spray fungicides. Experiments were carried out during Spring 2004 and Autumn 2005, in Santa Maria, RS, Brazil. Meteorological data were measured in the center of the experimental area at 0.10 and 1.50 m above soil surface. Different accumulated severity values (VS) were calculated with 'Blitecast' (VS = 18, 24, 30, 36 and 42) and 'Prophy' (VS = 15, 20, 25, 30 and 35) forecast systems. These values were used to perform. Two additional treatments were the weekly sprays and without fungicides. The experimental design was a completely randomized, with four replications. Each plot had four rows plants with 5 m length. Late blight severity was evaluated in each three to five days. The fungicide spraying schedule based on Blitecast system with 18 accumulated severity values increased tuber yield at least 42.6 percent compared to the control without fungicides treatment. It also reduced the number of sprayings by 25 percent during wet periods and 70 percent during dry periods compared to weekly sprayings. The efficiency of controlling late blight was similar to the weekly sprayings treatment in the treatments Bli18 e Pro15. The Prophy model predicted higher number of fungicide sprayings than the Blitecast system and did not improve disease control.

Inheritance of resistance to Phytophthora infestans (Peronosporales, Pythiaceae) in a new source of resistance in tomato (Solanum sp. (formerly Lycopersicon sp.), Solanales, Solanaceae)

In Brazil, no commercial tomato (Solanum lycopersicum L. formerly Lycopersicon esculentum Mill.) varieties are available which are resistant to the late blight, one of the most important tomato diseases, produced by the phytopathogenic oomycete Phytophthora infestans. The wild tomato (Solanum habrochaites Knapp & Spooner, formerly Lycopersicon hirsutum Dunal) shows resistance to P. infestans, because of which we investigated an interspecific cross between S. lycopersicum cv. Santa Clara and S. habrochaites accession BGH 6902 maintained at the Horticultural Germplasm Bank at the Federal University of Viçosa (Banco de Germoplasma de Horticultura (BGH), Universidade Federal de Viçosa (UFV), Viçosa, Minas Gerais, Brazil) The genitors, F1, F2, BC1 and BC2 were used to study the inheritance of resistance to P. infestans and to estimate the genetic parameters associated with resistance. Analysis of the area under the disease progress curve (AUDPC) indicated that inheritance is polygenic and that dominance controls character, whereas mean analysis showed that the additive effect was the most important. Although the character presents variability, the heritability is low which generates the need to better control the environment to obtain success with the selection.