Starch and Sugar Accumulation in Two Accessions of Lycopersicon cheesmanii
| Autor: | John D. Hewitt, T. Casey Garvey |
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| Rok vydání: | 1991 |
| Předmět: | |
| Zdroj: | Journal of the American Society for Horticultural Science. 116:77-79 |
| ISSN: | 2327-9788 0003-1062 |
| DOI: | 10.21273/jashs.116.1.77 |
| Popis: | A study using Lycopersicon cheesmanii Riley LA 1449 (typicum), a low soluble solids content (SSC) acces- sion, and L. cheesmanii f. minor LA 528 (minor), a high SSC accession, was undertaken to characterize the accu- mulation of starch, sugar, and total SSC. Fruit of each accession was sampled throughout development to identify differences in SSC, starch accumulation, and sugar distribution. Osmetric analysis indicated that the minor race had higher SSC content throughout the ontogeny of fruit development than the typicum. Typicum contained more starch than minor, and both accessions showed a rapid decline in percent starch as the fruit ripened. Sucrose remained low throughout all stages of fruit development for both accessions. Glucose increased in the minor and declined in the typicum. Fructose increased in both accessions. Total reducing sugar content at the full ripe stage was higher in minor than the typicum. A survey of 30 accessions of Lycopersicon cheesmanii from the Galapagos Islands revealed that L. cheesmanii f. minor had a higher soluble solids content than L. cheesmanii typicum (Garvey and Hewitt, 1984). This difference prompted a series of devel- opmental studies to analyze factors governing SSC content in the two races of L. cheesmanii. Starch accumulation followed by hydrolysis to reducing sug- ars has been proposed as a mechanism contributing to high SSC (Walker and Ho, 1978; Yelle et al., 1988). Cultivated tomatoes that have higher total SSC when fully ripe were shown to have higher starch levels during early fruit development (Dinar and Stevens, 1981). Walker and Ho (1977) reported that starch and other insoluble are formed from the soluble sugars in the fruit, and a correlation was found between the rate of carbon import and the formation of insoluble residues. Fruits with the highest carbon import rates also had the greatest starch accumulation (Walker and Ho, 1977). Furthermore, there was an increase in reducing sugar levels accompanying the breakdown of starch (Davies and Cocking, 1965; Davies and Hobson, 1981). Walker and Ho (1977) re- ported that sucrose was a principal transport assimilate but that its level in cultivated tomato fruit remained low. Developmental studies of the tomato revealed that fructose and glucose were accumulated rather than sucrose (Davies, 1966; Davies and Kempton, 1975) in the mature fruit. Experiments with 14 C in- dicated that sucrose was hydrolyzed to reducing sugars once inside the tomato fruit (Walker and Ho, 1977). Representative accessions of each race of L. cheesmanii, sam- pled throughout fruit development, were used in the present study to identify differences in SSC, starch accumulation, and sugar distribution. |
| Databáze: | OpenAIRE |
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