Search Results
Abstract
Tolerance of carrot seeds (Daucus carota L.) to heat treatments that could eradicate seedborne pathogens was investigated. Germination and emergence of seedlings from seeds treated in hot water at 35, 40, 45, 50, or 55C from 4 to 20 min were not affected, but seeds treated at 60C for 8 min or more were affected adversely. At 45 and 50C, treatment durations as long as 48 min did not affect emergence, but >20 min at 55C reduced emergence. Similar results were obtained when seeds were treated at the same temperatures in water containing 1.1% sodium hypochlorite (NaOCI). Emergence of seeds treated in hot water or 1.1% NaOCl and planted within 5 days generally was similar to that of treated seeds stored for 90 days at 20C in 60% RH before planting. Any existing differences were small and not clearly related to temperature–duration treatment combinations. Percent emergence from seeds of 19 out of 25 hybrid cultivars treated at 50C for 15 min was reduced by an average of 2.9%, but differences for untreated seeds ranged from −13.3% to +4.8%. Emergence from hot water-treated seeds was reduced after 6 weeks of storage at 70% and 80% RH, but not at 20% to 60% RH. Prolonged treatment and the higher temperatures were particularly effective in reducing populations of seedborne Alternaria dauci.
Abstract
Effects of soil compaction on early root growth of carrot (Daucus carota L.) growing in organic soil contained in specially constructed pots were studied under controlled environmental conditions. Screened and steamed mucky peat soil was artificially compacted with an applied pressure of 0.45 — 2.23 bars to produce soil densities of 0.7 — 1.1 g/cm3. Soil strength, measured as penetrometer resistance was directly related to applied compacting pressure and highly dependent upon soil moisture. Highest soil strengths were produced when the soil contained 52-58% moisture. Taproot lengths 16 days after seeding were significantly shorter at each increase in soil strength produced by applied compacting pressures of 0.45, 1.12, 1.51, and 2.23 bars. Rates of early taproot growth measured at 2-day intervals for 18 days were similarly decreased with increasing soil strength. Young taproots grew normally through compaction zones produced by 0.45 bars but were severely impeded when compaction zones produced by 1.12, 1.51, and 2.23 bars were encountered. Roots impeded by high soil strength were frequently thickened and convoluted with increased branching but no significant differences between treatments could be detected. Effects of soil compaction on mature roots were evidenced by abnormally short, blunt, and abruptly tapered roots. Mature root weight, diameter, and length decreased with increasing soil compaction.
Abstract
Effects of water saturation of the soil on early root growth of carrot (Daucus carota L.) were studied using specially designed pots containing organic soil. Water saturated soil conditions were created by raising the water table to envelop actively growing carrot root tips on the 6th day after planting pre-germinated seed. Water saturation was maintained for intervals of 12 hours to 7 days. Sixteen days after seeding (DAS), taproots subjected to as little as a 12 hour period of water saturated soil at 6 DAS were significantly shorter and exhibited more discolored root tips and forked roots than roots growing under normal moisture conditions. After 78 days of growth, the roots subjected to water saturated soil at 6 DAS were significantly shorter, weighed less, and were smaller in diameter than controls. The height of the carrot tops was not affected by treatments.
Abstract
Early root growth of carrots (Daucus carota L.) was studied in specially constructed pots containing organic soil under controlled environments at 16°, 20°, 24°, and 28°C. Carrot tops produced greater amounts of bio-mass on a fresh or dry weight basis than did roots, whereas taproots demonstrated faster rates of linear growth than did the tops throughout the 24-day sampling period at all temperatures. The optimum range of temperatures for carrot root growth was 20-24°C. Taproots reached the potential length for market-acceptable storage roots (15.2 cm) between 12 and 16 days after planting at 20°, 24°, and 28°C and after 20 days at 16°C. Average taproot lengths after 24 days at 16°, 20°, 24°, and 28°C were 23.6, 38.5, 35.6, and 16.7 cm, respectively. Secondary roots had developed by the 8th day and tertiary roots by the 20th day. Tertiary roots were confined to the upper 5 cm of the root system at this early date.
Abstract
The open pollinated carrot (Daucus carota L.) ‘Beta III’ was released and widely distributed in 1986, primarily for its value as a garden cultivar and for an improved source of carotenes for providing vitamin A. It is a promising population for breeders to extract inbred lines for improved hybrids.
Abstract
Hybrid carrots (Daucus carota L.) are gaining a larger share of the market once devoted exclusively to open-pollinated cultivars. The carrot inbred Florida 524 has been used extensively as the male parent in experimental hybrids tested in Florida, California, Wisconsin, Texas, and Arizona. These trials have revealed that Florida 524 has good combining ability for fresh market characteristics. Florida 524 is being released jointly by the University of Florida and the U.S. Department of Agriculture.
Abstract
Flavor is an important factor in establishing consumer preference of carrots. Although harsh, strong flavor frequently occurs in available cultivars, the dominance of mild flavor in hybrids from harsh and mild parents suggests that carrot flavor can be improved rapidly when mild-flavored inbreds are available (1). Carrot inbred B2566 has been selected as a source of improved flavor and was used as a male parent in experimental hybrids tested in California, Florida, and Wisconsin. B2566 has demonstrated good combining ability for important fresh market characteristics of color, shape, and seed productivity along with desirable mild, sweet flavor and succulent texture. Because of these qualities, B2566 is being released jointly by the USDA, the Univ. of Florida, and the Univ. of California.
Abstract
Carotenes from vegetables and fruits are vitamin A precursors that contribute about half of the vitamin A in the U.S. diet (3) and two-thirds of the world diet (5). Carrots typically contain 65 to 90 ppm carotenes (1) and are estimated to be the major source of carotene for U.S. consumers (3). Few pro-vitamin A sources surpass the carotene content of typical carrots, although red palm oil can contain >825 ppm carotenes (2). Genetic selection for higher carotene levels in carrots could increase the dietary consumption of carotene and consequently vitamin A. A high carotene mass carrot population was developed for use in breeding, genetic, and biochemical studies of carrot (Fig. 1).