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D.T. Ray and J.D. McCreight

A new chlorophyll-deficient mutant is the first cytoplasmically inherited trait described in melon. This mutant is characterized by yellow apices with the leaves and stems progressively turning green in color as the branches mature. A protocol is proposed for naming and symbolizing cytoplasmic traits in melon. This mutation is named yellow-tip and symbolized cyt-Yt.

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Maria E. Pérez de C, Josefina Rodirguez, Susana Torcates, and Mario Pérez y Hugo Ramírez

Several postharvest quality parameters of cantaloupe fruit were grown under different organic and mineral fertilization schemes We evaluated a Laguna hybrid (Asgrow) cantaloupe grown under a design of blocks completely randomized, with three fertilizer treatments corresponding to: T1, goat manure; T2, simple fertilization; T3 mixed fertilization, with six replications each. The fruits were mature-harvested and stored in a room with an average temperature of 18°C for posterior laboratory analysis. The results showed different effects of the treatments on the following parameters: total soluble solids, diameter of the fruits, and thickness of the pulp, and showed no effects on consistency of fruits, cavity, dry matter, and fresh weight. All these parameters decreased during the period of storage. The organic manure treatments showed the best values of most of the evaluated parameters.

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Hugo Ramirez, Mary Torcates, Jose Perez, Josefina Rodriguez, and Marin E. Perez

The response of different doses of calcium sulfate or phosphogypsum (PG) on several postharvest quality parameters of `Laguna' cantaloupe hybrid were analyzed in the semi-arid San Francisco experiment station (UCLA), located in the Lara state, Venezuela. The experimental design was a completely randomized block with four treatments (0, 300, 600, and 1200 kg/ha, PG) with five replications. The PG was surface-spread on the irrigation furrows, 1 day before sowing. The fruits were harvested at maturity and stored under an average temperature of 28°C for posterior quality analysis. The PG treatments did not have any effect on the studied parameters: total soluble solids (°Brix), consistency (kg/cm2), diameter, and cavity of the fruit, pulp thickness, and dry and fresh matter. All of the parameters evaluated decreased during the 6 days of storage. These results could be because of the low doses of PG used or because the supply of calcium was not a limitation in these soils.

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Hector G. Nunez-Palenius, Daniel J. Cantliffe, Harry J. Klee, and Don J. Huber

Embryo abortion and empty seeds after self-pollination occur in some transgenic (ACO antisense) `Galia' male parental lines. An embryo-rescue system in this melon was developed to save potential viable embryos. To obtain the best and reliable embryo-rescue technique, several parameters were used including an improved (five new supplements) nutrient medium (named E-21) from the E-20A basic medium (Sauton and Dumax de Vaulx, 1987), an inoculation system (removing the embryo from the seed or intact seed), and the use of different fruit harvesting dates of the wild type and a transgenic `Galia' male parental line. Fruits of wild type (WT) and transgenic (ACO gene in antisense orientation) `Galia' male parental line were harvested at 4, 10, 17, 24, and 30 days after pollination (DAP). Fruits were surface sterilized by dipping in a 20% commercial bleach solution for 30 minutes. Subsequently, seeds were removed from fruit under sterile conditions. These seeds were either used to dissect the embryos or placed directly with the hilum facing E-20A or E-21 medium. Seedlings from all treatments were transferred to E-21 elongation medium, incubated 4 weeks, and transferred to soil to evaluate growth. The efficiency of this technique was greater when the time after pollination (4, 10, 17, 24, and 30 DAP) to rescue the embryos was increased. Thus, 30 DAP was the best time to rescue the embryos. The number of rescued embryos using E-21 medium was greater than with E-20A. We did not find any significant differences in survival efficiency rate between WT and transgenic embryos. We have obtained a competent embryo-rescue technique for WT and transgenic `Galia' male parental line, which can be applied to rescue valuable GMO hybrid-melon embryos.

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Wayne A. Mackay, Timothy J Ng, and Freddi A. Hammerschlag

Studies examining exposure methods and callus type were conducted to develop an in vitro selection system using roridin E as a selection agent. Vacuum infiltration of callus with the toxin solution was the only successful selection method at the concentrations tested. Primary callus (callus originating directly from the explant) was not sensitive to roridin A or E at the concentrations used. Secondary callus (callus produced from primary callus) exhibited a differential response to roridins A and E similar to that of detached-leaf assays. Electrolyte leakage studies of callus were not conclusive in establishing the membrane as the site of toxin action or useful for screening tolerance in vitro. A small percentage of callus from tolerant and susceptible cultivars survived repeated exposure to roridin E at 50 μg·ml-1.

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David W. Wolff

We conducted a field screen of 130 melon cultigens to identify potential sources of host-plant resistance to Monosporascus cannonballus. Seed were sown in Speedling trays with inoculated or non-inoculated media. Plants were transplanted into a field known to be highly infested with Monosporascus cannonballus. Noninoculated plots were planted in rows that were fumigated with Telone II. Cultigens were arranged in a randomized complete block with three replications in each treatment (fumigated, nonfumigated). A disease symptom rating (1 = complete death to 5 = no symptoms) was taken at 78 and 90 days post-transplanting. Disease symptoms were most severe and occurred earliest in the inoculated, nonfumigated plots. Natural infection by Monosporascus occurred in the fumigated plots as over 95% of root samples collected contained perithecia. At the second rating date, 108 of the 130 cultigens tested were classified as moderately to highly susceptible (rating < 2.5). The four most resistant genotypes had a second rating equal or close to 4.0 (`Galia', `Deltex', `Rocky Sweet', and `Charlynne'). A group of 14 genotypes showed moderate resistance with a second rating of 3.0. Included in this group were `Morning Ice', `Doublon', `Israeli', `MR-1', `Santa Clause', and `Primo'. The physiological stress of a concentrated fruit set increases severity of vine decline symptoms.

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Entin Daningsih, Laurie Hodges, and James R. Brandle

Experiments were conducted during summer seasons from 1991 to 1994 to find out the effect of winds on early growth of muskmelon. A randomized complete-block design with sheltered and exposed areas as treatments was used. Sensors for air temperature and relative humidity (model HMP35C or model XN217, Campbell Scientific) were placed at canopy height and 3-cup anemometers (model 12102, R.M. Young, Traverse City, Mich.) were 50 cm aboveground. All sensors were connected to CR10 automatic data loggers and recorded hourly average data. Using regression analysis, we found that the accumulative windspeed frequency below threshold (<4 ms–1) can be used to predict both accumulative hourly heat units of air temperature (GDHT) with R2's more than 0.85 and total muskmelon fresh and dry weight and leaf area index at early growth. Predicted models using accumulative hourly windspeed frequency have R2's >0.80 in sheltered areas. Adding vapor pressure deficit to the model improves the prediction of muskmelon early growth, especially in exposed areas.

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S. Jenni and K.A. Stewart

As part of a program to develop a model for growth and development of muskmelon produced under various mulch and row cover combinations, all perfect flowers of five plants were tagged and measured on a daily basis. The polar and equatorial lengths of the inferior ovary were recorded from anthesis to fruit maturity. Mature fruits were harvested at full slip. The location of each flower on the plant was coded. Flowers and subsequent fruits were classified according to the following phenological stages: immature, close to mature, close to full bloom, full bloom, wilted, past full bloom, close to fruit, fruit. The netting was visually evaluated and rated on a scale of 0 to 5, the highest value representing maximum netting. At fruit maturity, the weight, polar and equatorial length of each fruit were measured and mature and immature seeds counted. The number of fruits that reached maturity was directly proportional to the total number of perfect flowers produced on a plant. Fruit weight during growth could be predicted from the polar and equatorial lengths.

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J. Alberto García-Salazar, Rhonda K. Skaggs, and Terry L. Crawford

fruit and vegetable producers in non-export regions who strategically organize, produce, promote, and sell their products. Cantaloupe melons [Cucumis melo (L.)] are produced in at least 13 different Mexican states, in every climatic zone, and by growers