ABSTRACT Monosporascus root rot and vine decline (MRRVD) is an important disease in the melon crop in Brazil. In our research, we evaluated the reaction of 45 melon genotypes to M. cannonballus in two successive cropping seasons in a greenhouse. Melon seedlings were transplanted into naturally infested soil. The evaluation of the genotypes was performed after 55 days, using a score scale to group each genotype into one of five classes and to calculate the disease severity index. None of the genotypes showed an immune reaction to M. cannonballus, regardless of the season. In the first cycle, only 28.9% ('AF 464', 'Auraprince', 'DRG 2278', 'Estoril', 'Guaporé', 'Kousto', 'Mabel', 'Magisto', 'Massaï', 'Nectar', '8530', 'RZ 34130' and 'RZ 34292') had a similar reaction to the high resistance to the MRRVD. Most genotypes (66.7%) behaved as moderately resistant while 4.4% were susceptible and none were highly susceptible. Conversely, in the second cycle, no genotype showed a reaction similar to high resistance while 42.2% behaved as moderately resistant, 48.9% as susceptible, and 8.9% as highly susceptible. The severity levels ranged from 7.5 to 60% and 27.5 to 92.5% for the first and second cycles, respectively. The genotypes 'DRG 2278', 'Estoril', 'Guaporé', 'Kousto', 'Mabel', 'Massaï', 'RZ 34130' and 'RZ 34292' were identified as highly resistant and moderately resistant in the first and second cycles of cultivation, respectively. Therefore, these genotypes are promising sources of resistance to M. cannonballus and should be preferred in commercial fields infested with the pathogen. | RESUMO A Podridão de raízes por Monosporascus e declínio de ramas (PRMDR) é uma importante doença em meloeiro no Brasil. Nesta pesquisa, foi analisada a reação de 45 genótipos de meloeiro a M. cannonballus em dois ciclos de cultivo sucessivos em casa de vegetação. Mudas de meloeiro foram transplantadas em solo naturalmente infestado. A avaliação dos genótipos foi realizada após 55 dias, com o auxílio de escala de notas para agrupamento de cada genótipo em cinco classes e cálculo do índice de severidade da doença. Nenhum dos genótipos apresentou reação de imunidade a M. cannonballus. No primeiro ciclo de cultivo, somente 28,9% (‘AF 464’, ‘Auraprince’, ‘DRG 2278’, ‘Estoril’, ‘Guaporé’, ‘Kousto’, ‘Mabel’, ‘Magisto’, ‘Massaï’, ‘Néctar’, ‘8530’, ‘RZ 34130’ e ‘RZ 34292’) apresentaram reação semelhante à alta resistência a PRMDR. A maioria dos genótipos (66,7%) se comportou como medianamente resistente, enquanto 4,4% como suscetível e nenhum como altamente suscetível. No segundo ciclo de cultivo, nenhum genótipo apresentou reação semelhante à alta resistência, enquanto 42,2% se comportaram como medianamente resistentes, 48,9% como suscetíveis e 8,9% como altamente suscetíveis. Os níveis de severidade variaram entre 7,5 a 60% para o primeiro ciclo de cultivo e entre 27,5 a 92,5% para o segundo ciclo. Os genótipos ‘DRG 2278’, ‘Estoril’, ‘Guaporé’, ‘Kousto’, ‘Mabel’, ‘Massaï’, ‘RZ 34130’ e ‘RZ 34292’ foram identificadas como altamente resistentes e medianamente resistentes, no primeiro e segundo ciclos de cultivo, respectivamente. Estes genótipos constituem fontes promissoras de resistência a M. cannonballus e devem ser preferidos em campos comerciais infestados pelo patógeno.

ABSTRACT: The downy mildew, caused by the fungus Pseudoperonospora cubensis is a major foliar disease that attacks the melon crop in the rainy season in northeastern Brazil. The objective of this study was to identify and characterize morphologically resistant melon accessions to P. cubensis. Thirty-six accessions and four commercial cultivars were evaluated in a randomized block design with three replications. The plot was composed of seven plants. The evaluation was conducted in the under field conditions with a diagrammatic scale and calculating the disease percentage index (DPI). Resistance sources and references genotypes were characterized morphologically. The accessions C-RN-2, C-SE-2, C-CE-2, C-PE-2, C-PI-1, and C-BA-2 show resistance to P. cubensis and are promising for use in programs breeding for resistance to downy mildew although its fruits have reduced commercial quality. | RESUMO: O míldio, causado pelo fungo Pseudoperonospora cubensis é uma das principais doenças foliares que acometem a cultura do meloeiro no período chuvoso da região Nordeste brasileira. O objetivo do presente trabalho foi identificar e caracterizar morfologicamente fontes de resistência de meloeiro a P. cubensis. Trinta e seis acessos e quatro cultivares comerciais foram avaliados em delineamento em blocos casualizados com três repetições. A unidade experimental foi composta por sete plantas. E a avaliação realizada em condições de campo com uma escala diagramática, a qual fora calculado o índice de porcentagem da doença (IPD). As fontes de resistência e genótipos referências foram caracterizadas morfologicamente. Os acessos C-RN-2, C-SE-2, C-CE-2, C-PE-2, C-PI-1 e C-BA-2 apresentam resistência a P. cubensis e são promissores para uso em programas de melhoramento visando resistência ao míldio do meloeiro, embora os seus frutos tenham reduzida qualidade comercial.

RESUMO A adequada relação no fornecimento de nitrogênio (N) e potássio (K) para cada estádio fenológico do meloeiro é fundamental para seu crescimento e desenvolvimento, com maximização da partição de massa seca entre as partes vegetativas e reprodutivas. O objetivo deste trabalho foi avaliar a influência de concentrações de N e K para duas fases fenológicas (vegetativa e reprodutiva) do meloeiro e obter a melhor relação N:K para cada uma delas. Na primeira fase, foram avaliadas quatro concentrações de N (8, 11, 14 e 17 mmol L-1) e duas concentrações de K (4 e 5 mmol L-1), em delineamento experimental de blocos ao acaso, em esquema fatorial 4x2, com cinco repetições. Na segunda fase, em esquema fatorial 2x2, foram avaliadas as combinações das duas concentrações de N que geraram as melhores características na fase anterior e duas concentrações de K (4,5 e 9,0 mmol L-1). O aumento da concentração de N na fase vegetativa promoveu o aumento dos teores foliares de N, P e S e a redução de K, Ca e Mg. Além disso, aumentou o número de folhas, a altura da planta (tutorada verticalmente) e a área foliar. Por isso, 17:5 mmol L-1 foi considerada como melhor relação N:K para a fase vegetativa. Na segunda fase, não houve efeito das concentrações de N e de K sobre a área foliar, produtividade e a qualidade dos frutos do meloeiro e, assim, considerou-se 14:4,5 mmol L-1 como a melhor relação N:K para a fase reprodutiva. | ABSTRACT The adequate ratio in the supply of nitrogen (N) and potassium (K) for each phenological growth stage of melon is fundamental for its growth and development with the maximization of the dry mass partition between the vegetative and reproductive parts. The objective of this study was to evaluate the influence of N and K concentrations in two phenological growth stages (vegetative and reproductive stage) of melon and obtain the best N:K ratio for each one. In the first stage, four concentrations of N (8, 11, 14 and 17 mmol L-1) and two concentrations of K (4 and 5 mmol L-1) were evaluated in a randomized block design in a 4 × 2 factorial scheme with five replicates. In the second stage, in a 2 × 2 factorial scheme, the combinations of the two concentrations of N that generated the best characteristics in the previous stage and two concentrations of K (4.5 and 9.0 mmol L-1) were evaluated. The increase of the N concentration in the vegetative stage promoted the increase of the N, P and S content of leaves and the reduction of K, Ca and Mg. Moreover, it increased the number of leaves, the height of the plant (vertically tutored) and the leaf area. Therefore, 17:5 mmol L-1 was considered as the best N:K ratio for the vegetative stage. In the second stage, there was no effect of N and K concentrations on leaf area, yield and fruit quality. So, 14:4.5 mmol L-1 was considered as the best N:K ratio for the reproductive stage.

ABSTRACT This study evaluates the agronomic and environmental performance of yellow melons produced in an experimental area in Rio Grande do Norte, Brazil, using conventional methods and alternative systems of cultivation based on the rotation of melons with green manure crops. Two types of alternative management systems were evaluated, spanning twelve treatments: i) tillage, with the incorporation of the green manure biomass into the soil via the subsequent planting of melons into that residue, and ii) no tillage, with the maintenance of the biomass on the soil surface with subsequent planting of melons. Agronomic performance was evaluated by statistical analysis of productivity, while environmental performance was evaluated by analyzing the carbon footprint, according to ISO 14067. Agronomic analysis showed that rotation of melons with maize and Brachiaria resulted in a higher yield of melons for export. Assessment of the carbon footprint of this system in relation to the conventional system showed that the rotation system presented a lower carbon footprint. A scenario analysis showed that the carbon footprint can be further reduced by 42.54%, if: i) production takes place in areas already cultivated for more than 20 years, ii) the amount of inorganic nitrogen applied is reduced by 50%, and iii) commercialization of melons begins in the United States. This study shows the importance of rotating melons with green manure crops to increase production in the semiarid region and reduce the carbon footprint of this fruit. | RESUMO Esse estudo realiza avaliações agronômica e ambiental do melão amarelo, produzido em área experimental no Rio Grande do Norte, Brasil, em sistemas convencional e alternativo de cultivo baseado na rotação do melão. Dois tipos de manejo no sistema alternativo foram avaliados, considerando doze tratamentos com adubos verdes: i) incorporação ao solo da biomassa vegetal do adubo verde, e ii) manutenção dessa biomassa sobre o solo com posterior plantio do melão sobre a palhada. A avaliação agronômica baseou-se em análise estatística da produtividade, enquanto a ambiental, na análise da pegada de carbono, de acordo com a ISO 14067. A análise agronômica mostrou que a rotação de melão com milho e braquiária, obteve maior produtividade de melões tipo exportação. A avaliação da pegada de carbono dos sistemas mostrou que o sistema com rotação i) obteve a menor pegada de carbono quando comparado ao tratamento de referência. O estudo de cenários mostrou que a pegada pode ser reduzida em 42,54%, se: i) a produção ocorra em áreas já cultivadas a mais de 20 anos, ii) a quantidade de nitrogênio inorgânico aplicado seja reduzida em 50%, iii) e o melão passe a ser comercializado nos Estados Unidos. Esse trabalho mostra a importância de rotação do melão com adubos verdes para aumento da produção em região semiárida e redução da pegada de carbono.

ABSTRACT Macrophomina (Botryosphaeriaceae) is one of the main genera of soilborne phytopathogenic fungi, which causes root and seed rot in more than 800 host plants worldwide. Recent phylogenetic studies identified the species M. phaseolina and M. pseudophaseolina in Trianthema portulacastrum and Boerhavia diffusa in melon and watermelon production areas in northeastern Brazil. Therefore, the objective of this study was: i) to verify the effect of temperature and salinity on the mycelial growth of M. phaseolina, M. pseudophaseolina and M. euphorbiicola, ii) to assess their pathogenicity on melon and watermelon seedlings, and iii) to determine their sensitivity to the fungicide carbendazim. The optimal temperature for mycelial growth rate (MGR) for Macrophomina spp. ranged from 27.18 ºC (CMM4771 – M. pseudophaseolina) to 31.80 ºC (CMM4763 – M. phaseolina). For the effect of salinity on mycelial growth of Macrophomina isolates, the EC50 ranged from 103.76 (CMM4868 – M. euphorbiicola) to 315.25 mM (CMM4801 – M. pseudophaseolina). The pathogenicity test demonstrated that M. phaseolina, M. pseudophaseolina and M. euphorbiicola are pathogenic on melon with M. phaseolina exhibiting a higher level of virulence. Macrophomina euphorbiicola isolates did not cause disease in watermelon. The most sensitive isolates to the fungicide carbendazim were CMM4868, CMM4867 (M. euphorbiicola) and CMM1531 (M. phaseolina) with EC50 of 0.003, 0.012 and 0.012 mg.L-1 a.i., respectively. All Macrophomina spp. used in these experiments were pathogenic to the tested melon and watermelon cultivars with the exception of the M. euphorbiicola isolate that did not cause damage to watermelon.

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.

ABSTRACT Previous investigations showed that diverse varieties of melon may have different attractiveness for bees. Therefore, the objective of this study was to evaluate the composition, frequency and behavior of flower visitors of some melon (Cucumis melo) cultivars (Amarelo, Pele de Sapo, Cantaloupe, Gália) in different conditions (conventional and organic farming, dry and rainy seasons, with and without mulching and introduction or not of honey bee hives) in the main production poles in the Brazilian Northeast (Petrolina-PE/Juazeiro-BA, Pacajus-CE and Mossoro-RN). Observations and collections of flower visitors occurred from 5p.m. to 6p.m, in non-consecutive days. We recorded 12 species of insects, mostly bees. The most frequent was Apis mellifera (99.68%), but other species appeared sporadically (less than 0.5%): Xylocopa grisescens, Trigona spinipes, Plebeia sp., Melipona mandacaia, Frieseomelitta doedereleini, Halicitidae. Apis mellifera was present in all studied cultivars and sites. Xylocopa grisescens appeared in two poles, but not in Pacajus-CE, Amarelo cultivar. In addition, Trigona spinipes, although present in the three poles, was not recorded on Pele de Sapo. The Amarelo cultivar, under organic farming, without the use of mulching, and presence of honey bee hives, in the Petrolina-PE/Juazeiro-BA pole, in the dry season, was the combination of factors showing the largest number of Apis mellifera as the main visitor of melon flowers.