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John L. Maas and M.J. Line

We report the use of nuclear magnetic resonance (NMR) imaging to detect differences in invasion and colonization of fruit by pathogens (Botrytis cinerea, Colletotrichum acutatum, and Phytophthora cactorum), and bruise wounds are sharply distinguishable from healthy fruit tissue by their T1 times. Digitized images from T1 images clearly show two or more zones of pathogen activity in fruit tissue. The innermost zone corresponds to the area of greatest invasive activity at the leading margin of the infection. A second zone corresponds to the area of tissue that has been killed and is being degraded by the pathogen. Sometimes, a third zone is present at the outer border of the lesion and this correspond to where aerial sporulation may occur. Images of bruises, however, are uniform with no apparent gradations in T1 characteristics. Detection of fruit deterioration and decay is important in understanding and controlling postharvest loss of fruit crops. The nondestructive nature of MRI provides a means to quantify the process of decay development and control measures applied to fruits.

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Monte L. Nesbitt, J. Benton Storey, D. Lyda, and L.J. Grauke

Rootstock resistance to soil-borne phytopathogenic fungi, such as Phymatotrichum omnivorum (Shear) Duggar, is an important factor in disease control. Measurement of natural rootstock resistance is often based on plant survival/mortality percentage, and /or growth data. Fungal colonization of host roots in disease screening experiments may not be uniform for many reasons, causing variability in host response. Quantification of fungal colonization is needed in order to better understand rootstock performance. Ergosterol, a structural sterol in cell membranes of fungi, is not found in higher plants, and can thus be a measure of fungal colonization. Ergosterol was extracted from roots of pecan seedlings artificially inoculated with P. omnivorum and grown in an environmental growth chamber. Analysis of extracts with HPLC revealed that seedlings which were killed in screening, or had low root performance ratings, had increased levels of ergosterol. Non-inoculated controls also contained Ergosterol. indicating contamination and possible competition by other fungi.

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Antonieta N. Salomão, Marta G.R. Faiad, and Rozane Cunha

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Y.L. Qian and M.C. Engelke

Determining the appropriate level of irrigation for turfgrasses is vital to the health of the turfgrass and the conservation of water. The linear gradient irrigation system (LGIS) allows long-term assessment of turf performance under continuous irrigation gradients from excess to no irrigation. The objectives of this study were to: 1) evaluate the minimum irrigation requirements and relative drought resistance of `Rebel II' tall fescue (Festuca arundinacea Schreb.), `Meyer' zoysiagrass (Zoysia japonica Steud.), `Tifway' bermudagrass [Cynodon dactylon (L.) Pers.], `Prairie' buffalograss [Buchloe dactyloides (Nutt.) Engelm], and `Nortam' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze]; and 2) evaluate the long-term effects of irrigation levels on turf persistence, weed invasion, and disease incidence for the five selected turfgrasses under field conditions. Turf was sodded under LGIS with an irrigation gradient ranging from 120% Class A pan evaporation (Ep) to natural precipitation, along a 20-m turf area. Evaluation during the summers of 1993–96 indicated that grasses differed in drought resistance and persistence under variable irrigation regimes. Irrigation (Ep) required to maintain acceptable turf quality for respective grasses was `Rebel II' (67%), `Meyer' (68%), `Nortam' (44%), `Tifway' (35%), and `Prairie' (26%). Higher dollar spot (Sclerotinia homoeocarpa Bennett) infection was observed at 115% Ep irrigation regime in `Tifway' bermudagrass, whereas gray leaf spot [Pyricularia grisea (Hebert) Barr] was observed only at 10% Ep irrigation regime in St. Augustinegrass plots. An outbreak of brown patch (Rhizoctonia solani Kuehn.) occurred in Sept. 1996 in St. Augustinegrass plots receiving irrigation at >80% Ep.

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Jun Tang, Kang-Di Hu, Lan-Ying Hu, Yan-Hong Li, Yong-Sheng Liu, and Hua Zhang

concentrations of 0, 0.5, 1.0, 1.5, 2.0, and 2.5 mmol·L −1 were placed in the bottom of the sealed containers at 20 °C with a relative humidity of 90% to 95% to fumigate fungi for the time indicated in the figure legends. For fungal infection of sweetpotato

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Marija Perić, Slavica Dmitrović, Suzana Živković, Biljana Filipović, Marijana Skorić, Ana Simonović, and Slađana Todorović

Protection Legislation ( Diklić et al., 1999 ). Propagation of R. umbellata in nature is limited by fungal infections and insufficient seed maturity ( Ljaljević Grbić et al., 2005 ). A literature search revealed no publications dedicated to this rare

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Judith Pozo, Miguel Urrestarazu, Isidro Morales, Jessica Sánchez, Milagrosa Santos, Fernando Dianez, and Juan E. Álvaro

%, and 55% in the stems of pepper, melon, and tomato plants, respectively. Table 7. Cuticle thickness (µm) in stem and leaves for the plants with (+Si) and without (−Si) silicon (Si) in the nutrient solution. Resistance to fungal infection. The area

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Michele R. Warmund and Jeanne D. Mihail

development occurs at the distal end of a current season’s growth of American elderberry canes and in the same region of older canes of European cultivars, floral meristems were likely injured by fungal infection after inoculation, resulting in the absence of

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Carlos A. Parera and Daniel J. Cantliffe

Generally, sweet corn cultivars (Zea mays L.) carrying the shrunken-2 (sh2) gene have lower germination and seedling vigor than normal or sugary (su) cultivars. Seeds of sh2 `How Sweet It Is' (HSII) and `Crisp N'Sweet 711' (CNS-711) were imbibed for 6 hours. Rapid water uptake, higher seed leakage, and fungal infection were found in HSII, the lower germinating cultivar. Imbibition rate and leakage conductivity were reduced in both cultivars during the first 5 hours at 5C as compared with 25C. Sodium hypochlorite was an effective seed disinfectant. When the seeds were primed with sodium hypochlorite via solid matrix priming (SMP), germination under stressful conditions (soilcold test) was significantly improved in both cultivars. Primed seeds had significantly lower imbibitional rates and leakage conductivity than nonprimed seeds. The superior germination measured in primed and disinfected seeds was possibly due to the lower imbibitional rate and reduced seed fungal infection.

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Rod Jones and John Faragher

Five members of the Proteaceae and 13 Australian native cut flower cultivars were stored for 35 days under standard conditions at 1C to assess their ability to withstand long-term storage and transport. Protea cynaroides L., Leucadendron `Silvan Red', Leucospermum `Firewheel', Thryptomene calycina (Lindl.) Stapf., Telopea speciosissima R. Br., and Verticordia grandtiflora Endl. retained a vase life of at least 7 days after 21 days of storage. Leucospermum cordifolium Salisb. ex Knight, Protea neriifoli R. Br., Chamelaucium uncinatum `Alba', C. uncinatum `Purple Pride', Verticordia monadelpha Turcz., Verticordia plumosa (Desf.) Druce, and Verticordia nitens (Lindl.) Schau. suffered a decline in vase life ranging from 31% to 100% after 14 to 21 days of storage. Species of Verticordia and Chamelaucium were particularly susceptible to fungal infection. Anigozanthos pulcherrimus Hook. and the Anigozanthos cultivars Ruby Delight, Bush Harmony, Bush Haze, and Gold Fever all showed a significant reduction in vase life after 14 days of storage compared with unstored controls.