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Rosanna Freyre, Zhanao Deng, and Victor A. Zayas

trials were wild R. simplex , Mayan Purple, Mayan Compact Purple, and the dwarf and fertile ‘Southern Star Blue’ (PanAmerican Seed Co., West Chicago, IL) to have four clones with different plant heights and growth habits. There was not enough plant

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J.W. Scott and B.K. Harbaugh

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S. Hanif-Khan, P.J. Stoffella, J.K. Brecht, H.J. McAuslane, R.C. Bullock, C.A. Powell, and R. Yokomi

External and internal tomato irregular ripening (TIR) symptoms have been associated with the feeding of silverleaf whitefly (SLW), Bemisia argentifolii Bellows and Perring. Soil drench application of gibberellic acid (GA3) (100 ppm, Trial 1 and 2) and cycocel (CCC) (2000 ppm, Trial 1; 1000 ppm, Trial 2) were applied to dwarf cherry tomato (Lycopersicon esculentum) in the presence and absence of SLW to mimic the TIR disorder induced by the SLW. Application of GA3 induced external and internal TIR symptoms similar to the SLW-induced disorder in `Florida Petite'. There were essentially no TIR symptoms in fruit treated with CCC, an inhibitor of GA biosynthesis. In Trial 1, internal white tissue in GA3, SLW, and CCC treatments was expressed in 97%, 95%, and 4% of the total fruit, respectively. Incidence of external TIR symptom was highest (56%) in the GA3 plus SLW treatment. In Trial 2, GA3 application in the presence (83%) or absence (85%) of SLW resulted in the highest incidence of fruit with internal white tissue. External TIR symptoms induced by GA3 in the presence and absence of SLW were reduced with CCC application. These results suggest that the TIR disorder in tomato is induced by the SLW may be a GA3-regulated disorder.

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Matthew D. Whiting and Gregory A. Lang

Canopy fruit to leaf area ratios (fruit no./m2 leaf area, F:LA) of 7- and 8-year-old `Bing' sweet cherry (Prunus avium L.) on the dwarfing rootstock `Gisela 5' (P. cerasus L. × P. canescens L.) were manipulated by thinning dormant fruit buds. F:LA influenced yield, fruit quality, and vegetative growth, but there were no consistent effects on whole canopy net CO2 exchange rate (NCERcanopy). Trees thinned to 20 fruit/m2 LA had yield reduced by 68% but had increased fruit weight (+25%), firmness (+25%), soluble solids (+20%), and fruit diameter (+14%), compared to unthinned trees (84 fruit/m2). Fruit quality declined when canopy LA was ≈200 cm2/fruit, suggesting that photoassimilate capacity becomes limiting to fruit growth below this ratio. NCERcanopy and net assimilation varied seasonally, being highest during stage III of fruit development (64 days after full bloom, DAFB), and falling more than 50% by 90 DAFB. Final shoot length, LA/spur, and trunk expansion were related negatively to F:LA. F:LA did not affect subsequent floral bud induction per se, but the number of flowers initiated per bud was negatively and linearly related to F:LA. Although all trees were thinned to equal floral bud levels per spur for the year following initial treatment (2001), fruit yields were highest on the trees that previously had no fruit, reflecting the increased number of flowers initiated per floral bud. Nonfruiting trees exhibited a sigmoidal pattern of shoot growth and trunk expansion, whereas fruiting trees exhibited a double sigmoidal pattern due to a growth lag during Stage III of fruit development. Vegetative growth in the second year was not related to current or previous season F:LA. We estimate that the LA on a typical spur is only sufficient to support the full growth potential of a single fruit; more heavily-set spurs require supplemental LA from nonfruiting shoots. From these studies there appears to be a hierarchy of developmental sensitivity to high F:LA for above-ground organs in `Bing'/`Gisela 5' sweet cherry trees: trunk expansion > fruit soluble solids (Stage III) > fruit growth (Stage III) > LA/spur > shoot elongation > fruit growth (Stages I and II) > LA/shoot. Current season F:LA had a greater influence on fruit quality than prior cropping history, underscoring the importance of imposing annual strategies to balance fruit number with LA.

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Kim D. Bowman

`Cipo' sweet orange [Citrus sinensis (L.) Osbeck] combines typical midseason fruit characteristics with a unique procumbent growth habit. This distinctive habit may be of value in breeding smaller and more procumbent scion cultivars if the growth habit is transmitted to hybrid seedlings. Two hybrid populations were created using `Clementine' mandarin (Citrus reticulata Blanco) as the female parent and either `Cipo' sweet orange or `Pineapple' (another midseason sweet orange with a more typical upright growth habit) as the male parent. The `Clementine' × `Cipo' cross yielded many hybrids with the procumbent habit, many with the upright habit, and some that appeared intermediate. Both hybrid populations were compared with nucellar seedling populations from `Cipo' and `Pineapple' using two morphological characteristics that differentiate between the procumbent habit of `Cipo' and the upright habit of `Pineapple'. All the `Clementine' × `Pineapple' hybrids were of upright growth habit, while the `Clementine' × `Cipo' progeny segregated into two groups based on growth habit (upright and procumbent). The two measured characteristics were tightly correlated in the segregating population and are probably pleiotropic effects of the same genetic mutation. The observed population distributions were as expected if the procumbent habit in `Cipo' is controlled by a single dominant allele in the heterozygous condition.

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R. Scorza, T.W. Zimmerman, J.M. Cordts, K.J. Footen, and M. Ravelonandro

`Wisconsin 38' tobacco (Nicotiana tabacum L.) leaf discs were transformed with the disarmed Agrobacterium tumefaciens strain EHA101 carrying the rolC gene from A. rhizogenes (Oono et al., 1987) and NPT II and GUS genes. Shoots that regenerated on kanamycin-containing medium were confirmed as transgenic through GUS assays, polymerase chain reaction (PCR), Southern blot analyses, and transmission of the foreign genes through the sexual cycle. Transgenic plants were as short as half the height of control plants; were earlier flowering by up to 35 days; and had smaller leaves, shorter internodes, smaller seed capsules, fewer seeds, smaller flowers, and reduced pollen viability. The number of seed capsules, leaf number, and specific root length were similar between transgenic and control plants. Transgenic clones varied in the expression of the rolC-induced growth alterations as did the first generation of seedlings from these clones. Such differences suggested the potential for selecting for different levels of expression. Transformation with the rolC gene presents a potentially useful method of genetically modifying horticultural crops, particularly for flowering date, height, and leaf and flower size. Chemical names used: neomycin phosphotransferase (NPTII), β-glucuronidase (GUS).

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Walter E. Splittstoesser, Ellen B. Rest, and Cleora J. D'Arcy

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James N. Moore, Roy C. Rom, Stanley A. Brown, and Gerald L. Klingaman

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A.S. Devyatov

Growth and fruiting of apple trees in twin-row tree-belts were studied during 5 years after planting the orchard. Distance between belts was 4 m, between rows in a belt was 1 m, between trees in row 3 or 1.5 m, giving tree densities of 1335 or 2670 trees/ha, respectively. Control was a single-row planting 4 × 3 or 4 × 1.5 m, producing densities of 833 or 1665 trees/ha. Trees were trained as hedgerow in treatments with a density of 1335 or 833 trees/ha. Each tree in a twin-row belt had a separate crown with narrow passage between trees. This passage was cut through every year. Fruiting of `Tellisaare' began at 2nd leaf, `Antey' at 3rd, and `Spartan' at 4th leaf after planting. Total yield for 3 years in the highest density treatment of single-row planting of `Antey' and `Tellisaare' was >50 t·ha–1 and in twin-row orchard construction from 36 to 57 t·ha–1, depending on orchard density. The two-fold increase in orchard density from 1335 to 2700 trees/ha raised yield of `Antey' by 58% and `Tellisaare' by 33%. Single-row treatment with a tree density of 1665/ha averaged 17.1–17.5 t·ha–1 without great expenditure on pruning of trees. The fruit quality was very high in all treatments.

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Brent K. Harbaugh and John W. Scott