Amaranths are easy to grow and reasonable yields can be produced even in poor soils (Afolabi et al. 1981, Dean 1986, Uzo and Okorie 1983). Amaranths have few insect pest problems (Afolabi et al. 1981, Dean 1986), but damping-off of seedlings by species of Pythium is a problem that plagues producers and breeders (National Research Council 1984).
Leaves of vegetable amaranths are nutritionally significant sources of betacarotene (National Research Council 1975). There have been concerns about the presence of oxalates in vegetable amaranths which can bind calcium and so lower ionic calcium concentrations in the blood, leading to hypocalcemia. Oxalates can comprise 0.2-11.4% of the dry matter in vegetable amaranths (Teutonico and Knorr 1985), but levels of oxalates are significantly reduced by steaming or boiling leaves for ten minutes, which does not significantly reduce nutrient levels (Stafford et al. 1976).
The objectives of our investigation were to identify vegetable amaranth cultivars which possess: high productivity in the summer in the deep South, high levels of resistance to Pythium damping-off, high levels of betacarotene, low levels of oxalates, and acceptable taste characteristics.
|'Ibondwe'||A. dubius||West Africa|
Resistance to Pythium damping-off was evaluated with a strain of P. myriotylum isolated from a diseased amaranth seedling and maintained on a modified form of Mitchell's CPV agar (Mitchell 1975). Oospores were produced on oatmeal agar while incubating for at least one week at 23-26deg.C in the dark- Free oospores were obtained by using a modification of the isolation of Ruben et al. (1980). A concentration of 1x107 oospores per liter which resulted in 50% mortality of the controls was used in the screening process. In a greenhouse study, 50 seedlings of each amaranth were challenged with 0.5 ml of the oospore suspension and dead seedlings determined after six days.
Betacarotene content was evaluated for spinach (Spinacia oleracea 'Bloomsdale Long Standing') and the amaranth cultivars based on the method of Jensen and Jensen (1971). Oxalate content was determined by a modification of the chromatographic method of Newton et al. (1986). A panel of 20 semi-trained taste judges evaluated vegetable amaranth cultivars, spinach, and mustard greens (Brassica juncea) which had been cooked in salted water for five minutes.
Uzo, J.O. and A.U. Okorie. 1983. Amaranthus hybridus: a potential grain crop. Nutr. Rpt. Intern. 27:519-524.
|Entries||Productivity (t/ha)||Pythium resistance (% mortality)||Betacarotene content (mg/g fresh wt)||Oxalate content (µg/g)||Taste test (1 unacceptable-10 acceptable scale)|