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Marco Volterrani, Simone Magni, Monica Gaetani, and Filippo Lulli

treatments resulted in a significant aerial biomass growth enhancement that reached the average value of 95.7 mg/plant with no statistical difference among the three application rates. Daughter plants originating from nodes excised at 8 WAT did not show

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Abu Shamim Mohammad Nahiyan and Yoh-ichi Matsubara

-AMF and AMF plants ( t test, P ≤ 0.05); ns = nonsignificant. Discussion In this study, dry weight of ferns and roots increased in all the AMF plants compared with non-AMF before and after Foa inoculation, which indicates the growth enhancement through

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Jinmin Fu, Jack Fry, and Bingru Huang

reduction in shoot growth may have contributed to root growth enhancement of tall fescue irrigated at 20% ET. A drier soil at the 0- to 25-cm depth at 20% ET irrigation in this field study also enhanced root numbers at a 36.3-cm depth, which is congruent

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F.T. Davies Jr., V. Olalde-Portueal, H. M. Escamilla, R.C. Ferrera, and M.J. Alvarado

In a 3 × 3 factorial experiment, Chile Ancho pepper (Capsicum annuum L. cv. San Luis) plants were inoculated or not with VA - mycorrhizal (VAM) Glomus fasciculatum and a Glomus sps isolate from Mexico (ZAC-19). Long Ashton Nutrient solution (LANS) were modified to supply P at II, 22 or 44 μg/ml to containerized plants, grown in a greenhouse for 72 days. The container medium was a modified 77% sand, 13% silt, 9% clay soil collected from an agricultural production site in Irapuato, Guanajuato, Mexico. Both P and VAM enhanced plant growth and development. Increasing P enhanced leaf area, fruit, shoot and root dry weight and shoot/root ratio; the leaf area ratio (LAR) decreased. Greater VAM growth enhancement occurred at Il and 22, than 44 μg/ml P. Growth enhancement was greater with Glomus fasciculatum than the mixed Glomus sps isolate (ZAC - 19).

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GyeSoon Jeong, John M. Brown, and Byoung Ryong Jeong

Trichoderm a spp. are currently being investigated for biological control of soil-borne pathogens and their potential to enhance plant growth and development. The influence of T. harzianum and T. hamatum on growth of 7 bedding plant species was Investigated. Trichoderm a formulated in peat moss and wheat bran, was mixed into germination and growing media at 1 × 106 cfu per gram of medium. Seeds were germinated in plugs and later grown in cellpacks containing a treated and non-treated medium until market stage. Plants were evaluated by measuring height, fresh and dry weight, and number and timing of flowering. Growth enhancement was found in marigold (14.8% dw), petunia (15.5% dw) and tomato (38.2% dw), however, no significant differences were seen in celosia, impatiens, salvi a and vinca. Results suggest that growth enhancement by Trichoderm a is species dependent and that Trichoderm a applied in the plug mix remains-effective through marketing stage.

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Amelia Camprubí and Cinta Calvet

The selection of the most effective arbuscular mycorrhizal (AM) fungi for growth enhancement of citrus cultivars used as rootstocks was the first step toward development of an AM inoculation system in citrus nurseries in Spain. AM fungi were isolated from citrus nurseries and orchards in the major citrus-growing areas of eastern Spain. The most common AM fungi found in citrus soils belonged to Glomus species, and G. mosseae (Nicol. & Gerd.) Gerdemann & Trappe and G. intraradices Schenck & Smith were the AM fungi most frequently associated with citrus roots. The most effective fungus for growth enhancement of citrus rootstocks was G. intraradices. Significant differences in mycorrhizal dependency among rootstocks were confirmed. Sour orange (Citrus aurantium L.) and Cleopatra mandarin (C. reshni L.) were more dependent than Troyer citrange [C. sinensis (L.) Obs. × Poncirus trifoliata (L.) Raf.] and Swingle citrumelo (C. paradisi Macf. × P. trifoliata). Moreover, several inoculation systems for plant production were evaluated for their effectiveness in promoting root colonization of the rootstock cultivars.

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James H. Keithly, Daniel P. Jones, and Henry Yokoyama

The growth-enhancing property of DCPTA was tested on transplanted seedlings of Brassolaeliocattleya × Hort. (Blc. Bryce Canyon × Lc. Pirate King), Dendrobium × Blume. Hickham Deb, Epidendrum radicans Pav. ex Lindl., Lueliocattleya × Rolfe Prism Palette `The Clown', and Phalaenopsis × Blume. [Pink Zebra × (Jutta Brungor × Music)]. After 3 to 6 months of greenhouse growth, plants treated with 30 μm DCPTA produced a 2- to 3-fold increase in root growth compared to the controls. Shoot growth, root: shoot ratio, and the survival of DCPTA-treated plants were increased significantly when compared with controls. Chemical name used: 2-(3,4-dichlorophenoxy)triethylamine (DCPTA).

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R.G. Linderman and E.A. Davis

Coconut fiber dust (coir) is being used as a peat substitute or amendment to potting mixes with varied results. However, its microbial composition and compatibility with beneficial microbes that might be added to growth media in the nursery, such as mycorrhizal fungi, has not been determined. In this study, coir was amended to a peat-based medium (15%, 30%, 45%, and 60% by volume) to determine its effects on growth of several ornamental plants and on the formation and function of the arbuscular mycorrhizal (AM) fungus Glomus intraradices. Mycorrhizae formed as well, and usually better, in all the coir-amended peat treatments as in peat alone. The magnitude of growth enhancement due to mycorrhizae was small for the plants tested in these media compared to that which usually occurs in soil-based media. In this experiment, plant growth responses appeared to be independent of level of mycorrhizal colonization and were plant species dependent. Consistent growth enhancement from mycorrhizae only occurred with marigold (Tagetes patula). With germander (Teucrium fruticans), growth was depressed with mycorrhizal inoculation in the medium composed of 60% coir. Growth of lavender (Lavandula augustifolia) was depressed in all coir-amended media, with or without AM inoculation, compared to the nonamended control. These results confirm previous reports of varied response of plant species to coir, and indicate the lack of any detrimental effects of coir on mycorrhiza formation.

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R.G. Linderman and E.A. Davis

Composted materials with high humic and microbial content, and their water extracts, are increasingly used in the nursery industry as potting mix components or as liquid amendments for the purposes of enhancing plant growth. Common speculation is that such materials either contain beneficial microbes or stimulate those in or added to the medium, such as vesicular-arbuscular mycorrhizal (VAM) fungi, known to have growth-stimulating effects on plants. Experiments were conducted to determine if one such compost enhanced plant growth by stimulating VAM fungi or other growth-enhancing microbes, by simply providing limiting nutrients [phosphorus (P)], or a combination of the two. Highly mycorrhiza-responsive onion (Allium cepa) `White Lisbon' was used to evaluate the interactions of composted grape pomace (CGP), the VAM fungus Glomus intraradices, and preplant soil heat treatment on onion growth under P-limiting conditions. CGP and its water extract stimulated onion growth under P-limiting conditions in the absence of VAM; the extract was more effective than the granular CGP. Growth was enhanced further by addition of G. intraradices, and the extract enhanced its colonization of roots. Heat pretreatment of the soil inconsistently affected growth-enhancement by CGP or its extract. Thus, inoculating plant roots with mycorrhizal fungi in combination with this composted organic amendment or its extract was beneficial. The effect could have been due to the CGP providing a source of P to overcome the P-limiting conditions, and to the mycorrhizal fungus enhancing P uptake by its extraradical hyphae and thereby increasing nutrient-use efficiency.

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Guglielmo Costa, Carlo Andreotti, Fabrizio Bucchi, Emidio Sabatini, Carlo Bazzi, Sabrina Malaguti, and Wilhelm Rademacher

Prohexadione-Ca (Apogee®) was tested as a growth retardant and fire-blight control agent in the pear (Pyrus communis L. cv. Abbé Fétel) on both bearing trees in the orchard and on 1-year-old scions under greenhouse conditions. Four sprays of 50 and 100 mg·L-1 of the chemical were applied to trees in the orchard at 2-week intervals starting at petal fall, when terminal growth was 4 cm (mid-April). Scions received a single application (250 mg·L-1) and were transferred 2 weeks later to a greenhouse where the shoots were inoculated with a local, virulent strain of Erwinia amylovora (Burrill) Winslow et al. In the orchard, the higher prohexadione-Ca concentration was more effective in reducing shoot growth, enhancing fruit weight and controlling fire blight incidence and severity. Similar effects on growth parameters and disease progression were observed under greenhouse conditions. Chemical name used: calcium 3-oxido-4-propionyl-5-oxo-3-cyclohexene carboxylate (prohexadione-Ca)