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 The Triplet-Septet (TS) set of melon cucurbit powdery mildew (CPM) race differentials (CPMRD) was established to provide an international means for objective and uniform identification and designation on CPM races. The Area Under Disease Progress Stairs (AUDPS) method for disease progress estimation was derived from the Area Under Disease Progress Curve (AUDPC) method, and both have been used to evaluate disease progress on other crops. We aimed to identify a melon CPM race on the TS melon CPMRD, and estimate disease progress thereon using AUDPC and AUDPS. Plants were inoculated at the 3 to 4 true leaf stage. Severity of CPM infection was evaluated on the 21 TS melon CPMRD at 15, 22, 32, and 41 days after inoculation (DAI) using a visual scale. The CPM population in the greenhouse was identified as race S based on reactions of a set of 11 commonly used melon CPMRD, and it may also be designated as 127.127.126 on the TS melon CPMRD. AUDPS identified higher levels of disease than AUDPC, and its results agreed with those obtained by the commonly used melon CPMRD conventional race identification methods (current and Triplet-Septet). AUDPS can be used to evaluate the disease progress on CPM.

Abstract The objective of this work was to evaluate the performance of okra grafted onto Hibiscus spp. in the presence and absence of three root knot nematode species. The experimental design was completely randomized in a 4x4 factorial arrangement with ten replicates. The first factor consisted of the following four rootstocks: kenaf (Hibiscus cannabinus), false roselle (Hibiscus acetosella), self-grafted, and non-grafted. The second factor was the inoculation of 5,000 eggs and second-stage juveniles of Meloidogyne incognita, Meloidogyne javanica, and Meloidogyne enterolobii in okra plants, plus an uninoculated control. Vegetative development, agronomic performance, and nematode reproduction were evaluated. The grafting of okra onto Hibiscus spp. in the presence of root-knot nematodes provided a greater plant height, scion length, fresh shoot mass, number of fruits, and yield, when compared with self-grafted and non-grafted plants. The averages of the root-knot nematode reproduction factor were low in the plants grafted onto Hibiscus spp., indicating that grafting in the presence of root-knot nematodes is capable of maintaining okra vegetative development and yield.

Resumo O objetivo deste trabalho foi avaliar o desempenho de quiabo enxertado em Hibiscus spp. na presença e na ausência de três espécies de nematoides-de-galha. O delineamento experimental foi inteiramente casualizado, em arranjo fatorial 4x4, com dez repetições. O primeiro fator foi constituído pelos quatro seguintes porta-enxertos: vinagreira-roxa (Hibiscus cannabinus), vinagreira-flor-de-veludo (Hibiscus acetosella), autoenxertia e pé-franco. O segundo fator foi a inoculação de 5.000 ovos e juvenis de segundo estágio de Meloidogyne incognita, Meloidogyne javanica e Meloidogyne enterolobii em plantas de quiabo, além de testemunha não inoculada. Foram avaliados desenvolvimento vegetativo, desempenho agronômico e reprodução do nematoide. A enxertia de quiabo em Hibiscus spp. na presença de nematoides proporcionou maiores altura de planta, comprimento de enxerto, massa fresca da parte aérea, número de frutos e produtividade, em comparação às plantas autoenxertadas e pé-franco. As médias do fator de reprodução dos nematoides foram baixas nas plantas enxertadas em Hibiscus spp., o que indica que a enxertia na presença de nematoides é capaz de manter o desenvolvimento vegetativo e a produção do quiabo.

ABSTRACT Melon is a vegetable of great socioeconomic importance, and its cultivation is carried out under different production systems. The protected cultivation of melon can be carried out in coconut shell fiber, which is a substrate widely used in olericulture, but little information is available regarding its continuous use in more than one cultivation cycle. Therefore, this study aimed to evaluate the performance of muskmelon hybrids as a function of the reuse of coconut shell fiber with fertigation in a protected environment. The experiment was carried out in a greenhouse from March to July 2008 and designed in randomized blocks in a 2×3 factorial arrangement, with four replications. The factors consisted of two hybrids (‘Bonus 2’ and ‘Fantasy’) and three types of substrate (S1: new coconut shell fiber; S2: coconut shell fiber reused once in sweet pepper cultivation; and S3: coconut shell fiber reused twice, i.e., first in sweet pepper cultivation and then in melon cultivation). Transverse and longitudinal fruit diameter, fruit shape index, transverse and longitudinal locule diameter, locule shape index, peduncle insertion diameter, mesocarp thickness, firmness, skin netting, fresh mass, soluble solids, titratable acidity, pH, and yield were evaluated after harvest. Reusing twice the coconut shell fiber as a substrate did not affect the agronomic and physicochemical characteristics of the hybrids Bonus 2 and Fantasy.

RESUMO O meloeiro é uma hortaliça de grande importância socioeconômica, sendo seu cultivo realizado em diferentes sistemas produção. Em ambiente protegido o cultivo do meloeiro pode ser realizado em em fibra da casca de coco, que é um substrato amplamente utilizado na olericultura, contudo, poucas informações existem quanto ao uso continuo de um mesmo substrato em mais de um ciclo de cultivo. Assim, objetiva-se avaliar o desempenho de híbridos de melão rendilhado em função da reutilização da fibra da casca de coco com fertirrigação em ambiente protegido. O experimento foi conduzido em casa de vegetação de março a julho de 2008. O experimento foi delineado em blocos casualizados, esquema fatorial 2x3, com quatro repetições. Os fatores foram dois híbridos, ‘Bônus no 2’ e ‘Fantasy’ e três tipos de utilização de substrato (S1 = fibra da casca de coco nova; S2 = fibra da casca de coco reutilizada uma vez na cultura do pimentão; e, S3 = fibra da casca de coco reutilizada por duas vezes, 1a na cultura do pimentão e 2a na cultura do melão). Após a colheita foram avaliados: diâmetro transversal e longitudinal do fruto, índice de formato de fruto, diâmetro transversal e longitudinal do lóculo, índice de formato do lóculo, diâmetro da inserção do pedúnculo, espessura do mesocarpo, firmeza, rendilhamento da casca, massa fresca, sólidos solúveis, acidez titulável, pH e produtividade. Com base nos resultados, concluiu-se o reuso de fibra da casca de coco como substrato por duas vezes não alterou as características agronômicas e físico-químicas dos híbridos Bônus n.2 e Fantasy.

Abstract The exploration of heterosis can be an efficient alternative to increase okra yield. The partial diallel strategy optimizes resources by guiding crosses based on genetic diversity between various genotypes. This study aimed to identify potential hybrid combinations through diallel analysis in comparison with commercial cultivars. The hybrids were evaluated by means of a partial diallel scheme based on the genetic divergence of the genotypes. Fourteen hybrids and their reciprocals were evaluated in the winter and summer conditions of Jaboticabal - SP for yield, number of fruits and precocity. No line showed significant general combining ability. The reciprocal effect was not significant for the evaluated characteristics. Four hybrid combinations showed significant and positive specific combining ability for number of fruits, which were considered promising hybrids. In the winter, the experimental hybrids 1 x 8 and 3 x 8 showed superior performance compared to the commercial hybrids. No significant differences were observed in the summer.

RESUMO A pimenta Habanero é popular no mercado internacional e começa a despertar maior interesse no nacional, porém poucas cultivares adaptadas às condições edafoclimáticas e com resistência às principais doenças como murcha bacteriana (MB) e murcha de fitóftora (MF), causadas respectivamente por Ralstonia pseudosolanacearum (RP) e Phytophthora capsici (PC), estão disponíveis no Brasil. O objetivo deste estudo foi avaliar a reação de linhagens avançadas de pimenta do grupo Habanero desenvolvidas pelo programa de melhoramento da Embrapa Hortaliças à MB e MF. Apesar de não ser exigida no processo de registro, proteção e lançamento de novas cultivares, esta informação é importante para os produtores. As linhagens avançadas identificadas como CNPH 15.737, CNPH 15.740, CNPH 15.744, CNPH 15.745, CNPH 15.749 e CNPH 15.750 foram inoculadas com três isolados de RP e um de PC. Quantificaram-se as plantas com folhas murchas (RP) e com necrose do caule, murcha das folhas e tombamento para PC. A área total abaixo da curva de progresso da doença (AACPD) foi obtida utilizando-se valores de incidência e, também, o índice de severidade para RP. CNPH 15.740 e CNPH 15.737 apresentaram alta resistência a RP. CNPH 15.749 apresentou nível moderado de resistência à PC. Merece destaque especial a linhagem CNPH 15.740, com nível elevado de resistência aos isolados de RP e intermediário a PC e que também possui características agronômicas desejáveis tendo, portanto, alto potencial como nova cultivar a ser disponibilizada aos produtores.

ABSTRACT Habanero pepper is important in the international market and is becoming popular in the national market; however, few cultivars adapted and resistant to devastating diseases caused by the soilborne pathogens Ralstonia pseudosolanacearum (RP) and Phytophthora capsici (PC) are available in Brazil. The aim of this study was to evaluate the reaction of Habanero-type advanced inbred lines, developed by Embrapa Hortaliças breeding program, to RP and PC. Although not required for the process of protection, registration and release of new cultivars, this information is important. CNPH 15.737; CNPH 15.740; CNPH 15.744; CNPH 15.745; CNPH 15.749 and CNPH 15.750 were inoculated with three RP and one PC isolates. Plants showing wilted leaves (RP) and stem necrosis, leaf wilting and damping off (PC) were quantified. Total area under the disease progress curve (AUDPC) was obtained using incidence values and also severity index for RP. CNPH 15.740 and CNPH 15.737 were highly resistant to RP. CNPH 15.749 displayed considerable resistance levels to PC. CNPH 15.740 showed high resistance to RP isolates and intermediate resistance to PC isolates which also shows agronomic traits of interest to the sector, therefore with a high potential to be released as a new cultivar.

ABSTRACT. The development of melon lines resistant to gummy stem blight (GSB) is an important strategy for decreasing losses caused by this disease. Thus, selecting the best parents for such a goal is essential. We evaluated the general (GCA) and specific (SCA) combining abilities of lines and accessions to guide the selection of the most promising parents to develop GSB-resistant lines. Six genotypes representing two groups (group I - susceptible: group II - resistant) were crossed in a partial diallel mating design. The genotypes were evaluated for disease expression using a rating scale from 0 (resistant) to 4 (susceptible). Estimates of GCA were negative and significant for the accessions PI 420145 and PI 482398, which can be suggested for crosses aimed at obtaining melon lines resistant to GSB. There is a reciprocal effect for the resistance of melon genotypes to Didymella bryoniae, especially when PI 482398, PI 420145, and PI 140471 are crossed with JAB-20. Such results indicate that maternal effects may be involved in the resistance to gummy stem blight.

RESUMO A cultura da melancia apresenta grande importância econômica e social. Paralelamente, novos nichos de mercado são requeridos pelos consumidores, a fim de fornecer produtos diferenciados, dentre os quais destaca-se a minimelancia. Objetivou-se avaliar o desempenho agronômico e a qualidade de frutos de minimelancia cultivados em fibra de casca de coco, em função do número de hastes e densidade de planta. Utilizaram-se o híbrido Smile e delineamento experimental em blocos casualizados, em esquema fatorial 2 x 2, com oito repetições, sendo o primeiro fator constituído pelo número de hastes por planta (1 ou 2) e o segundo pelo número de plantas por vaso (1 ou 2). Foram avaliadas características relacionadas à produção, parâmetros fisiológicos da planta e qualidade de frutos. Houve interação entre o número de hastes e a densidade de plantas apenas para as características de área foliar, massa fresca média de frutos, produtividade total e percentual de frutos grandes, sendo que, para as demais características, os fatores foram avaliados separadamente. As plantas conduzidas com duas hastes, na densidade de uma planta por vaso, proporcionam maior produtividade, sem prejudicar a qualidade dos frutos, sendo, nessas condições, o método mais indicado para os produtores.

ABSTRACT Watermelon farming has a high economic and social importance. In parallel, the consumers’ demand for distinctive products has led to niche markets, where mini watermelons stand out. This study aimed to assess the agronomic performance and fruit quality of mini watermelon grown in coconut husk fiber, as a function of number of stems per plant and plant density. The Smile hybrid was used, as well as a randomized block design, in a 2 x 2 factorial scheme, with eight repetitions, being the first factor the number of stems per plant (1 or 2) and the second the number of plants per pot (1 or 2). Characteristics related to yield, physiological parameters and fruit quality were assessed. Interaction between number of stems and plant density was only observed for leaf area, average fruit fresh weight, total yield and percentage of large fruits. The factors were evaluated separately for the remaining traits. Two-stemmed training systems, at a density of one plant per pot, produce the highest yield, without compromising the quality of the fruits, being, in these conditions, the most suitable method for farmers.

Resumo: O objetivo deste trabalho foi estimar os danos causados por Meloidogyne enterolobii em quiabeiro (Abelmoschus esculentus) e verificar a confiabilidade do fator de reprodução como medição adequada para a seleção de genótipos de quiabeiro resistentes. Avaliaram-se populações crescentes de M. enterolobii - 0, 500, 1.500, 3.000, 5.000 e 7.000 ovos e juvenis de segundo estádio (J2) por planta -, em um delineamento inteiramente casualizado. O patógeno apresentou padrão de parasitismo similar ao de M. incognita, tendo causado redução significativa de parâmetros morfológicos e agronômicos. O fator de reprodução do patógeno deve ser usado na seleção de genótipos de quiabeiro quanto à tolerância a M. enterolobii, em populações acima de 3.000 ovos ou J2.

Abstract: The objective of this work was to estimate the damage caused by Meloidogyne enterolobii in okra (Abelmoschus esculentus) and to verify the reliability of the reproduction factor as a suitable measure for selecting resistant okra genotypes. Increasing populations of M. enterolobii - 0, 500, 1,500, 3,000, 5,000, and 7,000 eggs and second-stage juveniles (J2) per plant, - were evaluated, in a completely randomized design. The pathogen showed a parasitism pattern similar to that of M. incognita, causing a significant decrease in morphological and agronomic traits. The pathogen reproduction factor should be used in the selection of okra genotypes for tolerance to M. enterolobii, in populations above 3,000 eggs or J2.

ABSTRACT Root-knot nematodes are among the main agents that negatively affect the pepper and sweet pepper crop (Capsicum annuum L.), especially Meloidogyne incognita, M. javanica, and M. enterolobii. The objective of this study was to evaluate genotypes of C. annuum L. var. annuum in their response to infection by M. incognita race 3, M. javanica, and M. enterolobii. The experiment was conducted using a completely randomized design arranged in a 27 × 3 factorial scheme with six replicates and each plot consisted of one plant. The experiment was carried out at the UNESP-FCAV in Jaboticabal, Sao Paulo, Brazil. The genotypes were in plastic pots containing an autoclaved mixture of soil, sand, and bovine manure under greenhouse conditions, and they were evaluated for the reproduction index and reproduction factor at 90 d after inoculation. Thirteen genotypes were classified as resistant, based on the reproductive factor, and highly resistant, based on the reproduction index, to M. javanica, while six were resistant and highly resistant materials to M. incognita race 3. No materials resistant to M. enterolobii were identified. The genotypes CNPH 698, CNPH 701, CNPH 702, CNPH 717, and CNPH 718 were simultaneously classified as resistant to M. incognita race 3 and M. javanica based on the reproduction factor.

Resumo: O objetivo deste trabalho foi estimar a estabilidade e a adaptabilidade genotípica de linhagens avançadas e cultivares de alface-crespa (Lactuca sativa), em diferentes sistemas de cultivos e épocas, pelo modelo misto REML/Blup. Foram avaliados dez genótipos de alface, sete sistemas de cultivo e duas épocas, em 2015. Avaliaram-se os caracteres de produção das plantas, e os dados foram submetidos ao programa Selegen-REML/Blup. A estabilidade e a adaptabilidade genotípica foram analisadas pelos métodos da média harmônica dos valores genotípicos (MHVG) e do desempenho relativo dos valores genotípicos (PRVG), respectivamente. A média harmônica do PRVG (MHPRVG) foi utilizada para estimar simultaneamente a estabilidade, a adaptabilidade e a produtividade das linhagens e das cultivares. Ao se considerar a análise conjunta das duas épocas para o conjunto dos caracteres, as linhagens L6, L7 e L8 foram selecionadas como promissoras e recomendadas para plantio. As linhagens selecionadas para todas as épocas apresentam bons rendimentos e são consideradas superiores às cultivares comerciais Vanda e Vera.

Abstract: The objective of this work was to estimate the stability and genotypic adaptability of advanced lines and cultivars of curled green-leaf lettuce (Lactuca sativa), in different growing environments and seasons, using the REML/Blup mixed model. Ten genotypes, seven cropping environments, and two growing seasons were studied in 2015. Plant yield traits were evaluated, and data were subjected to the Selegen-REML/Blup software. Genotype stability and adaptability were analyzed using the harmonic mean of genotypic values (HMGV) and the relative performance of genotypic values (RPGV), respectively. The harmonic mean of RPGV (HMRPGV) was used to simultaneously estimate the stability, adaptability, and yield of breeding lines or cultivars. Considering the combined analysis of the two seasons for the set of traits, the lines L6, L7, and L8 were selected as promising ones and recommended for planting. The breeding lines selected for all season exhibit good yield and are considered superior to the commercial cultivars Vanda and Vera.

RESUMO O uso de resistência genética é um dos métodos mais adequados para o controle de oídio das cucurbitáceas em melão, causado por Podosphaera xanthii ou Golovinomyces orontii. Contudo, muitas raças desses patógenos têm sido descobertas, o que pode comprometer a eficácia desse método. Fazem-se, então, necessários o constante monitoramento de raças de oídio e a busca por novas fontes de resistência. Objetivou-se identificar em nível de raça uma população natural de oídio das cucurbitáceas em casa-de-vegetação, bem como avaliar a reação de genótipos locais e exóticos de meloeiro à raça identificada. A identificação da raça foi baseada na reação de oito linhagens diferenciadoras (PI 414723, PMR 45, PMR 5, WMR 29, Edisto 47, Nantais Oblong, PI 124111 e Védrantais). Foram avaliados 59 genótipos de meloeiro, sendo 53 destes acessos de germoplasma e seis linhagens de melão rendilhado, além de duas cultivares (Louis e Fantasy). As plantas foram avaliadas com base em escala visual para lesões nas folhas. A espécie P. xanthii foi confirmada como o agente causal, pela visualização de corpos de fibrosina nos conídios e pela resistência da abóbora d’água (Benincasa hispida). A raça 4 foi identificada pela primeira vez no estado de São Paulo. Os genótipos A19, A30, A32, C67, C384, JAB-3, JAB-7, JAB-9, JAB-11, JAB-18, JAB-20 e Solarking mostraram-se resistentes à raça 4.

ABSTRACT Genetic resistance is one of the most suitable strategies to control cucurbit powdery mildew (CPM) on melon, incited by Podosphaera xanthii or Golovinomyces orontii. However, many races of these pathogens have been reported worldwide in recent years, what may compromise the effectiveness of this method. Thus, annual surveys of CPM races and the screening of germplasm for new sources of genetic resistance provide a vital support to melon breeding programs. This study aimed at identifying a natural population of CPM race under greenhouse conditions, as well as evaluating the reaction of local and exotic melon germplasm for CPM-resistance. CPM race identity was based on the reaction of eight race differentials: Védrantais, Nantais Oblong, PMR 45, PMR 5, WMR 29, Edisto 47, PI 414723 and PI 124111. Fifty-nine melon genotypes were evaluated, 53 of them being germplasm accessions, and six net melon elite-inbred lines, besides two net melon-type cultivars (Louis and Fantasy). Plants were evaluated using a visual scale for leaf lesions. The causal pathogen was confirmed to be P. xanthii, based on the presence of fibrosin bodies in conidia and the complete resistance response of winter melon (Benincasa hispida). Race 4 was identified for the first time in the São Paulo state, Brazil. Genotypes A19, A30, A32, C67, C384, JAB-3, JAB-7, JAB-9, JAB-11, JAB-18, JAB-20 and Solarking showed to be resistant to the race 4.

RESUMO Uma das formas de melhoria da qualidade e da produção do tomateiro é a adoção de técnicas adequadas de manejo da cultura, destacando-se o uso da enxertia e o método de condução das plantas. Contudo, no Brasil, há falta de informações que estimulem essas práticas. Por isso, este trabalho teve por objetivo avaliar o desempenho de porta-enxertos para tomateiro, com vigoroso sistema radicular, conduzido com quatro hastes, em fibra da casca de coco, em ambiente protegido. Adotou-se o espaçamento de 2,0 m entrelinhas e 0,40 m entre plantas. Para isso, foi utilizado o delineamento em blocos casualizados, com quatro tratamentos e seis repetições, sendo, os tratamentos, dois porta-enxertos (‘Maxifort’ e ‘Multifort’), autoenxertia (‘Alambra’ em ‘Alambra’), e o pé franco (‘Alambra’). Cada parcela foi constituída de 20 plantas, sendo avaliadas as 14 plantas centrais. Não houve efeito significativo no uso dos porta-enxertos sobre as características de produção e de qualidade dos frutos. Na avaliação do estado nutricional, houve diferenças para os teores de P, Mg e Ca em plantas enxertadas. Portanto, os porta-enxertos ‘Maxifort’ e ‘Multifort’, cultivados nas condições em que o experimento foi realizado, não proporcionaram aumento da produção e da qualidade dos frutos.

ABSTRACT One way of improving the quality and production of tomato is the adoption of appropriate techniques for crop management, especially the use of grafting and conduction method of the plants. However, in Brazil, there is a lack of information to encourage such practices. Therefore, this study aimed to evaluate the performance of rootstocks for tomato plants, with vigorous root system, conducted with four stems, in coconut fiber, under protected cultivation. The adopted spacing was 2.0 m between rows and 0.40 m between plants. For this, we used a randomized block design with four treatments and six replications. The treatments consisted of two rootstocks (“Maxifort” and “Multifort”), self-grafted (“Alambra” in “Alambra”), and ungrafted (“Alambra”). Each plot consisted of 20 plants, out of which the 14 central plants were evaluated. There was no significant effect on yield and fruit quality. In the assessment of nutritional status, there were no differences in the levels of P, Mg, and Ca in grafted plants. Therefore, the rootstocks Maxifort and Multifort, grown under conditions in which the experiment was conducted, did not increase the production and quality of fruits.

RESUMO Sob condições controladas em câmara tipo BOD, oito linhagens de alface crespa e a cultivar Solaris, foram avaliadas por meio de um índice de latência (IL) como medida da severidade do míldio, e a resposta de resistência por meio da porcentagem de plântulas com esporângios (PE), quando inoculadas com nove raças de Bremia lactucae isoladamente e com a única mistura de todas as raças. O IL e a PE nas linhagens foram inferiores aos apresentados na cultivar Solaris utilizada como padrão de suscetibilidade. As linhagens L1, L2, L3 e L4, foram altamente resistentes quando inoculadas (PE=0,0%) com às nove raças/mistura, as linhagens L5, L6, L7 e L8, dependendo da raça/mistura inoculada apresentaram alto nível de resistência (PE=0-4,6%), resistência incompleta (PE=6,0-15,1%), e a linhagem L5 apresentou reação heterogênea de resistência e suscetibilidade à raça SPBl:07 (PE=27,9% ).

ABSTRACT Under controlled conditions in a BOD chamber, eight lines of green leaf lettuce and the cultivar Solaris were evaluated by means of a latency index (IL) as a measure of downy mildew severity, while the resistance response was assessed based on the percentage of seedlings with sporangia (PE) when inoculated with nine races of Bremia lactucae alone and with one single mixture of all races. The IL and PE for the lines were inferior to those shown for the cultivar Solaris, used as the susceptibility standard. The lines L1, L2, L3 and L4 were highly resistant when inoculated (PE = 0.0%) with the nine races/mixture; the lines L5, L6, L7 and L8, depending on the inoculated race/mixture, showed high resistance level (PE = 0-4.6%) and incomplete resistance (PE = 6.0-15.1%), and the line L5 presented a heterogeneous resistance and susceptibility reaction to race SPBl:07 (PE = 27.9%).

RESUMO: Com o objetivo de avaliar o controle genético da resistência do melão ‘Gaúcho Redondo’ ao nematoide de galha Meloidogyne incognita, foi conduzido um experimento em blocos casualizados com três blocos e seis tratamentos, os quais envolveram as linhas parentais ‘Gaúcho Redondo’ (P1, resistente) e JAB 20 (P2, suscetível), assim como as gerações F1, F2, e retrocruzamentos (RC1P1 e RC1P2). Avaliaram-se plantas individuais após 70 dias da inoculação com o patógeno, por meio do fator de reprodução do nematoide (FR). A hipótese de herança monogênica foi rejeitada pelo teste do qui-quadrado (χ2), indicando que a resistência está sob controle de mais de um loci gênico, sendo confirmado pela análise quantitativa, que evidenciou a presença de seis genes.

ABSTRACT: In order to assess the genetic control of resistance in the melon ‘Gaúcho Redondo’ to the root-knot nematode Meloidogyne incognita, an experiment was conducted in a randomized complete block design with three blocks and six treatments using the parental lines ‘Gaúcho Redondo’ (P1 resistant) and JAB 20 (P2 susceptible), as well as F1, F2, and backcross generations (RC1P1 and RC1P2). Seventy days after inoculation, individual plants were evaluated for resistance using the nematode reproduction factor (RF). The hypothesis of monogenic inheritance was rejected by the chi-square test (χ2), and results indicated that resistance is controlled by more than one gene locus, as confirmed by the quantitative analysis that revealed the presence of six genes.