Abstract
‘Melogold’ is an early-maturing, seedless, hybrid grapefruit-type citrus released for use in interior areas of California. It may be suitable for intermediate climate zones in other citrus areas. Fruit quality has not been satisfactory in cool, humid climates nor in hot desert areas.
Abstract
‘O roblanco’ is an early-maturing, seedless grapefruit-type citrus released for use in the interior areas of California. It may be suitable for interm ediate climate zones in other citrus areas. Fruit quality has not been satisfactory in cool, humid climates nor in hot desert areas.
The effects of grapefruit cultivar and coating type on chilling injury (CI) incidence were examined. The shellac coating widely used for exported citrus resulted in the lowest CI incidence in white `Marsh' grapefruit stored for 2 months at 4 °C and 92% ± 3% relative humidity compared with nonwaxed fruit or fruit waxed with either carnauba or polyethylene waxes. The order of coating performance for reducing CI was shellac > carnauba > polyethylene > nonwaxed fruit. For `Flame' little difference of coating type on CI was detected after 2 months of storage. Overall, CI incidence was high in fruit of the cultivars harvested from September to December, low in February, and high again after March but was generally higher in white `Marsh' seedless grapefruit than `Ruby Red', `Rio Red', or `Flame'. However, little difference of cultivar on CI incidence was found among the `Ruby Red', `Rio Red', and `Flame' grapefruit except the October harvest in which CI was higher in `Ruby Red' than in `Rio Red' and `Flame' grapefruit. These studies suggest that the coating and cultivar should be considered in the postharvest management of CI in commercial packing.
Grapefruit ( Citrus × aurantium ) belongs to the family Rutaceae, subfamily Aurantioideae. Grapefruit is unique among citrus ( Citrus sp.) fruit due to its distinctive flavor, health benefits, and recent Caribbean islands’ origin less than 300
Abstract
The shape of ‘Redblush’ grapefruit, Citrus paradisi Macf., grown in controlled environments was affected by the difference between day and night temperature. Fruit grown under a 32°/30°C day/night temperature regime had creased stem ends; a 32°/24° regime resulted in normal fruit, and 32°/7° induced severe sheepnosing. Reducing daylength from 14 to 11 hours had no influence on fruit shape.
The world market for citrus (Citrus spp.) products has undergone dramatic shifts over the last decade. These shifts are influencing development and planting of new citrus cultivars. Seedlessness and very easy peeling have become paramount in mandarin types (C. reticulata and hybrids), and new cultivars are being developed through plant breeding and selection of new sports. In both sweet orange (C. sinensis) and grapefruit (C. paradisi), essentially all important cultivars are derived from a single original hybrid of each fruit type, and plant improvement has focused on selection of sports with redder color and extended maturity. The existence of many active citrus breeding programs makes it likely that we will continue to see evolution of new citrus cultivars over the foreseeable future.
Wind-induced blemishing known as windscar and lesions from the disease melanose (caused by Diaporthe citri) are two of the most important causes of fresh grapefruit (Citrus paradisi) cullage in Florida. Copper hydroxide fungicides are the primary means of controlling melanose, but high air velocities from passing sprayers have been suspected of increasing windscar. In 1998 and 1999, airblast applications of Cu(OH)2 (1.7 kg·ha-1 Cu) were made at a range of early fruit development stages to a fresh grapefruit orchard in the Indian River region of Florida. These applications supplemented aerial sprays of Cu(OH)2 that were made uniformly across the entire experimental site at biweekly intervals beginning near full bloom. During the commercial harvest period fruit were sampled from three regions (interior, upper exterior, and lower exterior) of each treatment tree and were evaluated for percentage of fruit surface covered by windscar and severity of melanose. Airblast applications did not affect windscar in either year, but windscar was significantly greater from the upper exterior of the canopy, which is likely to experience the highest natural wind velocities. From these data, it appears unlikely that airblast applications significantly contribute to windscar of Indian River grapefruit. In 1998, no trees receiving airblast applications had significantly lower melanose incidence than the trees sprayed only via aircraft; however, trees receiving four airblast applications were scored as having higher apparent melanose on exterior samples than trees receiving most other treatments. This is consistent with high levels of Cu injury on these fruit which can superficially resemble melanose. Following treatment in 1999, trees receiving four airblast applications of Cu(OH)2 had significantly lower melanose scores than trees receiving either no or only early airblast applications, but were not significantly different from trees receiving a single spray 5.5 weeks postbloom. A computer model, which estimates Cu levels on fruit based on fruit growth, rainfall, and application parameters, indicated exterior fruit receiving four airblast sprays had >3 μg·cm-2 [Cu] for 40 days in 1998 but only 10 days in 1999, which reflects increased probability of Cu damage in 1998. It appears that aerial application supplemented by airblast merits further study as an economical means of melanose control.
Adjacent but separate trials of `Oroblanco' and `Melogold', both triploid pummelo [Citrus grandis (L.) Osbeck] × grapefruit (Citrus paradisi Macf.) hybrids, were established on nine rootstocks in the Indian River citrus region of Florida in 1993. The trees on the citrandarin rootstock ×639 [Cleopatra mandarin (C. reticulata Blanco) × trifoliate orange (Poncirus trifoliata L.)] were significantly more productive than trees on any other rootstock tested for `Oroblanco' and all rootstocks except Swingle citrumelo (C. paradisi × P. trifoliata) and Cleopatra mandarin for `Melogold'. Cumulative production of `Oroblanco' on ×639, through year 9, was 50% higher than for Swingle or Volkamer lemon [C. limon (L.)], which were the next highest in yield. `Melogold' displayed extremely low yield, with 45% of trees producing fewer than 50 fruit total in the 9 years of this study. Carrizo citrange (C. sinensis Osbeck × P. trifoliata) produced the smallest trees with both scion varieties, reflecting poor adaptation of this rootstock to the calcareous soil at the trial site. As expected, acidity of `Oroblanco' and `Melogold' was much lower than would be observed for grapefruit when fall harvested, with similar total soluble solids (TSS), and much higher TSS: titratable acidity ratio. Some rootstock effects on internal quality were observed.
residential grapefruit tree in Mission, TX; therefore, it is very important to establish CLas distribution in citrus tree parts under field conditions where the temperatures are consistently high and different from Florida or elsewhere. According to 1981
, pork, soybeans, cotton, and others. Only 15, however, currently fund such programs, including Marketing Order 906 for citrus products (grapefruit and oranges) grown in the Lower Rio Grande Valley of Texas. One of only two federal marketing orders