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  • Journal of the American Society for Horticultural Science x
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The purpose of the present study was to investigate the role of ethylene action, via use of the ethylene antagonist 1-methylcyclopropene (1-MCP), on the senescence and quality of fresh-cut ripe papaya (Carica papaya L. `Sunrise Solo') fruit. Ripe papaya fruit were treated with 2.5 μL·L-1 1-MCP and immediately processed into fresh-cut slices or left intact. At 2-day intervals over 10 days at 5 °C, continuously stored slices were monitored for ethylene production, firmness, electrolyte leakage, color, sensory changes, and pathogen incidence. Slices freshly prepared from intact fruit stored under identical conditions were measured similarly. Ethylene production did not differ significantly between the treatments, although production rates were slightly but consistently higher in slices from intact control compared with intact 1-MCP-treated fruit. Mesocarp firmness of continuously stored slices and slices from fruit stored intact was significantly retained by 1-MCP. Firmness of continuously stored slices from 1-MCP-treated fruit declined 50% compared with 75% for control slices. Firmness of fresh-cut slices prepared from intact control and 1-MCP-treated fruit at each sampling interval declined 26% and 15%, respectively. Electrolyte leakage remained low and changed little in slices freshly prepared from fruit stored intact. Leakage from continuously stored papaya slices increased after 4 days, and after 6 days controls increased significantly compared with stored slices derived from papaya fruit initially treated with the ethylene antagonist. The flesh color of continuously stored slices or slices prepared from fruit stored intact was influenced by 1-MCP only during the later periods of storage. Microbial counts in stored slices or slices prepared at each sampling were generally unaffected by 1-MCP. Informal sensory analysis indicated that the edible shelf life was 6 days in stored slices from 1-MCP-treated fruit compared with 2 to 3 days for stored slices from control fruit.

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Abstract

The effect of waxes and plastic shrink wraps on weight loss from papaya (Carica papaya L.) fruit during ripening was determined. Loss of ≈8% of initial weight from mature-green papaya produced “rubbery”, low-gloss, unsalable fruit. The rate of weight loss from ripening papaya was ≈0.1% initial weight/day per mbar. The highest rate of weight loss occurred via the stem scar (nearly 3500 mg·cm−2·day−1) while 4.4 mg·cm−2·day−1 was lost through the skin. The major mode of weight loss was the skin because of its larger surface area. The stomata did not appear to function in ripening fruit. The skin's resistance to water movement increased at the start of ripening, then declined with no apparent change in the rate of total water loss. Part of the decline in resistance was associated with the disruption of the cuticle with latex, especially after the 50% ripe stage. These results suggest that the major site of resistance to weight loss changed late in ripening. Fruit waxing reduced weight loss by 14% to 40%, while plastic shrink wraps reduced loss by ≈90%. The loss of water was the major component of weight loss. Some waxes and one wrap delayed ripening by 1 to 2 days at ambient temperatures, after storage for up to 2 weeks at 10C. Occasionally, off-flavors occurred in waxed and wrapped fruit when the fruit cavity CO2 level exceeded ≈7% at the full-ripe stage.

Open Access
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Abstract

A phosphorus fertilizer experiment at Puna, Hawaii comprising 3 application rates was conducted over a period of 11/2 years in “aa” lava soil on fruiting papaya trees (Carica papaya L. ‘Solo’). Leaves at 3 stages of maturity were sampled 4 times a year, and the dried ground leaves were chemically analyzed for P. The weight of fruits was obtained at weekly intervals. A curvilinear regression of yield on concentration of P was determined for each leaf tissue at each stage, at each sampling date. A multiple correlation coefficient was then obtained from each of these calculations.

In general, the highest multiple correlation coefficients were obtained with the “recently matured” petiole. Thus, the concentration of P in this tissue on a dry weight basis was selected as the P index of papaya. The critical levels which related yield to the P index and the weights of leaves to the P index were determined for April and May and were found to be about the same. They were 0.25% P for the maximum yield or weight of leaves and 0.213% P for 5% off the maximum. These levels can serve tentatively as a basis for P fertilization of papaya in the Puna area of Hawaii.

Open Access

Abstract

Papaya plants, Carica papaya L. cv. Solo, were treated with 3 levels of lime combined with 3 levels of P in a split-plot arrangement. Optimal yield of papaya was maintained when the pH of the surface soil ranged from 5.5 to 6.7. Liming lowered petiole concentrations of Mn, K, and Mg and raised those of Ca and P; petiole P was raised when P was applied only. Phosphorus fertilization increased the growth rate of the tree-trunk circumference only at the early stage of growth, while liming affected growth later than P. Phosphorus fertilization raised the petiole concentrations of P, N, Mn, and Zn and lowered petiole concentrations of K and Cu.

Open Access
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Abstract

N and P fertilizers in factorial combinations were applied to flowering and bearing papaya (Carica papaya L.) grown on aa lava soil. An increase in N fertilization increased the number of harvested fruit and yield of marketable fruit and culls but decreased fruit size. P fertilization increased the number of harvested fruit and yield of culls but did not affect yield of marketable fruit. N fertilization increased petiole concentrations of N, Mg, S, Fe, Mn, Zn, and Cu and decreased those of K and B. P fertilization increased petiole concentrations of P, N, and Mn, and decreased those of Ca, S, and Cu. Petiole N concentrations associated with maximum yield of marketable fruits were determined under low P (41 kg P/ha) and the combined medium (186 kg P/ha) and high P (723 kg P/ha) plots.

Open Access
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Abstract

Nitrogen fertilizers as urea and ammonium-nitrate-sulphate were supplied at 2 rates to fruiting papaya trees. Control trees were untreated. Concentrations of petiole N and fruit yield increased with N applications. Petiole N and petiole water affected fruit yield in June. In December tree size and petiole N affected yield. Although N application rate was the dominant variable which affected the concn of petiole N in both June and December, petiole K also affected petiole N in June. The December data were used to determine the petiole N level (1.45% N) which gave max yield. This N level can be used as a basis for applying N fertilizers to fruiting papaya trees in Hawaii.

Open Access
Authors: and

Abstract

Fruiting papaya trees (Carica papaya L. cv. Solo), grown on “aa” lava soil at Puna, Hawaii, were supplied K fertilizer at rates of 0, .208, and .519 lb. K/tree/6 weeks. Leaves at 2 stages of maturity were sampled for K analysis. The method of curvilinear regression was used to relate leaf K to yield of papaya.

The multiple correlation coefficients obtained from the curvilinear regressions of yield on K were high with all tissues. Because the recently matured petiole had been selected previously as the N and P index tissue, and because good relationship was obtained in the present study, this tissue was also selected as the K index tissue. The critical concentration in this tissue was 3.61% K on the dry weight basis. At the adequate level of K. fruit weight and fruit soluble solids content were greater than at the deficiency level. At the excess level, fruit weight was unchanged while the soluble solids content increased compared with fruit at the adequate level.

Open Access
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Abstract

Nitrogen fertilizer was applied at 5 rates to fruiting, hermaphroditic papaya trees, var. ‘Solo’, at Waimanalo, Oahu, Hawaii. Leaves at 3 stages of maturity—recently matured, matured, and old—were sampled at 15-week intervals for 1 year. Total N and nitrate-N were determined on the petioles while total N only was determined on the blades. Curvilinear regressions of yield on concentrations of total N or nitrate-N were determined for leaf tissues of the 3 stages at each sampling date, and multiple correlation coefficients were calculated.

Although the multiple correlation coefficients were highest for total N and nitrate-N of the matured petiole, the recently matured petiole was preferred as the N index tissue because it could be sampled more precisely, and it was previously selected as the P index tissue. As a N index, total N was selected over nitrate-N because the former appeared more useful over a wide range of growing conditions. Tentative N critical levels, relating % N to yield of papaya were determined for certain times of the year.

Open Access

Transgenic plum plants expressing the papaya ringspot virus (PRV) coat protein (CP) were produced by Agrobacterium-mediated transformation of hypocotyl slices. Hypocotyl slices were cocultivated with Agrobacterium tumefaciens strain C58/Z707 containing the plasmid pGA482GG/CPPRV-4. This plasmid carries the PRVCP gene construct and chimeric NPTII and GUS genes. Shoots were regenerated on Murashige and Skoog salts, vitamins, 2% sucrose, 2.5 μm indolebutyric acid, 7.5 μm thidiazuron, and appropriate antibiotics for selection. Integration of the foreign genes was verified through kanamycin resistance, GUS assays, polymerase chain reaction (PCR), and Southern blot analyses. Four transgenic clones were identified. Three were vegetatively propagated and graft-inoculated with plum pox virus (PPV)-infected budwood in a quarantine, containment greenhouse. PPV infection was evaluated over a 2- to 4-year period through visual symptoms, enzyme-linked immunosorbent assay, and reverse transcriptase PCR assays. While most plants showed signs of infection and systemic spread of PPV within l-6 months, one plant appeared to delay the spread of virus and the appearance of disease symptoms. Virus spread was limited to basal portions of this plant up to 19 months postinoculation, but, after 32 months symptoms were evident and virus was detected throughout the plant. Our results suggest that heterologous protection with PRVCP, while having the potential to delay PPV symptoms and spread throughout plum plants, may not provide an adequate level of long-term resistance.

Free access
Authors: and

Abstract

Bearing Solo papaya plants (Carica papaya L.) 24- to 48-months old grown on aa lava soil were treated with N and K fertilizers in factorial combinations. An increase in N or K fertilization increased the total number and total weight of marketable fruit and the weight of each marketable fruit. N fertilization increased petiole concentrations of N, Fe, Mn, Cu, and Zn, and decreased those of P and B. K fertilization increased petiole concentrations of K and Mn, and decreased those of N, P, Ca, Mg, Na, and B. The maximum yield of marketable fruit was associated with petiole concentrations of 1.44% N and 2.52% K.

Open Access