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  • Author or Editor: J. O. Kuti x
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Flavonoid content and antioxidant activity in peel and pulp samples of four different cactus pear fruit varieties were investigated. Major cactus fruit flavonoids were quercetin, kaempferol, and isorhamnetin. Greater amount of quercetin was found in the pulp compared with the peel samples in all varieties examined. Both kaempferol and isorhamnetin were found in at least three of the varieties (Opuntia ficus-indica; O. lindheimeri; O. streptacantha) exclusively in the peel samples. Generally, pulp tissue samples of all the cactus fruit varieties contained greater ascorbic acid, glutathione, alpha-tocopherol and beta-carotene and antioxidant activities than the peel tissue samples. Total flavonoids correlated well with antioxidant activity (r 2 = 0.89). Ascorbic acid had the highest antioxidant activity, followed by glutathione, beta-carotene, and alpha-tocopherol on equimolar basis.

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Freezing temperatures limit areas in which prickly pears (Opuntis species) can be cultivated for their fruits and nopals. Inheritance of cold tolerance was investigated in three cultivated species ofOpuntia. Parental, F1, backcross and F2 populations from crosses between O. ficus-indica (accession #1271),O. lindheimeri (accession #1348) and O. robusta (accession #1241) were used. Plants were evaluated for cold tolerance by the conductivity method after 3 hrs in a growth chamber at temperatures ranging from 0° to -15°C and acclimation at 10°/5°C (day/night) for 14 days. Means of each genetic population were calculated and broad and narrow sense heritability estimates were determined. The heritability estimates were generally low with evidence of small additive effects and large environmental effects.

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Callus induction in 12 genotypes of faba bean (Vicia faba L.) genotypes from Egypt were examined. Cotyledon, leaf petiole, and stem explants were cultured on two basal agar media; Murashige and Skoog (MS) and Gamborg (B5). The media contained 0.5 mm 2,4-D, 0.25 mm NAA, and 30 g of sucrose/L. Calli were easily formed in B5 media and induction rate was significantly dependent on the genotype. The highest induction rates occurred mostly in genotypes from Assiut Univ., Egypt, and in a local variety `Goya'. These callus cultures will be used for in vitro screening of the faba bean genotypes for tolerance to salt and drought, respectively.

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The use of protein profiles and isozyme banding patterns as genetic markers in cultivated Opuntia species was investigated using SDS-PAGE and spectrophotometric analysis of seeds and stem (cladode) tissues. Twenty morphologically different entries belonging to six Opuntia species were analyzed for total protein profile and three enzyme systems (superoxide dismustase [SOD], phosphoglucomutase [PGM] and UDPG ppase). Seed proteins, mostly low molecular weights, were 3-fold that of cladode proteins. Marked differences in protein molecular weight were found among the entries. PGM activity, found only in the cladode tissues, differred among the entries. No UDPG ppase activity was found in either seeds or cladode tissues. Within the entries surveyed, identical SOD banding patterns were observed indicating some degree of similarity among the species. The preliminary results suggest that isozyme and protein profiles can be used as markers in genetic studies of cultivated Opuntia species.

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Abstract

Five parental cultivars of muskmelon (Cucumis melo L.) and 16 F1 hybrids, including six reciprocals, were evaluated in a diallel design for reaction to inoculations with Myrothecium roridum and its phytotoxic metabolite roridin E using a detached leaf screening test. Analyses of variance revealed genetic variability for tolerance to the fungus and to the toxin; the correlation coefficient between inoculations with the pathogen and the toxin was 0.94. Disease and toxin tolerance were associated with highly significant general combining ability (GCA) effects, but specific combining ability were significant only for inoculations involving the pathogen. The GCA component accounted for 95.8% of the genotypic variation for pathogen tolerance and 99.3% for toxin tolerance. Reciprocal effects were not present in either set of inoculations.

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Abstract

The reactions of 50 cultivars and breeding lines of muskmelon (Cucumis melo L.) to inoculation with a pathogenic strain of Myrothecium roridum Tode ex Fries were evaluated using detached leaf tissues from greenhouse plants and immature fruits from field-grown plants. Leaf susceptibility was characterized by chlorosis, necrosis, and extensive fungus sporulation, whereas fruit susceptibility was evidenced by host tissue decay and fungus sporulation. Differences in reactions among muskmelon cultigens using detached leaves were consistent among tests and correlated well with susceptibility of young, immature fruits. Tolerance appeared to decrease with increasing physiological age of the immature fruits. ‘Hales Best’ exhibited the greatest tolerance, whereas ‘Summet’ was very susceptible.

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Guayule (Parthenium argentatum Gray) is a promising alternative to rubber tree (Hevea brasiliensis Muell. Arg.) for production of natural rubber in semiarid regions. For guayule to be commercially viable, substantial improvement in rubber yield is needed. Field studies were conducted on a dryland site in south Texas to evaluate productivity of selected guayule genotypes from Arizona and California. After 34 months of growth, no significant differences (p= 0.05) were found among the genotypes for rubber yield. However, rubber yields for most of the genotypes increased more than 3-fold from that of last year (1992) yields. Genotype `N9-5' from Arizona had the highest yield (1,239 kg ha-1). Survivability of the genotypes has progressively decreased over the years and survival rates for this year (1993) ranged from 48-25%.

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Relative water usage of four species of container-grown woody ornamental shrubs (Buxus japonica (Japenese boxwood), Leucophyllum frutescens (Texas sage), Ligustrum japonica (ligustrum) and Pittosporum tobira wheeleri (dwarf) pittosporurm)), normally used for home landscaping in south Texas, were evaluated by comparing water consumption and frequency of watering with growth rates and horticultural quality after six months growth in containers. Growth rates were determined by the difference in plant height and leaf area from the control unwatered plants and were used to characterize the suitability of ornamental shrubs for xeric landscapes. While frequency of watering had no significant effects on plant height, only ligustrum and dwarf pittosporum plants watered on weekly basis showed positive change in leaf area. There was considerable leaf regrowth in Texas sage plants after initial leaf loss. Of all the shrubs tested, dwarf pittosporum plants watered biweekly used less water to maintain their horticultural quality.

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Guayule shrub (Parthenium argentatum Gray) is a source of natural rubber resin and latex. Because guayule does not produce natural antioxidants, considerable amounts of rubber and resin are lost after harvest. The effect of long (2–7 years) cold storage on postharvest stability of rubber and resin contents in selected dryland guayule breeding lines were compared. While most genotypes tested showed significant decline in rubber and/or resin content during the storage, few genotypes consistently maintained or increased the amounts of rubber or resin content during storage. The mechanisms of postharvest degradation or synthesis of rubber and resin in harvested guayule plant materials need to be studied further.

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