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Abstract

Multiple cropping systems are characterized by high plant species diversity, closed cycling of nutrients, reduced pest incidence, erosion control, low but stable yields, and an intensive exploitation of limited land resources. Used on small farms in Latin America for centuries, bean-maize systems provide a source of income and a balanced diet for the farm family. Limited technology has reached this sector of the agricultural population, and new research reveals an impressive potential for improving yields in the bean-maize cropping system.

The current national trends in nutrition have resulted in a very high interest in the benefits of proper diet. It is very apparent that adding foods high in antioxidants to the human diet can have drastic affects on human health by reducing the risk of cancer, cardiovascular and pulmonary disease, as well as age-related degenerative diseases. It is well-known and well-documented that spinach is one of the very best vegetables in antioxidant potential. It is high in beta-carotene (provitamin A) and is also very high in lutein (a carotenoid that is a strong antioxidant but with no vitamin A activity). Lutein has also been documented to have the potential to significantly reduce macular degeneration in humans when added to the diet on a regular basis. With these health benefits in mind the Univ. of Arkansas is releasing the spinach breeding line that has been tested as 88-310. It is a slow-growing semi-savoy that exhibits excellent color and has a moderate level of white rust resistance. It has excellent plant type, producing a very attractive compact rosette plant that is very desirable for root cut whole plants or for various types of clipped spinach. It is best-suited to both fall and overwinter production in Arkansas and for winter production in the Texas wintergarden. Seed for tests can be obtained by contacting T.E. Morelock, Dept. of Horticulture, Univ. of Arkansas, Fayetteville, AR 72701.

Studies have been underway to evaluate the genetic variation in iron nutritional quality of the green leafy vegetable Amaranthus. Initial screening of 35 lines of amaranth from 12 species indicated wide variation in total iron, and small, but significant, differences in bioavailable iron, as determined by an in vitro assay. To verify if the differences in bioavailable iron detected by the in vitro assay were biologically significant, two lines of amaranth, A. tricolor Ames 5113 and A. hypochondriacus Ames 2171, were evaluated using a hemoglobin repletion assay in rats. Weanling Sprague-Dawley rats were made anemic by feeding an ironfree casein-based diet for 4 weeks. The anemic animals were fed treatment diets in which all Fe was provided by the amaranth lines. Hemoglobin levels were measured at the start and end of the treatment period to determine bioavailability. Although A. tricolor contained a higher concentration of total iron (670 ppm), the bioavailability of this iron to rats was lower than from the A. hypochondnacus line (total Fe = 210 ppm). Similar amounts of either amaranth line added to the diet produced similar changes in hemoglobin, although total iron concentrations were significantly different, confirming results observed with in vitro assays.

Abstract

Semi-purifled extracts of phenolics from foliage of tomato (Lycopersicon esculentum Mill.) inhibit larval growth of the fruitworm, Heliothis zea (Boddie), when added to artificial diets for this insect pest. The degree of inhibition of growth (dose-response) is directly related to the quantity of total phenolics in extracts added to diets, whether the extracts are of equivalent amounts of foliage from different cultivars or of foliage pooled from several cultivars added in serial dilution. Dose-responses for extracts were equal to those obtained with pure chlorogenic acid or rutin, major phenolic constituents of tomato foliage. Also, equivalent quantities of phenolics from 5 different cultivars inhibited larval growth equally when added to diets. These 3 sets of observations show that isolated tomato foliar phenolics affect H. zea larvae quantitatively, with no measurable qualitative differences between cultivars. When 2nd instar larvae were reared on excised leaflets from several cultivars of field-grown tomatoes, significant differences in larval growth between cultivars were obtained, which were consistent through two years. However, significant relationships between foliar phenolic content and larval growth were not obtained, partially because of the highly variable nature of phenolic content within and between plants. Our results suggest that phenolics in tomato foliage at the minimum contribute a substantial background level of antibiosis to H. zea.

Abstract

Horticultural crops play an important role in meeting the needs of man for vitamins and minerals. The serious problem of calorie-deficient diets can be relieved by many horticultural crops, although most of the world’s food energy is derived from grains. It is generally accepted that the most serious problem of underfed people in the less developed countries is one of protein-calorie malnutrition, particularly in infants, young children and pregnant and lactating women (1, 6). What part do horticultural crops play or what part might they play in closing the protein gap?

Abstract

Leaves of Lycopersicon hirsutum Humb. & Bonpl. and L. hirsutum f. glabratum C. H. Mull, contained a factor highly antibiotic to tomato fruitworm, Heliothis zea (Boddie), larvae. The factor was extractable with ethanol and lethal to larvae fed on an artifical diet containing the extract. The antibiotic factor appeared to be inherited recessively. Because the early instars of H. zea larvae on tomato, L. esculentum Mill., plants depend on leaf tissue rather than fruit as a primary food source, this antibiotic factor may be a valuable source of resistance for commercial cultivars.

Sweetpotato resin glycosides were purified by HPLC methods. Most allelopathic potential could be explained by these compounds. Fifty percent inhibition (I₅₀) of seed germination was obtained for redroot pigweed at 160 ppm, for velvetleaf at 13 ppm and for prosomillet at 11 ppm. Seed of the congeneric species I. purpurea was not sensitive. Growth of yellow nutsedge was drastically reduced, the I₅₀ for shoot growth was 30 ppm, for number of roots 36 ppm, and for total root length 19 ppm. The glycosides accounted for approximately half of the total fungicidal activity of all extract fractions when tested on Fusarium oxysporum pv. batatae. At 2 mg per ml, the glycosides inhibited hyphal growth by 31%. This concentration is less than 10% of the glycoside concentration in dry periderm tissue of `Regal'. The purified glycosides were incorporated into a meridic diet for diamondback moth larvae. All observed antibiosis was caused by the glycosides; the LD₅₀ was 7.2 mg per ml diet. At that concentration the surviving larvae showed a weight decrease of 46%.