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  • Author or Editor: F. J. Peterson x
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Sweetpotato resin glycosides were purified by HPLC methods. Most allelopathic potential could be explained by these compounds. Fifty percent inhibition (I50) of seed germination was obtained for redroot pigweed at 160 ppm, for velvetleaf at 13 ppm and for prosomillet at 11 ppm. Seed of the congeneric species I. purpurea was not sensitive. Growth of yellow nutsedge was drastically reduced, the I50 for shoot growth was 30 ppm, for number of roots 36 ppm, and for total root length 19 ppm. The glycosides accounted for approximately half of the total fungicidal activity of all extract fractions when tested on Fusarium oxysporum pv. batatae. At 2 mg per ml, the glycosides inhibited hyphal growth by 31%. This concentration is less than 10% of the glycoside concentration in dry periderm tissue of `Regal'. The purified glycosides were incorporated into a meridic diet for diamondback moth larvae. All observed antibiosis was caused by the glycosides; the LD50 was 7.2 mg per ml diet. At that concentration the surviving larvae showed a weight decrease of 46%.

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Callus tissue grown from `Marsh' grapefruit (Citrus paradisi Macf.) albedo tissue was grown at 30C for ≈ 40 days. Calli were preconditioned in normal air for 5 days at 10 or 30C before being fumigated for 2 hr with 0, 32, or 48 g of methyl bromide (MB)/m 3. Calli were then held at 10C and K+ leakage was measured after 1, 10, 20, and 30 days. The amount of K+ leaked from MB-fumigated calli was greater than that for nonfumigated calli and increased with higher MB dose. Leakage also increased with time following fumigation. Leakage of calli preconditioned at 30C and fumigated with 48 g MB/m3 was 140%, 196%, and 260% greater than leakage from nonfumigated calli 10, 20, and 30 days after fumigation, respectively. Leakage from calli preconditioned at 10C for 5 days before MB fumigation was less than that from calli held at 30C. MB doses of 32 and 48 g·m-3 increased leakage of calli preconditioned at 10C by 6% and 43% and for those preconditioned at 30C by 99% and 140%, respectively, 10 days after fumigation. In addition to K+ leakage, MB induced the development of a tan to orangish-brown discoloration.

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These studies were initiated to investigate severe growth inhibition observed when some vegetable crops were infested with corn spurry (Spergula arvensis L.). Interference by a natural population of the weed reduced the shoot weights of English pea (Pisum sativum L.) and collard (Brassica oleracea L.) by 93% and 72%, respectively. In a greenhouse experiment where light competition by corn spurry was prevented, broccoli (Brassica oleracea L.) shoot weights were reduced by corn spurry, but pea weights were not different from the controls. Homogenized corn spurry shoot tissue incorporated into a greenhouse potting medium inhibited the growth of both species, and a concentration effect was observed. Sequential hexane, dichloromethane, methanol, and 50% aqueous methanol extracts of corn spurry root and shoot tissue were tested for inhibitory activity using millet seed germination and broccoli seedling growth bioassays. Dichloromethane, methanol, and aqueous methanol shoot extracts were inhibitory to broccoli; whereas all shoot extracts inhibited millet germination. Shoot extracts were more inhibitory than root extracts. Further fractionation of the inhibitors using a combination of reversed-phase sephadex LH-20 and silicic acid column chromatographic procedures showed that a major portion of the millet germination inhibition was due to sucrose esters (SE). Preliminary characterization of the esters showed that there were four different SE groups. The major groups contained either octanoic or dodecanoic acid along with butanoic and petanoic acids. All groups inhibited seed germination at concentrations as low as 20 ppm. This is the first report of the SE class of defense chemicals in plant species outside of the solanaceae family.

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Two biosolid-containing waste media [sewage sludge compost and incinerated biosolids (flume sand)] were tested individually, together, and in combination with a commercial growing medium for growing wildflower sod in greenhouse trials over a 3-year period. A medium composed of flume sand and Metromix (7:3 weight/weight) in 7.5 {XtimesX} 10.5 {XtimesX} 2-inch deep (19 {XtimesX} 27 {XtimesX} 5-cm) plastic trays seeded at 20 oz/1000ft2 (6.1 g·m-2) with cosmos (Cosmos bipinnatus), cornflower (Centaurea cyannis), plains coreopsis (Coreopsis tinctoria), white yarrow (Achillea millefolium) and purple coneflower (Echinacea purpurea) produced a suitable wildflower sod in 10 to 12 weeks. A single application of slow release fertilizer (Osmocote 14-14-14, 14N-4.2P-11.6K) applied as a top dressing had no significant effect on sod development; however, a 4-mil [0.004-inch (0.10-mm)] polyethylene barrier placed in the base of each container resulted in increased dry weight accumulation and a higher root to shoot ratio relative to sod grown without plastic.

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Abstract

‘La Festival’ peach [Prunus persica (L.) Batsch] was released to provide a yellow flesh cultivar with a good quality fruit requiring 400 to 500 hr chilling. ‘La Festival’ produces a heavy crop of medium to large freestone fruit that ripen about 25 June, or about 20 days before ‘Elberta’ in southern Louisinna

Open Access

Abstract

‘La Pecher’ peach [Prunus persica (L.) Batsch] was released to provide a good quality yellow flesh cultivar with a 400 to 500 hr chilling requirement. ‘La Pecher’ produces a heavy crop of medium to large semifreestone fruit that ripen 39 days before ‘Elberta’ or about 6 June in southern Louisiana.

Open Access

Abstract

‘La White’ peach [Prunus persica (L.) Batsch] was released to provide a 600-700 hr chilling requirement, low acid, white flesh cultivar adapted to conditions in southeastern Louisiana. ‘La White’ produces a heavy crop of medium to large semi-freestone fruit that ripen 27 days before ‘Elberta’ or about 18 June in southeastern Louisiana.

Open Access