Primed, pregerminated, or nontreated seeds of bell pepper (Capsicum annum L.) `Early California Wonder' were grown in controlled conditions for 14 days in glass tubes containing a gel medium. The number of basal roots (one per plant), lateral roots (one per plant), and taproot length (64 mm) did not differ between seed treatments 14 days after seeding. Roots of seedlings from nontreated seeds weighed more than seedlings from primed seeds, and the seedlings had smaller shoot: root ratios than those from pregerminated or primed seeds. Seedlings from pregerminated seeds had heavier and taller shoots than seedlings from nontreated or primed seeds. Taproot length from 1 to 6 days after radicle protrusion increased linearly for all seed treatments. Seedlings from pregerminated seeds initially had longer taproots but had slower linear taproot growth up to 6 days after seeding than seedlings from nontreated or primed seeds.
Seed treatments and soil covers were used to assess stand establishment and uniformity of direct-seeded cabbage (Brassica oleracea L. var capitata) under high and low soil temperatures. Generally, primed seeds did not result in increased or more uniform seedling emergence compared to untreated seeds. Germinated seeds sown with a magnesium silicate gel (Laponite) or a starch-acrylamide-acrylate polymer gel (Liquagel) resulted in incomplete stands under heat stress, and stands for all plantings were generally lower when cabbage seeds were sown in a gel than when sown without a gel. Peat-vermiculite (Plug-mix) and calcined clay (GrowSorb) seed covers improved stands regardless of seed treatment when average soil temperatures were ≥30°C. Under normal (25°) to cooler soil conditions stands were not improved by seed treatment or seed cover.
The rate and total emergence of lettuce (Lactuca sativa L. ‘Empire’) seedlings incubated at 33°C for 10 hr, alternating with 23° for 14 hr, was markedly increased by seed treatment with 0.5 mM fusicoccin (FC). Neither gibberellic acid (GA) nor kinetin (K) were effective in improving emergence when used alone. The combination of FC with GA or K appeared to give a synergistic enhancement of emergence rate. The radicle elongation of seedlings was reduced by seed treatment with FC, K, or combinations of FC, GA, and K in tests at 20°. The greatest reductions were caused by combinations that included FC. The inhibiting effect of FC on radicle growth was reduced by using a concentration of 0.05 mm. Treatment with 0.05 mm FC resulted in slower emergence but gave the same total emergence as 0.5 mm FC at high temperature. Both FC and GA stimulated hypocotyl elongation.
Tomato plants selected for rapid (early) emergence in several germination environments revealed small but statistically significant gains in maturity and fruit size. Even more significant was the interaction of selection time with germination environment and with entry. It was concluded that while some genetic gain might result from seedling selection, the seeding treatments utilized in this trial would not enhance this gain. The interaction with entry indicated a lack of consistent directed response.
Irregular germination and delayed emergence of blueberry, strawberry, blackberry and raspberry seedlings have been noted by various investigators. Seed treatments such as afterripening (1) and acid scarification of strawberry seed (2) improved rapidity of germination, but neither treatment fully overcame the delay in seed germination. In a study with blueberry seed, after-ripening did not improve germination (2). Sporadic germination and delayed emergence of seedlings complicates a breeding program when uniform size of seedlings is desired.
Plantpro 45, an iodine-based compound, was evaluated as a seed treatment for management of fusarium wilt caused by Fusarium oxysporum f.sp. basilici on basil (Ocimum basilicum) in greenhouse assays and for effects on growth of the pathogen in vitro. Plantpro 45 at a concentration of 300 mg·L-1 (ppm) prevented fusarium hyphal growth in vitro. Seed treatments of 800 to 1000 mg·L-1 eliminated fungal contamination of seed and increased germination by 27% compared to the nontreated control. Basil transplants grown from seed treated with 400, 800, and 1000 mg·L-1 were significantly taller, weighed more, exhibited larger leaf area, and had reduced wilt severity in the greenhouse compared to the nontreated control. Transplants grown in soil treated with increasing concentrations of Plantro 45 had correspondingly decreased wilt severity, regardless of whether or not the seeds had been previously treated with Plantpro 45. Further research and optimization of soil and foliar applications in combination with seed treatments are needed to provide a complete program for management of fusarium wilt of basil.
A strain of the biocontrol fungus Trichoderma harzianum was tested for effectiveness in improving the performance of sh2 sweet corn using a variety of delivery methods. In greenhouse trials, Trichoderma seed treatment reduced the proportion of weak plants (unlikely to make a marketable ear) from 40% to 10%. This is evidence that the characteristically uneven stand establishment of supersweet corn should be overcome by using Trichoderma. In field trials, Trichoderma and Gliocladium (a related fungus) were inoculated as a seed treatment without fungicide in spring-tilled plots. Yields of uninoculated controls were 2.2, Gliocladium-treated were 2.6, and Trichoderma -treated were 3.6 T/ac. Delivering the same lines of fungus in the fall to a rye cover crop resulted in high populations the following spring. The cover crop was killed and fungicide-treated seed of `Zenith' sweet corn was planted without tillage. Yield with Trichoderma was 4.0, with Gliocladium was 3.7, and uninoculated was 2.4 T/at. The uninoculated, conventionally-tilled plots also yielded 4 T/at. Thus the beneficial fungi overcame the inhibition caused by no-till. Trichoderma was delivered effectively both as a seed treatment and on a winter cover crop to improve stand uniformity and overall yield.
There are many ground covers native to Korea. Liriope spicata is very promising for landscaping purposes due to its waxy and dark-green foliage fragrant and pink flowers, as well as fruit. However, seeds harvested during late fall do not germinate at all if they are sown in spring. Thus, series of experiments were conducted to undestand the physiological mechanism of dormancy breaking and germination of Liriope spicata Lour. seeds and to determine the effective methods for enhancing seed germination. Fruit were harvested in October through December. Depulped seeds germinated rapidly, indicating that one or more inhibitors may be present in the pulps of fruit and/or seeds. GA3, NaOCl, NaOH, and H2SO4 treatments and dry cold treatment had no effect on germination, whereas wet, cold seed treatment for at least 30 days promoted germination up to 75% within 15 days. Optimum conditions for germination was continuous dark and 25/20 °C alternate temperature conditions. Extracts from pulps and seeds showed a strong inhibition effects on the germination of lettuce seeds, indicating that germination inhibitors are present in pulp and seeds. Since extracts from naked seeds did not show inhibition, inhibitory substances are thought to be present in pulp and seedcoat. Pulp and seeds were extracted with water and methanol and autoclaved at 115 °C, followed by bioassay experiments. Germination inhibitors were found water soluble and heat stable by series of bioassay experiments. Diluted extracts 4 to 8 times still maintained inhibitory effects. Optimum seed harvesting time was from 22 Nov. to 1 Dec., where seed germination was high without additional seed treatments. Total phenolic compounds and ABA contents of pulp and seeds decreased by wet cold seed treatment. Changes in total phenolic compounds and ABA in from October through December were correlated with germination during the seed development. When contents of total phenolic compounds and ABA were high, seeds did not germinate at all, while low contents resulted in good seed germination.
An experiment was initiated to evaluate the effects of previously recommended seed treatments for baldcypress [Taxodium distichum (L.) Rich.] or pondcypress [Taxodium distichum (L.) Rich. var. imbricarium (Nutt.) Croom] on Montezuma cypress [Taxodium distichum (L.) Rich. var. mexicanum Gordon], and to determine which, if any, provided optimum germination. Factorial combinations of seed treatments and stratification (2 °C for 0, 45, or 90 d) were applied to seeds of Montezuma cypress. Treatments included: 1) 90% ethanol 5 min soak, 2) ethyl ether 5 min soak, 3) 100 mg·L-1 citric acid 48 h soak, 4) mechanical scarification, 5) five hot water baths (42 °C) allowing the water to cool to room temperature between baths, and 6) a non-treated control. Three more seed treatments consisted of water soaks at room temperature (25 °C) for 0, 45, or 90 d. Seeds were germinated on moist filter paper in a growth chamber with a 12-h day/night photoperiod at a constant 25 °C. Data was collected daily for 14 d and then weekly for the following 4 wks. Radicle elongation of 1 cm was considered germination. Without stratification, 100 mg·L-1 citric acid and the hot water bath treatments were significantly different from other treatments by 7 d, though not from each other, with a mean cumulative germination of 15.6% and 12.2%, respectively. By 14 d, the 100 mg·L-1 citric acid treatment differed only from the ethyl ether wash attaining 28.9% and 14.4% germination, respectively. There were no other statistically significant differences observed among any other treatments without stratification. Germination percentages were low,<30%, without stratification. Effects of additional stratification will also be discussed.
Application of DCPTA, as a seed treatment and a foliar spray, was evaluated for effects on productivity and fruit quality of processing tomato (Lycopersicon esculentum Mill.) and fresh-market pepper (Capsicum annuum L.). Two field trials for each crop were conducted in California during 1992. No DCPTA treatment was effective in increasing vegetative growth or fresh fruit yield of either crop at any site. Total soluble solids concentration and color of tomato fruits were unaffected by DCPTA, regardless of application method. We conclude that DCPTA is not a useful production aid for field-grown tomato or pepper. Chemical name used: 2-(3,4-dichlorophenoxy) triethylamine (DCPTA).