Pummelo Fruit Research Articles

Limonoids in Pummelos [Citrus grandis (L.) Osbeck

ABSTRACTJuice and seeds from 16 cultivars of mature pummelo fruits were analyzed for limonoid content. Pummelo juice contained an average of 18 ppm limonin and 29 ppm total limonoid glucosides. Compared to other juices, ptmnnelo contained very high concentrations of limonin and very low concentrations of limonoid glucosides. Limonin, nomilin, obacunone and trace amounts of deacetyhromilin were found in pummelo seeds. The 17–β‐D‐glucopyranoside derivatives (glucosides) of nomilin, nomilinic acid and obacunone were also present. Total limonoid aglycone concentration in the seeds ranged from 773 ppm to 9,900 ppm and total limonoid glucosides ranged from 130 ppm to 1,912 ppm.

Pummelo fruit transcript homologous to ripening-induced genes.

Organic acid accumulation in the vacuole of juice cells of citrus fruits is a developmentally regulated process, the degree and timing of which varies greatly among species and varieties and is highly susceptible to environmental conditions (Clements, 1963; Ting and Vines, 1966; Vandercook, 1977). Total titratable acidity of the fruit juice of the acidless pummelo 2240 (Citrus maxima [Burm.] Merrill) is only 0.10% on a weight basis; HPLC analysis indicates that the citric acid concentration of pummelo 2240 fruit juice is 10 times lower than that in normal fruits. The acidless phenotype of pummelo 2240 is caused by a mutation involving a single nuclear gene, acitric, that does not affect other traits (Cameron and Soost, 1977; M.L. Roose, unpublished results). To generate citrus varieties of moderate acidity, pummelo 2240 was used in crosses with varieties of i n te rmed ia te and high ac id levels (Soost and Cameron, 1961). F, and backcross populations obtained from these crosses include low-acid individuals that are homozygous for acitric and high-acid individuals that carry at least one copy of the wild-type allele. As part of a continuing effort to identify acitric, two-dimensional IEF/SDS-PAGE protein patterns of tonoplast-enriched fractions obtained from the juice of lowand high-acid fruits were compared. A moderately abundant polypeptide of 10 to 15 kD and approximately neutra1 pI was identified in the juice of immature low-acid fruits that was not detected in juice from highacid fruits at the same developmental stage. Mouse polyclonal antibodies raised against the electroeluted protein reacted with a single low-molecular-weight protein of juice tissues and seeds; the protein was not detected in roots, epicotyl, fruit rind, or unstressed leaves. Full-length cDNA clones encoding the purified polypeptide were isolated that showed strong nucleotide sequence similarity to the Lycopersicon esculentum genes asrl and asr2 (GenBank accession Nos. L08255 and L20756). The tomato genes encode 13-kD proteins, whose expression is induced in leaves by water stress and in fruit pericarp by ripening (Iusem et al., 1993). The citrus gene, designated asr l , encodes a 98-amino acid polypeptide of 10.87 kD. Like the tomato asrl product, the citrus protein is rich in Ala, Glu, His, and Lys (Table I).

Scierification of juice sacs in pummelo (Citrus grandis) fruit

Granulation of juice sacs in pummelo (Citrus grandis L.) fruit was found to occur upon ripening. The juice sac tissue consisted of epidermal and subepidermal cell layers, an elongated cell layer, and juice cells. The granulation was accompanied by the appearance of opaque white regions inside transparent tissue. The subepidermal cells of the granulated tissue were disordered and the cell walls of the elongated and the juice cells were distinctly thickened. An ultrastructural study has shown that the subepidermal cell walls of granulated juice sacs were distorted and had swollen regions. The cell walls of both the elongated and the juice cells had secondary thickening with pits. The total dry weight, cellulose (as glucose), lignin, and hemicellulose (as xylose) were significantly higher and insoluble proteins were lower in granulated juice sacs than in non-granulated ones. The content of insoluble neutral sugars such as rhamnose, arabinose, mannose, and galactose decreased as a result of granulation, as did that of soluble sugars glucose, fructose, sucrose, and organic acids. Thus, it seems that granulation of pummelo fruit juice sacs is a result of lignification of the juice cells, which leads to the formation of sclerenchyma.

Light‐induced postharvest regreening of pummelo fruit*

SUMMARYRegreening was observed and measured in harvested pummelo fruit stored in the light. At temperatures of 22 ‐ 28°C, regular daylight was sufficient for regreening to occur. The addition of continuous fluorescent light intensified the process. Pre‐stored fruit held in darkness at 11°C and non‐stored fruit responded to both light conditions in a similar manner. Electron microscopy has shown that globular chromoplasts revert to chloroplasts during regreening. The similarities between regreening processes in preharvest and postharvest fruits are discussed.

ハッサク及びブンタン果実のリモノイドの時期別変化

The limonoid content in the component parts of Hassaku (Citrus hassaku hort. ex Tanaka) and pummelo(Citrus grandis Osbeck) fruits was investigated at monthly intervals.1. The major limonoid in Hassaku fruit was limonin, showing a maximal concentration of 50ppm in the flesh in September. The nomilin concentrations in the flesh and segment membrane reached maxima of 20 and 500ppm, respectively, in August and then decreased rapidly. In the seeds, nomilin and limonin showed maximal concentrations in October and November, respectively.2. All the parts of pummelo fruit except flavedo contained a large amount of nomilin, and it was particulary true in albedo and segment membrane. The deoxylimonin content in the segment membrane was similar to the limonin content in the segment membrane during fruit maturation. The limonin concentration in the seeds showed a maximum in December and it was far higher in the kernel than in the seed coat.3. In pummelo fruit, the total limonoid content reached a maximum of 200mg per fruit. The total limonoid content in the seeds was less than that in albedo or segment membrane in spite of a high concentration of limonoids in the seeds. It became clear that in both Hassaku and pummelo fruits the limonin concentration reached a maximum one month later than the nomilin concentration in all the component parts.

Chandler—an early-ripening hybrid pummelo derived from a low-acid parent

Abstract does not appear. First page follows. The pummelo (Citrus grandis Osbeck) is a citrus species which is widely grown and used as a fresh fruit in southeast Asia, but is little known in the United States. Many varieties exist, partly because pummelos produce only sexual progeny and each new seedling is likely to be somewhat different from the next. Pummelos and pummelo culture have been described by (Wester (1917))4 in the Philippine Islands, (Reinking and Groff (1921)) and (Groff (1927), (1930) in Thailand, and (Ochse (1931)) in the Dutch East Indies. (Reasoner (1888)) discussed some varieties of pummelo growing in Florida. (Swingle (1943)) and (Webber (1943)) have discussed the botany and some of the cultivated varieties of the pummelo. Among citrus fruits, the grapefruit is the closest relative of the pummelo. The two are similar in many respects, but the pummelo fruit is larger and has firmer flesh. In most varieties, it also has a considerably thicker rind. It often lacks the bitterness characteristic of grapefruit, although some pummelo varieties have highly unpleasant flavors. At Riverside, pummelos ripen earlier than grapefruit. In the Orient, the pummelo flesh apparently develops greater firmness than in California, and the juice vesicles can be eaten out of hand, even after removal of the segment membranes. At the University of California Citrus Experiment Station, Riverside, a collection of some fifty pummelo varieties, mostly obtained through the United States Department of Agriculture, Bureau of Plant Introduction, has been maintained since about 1932. Under Riverside climatic conditions, most of these varieties have not been particularly promising. A few become good-flavored by March or April, some eleven months after flowering, but nearly all show severe fruit drop by that time, particularly during periods of high winds, which usually occur one or more times during the winter season. All the varieties have contained many seeds in the mixed plantings at the station, although in southeast Asia, fruits with few seeds are produced under some conditions. In the United States, the seediness and firmness of the pummelo reduce its suitability for eating by halves with a spoon, as grapefruit are eaten. Likewise, it is not suitable for juicing. It serves best as a specialty fruit, to be eaten by slices out of hand, in salads, or fruit cups. By cutting pie-shaped or tangential sections, one can largely avoid the seeds and core. Unlike most