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  • Author or Editor: Leonard M. Pike x
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Fruit of TAMU breeding line 830397 are green in contrast to the cream or orange fruit of commercial cultivars at the mature-seed stage (MS-S). Inheritance of this trait for green MS-S fruit color in Cucumis sativus was investigated. A new locus, gn, is proposed as well as the elimination of the C locus. MS-S fruit color is controlled by two major genes, R and Gn. Fruit is orange when the genotype is R_ _ and green when the genotype is rrgngn. The cream MS-S fruit color trait is incompletely dominant over green, as the genotype rrGnGn is cream while rrGngn produces mature fruit from cream to intermediate in color between cream-colored and green fruit. Spine color is pleiotropic with or very tightly linked to the R locus, but heavy netting from PI 165509 appears not to be linked with the orange genotype and is polygenic.

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Abstract

Onion growth responses to salinity levels were evaluated using five onion cultivars. In a plant growth study, eight salt levels were used with electrical conductivities (EC) ranging from 0.8 to 12.0 dS·m−1. Total area of the leaves and stem, dry weight, plant height, and leaf tip burn were measured after 45 days of growth. All five cultivars were sensitive to low salt levels, with significant reduction occurring at 1.4 dS·m−1. In a 2nd experiment germination percentage was evaluated for 8 days; a wider range of salt levels was tested (0.0–50.0 dS·m−1). Rate of germination was retarded 1–3 days with increasing salt concentrations, but germination percentage after 8 days was not significantly reduced in the 0.0–25.0 dS·m−1 salt levels. Germination was prevented at 45.0 dS·m−1 for all cultivars except ‘Texas Grano 1015Y’, which exhibited slight germination. These test results confirm that salt effects during germination are not related to later responses of the whole plant to salt. Screening onion for salt tolerance would best be done at the vegetative stage.

Open Access

Abstract

Quality was compared for short-day onions (Allium cepa L.) packed in corrugated paper boxes or conventional mesh bags when stored at 1, 15, or 24C for 3 weeks and an additional 2 weeks after transfer to a 24C holding room. It took 18 to 24 hr to equalize the air and bulb temperatures to 24C room temperature after transfer. Air temperatures in bags increased slightly faster than in boxes, but the bulb temperatures increased at the same rate. Weight loss was 2% to 4% after 5 weeks and was only slightly higher in bags. Incidence of black mold (Aspergillus niger Teigh.) was greatest at 24C continuously and was not affected by kind of container. Incidence of “slippery skin” (Pseudomonas spp.) was higher at 24C than at lower temperatures after 3 and 4 weeks, but was not affected by containers. Decay incited by Botrytis spp. occurred randomly and no sprouting was found during storage.

Open Access

A simple and fast method for measuring low boiling point (LBP) volatile terpenoids in carrots (Daucus carota L.) was developed by using a direct headspace sampling technique. Seven LBP terpenoid compounds were separated with high sensitivity and consistency via gas chromatography. High boiling point terpenoids above terpinolene were not well characterizable. Standard compounds showed highly linear responses up to 10 μg.g-1, with a detection limit of 0.01 μg.g-1. We confirmed that high α- and β-pinene and/or total terpenoids contributed to harsh or oily flavors. Up to 40 samples can be analyzed in an 8-h day using this method, compared to 10 samples using previous methods.

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`Pavo', a commercially grown, virus-susceptible squash (Cucurbita pepo L.) hybrid, and two experimental virus-resistant transgenic squash hybrids, XPH-1719 and XPH-1739, were tested for field performance. The two transgenic squash hybrids possess the desired fruit and plant characteristics of their parental line, `Pavo', plus resistance to zucchini yellow mosaic virus and watermelon mosaic virus 2 (XPH-1719), and resistance to zucchini yellow mosaic virus, watermelon mosaic virus 2, and cucumber mosaic virus (XPH-1739). Percent emergence and days to flowering were similar among the three hybrids. XPH-1719 and XPH-1739 were equally effective in producing a high percentage of quality marketable fruit and yields with 90% and 13,800 kg·ha–1 and 87% and 16,500 kg·ha–1, respectively. XPH-1719 and XPH-1739 demonstrated their outstanding virus resistance over `Pavo' by producing only 3% and 14% symptomatic plants, respectively, compared to 53% for `Pavo'. They also produced the lowest percentage of infected fruit, 0% and 7%, respectively, with `Pavo' at 26%.

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Inner scales excised from dormant bulbs of the short-day `Texas Grano 1015Y' onion (Allium cepa L.) were cultured in vitro and leaf growth was examined. Light promoted leaf growth, but no differences in leaf growth were observed for media pH between 4 and 7. Leaf growth rate in darkness was highest at 24C, reduced at 15C, and greatly reduced at SC. Kinetin promoted leaf growth at 1, 10, and 100 μm. IAA was effective at 1 and 10 μM, but not at 0.1 and 100 μm. GA3 promoted growth at 0.1 μM. No inhibitory effects of ABA on leaf growth could be detected. Chemical names used: 1-H-indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellic acid (GA3), 6-furfurylaminopurine (Kinetin).

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The relatively low evolution rate of the chloroplast DNA has made it an ideal tool to study evolutionary processes in plants above the species levels. However, recent studies have demonstrated that intraspecific variation in the chloroplast DNA is also common. This variation has provided useful insights into population level evolutionary processes. The polymerase chain reaction and sequencing of a noncoding chloroplast region used to classify onion lines for cytoplasmic type facilitated the identification of one sterile and two normal plastome variants in onion (Allium cepa L.). Sequence comparison revealed that differences between plastome variants included the presence of single-nucleotide polymorphisms associated with cytoplasmic type and variable numbers of tandem repeats, possibly resulting from slipped-strand mispairing. Our observations support the use of chloroplast-specific markers to assist in the selection of specific cytoplasmic types, suggest the potential to facilitate genotype determination, and demonstrate the presence of additional variation within cytoplasm type which gives insight into plastome evolution and may facilitate more accurate genotyping and selection.

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The aglycone, or free quercetin, and total quercetin content of 75 cultivars and selections was analyzed by reverse-phase high-performance liquid chromatography. Quercetin glycosides were hydrolyzed into aglycones. Total quercetin content in yellow, pink, and red onions varied from 54 to 286 mg·kg-1 fresh weight in different onion entries grown during 1992. White onions contained trace amounts of total quercetin. Free quercetin content in all the onions was low (< 0.4 mg·kg-1) except in `20272-G' (12.5 mg·kg-1 fresh weight). Bulbs stored at 5, 24, and 30C and controlled atmosphere (CA) for 0,1,2,3,4, and 5 months showed a most marked change in total quercetin content at 24C compared to other treatments, with a rise in mid-storage followed by a drop. Storage at 5 and 30C also demonstrated a similar change. However, total quercetin content did not vary significantly in bulbs stored at CA for 5 months. We conclude that genetic and storage factors affect quercetin content on onions.

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Limonoids, chemically related triterpinoids predominantly found in citrus and neem relatives, are known to play a pivotal role in the prevention of different types of cancer and cardiovascular diseases. Since the concentrations of these compounds are low in the plant tissues, the isolation of pure compounds is the limiting factor for the individual activity studies in animal models. In this study, combinations of chromatographic techniques were used to isolate limonoid aglycones and limonoid glucosides from citrus byproducts such as seeds and molasses. The compounds were initially extracted with different polar solvents and the concentrated extracts were passed through a series of adsorbent resin (SP-70) and ion-exchange resins (WA-30, Dowex-50, Q-sepharose) to remove further impurities. The use of increasing ionic strength of NaCl from 0 to 800 mm to release the exchanged compounds from the ion exchange columns further separated the limonoids from flavonoids, which was confirmed through TLC, UV, and analytical HPLC methods. Individual compounds were further purified using flash chromatography and preparative HPLC methods and identified by using LC-MS analysis. Direct crystallization of limonin resulted in a 17% increase in the yield as compared to the previously reported methods. The results suggest that application of these purification methods are useful for the bulk purification of compounds in order to further investigate their biological activity.

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