Carrot tissue cultures, germinating seed, and dry seed were exposed to gamma radiation. Irradiation accelerated germination of carrot seed in the M1 generation at low doses (0.5 and 1 krad), whereas higher doses delayed germination. A high negative correlation was observed between dose and survival of plants after seed irradiation. Plant size and root weight were 20 % to 35% greater than control plants after seeds, but not tissue cultures, were exposed to low doses of gamma irradiation. Higher doses reduced M1 plant size by >50% in germinating seed and tissue culture treatments but less for the dry seed treatment. Seed production decreased while phenotypic variation of M1 plants increased with increasing gamma ray dosage. Root weight and total dissolved solids were highly variable in M2 families. Less variation was observed in total carotene content and none was seen in sugar type (reducing vs. nonreducing sugars). Induced variation in root color and root shape was also observed. Irradiation of germinating seed and tissue cultures yielded more M2 variation than irradiation of dry seed. Putative point mutations were not observed. Unirradiated carrot tissue cultures did not yield significant M2 somaclonal variation. Average root weight of M2 plants increased with increasing gamma ray dosage, especially for the dry seed treatment.
Abstract
Successive plantings were made from August through October in southeastern Florida to compare plant establishment methods and their effects on stand establishment, plant growth, and maturation (time to anthesis) of bell pepper (Capsicum annuum L.). Direct-seeding treatments were germinated seeds planted in potassium starch acrylamide (PSA) gel, magnesium silicate clay (MSC) gel, plug-mix, MSC gel mix, PSA gel mix. Nongerminated seeds were covered with soil or plug-mix. Three types of containerized transplants were used for comparison of earliness to flowering. Regardless of planting date, the PSA gel mix treatment generally led to earlier emergence and more uniform plant stands compared with the other direct-seeding techniques tested. Fluid drilling with PSA (without plug-mix) typically led to reduced plant stands, whereas all other direct-seeding methods did not differ in stands. Plant dry weights were increased as much as 100% when seeds were sown in PSA gel mix rather than with other seeding treatments. Plants established by transplanting began flowering at least 16 days earlier than plants established via direct seeding. Direct-seeding germinated seeds in PSA gel mix or plug-mix led to earlier, more uniform anthesis than sowing nongerminated seeds in soil.
Application of DCPTA as a pregermination seed treatment (DCPTA plants) increased the seedling vigor, relative growth rate, harvestable yield, and yield quality of processing tomato (Lycopersicon esculentum Mill. cvs. UC82, VF6203, H100). When compared with controls, the growth rates of roots and shoots of 30 μm DCPTA plants were increased significantly (P = 0.05) during seed germination and midexponential growth. At fruit harvest, greenhouse-grown 30 μm DCPTA plants showed a 2- to 3-fold increase in leaf, stem, and root dry weight compared with that of controls. Improvements in the uniformity of fruit maturation significantly increased the harvestable fruit yields of greenhouse-grown DCPTA plants compared with that of controls. The total soluble solids (oBrix), glucose, fructose, and carotenoid contents of red-ripe fruits harvested from greenhouse- and field-grown DCPTA plants were significantly increased compared with controls. Chemical name used: 2-(3,4-dichlorophenoxy)triethylamine (DCPTA).
Some apple cultivars are biennial. Experiments with the facultatively parthenocarpic apple cultivar `Spencer Seedless' indicated that seeds are responsible for inhibiting flowering (Chan and Cain, Proc. ASHS 91:63-68, 1967). Because gibberellin inhibits flowering in apple, seed GAs may be responsible for biennial bearing, or seeds may affect metabolism of GAs in bourse shoots. To obtain additional information, 14C - G A12 was injected into seeds or bourse shoots of `Spencer Seedless' and the metabolites were extracted after 24 or 48 hr. Metabolites moved from seeds to bourse shoots and vice versa in 1992, only the most polar compound(s) being transported. However, transport was not observed in 1993. Five metabolites of 14C - G A12 were found in apices following injection, 5 to 7 in seeds. Two metabolites occurred in fruit flesh following seed treatment. The presence of seeds appeared to have no qualitative effect on metabolism in the bourse shoot, although the metabolites have not yet been identified.
One-year old `Coho' spinach seeds (Spinacea oleracea L.) were primed, air-dried, and germinated for 12 days to determine the effects of multi nutrient liquid chelate compound (Crop-Up) and its single nutrient chelate components on the germination performance of old seeds. Treatments consisted of Crop-Up, Ca, Mg, Mn, Fe, Zn, Cu, and B chelate solutions at concentrations of 5, 0.25, 0.11, 0.28, 0.25, 0.34, 0.10, and 0.05%, respectively. Distilled water was used for the check. Crop-Up-, Fe-, Zn-, and Cu-priming significantly increased both seedling fresh and dry weights, and improved seed germination by 23 to 32% over the check treatment. Al1 nutrient treatments, except Cu, had a delaying effect on time of emergence. Fe-, Zn-, and Cu-priming treatments increased germination performance index by 21, 11, and 9%, respectively.
Shrunken-2 supersweet (sh2) sweet corn is susceptible to preemergence damping-off caused by Pythium ultimum, especially when planted into cold soil. Bio-priming, a seed treatment which combines the establishment of a bioprotectant on the seed with preplant seed hydration, was developed to protect seeds from damping-off.
In a series of field experiments conducted in Montana's Bitterroot and Gallatin Valleys, bio-priming or seed bacterization with Pseudomonas fluorescens AB254 protected sweet corn from P. ultimum damping-off. Bio-priming corn seed with P. fluorescens AB254 was comparable to treatment with the fungicide metalaxyl in increasing seedling emergence. Seedlings from bio-primed seeds emerged from the soil more rapidly than from nontreated seeds and were larger at three weeks postplanting. Seeds of sh 2 and sugary enhancer (se) sweet corn, as well as that of several sh 2 cultivars, were protected from damping-off by bio-priming.
Seedling emergence from primed and nonprimed sugar beet seed (Beta vulgaris L.) was studied for 3 years under field conditions near Kimberly, Idaho, and compared with germination or emergence under controlled laboratory conditions. Maximum seedling emergence did not vary with seed treatment in spite of low field soil temperatures. Time to 50% of maximum emergence was significantly less for seed primed with polyethylene glycol 8000 than for nonprimed seed in only 1 of 3 years. Seed soaked in 30C water for 24 h performed similarly to nontreated seed in the field, but their maximum emergence was significantly improved compared with primed seed in one of two laboratory experiments. Time to 50% of maximum germination was improved by priming with or without a warm water soak in one of the two laboratory experiments.
Cabbage (Brassica oleracea L. Capitata) was direct-seeded with a precision seeder or with a bulk seeder. Treatments with the bulk seeder consisted of blending viable, hybrid cabbage seed with nonviable, open-pollinated seed at several ratios to reduce the cost of planting hybrid seed. The study demonstrated that farmers with small acreages can obtain equivalent net income per acre using bulk seeders compared to using more expensive precision seeders. The study also showed that the additional cost per acre of a precision seeder is small compared to other input costs (for the acreage assumptions used here). Low percentages of hybrid seed in the bulk seeder (10% to 50%) were not economical. Precision seeding to a stand reduced the need for thinning labor and resulted in equivalent yields and net income.
In field experiments, bio-priming and coating with Pseudomonas fluorescens AB254 consistently protected sweet corn (Zea mays L.) seeds from preemergence damping-off caused by Pythium ultimum Trow. The bio-priming seed treatment was evaluated under various disease pressures and with seeds of three sweet corn genotypes: shrunken-2 supersweet (sh-2), sugary enhancer (se), and sugary (su). While no damping-off occurred in the su sweet corn, bio-priming protected sh-2 and se sweet corn seeds at a level equivalent to that obtained by treatment with the fungicide metalaxyl. Biopriming increased seedling height of all three sweet corn genotypes at 4 weeks post-planting. Coating of sweet corn seeds with P. fluorescens AB254 provided an equivalent degree of protection from damping-off under all but the most severe conditions.
Abstract
Seeds of black locust (Robinia pseudoacacia L.), common honeylocust (Gleditsia triacanthos L.), and Kentucky coffeetree (Gymnocladus dioica L.) were coated with an adhesive plus hydrophilic gel, adhesive only, or neither (control), planted in sand in the greenhouse, and then irrigated at 3-, 6-, or 9-day intervals. Percent germination of black locust seeds irrigated at 3-day intervals was decreased significantly with exposure to hydrophilic gel. Gel-coated Kentucky coffeetree seeds irrigated at 6-day intervals also had a percent germination significantly lower than those treated with adhesive alone, but germination of untreated seeds was not different from adhesive- or gel-coated seeds. No other significant difference in germination percentage was observed. Seedling heights and dry weights were not affected by seed treatment; however, decreased moisture availability because of longer time periods between irrigations tended to delay emergence and reduced seedling vigor.