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  • Author or Editor: Rhoda L. Burrows x
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Fungicides applied as soil drenches affect arbuscular-mycorrhizal (AM) fungal colonization of plant roots to different degrees, depending on the chemical used. However, the effect of fungicides applied as seed treatments has been less studied, and is of particular interest to growers who want to encourage beneficial mutualisms while protecting seedlings against pathogens. We tested the effects of four common seed treatments, Apron (mefenoxam), Thiram, Raxil (tebuconzaole), and Captan on colonization of `Superstar' muskmelon roots by the AM fungus Glomus intraradices in the greenhouse. By 30 days after planting, colonization was very high (>90% root length) for all treatments, with relatively minor (<10%) differences in percent length root with AM hyphae. The Apron seed treatment had the highest percent root length with hyphae, but the lowest amount of vesicles, while roots from Raxil and Captan-treated seeds had the lowest hyphal colonization and highest vesicle formation. Myconate ®, a commercial formulation of formononetin, an isoflavone previously shown to increase AM colonization, significantly increased the percent colonization of roots from the Raxil treatment, but not other treatments. Myconate also increased vesicle numbers in all but the Captan treatments, but not significantly.

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Abstract

After the first full growing season, 9- and 11-week-old asparagus (Asparagus officinalis L.) seedlings transplanted in fall exhibited superior crown and fern characteristics relative to seedlings of the same ages transplanted in spring. Seedlings overwintered in coldframes and planted in the spring matched or exceeded growth of those transplanted the previous fall. The hybrid ‘Jersey Giant’ was superior to an improved selection of ‘Mary Washington’ for all planting dates. Correlations between seedling size at transplanting and after one season’s growth were significant for crown weight (r = 0.82), fern weight (r = 0.65), and fern number (r = 0.60). The importance of seedling size is further confirmed by the superior growth of 11-week-old over 9-week-old seedlings up to 18 months after planting.

Open Access

Asparagus offcinalis L. `Mary Washington' seedlings inoculated with Glomus fasciculatum (Thaxter) Gerd. and Trappe emend. Walker and Koske showed increased growth after 9 weeks, compared with noninoculated plants. Phosphorus supplementation (25 g·m-3) increased seedling growth of inoculated and noninoculated plants throughout the 26 weeks of the experiment. However, after 9 weeks, there were no differences in growth of inoculated, non-P-supplemented plants and noninoculated, P-supplemented plants. Fern height, fern and crown weight, and bud numbers correlated positively to the percentage of G. fasciculatum root infection.

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High levels of sphagnum peat in the growing medium promoted growth of asparagus (Asparagus officinalis L. cv. Viking 2K) in a greenhouse study. Application of NH4NO3 > 1 g/pot (84 kg·ha-1 equivalent) was detrimental to root growth. High N rates and high organic matter levels decreased fibrous root development. Shoot dry weight was highly correlated with fleshy root number, root dry weight, and shoot vigor.

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Two year old sugar maples grown in 25 gallon containers were subjected to different levels of stress by withholding water. Drought levels were measured using irrometers. Irrometer readings of 40, 60, and 80 centibars were used to determine when to add water. The media used were a primary nursery mix of 50:50 sand and pine bark by volume. The maples were evaluated for differences in stomatal responsiveness with the porometer and growth parameters of number of nodes, internode length, and leaf number were taken. Some of the trees were treated with ROOTS as a drench to determine if it would enhance resistance to water stress of containerized nursery plants. Despite the use of ROOTS there was no significant difference between the stressed and the non-stressed plants of stomatal responsiveness or the growth parameters.

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Abstract

Three- to 4-month-old seedlings of an improved selection of Asparagus officinalis L. cv. Mary Washington were artificially hardened and crowns subjected to controlled freezing tests. Two low-temperature acclimation regimes were used. The first was 3C for 0, 1, or 2 weeks before freezing at 0, −5, or − 10C; the second, 3C for 0, 1.5, or 3 weeks, followed by freezing at 0, −2.5, −4.5, −6.5, or −8.5C. Regrowth tests showed that hardiness increased with 2 and 3 weeks of acclimation, with tolerance to −5 and −6.5C, respectively. Water-stressed seedlings (relative water content at 57%) withstood exposure to −5C, but not to −6.5C; rehydrated crowns and well-watered controls were hardy to −3.5C.

Open Access