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.
Seeds and cladodes (stems) of cultivated Opuntia species were analyzed for fatty acids using gas chromatography. The major fatty acids found in the cladode tissues were myristic (14:0), palmitic (16:0), stearic (18:0), arachidic (20:0), and behenic (22:0). The seeds contained predominantly palmitic, stearic, and behenic acids. Significant differences, both in content and composition of fatty acids, exist among the species so that fatty acid profiles may be useful as taxonomic markers for the differentiation of cultivated Opuntia species.
F. Nekouei and J.O. Kuti
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.
J.O. Kuti and C.M. Galloway
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.
J.O. Kuti, G.V. Latigo and J.O. Bradford
Soil-borne pathogens such as Macrophomina phaseolina (the causative agent of charcoal rot) and Phymatotrichum omnivorum (the causative agent of cotton root rot) contribute to mortality of transplanted guayule (Parthenium argentatum, Gray) seedlings in southern Texas. In order to select guayule genotypes for resistance to these pathogens, it would be useful to develop reliable greenhouse inoculation procedures for screening guayule seedlings. Twelve-week-old guayule seedlings (`11591', a USDA standard breeding line) were inoculated using two inoculation methods (soil-drenching and root-dipping) in two soil media (field soil and commercial soil mix). Plants were rated for disease severity 2 to 5 months after inoculation and pathogens were re-isolated from diseased plants to establish Koch postulates. The soil drenching technique, using field soil, caused rapid development of disease symptoms that were consistent with re-isolation frequencies of pathogens from the diseased plant tissues.
G.V. Latigo, J.R. Smart and J.O. Kuti
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%.
E.C. Boehm, T.D. Davis and J.O. Kuti
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.
G.V. Latigo, J Smart, J.O. Bradford and J.O. Kuti
Guayule (Parthenium argentatum Gray) is a promising alternative to (Hevea brasiliensis Muell. Arg.) for rubber production in semiarid regions. Substantial improvement in yield is needed to establish guayule as a competitive source of natural rubber. A 4-year field study was conducted on a dryland site in southern Texas to evaluate productivity of selected guayule breeding lines from Arizona and California. Plants were harvested at the age of 22, 34, and 46 months and analyzed for dry weight, resin content, rubber content, resin yield, rubber yield, and percent mortality. While significant differences (P = 0.05) were found for dry weight, resin content, and rubber content within the harvest dates and among the guayule lines, no significant differences were found for rubber content between the harvest dates for each genotypes. Phytomass was highly correlated (r = 0.94) with rubber yield. Survivorship of all the guayule lines decreased progressively over the experimental period and mortality rates ranged from 38% to 67 %. Guayule lines `UC102' from California and `N6-5' and `P3-1' from Arizona were ranked highest for all traits measured.
C.D. Grote-Flores, G.V. Latigo, J.O. Bradford and J.O. Kuti
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.