Uma escala diagramática para a avaliação da severidade da seca-de-ponteiros do eucalipto causada por Erwinia psidii

This study aimed to develop and validate a standard area diagram (SAD) set to estimate the severity of bacterial blight of eucalyptus caused by Erwinia psidii. For this purpose, an eightlevel SAD was developed and validated by ten inexperienced raters. Accuracy and precision of the estimates by each rater, with and without the SAD, were determined based on Lin’s concordance correlation coefficient. The proposed SAD improved the accuracy and precision of the estimates. The SAD set studied here is a useful tool in assessments of bacterial blight of eucalyptus for epidemiological research and breeding programs.Este trabalho objetivou o desenvolvimento de uma escala para estimar a severidade da seca-de-ponteiros do eucalipto causada por Erwinia psidii. Para isso, uma escala de oito níveis foi desenvolvida e validada por dez avaliadores inexperientes. A acurácia e precisão das estimativas de cada avaliador, com e sem a escala, foram determinadas baseadas no coeficiente de correlação concordante de Lin. A escala proposta melhorou a acurácia e a precisão das estimativas. A escala estudada se mostrou uma ferramenta útil na avaliação da seca-de-ponteiros do eucalipto para estudos epidemiológicos e em programas de melhoramento

Inheritance of coffee leaf rust resistance in Timor Hybrid UFV 443-03

O objetivo deste trabalho foi caracterizar a herança da resistência do Híbrido de Timor UFV 443-03 à ferrugem-do-cafeeiro (Hemileia vastatrix). Para isso, a raça II e o patótipo 001 de ferrugem foram inoculados em 246 plantas da população F2, 115 plantas do retrocruzamento suscetível (RCS) e 87 plantas do retrocruzamento resistente (RCR), originadas do cruzamento entre o genótipo suscetível cv. Catuaí Amarelo IAC 64 e a fonte de resistência Híbrido de Timor UFV 443-03. Para ambos os inóculos, a cv. Catuaí Amarelo IAC 64 foi suscetível, enquanto o Híbrido de Timor UFV 443-03, a planta representante da geração F1 e as plantas do RCR foram resistentes. As plantas F2, quando inoculadas com a raça II, apresentaram dois padrões de segregação significativos: 15:1 e 61:3. A herança da resistência foi confirmada pela inoculação das plantas do RCS, que segregaram na proporção de 3:1, padrão esperado para herança condicionada por dois genes. A hipótese de segregação 7:1 para três genes foi rejeitada. Resultados semelhantes foram obtidos para o patótipo 001. Dois genes dominantes e independentes conferem a resistência genética do Híbrido de Timor UFV 443-03 à raça II e ao patótipo 001 de H. vastatrix.The aim of this work was to characterize the resistance inheritance of the Timor Hybrid UFV 443-03 to coffee leaf rust (Hemileia vastatrix). For this, the race II and pathotype 001 of coffee leaf rust were inoculated in 246 F2 plants, 115 susceptible backcrossing (BCS) plants, and 87 resistant backcrossing (BCR) plants, derived from the crossing between the susceptible genotype 'Catuaí Amarelo' IAC 64 and the resistance source Timor Hybrid UFV 443-03. For both inoculums, the 'Catuaí Amarelo' IAC 64 was susceptible, while the Timor Hybrid, the plant representing F1 generation, and the BCR plants were resistant. The F2 plants inoculated with race II presented two significant segregation ratios: 15:1 and 61:3. The resistance inheritance was verified by the inoculation of the BCS plants, which segregated at a 3:1 ratio, an expected pattern for the inheritance controlled by two genes, whereas the segregation hypothesis of 7:1 for three genes was rejected. Two independent and dominant genes confer the genetic resistance of Timor Hybrid UFV 443-03 to race II and pathotype 001 of H. vastatrix

Characterization, pathogenicity and anastomosis groups of Rhizoctonia solani from watermelon

The objective of this study was to characterize the morphological and pathogenic variation of Rhizoctonia solani isolates as well as to determine mycelial compatibility and hyphal fusion. The R. solani isolates CMM1053, CMM2967, CMM1052, CMM2983, CMM2971 and CMM3890 from watermelon were used. The determination of aggressiveness was evaluated using the six isolates inoculated in the Crimson Sweet susceptible cultivar in a completely randomized design (CRD) with five replicates, the sample unit consisting of one plant. The experiment of mycelial growth rate was installed in the factorial scheme, 6 isolates x 3 culture media, using the following culture media Nutrient Agar, PDA and PSA, and a total of 5 replicates. The color characterization and sclerotia formation was performed 15 days after the fungal inoculation in each culture medium. For the characterization of vegetative compatibility and occurrence of hyphal fusion, the experiments were performed in CDR with three and two replicates, respectively. CMM1053 and CMM1052 isolates were the most aggressive; however, they were statistically different only from CMM2967 isolate. The PSA medium was the most promising for the mycelial growth. It was possible to observe that there was variability in the colonies color, being higher in the Nutrient Agar medium. Based on evaluations of vegetative compatibility and hyphal fusion, the six isolates belong to the same anastomosis group.The objective of this study was to characterize the morphological and pathogenic variation of Rhizoctonia solani isolates as well as to determine mycelial compatibility and hyphal fusion. The R. solani isolates CMM1053, CMM2967, CMM1052, CMM2983, CMM2971 and CMM3890 from watermelon were used. The determination of aggressiveness was evaluated using the six isolates inoculated in the Crimson Sweet susceptible cultivar in a completely randomized design (CRD) with five replicates, the sample unit consisting of one plant. The experiment of mycelial growth rate was installed in the factorial scheme, 6 isolates x 3 culture media, using the following culture media Nutrient Agar, PDA and PSA, and a total of 5 replicates. The color characterization and sclerotia formation was performed 15 days after the fungal inoculation in each culture medium. For the characterization of vegetative compatibility and occurrence of hyphal fusion, the experiments were performed in CDR with three and two replicates, respectively. CMM1053 and CMM1052 isolates were the most aggressive; however, they were statistically different only from CMM2967 isolate. The PSA medium was the most promising for the mycelial growth. It was possible to observe that there was variability in the colonies color, being higher in the Nutrient Agar medium. Based on evaluations of vegetative compatibility and hyphal fusion, the six isolates belong to the same anastomosis group

Inheritance and mapping of QTLs for resistance of Híbrido de Timor to the coffee leaf rust

Este trabalho teve como objetivos estudar a herança da resistência do Híbrido de Timor UFV 443-3 a Hemileia vastatrix e identificar QTLs associados à resistência à ferrugem do cafeeiro. Para o estudo da herança, foram utilizadas 246 plantas da população F2, originadas da autofecundação controlada do F1 H 511-1, 115 plantas do retrocruzamento suscetível (RCS) e 87 do retrocruzamento resistente (RCR), derivados de cruzamentos do F1 com o genótipo Catuaí Amarelo IAC 64 (UFV 2148-57) e o Híbrido de Timor UFV 443-3, respectivamente. Essas plantas foram inoculadas com a raça II de H. vastatrix e um isolado coletado de Coffea arabica Oeiras , de raça desconhecida, denominado patótipo 001, ambos isolados de lesões monopustulares. Para os dois patótipos, o Catuaí Amarelo UFV 2148-57 foi suscetível, enquanto que o Híbrido de Timor UFV 443-3, a F1 e as plantas do RCR foram resistentes. As plantas F2, quando inoculadas com a raça II, apresentaram duas segregações significativas pelo teste Qui-quadrado, 15:1 (P=24,92%) e 61:3 (P=87,27%). A herança da resistência foi confirmada pela inoculação das plantas do RCS que segregaram na proporção de 3:1 (P=17,83%), esperado para os dois genes, enquanto que a segregação 7:1, esperada para três genes, foi rejeitada. Estes dados sugerem que dois genes dominantes e independentes conferem a resistência desse Híbrido de Timor à raça II de H. vastatrix. Resultados semelhantes foram obtidos com o patótipo 001, onde foi observada segregação de 15:1 (P=92,13%) na F2 e de 3:1 (P=78,78%) no RCS, demonstrando, também, que dois genes dominantes e independentes controlam a resistência do Híbrido de Timor a esse outro patótipo. Para a identificação de QTLs associados à resistência do Híbrido de Timor UFV 443-3 a H. vastatrix, 286 marcadores moleculares (282 SSR e 4 RAPD) foram analisados nos parentais. Os marcadores polimórficos (21 SSR e 4 RAPD) foram utilizados para amplificar o DNA das 246 plantas F2 e construir o mapa genético. Dos 25 marcadores analisados, dois não se ligaram a nenhum dos seis grupos de ligação formados pelos 23 marcadores restantes, que cobriram 277,90 cM do genoma. Três QTLs foram identificados e designados como QTLHv1, QTLHv2 e QTLHv3, que explicaram, respectivamente, 5,94%, 5,52% e 15,92% da variação fenotípica. Os valores de LOD e distância entre as marcas e respectivos QTLs foram de 3,69 e 14 cM para o QTLHv1, 3,18 e 0,5 cM para o QTLHv2 e 10,33 e 22 cM para o QTLHv3. Este é o primeiro relato da utilização de marcadores SSR na identificação de QTLs associados à resistência do cafeeiro a H. vastatrix. Esses QTLs poderão ser utilizados na seleção assistida para a introgressão de genes de resistência do Híbrido de Timor UFV 443-3 à ferrugem nos genótipos comerciais.The objectives of this work were to study the resistance inheritance of the Híbrido Timor UFV 443-3 to Hemileia vastatrix and identify QTLs associated with resistance to coffee leaf rust. To study the inheritance we used a population of 246 individuals, produced from the controlled self-pollinated F1 H 511-1, 115 susceptible backcrossing (BCS) plants, and 87 resistant backcrossing (BCR) plants, originated from the crossing between F1 with Catuaí amarelo UFV 2148-57 and Híbrido de Timor UFV 443-3, respectively. These populations were inoculated with the race II, and a noncharacterized field isolate, designated pathotype 001, both from a single pustule-isolate of H. vastatrix. For both pathotypes, the Catuaí amarelo UFV 2148-57 was susceptible, while the Híbrido de Timor, the F1, and the BCR plants were resistant. The F2 plants inoculated with the race II showed two goodness of fit by the chi-square test, 15:1 (P=24.92%) and 61:3 (P=87.27%). The resistance inheritance was confirmed by the inoculation of BCs plants which segregated in a rate of 3:1 (P=17.83%), expected for the two genes, whereas the hypothesis of segregation 7:1, expected for three genes, was rejected. These results demonstrate that two independent dominant genes are responsible for the resistance of the Híbrido de Timor 443-3 to the race II of H. vastatrix. Similar results were observed with the pathotype 001 showing a segregation of 15:1 (P=92.13%) in the F2, and 3:1 (P=78.78%) in the BCs. These data indicate that two independent dominant genes, also, control the resistance of the Híbrido de Timor to this pathotype. To identify QTLs associated with the resistance of the Híbrido de Timor UFV 443-3 to coffee leaf rust we tested 286 molecular markers (282 SSR and 4 RAPD) in the parental genotypes. Those polymorphic markers (21 SSR and 4 RAPD) were used to screening the 246 F2 plants and to construct the linkage map. Among the 25 analyzed markers, two did not match to any of the six linkage groups formed by the 23 remaining markers, covering 277.90cM of the genome. Three QTLs were identified, QTLHv1, QTLHv2 and QTLHv3, that explain, 5.94%, 5.52% and 15.92% of the phenotypic variation respectively. The LOD score and the recombination frequency between the marker and respective QTLs were 3.69 and 14cM to the QTLHv1, 3.18 and 0.5cM to the QTLHv2, and 10.33 and 22cM to the QTLHv3. This is the first report of SSR markers in the identification of QTLs associated to the coffee tree resistance to H. vastatrix. These QTLs could be used in the assisted selection for introgression of genes for resistance from the Híbrido de Timor UFV 443-3 to coffee leaf rust into commercial genotypes.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Epidemiology and resistance of coffee conilon to rust

Nos últimos anos a ferrugem no cafeeiro conilon (Coffea canephora), causada por Hemileia vastatrix, tem ocorrido no campo sob grandes epidemias. Pouco se conhece sobre esse patossistema e a partir de questionamentos sobre o hospedeiro, o patógeno e o ambiente dessa interação surgiu o interesse em desenvolver este trabalho, que teve como objetivos: 1) determinar que temperatura e períodos de molhamento que favorecem a germinação e a infecção de H. vastatrix no cafeeiro conilon e caracterizar, em condições de campo, a influência de variáveis macroclimáticas na epidemia da doença; 2) elaborar e validar uma escala diagramática precisa e acurada para a ferrugem do cafeeiro; 3) caracterizar a resistência horizontal dos genótipos da variedade Conilon Vitória Incaper 8142, agrupando-os em níveis de resistência à três raças de H. vastatrix; 4) avaliar a eficiência de fungicidas triazóis aplicados via solo com complementação foliar no controle da ferrugem em cafeeiro conilon e estimar o dano causado pela doença nesse cafeeiro. Experimentos no delineamento inteiramente casualizado foram realizados para determinar a temperatura e períodos de molhamento mais favoráveis à germinação e a infectividade de H. vastatrix. As análises de regressão foram realizadas para modelar os dados. Os resultados mostraram que temperaturas entre 21,6 e 23,6°C e molhamento foliar superior a 24 horas é a condição mais favorável à germinação e infecção do conilon por H. vastatrix. Esses resultados auxiliaram no desenvolvimento das funções discriminantes do segundo objetivo da tese. Para alcançar este objetivo os dados históricos de clima de três municípios do norte do Espírito Santo e os dados de intensidade da doença foram utilizados para criar as funções discriminantes. Historicamente os meses do ano mais favoráveis à infecção de H. vastatrix são de maio a outubro. Nesses períodos as temperaturas médias mensais são amenas (próximo a 22°C) com alta umidade relativa (>80%), associado à baixa precipitação mensal (<50mm), porém com molhamento foliar. Para criar e validar uma escala diagramática para a ferrugem do cafeeiro foi coletada e escaneada folhas doentes de C. arabica Catuaí Vermelho IAC144 e C. canephora Clone 02. A escala foi validada por dez avaliadores. A severidade das folhas doentes foi estimada, primeiramente sem o uso da escala e, posteriormente, com o uso da escala. Análises de regressão e de correlação concordante de Lin entre os dados estimados e reais de severidade mostraram que a precisão e a acurácia foram significativamente melhores usando a escala. A análise dos dados também mostrou que a escala apresentou alta reprodutibilidade, podendo ser utilizada por várias pessoas em uma mesma quantificação de um experimento. Para determinar a resistência quantitativa em mudas da variedade Conilon Vitória Incaper 8142, foram utilizadas as raças I, II e XXXIII de H. vastatrix em um delineamento inteiramente casualizado. Após as inoculações onze componentes de resistência foram avaliados: períodos de incubação e latente, produção de esporos, área foliar lesionada, produção de esporos por área foliar lesionada, área foliar esporulada, produção de esporos por área foliar esporulada, severidade com o uso da escala proposta, frequência de infecção, número total de pústulas e taxa de expansão das lesões. O uso de análises multivariadas de agrupamento e de discriminantes com os onze componentes de resistência possibilitou determinar quatro níveis de resistência: plantas resistentes, moderadamente resistentes, moderadamente suscetíveis e suscetíveis. O grupo de plantas mais resistentes (resistentes ou moderadamente resistentes) às três raças de H. vastatrix foram constituídas pelos clones 3V e 5V da variedade. Para testar a eficiência de triazóis e estrobilurinas via solo com ou sem complementação foliar no controle da ferrugem, foi instalado um experimento no delineamento em blocos casualizados com oito tratamentos. A cada 30 dias foram coletadas folhas das parcelas experimentais para a aferição da incidência e severidade da doença. A produção também foi quantificada nos anos de condução do experimento. Com esses dados foram traçadas as curvas de progresso da doença e calculada a área abaixo da curva de progresso para a incidência da doença. Os dados de intensidade de doença e produção também foram usados para estimar o dano causado pela ferrugem no clone 02 do cafeeiro conilon. O clima durante a condução do experimento apresentou vários meses favoráveis ao desenvolvimento da ferrugem. Ocorreram duas epidemias durante a condução do experimento, uma típica com um pico ocorrido no mês de julho e outra atípica com um pico em janeiro. Os tratamentos com as aplicações via solo foram eficientes no controle da doença, porém, analisando conjuntamente o controle da doença e a produtividade, os melhores tratamentos foram os que utilizaram o cipronazol ou o flutriafol via solo, com ou sem complementação foliar. O dano causado pela ferrugem no clone 02 do cafeeiro conilon pode alcançar 47% se não forem implantadas medidas de controle da doença.In recent years the rust in conilon coffee (Coffea canephora), caused by Hemileia vastatrix, has occurred in large epidemics in the field. Little is known about this pathosystem and from questions about the host, pathogen and environment of this interaction became interested in developing this work, which aimed to: 1) to determine what temperature and wetness periods that favor germination and infection of H. vastatrix in conilon coffee and characterize, in field conditions, the influence of variables macroclimatic the epidemic of disease, 2) develop and validate a diagrammatic scale for coffee rust, 3) characterize the horizontal resistance of the variety of genotypes Conilon Incaper Victoria 8142, grouping them into levels of resistance to three races of H. vastatrix, 4) evaluate the efficiency of triazole fungicides applied to the soil with supplementation in the control of leaf rust in conilon coffee and estimate the damage caused by disease is this coffee. Experiments in a completely randomized design were performed to determine the temperature and wetness periods favorable for germination and infectivity of H. vastatrix. Regression analysis was performed to model the data. The results showed that temperatures between 21.6 and 23.6°C and leaf wetness exceeding 24 hours is the most favorable condition for germination and infection of conilon by H. vastatrix. These results helped to develop the discriminant functions of the second objective of the thesis. To achieve this objective, the historical data of climate in three municipalities in the north of Espirito Santo and the disease severity data were used to create the discriminant functions. Historically the months of the year most favorable to the infection of H. vastatrix are from May to October. At these times the monthly average temperatures are mild (near 22°C) with high humidity (>80%), associated with low monthly precipitation (<50mm), but with leaf wetness. To create and validate a diagrammatic scale for coffee rust was collected and scanned diseased leaves of C. arabica Catuaí IAC144 and C. canephora clone 02. The scale was validated by ten raters. The severity of diseased leaves was estimated first without the use of the scale and then using the scale. Regression analysis and Lin s concordance correlation between the data estimated and actual severity showed that the precision and accuracy were significantly better using the scale. The data analysis also showed that the scale presented high reproducibility and can be used by several people in the same quantification of an experiment. To determine the quantitative resistance in seedlings of the variety Conilon Incaper Victoria 8142, we used the races I, II and XXIII of H. vastatrix in a completely randomized design. After inoculations eleven resistance components were evaluated: incubation and latent periods, spore production, leaf area lesioned, number of spores per leaf area lesioned, sporulated leaf area, number of spores per sporulated leaf area, severity scale using the proposed, infection frequency, total number of pustules and expansion rate of the lesions. The use of multivariate analysis discriminant and of cluster with the eleven components of resistance possible to determine four levels of resistance: resistant plants, moderately resistant, moderately susceptible and susceptible. The group of plants more resistant (resistant or moderately resistant) to three races of H. vastatrix were established by clones 3V and 5V of the variety. To test the efficiency of triazoles in the soil with or without supplementation leaf in the control of leaf rust, an experiment was conducted in randomized block design with eight treatments. Every 30 days leaves were collected from experimental plots to measure the incidence and severity of disease. The production was also measured in years of conducting the experiment. With these data were plotted curves of disease progress and calculated the area under the disease progress curve for incidence of the disease. The intensity data of disease and production were also used to estimate the damage caused by rust in conilon coffee clone 02. The weather during the experiment had several months to promote the development of rust. Two epidemics occurred during the experiment, with a typical peak occurred in July and another with an atypical peak in January. The treatments with the soil applications were effective in controlling the disease, however, jointly analyzing disease control and productivity, the best treatments were those who used or cipronazol flutriafol in the soil, with or without supplementation leaf. The damage caused by rust in conilon coffee clone 02 can reach 47% if not implemented measures to control the disease.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Herança da resistência do Híbrido de Timor UFV 443-03 à ferrugem- do- cafeeiro

O objetivo deste trabalho foi caracterizar a herança da resistência do Híbrido de Timor UFV 443-03 à ferrugem-do-cafeeiro (Hemileia vastatrix). Para isso, a raça II e o patótipo 001 de ferrugem foram inoculados em 246 plantas da população F2, 115 plantas do retrocruzamento suscetível (RCS) e 87 plantas do retrocruzamento resistente (RCR), originadas do cruzamento entre o genótipo suscetível cv. Catuaí Amarelo IAC 64 e a fonte de resistência Híbrido de Timor UFV 443-03. Para ambos os inóculos, a cv. Catuaí Amarelo IAC 64 foi suscetível, enquanto o Híbrido de Timor UFV 443-03, a planta representante da geração F1 e as plantas do RCR foram resistentes. As plantas F2, quando inoculadas com a raça II, apresentaram dois padrões de segregação significativos: 15:1 e 61:3. A herança da resistência foi confirmada pela inoculação das plantas do RCS, que segregaram na proporção de 3:1, padrão esperado para herança condicionada por dois genes. A hipótese de segregação 7:1 para três genes foi rejeitada. Resultados semelhantes foram obtidos para o patótipo 001. Dois genes dominantes e independentes conferem a resistência genética do Híbrido de Timor UFV 443-03 à raça II e ao patótipo 001 de H. vastatrix.The aim of this work was to characterize the resistance inheritance of the Timor Hybrid UFV 443-03 to coffee leaf rust (Hemileia vastatrix). For this, the race II and pathotype 001 of coffee leaf rust were inoculated in 246 F2 plants, 115 susceptible backcrossing (BCS) plants, and 87 resistant backcrossing (BCR) plants, derived from the crossing between the susceptible genotype 'Catuaí Amarelo' IAC 64 and the resistance source Timor Hybrid UFV 443-03. For both inoculums, the 'Catuaí Amarelo' IAC 64 was susceptible, while the Timor Hybrid, the plant representing F1 generation, and the BCR plants were resistant. The F2 plants inoculated with race II presented two significant segregation ratios: 15:1 and 61:3. The resistance inheritance was verified by the inoculation of the BCS plants, which segregated at a 3:1 ratio, an expected pattern for the inheritance controlled by two genes, whereas the segregation hypothesis of 7:1 for three genes was rejected. Two independent and dominant genes confer the genetic resistance of Timor Hybrid UFV 443-03 to race II and pathotype 001 of H. vastatrix

Characterization, pathogenicity and anastomosis groups of Rhizoctonia solani from watermelon

The objective of this study was to characterize the morphological and pathogenic variation of Rhizoctonia solani isolates as well as to determine mycelial compatibility and hyphal fusion. The R. solani isolates CMM1053, CMM2967, CMM1052, CMM2983, CMM2971 and CMM3890 from watermelon were used. The determination of aggressiveness was evaluated using the six isolates inoculated in the Crimson Sweet susceptible cultivar in a completely randomized design (CRD) with five replicates, the sample unit consisting of one plant. The experiment of mycelial growth rate was installed in the factorial scheme, 6 isolates x 3 culture media, using the following culture media Nutrient Agar, PDA and PSA, and a total of 5 replicates. The color characterization and sclerotia formation was performed 15 days after the fungal inoculation in each culture medium. For the characterization of vegetative compatibility and occurrence of hyphal fusion, the experiments were performed in CDR with three and two replicates, respectively. CMM1053 and CMM1052 isolates were the most aggressive; however, they were statistically different only from CMM2967 isolate. The PSA medium was the most promising for the mycelial growth. It was possible to observe that there was variability in the colonies color, being higher in the Nutrient Agar medium. Based on evaluations of vegetative compatibility and hyphal fusion, the six isolates belong to the same anastomosis group

Resistance to Fusarium Wilt in watermelon accessions inoculated by chlamydospores

The present study aimed to evaluate different inoculation methods of Fusarium oxysporum f. sp. niveum in watermelon and the reaction of accessions from this crop. Firstly, seven inoculation methods using conidia were tested on the susceptible cultivar Sugar Baby, including the standard dipping method. The methods initially tested were not efficient; therefore, we tested a new methodology using chlamydospores which are fungus survival structures. After the production of chlamydospores in vermiculite enriched with liquid culture media potato and sucrose (PS), the new method was tested on an experiment comparing inoculation by conidia and chlamydospores. For the conidia method, the plants were inoculated after their final leaf formed. For chlamydospores, inoculations were done in plants or sowed seeds. The use of chlamydospores in sowed seeds was effective for the inoculation of Fusarium oxysporum f. sp. niveum in watermelon and showed the highest severity scores in relation to the others methods. The inoculation method using chlamydospores also obtained the shortest means of root and shoot length in the cultivars Charleston Gray and Sugar Baby. Thus, using this methodology, 25 accessions from the watermelon germplasm were evaluated 21 days after inoculation with a grading scale. Eight accessions were classified as resistant, corresponding to 32% of accessions evaluated. Eight other accessions received the highest score of severity, proving the efficiency of the methology to evaluate the reaction to the disease

Herança da resistência do Híbrido de Timor UFV 443-03 à ferrugem-do-cafeeiro Inheritance of coffee leaf rust resistance in Timor Hybrid UFV 443-03

O objetivo deste trabalho foi caracterizar a herança da resistência do Híbrido de Timor UFV 443-03 à ferrugem-do-cafeeiro (Hemileia vastatrix). Para isso, a raça II e o patótipo 001 de ferrugem foram inoculados em 246 plantas da população F2, 115 plantas do retrocruzamento suscetível (RC S) e 87 plantas do retrocruzamento resistente (RC R), originadas do cruzamento entre o genótipo suscetível cv. Catuaí Amarelo IAC 64 e a fonte de resistência Híbrido de Timor UFV 443-03. Para ambos os inóculos, a cv. Catuaí Amarelo IAC 64 foi suscetível, enquanto o Híbrido de Timor UFV 443-03, a planta representante da geração F1 e as plantas do RC R foram resistentes. As plantas F2, quando inoculadas com a raça II, apresentaram dois padrões de segregação significativos: 15:1 e 61:3. A herança da resistência foi confirmada pela inoculação das plantas do RC S, que segregaram na proporção de 3:1, padrão esperado para herança condicionada por dois genes. A hipótese de segregação 7:1 para três genes foi rejeitada. Resultados semelhantes foram obtidos para o patótipo 001. Dois genes dominantes e independentes conferem a resistência genética do Híbrido de Timor UFV 443-03 à raça II e ao patótipo 001 de H. vastatrix.<br>The aim of this work was to characterize the resistance inheritance of the Timor Hybrid UFV 443-03 to coffee leaf rust (Hemileia vastatrix). For this, the race II and pathotype 001 of coffee leaf rust were inoculated in 246 F2 plants, 115 susceptible backcrossing (BCS) plants, and 87 resistant backcrossing (BC R) plants, derived from the crossing between the susceptible genotype 'Catuaí Amarelo' IAC 64 and the resistance source Timor Hybrid UFV 443-03. For both inoculums, the 'Catuaí Amarelo' IAC 64 was susceptible, while the Timor Hybrid, the plant representing F1 generation, and the BC R plants were resistant. The F2 plants inoculated with race II presented two significant segregation ratios: 15:1 and 61:3. The resistance inheritance was verified by the inoculation of the BCS plants, which segregated at a 3:1 ratio, an expected pattern for the inheritance controlled by two genes, whereas the segregation hypothesis of 7:1 for three genes was rejected. Two independent and dominant genes confer the genetic resistance of Timor Hybrid UFV 443-03 to race II and pathotype 001 of H. vastatrix