Crimson Sweet Research Articles

Inclusion of plant growth regulators into priming solution improves low-temperature germination and emergence of watermelon seeds

The effects of incorporating plant growth regulators into the priming solution on low temperature germination and emergence performance of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai. cv. Crimson Sweet] seeds were investigated. Seeds were primed in 2.5% (0.25 M) KNO3 solution for 6 d at 25°C in darkness containing one of the following: 1, 3 or 5 µM methyl jasmonate (MeJA), or 1, 3 or 5 mM spermine. Following priming, seeds were subjected to germination and emergence tests at 15°C. Priming watermelon seeds in the presence or absence of plant growth regulators significantly improved germination percentage and rate at 15°C compared to untreated seeds, which failed to germinate. Seeds primed in KNO3 solution containing 1 or 3 µM of MeJA had significantly higher germination percentages, 96 and 85%, respectively, compared to seeds primed in KNO3 only (69%). Germination rate and synchrony were improved by 1 and 3 µM of MeJA added to the priming solution. Emergence was enhanced by priming seeds in the presence of 1 µM (75%) and 3 µM (63%) MeJA compared to seeds primed in KNO3 solution, (35%) while non-primed seeds were unable to emerge at 15°C. Inclusion of spermine at all three concentrations into the priming solution did not significantly improve germination and emergence characteristics of watermelon seeds compared to seeds that were primed in KNO3 solution only. Therefore, priming watermelon seeds in 1 or 3 µM of MeJA incorporated into the KNO3 solution can be used as an effective method to improve low temperature performance of watermelon seeds. Key words: Watermelon, methyl jasmonate, polyamines, germination, emergence.

Levantamento preliminar de raças de Sphaerotheca fuliginea no Brasil

Sphaerotheca fuliginea é o agente causal do oídio, uma das principais doenças do meloeiro (Cucumis melo) e de outras cucurbitáceas no Brasil. O controle é feito principalmente pelo uso de fungicidas, mas o uso de cultivares resistentes pode ser uma opção dentro de um programa de manejo da doença. Este fungo apresenta especificidade fisiológica em melão, sendo a raça 1aparentemente a predominante no Brasil e no mundo. O conhecimento das raças prevalecentes em determinada região é de vital importância para os melhoristas. Neste trabalho, 31 isolados foram obtidos de diversas espécies de cucurbitáceas, provenientes de diferentes estados do Brasil. Todos os isolados foram identificados como S. fuliginea. Os isolados foram multiplicados em casa-de-vegetação e avaliados quanto à virulência em uma série de cultivares diferenciadoras de melão, uma cultivar de melancia, uma de pepino e uma linhagem de abóbora. Vinte e um dos 31 isolados foram identificados como raça 1 e oito como raça 2. Os dois isolados obtidos de melancia mostraram-se específicos à mesma pois só infectaram a cultivar desta espécie. Os resultados confirmam que a raça 1 é a predominante no Brasil. A raça 2 também está presente no DF, apesar de parecer estar adaptada apenas às condições de cultivo protegido, pois os oito isolados desta raça foram obtidos de melão, pepino e abóbora cultivados em estufa ou casa-de-vegetação. Este é o primeiro relato da raça 2 de S. fuliginea no Distrito Federal.

Activation of Isopentenyl Transfarese (ipt) Gene in Transformed Watermelon Influences Seed Number and Other Characteristics

The watermelon cv. Crimson Sweet was transformed with the copper inducible isopentenyl transferase, the rate-limiting step in cytokinin biosynthesis, gene via Agrobacterium tumafaciences (LBA4404). Transformed (ipt) and nontransformed plants were regenerated from tissue culture and clonally propagated by the rooting of leaf node cuttings. Twelve plants of each were grown in 1-gal. pots. Once the plants initiated new growth both transgenic plants and wild type plants were sprayed with one of four different concentrations (0, 5, 10, & 50 μm) of CuSO4. The experimental unit was a single plant with three replicates. The growth rate, number of leaves, flowers, lateral shoots, and chlorophyll content were measured weekly for five weeks. Treated transgenic plants had greater numbers of leaves, flowers and lateral branches as well as higher chlorophyll levels. Pollen viability was examined in all treatments with no differences among treatments. Plants of both types were self pollinated to generate seeds. Female flowers were bagged before opening and then selfed. Selfed flowers were bagged for at least two days. The fruits were grown for eight to ten weeks with support. Once they reached maturity, fruits were harvested and fruit shape, flesh color, brix, number of normal seeds, number of colored but empty seeds and number of white seeds were recorded. Significant differences were observed only in seed number between wild type and transgenic (both treated and nontreated,) watermelon fruits. The number of seeds in transgenic watermelon plants treated with CuSO4 was reduced to about 5% to 7% of wild type plants. Transgenic plants which received no CuSO4 had approximately 33% to 50% of the seed of wild type.

Evaluation of Resistance to Gummy Stem Blight (Didymella bryoniae) Disease in ipt (Isopentenyl Transferase) Transformed Watermelon Plants

Watermelon plants are susceptible to Gummy stem blight disease that considerably reduces yields worldwide. In order to develop non-specific resistance, watermelon cv. Crimson Sweet was transformed with copper inducible isopentenyl transferase (ipt), the rate-limiting step in cytokinin biosynthesis, gene via Agrobacterium tumafaciences (LBA4404). Transformed (ipt) and nontransformed plants were grown at approximately 28-30 °C day, 20-22 °C night and 16 hours daylight under greenhouse conditions. Once the plants initiated new growth both transgenic plants and wild type plants were sprayed with one of three different concentrations (0, 10 & 50 μm) of CuSO4. Plants were sprayed twice to run-off in a twenty-four hour time period before inoculation with the pathogen. Cultures of the pathogen Didymela bryonia (W353) were grown for about 3 weeks and an inoculum containing 105 conidia per mL was sprayed with the prepared suspension until initial run-off in a humidified chamber. The disease symptoms were evaluated after one week with resistance demonstrated in all treated transgenic plants. All nonsprayed transgenic and wild type plants showed similar disease symptoms. Infected leaf samples were surface sterilized and re-cultured on V8 medium. The characteristics of the recovered pathogen confirmed that it was identical to the stock culture of W353. The same experiment has been conducted on seedlings from transgenic (T1 generations) and non-transformed plants. The non-transformed seedlings showed the first disease symptoms on their cotyledons and lower leaves. Disease resistance was observed in seedlings of the treated transformed plants as compared to nontransformed ones.

Differences in Pathogenicity between two Genetically Distinct Groups of Acidovorax avenae subsp. citrulli on Cucurbit Hosts

AbstractUsing DNA fingerprinting by pulse‐field gel electrophoresis and repetitive extragenic pallindromic (REP)‐polymerase chain reaction (PCR), two distinct groups were confirmed among 64 Acidovorax avenae subsp. citrulli strains collected from a range of cucurbitaceous hosts in the USA, China, Taiwan, Thailand, Canada, Australia, Brazil and Israel. Eighty‐two percent of the group I strains were recovered from non‐watermelon hosts and the subspecies type strain was the only member of this group that utilized l‐leucine as a sole carbon source. On the contrary, 94% of the group II strains were recovered from watermelon and 96% of them utilized l‐leucine. Two‐week‐old watermelon cv. Crimson sweet, cantaloupe cv. Athena, pumpkin cv. Lumina and squash cv. Early yellow crookneck seedlings were susceptible to A. avenae subsp. citrulli strains representing each group with the exception of the subspecies type strain. Overall, seedlings of watermelon cv. Crimson Sweet were most susceptible to A. avenae subsp. citrulli infection followed by cantaloupe, pumpkin and squash. Group II strains were more aggressive watermelon than on other hosts. On the contrary, group I strains were moderately aggressive on all cucurbit hosts tested.

A melancia como fonte de licopeno

This work had the objective of quantifying the principal carotenoids of the watermelon,cultivar Crimson Sweet, obtained from two producing states: Sao Paulo and Goias. The samples werepurchased during the year from the Central Distribution Center (CEASA) of Campinas, totalling five fruitsanalysed individually for each region. The analyses, carried out in duplicate, consisted of extraction withacetone, partition to petroleum ether and quantification by high performance liquid chromatography(HPLC) (C18 column, Spherisorb ODS2, 3 µm, 4.6 mm x 150 mm; isocratic elution, mobile phase of acetonitrilecontaining 0.05% triethylamine:methanol:ethyl acetate (60:20:20); flow rate of 0.8 mL/min), using externalstandardization. The HPLC chromatogram revealed that the watermelon analyzed contained almostexclusively lycopene, with a small amount of β-carotene. The lycopene and β-carotene contents (µg/g)were, respectively, 36 + 5 and 4.7 + 2.4 for the fruits from Sao Paulo, and 35 + 2 and 2.6 + 1.7 for those fromGoias. The concentrations of these two carotenoids resembled those found in tomato, cultivar Carmen (35+ 10 µg/g for lycopene and 3.2 + 0.6 µg/g for β-carotene), showing watermelon to be an important sourceof lycopene. The difference in terms of place of production was not significant.

Biomass, virus concentration, and symptomatology of cucurbits infected by mild and severe strains of Papaya ringspot virus

Pre-immunization with mild strains of Papaya ringspot virus - type W (PRWV-W) has allowed the mosaic disease to be controlled in different cucurbit species, with increases in marketable fruit yield. The objective of this study was to compare virus concentration, biomass and symptomatology of 'Caserta' zucchini squash, 'Menina Brasileira' long-neck squash and 'Crimson Sweet' watermelon plants infected by three mild strains and one severe strain of PRSV-W. Plants were inoculated at the cotyledonary stage, under greenhouse conditions, sampled at 7, 14, 21, 28 and 35 days after inoculation (DAI), and analyzed by PTA-ELISA. The severity of the symptoms was scored according to a scale from 1 to 5, and the fresh and dry biomass of the aerial part of the plants were evaluated at 40 DAI. Concentrations of the mild strains, based on absorbance values of the PTA-ELISA, were lower than the concentration of the severe strain for all species. The mild strains did not cause mosaic in infected plants of all species. Plants of zucchini squash and watermelon infected by the severe strain exhibited severe mosaic symptoms, but the same was not noticed for infected long-neck squash plants. Biomass values from zucchini squash and watermelon plants infected by the mild strains were 1.7 % to 12.4 % lower as compared to healthy plants. Biomass values of zucchini squash and watermelon plants infected by the severe strain presented greater reduction, varying from 29 % to 74 %. However, biomass values of long-neck squash plants infected by the mild and severe strains were similar for all treatments.

Avaliação do vigor de sementes de melancia (Citrullus lunatus Schrad.) pelo teste de envelhecimento acelerado

O trabalho teve como objetivo determinar a eficiência do teste de envelhecimento acelerado para a avaliação do vigor de sementes de melancia (Citrullus lunatus Schrad). Para tanto, sementes de quatro lotes da cultivar Crinsom Sweet foram submetidas ao envelhecimento acelerado a 41 e 45°C por 48, 72 e 96 horas, a 100 e 76% de UR relacionando-se os resultados obtidos com os testes de germinação, primeira contagem de germinação, germinação a baixa temperatura e emergência de plântulas em solo. Os resultados indicaram que o teste de envelhecimento acelerado pelo método tradicional (100% UR) mostrou-se mais eficiente que o método alternativo (76% UR), se constituindo em alternativa promissora para a avaliação da qualidade fisiológica das sementes de melancia. O envelhecimento acelerado a 41°C e 100% UR por 48 horas foi o método mais promissor para a avaliação do vigor dessas sementes.

A Histological Analysis of Regeneration in Watermelon

The optimization of regeneration protocol for different genotypes increases the yield in transformation studies. Cotyledon explants of watermelon [Citrullus lanatus (Thunb) Matsum & Nakai] cv Crimson Sweet were cultured on MS medium containing combinations of benzyl adenine (BA) (0, 5, 10, 20 µM) and indole-3-acetic acid (IAA) (0, 0.5, 5 µM). Maximum shoot growth and subsequent rooting from explants on regeneration medium were obtained from the media containing 10 µM BA + 0.5 µM IAA and 20 µM BA (75 and 78%) by direct organogenesis, respectively. Histological analysis showed that cell division was observed in the epidermal and subepidermal layers. Protuberant structures were observed in tissues between 7 and 12 days in culture. Meristematic structures were observed after 12days in culture which later developed into buds.

Efeitos da interação de potyvirus em híbridos de meloeiro, variedades de melancia e abobrinha

Em razão da freqüente ocorrência de infecção mista, na natureza, o presente trabalho objetivou estudar o efeito da interação de diferentes espécies de potyvírus em meloeiro (Cucumis melo), melancia (Citrullus lanatus) e abobrinha (Cucurbita pepo). Foram usados os seguintes vírus da família Potyviridae, gênero Potyvirus: Papaya ringspot virus (PRSV); Watermelon mosaic virus, (WMV) e Zucchini yellow mosaic virus, (ZYMV). Os efeitos na sintomatologia das infecções duplas e simples de PRSV, WMV e ZYMV foram avaliados em três híbridos de meloeiro, duas variedades de melancia e abobrinha 'Caserta', em experimentos de casa de vegetação. Os três vírus, isoladamente ou em todas as duplas combinações possíveis, foram inoculados, em plantas dos híbridos de meloeiro Hy Mark, Gold Mine e Orange Flesh, variedades de melancia Crimson Sweet e Charleston Gray e abobrinha 'Caserta', usando-se dez plantas de cada híbrido ou variedade, por combinação de vírus. As inoculações foram efetuadas por meio de extratos de folhas com infecção simples dos respectivos vírus. As plantas inoculadas com cada vírus isoladamente e suas respectivas combinações foram observadas quanto ao aparecimento de sintomas durante 30 dias após as inoculações. Amostras foliares das plantas inoculadas foram, também, testadas por ELISA indireto contra os anti-soros correspondentes para cada vírus. As infecções duplas em meloeiro, melancia e abobrinha revelaram, através da avaliação sintomatológica, que existem interações sinérgicas entre PRSV, WMV e ZYMV. As infecções duplas envolvendo o ZYMV apresentaram alta severidade, exibindo sintomas não encontrados em infecções simples, apesar da severidade nas infecções isoladas do ZYMV.

Influence of Diploid Pollinizer Frequencies on Triploid Watermelon Quality and Yields

During the 1999 and 2000 growing seasons in Illinois, studies were conducted to determine the influence of two pollinizers (`Crimson Sweet' and `Fiesta') and three pollinizer frequencies (11%, 20%, and 33%) on `Millionaire' seedless watermelon (Citrullus lanatus) quality and yields. More large-sized [>16 lb (7.2 kg)] `Millionaire' watermelons were produced when `Crimson Sweet' was used as the pollinizer compared to `Fiesta', which resulted in `Crimson Sweet' leading to greater marketable and total `Millionaire' yields. Pollinizers responded similarly over the pollinizer frequencies for `Millionaire' watermelon yields as no pollinizer by pollinizer frequency interaction was observed. The 20% and 33% pollinizer frequencies produced similar `Millionaire' yields per acre and both resulted in greater yields compared to the 11% pollinizer frequency. Soluble solids in `Millionaire' fruits were not influenced by pollinizer or pollinizer frequency. However, hollow heart disorder followed a quadratic response with respect to pollinizer frequency with the lowest amount of hollow heart observed at the 33% pollinizer frequency and greatest at the 11% pollinizer frequency. No significant interaction (P ≤ 0.05) was observed for pollinizer by pollinizer frequency for hollow heart disorder in `Millionaire'; although, more hollow heart disorder in `Millionaire' was observed when `Fiesta' was used as the pollinizer.

Interaction of border and center rows of multiple row plots in watermelon yield trials

Researchers interested in evaluating watermelon (Citrullus lanatus(Thunb.) Matsum. & Nakai) cultivars for yield often use multiple-row plots to simulate the monoculture system growers use or ingle-row plots to save on land, labor, and seeds. An important question is whether there is significant interaction of border rows with center rows when diverse cultivars are planted in adjacent rows. Based on recommendations from watermelon researchers in the U.S., ‘Charleston Gray’, ‘Crimson Sweet’, and ‘Sugar Baby’ were chosen to represent long, medium, and short-vined cultivars, respectively. Cultivars were planted in three-row plots with all nine combinations of the three represented in border and center rows. The experiment was a randomized complete block with the nine border by center plot combinations, two locations (Kinston, Clinton), and three replications at each location. Vine length was measured during the season, and fruit from four harvests were graded (marketable and cull), counted and weighed. Results showed that ‘Charleston Gray’ had the longest vines, followed by ‘Crimson Sweet’ and ‘SugarBaby’. In the analysis of variance, the largest effects (F ratio) on yield were from cultivar, location, and the interaction of the two. The smallest effects were border row and the interaction of center with border row. Center by border interactions were significant (5%level) in some cases, but were usually small and did not involve change in rank. Therefore, researchers interested in running trials with many cultivars and small seed quantities can obtain good data using single-row plots. However, there is a small (but significant) interaction of center with border rows in some cases, so testing at the final stage should be with trials having multiple-row plots or with cultivars grouped by vine length. Additional research is needed to determine the effect of cultivars having extreme plant types, for example dwarf cultivars in bordering rows with long-vined cultivars.

Mycorrhizal colonisation improves fruit yield and water use efficiency in watermelon (Citrullus lanatus Thunb.) grown under well-watered and water-stressed conditions

The effect of arbuscular mycorrhizal (AM) colonisation by Glomus clarum on fruit yield and water use efficiency (WUE) was evaluated in watermelon (Citrullus lanatus) cv. Crimson Sweet F1 under field conditions. Treatments were: (1) well-watered plants without mycorrhizae (WW-M), (2) well-watered plants with mycorrhizae (WW+M), (3) water- stressed plants without mycorrhizae (WS-M) and (4) water-stressed plants with mycorrhizae (WS+M). When soil water tension readings reached −20 and −50 kPa for well-watered (WW) and water-stressed (WS) treatments, respectively, irrigation was initiated to restore the top soil to near field capacity. Water stress reduced watermelon shoot and root dry matter, fruit yield, water use efficiency but not total soluble solids (TSS) in the fruit, compared with the non-stressed treatments. Mycorrhizal plants had significantly higher biomass and fruit yield compared to nonmycorrhizal plants, whether plants were water stressed or not. AM colonisation increased WUE in both WW and WS plants. Macro- (N, P, K, Ca and Mg) and micro- (Zn, Fe and Mn) nutrient concentrations in the leaves were significantly reduced by water stress. Mycorrhizal colonisation of WS plants restored leaf nutrient concentrations to levels in WW plants in most cases. This is the first report of the mitigation of the adverse effect of water stress on yield and quality of a fruit crop.

Capacidade de combinação entre linhas tetraplóides e diplóides de melancia

A capacidade de combinação entre três genitores tetraplóides (LT7-48.1, LT9-24.1 e LTCC-24) e quatro diplóides de melancia ('Crimson Sweet', 'Pérola', 'New Hampshire Midget' e 'Charleston Gray') foi avaliada num esquema de cruzamentos dialélicos parciais. Utilizou-se delineamento de blocos casualizados, com três repetições, formadas por parcelas de sete plantas. Genitores e F1's foram avaliados quanto ao número de dias para o aparecimento da primeira flor masculina e feminina, número de frutos por planta, comprimento da rama principal, massa média dos frutos, teor médio de sólidos solúveis na polpa, diâmetros transversal e longitudinal do fruto, espessura da casca do fruto na região do pedúnculo e na região da cicatriz floral, cor da polpa e ocorrência de ocamento no fruto. Os genitores, tanto diplóides como tetraplóides, apresentaram-se bastante divergentes quanto às características estudadas. Os efeitos da capacidade geral de combinação (CGC) foram superiores aos efeitos da capacidade específica de combinação (CEC) para a maioria dos caracteres, especialmente daqueles relacionados com a produção da planta, indicando a maior importância dos efeitos gênicos aditivos. No entanto, algumas características, como precocidade e ocamento de frutos tiveram controle gênico não aditivo e, portanto, a avaliação e seleção de linhagens em combinações híbridas permitirão a síntese de híbridos triplóides superiores.

Seletividade e eficiência agronômica de herbicidas no controle de capim-colchão na cultura da melancia

Foi avaliada a seletividade e a eficiência agronômica dos herbicidas clethodim e sethoxydim, no controle de Digitaria horizontalis (capim-colchão) na cultura da melancia (cv. Crimson Sweet). O experimento foi conduzido em campo, no município de Floresta, PR, em 1995/96, em delineamento de blocos ao acaso, com quatro repetições. Os tratamentos avaliados foram clethodim nas doses de 84; 96 e 108 g i.a./ha adicionado de 1,0 L/ha de óleo mineral (Dytrol), sethoxydim na dose de 230 g i.a./ha adicionado de 1,0 L/ha de óleo mineral (Assist) e testemunhas com e sem capina. Os herbicidas foram aplicados em pós-emergência, quando a melancia apresentava ramas com 1,4 m e a D. horizontalis em estádio de três folhas a três perfilhos e densidade de 240 plantas/m². Para a aplicação dos herbicidas utilizou-se pulverizador costal de pressão mantida por injeção de CO2, equipado com pontas de jato plano XR110.02 e volume de calda de 200 L/ha. As avaliações de seletividade (Escala E.W.R.C.) e controle das plantas daninhas (0 - 100%) foram efetuadas aos 7; 15 e 30 dias após aplicação dos tratamentos. Os resultados indicaram que o herbicida clethodim, a partir de 96 g i.a./ha, controlou eficientemente a D. horizontalis, sendo estatisticamente superior ao herbicida sethoxydim e à testemunha sem capina. Nenhum dos tratamentos químicos causou fitotoxicidade que afetasse o desenvolvimento e a produção da melancia. A D. horizontalis interferiu no desenvolvimento da cultura, causando redução média de 36,0% da produção da melancia.

Manganese Toxicity in Watermelon as Affected by Lime and Compost Amended to a Hawaiian Acid Oxisol

Manganese (Mn) toxicity in crops is a serious problem in Hawaii, especially Kauai and Oahu, where most soils are highly weathered. To devise a management strategy to control Mn toxicity, a greenhouse experiment was conducted on an acid (pH 4.4) Oxisol (Wahiawa series) having 15g·kg-1 total Mn. Factorial combinations of lime (0, 2.0, and 4.0 g·kg-1 CaCO3) and two composts (made from chicken manure and from sewage sludge at 0, 5, and 10 g·kg-1) were applied to the soil, which was subsequently planted to watermelon (Citrullus lanatus Thunb. `Crimson Sweet'). Our preliminary results showed that: 1) liming reduced Mn extractability and phytoavailability, but the reduction in Mn per unit increase in pH was much less than predicted by theory; 2) for good watermelon growth, soluble Mn, as extracted by the saturated paste method, should be <2.0 mg·L-1 corresponding to a soil pH >5.7; 3) unlike the saturated-paste extractable Mn, the Mehlich3-extractable Mn varied less with pH in a given soil series than between soil series; 4) effects of composts on Mn toxicity varied with compost properties, especially their Ca content and pH altering capacity; and 5) the diagnostic criteria for Mn toxicity in watermelon are tentatively proposed as: leaf Mn >1000 mg·kg-1 and leaf Ca/Mn ratio (g·g-1) <25.

Capacidade de combinação em sete populações de melancia

Este trabalho teve como objetivo estimar as capacidades geral (CGC) e específica (CEC) de combinação e os efeitos recíprocos (ER) em relação à precocidade, componentes de produção e características do fruto em sete populações de melancia. As populações foram intercruzadas em dialelo, incluindo os recíprocos. Todas as variáveis avaliadas, com exceção do número de frutos por planta, apresentaram efeitos da CGC, CEC e ER significativos. Efeitos gênicos aditivos foram importantes em relação ao número e peso de frutos por planta, assim como em relação à cor, espessura e teor de sólidos solúveis da polpa. Quanto ao número de dias para o aparecimento da primeira flor feminina e número de sementes por fruto, ocorreu predominância de efeitos gênicos não-aditivos. Foram identificadas algumas populações e algumas combinações híbridas superiores, que podem ser exploradas em programas de melhoramento. As populações tradicionais P14 e B9, coletadas no Nordeste do Brasil, são promissoras para serem empregadas em programas que visem melhorar o número e o peso dos frutos, ao passo que a M7 é promissora em relação à precocidade. As variedades comerciais Charleston Gray e Crimson Sweet poderão ser empregadas para melhorar o teor de açúcar e a cor da polpa.

VIDA ÚTIL PÓS-COLHEITA DE MELANCIA SUBMETIDA A DIFERENTES TEMPERATURAS DE ARMAZENAMENTO

The purpose of this study was to determine the post harvest shelf life of ‘Crimson Sweet’ watermelon fruit which is yielded in the ‘Gangorra’ commercial planting 20 km from MossoroRN-Brazil. The fruits were harvested and transported to the Post harvest Fruits Laboratory of the Escola Superior de Agricultura de Mossoro-ESAM. The experiment was carried out in a completely randomized design in a 3 x 7 factorial scheme with five replicates. The first considered factor was the storage temperature (10 o C, 12 o C and ambient temperature) and the second factor was the storage time (0, 5, 10, 15, 20, 25 and 30 days). The following traits were evaluated during this period: internal and external fruit appearance, pulp firmness, total titratable acidity, pH, total soluble solids and content total soluble sugars. The ‘Crimson Sweet’ watermelon had 25 days of post harvest shelf life. The best temperature was 10 oC, that maintained the external and internal appearances with superior note to 3,0 that’s considered commercial, soluble solids above 10,5 g  100 mL -1 and total sugars 9,44 g 100 mL -1 .

Short-term Cyclic Cold Temperature Stress on Watermelon Yield

Watermelon [Citrullus lanatus (Thunb) Matsum. & Nakai.] seedlings may be repeatedly exposed to temperatures alternating between almost freezing and optimum soon after field transplanting. `Carnival', `Crimson Sweet', `Millionaire' and `Crimson Trio' watermelon transplants were exposed to cold temperature stress at 2 ± 1 °C in a walk-in cooler and then to 29 ± 5 °C in a greenhouse immediately before field planting to simulate temperature alternations that may occur after field transplanting. Cold-stressed transplants were field planted after all risk of ambient cold stress passed. In 1998, transplants were exposed to 2 °C from 9 hours to 54 hours, and in 1999 from 9 to 81 hours. Early yields of all cultivars, except Carnival, significantly decreased with increasing hours of cold stress in both years. Total yields of `Carnival' decreased linearly in both years with a 10% yield reduction occurring from 14 to 15 hours of cold stress. `Crimson Sweet' yields were reduced in 1999 only, with 16 hours of cold stress reducing yield 10%.

Watermelon Production as Influenced by Lime, Gypsum, and Potassium

Watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] were grown with three rates each of lime, gypsum, and K during two seasons to evaluate their effects on fruit production and mineral concentration. The first experimental site was a recently cleared Sparr fine sand with an initial water pH of 5.0 and Mehlich I extractable K of 8 mg·kg-1 (very low) and 20 mg·kg-1 Ca (very low). The second site was a virgin Pomona fine sand with a water pH of 4.8, 28 mg·kg-1 K (low), and 612 mg·kg-1 Ca (high). `Crimson Sweet' fruit yields were reduced 10% with an increase in lime rate from 0 to 4.48 t·ha-1 in the first season. In the second season, lime rate had no effect on yield. In both seasons, fruit yields were reduced 14% with an increase in Ca from gypsum from 0 to 1.12 t·ha-1. On the soil testing very low in K, yield increased with an increase in K rate from 90 to 224 kg·ha-1 with no lime or gypsum. On the soil testing low in K, greatest yields were obtained with 90 kg·ha-1 K with no lime and gypsum. Application of lime and gypsum increased Ca and decreased K in seedlings but not consistently in older leaf and fruit tissues. An increase in K application increased leaf K in the first season but not in the second. Fruit firmness and soluble solids content were not consistently affected by treatment during the two seasons. Thus, on soils low in toxic elements (Mn and Al) such as used in this study, watermelon will grow well and tolerate a wide range of soil pH values without additional Ca from lime or gypsum.