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- Author or Editor: D. J. Styer x
The reaction of 39 marigold cultivars to Pseudomonas syringae pv. tagetis Young, Dye & Wilkie was determined. Three new symptoms were observed in addition to large necrotic leaf spots with or without apical chlorosis: flecks and leaf spots both surrounded by chlorotic halos and apical chlorosis without leaf spots. Symptoms develop only on vegetatively growing tissue; new symptoms do not develop on mature tissue. Tall cultivars generally were more susceptible than dwarf cultivars.
The possibility of using seed adenosine triphosphate (ATP) content as an indicator of seed vigor was studied. Seeds of corn (Zea mays L.), cucumber, (Cucumis sativus L.), onion (Allium cepa L.), and radish (Raphanus sativus L.) with seed moisture contents of 5, 10, 15, 20, or 25% were stored at temperatures of −10°, 5°, 15°, 25°, or 35°C for 0, 2.5, 5, and 10 months. Germination and seedling vigor decreased as storage time, temperature, and moisture level increased. Viability was lost in most seeds after 2.5 months at high temperature (25-35°) and high moisture (20-25%) contents. Seed stored at 5° and 5% moisture maintained the highest viability and seedling vigor over the 10-month storage. Low temperature (−10°) and high seed moisture levels (20-25%) reduced germination and vigor of radish seed. Seed ATP content did not correlate with reduced germination or vigor in any species. ATP concentrations consistently decreased over the 10-month storage period in all seeds stored at −10°. However, this trend did not correlate with the other vigor indices.
New hybrids of sweet corn (Zea mays L.) utilize genes which allow the build-up of high levels of sugar but which also lead to problems with seed and seedling vigor. In this study, ATP and various seedling vigor measurements were compared with seed germination and seedling vigor in normal and 3 corn endosperm mutants harvested at 16 to 42 days post-pollination. Germination and seedling vigor measurements (germination rate, radicle length, fresh and dry weight) showed that a shrunken-2 (sh2) corn was significantly lower in both laboratory and field tests than sugary (su), brittle (bt), and normal. The latter 3 genotypes were nearly equal in seedling vigor. Sugar levels of all mutants and normal were similar at 42 days post-pollination. Total polysaccharides in sh2 were 50% or more below the other 3 genotypes. ATP levels in seeds imbibed 4 hours, were generally similar in sh2 as in the other genotypes. In a time course study of 0 to 96 hr imbibition using 42 day-old seeds, the ATP content of sh2 seeds, was generally as high or higher than in the other 3 genotypes. It did not appear that ATP level was related to poor vigor during the early stages of germination of sh2 corn seeds.