Crimson Sweet Research Articles

Comparison of Several Watermelon (Citrullus lanatus Thunb.) Hybrids in Republic of Macedonia

Watermelon is a traditionally grown vegetable in the Republic of Macedonia. Numerous varieties and hybrids of watermelon are registered in the National Variety List. Prior to their introduction into commercial production, all foreign hybrids and newly created varieties are examined in order to determine their stages of growth, yield and characteristic of fruit. The experiment was set on experimental plots in the Institute of Agriculture in Skopje. In the years between 2005 and 2009, the following 21 varieties and hybrids of watermelon were observed: Romanza F1, Bambolino F1, Bonta F1, Scherezada in 2005; Pauline F1, Nelson F1, Joker F1, Carmen F1 in 2006; Lady F1, Trophy F1, Fletta F1, Marabella F1, Super Crimson Sweet OP, Fantasy F1 in 2007; Crimson Ruby F1, Biblos F1, Pegasus F1, Megan F1 in 2008; Colosseo F1, Caravan F1, Montana F1 in 2009. The Crimson Sweet was used as a standard variety. In 2005, Bambolino F1 gave higher yield (59.7t/ha) than the standard variety (31.42t/ha). In 2006, Nelson F1 exceeded significantly higher yield by giving 65,8 t/ha in comparison to standard variety 46.3 t/ha. In 2007 all examined varieties gave better results than the standard variety. In 2008 Crimson Ruby F1 gave higher yield (42.7 t/ha) than the standard variety (36.8t/ha). In 2009 Montana F1 was more yielded (67.5 t/ha) then the standard variety (62.2 t/ha). All examined varieties and hybrids gave stable characteristics and were registered in the National Variety List for commercial production.

Molecular characterization of watermelon cultivars using microsatellite markers

Allelic patterns and genetic similarity among 17 watermelon cultivars were established using microsatellite markers. For visualization of the genetic similarity, the dendrogram UPGMA (Unweighted Pair Group Method with Arithmetic Means) was generated by the similarity matrix of the Jacquard coefficient, based on 34 alleles of ten microsatellite loci. Total DNA was extracted by the CTAB 2x method and PCR (Polymerase Chain Reaction) products were analyzed in denaturing polyacrylamide 6% gels, stained with silver nitrate. The number of base pairs was estimated by the method of inverse mobility, based on known size product regression. Similarity ranged from 34 to 100%, reflecting high genetic variability. Analyzed loci were not enough to distinguish all 17 watermelon cultivars. The pairs 'Sugar Baby' and 'Omaru Yamato', 'Charleston Gray' and 'Sunshade', 'Crimson Sweet' and 'Nova Crimson' presented 100% of similarity. In dendrogram two groups were observed at 0.42 similarity cut point, with Citrullus colocynthis, positioned as an out group. One watermelon group was formed predominantly by cultivars derived from 'Crimson' and another group was formed by cultivars of different types such as 'Sugar Baby', 'Charleston Gray' and 'Pérola'. Allele pattern and base pair (bp) estimates for the 34 alleles in the 10 microsatellite loci revealed in the present study are a first endeavor to use microsatellite markers in situations of cultivar protection for the watermelon agribusiness in Brazil. They can also be used in situations of commercial disputes regarding certification of the main watermelon cultivars used in the country.

Pollen Viability of F1 Hybrids between Watermelon Cultivars and Disease-resistant, Infraspecific Crop Wild Relatives

Crop wild relatives (CWRs) are important sources of variation for domesticated crops like watermelon (Citrullus lanatus) where cultivated varieties have a very narrow genetic base. The use of CWRs in plant breeding can be hampered by low fertility, chromosomal rearrangements, marker distortion, and linkage drag in the progeny. Pollen viability can be a quick and easy way to estimate male fertility, which can be a cause of marker distortion and an indicator of chromosomal rearrangements. Pollen viability was determined for F1 hybrids between cultivars and resistant citron and egusi types and the data were used to determine whether the parental cultivars/lines used or the directionality of the cross play a role in pollen viability. F1 hybrids between cultivars and the egusi type showed no reduction in pollen viability compared with parental lines, whereas pollen viability of hybrids with citron types varied between 61.8% and 91.7%. Significant main effects were observed for the cultivar and donor lines used, but the directionality of the cross did not affect pollen viability. F1 hybrids with ‘Crimson Sweet’ as the cultivar parent had significantly higher pollen viability than those with ‘Sugar Baby’ or ‘Charleston Gray’. Our results indicate that the directionality of the crosses between watermelon cultivars and infraspecific CWRs does not affect pollen viability but that the specific cultivars and donor lines used can have a significant effect. The high pollen viability of cultivar–egusi hybrids is supported by previous genetic data and strongly suggests that it should be easier to introgress traits from egusi types than citron types.

Mulching with Large Round Bales between Plastic-covered Beds Using a Newly Developed Offset Round-bale Unroller for Weed Control

Mulching between rows of plastic used for vegetable production can be an effective practice for controlling weeds. An existing round-bale unroller was modified to create an offset bale unroller, allowing round bales of hay to be unrolled between planting rows with a tractor. This modification has made the practice of mulching with round bales of hay or wheat straw more efficient. This offset round-bale unroller was used to apply hay and wheat straw mulch to between-row areas of ‘Crimson Sweet’ watermelon (Citrullus lanatus) in 2009 and 2010. Hay and wheat (Triticum sp.) straw mulches were applied at two thicknesses, corresponding one and two layers of mulch from the round bale, respectively. All of the hay and wheat straw mulch treatments controlled weeds significantly better than the non-treated controls in both years. There was a significant mulch-type by year interaction for weed control, with 1-year-old hay having less weed control in 2010 compared with 2009, whereas other mulches had improved weed control in 2010. One-year-old wheat straw and new hay had the lowest levels of weed biomass present compared with new wheat straw and the no-mulch control. Mulch thickness significantly affected weed control, with mulches applied in two layers having significantly less weed biomass than those applied in one layer. Weed pressure was significantly less in 2010 compared with 2009. The offset bail-unroller that has been developed to apply mulches to between-row areas of plastic-covered beds is a useful tool that can be used to efficiently unroll round bales of a variety of organic mulches for weed control.

Evaluation of watermelons texture using their vibration responses

Flesh texture quality is an important attribute for watermelons that can be used as a ripeness indicator for sorting fruits. A non-destructive method is employed here, based on vibrations response, to assess the consumer opinion about watermelon (Crimson Sweet) tissue. The responses of samples to vibration excitation were recorded by laser Doppler vibrometry (LDV). The amplitude and phase as two spectrums of frequency response function were extracted over a wide frequency range. Following non-destructive tests, the watermelons were sensory evaluated. The samples were graded in a range of ripeness by panel members in terms of texture acceptability. Stepwise multiple linear regression (SMLR) and partial least squares regression (PLSR) were applied to extracted vibration spectrums to construct prediction models of watermelon flesh quality. The results showed that performance of SMLR models on phase spectrum was better than others. The determination coefficients (R2) of the calibration and cross validation models were 0.9998 and 0.9986 respectively. This study demonstrated the feasibility of mentioned method for predicting the quality of watermelons in industrial grading systems.

Produção e qualidade da melancia submetida a adubação nitrogenada

Propôs-se, neste trabalho, avaliar o efeito da aplicação de diferentes doses de nitrogênio sobre a produção e qualidade de melancia 'Crimson Sweet'. Conduziu-se esta pesquisa na área experimental da Universidade Federal de Roraima, Boa Vista, RR, no período de janeiro a abril de 2010. O delineamento experimental utilizado foi o de blocos inteiramente casualizados, com 4 repetições. Os tratamentos consistiram de 5 níveis de nitrogênio (50, 100, 150, 200 e 250 kg ha-1 de N) aplicados na forma de ureia, de modo convencional. A produção comercial máxima obtida foi de 40.428 kg ha-1 com 144,76 kg ha-1 de N. Referente à qualidade dos frutos, o pH não foi influenciado pelos tratamentos, apresentando média de 5,34. A relação comprimento/diâmetro e a espessura da casca também não sofreram influência dos tratamentos enquanto a firmeza do fruto, o conteúdo de sólidos solúveis (SS), a acidez titulável (AT), o conteúdo de açúcares (redutores, não redutores e totais), o teor de ácido ascórbico e a relação SS/AT, foram influenciados pelos níveis de N.

Importance of cucurbits in the epidemiology of Papaya ringspot virus type P

Papaya ringspot virus type P (PRSV‐P) systemically infects Carica papaya and species belonging to the family Cucurbitaceae. Attempts to recover PRSV‐P from naturally infected cucurbit plants grown near or among diseased papaya trees have shown conflicting results worldwide. This study aimed to evaluate the natural infection of cucurbit species grown among and near papaya trees infected with PRSV‐P in Brazil. Natural infection of cucurbits with PRSV‐P occurred in zucchini squash but not in watermelon and cucumber. However, several attempts to recover PRSV‐P from numerous Cucurbita pepo cv. Caserta (zucchini squash) plants grown 5–80 m from diseased papaya trees in the field failed. Mechanical inoculations of Cucurbita pepo cv. Caserta, Cucurbita maxima cv. Exposição (pumpkin), Cucumis sativus cv. Primepack Plus (cucumber) and Citrullus lanatus cv. Crimson Sweet (watermelon) with five Brazilian PRSV‐P isolates showed that zucchini squash was the most susceptible species followed by watermelon and cucumber, while pumpkin was not infected. The results confirmed the variable susceptibility of cucurbit species to experimental and natural PRSV‐P infection. Given these facts, the control of the disease through roguing should focus mainly on diseased papaya plants, as has been practised successfully in Brazil for many years, and on those cucurbits particularly known to be susceptible to natural infection with PRSV‐P.

EVALUATION OF ROOTSTOCKS FOR WATERMELON GRAFTING WITH REFERENCE TO PLANT DEVELOPMENT, YIELD AND FRUIT QUALITY

The effect of grafting and post-grafting temperature on the plant development of two watermelon cultivars at transplantation and on subsequent fruit quality was studied. Watermelon cv. Sugar Baby and Crimson Sweet were self-rooted or grafted onto rootstock RS 841 F1 (Cucurbita maxima × C. moschata) or bottlegourd [Lagenaria siceraria f. clavata] (year 1), plus L. siceraria f. pyrotheca (year 2). After grafting, plants were held at 8 oC or 16 oC (minimum) until transplantation (28-29 days), at which stage growth was compared with that of the self-rooted control held under the same conditions. Plants were planted in the field and fruit quality assessed at harvest. At the time of transplantation in year 1, plants at 16 oC were taller and had a higher total fresh weight than those at 8 oC. The grafted plants of both cultivars were taller and had a higher leaf area and fresh weight than the self-rooted plants, irrespective of rootstock. In year 2, the grafted plants of both cultivars had better development (height, leaf area, leaf number, fresh weight) than self-rooted plants. The plants of Crimson Sweet × L. siceraria f. pyrotheca were taller than those of the other two scion-rootstock combinations, irrespective of temperature. Mean fruit weight at harvest was higher in grafted plants than in self-rooted plants, and sugar content varied with scion-rootstock combination. Grafting of watermelon results in better plant growth by the time of transplantation, whereas the scion-rootstock combination affects fruit quality. A minimum temperature of 16 oC is indicated during the post-grafting stage.

Germinação e vigor de sementes de melancia tratadas com zinco

O experimento foi conduzido com objetivo de avaliar os efeitos da aplicação de doses de zinco sobre a germinação e o vigor de sementes de melancia. Os tratamentos constaram da aplicação de sete doses de zinco (0; 0,19; 0,38; 0,76; 0,95; 1,14 e 1,52 g de Zn kg-1 de sementes), utilizando como fonte o ZnSO4.7H2O. Os efeitos da aplicação de Zn sobre as sementes e plântulas foram avaliados pelo teste de germinação (porcentagem de plântulas normais e anormais + sementes mortas), com quatro repetições, e por teste de vigor (comprimento, massa fresca e seca de plântulas), com cinco repetições, sob delineamento inteiramente casualizado. O tratamento de sementes de melancia, cv. Crimson Sweet com Zn, aumentou a germinação até a dose de máxima eficiência técnica, a qual foi de 0,95 g de Zn kg-1 de sementes. O tratamento de sementes de melancia com diferentes doses de Zn reduziu o vigor das sementes, quando avaliado pelo teste de comprimento e massa fresca e seca de plântulas.

Evapotranspiration and crop coefficient of drip irrigated watermelon in Piaui coastline, Brazil

The knowledge of the evapotranspiration (ETc) and crop coefficient (Kc) is fundamental to plan and to manage the irrigation of any crop. The aim of this study was to determine the daily and hourly evapotranspiration of drip irrigated watermelon (Citrullus Lanatus, var. Crimson Sweet) and crop coefficient (Kc) in each crop development phase. The experiment was carried out in an experimental area of 1.27 ha of Embrapa Mid-North, localized in Parnaíba (02°54'S, 41°47'W and 46 m above of sea), State of Piauí, Brazil, from September to November, 2006. Electronic weighing lysimeters of 1.5 m x 1.5 m wide and long and 1.0 m deep were used to obtain the evapotranspiration. The plants were drip irrigated with a lateral row per plant row and drippers spaced 0.5 m from each other. The reference evapotranspiration (ETo) was estimated using the Penman-Monteith equation from the climatic data obtained by electronic sensors. The total evapotranspiration during the watermelon crop cycle cultivated in the state of Piauí was 233.87 mm, with mean values of 3.7 mm day-1, minimum of 1.18 and maximum of 8.14 mm day-1. The Kc of the drip irrigated watermelon was 0.18 in the initial stage of crop growth; 0.18 to 1.3, in crop development stage; 1.3 in the intermediate stage and 0.43 in the final stage.

Inheritance of resistance to the Papaya ringspot virus-watermelon strain (PRSV-W) from watermelon accession 'PI 595201'

Two watermelon genotypes were used as parental in crosses designed to study the inheritance of resistance to PRSV-W: the cultivar Crimson Sweet (susceptible) and the accession 'PI 595201'(resistant). Plants of the generations P1, P2, F1, F2, BC11 e BC12 were inoculated with a Brazilian isolate of PRSV-W and were evaluated by recording symptoms. Genetic and phenotypic parameters of PRSV-W resistance were estimated and tests based on hypothesis of monogenic inheritance and maximum likelihood methods were performed. The additive component [a] of resistance was higher than the non-additive [d]. The estimates of the broad-sense heritability (0.80) and of narrow-sense heritability (0.67) indicated that the genetic variance was greater than the environmental, allowing higher genetic gains in selecting more resistant plants in segregating populations. The inheritance is more complex than a typical monogenic inheritance. The importance of the additive genetic effects in the expression of resistance to PRSV-W was evidenced.

Watermelon transformation with Zucchini yellow mosaic virus coat protein gene and comparison with parental cultivar

The objective of this work was to transfer Zucchini yellow mosaic virus coat protein (ZYMV-CP) and neomycin phosphotransferase II (NPT II) genes to the watermelon 'Crimson Sweet'(CS) genome, and to compare the transgenic progenies T1 and T2 with the nontransformed parental cultivar for morphological, pomological, growth and yield characteristics. The ZYMV-CP gene was transferred by Agrobacterium tumefaciens. The presence of the gene in transgenic T0, T1 and T2 plants was determined by polymerase chain reaction, and the results were confirmed by Southern blot. Two experiments were performed, one in the winter-spring and the other in the summer-autumn. In both experiments, the hypocotyl length of transgenic seedlings was significantly higher than that of nontransgenic parental ones. In the second experiment, the differences between transgenic and nontransgenic individuals were significant concerning fruit rind thickness, flesh firmness, fruit peduncle length, size of pistil scar, and a* values for fruit stripe or flesh color. Transferring ZYMV-CP gene to CS genome affected only a few characteristics from the 80 evaluated ones. The changes in rind thickness, flesh firmness and flesh color a* values are favorable, while the increase in the size of pistil scar is undesirable. The transgenic watermelon line having ZYMV-CP gene and the parental cultivar CS are very similar.

Identification of Citrullus lanatus Germplasm Accessions Tolerant to Clomazone Herbicide

Clomazone herbicide is registered for use in watermelon; however, crop tolerance is marginal, and the recommended use rates (0.17 to 0.28 kg a.i./ha) are lower for watermelon than for other crops. In a greenhouse germplasm evaluation experiment including 56 germplasm accessions and watermelon cultivars, three Citrullus lanatus var. citroides PI accessions (PI 482324, PI 5003540, and PI 532624) were not injured by clomazone, whereas most of the other accessions and cultivars were moderately or severely injured. A greenhouse concentration response experiment demonstrated that the clomazone concentration required to cause moderate injury to the tolerant ‘PI 500354’ was approximately three times the concentration required to cause similar injury to the susceptible citroides accession ‘PI 244017’, and the concentration required to cause 50% shoot biomass reduction was approximately five times greater for ‘PI 500354’ than for ‘Charleston Gray’ watermelon. Subsequent field experiments demonstrated that two tolerant accessions (‘PI 500354’ and ‘PI 482324’) were injured less initially by clomazone and recovered more rapidly from clomazone injury than two susceptible accessions (‘PI 244017’ and ‘PI 271773’) and two watermelon cultivars (‘Charleston Gray’ and ‘Crimson Sweet’). Tolerant germplasm accessions like ‘PI 482324’ and ‘PI 500354’ may be useful as sources of clomazone tolerance in watermelon breeding. Chemical name used: clomazone {2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone}.

An Extended Genetic Linkage Map for Watermelon Based on a Testcross and a BC<sub>2</sub>F<sub>2</sub> Population

There is limited genetic mapping data useful for breeding programs of watermelon. Introgression lines should be a use-ful tool for genetic studies and genetic enhancement of watermelon cultivars. In this study, we used an advanced re-combinant population (BC2F2) to identify and map chromosomal segments of the wild watermelon Citrullus lanatus var. citroides that were incorporated in the genome of the watermelon cultivar Crimson Sweet (Citrullus lanatus var. lana-tus). An advanced recombinant population (BC2F2) was constructed using a United States Plant Introduction (PI) 494817 (C. lanatus var. citroides) (known to have moderate resistance to bacterial fruit blotch) as a donor parent, and the elite watermelon cultivar Crimson Sweet (C. lanatus var. lanatus) as the recurrent parent. The genetic linkage map consists of 272 markers, including 89 sequence-related amplified polymorphism (SRAP), 72 targeted region amplifica-tion polymorphism (TRAP), and 111 high frequency oligonucleotide-targeting active gene (HFO-TAG) markers. The 272 markers were assembled into 51 linkage groups, covering a total genetic distance of 2162 cM, with an average genetic distance of 7.9 cM between markers. Also, we expended the genetic linkage map for watermelon derived from a testcross population {Griffin 14113 [C. lanatus var. citroide (L.H. Bailey) Mansf.] x watermelon cultivar New Hamp-shire Midget (C. lanatus var. lanatus)} x PI 386015 [C. colocynthis (L.) Schrad.]. The genetic linkage map based on the test cross population consists of 558 markers that cover a genetic distance of 2760.8 cM. This linkage map consists of 41 linkage group, including 10 large linkage groups (ranging from102-240 cM), nine intermediate size linkage groups (ranging from 62-93 cM), and 22 small linkage groups (ranging from 2-56 cM). Comparative mapping between these two linkage maps identified high consensus in 25 HFO-TAG markers and one TRAP marker that represent 8 linkage groups in the BC2F2 population and 9 linkage groups in the testcross population. These results indicate that HFO-TAG markers should be useful in comparative mapping. The extended genetic maps and the genetic population in this study should be useful in breeding programs using marker assisted selection and should serve as a platform for further de-velopment of introgression lines for watermelon.

Bioactive compounds and antioxidant activities of different watermelon ( Citrullus lanatus (Thunb.) Mansfeld) cultivars as affected by fruit sampling area

This investigation reports the variability of antioxidant components and antioxidant activities of six watermelon cultivars (cvs) (four commercial cvs Aramis, Crimson Sweet, Dumara, Giza, and two new selections P503 and P403 produced by the National Agricultural Research Institute of Tunisia) as influenced by sampling area. All cvs were simultaneously grown in an open-field and subjected to identical horticultural practices in order to minimize the effects of environmental conditions and maximize those related to genotype. Significant differences were found between watermelon cvs for lycopene, phenolics, flavonoids, ascorbic acid (AsA), dehydroascorbic acid (DHA) and total vitamin C (AsA + DHA) contents, as well as in the antioxidant activity of their hydrophilic and lipophilic fractions. P503 cv showed the highest lycopene and flavonoid contents. Crimson Sweet and Giza cvs showed the highest HAA and LAA when TEAC was used as assay method, while the highest HAA and LAA were detected in Giza and Dumara cvs and in P503 cv, respectively, when FRAP assay was used. This study demonstrates that the amount of each specific antioxidant, as well as the HAA and LAA, were both influenced by genotype and sampling area, emphasizing the need to evaluate watermelon biodiversity in order to improve its nutritional value.

Temporal and spatial dynamics of watermelon gummy stem blight epidemics

The effect of the distance of initial inoculum on the intensity of watermelon gummy stem blight, caused by Didymella bryoniae, was studied in a naturally-infected rainfed commercial field. The shorter the distance from the focus, the sooner was disease onset and the earlier maximum disease levels were achieved. Maximum disease incidences were reached earlier than maximum severities, but eventually destructive levels were observed for both disease incidence and severity. Disease progressed at similar rates, irrespective of the radial distance from the focus. A detailed study of the disease temporal progress was conducted in inoculated rainfed experimental fields with commercial genotypes Crimson Sweet (susceptible, S) and Riviera (moderately resistant, R). The Gompertz model best described the disease progress curves, and estimated apparent infection rates were 0.049 and 0.020 respectively for S and R genotypes. In addition, spatial pattern studies were conducted during the dry season in overhead irrigated experimental plots, inoculated with point-source foci. Disease intensity gradients were better explained by the Exponential model than by the Power Law model. Gummy stem blight distribution was classified as aggregated by the Ordinary Runs procedure. Two different spatial autocorrelation methods (2DCorr and LCOR) revealed strong short distance spatial dependencies. Long distance positive correlations between quadrats were observed along with periods of higher progress rates. The dynamic patterns of the epidemics of gummy stem blight in watermelon described here are consistent with epidemics of polycyclic diseases with splash-dispersed spores.

High-frequency Oligonucleotides in Watermelon Expressed Sequenced Tag-unigenes Are Useful in Producing Polymorphic Polymerase Chain Reaction Markers among Watermelon Genotypes

In this study, we report a simple procedure for developing and using new types of polymerase chain reaction (PCR) primers, named “high-frequency oligonucleotides–targeting active genes” (HFO-TAG). The HFO-TAG primers were constructed by first using a “practical extraction and report language” script to identify oligonucleotides (8, 9, and 10 bases) that exist in high frequency in 4700 expressed sequence tag (EST)-unigenes of watermelon (Citrullus lanatus) fruit. This computer-based screening yielded 3162 oligonucleotides that exist 32 to 335 times in the 4700 EST-unigenes. Of these, 192 HFO-TAG primers (found 51 to 269 times in the 4700 EST-unigenes) were used to amplify genomic DNA of four closely related watermelon cultivars (Allsweet, Crimson Sweet, Charleston Gray, and Dixielee). The average number of DNA fragments produced by a single HFO-TAG primer among these four watermelon cultivars was considerably higher (an average of 5.74 bands per primer) than the number of fragments produced by intersimple sequence repeat (ISSR) or randomly amplified polymorphic DNA (RAPD) primers (an average of 2.32 or 4.15 bands per primer, respectively). The HFO-TAG primers produced a higher number of polymorphic fragments (an average of 1.77 polymorphic fragments per primer) compared with the ISSR and RAPD primers (an average of 0.89 and 0.47 polymorphic fragments per primer, respectively). Amplification of genomic DNA from 12 watermelon cultivars and two U.S. Plant Introductions with the HFO-TAG primers produced a significantly higher number of fragments than RAPD primers. Also, in PCR experiments examining the ability of primers to amplify fragments from a watermelon cDNA library, the HFO-TAG primers produced considerably more fragments (an average of 6.44 fragments per primer) compared with ISSR and RAPD primers (an average of 3.59 and 2.49 fragments per primer, respectively). These results indicate that the HFO-TAG primers should be more effective than ISSR or RAPD primers in targeting active gene loci. The extensive EST database available for a large number of plant and animal species should be a useful source for developing HFO-TAG primers that can be used in genetic mapping and phylogenic studies of important crop plants and animal species.

Avaliação de genótipos de melancia para resistência ao Papaya ringspot vírus, estirpe melancia

Verificou-se a eficiência de duas metodologias de avaliação em nove genótipos de melancia da resistência a três isolados de Papaya ringspot virus, estirpe melancia (PRSV-W), de três regiões brasileiras. O delineamento do experimento foi em blocos casualizados com quatro repetições. Cada parcela foi composta de um vaso com 5 kg de substrato com cinco plantas de melancia por vaso. Aos 10 e 13 dias após a semeadura, três isolados do PRSV-W coletados nos estados de Goiás, Pernambuco e São Paulo, foram inoculados mecanicamente. Aos 27 e 37 dias após a semeadura foram feitas avaliações visuais de sintomas de vírus. A confirmação da presença ou não do vírus nas plantas inoculadas foi feita através do teste sorológico Das-Elisa, utilizando anti-soro policlonal. Foram realizadas análises de variância, estimadas as herdabilidades, calculadas as correlações entre os caracteres, e efetuadas comparações das médias dos genótipos e dos diferentes inóculos. Pelo comportamento diferenciado dos genótipos em relação aos isolados avaliados, conclui-se que isolados provenientes de diferentes regiões devem ser testados nos programas de melhoramento de melancia. Os altos valores de herdabilidade para a maioria dos caracteres indicam que a característica em estudo está sob o controle de poucos loci e que, portanto, a possibilidade de seleção de materiais resistentes é alta. Em geral, os genótipos mostraram um nível de tolerância superior ao da cultivar predominante no mercado brasileiro (Crimson Sweet). Portanto, podem servir de base para a produção de cultivares mais tolerantes ao PRSV-W.

First Report of Monosporascus cannonballus on Watermelon in Brazil.

In 2008 and 2009, vine decline symptoms were observed in three watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) fields located in the municipalities of Mossoró (Rio Grande do Norte State) and Quixeré (Ceará State) in northeastern Brazil. Symptoms included yellowing of crown leaves just prior to harvest and collapse of many of the vines. Mean maximum daily temperatures for the first and second half of the season were 28.6 and 25.1°C, respectively. Affected plants exhibited necrotic root systems and lacked most of the secondary and tertiary feeder roots. Numerous perithecia on the roots contained asci and ascospores characteristics of Monosporascus cannonballus Pollack & Uecker (1,2). Small pieces of primary and secondary roots were surface disinfected and plated onto potato dextrose agar (PDA) medium with 0.5 g liter-1 of streptomycin sulfate and incubated for 7 days at 25°C in the dark. Hyphal tips from all colonies were transferred to PDA and further incubated for 30 to 40 days at 25°C in the dark for subsequent growth and sporulation. Isolations consistently yielded colonies of white mycelium, which became dark grayish after 10 to 15 days, and perithecia with one-spored asci. The internal transcribed spacer regions of ribosomal DNA of isolates 18-5 and 19-1 were sequenced (GenBank Accession Nos. GQ891544 and GQ891545). These sequences were identical to sequences of M. cannonballus (GenBank Accession Nos. AM167936 and AM167937). Pathogenicity of these two isolates was confirmed on watermelon cv. Crimson Sweet in a greenhouse maintained at 25 to 30°C. Inoculum was produced in a sand-oat hulls (Avena sativa) medium (0.5 liter of sand, 46 g of ground oat hulls, and 37.5 ml of distilled water) and incubated at 25°C for 1 month. CFU were quantified by serial dilution using 1% hydroxyethyl cellulose. A sterilized mixture of equal portions (vol/vol) of sand and peat moss was used to fill 17-cm-diameter plastic pots and inoculum was added to produce an inoculum concentration of 20 CFU g-1. Five watermelon seeds planted in each pot were later thinned to one seedling per pot. There were five replicated pots for each treatment with an equal number of noninfested pots. Plants were evaluated for disease 45 days after sowing. All isolates of M. cannonballus were highly aggressive and caused severe root necrosis compared with the noninoculated controls. M. cannonballus was reisolated from symptomatic plants, confirming Koch's postulates. In 2004, M. cannonballus was reported in the same Brazilian cucurbit-growing areas causing root rot and vine decline of muskmelon (Cucumis melo L.) (3), but to our knowledge, this is the first report of M. cannonballus on watermelon in Brazil.

Plantio irrigado de bananeiras resistentes à Sigatoka-negra consorciado com culturas anuais

Com o objetivo de avaliar o plantio irrigado de bananeiras resistentes à Sigatoka-negra consorciado com cultura anuais, na região norte de Minas Gerais, um experimento foi instalado na Fazenda Experimental do Departamento de Ciências Agrárias da Universidade Estadual de Montes Claros, Câmpus de Janaúba-MG. O experimento foi conduzido no período de abril de 2006 a julho de 2007, delineado em blocos casualizados, segundo um esquema de parcelas subdivididas 3 x 5, tendo na parcela as três variedades de bananeiras: Pacovan Ken, Caipira e Thap Maeo, e na subparcela quatro culturas intercalares: Feijão-Pérola, Quiabo-Dardo, Melancia-Crimson-Sweet e Feijão-Caupi, e a testemunha (sem cultura intercalar), com três repetições. Ao todo, foram 756 bananeiras, em 45 parcelas, com 6 plantas úteis cada, constituindo a cultura principal. As culturas intercalares ocuparam as entrelinhas da bananeira, tanto aquelas com as linhas de irrigação como sem linha de irrigação. O plantio da bananeira e das culturas intercalares foi feito no mesmo período, utilizando-se do espaçamento de 3,0 m entre as linhas e 2,0 m entre as covas de bananeira, com microaspersores espaçados de 6 m. Avaliaram-se as características vegetativas e reprodutivas das variedades de bananeiras, no primeiro ciclo. Não foi observado efeito significativo dos cultivos intercalares sobre as variedades de bananeiras, com exceção do número de dias do plantio ao florescimento e do número de dias do plantio à colheita das variedades de bananeiras. O uso do feijão-caupi promoveu atraso no ciclo de produção das três variedades de bananeiras Pacovan Ken, Caipira e Thap Maeo.